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Attack Surface Analysis for Requests Library

Attack Surface Identification

Components and Entry Points

  1. HTTP Request Handling API

    • Description: The requests library provides functions and classes for making HTTP requests.
    • Entry Points:
      • Functions like requests.get, requests.post, requests.put, etc.
      • Classes such as Session, Request, PreparedRequest.
    • Implementation Details:
      • Implemented in src/requests/api.py, src/requests/models.py, src/requests/sessions.py.

  2. URL Parsing and Handling

    • Description: Processing and sanitizing user-provided URLs.
    • Potential Vulnerabilities:
      • Malformed or malicious URLs leading to SSRF, open redirects, or information disclosure.
    • Implementation Details:
      • URL parsing in src/requests/utils.py, src/requests/models.py.

  3. SSL/TLS Connections and Certificate Verification

    • Description: Handling secure HTTP connections, SSL context configuration, certificate verification.
    • Components:
      • SSL context creation and configuration.
      • Certificate verification logic.
      • Handling of the verify parameter.
      • Custom certificate authorities via certifi.
    • Potential Vulnerabilities:
      • Insecure SSL defaults.
      • Bypassing certificate verification.
      • Vulnerable SSL/TLS protocols or ciphersuites.
    • Implementation Details:
      • src/requests/certs.py: provides default CA bundle.
      • src/requests/adapters.py: cert_verify method.
      • SSL context usage in src/requests/adapters.py.

  4. Authentication Mechanisms

    • Description: Handling HTTP authentication methods like Basic, Digest, and Proxy authentication.
    • Components:
      • Basic Auth (HTTPBasicAuth)
      • Digest Auth (HTTPDigestAuth)
      • Proxy Authentication (HTTPProxyAuth)
    • Potential Vulnerabilities:
      • Credentials leakage in logs or error messages.
      • Insecure storage or handling of credentials.
      • Reuse of authentication headers in redirects.
    • Implementation Details:
      • Auth handlers in src/requests/auth.py.
      • Authorization header management in src/requests/adapters.py, src/requests/sessions.py.

  5. Redirect Handling

    • Description: Processing HTTP redirects and maintaining session state.
    • Potential Vulnerabilities:
      • Redirection loops.
      • Leaking of sensitive headers (e.g., Authorization) during redirects.
      • Open redirects leading to phishing attacks.
    • Implementation Details:
      • Redirection logic in src/requests/sessions.py (SessionRedirectMixin class).
      • Max redirects controlled by Session.max_redirects.
      • Authentication stripping in src/requests/sessions.py.

  6. Cookie Management

    • Description: Handling cookies sent to and from servers.
    • Components:
      • CookieJar management.
      • Domain and path scoping.
      • Cookie setting and retrieval.
    • Potential Vulnerabilities:
      • Cookie injection attacks.
      • Insecure persistence of cookies.
    • Implementation Details:
      • Cookie handling in src/requests/cookies.py.
      • Cookie extraction and insertion in src/requests/models.py, src/requests/sessions.py.

  7. Proxy Configuration and Handling

    • Description: Support for using HTTP proxies, including SOCKS proxies.
    • Potential Vulnerabilities:
      • Proxy credential leakage.
      • Insecure default proxy settings.
      • Transparent redirection of traffic to malicious proxies.
    • Implementation Details:
      • Proxy handling in src/requests/sessions.py, src/requests/adapters.py, src/requests/utils.py.
      • Proxy URL parsing and usage in src/requests/adapters.py.

  8. Header Processing

    • Description: Managing HTTP headers in requests and responses.
    • Potential Vulnerabilities:
      • Injection attacks via headers.
      • Header smuggling.
      • Reuse or leakage of sensitive headers.
    • Implementation Details:
      • Header validation in src/requests/utils.py (check_header_validity function).
      • Header manipulation in src/requests/models.py.

  9. File Handling and Multipart Form Data

    • Description: Supporting file uploads and encoding of multipart form data.
    • Potential Vulnerabilities:
      • Unsafe file handling leading to resource exhaustion.
      • Injection of malicious content via uploaded files.
    • Implementation Details:
      • Multipart encoding in src/requests/models.py (prepare_body method).
      • File name and content handling in src/requests/models.py.

