Testing for Sensitive information sent via unencrypted channels (OTG-CRYPST-007)

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This article is part of the new OWASP Testing Guide v4. 
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Brief Summary

Sensitive data must be protected when it is transmitted through the network. If data is transmitted over HTTPS or encrypted in another way the protection mechanism must not have limitations or vulnerabilities, as explained in the broader article Testing for Weak SSL/TSL Ciphers, Insufficient Transport Layer Protection (OWASP-EN-002) [1] and in other OWASP documentation [2], [3], [4], [5].

As a rule of thumb if data must be protected when it is stored, this data must also be protected during transmission. Some examples for sensitive data are:

  • Information used in authentication (e.g. Credentials, PINs, Session identifiers, Tokens, Cookies…)
  • Information protected by laws, regulations or specific organizational policy (e.g. Credit Cards, Customers data)

Description of the Issue

If the application transmits sensitive information via unencrypted channels - e.g. HTTP - it is considered a security risk. Some examples are Basic authentication which sends authentication credentials in plain-text over HTTP, form based authentication credentials sent via HTTP, or plain-text transmission of any other information considered sensitive due to regulations, laws, organizational policy or application business logic.

Black Box testing and examples

Various types of information that must be protected, could be transmitted by the application in clear text. It is possible to check if this information is transmitted over HTTP instead of HTTPS, or whether weak cyphers are used. See more information about insecure transmission of credentials Top 10 2013-A6-Sensitive Data Exposure [3] or insufficient transport layer protection in general Top 10 2010-A9-Insufficient Transport Layer Protection [2].

Example 1: Basic Authentication over HTTP

A typical example is the usage of Basic Authentication over HTTP. When using Basic Authentication, user credentials are encoded rather than encrypted, and are sent as HTTP headers. In the example below the tester uses curl [5] to test for this issue. Note how the application uses Basic authentication, and HTTP rather than HTTPS

$ 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>

Example 2: Form-Based Authentication Performed over HTTP

Another typical example is authentication forms which transmit user authentication credentials over HTTP. In the example below one can see HTTP being used in the "action" attribute of the form. It is also possible to see this issue by examining the HTTP traffic with an interception proxy.

<form action="http://example.com/login">
	<label for="username">User:</label> <input type="text" id="username" name="username" value=""/><br />
	<label for="password">Password:</label> <input type="password" id="password" name="password" value=""/>
	<input type="submit" value="Login"/>

Example 3: Cookie Containing Session ID Sent over HTTP

The Session ID Cookie must be transmitted over protected channels. If the cookie does not have the secure flag set [6] it is permitted for the application to transmit it unencrypted. Note below the setting of the cookie is done without the Secure flag, and the entire log in process is performed in HTTP and not HTTPS.


POST /login HTTP/1.1
Host: secure.example.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:25.0) Gecko/20100101 Firefox/25.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://secure.example.com/
Content-Type: application/x-www-form-urlencoded
Content-Length: 188

HTTP/1.1 302 Found
Date: Tue, 03 Dec 2013 21:18:55 GMT
Server: Apache
Cache-Control: no-store, no-cache, must-revalidate, max-age=0
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Pragma: no-cache
Set-Cookie: JSESSIONID=BD99F321233AF69593EDF52B123B5BDA; expires=Fri, 01-Jan-2014 00:00:00 GMT; path=/; domain=example.com; httponly
Location: private/
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
Content-Length: 0
Keep-Alive: timeout=1, max=100
Connection: Keep-Alive
Content-Type: text/html


GET /private HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:25.0) Gecko/20100101 Firefox/25.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: https://secure.example.com/login
Cookie: JSESSIONID=BD99F321233AF69593EDF52B123B5BDA;
Connection: keep-alive

HTTP/1.1 200 OK
Cache-Control: no-store
Pragma: no-cache
Expires: 0
Content-Type: text/html;charset=UTF-8
Content-Length: 730
Date: Tue, 25 Dec 2013 00:00:00 GMT


OWASP Resources


  • [5] curl can be used to check manually for pages