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attack-surface.md

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Attack Surface Analysis for docusealco/docuseal

Attack Surface: Malicious File Upload

  • Description: Attackers upload malicious files to the application server.
  • Docuseal Contribution: Docuseal's core functionality is document uploads for signing workflows. This inherently creates an upload endpoint that is a primary target. Without Docuseal's document-centric nature, this attack surface would be less prominent.
  • Example: An attacker uploads a PDF file containing a JavaScript payload. When the server attempts to process or render this PDF (a core Docuseal function), the JavaScript executes, potentially leading to Remote Code Execution (RCE) on the server.
  • Impact: Remote Code Execution, Server Compromise, Data Breach, Denial of Service.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developers:
      • Input Validation: Implement strict file type validation (allowlist approach - only permit specific, necessary file types).
      • File Size Limits: Enforce reasonable file size limits to prevent resource exhaustion.
      • Content Security Policy (CSP): Implement CSP headers to mitigate client-side execution of malicious scripts from uploaded files.
      • Secure File Storage: Store uploaded files outside the webroot and with restricted permissions.
      • Antivirus/Malware Scanning: Integrate with antivirus or malware scanning solutions to scan uploaded files before processing.
      • Sandboxed Processing: Process and render documents in a sandboxed environment to limit the impact of potential exploits in document processing libraries.

Attack Surface: Vulnerabilities in Document Processing Libraries

  • Description: Exploiting vulnerabilities within libraries used by Docuseal to parse and render document formats (e.g., PDF, DOCX).
  • Docuseal Contribution: Docuseal directly relies on document processing libraries to handle various document formats. This dependency is essential for Docuseal's operation and introduces the risk of vulnerabilities within these libraries.
  • Example: A vulnerability (e.g., buffer overflow) exists in the PDF parsing library used by Docuseal. An attacker crafts a malicious PDF that triggers this vulnerability when processed by the server (a core Docuseal action), leading to RCE.
  • Impact: Remote Code Execution, Server Compromise, Denial of Service.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developers:
      • Library Updates: Regularly update all document processing libraries to the latest versions to patch known vulnerabilities.
      • Vulnerability Scanning: Implement automated vulnerability scanning for dependencies to identify and address vulnerable libraries proactively.
      • Library Selection: Choose well-maintained and reputable document processing libraries with a strong security track record.
      • Sandboxed Processing: As mentioned before, process documents in a sandboxed environment.

Attack Surface: Cross-Site Scripting (XSS) via Document Content

  • Description: Injecting malicious scripts into document content that are then executed in other users' browsers when they view the document within Docuseal.
  • Docuseal Contribution: Docuseal's primary function is to display document content to users for review and signing. This display mechanism, if not secured, becomes a direct pathway for XSS attacks originating from document content.
  • Example: An attacker uploads a document containing malicious JavaScript embedded within the document text or metadata. When another user views this document in Docuseal (a standard Docuseal workflow step), the JavaScript executes in their browser, potentially stealing session cookies or redirecting them to a phishing site.
  • Impact: Session Hijacking, Data Theft, Account Takeover, Defacement.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Output Encoding/Escaping: Implement robust output encoding/escaping of document content before displaying it in the browser. Use context-aware encoding appropriate for HTML, JavaScript, and CSS.
      • Content Security Policy (CSP): Implement a strict CSP to limit the sources from which scripts can be loaded and executed, reducing the impact of XSS.
      • HTML Sanitization Libraries: Utilize well-vetted HTML sanitization libraries to remove potentially malicious HTML tags and attributes from document content before display.

Attack Surface: Insecure Document Storage

  • Description: Documents are stored without proper encryption at rest, making them vulnerable if the storage system is compromised.
  • Docuseal Contribution: Docuseal must store uploaded documents persistently to manage workflows and provide access to signed documents. This storage requirement directly introduces the risk of data breaches if storage is not properly secured.
  • Example: An attacker gains unauthorized access to the server's file system or database where Docuseal stores documents. Because the documents are not encrypted, the attacker can directly access and read sensitive information contained within them, compromising the confidentiality of documents managed by Docuseal.
  • Impact: Data Breach, Confidentiality Violation, Compliance Issues.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Encryption at Rest: Implement encryption at rest for document storage. Use strong encryption algorithms and securely manage encryption keys (e.g., using a Hardware Security Module or Key Management System).
      • Access Control Lists (ACLs): Implement strict access control lists on the storage system to limit access to only authorized processes and users.
      • Secure Storage Location: Store documents in a secure location, separate from the web application's public directory.

Attack Surface: Insufficient Access Control

  • Description: Weak or improperly implemented access control allows unauthorized users to access, modify, or delete documents or workflow data.
  • Docuseal Contribution: Docuseal manages document workflows and user access to documents and workflow stages. Effective access control is fundamental to Docuseal's security model and the confidentiality and integrity of documents within its system.
  • Example: A user with "viewer" permissions is able to manipulate the application to directly access and download documents intended only for "signer" roles, bypassing intended access restrictions within Docuseal's workflow.
  • Impact: Unauthorized Access, Data Breach, Data Manipulation, Privilege Escalation.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Role-Based Access Control (RBAC): Implement a robust RBAC system to define and enforce user permissions based on roles.
      • Principle of Least Privilege: Grant users only the minimum necessary permissions required for their tasks.
      • Authorization Checks: Perform thorough authorization checks at every access point, both at the UI level and in the backend code.
      • Secure Direct Object References: Avoid exposing internal object IDs directly in URLs or client-side code. Use indirect references or access control mechanisms to prevent unauthorized access based on predictable IDs.

Attack Surface: Weak Signature Verification

  • Description: Using weak cryptographic algorithms or improper implementation of signature verification can lead to forged or invalid signatures being accepted.
  • Docuseal Contribution: Docuseal's core value proposition is digital document signing. Robust signature verification is paramount to ensure the integrity, authenticity, and non-repudiation of documents signed using Docuseal. Weaknesses here directly undermine Docuseal's purpose.
  • Example: Docuseal uses an outdated hashing algorithm for digital signatures that is vulnerable to collision attacks. An attacker can create a second, malicious document with the same signature hash as a legitimate document, effectively forging a valid signature within the Docuseal signing process.
  • Impact: Forged Signatures, Non-Repudiation Failure, Legal and Financial Risks.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers:
      • Strong Cryptographic Algorithms: Use strong and up-to-date cryptographic algorithms for digital signatures (e.g., SHA-256 or stronger hashing, RSA or ECDSA with appropriate key lengths).
      • Proper Signature Verification Implementation: Implement signature verification according to best practices and security guidelines for the chosen algorithms. Use established cryptographic libraries correctly.
      • Regular Security Audits: Conduct regular security audits of the signature verification process and cryptographic implementations.
      • Timestamping: Implement timestamping to provide proof of when a document was signed, further strengthening non-repudiation.