  10. Third-Party Dependencies

    • Description: Use of external libraries like urllib3, chardet, charset_normalizer, idna, and certifi.
    • Potential Vulnerabilities:
      • Outdated or vulnerable dependencies.
      • Dependency confusion attacks.
    • Implementation Details:
      • Dependencies declared in setup.cfg.
      • Imported in modules like src/requests/compat.py, src/requests/packages.py, src/requests/__init__.py.

  11. Input Data Handling

    • Description: Handling of data provided by users for request bodies, parameters, headers.
    • Potential Vulnerabilities:
      • Injection attacks via untrusted data.
      • Buffer overflows or memory exhaustion with large inputs.
    • Implementation Details:
      • Data encoding and parameter handling in src/requests/models.py, src/requests/utils.py.

  12. CA Bundle Management

    • Description: Use of certifi package to manage CA certificates for SSL/TLS verification.
    • Potential Vulnerabilities:
      • Outdated or compromised CA certificates may not verify malicious certificates.
    • Implementation Details:
      • Certificate management relies on certifi dependency specified in setup.cfg and discussed in documentation docs/user/advanced.rst.

  13. Test Utilities Exposure

    • Description: Inclusion of testing utilities and servers in the codebase.
    • Potential Vulnerabilities:
      • If test code is accidentally included in production distributions, it could expose internal functions or create security vulnerabilities.
    • Implementation Details:
      • Test server code in tests/test_lowlevel.py, tests/testserver/server.py.
      • Test configurations in pyproject.toml, setup.cfg.

Threat Enumeration

1. HTTP Request Handling API

  • Threat: Tampering with Request Parameters

    • Description: Attackers could manipulate request parameters to inject malicious inputs.
    • Attack Vectors: If unvalidated or improperly handled, parameters could be exploited (e.g., command injection).
    • Components: src/requests/models.py, src/requests/sessions.py, src/requests/api.py

  • Threat: Information Disclosure via Error Messages

    • Description: Detailed error messages could leak sensitive information.
    • Attack Vectors: Exceptions or tracebacks containing sensitive data.
    • Components: src/requests/exceptions.py, src/requests/models.py

2. URL Parsing and Handling

  • Threat: Server-Side Request Forgery (SSRF)

    • Description: Crafting URLs that cause the application to make requests to internal resources.
    • Attack Vectors: Supplying malicious URLs to access internal services.
    • Components: src/requests/models.py, src/requests/utils.py

  • Threat: Open Redirects

    • Description: Improper validation of redirect URLs leading to open redirects.
    • Attack Vectors: Manipulated redirect location headers pointing to attacker-controlled URLs.
    • Components: src/requests/sessions.py (resolve_redirects method)

3. SSL/TLS Connections and Certificate Verification

  • Threat: Man-in-the-Middle (MitM) Attacks via Insecure SSL Configuration

    • Description: Disabling SSL verification allows attackers to intercept and tamper with communications.
    • Attack Vectors: Setting verify=False, accepting self-signed or invalid certificates.
    • Components: src/requests/adapters.py (cert_verify method)

  • Threat: Man-in-the-Middle (MitM) Attacks via Outdated CA Certificates

    • Description: Attackers could exploit outdated or compromised CA certificates in the certifi package to intercept and decrypt communications.
    • Attack Vectors: Applications using an outdated certifi package may trust malicious certificates.
    • Components: certifi dependency, SSL verification processes.

