Difference between revisions of "Testing for Weak SSL/TSL Ciphers, Insufficient Transport Layer Protection (OWASP-EN-002)"

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== Brief Summary ==
 
== Brief Summary ==
<br>
+
 
Due to the historical exporting restrictions of high grade cryptography, both legacy and new web servers could be able to handle a weak cipher suite.<br>
+
Sensitive data must be protected when it is transmitted through the network. Such data can include user credentials and credit cards. As a rule of thumb, if data must be protected when it is stored, it must be protected also during transmission.
Even if high grade ciphers are today supported and normally used, some misconfiguration in server installation could be used to force the use of a weak cipher (or at worst no encryption) permitting to an attacker to gain access to the supposed secure communication channel.<br>
+
 
<br>
+
 
 +
HTTP is a clear-text protocol and it is normally secured via an SSL/TLS tunnel, resulting in HTTPS traffic [1]. The use of this protocol ensures not only confidentiality, but also authentication. Servers are authenticated using digital certificates and it is also possible to use client certificate for mutual authentication.
 +
 
 +
 
 +
Even if high grade ciphers are today supported and normally used, some misconfiguration in the server can be used to force the use of a weak cipher - or at worst no encryption - permitting to an attacker to gain access to the supposed secure communication channel. Other misconfiguration can be used for a Denial of Service attack.
 +
 
 +
 
 
== Description of the Issue ==  
 
== Description of the Issue ==  
<br>
+
A vulnerability occurs if the HTTP protocol is used to transmit sensitive information [2] (e.g. credentials transmitted over HTTP [3]).
The HTTP clear-text protocol is normally secured via an SSL or TLS tunnel, resulting in HTTPS traffic. In addition to providing encryption of data in transit, HTTPS allows the identification of servers (and, optionally, of clients) by means of digital certificates.
+
 
 +
When the SSL/TLS service is present it is good but it increments the attack surface and the following vulnerabilities exist:
 +
* SSL/TLS protocols, ciphers, keys and renegotiation must be properly configured.
 +
* Certificate validity must be ensured.
 +
 
 +
Other vulnerabilities linked to this are:
 +
* Software exposed must be updated due to possibility of known vulnerabilities [4].
 +
* Usage of Secure flag for Session Cookies [5].
 +
* Usage of HTTP Strict Transport Security (HSTS) [6].
 +
* The presence of HTTP and HTTPS both, which can be used to intercept traffic [7], [8].
 +
* The presence of mixed HTTPS and HTTP content in the same page, which can be used to Leak information.
 +
 
 +
 
 +
===Sensitive data transmitted in clear-text===
 +
The application should not transmit sensitive information via unencrypted channels. Typically it is possible to find basic authentication over HTTP, input password or session cookie sent via HTTP and, in general, other information considered by regulations, laws or organization policy.
 +
 
 +
 
 +
===Weak SSL/TLS Ciphers/Protocols/Keys===
 +
Historically, there have been limitations set in place by the U.S. government to allow cryptosystems to be exported only for key sizes of at most 40 bits, a key length which could be broken and would allow the decryption of communications. Since then cryptographic export regulations have been relaxed the maximum key size is 128 bits.
 +
 
 +
 
 +
It is important to check the SSL configuration being used to avoid putting in place cryptographic support which could be easily defeated. To reach this goal SSL-based services should not offer the possibility to choose weak cipher suite. A cipher suite is specified by an encryption protocol (e.g. DES, RC4, AES), the encryption key length (e.g. 40, 56, or 128 bits), and a hash algorithm (e.g. SHA, MD5) used for integrity checking.
 +
 
 +
 
 +
Briefly, the key points for the cipher suite determination are the following:
 +
# The client sends to the server a ClientHello message specifying, among other information, the protocol and the cipher suites that it is able to handle. Note that a client is usually a web browser (most popular SSL client nowadays), but not necessarily, since it can be any SSL-enabled application; the same holds for the server, which needs not to be a web server, though this is the most common case [9].
 +
#The server responds with a ServerHello message, containing the chosen protocol and cipher suite that will be used for that session (in general the server selects the strongest protocol and cipher suite supported by both the client and server).
 +
 
 +
 
 +
It is possible (for example, by means of configuration directives) to specify which cipher suites the server will honor. In this way you may control whether or not conversations with clients will support 40-bit encryption only.
 +
 
 +
#The server sends its Certificate message and, if client authentication is required, also sends a CertificateRequest message to the client.
 +
#The server sends a ServerHelloDone message and waits for a client response.
 +
#Upon receipt of the ServerHelloDone message, the client verifies the validity of the server's digital certificate.
 +
 
  
===Weak SSL/TSL Ciphers===
 
<br>
 
Historically, there have been limitations set in place by the U.S. government to allow cryptosystems to be exported only for key sizes of at most 40 bits, a key length which could be broken and would allow the decryption of communications. Since then cryptographic export regulations have been relaxed (though some constraints still hold), however it is important to check the SSL configuration being used to avoid putting in place cryptographic support which could be easily defeated. To reach this goal SSL-based services should not offer the possibility to choose weak cipher suite. A cipher suite is specified by an encryption protocol (DES, RC4, AES), the encryption key length (such as 40, 56, or 128 bits), and a hash algorithm (SHA, MD5) used for integrity checking.<br>
 
Briefly, the key points for the cipher suite determination are the following: <br>
 
# The client sends to the server a ClientHello message specifying, among other information, the protocol and the cipher suites that it is able to handle. Note that a client is usually a web browser (most popular SSL client nowadays), but not necessarily, since it can be any SSL-enabled application; the same holds for the server, which needs not to be a web server, though this is the most common case. (For example, a noteworthy class of SSL clients is that of SSL proxies such as stunnel (www.stunnel.org) which can be used to allow non-SSL enabled tools to talk to SSL services);<br>
 
# The server responds with a ServerHello message, containing the chosen protocol and cipher suite that will be used for that session (in general the server selects the strongest protocol and cipher suite supported by both the client and server). <br>
 
It is possible (for example, by means of configuration directives) to specify which cipher suites the server will honor. In this way you may control, for example, whether or not conversations with clients will support 40-bit encryption only.<br>
 
 
===SSL certificate validity – client and server===
 
===SSL certificate validity – client and server===
When accessing a web application via the HTTPS protocol, a secure channel is established between the client and the server. The identity of one (the server) or both parties (client and server) is then established by means of digital certificates. So, once the cipher suite is determined, the “SSL Handshake” continues with the exchange of the certificates, like follow:<br>
+
 
<ol>
+
When accessing a web application via the HTTPS protocol, a secure channel is established between the client and the server. The identity of one (the server) or both parties (client and server) is then established by means of digital certificates. So, once the cipher suite is determined, the “SSL Handshake” continues with the exchange of the certificates:
<li value=3> The server sends its Certificate message and, if client authentication is required, also sends a CertificateRequest message to the client.  
+
# The server sends its Certificate message and, if client authentication is required, also sends a CertificateRequest message to the client.
<li> The server sends a ServerHelloDone message and waits for a client response.
+
# The server sends a ServerHelloDone message and waits for a client response.
<li> Upon receipt of the ServerHelloDone message, the client verifies the validity of the server's digital certificate.
+
# Upon receipt of the ServerHelloDone message, the client verifies the validity of the server's digital certificate.
</ol>
+
 
In order for the communication to be set up, a number of checks on the certificates must be passed. While discussing SSL and certificate based authentication is beyond the scope of this Guide, we will focus on the main criteria involved in ascertaining certificate validity: <br>
+
 
a) checking if the Certificate Authority (CA) is a known one (meaning one considered trusted);<br>
+
In order for the communication to be set up, a number of checks on the certificates must be passed. While discussing SSL and certificate based authentication is beyond the scope of this guide, this section will focus on the main criteria involved in ascertaining certificate validity:  
b) checking that the certificate is currently valid;<br>
+
 
c) checking that the name of the site and the name reported in the certificate match.<br>
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* Checking if the Certificate Authority (CA) is a known one (meaning one considered trusted);
Let’s examine each check more in detail. <br>
+
* Checking that the certificate is currently valid;
a) Each browser comes with a preloaded list of trusted CAs, against which the certificate signing CA is compared (this list can be customized and expanded at will). During the initial negotiations with an HTTPS server, if the server certificate relates to a CA unknown to the browser, a warning is usually raised. This happens most often because a web application relies on a certificate signed by a self-established CA. Whether this is to be considered a concern depends on several factors. For example, this may be fine for an Intranet environment (think of corporate web email being provided via HTTPS; here, obviously all users recognize the internal CA as a trusted CA). When a service is provided to the general public via the Internet, however (i.e. when it is important to positively verify the identity of the server we are talking to), it is usually imperative to rely on a trusted CA, one which is recognized by all the user base (and here we stop with our considerations; we won’t delve deeper in the implications of the trust model being used by digital certificates). <br>
+
* Checking that the name of the site and the name reported in the certificate match.
b) Certificates have an associated period of validity, therefore they may expire. Again, we are warned by the browser about this. A public service needs a temporally valid certificate; otherwise, it means we are talking with a server whose certificate was issued by someone we trust, but has expired without being renewed. <br>
+
 
c) What if the name on the certificate and the name of the server do not match? If this happens, it might sound suspicious. For a number of reasons, this is not so rare to see. A system may host a number of name-based virtual hosts, which share the same IP address and are identified by means of the HTTP 1.1 Host: header information. In this case, since the SSL handshake checks the server certificate before the HTTP request is processed, it is not possible to assign different certificates to each virtual server. Therefore, if the name of the site and the name reported in the certificate do not match, we have a condition which is typically signaled by the browser. To avoid this, IP-based virtual servers must be used. [2] and [3] describe techniques to deal with this problem and allow name-based virtual hosts to be correctly referenced. <br>
+
 
 +
Let's examine each check more in detail.  
 +
 
 +
* Each browser comes with a pre-loaded list of trusted CAs, against which the certificate signing CA is compared (this list can be customized and expanded at will). During the initial negotiations with an HTTPS server, if the server certificate relates to a CA unknown to the browser, a warning is usually raised. This happens most often because a web application relies on a certificate signed by a self-established CA. Whether this is to be considered a concern depends on several factors. For example, this may be fine for an Intranet environment (think of corporate web email being provided via HTTPS; here, obviously all users recognize the internal CA as a trusted CA). When a service is provided to the general public via the Internet, however (i.e. when it is important to positively verify the identity of the server we are talking to), it is usually imperative to rely on a trusted CA, one which is recognized by all the user base (and here we stop with our considerations; we won’t delve deeper in the implications of the trust model being used by digital certificates).  
 +
 
 +
 
 +
* Certificates have an associated period of validity, therefore they may expire. Again, we are warned by the browser about this. A public service needs a temporally valid certificate; otherwise, it means we are talking with a server whose certificate was issued by someone we trust, but has expired without being renewed.  
 +
 
 +
 
 +
* What if the name on the certificate and the name of the server do not match? If this happens, it might sound suspicious. For a number of reasons, this is not so rare to see. A system may host a number of name-based virtual hosts, which share the same IP address and are identified by means of the HTTP 1.1 Host: header information. In this case, since the SSL handshake checks the server certificate before the HTTP request is processed, it is not possible to assign different certificates to each virtual server. Therefore, if the name of the site and the name reported in the certificate do not match, we have a condition which is typically signaled by the browser. To avoid this, IP-based virtual servers must be used. [33] and [34] describe techniques to deal with this problem and allow name-based virtual hosts to be correctly referenced.  
 +
 
  
 
===Other vulnerabilities===
 
===Other vulnerabilities===
Moreover, also in the case in which weak cipher suites are not supported by the server, there are others vulnerabilities that could lead an attacker to force a victim into using a non-secure channel instead of a secure one. These vulnerabilities, like SSL Strip attack and Surf Jacking, are possible due to the use, by the server, of both the HTTP and HTTPS protocols to provide the website contents.<br>
+
The presence of a new service, listening in a separate tcp port may introduce vulnerabilities such as infrastructure vulnerabilities if the software is not up to date [4]. Furthermore, for the correct protection of data during transmission the Session Cookie must use the Secure flag [5] and some directives should be sent to the browser to accept only secure traffic (e.g. HSTS [6], CSP [9]).
 +
 
 +
 
 +
Also there are some attacks that can be used to intercept traffic if the web server exposes the application on both HTTP and HTTPS [6], [7] or in case of mixed HTTP and HTTPS resources in the same page.
 +
 
 +
 
 +
== Black Box Testing ==
 +
 
 +
===Testing for sensitive data transmitted in clear-text===
 +
Various types of information which must be protected can be also transmitted in clear text. It is possible to check if this information is transmitted over HTTP instead of HTTPS. Please refer to specific tests for full details, for credentials [3] and other kind of data [2].
 +
 
  
<br>
+
=====Example 1. Basic Authentication over HTTP=====
== Black Box testing and example ==
+
A typical example is the usage of Basic Authentication over HTTP because with Basic Authentication, after log in, credentials are encoded - and not encrypted - into HTTP Headers.
<br>
+
===Testing for Weak SSL/TSL Ciphers vulnerabilities===
+
Large number of available cipher suites and quick progress in cryptanalysis makes judging a SSL server a non-trivial task. These criteria are widely recognized as minimum checklist:<br>
+
* SSLv2, due to known weaknesses in protocol design
+
* Export (EXP) level cipher suites in SSLv3
+
* Cipher suites with symmetric encryption algorithm smaller than 128 bits
+
* X.509 certificates with RSA or DSA key smaller than 1024 bits
+
* X.509 certificates signed using MD5 hash, due to known collision attacks on this hash
+
* TLS Renegotiation vulnerability
+
While there are known collision attacks on MD5 and known crypto-analytical attacks on RC4, their specific usage in SSL and TLS doesn't allow these attacks to be practical and SSLv3 or TLSv1 cipher suites using RC4 and MD5 with key length of 128 bit is still considered sufficient.<br>
+
The following standards can be used as reference while assessing SSL servers:<br>
+
* NIST SP 800-52 recommends U.S. federal systems to use at least TLS 1.0 with ciphersuites based on RSA or DSA key agreement with ephemeral Diffie-Hellman, 3DES or AES for confidentality and SHA1 for integrity protection. NIST SP 800-52 specifically disallows non-FIPS compliant algorithms like RC4 and MD5. An exception is U.S. federal systems making connections to outside servers, where these algorithms can be used in SSL client mode.
+
* PCI-DSS v2.0 in point 4.1 requires compliant parties to use "strong cryptography" without precisely defining key lengths and algorithms. Common interpretation, partially based on previous versions of the standard, is that at least 128 bit key cipher, no export strength algorithms and no SSLv2 should be used.
+
* SSL Server Rating Guide has been proposed to standardize SSL server assessment and currently is in draft version.
+
SSL Server Database can be used to assess configuration of publicly available SSL servers based on SSL Rating Guide[5].<br>
+
In order to detect possible support of weak ciphers, the ports associated to SSL/TLS wrapped services must be identified. These typically include port 443, which is the standard https port; however, this may change because a) https services may be configured to run on non-standard ports, and b) there may be additional SSL/TLS wrapped services related to the web application. In general, a service discovery is required to identify such ports. <br>
+
The nmap scanner, via the “–sV” scan option, is able to identify SSL services. Vulnerability Scanners, in addition to performing service discovery, may include checks against weak ciphers (for example, the Nessus scanner has the capability of checking SSL services on arbitrary ports, and will report weak ciphers). <br>
+
  
''' Example 1. ''' SSL service recognition via nmap.
 
