Skip to content

Latest commit

 

History

History
227 lines (171 loc) · 22.5 KB

sec-design-deep-analysis.md

File metadata and controls

227 lines (171 loc) · 22.5 KB

Certainly! Let's perform a deep security analysis of Pandoc based on the provided security design review.

Deep Security Analysis of Pandoc

1. Objective, Scope, and Methodology

Objective:

The primary objective of this deep security analysis is to thoroughly evaluate the security posture of Pandoc, a universal document converter. This analysis will focus on identifying potential security vulnerabilities within Pandoc's architecture, specifically within its core components responsible for parsing, converting, and generating documents in various formats. The goal is to provide actionable, Pandoc-specific security recommendations and mitigation strategies to enhance the overall security of the application and protect users from potential threats arising from malicious or malformed documents.

Scope:

This analysis will encompass the following areas based on the provided Security Design Review and C4 diagrams:

  • Core Components: Pandoc CLI, Format Readers, and Format Writers as depicted in the Container Diagram.
  • Data Flow: The flow of data from input files through Pandoc's processing to output files.
  • Deployment Model: Standalone executable distribution as described in the Deployment Diagram.
  • Build Process: Stack-based Haskell build process as outlined in the Build Diagram.
  • Identified Security Controls and Risks: Existing and recommended security controls, accepted risks, and security requirements as stated in the Security Posture section.

This analysis will not cover:

  • Security of user environments (as it is an accepted risk).
  • Detailed analysis of every single document format supported by Pandoc (due to the vast number of formats).
  • Operational security aspects beyond the application itself (e.g., network security, server security if Pandoc is used in a server context, which is not the primary deployment model but possible).

Methodology:

The methodology for this deep analysis will involve:

  1. Document Review: In-depth review of the provided Security Design Review document, including business and security posture, C4 diagrams, and risk assessment.
  2. Architecture and Data Flow Inference: Based on the C4 diagrams and component descriptions, infer the detailed architecture and data flow within Pandoc, focusing on how input documents are processed and output documents are generated.
  3. Component-Level Security Analysis: Analyze each key component (Pandoc CLI, Format Readers, Format Writers) for potential security vulnerabilities, considering common attack vectors relevant to document processing applications. This will include:
    • Input Validation Analysis: Examining how Pandoc validates input documents and identifying potential bypasses or weaknesses.
    • Parsing Logic Analysis: Analyzing the security implications of parsing complex and potentially malicious document formats.
    • Output Generation Analysis: Assessing the security of output generation, including potential injection vulnerabilities in output formats.
    • Dependency Analysis: Considering the security of third-party libraries used by Pandoc, especially within Format Readers and Writers.
  4. Threat Modeling: Identify potential threats and attack scenarios targeting Pandoc, considering the identified vulnerabilities and the application's context.
  5. Mitigation Strategy Development: Develop specific, actionable, and tailored mitigation strategies for the identified threats, focusing on practical recommendations for the Pandoc development team.
  6. Alignment with Security Requirements and Controls: Ensure that the recommendations align with the stated security requirements and build upon the existing and recommended security controls.

2. Security Implications of Key Components

Based on the Container Diagram and component descriptions, let's break down the security implications of each key component:

a) Pandoc CLI:

  • Security Implications:
    • Command-Line Argument Parsing Vulnerabilities: While less common in Haskell due to its type safety, vulnerabilities could arise from incorrect parsing of command-line arguments, especially if complex options or file paths are handled improperly. This could potentially lead to unexpected behavior or even command injection if external commands are executed based on user input (though less likely in Pandoc's architecture).
    • Process Isolation (Limited Relevance): As a CLI tool, Pandoc runs as a process initiated by the user. While process isolation is generally a good security practice, its direct relevance is limited in this context. However, if Pandoc were to spawn subprocesses for certain conversions (which is not explicitly stated but possible for external tools), the security of these subprocesses and inter-process communication would become relevant.
    • Orchestration Logic Flaws: Bugs in the CLI's logic for selecting and invoking Format Readers and Writers could lead to unexpected behavior or bypasses in security checks if they exist at this level.
    • Logging and Error Handling: Insufficient or overly verbose error messages could leak sensitive information about the system or internal workings, aiding attackers. Improper logging could hinder incident response and security monitoring.

b) Format Readers:

  • Security Implications:
    • Primary Attack Surface: Format Readers are the most critical security component as they directly process untrusted input documents. They are the primary attack surface for vulnerabilities.
    • Parsing Vulnerabilities: Complex document formats are inherently difficult to parse securely. Vulnerabilities such as:
      • Buffer Overflows/Memory Corruption: While Haskell's memory safety mitigates classic buffer overflows, logical errors in parsing logic could still lead to memory-related issues or unexpected program states.
      • Denial of Service (DoS): Maliciously crafted documents could exploit parsing inefficiencies or algorithmic complexity in Readers to cause excessive resource consumption (CPU, memory), leading to DoS.
      • Format String Bugs (Less Likely in Haskell): While less typical in Haskell, improper use of string formatting functions could theoretically lead to format string vulnerabilities if user-controlled data is directly used in format strings.
      • XML External Entity (XXE) Injection (Relevant for XML-based formats): If Readers process XML-based formats (e.g., DOCX, EPUB), they could be vulnerable to XXE injection if external entity processing is not disabled or properly secured.
      • Billion Laughs/XML Bomb (DoS for XML formats): Similar to XXE, XML bombs can exploit recursive entity expansion to cause extreme memory consumption and DoS.
      • Logic Bugs in Format-Specific Parsing: Each format reader has its own parsing logic, and vulnerabilities can arise from subtle errors in handling specific format features, edge cases, or malformed inputs.
    • Input Validation Weaknesses: Insufficient or incomplete input validation in Readers could allow malicious documents to bypass checks and trigger parsing vulnerabilities.
    • Dependency Vulnerabilities: Format Readers might rely on third-party libraries for parsing specific formats. Vulnerabilities in these dependencies could directly impact Pandoc's security.

c) Format Writers:

  • Security Implications:
    • Output Injection Vulnerabilities: Format Writers are responsible for generating output documents. If they incorrectly handle the internal document representation or user-controlled data during output generation, they could introduce injection vulnerabilities in the output format. Examples include:
      • HTML/JavaScript Injection: If generating HTML output, improper encoding or sanitization of content could lead to Cross-Site Scripting (XSS) vulnerabilities if the generated HTML is later displayed in a web browser.
      • Command Injection (Less Likely but Possible): In formats that support embedding commands or scripts (e.g., potentially in some document formats or if Pandoc were extended to generate configuration files), vulnerabilities could arise if user-controlled data is used to construct these commands without proper sanitization.
    • Output Sanitization Issues: Failure to properly sanitize or encode output content could lead to various issues, including:
      • Information Disclosure: Accidental inclusion of sensitive data in output documents due to incorrect handling of internal representations.
      • Format Corruption: Incorrect output encoding or formatting could lead to corrupted or unreadable output documents.
    • Dependency Vulnerabilities: Similar to Readers, Writers might use third-party libraries for output generation. Vulnerabilities in these dependencies could affect the security of the generated output.

3. Architecture, Components, and Data Flow Inference

Based on the diagrams and descriptions, we can infer the following architecture and data flow:

Architecture:

Pandoc follows a modular architecture centered around the Pandoc CLI. The core components are:

  1. Pandoc CLI (Executable): The main entry point, responsible for:

    • Parsing command-line arguments (input file, output format, options).
    • Loading the appropriate Format Reader based on the input file extension or specified format.
    • Invoking the selected Format Reader to parse the input document into an internal, abstract representation (likely a Haskell data structure).
    • Performing document transformations and manipulations on the internal representation (core conversion logic).
    • Loading the appropriate Format Writer based on the desired output format.
    • Invoking the selected Format Writer to generate the output document from the internal representation.
    • Handling errors and outputting results.

  2. Format Readers (Libraries): A collection of independent libraries, each responsible for parsing a specific input document format. They:

    • Receive an input file (or stream).
    • Perform format-specific parsing and validation.
    • Convert the parsed document into Pandoc's internal representation.
    • Handle format-specific errors.

  3. Format Writers (Libraries): A collection of independent libraries, each responsible for generating a specific output document format. They:

    • Receive Pandoc's internal document representation.
    • Generate an output document in the specified format.
    • Handle format-specific output encoding and formatting.

Data Flow:

  1. User Input: The user executes the Pandoc CLI with command-line arguments, including the input file and desired output format.
  2. CLI Processing: The Pandoc CLI parses the arguments, identifies the input format, and loads the corresponding Format Reader.
  3. Input Parsing: The selected Format Reader reads and parses the input file. It performs format-specific validation and converts the document content into Pandoc's internal representation.
  4. Internal Representation: The document is now represented in an abstract, format-agnostic data structure within Pandoc.
  5. Conversion Logic (Implicit): Pandoc's core logic operates on this internal representation to perform the document conversion. This might involve transformations, filtering, and restructuring of the document content within the internal representation.
  6. Output Generation: The Pandoc CLI identifies the desired output format and loads the corresponding Format Writer.
  7. Output Writing: The selected Format Writer takes the internal representation and generates the output document in the specified format, writing it to the output file.

