CWE-601 Detail

The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.

Background Details

Phishing is a general term for deceptive attempts to coerce private information from users that will be used for identity theft.

Modes Of Introduction

Architecture and Design : OMISSION: This weakness is caused by missing a security tactic during the architecture and design phase.
Implementation

Applicable Platforms

Language

Class: Not Language-Specific (Undetermined)

Technologies

Class: Web Based (Undetermined)

Common Consequences

Observed Examples

Potential Mitigations

Phases : Implementation

Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.

When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."

Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

Use a list of approved URLs or domains to be used for redirection.

Phases : Architecture and Design
Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
Phases : Architecture and Design

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

For example, ID 1 could map to "/login.asp" and ID 2 could map to "http://www.example.com/". Features such as the ESAPI AccessReferenceMap [REF-45] provide this capability.

Phases : Architecture and Design
Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application [REF-483]. Be sure that the nonce is not predictable (CWE-330).
Phases : Architecture and Design // Implementation

Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

Many open redirect problems occur because the programmer assumed that certain inputs could not be modified, such as cookies and hidden form fields.

Phases : Operation
Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

Detection Methods

Manual Static Analysis

Since this weakness does not typically appear frequently within a single software package, manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all potentially-vulnerable operations can be assessed within limited time constraints.
Effectiveness : High

Automated Dynamic Analysis

Automated black box tools that supply URLs to every input may be able to spot Location header modifications, but test case coverage is a factor, and custom redirects may not be detected.

Automated Static Analysis

Automated static analysis tools may not be able to determine whether input influences the beginning of a URL, which is important for reducing false positives.

Automated Static Analysis

Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)
Effectiveness : High

Automated Static Analysis - Binary or Bytecode

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

Effectiveness : High

Dynamic Analysis with Automated Results Interpretation

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

Effectiveness : High

Dynamic Analysis with Manual Results Interpretation

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

Effectiveness : High

Manual Static Analysis - Source Code

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

Effectiveness : High

Automated Static Analysis - Source Code

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

Effectiveness : High

Architecture or Design Review

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

Effectiveness : High

Vulnerability Mapping Notes

Justification : This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.
Comment : Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Related Attack Patterns

NotesNotes

Whether this issue poses a vulnerability will be subject to the intended behavior of the application. For example, a search engine might intentionally provide redirects to arbitrary URLs.

References

REF-483

Exploitable Redirects on the Web: Identification, Prevalence, and Defense
Craig A. Shue, Andrew J. Kalafut, Minaxi Gupta.
https://www.cprogramming.com/tutorial/exceptions.html

REF-484

Open redirect vulnerabilities: definition and prevention
Russ McRee.
http://www.net-security.org/dl/insecure/INSECURE-Mag-17.pdf

REF-485

Top 25 Series - Rank 23 - Open Redirect
Jason Lam.
http://software-security.sans.org/blog/2010/03/25/top-25-series-rank-23-open-redirect

REF-45

OWASP Enterprise Security API (ESAPI) Project
OWASP.
http://www.owasp.org/index.php/ESAPI

Submission

Modifications