 
<pre>
 
<pre>
[root@test]# nmap -F -sV localhost
+
$ curl -kis http://example.com/restricted/
 +
HTTP/1.1 401 Authorization Required
 +
Date: Fri, 01 Aug 2013 00:00:00 GMT
 +
WWW-Authenticate: Basic realm="Restricted Area"
 +
Accept-Ranges: bytes
 +
Vary: Accept-Encoding
 +
Content-Length: 162
 +
Content-Type: text/html
  
Starting nmap 3.75 ( http://www.insecure.org/nmap/ ) at 2005-07-27 14:41 CEST
+
<html><head><title>401 Authorization Required</title></head>
Interesting ports on localhost.localdomain (127.0.0.1):
+
<body bgcolor=white>
(The 1205 ports scanned but not shown below are in state: closed)
+
<h1>401 Authorization Required</h1>
  
PORT      STATE SERVICE        VERSION
+
Invalid login credentials!
443/tcp  open  ssl            OpenSSL
+
901/tcp  open  http            Samba SWAT administration server
+
8080/tcp  open  http            Apache httpd 2.0.54 ((Unix) mod_ssl/2.0.54 OpenSSL/0.9.7g PHP/4.3.11)
+
8081/tcp  open  http            Apache Tomcat/Coyote JSP engine 1.0
+
  
Nmap run completed -- 1 IP address (1 host up) scanned in 27.881 seconds
+
</body></html>
[root@test]#
+
 
</pre>
 
</pre>
  
''' Example 2. ''' Identifying weak ciphers with Nessus. The following is an anonymized excerpt of a report generated by the Nessus scanner, corresponding to the identification of a server certificate allowing weak ciphers (see underlined text).  
+
 
 +
===Testing for Weak SSL/TLS Ciphers/Protocols/Keys vulnerabilities===
 +
The large number of available cipher suites and quick progress in cryptanalysis makes testing an SSL server a non-trivial task.  
 +
 
 +
At the time of writing these criteria are widely recognized as minimum checklist:
 +
* Weak ciphers must not be used (e.g. less than 128 bits [10]; no NULL ciphers suite, due to no encryption used; no Anonymous Diffie-Hellmann, due to not provides authentication).
 +
* Weak protocols must be disabled (e.g. SSLv2 must be disabled, due to known weaknesses in protocol design [11]).
 +
* Renegotiation must be properly configured (e.g. Insecure Renegotiation must be disabled, due to MiTM attacks [12] and Client-initiated Renegotiation must be disabled, due to Denial of Service vulnerability [13]).
 +
* No Export (EXP) level cipher suites, due to can be easly broken [10].
 +
* X.509 certificates key length must be strong (e.g. if RSA or DSA is used the key must be at least 1024 bits).
 +
* X.509 certificates must be signed only with secure hashing algoritms (e.g. not signed using MD5 hash, due to known collision attacks on this hash).
 +
* Keys must be generated with proper entropy (e.g, Weak Key Generated with Debian) [14].
 +
 
 +
A more complete checklist includes:
 +
* Secure Renegotiation should be enabled.
 +
* MD5 should not be used, due to known collision attacks. [35]
 +
* RC4 should not be used, due to crypto-analytical attacks [15].
 +
* Server should be protected from BEAST Attack [16].
 +
* Server should be protected from CRIME attack, TLS compression must be disabled [17].
 +
* Server should support Forward Secrecy [18].
 +
 
 +
 
 +
The following standards can be used as reference while assessing SSL servers:
 +
* PCI-DSS v2.0 in point 4.1 requires compliant parties to use "strong cryptography" without precisely defining key lengths and algorithms. Common interpretation, partially based on previous versions of the standard, is that at least 128 bit key cipher, no export strength algorithms and no SSLv2 should be used [19].
 +
* Qualys SSL Labs Server Rating Guide [14], Depoloyment best practice [10] and SSL Threat Model [20] has been proposed to standardize SSL server assessment and configuration. But is less updated than the SSL Server tool [21].
 +
* OWASP has a lot of resources about SSL/TLS Security [22], [23], [24], [25]. [26].
 +
 
 +
 
 +
Some tools and scanners both free (e.g. SSLAudit [28] or SSLScan [29]) and commercial (e.g. Tenable Nessus [27]),  can be used to assess SSL/TLS vulnerabilities. But due to evolution of these vulnerabilities a good way to test is to check them manually with openssl [30] or use the tool’s output as an input for manual evaluation using the references.
 +
 
 +
 
 +
Sometimes the SSL/TLS enabled service is not directly accessible and the tester can access it only via a HTTP proxy using CONNECT method [36]. Most of the tools will try to connect to desired tcp port to start SSL/TLS handshake. This will not work since desired port is accessible only via HTTP proxy. The tester can easily circumvent this by using relaying software such as socat [37].
 +
 
 +
 
 +
====Example 2. SSL service recognition via nmap====
 +
 
 +
The first step is to identify ports which have SSL/TLS wrapped services. Typically tcp ports with SSL for web and mail services are -  but not limited to - 443 (https), 465 (ssmtp), 585 (imap4-ssl), 993 (imaps), 995 (ssl-pop).
 +
 
 +
In this example we search for SSL services using nmap with “-sV” option, used to identify services and it is also able to identify SSL services [31]. Other options are for this particular example and must be customized. Often in a Web Application Penetration Test scope is limited to port 80 and 443.
  
 
<pre>
 
<pre>
https (443/tcp)
+
$ nmap -sV --reason -PN -n --top-ports 100 www.example.com
Description
+
Starting Nmap 6.25 ( http://nmap.org ) at 2013-01-01 00:00 CEST
Here is the SSLv2 server certificate:
+
Nmap scan report for www.example.com (127.0.0.1)
Certificate:
+
Host is up, received user-set (0.20s latency).
Data:
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Not shown: 89 filtered ports
Version: 3 (0x2)
+
Reason: 89 no-responses
Serial Number: 1 (0x1)
+
PORT    STATE SERVICE REASON VERSION
Signature Algorithm: md5WithRSAEncryption
+
21/tcp open ftp      syn-ack Pure-FTPd
Issuer: C=**, ST=******, L=******, O=******, OU=******, CN=******
+
22/tcp open ssh      syn-ack OpenSSH 5.3 (protocol 2.0)
Validity
+
25/tcp open smtp    syn-ack Exim smtpd 4.80
Not Before: Oct 17 07:12:16 2002 GMT
+
26/tcp open smtp    syn-ack Exim smtpd 4.80
Not After : Oct 16 07:12:16 2004 GMT
+
80/tcp open http    syn-ack
  Subject: C=**, ST=******, L=******, O=******, CN=******
+
110/tcp open pop3    syn-ack Dovecot pop3d
  Subject Public Key Info:
+
143/tcp open imap    syn-ack Dovecot imapd
  Public Key Algorithm: rsaEncryption
+
443/tcp open ssl/http syn-ack Apache
  RSA Public Key: (1024 bit)
+
465/tcp open ssl/smtp syn-ack Exim smtpd 4.80
Modulus (1024 bit):
+
993/tcp open ssl/imap syn-ack Dovecot imapd
00:98:4f:24:16:cb:0f:74:e8:9c:55:ce:62:14:4e:
+
995/tcp open ssl/pop3 syn-ack Dovecot pop3d
6b:84:c5:81:43:59:c1:2e:ac:ba:af:92:51:f3:0b:
+
Service Info: Hosts: example.com
ad:e1:4b:22:ba:5a:9a:1e:0f:0b:fb:3d:5d:e6:fc:
+
Service detection performed. Please report any incorrect results at http://nmap.org/submit/ .
  ef:b8:8c:dc:78:28:97:8b:f0:1f:17:9f:69:3f:0e:
+
Nmap done: 1 IP address (1 host up) scanned in 131.38 seconds
  72:51:24:1b:9c:3d:85:52:1d:df:da:5a:b8:2e:d2:
+
</pre>
09:00:76:24:43:bc:08:67:6b:dd:6b:e9:d2:f5:67:
+
e1:90:2a:b4:3b:b4:3c:b3:71:4e:88:08:74:b9:a8:
+
2d:c4:8c:65:93:08:e6:2f:fd:e0:fa:dc:6d:d7:a2:
+
3d:0a:75:26:cf:dc:47:74:29
+
Exponent: 65537 (0x10001)
+
  X509v3 extensions:
+
  X509v3 Basic Constraints:
+
CA:FALSE
+
Netscape Comment:
+
OpenSSL Generated Certificate
+
Page 10
+
Network Vulnerability Assessment Report 25.05.2005
+
X509v3 Subject Key Identifier:
+
10:00:38:4C:45:F0:7C:E4:C6:A7:A4:E2:C9:F0:E4:2B:A8:F9:63:A8
+
X509v3 Authority Key Identifier:
+
keyid:CE:E5:F9:41:7B:D9:0E:5E:5D:DF:5E:B9:F3:E6:4A:12:19:02:76:CE
+
DirName:/C=**/ST=******/L=******/O=******/OU=******/CN=******
+
  serial:00
+
Signature Algorithm: md5WithRSAEncryption
+
7b:14:bd:c7:3c:0c:01:8d:69:91:95:46:5c:e6:1e:25:9b:aa:
+
8b:f5:0d:de:e3:2e:82:1e:68:be:97:3b:39:4a:83:ae:fd:15:
+
2e:50:c8:a7:16:6e:c9:4e:76:cc:fd:69:ae:4f:12:b8:e7:01:
+
b6:58:7e:39:d1:fa:8d:49:bd:ff:6b:a8:dd:ae:83:ed:bc:b2:
+
40:e3:a5:e0:fd:ae:3f:57:4d:ec:f3:21:34:b1:84:97:06:6f:
+
f4:7d:f4:1c:84:cc:bb:1c:1c:e7:7a:7d:2d:e9:49:60:93:12:
+
0d:9f:05:8c:8e:f9:cf:e8:9f:fc:15:c0:6e:e2:fe:e5:07:81:
+
82:fc
+
Here is the list of available SSLv2 ciphers:
+
  RC4-MD5
+
  EXP-RC4-MD5
+
  RC2-CBC-MD5
+
  EXP-RC2-CBC-MD5
+
  DES-CBC-MD5
+
  DES-CBC3-MD5
+
  RC4-64-MD5
+
The SSLv2 server offers 5 strong ciphers, but also 0 medium strength and 2 weak "export class" ciphers.
+
  The weak/medium ciphers may be chosen by an export-grade or badly configured client software. They only offer a limited protection against a brute force attack
+
  Solution: disable those ciphers and upgrade your client software if necessary.
+
See http://support.microsoft.com/default.aspx?scid=kben-us216482
+
or http://httpd.apache.org/docs-2.0/mod/mod_ssl.html#sslciphersuite
+
This SSLv2 server also accepts SSLv3 connections.
+
This SSLv2 server also accepts TLSv1 connections.
+
+
Vulnerable hosts
+
(list of vulnerable hosts follows)
+
  
 +
 +
====Example 3. Checking for Certificate information, Weak Ciphers and SSLv2 via nmap====
 +
Nmap has two scripts for checking Certificate information, Weak Ciphers and SSLv2 [31].
 +
 +
<pre>
 +
$ nmap --script ssl-cert,ssl-enum-ciphers -p 443,465,993,995 www.example.com
 +
Starting Nmap 6.25 ( http://nmap.org ) at 2013-01-01 00:00 CEST
 +
Nmap scan report for www.example.com (127.0.0.1)
 +
Host is up (0.090s latency).
 +
rDNS record for 127.0.0.1: www.example.com
 +
PORT    STATE SERVICE
 +
443/tcp open  https
 +
| ssl-cert: Subject: commonName=www.example.org
 +
| Issuer: commonName=*******
 +
| Public Key type: rsa
 +
| Public Key bits: 1024
 +
| Not valid before: 2010-01-23T00:00:00+00:00
 +
| Not valid after:  2020-02-28T23:59:59+00:00
 +
| MD5:  *******
 +
|_SHA-1: *******
 +
| ssl-enum-ciphers:
 +
|  SSLv3:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|  TLSv1.0:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|_  least strength: strong
 +
465/tcp open  smtps
 +
| ssl-cert: Subject: commonName=*.exapmple.com
 +
| Issuer: commonName=*******
 +
| Public Key type: rsa
 +
| Public Key bits: 2048
 +
| Not valid before: 2010-01-23T00:00:00+00:00
 +
| Not valid after:  2020-02-28T23:59:59+00:00
 +
| MD5:  *******
 +
|_SHA-1: *******
 +
| ssl-enum-ciphers:
 +
|  SSLv3:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|  TLSv1.0:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|_  least strength: strong
 +
993/tcp open  imaps
 +
| ssl-cert: Subject: commonName=*.exapmple.com
 +
| Issuer: commonName=*******
 +
| Public Key type: rsa
 +
| Public Key bits: 2048
 +
| Not valid before: 2010-01-23T00:00:00+00:00
 +
| Not valid after:  2020-02-28T23:59:59+00:00
 +
| MD5:  *******
 +
|_SHA-1: *******
 +
| ssl-enum-ciphers:
 +
|  SSLv3:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|  TLSv1.0:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|_  least strength: strong
 +
995/tcp open  pop3s
 +
| ssl-cert: Subject: commonName=*.exapmple.com
 +
| Issuer: commonName=*******
 +
| Public Key type: rsa
 +
| Public Key bits: 2048
 +
| Not valid before: 2010-01-23T00:00:00+00:00
 +
| Not valid after:  2020-02-28T23:59:59+00:00
 +
| MD5:  *******
 +
|_SHA-1: *******
 +
| ssl-enum-ciphers:
 +
|  SSLv3:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|  TLSv1.0:
 +
|    ciphers:
 +
|      TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
 +
|      TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
 +
|      TLS_RSA_WITH_RC4_128_SHA - strong
 +
|    compressors:
 +
|      NULL
 +
|_  least strength: strong
 +
Nmap done: 1 IP address (1 host up) scanned in 8.64 seconds
 
</pre>
 
</pre>
''' Example 3. ''' Manually audit weak SSL cipher levels with OpenSSL. The following will attempt to connect to Google.com with SSLv2.
 
