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Security: Gongchampou/SignvalidGov

Security

security.md

SignValid Security Architecture & Threat Defense

Classification: Comprehensive Technical Security Documentation
Target System: SignValid (Universal Indian Digital Signature Validator & Stamping Engine)
Architecture Model: 100% Client-Side In-Memory (Zero-Trust / Zero-Knowledge)
Regulatory Adherence: Information Technology Act, 2000 (Republic of India) · ISO 32000-1 · RFC 5280 · RFC 3161

1. Executive Summary & Core Security Guarantees

SignValid is architected from the ground up on a Zero-Knowledge, 100% Ephemeral Client-Side execution paradigm. Traditional document verification portals upload user documents to centralized servers, introducing critical attack surfaces including cloud data breaches, man-in-the-middle interception, unauthorized telemetry, and permanent database retention of sensitive citizen records (e-Aadhaar, PAN cards, income and caste certificates).

SignValid eliminates the server from the security boundary entirely:

[ User Browser / Device ] <====== No Server Uploads ======> [ External Internet ]
         │
         ├── 1. In-Memory Ephemeral RAM Processing
         ├── 2. Native WebCrypto & PKI.js Cryptography
         ├── 3. Bundled CCA India Official Root Store
         └── 4. Ephemeral Garbage Collection on Reset

Core Security Tenets:

  1. Zero Remote Transmission: PDF bytes are never transmitted across the network. All parsing, hashing, signature validation, and PDF stamping execute locally within the browser engine.
  2. Zero Disk / Storage Persistence: Documents, private certificates, signatures, and document passwords are never written to localStorage, sessionStorage, IndexedDB, WebSQL, or cookies.
  3. Hardware-Accelerated WebCrypto: SHA-256 digests and RSA/ECDSA mathematical operations execute via browser native window.crypto.subtle primitives.
  4. Strict Isolation & Outbound Blocking: A strict Content Security Policy (CSP) with connect-src 'self' ws: wss: and object-src 'none' prevents unauthorized network exfiltration.

2. Threat Modeling & Cyber Attack Surface Analysis

The following threat matrix documents all audited cyber attack vectors, potential hacker exploits, and SignValid's corresponding defense-in-depth countermeasures:

Threat Category Potential Attack Vector / Exploit Risk Level SignValid Defense & Countermeasure Implementation Reference
Data Exfiltration Malicious browser extension, supply-chain attack, or rogue third-party script exfiltrating uploaded government documents. Critical Zero network transmission architecture; strict Content-Security-Policy (CSP) blocking external outbound network requests (connect-src); strictly ephemeral memory buffers. index.html
src/App.tsx
Polyglot & File Masquerading Hacker uploads HTML, PHP, shell scripts, or executable binaries masquerading with .pdf extension to exploit browser parsers. High Multi-tier file inspection: MIME type checking, 1024-byte magic byte detection (%PDF-), rejection of HTML/XML/script tokens in file header. src/security/sanitizer.ts
validatePdfBytes()
Stored DOM XSS Adversary crafts a fraudulent certificate with embedded JavaScript payloads in X.509 fields (e.g. CN=<script>alert(1)</script>). High Mandatory input sanitization stripping ASCII control codes (\x00-\x1F), encoding HTML entities (<>&"'), and React virtual DOM automatic escaping. src/security/sanitizer.ts
sanitizeCertString()
Denial of Service (DoS / ReDoS) Maliciously crafted PDF with recursive dictionary loops, zip compression bombs, or endless cross-reference tables causing tab freeze. Medium Strict 25-second operation timeout promise wrapper; 25 MB file size limit; recursive depth boundaries on ASN.1 parsing and appearance streams. src/security/sanitizer.ts
runWithSecurityTimeout()
Client-Side Abuse & Brute-Force Automated scripts or bots rapidly testing passwords or flooding local execution to cause browser crashes. Medium Sliding-window rate limiter enforcing 1,000ms minimum interval throttle and a maximum of 6 certificate verifications per 60-second window. src/security/rateLimiter.ts
securityRateLimiter
Clickjacking / UI Redressing Adversarial website embeds SignValid in a transparent <iframe> to trick users into dragging files or authorizing downloads. Medium Strict X-Frame-Options: DENY, frame-ancestors 'none' in CSP, and real-time inline JavaScript anti-clickjacking framebuster defense. index.html
#antiClickjack
Cryptographic Signature Forgery Attacker tampers with document content while preserving the signature block or forging untrusted root certificates. Critical Exact byte-range digest verification against PKCS#7 messageDigest; public key signature verification; hierarchical certificate path chaining to official CCA India 2014 & 2022 roots. src/verify/verifyPdf.ts
verifyOne(), buildChain()
Path Traversal / Filename Injection Malicious PDF naming (e.g. ../../payload.exe or %00evil.pdf) exploiting browser file saving mechanisms. Low Regex sanitization of download filenames stripping path delimiters (/, \), control characters, and reserved system characters, enforcing .pdf suffix. src/verify/stampPdf.ts
downloadBytes()
Memory / Cache Residuals Document passwords or sensitive decrypted bytes lingering in memory or disk cache after session completion. Medium Ephemeral React state storage; explicit manual and automatic password clearing; explicit URL.revokeObjectURL() invocation after 2,000ms. src/verify/stampPdf.ts
src/components/ResultsCard.tsx