4. Authentication Mechanisms

  • Threat: Credential Leakage

    • Description: Credentials might be transmitted over insecure channels or logged.
    • Attack Vectors: Sending credentials over HTTP instead of HTTPS, logging sensitive information.
    • Components: src/requests/auth.py, src/requests/adapters.py

  • Threat: Reusing Authentication Headers on Redirects

    • Description: Authentication headers might be sent to unintended hosts during redirects.
    • Attack Vectors: Following redirects to different domains while maintaining Authorization headers.
    • Components: src/requests/sessions.py (should_strip_auth method)

5. Redirect Handling

  • Threat: Authentication Header Leakage via Redirects

    • Description: Sensitive headers sent to untrusted domains.
    • Attack Vectors: Not stripping Authorization headers on cross-domain redirects.
    • Components: src/requests/sessions.py

  • Threat: Redirection Loops Leading to Denial of Service

    • Description: Infinite redirect loops causing resource exhaustion.
    • Attack Vectors: Handling of redirects without proper loop detection or limit.
    • Components: src/requests/sessions.py (max_redirects parameter)

6. Cookie Management

  • Threat: Cookie Injection and Manipulation
    • Description: Attackers could inject or manipulate cookies to alter session state.
    • Attack Vectors: Acceptance of cookies from untrusted sources, weak domain/path validation.
    • Components: src/requests/cookies.py, src/requests/sessions.py

7. Proxy Configuration and Handling

  • Threat: Proxy Credential Exposure

    • Description: Proxy credentials could be exposed in logs or via insecure connections.
    • Attack Vectors: Including credentials in proxy URLs, transmitting over insecure channels.
    • Components: src/requests/adapters.py, src/requests/sessions.py

  • Threat: Proxy Injection via Environment Variables

    • Description: Manipulating proxy settings via environment variables to redirect traffic.
    • Attack Vectors: Untrusted environment variables leading to traffic redirection.
    • Components: src/requests/utils.py

8. Header Processing

  • Threat: Header Injection

    • Description: Malicious data included in headers causing response splitting or smuggling.
    • Attack Vectors: Not validating headers properly.
    • Components: src/requests/utils.py, src/requests/models.py

  • Threat: Sensitive Data in Headers

    • Description: Sensitive data included in headers sent over insecure channels.
    • Attack Vectors: Headers containing tokens or credentials sent over HTTP.
    • Components: src/requests/models.py, src/requests/adapters.py

9. File Handling and Multipart Form Data

  • Threat: Resource Exhaustion via Large File Uploads
    • Description: Sending extremely large files causing memory or disk exhaustion.
    • Attack Vectors: Unbounded file size during multipart encoding.
    • Components: src/requests/models.py, src/requests/utils.py

10. Third-Party Dependencies

  • Threat: Vulnerable Dependencies

    • Description: Using outdated or vulnerable libraries exposes the system to exploits.
    • Attack Vectors: Vulnerabilities in urllib3, chardet, idna, certifi.
    • Components: src/requests/compat.py, src/requests/__init__.py, setup.cfg

  • Threat: Dependency Confusion

    • Description: Attackers supplying malicious packages with the same name as internal dependencies.
    • Attack Vectors: Malicious packages uploaded to public repositories with higher version numbers.
    • Components: Installation process via setup.cfg

11. Input Data Handling

  • Threat: Injection Attacks via Untrusted Input
    • Description: Unvalidated input leading to SQL injection, command injection.
    • Attack Vectors: Malicious payloads in data, parameters.
    • Components: src/requests/models.py, src/requests/utils.py

12. CA Bundle Management

  • Threat: Man-in-the-Middle (MitM) Attacks via Outdated CA Certificates
    • Description: Attackers could exploit outdated or compromised CA certificates in the certifi package to intercept and decrypt communications.
    • Attack Vectors: Applications using an outdated certifi package may trust malicious certificates.
    • Components: certifi dependency, SSL verification processes.

13. Test Utilities Exposure

  • Threat: Exposure of Test Server Utilities in Production Environment
    • Description: If test server code is included in the production package, attackers could exploit vulnerabilities in these test utilities.
    • Attack Vectors: Inclusion of tests/testserver/server.py in production could expose unnecessary network interfaces.
    • Components: tests directory, test server code.