  
 +
 +
====Example 4 Checking for Client-initiated Renegotiation and Secure Renegotiation via openssl (manually)====
 +
 +
Openssl [30] can be used for testing manually SSL/TLS. In this example the tester tries to initiate a renegotiation by client [m] connecting to server with openssl. The tester then writes the fist line of an HTTP request and types “R” in a new line. He then waits for renegotiaion and completion of the HTTP request and checks if secure renegotiaion is supported by looking at the  server output. Using manual requests it is also possible to see if Compression is enabled for TLS and to check for CRIME [13], for ciphers and for other vulnerabilities.
  
 
<pre>
 
<pre>
[root@test]# openssl s_client -no_tls1 -no_ssl3 -connect www.google.com:443
+
$ openssl s_client -connect www2.example.com:443
 
CONNECTED(00000003)
 
CONNECTED(00000003)
depth=0 /C=US/ST=California/L=Mountain View/O=Google Inc/CN=www.google.com
+
depth=2 ******
 
verify error:num=20:unable to get local issuer certificate
 
verify error:num=20:unable to get local issuer certificate
verify return:1
+
verify return:0
depth=0 /C=US/ST=California/L=Mountain View/O=Google Inc/CN=www.google.com
+
---
verify error:num=27:certificate not trusted
+
Certificate chain
verify return:1
+
0 s:******
depth=0 /C=US/ST=California/L=Mountain View/O=Google Inc/CN=www.google.com
+
  i:******
verify error:num=21:unable to verify the first certificate
+
1 s:******
verify return:1
+
  i:******
 +
2 s:******
 +
  i:******
 
---
 
---
 
Server certificate
 
Server certificate
 
-----BEGIN CERTIFICATE-----
 
-----BEGIN CERTIFICATE-----
MIIDYzCCAsygAwIBAgIQYFbAC3yUC8RFj9MS7lfBkzANBgkqhkiG9w0BAQQFADCB
+
******
zjELMAkGA1UEBhMCWkExFTATBgNVBAgTDFdlc3Rlcm4gQ2FwZTESMBAGA1UEBxMJ
+
Q2FwZSBUb3duMR0wGwYDVQQKExRUaGF3dGUgQ29uc3VsdGluZyBjYzEoMCYGA1UE
+
CxMfQ2VydGlmaWNhdGlvbiBTZXJ2aWNlcyBEaXZpc2lvbjEhMB8GA1UEAxMYVGhh
+
d3RlIFByZW1pdW0gU2VydmVyIENBMSgwJgYJKoZIhvcNAQkBFhlwcmVtaXVtLXNl
+
cnZlckB0aGF3dGUuY29tMB4XDTA2MDQyMTAxMDc0NVoXDTA3MDQyMTAxMDc0NVow
+
aDELMAkGA1UEBhMCVVMxEzARBgNVBAgTCkNhbGlmb3JuaWExFjAUBgNVBAcTDU1v
+
dW50YWluIFZpZXcxEzARBgNVBAoTCkdvb2dsZSBJbmMxFzAVBgNVBAMTDnd3dy5n
+
b29nbGUuY29tMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC/e2Vs8U33fRDk
+
5NNpNgkB1zKw4rqTozmfwty7eTEI8PVH1Bf6nthocQ9d9SgJAI2WOBP4grPj7MqO
+
dXMTFWGDfiTnwes16G7NZlyh6peT68r7ifrwSsVLisJp6pUf31M5Z3D88b+Yy4PE
+
D7BJaTxq6NNmP1vYUJeXsGSGrV6FUQIDAQABo4GmMIGjMB0GA1UdJQQWMBQGCCsG
+
AQUFBwMBBggrBgEFBQcDAjBABgNVHR8EOTA3MDWgM6Axhi9odHRwOi8vY3JsLnRo
+
YXd0ZS5jb20vVGhhd3RlUHJlbWl1bVNlcnZlckNBLmNybDAyBggrBgEFBQcBAQQm
+
MCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3NwLnRoYXd0ZS5jb20wDAYDVR0TAQH/
+
BAIwADANBgkqhkiG9w0BAQQFAAOBgQADlTbBdVY6LD1nHWkhTadmzuWq2rWE0KO3
+
Ay+7EleYWPOo+EST315QLpU6pQgblgobGoI5x/fUg2U8WiYj1I1cbavhX2h1hda3
+
FJWnB3SiXaiuDTsGxQ267EwCVWD5bCrSWa64ilSJTgiUmzAv0a2W8YHXdG08+nYc
+
X/dVk5WRTw==
+
 
-----END CERTIFICATE-----
 
-----END CERTIFICATE-----
subject=/C=US/ST=California/L=Mountain View/O=Google Inc/CN=www.google.com
+
subject=******
issuer=/C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services Division/CN=Thawte Premium Server CA/emailAddress=premium-server@thawte.com
+
issuer=******
 
---
 
---
 
No client certificate CA names sent
 
No client certificate CA names sent
 
---
 
---
Ciphers common between both SSL endpoints:
+
SSL handshake has read 3558 bytes and written 640 bytes
RC4-MD5        EXP-RC4-MD5    RC2-CBC-MD5
+
EXP-RC2-CBC-MD5 DES-CBC-MD5    DES-CBC3-MD5
+
RC4-64-MD5
+
 
---
 
---
SSL handshake has read 1023 bytes and written 333 bytes
+
New, TLSv1/SSLv3, Cipher is DES-CBC3-SHA
---
+
Server public key is 2048 bit
New, SSLv2, Cipher is DES-CBC3-MD5
+
Secure Renegotiation IS NOT supported
Server public key is 1024 bit
+
 
Compression: NONE
 
Compression: NONE
 
Expansion: NONE
 
Expansion: NONE
 
SSL-Session:
 
SSL-Session:
     Protocol  : SSLv2
+
     Protocol  : TLSv1
     Cipher    : DES-CBC3-MD5
+
     Cipher    : DES-CBC3-SHA
     Session-ID: 709F48E4D567C70A2E49886E4C697CDE
+
     Session-ID: ******
     Session-ID-ctx:
+
     Session-ID-ctx:  
     Master-Key: 649E68F8CF936E69642286AC40A80F433602E3C36FD288C3
+
     Master-Key: ******
     Key-Arg  : E8CB6FEB9ECF3033
+
     Key-Arg  : None
     Start Time: 1156977226
+
    PSK identity: None
 +
    PSK identity hint: None
 +
    SRP username: None
 +
     Start Time: ******
 
     Timeout  : 300 (sec)
 
     Timeout  : 300 (sec)
     Verify return code: 21 (unable to verify the first certificate)
+
     Verify return code: 20 (unable to get local issuer certificate)
 
---
 
---
closed
 
 
</pre>
 
</pre>
  
''' Example 4. ''' Testing supported protocols and ciphers using SSLScan. <br>
 
SSLScan is a free command line tool that scans a HTTPS service to enumerate what protocols (supports SSLv2, SSLv3 and TLS1) and what ciphers the HTTPS service supports. It runs both on Linux and Windows OS (OSX not tested) and is released under an open source license.
 
  
 +
Now the tester can write the first line of an HTTP request and then R in a new line.
 
<pre>
 
<pre>
[user@test]$ ./SSLScan --no-failed mail.google.com
+
HEAD / HTTP/1.1
                  _
+
R
          ___ ___| |___  ___ __ _ _ __
+
</pre>
          / __/ __| / __|/ __/ _` | '_ \
+
          \__ \__ \ \__ \ (_| (_| | | | |
+
          |___/___/_|___/\___\__,_|_| |_|
+
  
                  Version 1.9.0-win
+
Server is renegotiating
            http://www.titania.co.uk
+
<pre>
Copyright 2010 Ian Ventura-Whiting / Michael Boman
+
RENEGOTIATING
    Compiled against OpenSSL 0.9.8n 24 Mar 2010
+
depth=2 C******
 +
verify error:num=20:unable to get local issuer certificate
 +
verify return:0
 +
</pre>
  
Testing SSL server mail.google.com on port 443
+
And the tester can complete our request, checking for response.
 +
<pre>
 +
HEAD / HTTP/1.1
  
  Supported Server Cipher(s):
+
HTTP/1.1 403 Forbidden ( The server denies the specified Uniform Resource Locator (URL). Contact the server administrator. )
    accepted SSLv3  256 bits  AES256-SHA
+
Connection: close
    accepted  SSLv3  128 bits  AES128-SHA
+
Pragma: no-cache
    accepted  SSLv3  168 bits  DES-CBC3-SHA
+
Cache-Control: no-cache
    accepted  SSLv3  128 bits  RC4-SHA
+
Content-Type: text/html
    accepted  SSLv3  128 bits  RC4-MD5
+
Content-Length: 1792  
    accepted  TLSv1  256 bits  AES256-SHA
+
    accepted  TLSv1  128 bits  AES128-SHA
+
    accepted TLSv1  168 bits  DES-CBC3-SHA
+
    accepted  TLSv1  128 bits  RC4-SHA
+
    accepted  TLSv1  128 bits  RC4-MD5
+
  
  Prefered Server Cipher(s):
+
read:errno=0
    SSLv3  128 bits  RC4-SHA
+
</pre>
    TLSv1  128 bits  RC4-SHA
+
  
  SSL Certificate:
+
Even if the HEAD is not permitted, Client-intiated renegotiaion is permitted.
    Version: 2
+
    Serial Number: -4294967295
+
    Signature Algorithm: sha1WithRSAEncryption
+
    Issuer: /C=ZA/O=Thawte Consulting (Pty) Ltd./CN=Thawte SGC CA
+
    Not valid before: Dec 18 00:00:00 2009 GMT
+
    Not valid after: Dec 18 23:59:59 2011 GMT
+
    Subject: /C=US/ST=California/L=Mountain View/O=Google Inc/CN=mail.google.com
+
    Public Key Algorithm: rsaEncryption
+
    RSA Public Key: (1024 bit)
+
      Modulus (1024 bit):
+
          00:d9:27:c8:11:f2:7b:e4:45:c9:46:b6:63:75:83:
+
          b1:77:7e:17:41:89:80:38:f1:45:27:a0:3c:d9:e8:
+
          a8:00:4b:d9:07:d0:ba:de:ed:f4:2c:a6:ac:dc:27:
+
          13:ec:0c:c1:a6:99:17:42:e6:8d:27:d2:81:14:b0:
+
          4b:82:fa:b2:c5:d0:bb:20:59:62:28:a3:96:b5:61:
+
          f6:76:c1:6d:46:d2:fd:ba:c6:0f:3d:d1:c9:77:9a:
+
          58:33:f6:06:76:32:ad:51:5f:29:5f:6e:f8:12:8b:
+
          ad:e6:c5:08:39:b3:43:43:a9:5b:91:1d:d7:e3:cf:
+
          51:df:75:59:8e:8d:80:ab:53
+
      Exponent: 65537 (0x10001)
+
    X509v3 Extensions:
+
      X509v3 Basic Constraints: critical
+
        CA:FALSE      X509v3 CRL Distribution Points:
+
        URI:http://crl.thawte.com/ThawteSGCCA.crl
+
      X509v3 Extended Key Usage:
+
        TLS Web Server Authentication, TLS Web Client Authentication, Netscape Server Gated Crypto      Authority Information Access:
+
        OCSP - URI:http://ocsp.thawte.com
+
        CA Issuers - URI:http://www.thawte.com/repository/Thawte_SGC_CA.crt
+
  Verify Certificate:
+
    unable to get local issuer certificate
+
  
  
Renegotiation requests supported
+
====Example 5. Testing supported Cipher Suites, BEAST and CRIME attacks via TestSSLServer====
 +
 
 +
TestSSLServer [32] is a script which permits the tester to check the cipher suite and also for BEAST and CRIME attacks. BEAST (Browser Exploit Against SSL/TLS)  exploits a vulnerability of CBC in TLS 1.0. CRIME (Compression Ratio Info-leak Made Easy) exploits a vulnerability of TLS Compression, that should be disabled. What is interesting is that the first fix for BEAST was the use of RC4, but this is now discouraged due to a crypto-analytical attack to RC4 [15].
 +
 
 +
 
 +
An online tool to check for these attacks is SSL Labs, but can be used only for internet facing servers. Also consider that target data will be stored on SSL Labs server and also will result some connection from SSL Labs server [21].
 +
 