3. Five-Tier Defense-in-Depth Architecture

graph TD
    subgraph TIER1["Tier 1: Boundary & Ingress Defense"]
        A[File Upload / Drag & Drop] --> B[MIME & Extension Validation]
        B --> C[Rate Limiter: 1 req/sec & max 6 certs/min]
        C --> D[Magic Byte Header Scan: %PDF- and Anti-Polyglot]
    end

    subgraph TIER2["Tier 2: Ephemeral Sandbox"]
        D --> E[ArrayBuffer Memory Allocation]
        E --> F[25-Second Execution Timeout Guard]
        F --> G[Password Sanitizer: 64 char max, no CRLF]
    end

    subgraph TIER3["Tier 3: Cryptographic Verification Core"]
        G --> H["Extract /ByteRange & /Contents (PKCS#7)"]
        H --> I["WebCrypto SHA-256 Digest of Document Bytes"]
        I --> J["Verify messageDigest Integrity in SignedAttrs"]
        J --> K["Verify RSA / ECDSA Cryptographic Signature"]
        K --> L["Walk Certificate Chain to Bundled CCA India Roots"]
    end

    subgraph TIER4["Tier 4: Safe Transformation & Rendering"]
        L --> M[Sanitize X.509 Subject & Issuer Strings]
        M --> N[Embed Vector 3D Drop-Shadow Green Tick]
        N --> O[PDF ISO 32000-1 Standards-Compliant Stamping]
    end

    subgraph TIER5["Tier 5: Egress Control & Browser Hardening"]
        O --> P[Sanitize Output Filename]
        P --> Q[Generate Blob URL & Auto-Revoke after 2s]
        Q --> R[Strict CSP: Block Remote Outbound Transmission]
        R --> S[Anti-Clickjacking Framebuster: X-Frame-Options DENY]
    end

    classDef ingress fill:#EFF6FF,stroke:#3B82F6,stroke-width:1.5px;
    classDef sandbox fill:#F0FDF4,stroke:#16A34A,stroke-width:1.5px;
    classDef crypto fill:#FEF3C7,stroke:#D97706,stroke-width:1.5px;
    classDef render fill:#FAF5FF,stroke:#9333EA,stroke-width:1.5px;
    classDef egress fill:#FEF2F2,stroke:#DC2626,stroke-width:1.5px;

    class A,B,C,D ingress;
    class E,F,G sandbox;
    class H,I,J,K,L crypto;
    class M,N,O render;
    class P,Q,R,S egress;
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4. End-to-End Cryptographic Verification Flow

