OWASP Top Ten Cheat Sheet

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Contents

Introduction

The following is a developer-centric defensive cheat sheet for the OWASP Top Ten Project. It also presents a quick reference based on OWASP Testing Project to help how to identify the risks.

OWASP Top Ten Cheat Sheet

Presentation Controller Model Testing (OWASP Testing Guide V3)
A1 Injection

Render: Set a correct content type Set safe character set (UTF-8) Set correct locale

On Submit: Enforce input field type and lengths Validate fields and provide feedback Ensure option selects and radio contain only sent values

Canonicalize using correct character set

Positive input validation using correct character set

(NR) Negative input validation (LR) Sanitize input

Tip: updating a negative list (such as looking for "script", "sCrIpT", "ßCrîpt", etc) will require expensive and constant deployments and will always fail as attackers work out your list of "bad" words. Positive validation is simpler, faster and usually more secure and needs updating far less than any other validation mechanism.

Parameterized queries

Object relational model (Hibernate) Active Record design pattern Stored procedures

Escape mechanisms such as ESAPI's Encoder.EncodeForLDAP() or Encoder.EncodeforOS()

Tip: All SQL Injection is due to dynamic SQL queries. Strongly consider prohibiting dynamic SQL queries within your organization

4.8.5 SQL Injection (OWASP-DV-005)

4.8.6 LDAP Injection (OWASP-DV-006) 4.8.7 ORM Injection (OWASP-DV-007) 4.8.8 XML Injection (OWASP-DV-008) 4.8.9 SSI Injection (OWASP-DV-009) 4.8.10 XPath Injection (OWASP-DV-010) 4.8.11 IMAP/SMTP Injection (OWASP-DV-011) 4.8.12 Code Injection (OWASP-DV-012) 4.8.13 OS Commanding (OWASP-DV-013) 4.8.14 Buffer overflow (OWASP-DV-014)


A2 XSS

Render Set correct content type Set safe character set (UTF-8) Set correct locale Output encode all user data as per output context Set input constraints

On Submit Enforce input field type and lengths Validate fields and provide feedback Ensure option selects and radio contain only sent values

Canonicalize using correct character set

Positive input validation using correct character set

(NR) Negative input validation (LR) Sanitize input

Tip: Only process data that is 100% trustworthy. Everything else is hostile and should be rejected.

Tip: Do not store data HTML encoded in the database. This prevents new uses for the data, such as web services, RSS feeds, FTP batches, data warehousing, cloud computing, and so on.

Tip: Use OWASP Scrubbr to clean tainted or hostile data from legacy data

4.8.1 Testing for Reflected Cross Site Scripting (OWASP-DV-001)

4.8.2 Testing for Stored Cross Site Scripting (OWASP-DV-002) 4.8.3 Testing for DOM based Cross Site Scripting (OWASP-DV-003) 4.8.4 Testing for Cross Site Flashing (OWASP-DV004)


A3 Weak authentication and session management Render

Validate user is authenticated Validate role is sufficient for this view Set "secure" and "HttpOnly" flags for session cookies Send CSRF token with forms

Design

Only use inbuilt session management Store secondary SSO / framework / custom session identifiers in native session object – do not send as additional headers or cookies

Validate user is authenticated Validate role is sufficient to perform this action Validate CSRF token

Validate role is sufficient to create, read, update, or delete data

Tip: Consider the use of a "governor" to regulate the maximum number of requests per second / minute / hour that this user may perform. For example, a typical banking user should not perform more than ten transactions a minute, and one hundred per second is dangerous and should be blocked.

4.4.2 Testing for user enumeration (OWASP-AT-002)

4.4.3 Testing for Guessable (Dictionary) User Account (OWASP-AT-003) 4.4.4 Brute Force Testing (OWASP-AT-004) 4.4.6 Testing for vulnerable remember password and pwd reset (OWASP-AT-006) 4.4.5 Testing for bypassing authentication schema (OWASP-AT-005) 4.4.7 Testing for Logout and Browser Cache Management (OWASP-AT-007) 4.4.8 Testing for CAPTCHA (OWASP-AT-008) 4.4.9 Testing Multiple Factors Authentication (OWASP-AT-009) 4.4.10 Testing for Race Conditions (OWASP-AT-010) 4.5.1 Testing for Session Management Schema (OWASP-SM-001) 4.5.2 Testing for Cookies attributes (OWASP-SM-002) 4.5.3 Testing for Session Fixation (OWASP-SM_003) 4.5.4 Testing for Exposed Session Variables (OWASP-SM-004) 4.5.5 Testing for CSRF (OWASP-SM-005) 4.6.2 Testing for bypassing authorization schema (OWASP-AZ-002) 4.6.3 Testing for Privilege Escalation (OWASP-AZ-003)


A4 Insecure Direct Object Reference If data is from internal trusted sources, no data is sent

Or

Render Send indirect random access reference map value

Obtain data from internal, trusted sources

Or

Obtain direct value from random access reference access map

Validate role is sufficient to create, read, update, or delete data 4.6.1 Testing for Path Traversal (OWASP-AZ-001)
A5 Cross Site Request Forgery Pre-render

Validate user is authenticated Validate role is sufficient for this view

Render Send CSRF token Set "secure" and "HttpOnly" flags for session cookies

Validate CSRF token

Validate role is sufficient to perform this action Validate role is sufficient

Tip: CSRF is always possible if there is XSS, so make sure XSS is eliminated within your application.