 +
<pre>
 +
$ java -jar TestSSLServer.jar www3.example.com 443
 +
Supported versions: SSLv3 TLSv1.0 TLSv1.1 TLSv1.2
 +
Deflate compression: no
 +
Supported cipher suites (ORDER IS NOT SIGNIFICANT):
 +
  SSLv3
 +
    RSA_WITH_RC4_128_SHA
 +
    RSA_WITH_3DES_EDE_CBC_SHA
 +
    DHE_RSA_WITH_3DES_EDE_CBC_SHA
 +
    RSA_WITH_AES_128_CBC_SHA
 +
    DHE_RSA_WITH_AES_128_CBC_SHA
 +
    RSA_WITH_AES_256_CBC_SHA
 +
    DHE_RSA_WITH_AES_256_CBC_SHA
 +
    RSA_WITH_CAMELLIA_128_CBC_SHA
 +
    DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 +
    RSA_WITH_CAMELLIA_256_CBC_SHA
 +
    DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 +
    TLS_RSA_WITH_SEED_CBC_SHA
 +
    TLS_DHE_RSA_WITH_SEED_CBC_SHA
 +
  (TLSv1.0: idem)
 +
  (TLSv1.1: idem)
 +
  TLSv1.2
 +
    RSA_WITH_RC4_128_SHA
 +
    RSA_WITH_3DES_EDE_CBC_SHA
 +
    DHE_RSA_WITH_3DES_EDE_CBC_SHA
 +
    RSA_WITH_AES_128_CBC_SHA
 +
    DHE_RSA_WITH_AES_128_CBC_SHA
 +
    RSA_WITH_AES_256_CBC_SHA
 +
    DHE_RSA_WITH_AES_256_CBC_SHA
 +
    RSA_WITH_AES_128_CBC_SHA256
 +
    RSA_WITH_AES_256_CBC_SHA256
 +
    RSA_WITH_CAMELLIA_128_CBC_SHA
 +
    DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
 +
    DHE_RSA_WITH_AES_128_CBC_SHA256
 +
    DHE_RSA_WITH_AES_256_CBC_SHA256
 +
    RSA_WITH_CAMELLIA_256_CBC_SHA
 +
    DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
 +
    TLS_RSA_WITH_SEED_CBC_SHA
 +
    TLS_DHE_RSA_WITH_SEED_CBC_SHA
 +
    TLS_RSA_WITH_AES_128_GCM_SHA256
 +
    TLS_RSA_WITH_AES_256_GCM_SHA384
 +
    TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
 +
    TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
 +
----------------------
 +
Server certificate(s):
 +
  ******
 +
----------------------
 +
Minimal encryption strength:    strong encryption (96-bit or more)
 +
Achievable encryption strength:  strong encryption (96-bit or more)
 +
BEAST status: vulnerable
 +
CRIME status: protected
 +
 
 
</pre>
 
</pre>
  
''' Example 5. ''' Testing common SSL flaws with ssl_tests <br>
+
 
ssl_tests (http://www.pentesterscripting.com/discovery/ssl_tests) is a bash script that uses sslscan and openssl to check for various flaws - ssl version 2, weak ciphers, md5withRSAEncryption,SSLv3 Force Ciphering Bug/Renegotiation.  
+
====Example 6. Testing SSL/TLS vulnerabilities with sslyze====
 +
Sslyze [33] is a python script which permits mass scanning and XML output. The following is an example of a regular scan. It is one of the most complete and versatile tools for SSL/TLS testing.
  
 
<pre>
 
<pre>
[user@test]$ ./ssl_test.sh 192.168.1.3 443
+
./sslyze.py --regular example.com:443
+++++++++++++++++++++++++++++++++++++++++++++++++
+
SSL Tests - v2, weak ciphers, MD5, Renegotiation
+
by Aung Khant, http://yehg.net
+
+++++++++++++++++++++++++++++++++++++++++++++++++
+
  
[*] testing on 192.168.1.3:443 ..
+
REGISTERING AVAILABLE PLUGINS
 +
-----------------------------
  
[*] tesing for sslv2 ..
+
  PluginHSTS
[*] sslscan 192.168.1.3:443 | grep Accepted  SSLv2
+
  PluginSessionRenegotiation
    Accepted  SSLv2  168 bits  DES-CBC3-MD5
+
   PluginCertInfo
    Accepted  SSLv2  56 bits   DES-CBC-MD5
+
   PluginSessionResumption
    Accepted  SSLv2  40 bits   EXP-RC2-CBC-MD5
+
   PluginOpenSSLCipherSuites
    Accepted  SSLv2  128 bits  RC2-CBC-MD5
+
  PluginCompression
    Accepted  SSLv2  40 bits   EXP-RC4-MD5
+
    Accepted  SSLv2  128 bits  RC4-MD5
+
  
  
[*] testing for weak ciphers ...
 
[*] sslscan 192.168.1.3:443 | grep  40 bits | grep Accepted
 
    Accepted  SSLv2  40 bits  EXP-RC2-CBC-MD5
 
    Accepted  SSLv2  40 bits  EXP-RC4-MD5
 
    Accepted  SSLv3  40 bits  EXP-EDH-RSA-DES-CBC-SHA
 
    Accepted  SSLv3  40 bits  EXP-DES-CBC-SHA
 
    Accepted  SSLv3  40 bits  EXP-RC2-CBC-MD5
 
    Accepted  SSLv3  40 bits  EXP-RC4-MD5
 
    Accepted  TLSv1  40 bits  EXP-EDH-RSA-DES-CBC-SHA
 
    Accepted  TLSv1  40 bits  EXP-DES-CBC-SHA
 
    Accepted  TLSv1  40 bits  EXP-RC2-CBC-MD5
 
    Accepted  TLSv1  40 bits  EXP-RC4-MD5
 
  
[*] sslscan 192.168.1.3:443 | grep 56 bits | grep Accepted
+
  CHECKING HOST(S) AVAILABILITY
    Accepted SSLv2  56 bits  DES-CBC-MD5
+
  -----------------------------
    Accepted  SSLv3  56 bits  EDH-RSA-DES-CBC-SHA
+
    Accepted  SSLv3  56 bits  DES-CBC-SHA
+
    Accepted  TLSv1  56 bits  EDH-RSA-DES-CBC-SHA
+
    Accepted  TLSv1  56 bits  DES-CBC-SHA
+
  
 +
  example.com:443                      => 127.0.0.1:443
  
[*] testing for MD5 certificate ..
 
[*] sslscan 192.168.1.3:443 | grep MD5WithRSAEncryption
 
  
[*] testing for SSLv3 Force Ciphering Bug/Renegotiation ..
+
 
[*] echo R | openssl s_client -connect 192.168.1.3:443 | grep DONE
+
SCAN RESULTS FOR EXAMPLE.COM:443 - 127.0.0.1:443
depth=0 /C=DE/ST=Berlin/L=Berlin/O=XAMPP/OU=XAMPP/CN=localhost/emailAddress=admin@localhost
+
---------------------------------------------------
verify error:num=18:self signed certificate
+
 
verify return:1
+
  * Compression :
depth=0 /C=DE/ST=Berlin/L=Berlin/O=XAMPP/OU=XAMPP/CN=localhost/emailAddress=admin@localhost
+
        Compression Support:      Disabled
verify return:1
+
 
RENEGOTIATING
+
  * Session Renegotiation :
depth=0 /C=DE/ST=Berlin/L=Berlin/O=XAMPP/OU=XAMPP/CN=localhost/emailAddress=admin@localhost
+
      Client-initiated Renegotiations:    Rejected
verify error:num=18:self signed certificate
+
      Secure Renegotiation:              Supported
verify return:1
+
 
depth=0 /C=DE/ST=Berlin/L=Berlin/O=XAMPP/OU=XAMPP/CN=localhost/emailAddress=admin@localhost
+
  * Certificate :
verify return:1
+
      Validation w/ Mozilla's CA Store:  Certificate is NOT Trusted: unable to get local issuer certificate
DONE
+
      Hostname Validation:              MISMATCH                         
 +
      SHA1 Fingerprint:                  ******
 +
 
 +
      Common Name:                      www.example.com                   
 +
      Issuer:                            ******
 +
      Serial Number:                    ****                             
 +
      Not Before:                        Sep 26 00:00:00 2010 GMT         
 +
      Not After:                        Sep 26 23:59:59 2020 GMT 
 +
     
 +
      Signature Algorithm:              sha1WithRSAEncryption             
 +
      Key Size:                          1024 bit                         
 +
      X509v3 Subject Alternative Name:  {'othername': ['<unsupported>'], 'DNS': ['www.example.com']}
 +
 
 +
  * OCSP Stapling :
 +
      Server did not send back an OCSP response.                                  
 +
 
 +
  * Session Resumption :
 +
      With Session IDs:          Supported (5 successful, 0 failed, 0 errors, 5 total attempts).
 +
      With TLS Session Tickets:  Supported
 +
 
 +
  * SSLV2 Cipher Suites :
 +
 
 +
      Rejected Cipher Suite(s): Hidden
 +
 
 +
      Preferred Cipher Suite: None   
 +
 
 +
      Accepted Cipher Suite(s): None 
 +
 
 +
      Undefined - An unexpected error happened: None
 +
 
 +
  * SSLV3 Cipher Suites :
 +
 
 +
      Rejected Cipher Suite(s): Hidden
 +
 
 +
      Preferred Cipher Suite:        
 +
        RC4-SHA                      128 bits      HTTP 200 OK                       
 +
 
 +
      Accepted Cipher Suite(s):       
 +
        CAMELLIA256-SHA              256 bits      HTTP 200 OK                       
 +
        RC4-SHA                      128 bits      HTTP 200 OK                       
 +
        CAMELLIA128-SHA              128 bits      HTTP 200 OK                       
 +
 
 +
      Undefined - An unexpected error happened: None
 +
 
 +
  * TLSV1_1 Cipher Suites :
 +
 
 +
      Rejected Cipher Suite(s): Hidden
 +
 
 +
      Preferred Cipher Suite: None   
 +
 
 +
      Accepted Cipher Suite(s): None 
 +
 
 +
      Undefined - An unexpected error happened:
 +
        ECDH-RSA-AES256-SHA            socket.timeout - timed out       
 +
        ECDH-ECDSA-AES256-SHA          socket.timeout - timed out       
 +
 
 +
  * TLSV1_2 Cipher Suites :
 +
 
 +
      Rejected Cipher Suite(s): Hidden
 +
 
 +
      Preferred Cipher Suite: None   
 +
 
 +
      Accepted Cipher Suite(s): None 
 +
 
 +
      Undefined - An unexpected error happened:
 +
        ECDH-RSA-AES256-GCM-SHA384      socket.timeout - timed out       
 +
        ECDH-ECDSA-AES256-GCM-SHA384    socket.timeout - timed out       
 +
 
 +
  * TLSV1 Cipher Suites :
 +
 
 +
      Rejected Cipher Suite(s): Hidden
 +
 
 +
      Preferred Cipher Suite:         
 +
        RC4-SHA                      128 bits      Timeout on HTTP GET               
 +
 
 +
      Accepted Cipher Suite(s):       
 +
        CAMELLIA256-SHA              256 bits      HTTP 200 OK                       
 +
        RC4-SHA                      128 bits      HTTP 200 OK                       
 +
        CAMELLIA128-SHA              128 bits      HTTP 200 OK                       
 +
 
 +
      Undefined - An unexpected error happened:
 +
        ADH-CAMELLIA256-SHA            socket.timeout - timed out       
 +
 
  
  
[*] done
+
SCAN COMPLETED IN 9.68 S
 +
------------------------
 
</pre>
 
</pre>
  
'''Example 6.''' Testing common SSL flaws with SSL Server Test<br>
+
 
SSL Server Test (https://www.ssllabs.com/ssltest/index.html) is a free online service, provided by Qualys SSL Labs, that performs a deep analysis of the configuration of any SSL web server on the public Internet. It’s a very easy to use but powerful tool. You have only to provide to the tool the URL of the website that you have to test, and the tool returns a lot of information about the protocols and cipher suites support by the server, with details about any flaws found.  
+
====Example 7. Testing SSL/TLS with testssl.sh====
 +
Testssl.sh [38] is a Linux shell script which provides clear output to facilitate good decision making. It can not only check web servers but also services on other ports, supports STARTTLS, SNI, SPDY and does a few check on the HTTP header as well.
 +
 
 +
 
 +
It's a very easy to use tool. Here's some sample output (without colors):
 +
<pre>
 +
user@myhost: % testssl.sh owasp.org     
 +
 
 +
########################################################
 +
testssl.sh v2.0rc3  (https://testssl.sh)
 +
($Id: testssl.sh,v 1.97 2014/04/15 21:54:29 dirkw Exp $)
 +
 
 +
  This program is free software. Redistribution +
 +
  modification under GPLv2 is permitted.
 +
  USAGE w/o ANY WARRANTY. USE IT AT YOUR OWN RISK!
 +
 
 +
Note you can only check the server against what is
 +
available (ciphers/protocols) locally on your machine
 +
########################################################
 +
 
 +
Using "OpenSSL 1.0.2-beta1 24 Feb 2014" on
 +
      "myhost:/<mypath>/bin/openssl64"
 +
 
 +
 
 +
Testing now (2014-04-17 15:06) ---> owasp.org:443 <---
 +
("owasp.org" resolves to "192.237.166.62 / 2001:4801:7821:77:cd2c:d9de:ff10:170e")
 +
 
 +
 
 +
--> Testing Protocols
 +
 +
SSLv2    NOT offered (ok)
 +
SSLv3    offered
 +
TLSv1    offered (ok)
 +
TLSv1.1  offered (ok)
 +
TLSv1.2  offered (ok)
 +
 
 +
SPDY/NPN  not offered
 +
 
 +
--> Testing standard cipher lists
 +
 +
Null Cipher              NOT offered (ok)
 +
Anonymous NULL Cipher    NOT offered (ok)
 +
Anonymous DH Cipher      NOT offered (ok)
 +
40 Bit encryption        NOT offered (ok)
 +
56 Bit encryption        NOT offered (ok)
 +
Export Cipher (general)  NOT offered (ok)
 +
Low (<=64 Bit)          NOT offered (ok)
 +
DES Cipher              NOT offered (ok)
 +
Triple DES Cipher        offered
 +
Medium grade encryption  offered
 +
High grade encryption    offered (ok)
 +
 
 +
--> Testing server defaults (Server Hello)
 +
 +
Negotiated protocol      TLSv1.2
 +
Negotiated cipher        AES128-GCM-SHA256
 +
 +
Server key size          2048 bit
 +
TLS server extensions:    server name, renegotiation info, session ticket, heartbeat
 +
Session Tickets RFC 5077  300 seconds
 +
 
 +
--> Testing specific vulnerabilities
 +
 +
Heartbleed (CVE-2014-0160), experimental  NOT vulnerable (ok)
 +
Renegotiation (CVE 2009-3555)            NOT vulnerable (ok)
 +
CRIME, TLS (CVE-2012-4929)                NOT vulnerable (ok) 
 +
 
 +
--> Checking RC4 Ciphers
 +
 
 +
RC4 seems generally available. Now testing specific ciphers...
 +
 +
Hexcode    Cipher Name                  KeyExch.  Encryption Bits
 +
--------------------------------------------------------------------
 +
[0x05]    RC4-SHA                      RSA        RC4      128
 +
 
 +
RC4 is kind of broken, for e.g. IE6 consider 0x13 or 0x0a
 +
 
 +
--> Testing HTTP Header response
 +
 +
HSTS        no
 +
Server      Apache
 +
Application (None)
 +
 +
--> Testing (Perfect) Forward Secrecy  (P)FS)
 +
 
 +
no PFS available
 +
 
 +
Done now (2014-04-17 15:07) ---> owasp.org:443 <---
 +
 
 +
user@myhost: %   
 +
 
 +
 
 +
</pre>
 +
 
 +
 
 +
STARTTLS would be tested via <code>testssl.sh -t smtp.gmail.com:587  smtp</code>, each ciphers with <code>testssl -e <target></code>, each ciphers per protocol with <code>testssl -E <target></code>. To just display what local ciphers that are installed for openssl see <code>testssl -V</code>. For a thorough check it is best to dump the supplied OpenSSL binaries in the path or the one of testssl.sh.
 +
 
 +
 
 +
The interesting thing is if a tester looks at the sources they learn how features are tested, see e.g. Example 4. What is even better is that it does the whole handshake for heartbleed in pure /bin/bash with /dev/tcp sockets -- no piggyback perl/python/you name it.
 +
 
 +
 
 +
Additionally it provides a prototype (via "testssl.sh -V") of mapping to RFC cipher suite names to OpenSSL ones. The tester needs the file mapping-rfc.txt in same directory.
  