The flowchart below demonstrates the mathematical and cryptographic verification lifecycle performed per signature in accordance with ISO 32000-1 (PDF Advanced Electronic Signatures) and the Information Technology Act, 2000:

flowchart TD
    Start([User Drops PDF]) --> Step1[Parse Raw PDF Byte Stream]
    Step1 --> Step2{Locate /ByteRange Array<br/>0, len1, len1+len2, len3}
    
    Step2 -- Not Found --> UnsignedDoc[Mark as Unsigned PDF<br/>Missing Cryptographic Dictionary]
    Step2 -- Found --> Step3[Extract Raw PKCS#7 / CMS<br/>DER Hex Stream from /Contents]
    
    Step3 --> Step4[Parse ASN.1 Structure via asn1js<br/>Extract SignedData & SignerInfos]
    
    Step4 --> Step5["Compute Document Digest<br/>SHA-256 across Range [0..len1] + [len1+len2..len3]"]
    
    Step5 --> Step6{"Compare Digest with CMS<br/>messageDigest Signed Attribute"}
    Step6 -- Mismatch --> Tampered[Status: INVALID<br/>Document altered after signing]
    Step6 -- Match --> Step7[Integrity Verified: Document Untampered]
    
    Step7 --> Step8["Verify Public Key Signature<br/>RSA / ECDSA mathematical check"]
    Step8 -- Invalid --> SigFail[Status: INVALID<br/>Signature math validation failed]
    Step8 -- Valid --> Step9[Signature Mathematics Verified]
    
    Step9 --> Step10[Extract Leaf Signer Certificate]
    Step10 --> Step11{"Check Validity Period<br/>at Signing Timestamp"}
    Step11 -- Expired/Not Yet Valid --> ExpiredCert[Problem: Certificate not valid at signing time]
    Step11 -- Valid --> Step12[Traverse Intermediate CA Certificates]
    
    Step12 --> Step13{"Is Issuer Anchored to<br/>CCA India Official Root Store?<br/>(2014 / 2022)"}
    
    Step13 -- No Path to Root --> Untrusted[Status: UNTRUSTED<br/>Signer intact but CA not accredited]
    Step13 -- Verified to Root --> Step14{"Does Signature Cover<br/>Whole Document?<br/>(No appended bytes)"}
    
    Step14 -- Appended Bytes Found --> ModifiedDoc[Status: MODIFIED<br/>Signatures intact but data appended]
    Step14 -- Covers Document --> ValidDoc[Status: VALID<br/>Authentic Indian Digital Signature]
    
    ValidDoc --> StampPhase[Generate Verified Display Copy<br/>Inject 3D Green Tick Vector & Audit Note]
    StampPhase --> End([Safe In-Browser Download])

    classDef pass fill:#DCFCE7,stroke:#15803D,stroke-width:2px;
    classDef fail fill:#FEE2E2,stroke:#DC2626,stroke-width:2px;
    classDef warn fill:#FEF3C7,stroke:#D97706,stroke-width:2px;
    classDef process fill:#F8FAFC,stroke:#475569,stroke-width:1.5px;

    class ValidDoc,Step7,Step9 pass;
    class Tampered,SigFail,ExpiredCert fail;
    class UnsignedDoc,Untrusted,ModifiedDoc warn;
    class Start,Step1,Step2,Step3,Step4,Step5,Step6,Step8,Step10,Step11,Step12,Step13,Step14,StampPhase,End process;
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5. Security Engine Implementation Details

