492 lines
23 KiB
Markdown
492 lines
23 KiB
Markdown
# Authentication API Documentation
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## Overview
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The nostr_core_lib unified request validation system provides a comprehensive authentication and authorization framework for Nostr-based applications. It combines Nostr event validation with flexible rule-based authentication in a single API call.
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## Authentication Flow and Order of Operations
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### Authentication Flow Diagram
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```
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┌─────────────────────┐
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│ Request Received │
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└──────────┬──────────┘
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│
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▼
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┌─────────────┐ ╔═══════════════════╗
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│ Input Valid?├─No─►║ REJECT: Invalid ║
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└──────┬──────┘ ║ Input (~1μs) ║
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│Yes ╚═══════════════════╝
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▼
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┌─────────────┐ ╔═══════════════════╗
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│System Init? ├─No─►║ REJECT: Not ║
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└──────┬──────┘ ║ Initialized ║
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│Yes ╚═══════════════════╝
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▼
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┌─────────────┐
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│Auth Header? │
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└──────┬──────┘
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│Yes
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▼ ┌─────────────────────┐
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┌─────────────┐ No │ │
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│Parse Header ├────────────┤ Skip Nostr │
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└──────┬──────┘ │ Validation │
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│ │ │
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▼ └──────────┬──────────┘
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┌─────────────┐ ╔═══════════════════╗ │
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│Valid Base64?├─No─►║ REJECT: Malformed ║ │
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└──────┬──────┘ ║ Header (~10μs) ║ │
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│Yes ╚═══════════════════╝ │
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▼ │
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┌─────────────┐ ╔═══════════════════╗ │
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│Valid JSON? ├─No─►║ REJECT: Invalid ║ │
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└──────┬──────┘ ║ JSON (~50μs) ║ │
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│Yes ╚═══════════════════╝ │
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▼ │
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┌─────────────┐ ╔═══════════════════╗ │
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│Valid Struct?├─No─►║ REJECT: Invalid ║ │
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└──────┬──────┘ ║ Structure (~100μs)║ │
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│Yes ╚═══════════════════╝ │
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▼ │
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┌─────────────────┐ ╔═══════════════════╗ │
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│ ECDSA Signature │No ║ REJECT: Invalid ║ │
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│ Verify (~2ms) ├──►║ Signature (~2ms) ║ │
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└─────────┬───────┘ ╚═══════════════════╝ │
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│Yes │
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▼ │
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┌─────────────────┐ ╔═══════════════════╗ │
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│Operation Match? │No ║ REJECT: Unauth. ║ |
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└─────────┬───────┘ ║ Operation (~200μs)║ │
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│Yes ╚═══════════════════╝ │
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▼ │
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┌─────────────────┐ ╔═══════════════════╗ │
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│Event Expired? │Yes║ REJECT: Expired ║ │
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└─────────┬───────┘ ║ Event (~50μs) ║ │
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│No ╚═══════════════════╝ │
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▼ │
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┌─────────────────┐ │
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│Extract Pubkey │ │
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└─────────┬───────┘ │
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│ │
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▼◄───────────────────────────────────────┘
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┌─────────────────┐ ╔═══════════════════╗
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│Auth Rules │ No ║ ALLOW: Rules ║
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│Enabled? ├────►║ Disabled ║
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└─────────┬───────┘ ╚═══════════════════╝
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│Yes
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▼
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┌─────────────────┐
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│Generate Cache │
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│Key (SHA-256) │
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└─────────┬───────┘
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│
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│Cache Hit? │ Yes ║ RETURN: Cached ║
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│(~100μs lookup) ├────►║ Decision (~100μs) ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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╔═══════════════════════════════════════╗
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║ RULE EVALUATION ENGINE ║
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║ (Priority Order) ║
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╚═══════════════════════════════════════╝
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│
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│1. Pubkey │ Yes ║ DENY: Pubkey ║
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│ Blacklisted? ├────►║ Blocked ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│2. Hash │ Yes ║ DENY: Hash ║
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│ Blacklisted? ├────►║ Blocked ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│3. MIME Type │ Yes ║ DENY: MIME ║
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│ Blacklisted? ├────►║ Blocked ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│4. Size Limit │ Yes ║ DENY: File ║
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│ Exceeded? ├────►║ Too Large ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│5. Pubkey │ Yes ║ ALLOW: Pubkey ║
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│ Whitelisted? ├────►║ Whitelisted ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│6. MIME Type │ Yes ║ ALLOW: MIME ║
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│ Whitelisted? ├────►║ Whitelisted ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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┌─────────────────┐ ╔═══════════════════╗
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│Whitelist Rules │ Yes ║ DENY: Not in ║
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│Exist? ├────►║ Whitelist ║
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└─────────┬───────┘ ╚═══════════════════╝
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│No
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▼
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╔═══════════════════╗
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║ ALLOW: Default ║
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║ Allow Policy ║
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╚═══════════════════╝
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│
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▼
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┌─────────────────┐
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│ Cache Decision │
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│ (5min TTL) │
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└─────────┬───────┘
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│
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▼
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┌─────────────────┐
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│ Return Result │
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│ to Application │
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└─────────────────┘
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```
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### Performance Timeline (ASCII)
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```
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Fast Path (Cache Hit) - Total: ~101μs
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┌─────┬─────────────────────────────────────────────────────────────────┬──────┐
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│ 1μs │ 100μs Cache Lookup │ 1μs │
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└─────┴─────────────────────────────────────────────────────────────────┴──────┘