  
 
===Testing SSL certificate validity – client and server===
 
===Testing SSL certificate validity – client and server===
 +
Firstly upgrade the browser because CA certs expire and in every release of the browser these are renewed. Examine the validity of the certificates used by the application. Browsers will issue a warning when encountering expired certificates, certificates issued by untrusted CAs, and certificates which do not match name wise with the site to which they should refer.
  
Firstly upgrade your browser because also CA certs expire and, in every release of the browser, these are been renewed.<br>
 
Examine the validity of the certificates used by the application. Browsers will issue a warning when encountering expired certificates, certificates issued by untrusted CAs, and certificates which do not match namewise with the site to which they should refer. By clicking on the padlock which appears in the browser window when visiting an HTTPS site, you can look at information related to the certificate – including the issuer, period of validity, encryption characteristics, etc.
 
If the application requires a client certificate, you probably have installed one to access it. Certificate information is available in the browser by inspecting the relevant certificate(s) in the list of the installed certificates. <br>
 
These checks must be applied to all visible SSL-wrapped communication channels used by the application. Though this is the usual https service running on port 443, there may be additional services involved depending on the web application architecture and on deployment issues (an HTTPS administrative port left open, HTTPS services on non-standard ports, etc.). Therefore, apply these checks to all SSL-wrapped ports which have been discovered. For example, the nmap scanner features a scanning mode (enabled by the –sV command line switch) which identifies SSL-wrapped services. The Nessus vulnerability scanner has the capability of performing SSL checks on all SSL/TLS-wrapped services. <br>
 
  
'''Examples'''
+
By clicking on the padlock that appears in the browser window when visiting an HTTPS site, testers can look at information related to the certificate – including the issuer, period of validity, encryption characteristics, etc. If the application requires a client certificate, that tester has probably installed one to access it. Certificate information is available in the browser by inspecting the relevant certificate(s) in the list of the installed certificates.  
Rather than providing a fictitious example, we have inserted an anonymized real-life example to stress how frequently one stumbles on https sites whose certificates are inaccurate with respect to naming. <br>
+
The following screenshots refer to a regional site of a high-profile IT company. <br>
+
<u>Warning issued by Microsoft Internet Explorer</u>. We are visiting an .it site and the certificate was issued to a .com site! Internet Explorer warns that the name on the certificate does not match the name of the site. <br>
+
  
 +
 +
These checks must be applied to all visible SSL-wrapped communication channels used by the application. Though this is the usual https service running on port 443, there may be additional services involved depending on the web application architecture and on deployment issues (an HTTPS administrative port left open, HTTPS services on non-standard ports, etc.). Therefore, apply these checks to all SSL-wrapped ports which have been discovered. For example, the nmap scanner features a scanning mode (enabled by the –sV command line switch) which identifies SSL-wrapped services. The Nessus vulnerability scanner has the capability of performing SSL checks on all SSL/TLS-wrapped services.
 +
 +
 +
====Example 7. Testing for certificate validity (manually)====
 +
Rather than providing a fictitious example, this guide includes an anonymized real-life example to stress how frequently one stumbles on https sites whose certificates are inaccurate with respect to naming. The following screenshots refer to a regional site of a high-profile IT company.
 +
 +
We are visiting a .it site and the certificate was issued to a .com site. Internet Explorer warns that the name on the certificate does not match the name of the site.
  
 
[[Image:SSL Certificate Validity Testing IE Warning.gif]]
 
[[Image:SSL Certificate Validity Testing IE Warning.gif]]
  
<u>Warning issued by Mozilla Firefox</u>. The message issued by Firefox is different Firefox complains because it cannot ascertain the identity of the .com site the certificate refers to because it does not know the CA which signed the certificate. In fact, Internet Explorer and Firefox do not come preloaded with the same list of CAs. Therefore, the behavior experienced with various browsers may differ.
+
''Warning issued by Microsoft Internet Explorer''
 +
 
 +
The message issued by Firefox is different. Firefox complains because it cannot ascertain the identity of the .com site the certificate refers to because it does not know the CA which signed the certificate. In fact, Internet Explorer and Firefox do not come pre-loaded with the same list of CAs. Therefore, the behavior experienced with various browsers may differ.
  
 
[[Image:SSL Certificate Validity Testing Firefox Warning.gif]]
 
[[Image:SSL Certificate Validity Testing Firefox Warning.gif]]
 +
 +
''Warning issued by Mozilla Firefox''
 +
  
 
===Testing for other vulnerabilities===
 
===Testing for other vulnerabilities===
As mentioned previously there are other types of vulnerabilities that are not related with the SSL/TLS protocol used or the cipher suite. These vulnerabilities are possible when the server provide the website both with the HTTP and HTTPS protocols, and permit to an attacker to force a victim into using a non-secure channel instead of a secure one.<br>
+
As mentioned previously, there are other types of vulnerabilities that are not related with the SSL/TLS protocol used, the cipher suites or Certificates. Apart from other vulnerabilities discussed in other parts of this guide, a vulnerability exists  when the server provides the website both with the HTTP and HTTPS protocols, and permits an attacker to force a victim into using a non-secure channel instead of a secure one.
 +
 
 +
 
 +
====Surf Jacking====
 +
The Surf Jacking attack [7] was first presented by Sandro Gauci and permits to an attacker to hijack an HTTP session even when the victim’s connection is encrypted using SSL or TLS.
 +
 
  
'''Surf Jacking'''
+
The following is a scenario of how the attack can take place:
Surf Jackin attack [6] was first presented by Sandro Gauci and permits to an attacker to hijack an HTTP session even when the victim’s connection is encrypted using SSL or TLS.<br>
+
The following is a scenario of how the attack can take place:<br>
+
 
* Victim logs into the secure website at https://somesecuresite/.
 
* Victim logs into the secure website at https://somesecuresite/.
 
* The secure site issues a session cookie as the client logs in.
 
* The secure site issues a session cookie as the client logs in.
Line 384: Line 707:
 
* An attacker sitting on the same network is able to see the clear text traffic to http://examplesite.
 
* An attacker sitting on the same network is able to see the clear text traffic to http://examplesite.
 
* The attacker sends back a "301 Moved Permanently" in response to the clear text traffic to http://examplesite. The response contains the header “Location: http://somesecuresite /”, which makes it appear that examplesite is sending the web browser to somesecuresite. Notice that the URL scheme is HTTP not HTTPS.
 
* The attacker sends back a "301 Moved Permanently" in response to the clear text traffic to http://examplesite. The response contains the header “Location: http://somesecuresite /”, which makes it appear that examplesite is sending the web browser to somesecuresite. Notice that the URL scheme is HTTP not HTTPS.
* The victim's browser starts a new clear text connection to http://somesecuresite/ and sends an HTTP request containing cookie in the HTTP header in clear text
+
* The victim's browser starts a new clear text connection to http://somesecuresite/ and sends an HTTP request containing the cookie in the HTTP header in clear text
* The attacker sees this traffic and logs the cookie for later (ab)use.
+
* The attacker sees this traffic and logs the cookie for later use.
To test if a website is vulnerable is sufficient to proceed like follow:
+
 
# Check if website supports both HTTP and HTTPS protocol
+
 
 +
To test if a website is vulnerable carry out the following tests:
 +
# Check if website supports both HTTP and HTTPS protocols
 
# Check if cookies do not have the “Secure” flag
 
# Check if cookies do not have the “Secure” flag
  
<br>
 
== Gray Box testing and example ==
 
<br>
 
  
===Testing for Weak SSL/TSL Ciphers===
+
====SSL Strip====
<br>
+
Some applications supports both HTTP and HTTPS, either for usability or so users can type both addresses and get to the site. Often users go into an HTTPS website from link or a redirect. Typically personal banking sites have a similar configuration with an iframed log in or a form with action attribute over HTTPS but the page under HTTP.
Check the configuration of the web servers which provide https services. If the web application provides other SSL/TLS wrapped services, these should be checked as well. <br>
+
'''Example 1:''' The following registry path in Microsoft Windows Server 2003 and Microsoft Windows Server 2008 defines the ciphers available to the server:
+
<pre>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Ciphers\ </pre>
+
'''Example 2: ''' To check the cipher suites and protocols supported by Apache2 web server open the ''ssl.conf'' file and search for the <code>SSLCipherSuite</code> and <code>SSLProtocol</code> directives.<br>
+
  
===Testing SSL certificate validity – client and server===
 
<br>
 
Examine the validity of the certificates used by the application at both server and client levels. The usage of certificates is primarily at the web server level; however, there may be additional communication paths protected by SSL (for example, towards the DBMS). You should check the application architecture to identify all SSL protected channels.
 
  
<br><br>
+
An attacker in a privileged position - as described in SSL strip [8] - can intercept traffic when the user is in the http site and manipulate it to get a Man-In-The-Middle attack under HTTPS. An application is vulnerable if it supports both HTTP and HTTPS.
  
==References==
 
'''OWASP Resources'''<br>
 
* [[Transport_Layer_Protection_Cheat_Sheet]]
 
  
'''Whitepapers'''<br>
+
===Testing via HTTP proxy===
* [1] RFC5246. The Transport Layer Security (TLS) Protocol Version 1.2 (Updated by RFC 5746, RFC 5878, RFC 6176) - http://www.ietf.org/rfc/rfc5246.txt
+
* [2] RFC2817. Upgrading to TLS Within HTTP/1.1 - http://www.ietf.org/rfc/rfc2817.txt
+
* [3] RFC6066. Transport Layer Security (TLS) Extensions: Extension Definitions - http://www.ietf.org/rfc/rfc6066.txt
+
* [4] https://www.ssllabs.com/projects/best-practices/
+
* [5] https://www.ssllabs.com/projects/rating-guide/index.html
+
* [6] https://resources.enablesecurity.com/resources/Surf%20Jacking.pdf
+
  
 +
Inside corporate environments testers can see services that are not directly accessible and they can access them only via HTTP proxy using the CONNECT method [36]. Most of the tools will not work in this scenario because they try to connect to the desired tcp port to start the SSL/TLS handshake. With the help of relaying software such as socat [37] testers can enable those tools for use with services behind an HTTP proxy.
  
'''Tools'''
 
  
* https://www.ssllabs.com/ssldb/
+
====Example 8. Testing via HTTP proxy====
  
* Vulnerability scanners may include checks regarding certificate validity, including name mismatch and time expiration. They usually report other information as well, such as the CA which issued the certificate. Remember that there is no unified notion of a “trusted CA”; what is trusted depends on the configuration of the software and on the human assumptions made beforehand. Browsers come with a preloaded list of trusted CAs. If your web application relies on a CA which is not in this list (for example, because you rely on a self-made CA), you should take into account the process of configuring user browsers to recognize the CA.
+
To connect to destined.application.lan:443 via proxy 10.13.37.100:3128 run socat as follows:
 +
<pre>
 +
$ socat TCP-LISTEN:9999,reuseaddr,fork PROXY:10.13.37.100:destined.application.lan:443,proxyport=3128
 +
</pre>
  
* The Nessus scanner includes a plugin to check for expired certificates or certificates which are going to expire within 60 days (plugin “SSL certificate expiry”, plugin id 15901). This plugin will check certificates ''installed on the server.
 
  
* Vulnerability scanners may include checks against weak ciphers. For example, the Nessus scanner (http://www.nessus.org) has this capability and flags the presence of SSL weak ciphers (see example provided above).
+
Then the tester can target all other tools to localhost:9999:
 +
<pre>
 +
$ openssl s_client -connect localhost:9999
 +
</pre>
  
* You may also rely on specialized tools such as SSL Digger (http://www.mcafee.com/us/downloads/free-tools/ssldigger.aspx), or – for the command line oriented – experiment with the openssl tool, which provides access to OpenSSL cryptographic functions directly from a Unix shell (may be already available on *nix boxes, otherwise see www.openssl.org).
 
  
* To identify SSL-based services, use a vulnerability scanner or a port scanner with service recognition capabilities. The nmap scanner features a “-sV” scanning option which tries to identify services, while the nessus vulnerability scanner has the capability of identifying SSL-based services on arbitrary ports and to run vulnerability checks on them regardless of whether they are configured on standard or non-standard ports.
+
All connections to localhost:9999 will be effectively relayed by socat via proxy to destined.application.lan:443.
  