Security-Relevant Data Flow Points:

  • Input File to Format Reader: This is the primary point where untrusted data enters the system. Secure parsing and validation within Format Readers are crucial.
  • Internal Representation: While internal, the security of the internal representation itself is important. If it's not designed securely, vulnerabilities could be introduced during the conversion logic phase.
  • Internal Representation to Format Writer: Data flowing from the internal representation to Format Writers needs to be handled carefully to prevent output injection vulnerabilities.

4. Tailored Security Considerations for Pandoc

Given Pandoc's nature as a document conversion tool, the following security considerations are particularly relevant and tailored:

  1. Input Validation is Paramount: Robust input validation in Format Readers is the most critical security control. Pandoc must rigorously validate all input documents against the expected format specifications. This includes:

    • Format Conformance: Verifying that the input document adheres to the basic structure and syntax of the declared format.
    • Schema Validation (where applicable): For formats with schemas (e.g., XML-based formats), validate against the schema to detect malformed or malicious structures.
    • Content Validation: Validate the content within the document, such as allowed tags, attributes, and data types, to prevent unexpected or malicious content.
    • Size and Complexity Limits: Implement limits on document size, nesting depth, and other complexity metrics to prevent DoS attacks based on resource exhaustion during parsing.

  2. Secure Parsing Logic for Each Format: Each Format Reader must implement secure parsing logic, specifically designed to mitigate format-specific vulnerabilities. This requires:

    • Vulnerability Awareness: Developers of Format Readers must be aware of common vulnerabilities associated with each document format (e.g., XXE in XML, macro vulnerabilities in DOCX, etc.).
    • Safe Parsing Libraries: Utilize secure and well-maintained parsing libraries where possible. If custom parsing logic is necessary, it must be implemented with extreme care and security in mind.
    • Regular Security Audits of Parsing Code: Parsing code should be regularly reviewed and audited for potential vulnerabilities, especially when new formats are added or existing formats are updated.

  3. Output Sanitization and Encoding: Format Writers must properly sanitize and encode output content to prevent injection vulnerabilities in the generated documents. This is especially important for formats that can contain executable content or scripts (e.g., HTML, potentially others).

    • Context-Aware Encoding: Use context-aware encoding techniques to ensure that output content is safe within the target format. For example, when generating HTML, use HTML entity encoding for text content to prevent XSS.
    • Content Security Policies (CSP) for HTML Output (If Applicable): If Pandoc is ever used in contexts where HTML output is directly served to web browsers, consider generating appropriate Content Security Policy headers to further mitigate XSS risks.

  4. Dependency Management and Security: Pandoc relies on Haskell packages and potentially external libraries for parsing and generating various document formats. Secure dependency management is crucial:

    • Dependency Scanning: Implement automated dependency scanning to identify known vulnerabilities in third-party libraries.
    • Regular Dependency Updates: Keep dependencies up-to-date with the latest security patches.
    • Vulnerability Assessment of Dependencies: Before incorporating new dependencies, assess their security posture and history of vulnerabilities.

  5. Resource Limits and DoS Protection: Pandoc should implement resource limits to protect against DoS attacks. This includes:

    • Timeouts for Parsing and Conversion: Set timeouts for parsing and conversion processes to prevent them from running indefinitely on maliciously crafted documents.
    • Memory Limits: Implement mechanisms to limit the memory consumption during parsing and conversion to prevent memory exhaustion attacks.
    • File Size Limits: Enforce reasonable limits on the size of input documents to prevent excessively large files from causing resource exhaustion.

  6. Vulnerability Disclosure and Response Process: A clear and well-publicized vulnerability disclosure and response process is essential for an open-source project like Pandoc. This includes:

    • Security Policy: Publish a security policy outlining how users can report vulnerabilities.
    • Dedicated Security Contact: Establish a dedicated email address or channel for security reports.
    • Response SLA: Define a Service Level Agreement (SLA) for acknowledging and responding to security reports.
    • Patch Management and Release Process: Have a process for developing, testing, and releasing security patches promptly.