Validate role is sufficient to create, read, update, or delete data 4.5.5 Testing for CSRF (OWASP-SM-005)
A6 Security Misconfiguration Ensure web servers and application servers are hardened

PHP – Ensure allow_url_fopen and allow_url_include are both disabled in php.ini. Consider the use of Suhosin extension

Ensure web servers and application servers are hardened

XML – Ensure common web attacks (remote XSLT transforms, hostile XPath queries, recursive DTDs, and so on) are protected by your XML stack. Do not hand craft XML documents or queries – use the XML layer.

Ensure database servers are hardened 4.2.6 Analysis of Error Codes (OWASP-IG-006)

4.3.2 DB Listener Testing (OWASP-CM-002) 4.3.3 Infrastructure Configuration Management Testing (OWASP-CM-003) 4.3.4 Application Configuration Management Testing (OWASP-CM-004) 4.3.5 Testing for File Extensions Handling (OWASP-CM-005) 4.3.6 Old, Backup and Unreferenced Files (OWASP-CM-006) 4.3.7 Infrastructure and Application Admin Interfaces (OWASP-CM-007) 4.3.8 Testing for HTTP Methods and XST (OWASP-CM-008)


A7 Insufficient Cryptographic Storage Design

Use strong ciphers (AES 128 or better) Use strong hashes (SHA 256 or better) with salts for passwords Protect keys more than any other asset

Render Do not send keys or hashes to the browser

Design

Use strong ciphers (AES 128 or better) Use strong hashes (SHA 256 or better) with salts for passwords Protect keys more than any other asset

Tip: Only certain personally identifiable information and sensitive values MUST be encrypted. Encrypt data that would be embarrassing or costly if it was leaked or stolen.

Tip: It is best to encrypt data on the application server, rather than the database server.

Design

Tip: Do not use RDBMS database, row or table level encryption. The data can be retrieved in the clear by anyone with direct access to the server, or over the network using the application credentials. It might even traverse the network in the clear despite being "encrypted" on disk.


A8 Failure to Restrict URL access Design

Ensure all non-web data is outside the web root (logs, configuration, etc) Use octet byte streaming instead of providing access to real files such as PDFs or CSVs or similar Ensure every page requires a role, even if it is "guest" Pre-render Validate user is authenticated Validate role is sufficient to view secured URL

Render Send CSRF token

Validate user is authenticated

Validate role is sufficient to perform secured action Validate CSRF token

Tip: It's impossible to control access to secured resources that the web application server does not directly serve. Therefore, PDF reports or similar should be served by the web application server using binary octet streaming.

Tip: Assume attackers will learn where "hidden" directories and "random" filenames are, so do not store these files in the web root, even if they are not directly linked.

Validate role is sufficient to create, read, update, or delete data 4.4.5 Testing for bypassing authentication schema (OWASP-AT-005)

4.6.1 Testing for Path Traversal (OWASP-AZ-001) 4.6.2 Testing for bypassing authorization schema (OWASP-AZ-002)

A9 Insufficient Transport Layer Protection Use TLS 1.2 or later for all web communications

Buy extended validation (EV) certificates for public web servers

Tip: Use TLS 1.2 always – even internally. Most snooping is done within corporate networks – and it is as easy and unethical as fishing with dynamite.

Mandate strong encrypted communications between web and database servers and any other servers or administrative users Mandate strong encrypted communications with application servers and any other servers or administrative users 4.3.1 SSL/TLS Testing (OWASP-CM-001)

4.4.1 Credentials transport over an encrypted channel (OWASP-AT-001)

A10 Unvalidated Redirects and Forwards Design the app without URL redirection parameters

or

Render Use random indirect object references for redirection parameters

Design the app without URL redirection parameters

or

Obtain direct redirection parameter from random indirect reference access map (LR) Positive validation of redirection parameter (NR) Java – Do not forward() requests as this prevents SSO access control mechanisms

Validate role is sufficient to create, read, update, or delete data

Authors and Primary Editors

Andrew van der Stock vanderaj[at]owasp.org

Ismael Rocha Gonçalves ismaelrg[at]gmail.com

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