* In case you need to talk to a SSL service but your favourite tool doesn’t support SSL, you may benefit from a SSL proxy such as stunnel; stunnel will take care of tunneling the underlying protocol (usually http, but not necessarily so) and communicate with the SSL service you need to reach.
 
  
* ssl_tests, http://www.pentesterscripting.com/discovery/ssl_tests
+
== Gray Box testing and example ==
  
* Finally, a word of advice. Though it may be tempting to use a regular browser to check certificates, there are various reasons for not doing so. Browsers have been plagued by various bugs in this area, and the way the browser will perform the check might be influenced by configuration settings that may not be evident. Instead, rely on vulnerability scanners or on specialized tools to do the job.
+
===Testing for Weak SSL/TLS Cipher Suites===
 +
Check the configuration of the web servers that provide https services. If the web application provides other SSL/TLS wrapped services, these should be checked as well.  
  
* [http://www.owasp.org/index.php/Transport_Layer_Protection_Cheat_Sheet OWASP Transport Layer Protection Cheat Sheet]
+
 
 +
====Example 9. Windows Server====
 +
Check the configuration on a Microsoft Windows Server (2000, 2003 and 2008) using the registry key:
 +
<pre>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\</pre>
 +
that has some sub-keys including Ciphers, Protocols and KeyExchangeAlgorithms.
 +
 
 +
 
 +
====Example 10: Apache====
 +
To check the cipher suites and protocols supported by the Apache2 web server, open the ssl.conf file and search for the SSLCipherSuite, SSLProtocol, SSLHonorCipherOrder,SSLInsecureRenegotiation and SSLCompression directives.
 +
 
 +
 
 +
===Testing SSL certificate validity – client and server===
 +
Examine the validity of the certificates used by the application at both server and client levels. The usage of certificates is primarily at the web server level, however, there may be additional communication paths protected by SSL (for example, towards the DBMS). Testers should check the application architecture to identify all SSL protected channels.
 +
 
 +
 
 +
==References==
 +
'''OWASP Resources'''
 +
* [5] [OWASP Testing Guide - Testing for cookie attributes (OTG-SESS-002)|https://www.owasp.org/index.php/Testing_for_cookies_attributes_(OWASP-SM-002)]
 +
* [4][OWASP Testing Guide - Test Network/Infrastructure Configuration (OTG-CONFIG-001)|https://www.owasp.org/index.php/Testing_for_infrastructure_configuration_management_(OWASP-CM-003)]
 +
* [6] [OWASP Testing |https://www.owasp.org/index.php/Testing_for_cookies_attributes_(OWASP-SM-002)][Guide - Testing for Missing HSTS header (OTG-CONFIG-009)|https://www.owasp.org/index.php/Testing_for_Missing_HSTS_header]
 +
* [2] [OWASP Testing Guide - Testing for Sensitive information sent via unencrypted channels (OTG-CRYPST-007)|https://www.owasp.org/index.php?title=Testing_for_Sensitive_information_sent_via_unencrypted_channels_(OTG-CRYPST-007)&action=edit&redlink=1]
 +
* [3] [OWASP Testing Guide - Testing for Credentials Transported over an Encrypted Channel (OWASP-AT-001)|https://www.owasp.org/index.php/Testing_for_Credentials_Transported_over_an_Encrypted_Channel_(OWASP-AT-001)]
 +
* [9] [OWASP Testing Guide - Test Content Security Policy (OTG-CONFIG-008)|https://www.owasp.org/index.php/Testing_for_Content_Security_Policy_weakness]
 +
* [22] [OWASP Cheat sheet - Transport Layer Protection|https://www.owasp.org/index.php/Transport_Layer_Protection_Cheat_Sheet]
 +
* [23] [OWASP TOP 10 2013 - A6 Sensitive Data Exposure|https://www.owasp.org/index.php/Top_10_2013-A6-Sensitive_Data_Exposure]
 +
* [24] [OWASP TOP 10 2010 - A9 Insufficient Transport Layer Protection|https://www.owasp.org/index.php/Top_10_2010-A9-Insufficient_Transport_Layer_Protection]
 +
* [25] [OWASP ASVS 2009 - Verification 10|https://code.google.com/p/owasp-asvs/wiki/Verification_V10]
 +
* [26] [OWASP Application Security FAQ - Cryptography/SSL|https://www.owasp.org/index.php/OWASP_Application_Security_FAQ#Cryptography.2FSSL]
 +
 
 +
 
 +
'''Whitepapers'''
 +
* [1] [RFC5246 - The Transport Layer Security (TLS) Protocol Version 1.2 (Updated by RFC 5746, RFC 5878, RFC 6176)|http://www.ietf.org/rfc/rfc5246.txt]
 +
* [36] [RFC2817 - Upgrading to TLS Within HTTP/1.1|]
 +
* [34] [RFC6066 - Transport Layer Security (TLS) Extensions: Extension Definitions|http://www.ietf.org/rfc/rfc6066.txt]
 +
* [11] [SSLv2 Protocol Multiple Weaknesses |http://osvdb.org/56387]
 +
* [12] [Mitre - TLS Renegotiation MiTM|http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-3555]
 +
* [13] [Qualys SSL Labs - TLS Renegotiation DoS|https://community.qualys.com/blogs/securitylabs/2011/10/31/tls-renegotiation-and-denial-of-service-attacks]
 +
* [10] [Qualys SSL Labs - SSL/TLS Deployment Best Practices|https://www.ssllabs.com/projects/best-practices/index.html]
 +
* [14] [Qualys SSL Labs - SSL Server Rating Guide|https://www.ssllabs.com/projects/rating-guide/index.html]
 +
* [20] [Qualys SSL Labs - SSL Threat Model|https://www.ssllabs.com/projects/ssl-threat-model/index.html]
 +
* [18] [Qualys SSL Labs - Forward Secrecy|https://community.qualys.com/blogs/securitylabs/2013/06/25/ssl-labs-deploying-forward-secrecy]
 +
* [15] [Qualys SSL Labs - RC4 Usage|https://community.qualys.com/blogs/securitylabs/2013/03/19/rc4-in-tls-is-broken-now-what]
 +
* [16] [Qualys SSL Labs - BEAST|https://community.qualys.com/blogs/securitylabs/2011/10/17/mitigating-the-beast-attack-on-tls]
 +
* [17] [Qualys SSL Labs - CRIME|https://community.qualys.com/blogs/securitylabs/2012/09/14/crime-information-leakage-attack-against-ssltls]
 +
* [7] [SurfJacking attack|https://resources.enablesecurity.com/resources/Surf%20Jacking.pdf]
 +
* [8] [SSLStrip attack|http://www.thoughtcrime.org/software/sslstrip/]
 +
* [19] [PCI-DSS v2.0|https://www.pcisecuritystandards.org/security_standards/documents.php]
 +
* [35] [Xiaoyun Wang, Hongbo Yu: How to Break MD5 and Other Hash Functions| http://link.springer.com/chapter/10.1007/11426639_2]
 +
 
 +
 
 +
'''Tools'''
 +
* [21][Qualys SSL Labs - SSL Server Test|https://www.ssllabs.com/ssltest/index.html]: internet facing scanner
 +
* [27] [Tenable - Nessus Vulnerability Scanner|http://www.tenable.com/products/nessus]: includes some plugins to test different SSL related vulnerabilities, Certificates and the presence of HTTP Basic authentication without SSL.
 +
* [32] [TestSSLServer|http://www.bolet.org/TestSSLServer/]: a java scanner - and also windows executable - includes tests for cipher suites, CRIME and BEAST
 +
* [33] [sslyze|https://github.com/iSECPartners/sslyze]: is a python script to check vulnerabilities in SSL/TLS.
 +
* [28] [SSLAudit|https://code.google.com/p/sslaudit/]: a perl script/windows executable scanner which follows Qualys SSL Labs Rating Guide.
 +
* [29] [SSLScan|http://sourceforge.net/projects/sslscan/] with [SSL Tests|http://www.pentesterscripting.com/discovery/ssl_tests]: a SSL Scanner and a wrapper in order to enumerate SSL vulnerabilities.
 +
* [31] [nmap|http://nmap.org/]: can be used primary to identify SSL-based services and then to check Certificate and SSL/TLS vulnerabilities. In particular it has some scripts to check [Certificate and SSLv2|http://nmap.org/nsedoc/scripts/ssl-cert.html] and supported [SSL/TLS protocols/ciphers|http://nmap.org/nsedoc/scripts/ssl-enum-ciphers.html] with an internal rating.
 +
* [30] [curl|http://curl.haxx.se/] and [openssl|http://www.openssl.org/]: can be used to query manually SSL/TLS services
 +
* [9] [Stunnel|http://www.stunnel.org]: a noteworthy class of SSL clients is that of SSL proxies such as stunnel available at which can be used to allow non-SSL enabled tools to talk to SSL services)
 +
* [37] [socat| http://www.dest-unreach.org/socat/]: Multipurpose relay
 +
* [38] [testssl.sh| https://testssl.sh/ ]
 +
   
  
 
[[Category:Cryptographic Vulnerability]]
 
[[Category:Cryptographic Vulnerability]]
 
[[Category:SSL]]
 
[[Category:SSL]]

Latest revision as of 13:42, 17 May 2014

This article is part of the new OWASP Testing Guide v4. 
At the moment the project is in the REVIEW phase.

Back to the OWASP Testing Guide v4 ToC: https://www.owasp.org/index.php/OWASP_Testing_Guide_v4_Table_of_Contents Back to the OWASP Testing Guide Project: http://www.owasp.org/index.php/OWASP_Testing_Project

Contents


Brief Summary

Sensitive data must be protected when it is transmitted through the network. Such data can include user credentials and credit cards. As a rule of thumb, if data must be protected when it is stored, it must be protected also during transmission.


HTTP is a clear-text protocol and it is normally secured via an SSL/TLS tunnel, resulting in HTTPS traffic [1]. The use of this protocol ensures not only confidentiality, but also authentication. Servers are authenticated using digital certificates and it is also possible to use client certificate for mutual authentication.


Even if high grade ciphers are today supported and normally used, some misconfiguration in the server can be used to force the use of a weak cipher - or at worst no encryption - permitting to an attacker to gain access to the supposed secure communication channel. Other misconfiguration can be used for a Denial of Service attack.


Description of the Issue

A vulnerability occurs if the HTTP protocol is used to transmit sensitive information [2] (e.g. credentials transmitted over HTTP [3]).

When the SSL/TLS service is present it is good but it increments the attack surface and the following vulnerabilities exist:

  • SSL/TLS protocols, ciphers, keys and renegotiation must be properly configured.
  • Certificate validity must be ensured.

Other vulnerabilities linked to this are:

  • Software exposed must be updated due to possibility of known vulnerabilities [4].
  • Usage of Secure flag for Session Cookies [5].
  • Usage of HTTP Strict Transport Security (HSTS) [6].
  • The presence of HTTP and HTTPS both, which can be used to intercept traffic [7], [8].
  • The presence of mixed HTTPS and HTTP content in the same page, which can be used to Leak information.


Sensitive data transmitted in clear-text

The application should not transmit sensitive information via unencrypted channels. Typically it is possible to find basic authentication over HTTP, input password or session cookie sent via HTTP and, in general, other information considered by regulations, laws or organization policy.


Weak SSL/TLS Ciphers/Protocols/Keys

Historically, there have been limitations set in place by the U.S. government to allow cryptosystems to be exported only for key sizes of at most 40 bits, a key length which could be broken and would allow the decryption of communications. Since then cryptographic export regulations have been relaxed the maximum key size is 128 bits.


It is important to check the SSL configuration being used to avoid putting in place cryptographic support which could be easily defeated. To reach this goal SSL-based services should not offer the possibility to choose weak cipher suite. A cipher suite is specified by an encryption protocol (e.g. DES, RC4, AES), the encryption key length (e.g. 40, 56, or 128 bits), and a hash algorithm (e.g. SHA, MD5) used for integrity checking.


Briefly, the key points for the cipher suite determination are the following:

  1. The client sends to the server a ClientHello message specifying, among other information, the protocol and the cipher suites that it is able to handle. Note that a client is usually a web browser (most popular SSL client nowadays), but not necessarily, since it can be any SSL-enabled application; the same holds for the server, which needs not to be a web server, though this is the most common case [9].
  2. The server responds with a ServerHello message, containing the chosen protocol and cipher suite that will be used for that session (in general the server selects the strongest protocol and cipher suite supported by both the client and server).


It is possible (for example, by means of configuration directives) to specify which cipher suites the server will honor. In this way you may control whether or not conversations with clients will support 40-bit encryption only.

  1. The server sends its Certificate message and, if client authentication is required, also sends a CertificateRequest message to the client.
  2. The server sends a ServerHelloDone message and waits for a client response.
  3. Upon receipt of the ServerHelloDone message, the client verifies the validity of the server's digital certificate.


SSL certificate validity – client and server

When accessing a web application via the HTTPS protocol, a secure channel is established between the client and the server. The identity of one (the server) or both parties (client and server) is then established by means of digital certificates. So, once the cipher suite is determined, the “SSL Handshake” continues with the exchange of the certificates:

  1.  The server sends its Certificate message and, if client authentication is required, also sends a CertificateRequest message to the client.
  2.  The server sends a ServerHelloDone message and waits for a client response.
  3.  Upon receipt of the ServerHelloDone message, the client verifies the validity of the server's digital certificate.


In order for the communication to be set up, a number of checks on the certificates must be passed. While discussing SSL and certificate based authentication is beyond the scope of this guide, this section will focus on the main criteria involved in ascertaining certificate validity:

  • Checking if the Certificate Authority (CA) is a known one (meaning one considered trusted);
  • Checking that the certificate is currently valid;
  • Checking that the name of the site and the name reported in the certificate match.


Let's examine each check more in detail.

  • Each browser comes with a pre-loaded list of trusted CAs, against which the certificate signing CA is compared (this list can be customized and expanded at will). During the initial negotiations with an HTTPS server, if the server certificate relates to a CA unknown to the browser, a warning is usually raised. This happens most often because a web application relies on a certificate signed by a self-established CA. Whether this is to be considered a concern depends on several factors. For example, this may be fine for an Intranet environment (think of corporate web email being provided via HTTPS; here, obviously all users recognize the internal CA as a trusted CA). When a service is provided to the general public via the Internet, however (i.e. when it is important to positively verify the identity of the server we are talking to), it is usually imperative to rely on a trusted CA, one which is recognized by all the user base (and here we stop with our considerations; we won’t delve deeper in the implications of the trust model being used by digital certificates).