Impact Assessment

Critical Severity

  • Man-in-the-Middle (MitM) Attacks via Insecure SSL Configuration

    • Impact: Compromise of confidentiality and integrity.
    • Likelihood: High if SSL verification is disabled.
    • Existing Controls: SSL verification enabled by default.
    • Severity: Critical

  • Dependency Confusion

    • Impact: Execution of malicious code during installation.
    • Likelihood: Medium to High, depending on dependency management practices.
    • Existing Controls: Use of standard package indices.
    • Severity: Critical

High Severity

  • Man-in-the-Middle (MitM) Attacks via Outdated CA Certificates

    • Impact: Compromise of confidentiality and integrity through interception of encrypted communications.
    • Likelihood: Medium to High if certifi is not regularly updated.
    • Existing Controls: Users must update certifi to receive updated CA bundles.
    • Severity: High

  • Credential Leakage

    • Impact: Disclosure of sensitive credentials.
    • Likelihood: Medium, depends on usage patterns.
    • Existing Controls: Secure handling recommended but depends on user implementation.
    • Severity: High

  • Reusing Authentication Headers on Redirects

    • Impact: Credentials sent to unintended hosts.
    • Likelihood: Medium
    • Existing Controls: Stripping auth headers when redirecting to a different host.
    • Severity: High

  • Vulnerable Dependencies

    • Impact: Introduction of known vulnerabilities.
    • Likelihood: Medium to High
    • Existing Controls: Specifying dependency versions in setup.cfg.
    • Severity: High

  • Injection Attacks via Untrusted Input

    • Impact: Execution of arbitrary code or commands.
    • Likelihood: Medium
    • Existing Controls: User responsibility to sanitize inputs.
    • Severity: High

Medium Severity

  • Server-Side Request Forgery (SSRF)

    • Impact: Unauthorized access to internal resources.
    • Likelihood: High if user input is not validated.
    • Severity: Medium

  • Proxy Credential Exposure

    • Impact: Disclosure of proxy credentials.
    • Likelihood: Medium
    • Severity: Medium

  • Sensitive Data in Headers

    • Impact: Exposure of sensitive information over insecure channels.
    • Likelihood: Medium
    • Severity: Medium

  • Cookie Injection and Manipulation

    • Impact: Session hijacking or manipulation.
    • Likelihood: Medium
    • Severity: Medium

  • Resource Exhaustion via Large File Uploads

    • Impact: Denial of service.
    • Likelihood: Medium
    • Severity: Medium

  • Exposure of Test Server Utilities in Production Environment

    • Impact: Potential unauthorized access or execution of code.
    • Likelihood: Low; test code is typically not included in production packages.
    • Existing Controls: Standard packaging excludes the tests directory.
    • Severity: Medium

Low Severity

  • Tampering with Request Parameters

    • Impact: Potential unauthorized actions.
    • Likelihood: Medium
    • Severity: Low

  • Information Disclosure via Error Messages

    • Impact: Leakage of sensitive information.
    • Likelihood: Low to Medium
    • Severity: Low

  • Redirection Loops Leading to Denial of Service

    • Impact: Resource exhaustion.
    • Likelihood: Low to Medium
    • Severity: Low

Threat Ranking

  1. Critical

    • MitM via Insecure SSL Configuration
    • Dependency Confusion

  2. High

    • Man-in-the-Middle (MitM) Attacks via Outdated CA Certificates
    • Credential Leakage
    • Reusing Authentication Headers on Redirects
    • Vulnerable Dependencies
    • Injection Attacks via Untrusted Input

  3. Medium

    • Server-Side Request Forgery (SSRF)
    • Proxy Credential Exposure
    • Sensitive Data in Headers
    • Cookie Injection and Manipulation
    • Resource Exhaustion via Large File Uploads
    • Exposure of Test Server Utilities in Production Environment

  4. Low

    • Tampering with Request Parameters
    • Information Disclosure via Error Messages
    • Redirection Loops Leading to Denial of Service

Mitigation Recommendations

Mitigation for MitM via Insecure SSL Configuration

  • Recommendation:
    • Enforce SSL verification by default and discourage disabling it.
    • Display prominent warnings when verify=False is used.
    • Provide documentation on the risks of disabling SSL verification.
  • Threats Addressed: Man-in-the-Middle Attacks via Insecure SSL Configuration
  • References:

Mitigation for Dependency Confusion

  • Recommendation:
    • Use explicit dependency version pinning and verify package authenticity.
    • Regularly update dependencies to patched versions.
    • Encourage the use of checksum verification for packages.
  • Threats Addressed: Dependency Confusion, Vulnerable Dependencies
  • References:

Mitigation for Man-in-the-Middle (MitM) Attacks via Outdated CA Certificates

  • Recommendation:
    • Ensure the certifi package is regularly updated to include the latest trusted CA certificates.
    • Provide guidance to users on the importance of keeping dependencies up to date.
  • Threats Addressed: Man-in-the-Middle (MitM) Attacks via Outdated CA Certificates
  • References:

Mitigation for Credential Leakage

  • Recommendation:
    • Avoid logging sensitive data such as credentials.
    • Ensure that credentials are only sent over secure channels (HTTPS).
    • Implement checks to prevent sending credentials over HTTP.
  • Threats Addressed: Credential Leakage
  • References:

Mitigation for Reusing Authentication Headers on Redirects

  • Recommendation:
    • Ensure Authorization headers are stripped when redirecting to different hosts.
    • Update should_strip_auth method to handle edge cases.
  • Threats Addressed: Reusing Authentication Headers on Redirects
  • References:

Mitigation for Injection Attacks via Untrusted Input

  • Recommendation:
    • Implement input validation and sanitization within the library where applicable.
    • Encourage users to validate inputs before usage.
  • Threats Addressed: Injection Attacks via Untrusted Input
  • References:

Mitigation for Server-Side Request Forgery (SSRF)

  • Recommendation:
    • Provide utilities or guidelines for validating and sanitizing URLs.
    • Warn users about the risks of making requests to user-supplied URLs.
  • Threats Addressed: Server-Side Request Forgery (SSRF)
  • References:

Mitigation for Proxy Credential Exposure

  • Recommendation:
    • Avoid including credentials in proxy URLs.
    • Support separate parameters or secure methods for proxy authentication.
  • Threats Addressed: Proxy Credential Exposure
  • References:

Mitigation for Sensitive Data in Headers

  • Recommendation:
    • Educate users on avoiding sending sensitive data in headers.
    • Provide mechanisms to enforce secure transmission when sensitive headers are used.
  • Threats Addressed: Sensitive Data in Headers
  • References:

Mitigation for Cookie Injection and Manipulation

  • Recommendation:
    • Implement strict cookie handling policies.
    • Sanitize cookie domains and paths.
  • Threats Addressed: Cookie Injection and Manipulation
  • References:

Mitigation for Resource Exhaustion via Large File Uploads

  • Recommendation:
    • Implement configurable limits on file sizes.
    • Stream file uploads to avoid memory exhaustion.
  • Threats Addressed: Resource Exhaustion via Large File Uploads
  • References:

Mitigation for Exposure of Test Server Utilities in Production Environment

  • Recommendation:
    • Ensure that test code and utilities are excluded from production distributions.
    • Review build and packaging processes to prevent accidental inclusion of test code.
  • Threats Addressed: Exposure of Test Server Utilities in Production Environment
  • References:

QUESTIONS & ASSUMPTIONS

  • Assumptions:

    • Users of the requests library are expected to handle input validation.
    • SSL verification is enabled by default, but users can disable it.
    • The library relies on third-party dependencies which are properly maintained.
    • Logging practices are left to the discretion of library users.
    • Test code and utilities are not included in production distributions.

  • Questions:

    • Are there measures to prevent users from accidentally disabling SSL verification without understanding the risks?
    • How does the library handle updates to third-party dependencies to address security vulnerabilities?
    • Is there guidance provided to users on safe practices for handling authentication and sensitive data?
    • What mechanisms are in place to sanitize or validate headers and cookies to prevent injection attacks?
    • Are build and packaging processes reviewed to ensure test code is not included in production distributions?
    • How are updates to the certifi package communicated to users to ensure CA certificates remain up to date?