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OWASP Top Ten Cheat Sheet

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Introduction

The following is a developer-centric defensive cheat sheet for the 2013 release of 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 V4)
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()
    • Encoder.EncodeforOS()

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

A2 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.

A3 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

A4 Insecure Direct Object References 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.
A5 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
A6 Sensitive Data Exposure Design:
  • Use strong ciphers (AES 128 or better) with secure mode of operations (do not use ECB).
  • Use strong hashes (SHA 256 or better) with salts for passwords.
  • Protect keys more than any other asset.
  • 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.

Render:

  • Do not send keys or hashes to the browser.
 Design:
  • Use strong ciphers (AES 128 or better) with secure mode of operations (do not use ECB).
  • Use strong hashes (SHA 256 or better) with salts for passwords.
  • Protect keys more than any other asset.
  • Mandate strong encrypted communications between web and database servers and any other servers or administrative users.

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:
  • Mandate strong encrypted communications with application servers and any other servers or administrative users.

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.

A7 Missing Function Level Access Control 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

Testing Directory traversal/file include (OTG-AUTHZ-001) Testing for bypassing authorization schema (OTG-AUTHZ-002) Testing for bypassing authentication schema (OTG-AUTHN-004)

A8 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
A9 Using Components with Known Vulnerabilities




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

Jorge Correa [email protected]

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