  • Certificates have an associated period of validity, therefore they may expire. Again, we are warned by the browser about this. A public service needs a temporally valid certificate; otherwise, it means we are talking with a server whose certificate was issued by someone we trust, but has expired without being renewed.


  • What if the name on the certificate and the name of the server do not match? If this happens, it might sound suspicious. For a number of reasons, this is not so rare to see. A system may host a number of name-based virtual hosts, which share the same IP address and are identified by means of the HTTP 1.1 Host: header information. In this case, since the SSL handshake checks the server certificate before the HTTP request is processed, it is not possible to assign different certificates to each virtual server. Therefore, if the name of the site and the name reported in the certificate do not match, we have a condition which is typically signaled by the browser. To avoid this, IP-based virtual servers must be used. [33] and [34] describe techniques to deal with this problem and allow name-based virtual hosts to be correctly referenced.


Other vulnerabilities

The presence of a new service, listening in a separate tcp port may introduce vulnerabilities such as infrastructure vulnerabilities if the software is not up to date [4]. Furthermore, for the correct protection of data during transmission the Session Cookie must use the Secure flag [5] and some directives should be sent to the browser to accept only secure traffic (e.g. HSTS [6], CSP [9]).


Also there are some attacks that can be used to intercept traffic if the web server exposes the application on both HTTP and HTTPS [6], [7] or in case of mixed HTTP and HTTPS resources in the same page.


Black Box Testing

Testing for sensitive data transmitted in clear-text

Various types of information which must be protected can be also transmitted in clear text. It is possible to check if this information is transmitted over HTTP instead of HTTPS. Please refer to specific tests for full details, for credentials [3] and other kind of data [2].


Example 1. Basic Authentication over HTTP

A typical example is the usage of Basic Authentication over HTTP because with Basic Authentication, after log in, credentials are encoded - and not encrypted - into HTTP Headers.

$ curl -kis http://example.com/restricted/
HTTP/1.1 401 Authorization Required
Date: Fri, 01 Aug 2013 00:00:00 GMT
WWW-Authenticate: Basic realm="Restricted Area"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Length: 162
Content-Type: text/html

<html><head><title>401 Authorization Required</title></head>
<body bgcolor=white>
<h1>401 Authorization Required</h1>

Invalid login credentials!

</body></html>


Testing for Weak SSL/TLS Ciphers/Protocols/Keys vulnerabilities

The large number of available cipher suites and quick progress in cryptanalysis makes testing an SSL server a non-trivial task.

At the time of writing these criteria are widely recognized as minimum checklist:

  • Weak ciphers must not be used (e.g. less than 128 bits [10]; no NULL ciphers suite, due to no encryption used; no Anonymous Diffie-Hellmann, due to not provides authentication).
  • Weak protocols must be disabled (e.g. SSLv2 must be disabled, due to known weaknesses in protocol design [11]).
  • Renegotiation must be properly configured (e.g. Insecure Renegotiation must be disabled, due to MiTM attacks [12] and Client-initiated Renegotiation must be disabled, due to Denial of Service vulnerability [13]).
  • No Export (EXP) level cipher suites, due to can be easly broken [10].
  • X.509 certificates key length must be strong (e.g. if RSA or DSA is used the key must be at least 1024 bits).
  • X.509 certificates must be signed only with secure hashing algoritms (e.g. not signed using MD5 hash, due to known collision attacks on this hash).
  • Keys must be generated with proper entropy (e.g, Weak Key Generated with Debian) [14].

A more complete checklist includes:

  • Secure Renegotiation should be enabled.
  • MD5 should not be used, due to known collision attacks. [35]
  • RC4 should not be used, due to crypto-analytical attacks [15].
  • Server should be protected from BEAST Attack [16].
  • Server should be protected from CRIME attack, TLS compression must be disabled [17].
  • Server should support Forward Secrecy [18].


The following standards can be used as reference while assessing SSL servers:

  • PCI-DSS v2.0 in point 4.1 requires compliant parties to use "strong cryptography" without precisely defining key lengths and algorithms. Common interpretation, partially based on previous versions of the standard, is that at least 128 bit key cipher, no export strength algorithms and no SSLv2 should be used [19].
  • Qualys SSL Labs Server Rating Guide [14], Depoloyment best practice [10] and SSL Threat Model [20] has been proposed to standardize SSL server assessment and configuration. But is less updated than the SSL Server tool [21].
  • OWASP has a lot of resources about SSL/TLS Security [22], [23], [24], [25]. [26].


Some tools and scanners both free (e.g. SSLAudit [28] or SSLScan [29]) and commercial (e.g. Tenable Nessus [27]), can be used to assess SSL/TLS vulnerabilities. But due to evolution of these vulnerabilities a good way to test is to check them manually with openssl [30] or use the tool’s output as an input for manual evaluation using the references.


Sometimes the SSL/TLS enabled service is not directly accessible and the tester can access it only via a HTTP proxy using CONNECT method [36]. Most of the tools will try to connect to desired tcp port to start SSL/TLS handshake. This will not work since desired port is accessible only via HTTP proxy. The tester can easily circumvent this by using relaying software such as socat [37].


Example 2. SSL service recognition via nmap

The first step is to identify ports which have SSL/TLS wrapped services. Typically tcp ports with SSL for web and mail services are - but not limited to - 443 (https), 465 (ssmtp), 585 (imap4-ssl), 993 (imaps), 995 (ssl-pop).

In this example we search for SSL services using nmap with “-sV” option, used to identify services and it is also able to identify SSL services [31]. Other options are for this particular example and must be customized. Often in a Web Application Penetration Test scope is limited to port 80 and 443.

$ nmap -sV --reason -PN -n --top-ports 100 www.example.com
Starting Nmap 6.25 ( http://nmap.org ) at 2013-01-01 00:00 CEST
Nmap scan report for www.example.com (127.0.0.1)
Host is up, received user-set (0.20s latency).
Not shown: 89 filtered ports
Reason: 89 no-responses
PORT    STATE SERVICE  REASON  VERSION
21/tcp  open  ftp      syn-ack Pure-FTPd
22/tcp  open  ssh      syn-ack OpenSSH 5.3 (protocol 2.0)
25/tcp  open  smtp     syn-ack Exim smtpd 4.80
26/tcp  open  smtp     syn-ack Exim smtpd 4.80
80/tcp  open  http     syn-ack
110/tcp open  pop3     syn-ack Dovecot pop3d
143/tcp open  imap     syn-ack Dovecot imapd
443/tcp open  ssl/http syn-ack Apache
465/tcp open  ssl/smtp syn-ack Exim smtpd 4.80
993/tcp open  ssl/imap syn-ack Dovecot imapd
995/tcp open  ssl/pop3 syn-ack Dovecot pop3d
Service Info: Hosts: example.com
Service detection performed. Please report any incorrect results at http://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 131.38 seconds


Example 3. Checking for Certificate information, Weak Ciphers and SSLv2 via nmap

Nmap has two scripts for checking Certificate information, Weak Ciphers and SSLv2 [31].

$ nmap --script ssl-cert,ssl-enum-ciphers -p 443,465,993,995 www.example.com
Starting Nmap 6.25 ( http://nmap.org ) at 2013-01-01 00:00 CEST
Nmap scan report for www.example.com (127.0.0.1)
Host is up (0.090s latency).
rDNS record for 127.0.0.1: www.example.com
PORT    STATE SERVICE
443/tcp open  https
| ssl-cert: Subject: commonName=www.example.org
| Issuer: commonName=*******
| Public Key type: rsa
| Public Key bits: 1024
| Not valid before: 2010-01-23T00:00:00+00:00
| Not valid after:  2020-02-28T23:59:59+00:00
| MD5:   *******
|_SHA-1: *******
| ssl-enum-ciphers: 
|   SSLv3: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|   TLSv1.0: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|_  least strength: strong
465/tcp open  smtps
| ssl-cert: Subject: commonName=*.exapmple.com
| Issuer: commonName=*******
| Public Key type: rsa
| Public Key bits: 2048
| Not valid before: 2010-01-23T00:00:00+00:00
| Not valid after:  2020-02-28T23:59:59+00:00
| MD5:   *******
|_SHA-1: *******
| ssl-enum-ciphers: 
|   SSLv3: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|   TLSv1.0: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|_  least strength: strong
993/tcp open  imaps
| ssl-cert: Subject: commonName=*.exapmple.com
| Issuer: commonName=*******
| Public Key type: rsa
| Public Key bits: 2048
| Not valid before: 2010-01-23T00:00:00+00:00
| Not valid after:  2020-02-28T23:59:59+00:00
| MD5:   *******
|_SHA-1: *******
| ssl-enum-ciphers: 
|   SSLv3: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|   TLSv1.0: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|_  least strength: strong
995/tcp open  pop3s
| ssl-cert: Subject: commonName=*.exapmple.com
| Issuer: commonName=*******
| Public Key type: rsa
| Public Key bits: 2048
| Not valid before: 2010-01-23T00:00:00+00:00
| Not valid after:  2020-02-28T23:59:59+00:00
| MD5:   *******
|_SHA-1: *******
| ssl-enum-ciphers: 
|   SSLv3: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|   TLSv1.0: 
|     ciphers: 
|       TLS_RSA_WITH_CAMELLIA_128_CBC_SHA - strong
|       TLS_RSA_WITH_CAMELLIA_256_CBC_SHA - strong
|       TLS_RSA_WITH_RC4_128_SHA - strong
|     compressors: 
|       NULL
|_  least strength: strong
Nmap done: 1 IP address (1 host up) scanned in 8.64 seconds


Example 4 Checking for Client-initiated Renegotiation and Secure Renegotiation via openssl (manually)

Openssl [30] can be used for testing manually SSL/TLS. In this example the tester tries to initiate a renegotiation by client [m] connecting to server with openssl. The tester then writes the fist line of an HTTP request and types “R” in a new line. He then waits for renegotiaion and completion of the HTTP request and checks if secure renegotiaion is supported by looking at the server output. Using manual requests it is also possible to see if Compression is enabled for TLS and to check for CRIME [13], for ciphers and for other vulnerabilities.

$ openssl s_client -connect www2.example.com:443
CONNECTED(00000003)
depth=2 ******
verify error:num=20:unable to get local issuer certificate
verify return:0
---
Certificate chain
 0 s:******
   i:******
 1 s:******
   i:******
 2 s:******
   i:******
---
Server certificate
-----BEGIN CERTIFICATE-----
******
-----END CERTIFICATE-----
subject=******
issuer=******
---
No client certificate CA names sent
---
SSL handshake has read 3558 bytes and written 640 bytes
---
New, TLSv1/SSLv3, Cipher is DES-CBC3-SHA
Server public key is 2048 bit
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : TLSv1
    Cipher    : DES-CBC3-SHA
    Session-ID: ******
    Session-ID-ctx: 
    Master-Key: ******
    Key-Arg   : None
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    Start Time: ******
    Timeout   : 300 (sec)
    Verify return code: 20 (unable to get local issuer certificate)
---


Now the tester can write the first line of an HTTP request and then R in a new line.

HEAD / HTTP/1.1
R

Server is renegotiating

RENEGOTIATING
depth=2 C******
verify error:num=20:unable to get local issuer certificate
verify return:0

And the tester can complete our request, checking for response.

HEAD / HTTP/1.1

HTTP/1.1 403 Forbidden ( The server denies the specified Uniform Resource Locator (URL). Contact the server administrator.  )
Connection: close
Pragma: no-cache
Cache-Control: no-cache
Content-Type: text/html
Content-Length: 1792  

read:errno=0

Even if the HEAD is not permitted, Client-intiated renegotiaion is permitted.


Example 5. Testing supported Cipher Suites, BEAST and CRIME attacks via TestSSLServer

TestSSLServer [32] is a script which permits the tester to check the cipher suite and also for BEAST and CRIME attacks. BEAST (Browser Exploit Against SSL/TLS) exploits a vulnerability of CBC in TLS 1.0. CRIME (Compression Ratio Info-leak Made Easy) exploits a vulnerability of TLS Compression, that should be disabled. What is interesting is that the first fix for BEAST was the use of RC4, but this is now discouraged due to a crypto-analytical attack to RC4 [15].


An online tool to check for these attacks is SSL Labs, but can be used only for internet facing servers. Also consider that target data will be stored on SSL Labs server and also will result some connection from SSL Labs server [21].

$ java -jar TestSSLServer.jar www3.example.com 443
Supported versions: SSLv3 TLSv1.0 TLSv1.1 TLSv1.2
Deflate compression: no
Supported cipher suites (ORDER IS NOT SIGNIFICANT):
  SSLv3
     RSA_WITH_RC4_128_SHA
     RSA_WITH_3DES_EDE_CBC_SHA
     DHE_RSA_WITH_3DES_EDE_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA
     RSA_WITH_AES_256_CBC_SHA
     DHE_RSA_WITH_AES_256_CBC_SHA
     RSA_WITH_CAMELLIA_128_CBC_SHA
     DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
     RSA_WITH_CAMELLIA_256_CBC_SHA
     DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
     TLS_RSA_WITH_SEED_CBC_SHA
     TLS_DHE_RSA_WITH_SEED_CBC_SHA
  (TLSv1.0: idem)
  (TLSv1.1: idem)
  TLSv1.2
     RSA_WITH_RC4_128_SHA
     RSA_WITH_3DES_EDE_CBC_SHA
     DHE_RSA_WITH_3DES_EDE_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA
     RSA_WITH_AES_256_CBC_SHA
     DHE_RSA_WITH_AES_256_CBC_SHA
     RSA_WITH_AES_128_CBC_SHA256
     RSA_WITH_AES_256_CBC_SHA256
     RSA_WITH_CAMELLIA_128_CBC_SHA
     DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
     DHE_RSA_WITH_AES_128_CBC_SHA256
     DHE_RSA_WITH_AES_256_CBC_SHA256
     RSA_WITH_CAMELLIA_256_CBC_SHA
     DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
     TLS_RSA_WITH_SEED_CBC_SHA
     TLS_DHE_RSA_WITH_SEED_CBC_SHA
     TLS_RSA_WITH_AES_128_GCM_SHA256
     TLS_RSA_WITH_AES_256_GCM_SHA384
     TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
     TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
----------------------
Server certificate(s):
  ******
----------------------
Minimal encryption strength:     strong encryption (96-bit or more)
Achievable encryption strength:  strong encryption (96-bit or more)
BEAST status: vulnerable
CRIME status: protected


Example 6. Testing SSL/TLS vulnerabilities with sslyze

Sslyze [33] is a python script which permits mass scanning and XML output. The following is an example of a regular scan. It is one of the most complete and versatile tools for SSL/TLS testing.