5.1. Input Sanitization & Anti-Polyglot Defense (src/security/sanitizer.ts)

  • Magic Byte Verification: Inspects the first 1,024 bytes of any dropped file for the required %PDF- signature. Rejects polyglot exploits disguised as PDFs containing HTML tags (<html, <script, <!doctype, <?xml).
  • ASN.1 Certificate String Sanitization (sanitizeCertString): Strips ASCII control codes (\x00-\x1F) and encodes HTML entities (<, >, &, ", ') before certificate attributes (e.g. Common Name, Organization, Issuer) reach React presentation layers.
  • Password Boundary Enforcement: Unlocking passwords for encrypted PDFs (e.g., e-Aadhaar passwords) are sanitized to a strict 64-character ceiling, stripped of carriage returns, line feeds, and null bytes (\r\n\t\0).
  • Cryptographic Timeout Guard (runWithSecurityTimeout): Enforces a 25,000ms hard deadline on all cryptographic verification tasks. Maliciously crafted decompression bombs or exponential parser traversals automatically reject without freezing the browser thread.

5.2. Client-Side Rate Limiter & Throttling (src/security/rateLimiter.ts)

  • Action Throttle: Enforces a minimum 1,000ms pause between consecutive verification actions to mitigate tab thread starvation.
  • Sliding-Window Ceiling: Enforces an upper limit of 6 certificates per 60-second sliding window. Batches exceeding this threshold are automatically queued or throttled with actionable remaining cooldown countdowns.

5.3. Trust Anchor Registry (src/certs/ccaRoots.ts)

SignValid embeds the official, cryptographically verified Root Certificates issued by the Controller of Certifying Authorities (CCA), Ministry of Electronics and Information Technology (MeitY), Government of India:

  • CCA India 2014 Root: RSA 2048-bit, SHA-256 root certificate.
  • CCA India 2022 Root: RSA 4096-bit, SHA-256 root certificate.

All intermediate certifying authorities (e-Mudhra, National Informatics Centre [NICCA], Capricorn, NSDL/Protean, VSign, IDRBT, CDAC, SafeScrypt) must mathematically chain to these authoritative trust anchors.

5.4. Content Security Policy (CSP) & Clickjacking Defense (index.html)

SignValid declares modern defensive HTTP equivalence headers:

<!-- Content Security Policy: Blocks all outbound exfiltration and unauthorized sources -->
<meta http-equiv="Content-Security-Policy" content="
  default-src 'self';
  script-src 'self' 'unsafe-inline' blob:;
  worker-src 'self' blob:;
  style-src 'self' 'unsafe-inline' https://fonts.googleapis.com;
  font-src 'self' https://fonts.gstatic.com data:;
  img-src 'self' data: blob: https://signvalid.pages.dev;
  connect-src 'self' ws: wss:;
  object-src 'none';
  frame-ancestors 'none';
" />

<!-- MIME Type Sniffing & Framing Defense -->
<meta http-equiv="X-Frame-Options" content="DENY" />
<meta http-equiv="X-Content-Type-Options" content="nosniff" />
<meta name="referrer" content="strict-origin-when-cross-origin" />

6. Indian IT Act 2000 Compliance Architecture

Under the Information Technology Act, 2000 of India:

  1. Section 3 (Authentication of Electronic Records): Requires electronic records to be authenticated by digital signatures utilizing asymmetric cryptosystems and hash functions. SignValid independently checks SHA-256 / SHA-1 message digests against the original byte ranges.
  2. Section 4 (Legal Recognition of Electronic Records): Mandates that electronic signatures generated through accredited Certifying Authorities under the CCA hierarchy possess the same legal validity as physical handwritten signatures.
  3. PAdES / ISO 32000-1 Standards: SignValid adheres strictly to PDF Reference standard ISO 32000-1 for signature verification, dictionary parsing, and visual appearance streams without corrupting underlying document structural integrity.

7. Vulnerability Disclosure Policy

SignValid operates under a coordinated vulnerability disclosure program. If you discover a security vulnerability, flaw in cryptographic verification, or potential bypass:

  • Contact: security@signvalid.pages.dev / GitHub Issues
  • Response SLA: Initial acknowledgment within 24 hours; technical analysis and mitigation roadmap within 72 hours.
  • Scope: Client-side cryptography, input sanitization, rate limiting, and memory isolation.

Document Version: 1.0.0 · Maintained by SignValid Security Operations

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