5. Actionable and Tailored Mitigation Strategies

Based on the identified security considerations, here are actionable and tailored mitigation strategies for Pandoc:

a) Enhance Input Validation in Format Readers:

  • Action: For each Format Reader, conduct a thorough review of input validation logic.
  • Specific Implementation:
    • Implement stricter format conformance checks based on format specifications.
    • Integrate schema validation for XML-based formats using robust schema validation libraries in Haskell.
    • Add content validation rules to restrict allowed tags, attributes, and data types based on the expected format and Pandoc's processing capabilities.
    • Implement size and complexity limits (e.g., maximum file size, nesting depth) within Format Readers to prevent DoS.
    • Consider using parsing libraries that offer built-in validation features and security hardening options.

b) Implement Automated Fuzzing for Format Readers (Recommended Control - Reinforce):

  • Action: Set up an automated fuzzing infrastructure specifically targeting Format Readers.
  • Specific Implementation:
    • Utilize fuzzing tools suitable for Haskell or capable of fuzzing native code if Format Readers use external C libraries.
    • Generate a diverse corpus of valid, malformed, and malicious documents for each supported input format.
    • Integrate fuzzing into the CI/CD pipeline to run regularly and automatically detect parsing vulnerabilities.
    • Focus fuzzing efforts on complex and historically problematic document formats first.
    • Analyze crash reports and code coverage from fuzzing to identify and fix vulnerabilities effectively.

c) Integrate Static Application Security Testing (SAST) Tools (Recommended Control - Implement):

  • Action: Integrate SAST tools into the build process to automatically detect code-level security flaws in Pandoc's Haskell code.
  • Specific Implementation:
    • Choose SAST tools that are effective for Haskell code analysis and can identify common vulnerability patterns (e.g., potential injection points, insecure data handling).
    • Configure SAST tools to focus on Format Readers and Writers, as these are the most security-sensitive components.
    • Integrate SAST into the CI/CD pipeline to run on every code commit and pull request.
    • Establish a process for reviewing and triaging SAST findings, prioritizing security-critical issues.

d) Implement Dependency Scanning (Recommended Control - Implement):

  • Action: Implement automated dependency scanning to identify and manage vulnerabilities in third-party Haskell packages and any external libraries used by Pandoc.
  • Specific Implementation:
    • Utilize dependency scanning tools that can analyze Haskell project dependencies (e.g., tools that integrate with Stack or Cabal).
    • Integrate dependency scanning into the CI/CD pipeline to run regularly and alert developers to vulnerable dependencies.
    • Establish a process for monitoring dependency scan results, prioritizing critical vulnerabilities, and updating dependencies promptly.
    • Consider using tools that can automatically create pull requests to update vulnerable dependencies.

e) Enhance Output Sanitization in Format Writers:

  • Action: Review and enhance output sanitization and encoding logic in all Format Writers, especially for formats like HTML, EPUB, and potentially others that can contain active content.
  • Specific Implementation:
    • Implement context-aware encoding for all output formats. For HTML, ensure proper HTML entity encoding for text content.
    • For formats that support scripting or macros, carefully consider whether to disable these features by default or implement robust sanitization to prevent malicious scripts or macros from being injected.
    • For HTML output, consider options to generate Content Security Policy (CSP) headers if Pandoc is used in web-related contexts.
    • Regularly review and update sanitization logic as new output formats are added or existing formats evolve.

f) Establish a Clear Vulnerability Disclosure and Response Process (Recommended Control - Implement):

  • Action: Formalize and publicize a vulnerability disclosure and response process for Pandoc.
  • Specific Implementation:
    • Create a security policy document and publish it on the Pandoc website and GitHub repository.
    • Set up a dedicated email address (e.g., [email protected]) for security vulnerability reports.
    • Define an SLA for acknowledging and responding to security reports (e.g., acknowledge within 24-48 hours, provide initial assessment within a week).
    • Establish a process for triaging, fixing, testing, and releasing security patches.
    • Communicate security advisories clearly and promptly to users when vulnerabilities are fixed.

g) Implement Resource Limits (DoS Protection):

  • Action: Implement resource limits to protect against Denial of Service attacks.
  • Specific Implementation:
    • Set reasonable timeouts for parsing and conversion operations within the Pandoc CLI or within individual Format Readers.
    • Implement memory usage limits to prevent excessive memory consumption during processing. Haskell's runtime might provide some inherent memory management, but explicit limits might still be necessary.
    • Enforce file size limits for input documents at the Pandoc CLI level.

By implementing these tailored mitigation strategies, the Pandoc development team can significantly enhance the security posture of this valuable document conversion tool and better protect its users from potential security threats. Remember that security is an ongoing process, and continuous monitoring, testing, and improvement are essential.