./sslyze.py --regular example.com:443

 REGISTERING AVAILABLE PLUGINS
 -----------------------------

  PluginHSTS
  PluginSessionRenegotiation
  PluginCertInfo
  PluginSessionResumption
  PluginOpenSSLCipherSuites
  PluginCompression



 CHECKING HOST(S) AVAILABILITY
 -----------------------------

  example.com:443                      => 127.0.0.1:443



 SCAN RESULTS FOR EXAMPLE.COM:443 - 127.0.0.1:443
 ---------------------------------------------------

  * Compression :
        Compression Support:      Disabled

  * Session Renegotiation :
      Client-initiated Renegotiations:    Rejected
      Secure Renegotiation:               Supported

  * Certificate :
      Validation w/ Mozilla's CA Store:  Certificate is NOT Trusted: unable to get local issuer certificate
      Hostname Validation:               MISMATCH                           
      SHA1 Fingerprint:                  ******

      Common Name:                       www.example.com                     
      Issuer:                            ******
      Serial Number:                     ****                               
      Not Before:                        Sep 26 00:00:00 2010 GMT           
      Not After:                         Sep 26 23:59:59 2020 GMT   
       
      Signature Algorithm:               sha1WithRSAEncryption              
      Key Size:                          1024 bit                           
      X509v3 Subject Alternative Name:   {'othername': ['<unsupported>'], 'DNS': ['www.example.com']}

  * OCSP Stapling :
      Server did not send back an OCSP response.                                   

  * Session Resumption :
      With Session IDs:           Supported (5 successful, 0 failed, 0 errors, 5 total attempts).
      With TLS Session Tickets:   Supported

  * SSLV2 Cipher Suites :

      Rejected Cipher Suite(s): Hidden 

      Preferred Cipher Suite: None     

      Accepted Cipher Suite(s): None   

      Undefined - An unexpected error happened: None 

  * SSLV3 Cipher Suites :

      Rejected Cipher Suite(s): Hidden 

      Preferred Cipher Suite:          
        RC4-SHA                       128 bits      HTTP 200 OK                        

      Accepted Cipher Suite(s):        
        CAMELLIA256-SHA               256 bits      HTTP 200 OK                        
        RC4-SHA                       128 bits      HTTP 200 OK                        
        CAMELLIA128-SHA               128 bits      HTTP 200 OK                        

      Undefined - An unexpected error happened: None 

  * TLSV1_1 Cipher Suites :

      Rejected Cipher Suite(s): Hidden 

      Preferred Cipher Suite: None     

      Accepted Cipher Suite(s): None   

      Undefined - An unexpected error happened: 
        ECDH-RSA-AES256-SHA             socket.timeout - timed out         
        ECDH-ECDSA-AES256-SHA           socket.timeout - timed out         

  * TLSV1_2 Cipher Suites :

      Rejected Cipher Suite(s): Hidden 

      Preferred Cipher Suite: None     

      Accepted Cipher Suite(s): None   

      Undefined - An unexpected error happened: 
        ECDH-RSA-AES256-GCM-SHA384      socket.timeout - timed out         
        ECDH-ECDSA-AES256-GCM-SHA384    socket.timeout - timed out         

  * TLSV1 Cipher Suites :

      Rejected Cipher Suite(s): Hidden 

      Preferred Cipher Suite:          
        RC4-SHA                       128 bits      Timeout on HTTP GET                

      Accepted Cipher Suite(s):        
        CAMELLIA256-SHA               256 bits      HTTP 200 OK                        
        RC4-SHA                       128 bits      HTTP 200 OK                        
        CAMELLIA128-SHA               128 bits      HTTP 200 OK                        

      Undefined - An unexpected error happened: 
        ADH-CAMELLIA256-SHA             socket.timeout - timed out         



 SCAN COMPLETED IN 9.68 S
 ------------------------


Example 7. Testing SSL/TLS with testssl.sh

Testssl.sh [38] is a Linux shell script which provides clear output to facilitate good decision making. It can not only check web servers but also services on other ports, supports STARTTLS, SNI, SPDY and does a few check on the HTTP header as well.


It's a very easy to use tool. Here's some sample output (without colors):

user@myhost: % testssl.sh owasp.org      

########################################################
testssl.sh v2.0rc3  (https://testssl.sh)
($Id: testssl.sh,v 1.97 2014/04/15 21:54:29 dirkw Exp $)

   This program is free software. Redistribution + 
   modification under GPLv2 is permitted. 
   USAGE w/o ANY WARRANTY. USE IT AT YOUR OWN RISK!

 Note you can only check the server against what is
 available (ciphers/protocols) locally on your machine
########################################################

Using "OpenSSL 1.0.2-beta1 24 Feb 2014" on
      "myhost:/<mypath>/bin/openssl64"


Testing now (2014-04-17 15:06) ---> owasp.org:443 <---
("owasp.org" resolves to "192.237.166.62 / 2001:4801:7821:77:cd2c:d9de:ff10:170e") 


--> Testing Protocols
 
 SSLv2     NOT offered (ok) 
 SSLv3     offered 
 TLSv1     offered (ok) 
 TLSv1.1   offered (ok) 
 TLSv1.2   offered (ok) 

 SPDY/NPN  not offered

--> Testing standard cipher lists
 
 Null Cipher              NOT offered (ok) 
 Anonymous NULL Cipher    NOT offered (ok) 
 Anonymous DH Cipher      NOT offered (ok) 
 40 Bit encryption        NOT offered (ok) 
 56 Bit encryption        NOT offered (ok) 
 Export Cipher (general)  NOT offered (ok) 
 Low (<=64 Bit)           NOT offered (ok) 
 DES Cipher               NOT offered (ok) 
 Triple DES Cipher        offered
 Medium grade encryption  offered
 High grade encryption    offered (ok) 

--> Testing server defaults (Server Hello)
 
 Negotiated protocol       TLSv1.2 
 Negotiated cipher         AES128-GCM-SHA256 
 
 Server key size           2048 bit
 TLS server extensions:    server name, renegotiation info, session ticket, heartbeat
 Session Tickets RFC 5077  300 seconds

--> Testing specific vulnerabilities
 
 Heartbleed (CVE-2014-0160), experimental  NOT vulnerable (ok) 
 Renegotiation (CVE 2009-3555)             NOT vulnerable (ok) 
 CRIME, TLS (CVE-2012-4929)                NOT vulnerable (ok)  

--> Checking RC4 Ciphers 

RC4 seems generally available. Now testing specific ciphers...
 
 Hexcode    Cipher Name                   KeyExch.  Encryption Bits
--------------------------------------------------------------------
 [0x05]     RC4-SHA                       RSA         RC4      128

RC4 is kind of broken, for e.g. IE6 consider 0x13 or 0x0a

--> Testing HTTP Header response 
 
 HSTS        no 
 Server      Apache
 Application (None)
 
--> Testing (Perfect) Forward Secrecy  (P)FS) 

no PFS available 

Done now (2014-04-17 15:07) ---> owasp.org:443 <---

user@myhost: %    



STARTTLS would be tested via testssl.sh -t smtp.gmail.com:587 smtp, each ciphers with testssl -e <target>, each ciphers per protocol with testssl -E <target>. To just display what local ciphers that are installed for openssl see testssl -V. For a thorough check it is best to dump the supplied OpenSSL binaries in the path or the one of testssl.sh.


The interesting thing is if a tester looks at the sources they learn how features are tested, see e.g. Example 4. What is even better is that it does the whole handshake for heartbleed in pure /bin/bash with /dev/tcp sockets -- no piggyback perl/python/you name it.


Additionally it provides a prototype (via "testssl.sh -V") of mapping to RFC cipher suite names to OpenSSL ones. The tester needs the file mapping-rfc.txt in same directory.


Testing SSL certificate validity – client and server

Firstly upgrade the browser because CA certs expire and in every release of the browser these are renewed. Examine the validity of the certificates used by the application. Browsers will issue a warning when encountering expired certificates, certificates issued by untrusted CAs, and certificates which do not match name wise with the site to which they should refer.


By clicking on the padlock that appears in the browser window when visiting an HTTPS site, testers can look at information related to the certificate – including the issuer, period of validity, encryption characteristics, etc. If the application requires a client certificate, that tester has probably installed one to access it. Certificate information is available in the browser by inspecting the relevant certificate(s) in the list of the installed certificates.


These checks must be applied to all visible SSL-wrapped communication channels used by the application. Though this is the usual https service running on port 443, there may be additional services involved depending on the web application architecture and on deployment issues (an HTTPS administrative port left open, HTTPS services on non-standard ports, etc.). Therefore, apply these checks to all SSL-wrapped ports which have been discovered. For example, the nmap scanner features a scanning mode (enabled by the –sV command line switch) which identifies SSL-wrapped services. The Nessus vulnerability scanner has the capability of performing SSL checks on all SSL/TLS-wrapped services.


Example 7. Testing for certificate validity (manually)

Rather than providing a fictitious example, this guide includes an anonymized real-life example to stress how frequently one stumbles on https sites whose certificates are inaccurate with respect to naming. The following screenshots refer to a regional site of a high-profile IT company.

We are visiting a .it site and the certificate was issued to a .com site. Internet Explorer warns that the name on the certificate does not match the name of the site.

SSL Certificate Validity Testing IE Warning.gif

Warning issued by Microsoft Internet Explorer

The message issued by Firefox is different. Firefox complains because it cannot ascertain the identity of the .com site the certificate refers to because it does not know the CA which signed the certificate. In fact, Internet Explorer and Firefox do not come pre-loaded with the same list of CAs. Therefore, the behavior experienced with various browsers may differ.

SSL Certificate Validity Testing Firefox Warning.gif

Warning issued by Mozilla Firefox


Testing for other vulnerabilities

As mentioned previously, there are other types of vulnerabilities that are not related with the SSL/TLS protocol used, the cipher suites or Certificates. Apart from other vulnerabilities discussed in other parts of this guide, a vulnerability exists when the server provides the website both with the HTTP and HTTPS protocols, and permits an attacker to force a victim into using a non-secure channel instead of a secure one.


Surf Jacking

The Surf Jacking attack [7] was first presented by Sandro Gauci and permits to an attacker to hijack an HTTP session even when the victim’s connection is encrypted using SSL or TLS.


The following is a scenario of how the attack can take place:

  • Victim logs into the secure website at https://somesecuresite/.
  • The secure site issues a session cookie as the client logs in.
  • While logged in, the victim opens a new browser window and goes to http:// examplesite/
  • An attacker sitting on the same network is able to see the clear text traffic to http://examplesite.
  • The attacker sends back a "301 Moved Permanently" in response to the clear text traffic to http://examplesite. The response contains the header “Location: http://somesecuresite /”, which makes it appear that examplesite is sending the web browser to somesecuresite. Notice that the URL scheme is HTTP not HTTPS.
  • The victim's browser starts a new clear text connection to http://somesecuresite/ and sends an HTTP request containing the cookie in the HTTP header in clear text
  • The attacker sees this traffic and logs the cookie for later use.


To test if a website is vulnerable carry out the following tests:

  1. Check if website supports both HTTP and HTTPS protocols
  2. Check if cookies do not have the “Secure” flag


SSL Strip

Some applications supports both HTTP and HTTPS, either for usability or so users can type both addresses and get to the site. Often users go into an HTTPS website from link or a redirect. Typically personal banking sites have a similar configuration with an iframed log in or a form with action attribute over HTTPS but the page under HTTP.


An attacker in a privileged position - as described in SSL strip [8] - can intercept traffic when the user is in the http site and manipulate it to get a Man-In-The-Middle attack under HTTPS. An application is vulnerable if it supports both HTTP and HTTPS.


Testing via HTTP proxy

Inside corporate environments testers can see services that are not directly accessible and they can access them only via HTTP proxy using the CONNECT method [36]. Most of the tools will not work in this scenario because they try to connect to the desired tcp port to start the SSL/TLS handshake. With the help of relaying software such as socat [37] testers can enable those tools for use with services behind an HTTP proxy.


Example 8. Testing via HTTP proxy

To connect to destined.application.lan:443 via proxy 10.13.37.100:3128 run socat as follows:

$ socat TCP-LISTEN:9999,reuseaddr,fork PROXY:10.13.37.100:destined.application.lan:443,proxyport=3128


Then the tester can target all other tools to localhost:9999:

$ openssl s_client -connect localhost:9999


All connections to localhost:9999 will be effectively relayed by socat via proxy to destined.application.lan:443.


Gray Box testing and example

Testing for Weak SSL/TLS Cipher Suites

Check the configuration of the web servers that provide https services. If the web application provides other SSL/TLS wrapped services, these should be checked as well.


Example 9. Windows Server

Check the configuration on a Microsoft Windows Server (2000, 2003 and 2008) using the registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\

that has some sub-keys including Ciphers, Protocols and KeyExchangeAlgorithms.


Example 10: Apache

To check the cipher suites and protocols supported by the Apache2 web server, open the ssl.conf file and search for the SSLCipherSuite, SSLProtocol, SSLHonorCipherOrder,SSLInsecureRenegotiation and SSLCompression directives.


Testing SSL certificate validity – client and server

Examine the validity of the certificates used by the application at both server and client levels. The usage of certificates is primarily at the web server level, however, there may be additional communication paths protected by SSL (for example, towards the DBMS). Testers should check the application architecture to identify all SSL protected channels.


References

OWASP Resources


Whitepapers


Tools