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cwe:cn:definition:352

CWE-352:跨站请求伪造(CSRF)

ID352
TypeCompound Element
AbstractionVariant
StructureComposite
StatusDraft
MITREhttp://cwe.mitre.org/data/definitions/352.html
Englishhttp://wiki.scap.org.cn/cwe/en/definition/352
Chinesehttp://wiki.scap.org.cn/cwe/cn/definition/352

Description Summary

The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.

Extended Description

When a web server is designed to receive a request from a client without any mechanism for verifying that it was intentionally sent, then it might be possible for an attacker to trick a client into making an unintentional request to the web server which will be treated as an authentic request. This can be done via a URL, image load, XMLHttpRequest, etc. and can result in exposure of data or unintended code execution.

Likelihood of Exploit

Medium to High

Common Consequences

Scope Technical Impace Note
Confidentiality
Integrity
Availability
Non-Repudiation
Access_Control
Gain privileges / assume identity
Bypass protection mechanism
Read application data
Modify application data
DoS: crash / exit / restart
The consequences will vary depending on the nature of the functionality that is vulnerable to CSRF. An attacker could effectively perform any operations as the victim. If the victim is an administrator or privileged user, the consequences may include obtaining complete control over the web application - deleting or stealing data, uninstalling the product, or using it to launch other attacks against all of the product's users. Because the attacker has the identity of the victim, the scope of CSRF is limited only by the victim's privileges.

Detection Methods

Detection Method - 1

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.

Specifically, manual analysis can be useful for finding this weakness, and for minimizing false positives assuming an understanding of business logic. However, it might not achieve desired code coverage within limited time constraints. For black-box analysis, if credentials are not known for privileged accounts, then the most security-critical portions of the application may not receive sufficient attention.

Consider using OWASP CSRFTester to identify potential issues and aid in manual analysis.

These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules.
2013/05/30 09:37

Detection Method - 2

Automated Static Analysis

CSRF is currently difficult to detect reliably using automated techniques. This is because each application has its own implicit security policy that dictates which requests can be influenced by an outsider and automatically performed on behalf of a user, versus which requests require strong confidence that the user intends to make the request. For example, a keyword search of the public portion of a web site is typically expected to be encoded within a link that can be launched automatically when the user clicks on the link.

Detection Method - 3

Automated Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Detection Method - 4

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Detection Method - 5

=== Dynamic Analysis with automated results interpretation === According to SOAR, the following detection techniques may be useful:

Detection Method - 6

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Detection Method - 7

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Detection Method - 8

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Detection Method - 9

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Potential Mitigations

Mitigation - 1

Architecture and Design

Strategy:Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, use anti-CSRF packages such as the OWASP CSRFGuard. [R.352.3]

Another example is the ESAPI Session Management control, which includes a component for CSRF. [R.352.9]

2013/05/30 09:36

Mitigation - 2

Implementation

Ensure that the application is free of cross-site scripting issues (CWE-79), because most CSRF defenses can be bypassed using attacker-controlled script.

Mitigation - 3

Architecture and Design

Generate a unique nonce for each form, place the nonce into the form, and verify the nonce upon receipt of the form. Be sure that the nonce is not predictable (CWE-330). [R.352.5]

Mitigation - 4

Architecture and Design

Identify especially dangerous operations. When the user performs a dangerous operation, send a separate confirmation request to ensure that the user intended to perform that operation.

Mitigation - 5

Architecture and Design

Use the “double-submitted cookie” method as described by Felten and Zeller:

When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user's machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same.

Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult.

This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [R.352.4]

Mitigation - 6

Architecture and Design

Do not use the GET method for any request that triggers a state change.

Mitigation - 7

Implementation

Check the HTTP Referer header to see if the request originated from an expected page. This could break legitimate functionality, because users or proxies may have disabled sending the Referer for privacy reasons.

Demonstrative Examples

Example - 1

This example PHP code attempts to secure the form submission process by validating that the user submitting the form has a valid session. A CSRF attack would not be prevented by this countermeasure because the attacker forges a request through the user's web browser in which a valid session already exists.

The following HTML is intended to allow a user to update a profile.

<form action="/url/profile.php" method="post"> 
<input type="text" name="firstname"/> 
<input type="text" name="lastname"/> 
<br/> 
<input type="text" name="email"/> 
<input type="submit" name="submit" value="Update"/> 
</form> 

profile.php contains the following code.

// initiate the session in order to validate sessions 
 
session_start(); 
 
//if the session is registered to a valid user then allow update 
 
if (! session_is_registered("username")) { 
 
echo "invalid session detected!"; 
 
// Redirect user to login page 
[...] 
 
exit; 
 
} 
 
// The user session is valid, so process the request 
// and update the information 
 
update_profile(); 
 
function update_profile { 
// read in the data from $POST and send an update 
// to the database 
SendUpdateToDatabase($_SESSION['username'], $_POST['email']); 
[...] 
echo "Your profile has been successfully updated."; 
 
} 

This code may look protected since it checks for a valid session. However, CSRF attacks can be staged from virtually any tag or HTML construct, including image tags, links, embed or object tags, or other attributes that load background images.

The attacker can then host code that will silently change the username and email address of any user that visits the page while remaining logged in to the target web application. The code might be an innocent-looking web page such as:

<SCRIPT> 
function SendAttack () { 
form.email = "attacker@example.com"; 
// send to profile.php 
form.submit(); 
 
} 
</SCRIPT> 
 
<BODY onload="javascript:SendAttack();"> 
 
<form action="http://victim.example.com/profile.php" id="form" method="post"> 
<input type="hidden" name="firstname" value="Funny"> 
<input type="hidden" name="lastname" value="Joke"> 
<br/> 
<input type="hidden" name="email"> 
</form> 

Notice how the form contains hidden fields, so when it is loaded into the browser, the user will not notice it. Because SendAttack() is defined in the body's onload attribute, it will be automatically called when the victim loads the web page.

Assuming that the user is already logged in to victim.example.com, profile.php will see that a valid user session has been established, then update the email address to the attacker's own address. At this stage, the user's identity has been compromised, and messages sent through this profile could be sent to the attacker's address.

Observed Examples

Reference Description
CVE-2004-1703Add user accounts via a URL in an img tag
CVE-2004-1995Add user accounts via a URL in an img tag
CVE-2004-1967Arbitrary code execution by specifying the code in a crafted img tag or URL
CVE-2004-1842Gain administrative privileges via a URL in an img tag
CVE-2005-1947Delete a victim's information via a URL or an img tag
CVE-2005-2059Change another user's settings via a URL or an img tag
CVE-2005-1674Perform actions as administrator via a URL or an img tag
CVE-2009-3520modify password for the administrator
CVE-2009-3022CMS allows modification of configuration via CSRF attack against the administrator
CVE-2009-3759web interface allows password changes or stopping a virtual machine via CSRF
cwe/cn/definition/352.txt · 最后更改: 2014/09/04 14:33 (外部编辑)