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Input │ │ Return
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Valid │ SQLite SELECT │ Result
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Typical Path (Valid Request) - Total: ~2.4ms
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┌──┬───┬────┬─────────────────────────┬────────┬────┬──┐
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│1μ│50μ│100μ│ 2000μs │ 200μs │100μ│1μ│
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└──┴───┴────┴─────────────────────────┴────────┴────┴──┘
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│ │ │ │ │ │ │
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│ │ │ │ ECDSA Signature │ Rule │Cache│Return
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│ │ │ │ Verification │ Eval │Store│Result
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│ │ │ │ (Most Expensive) │ │ │
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│ │ │
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│ │ JSON Parse
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│ Header Parse
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Input Validation
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Worst Case (Full Validation) - Total: ~2.7ms
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┌──┬───┬────┬─────────────────────────┬─────────┬────┬──┐
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│1μ│50μ│100μ│ 2000μs │ 500μs │100μ│1μ│
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└──┴───┴────┴─────────────────────────┴─────────┴────┴──┘
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│
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All 6 Rule Checks
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(Multiple DB Queries)
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```
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### Request Processing Flow (DDoS-Optimized)
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The authentication system is designed with **performance and DDoS protection** as primary concerns. Here's the exact order of operations:
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#### Phase 1: Input Validation (Immediate Rejection)
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1. **Null Pointer Checks** - Reject malformed requests instantly (lines 122-128)
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2. **Initialization Check** - Verify system is properly initialized
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3. **Basic Structure Validation** - Ensure required fields are present
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#### Phase 2: Nostr Event Validation (CPU Intensive)
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4. **Authorization Header Parsing** (lines 139-148)
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- Extract base64-encoded Nostr event from `Authorization: Nostr <base64>` header
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- Decode base64 to JSON (memory allocation + decoding)
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- **Early exit**: Invalid base64 or malformed header rejected immediately
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5. **JSON Parsing** (lines 150-156)
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- Parse Nostr event JSON using cJSON
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- **Early exit**: Invalid JSON rejected before signature verification
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6. **Nostr Event Structure Validation** (lines 159-166)
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- Validate event has required fields (kind, pubkey, sig, etc.)
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- Check event kind is 24242 for Blossom operations
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- **Early exit**: Invalid structure rejected before expensive crypto operations
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7. **Cryptographic Signature Verification** (lines 159-166)
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- **Most CPU-intensive operation** - ECDSA signature verification
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- Validates event authenticity using secp256k1
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- **Early exit**: Invalid signatures rejected before database queries
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8. **Operation-Specific Validation** (lines 169-178)
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- Verify event authorizes the requested operation (upload/delete/list)
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- Check required tags (t=operation, x=hash, expiration)
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- Validate timestamp and expiration
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- **Early exit**: Expired or mismatched events rejected
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9. **Public Key Extraction** (lines 181-184)
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- Extract validated public key from event for rule evaluation
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#### Phase 3: Authentication Rules (Database Queries)
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10. **Rules System Check** (line 191)
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- Quick config check if authentication rules are enabled
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- **Early exit**: If disabled, allow request immediately
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11. **Cache Lookup** (lines 1051-1054)
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- Generate SHA-256 cache key from request parameters
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- Check SQLite cache for previous decision
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- **Early exit**: Cache hit returns cached decision (5-minute TTL)
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12. **Rule Evaluation** (Priority Order - lines 1061-1094):
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- **a. Pubkey Blacklist** (highest priority) - Immediate denial if matched
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- **b. Hash Blacklist** - Block specific content hashes
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- **c. MIME Type Blacklist** - Block dangerous file types
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- **d. File Size Limits** - Enforce upload size restrictions
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- **e. Pubkey Whitelist** - Allow specific users (only if not denied above)
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- **f. MIME Type Whitelist** - Allow specific file types
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13. **Whitelist Default Denial** (lines 1097-1121)
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- If whitelist rules exist but none matched, deny request
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- Prevents whitelist bypass attacks
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14. **Cache Storage** (line 1124)
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- Store decision in cache for future requests (5-minute TTL)
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### DDoS Protection Features
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#### **Fail-Fast Design**
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- **Input validation** happens before any expensive operations
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- **Authorization header parsing** fails fast on malformed data
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- **JSON parsing** rejects invalid data before signature verification
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- **Structure validation** happens before cryptographic operations
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#### **Expensive Operations Last**
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- **Signature verification** only after structure validation
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- **Database queries** only after successful Nostr validation
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- **Cache prioritized** over database queries
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#### **Caching Strategy**
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- **SHA-256 cache keys** prevent cache pollution attacks
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- **5-minute TTL** balances performance with rule changes
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- **LRU eviction** prevents memory exhaustion
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- **Per-request caching** includes all parameters (pubkey, operation, hash, MIME, size)
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#### **Resource Limits**
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- **JSON parsing** limited to 4KB buffer size
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- **Cache entries** limited to prevent memory exhaustion
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- **Database connection pooling** (single connection with proper cleanup)
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- **String length limits** on all inputs
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#### **Attack Mitigation**
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- **Base64 bombs** - Limited decode buffer size (4KB)
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- **JSON bombs** - cJSON library handles malformed JSON safely
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- **Cache poisoning** - Cryptographic cache keys prevent collisions
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- **Rule bypass** - Whitelist default denial prevents unauthorized access
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- **Replay attacks** - Timestamp and expiration validation
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- **Hash collision attacks** - Full SHA-256 verification
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### Performance Characteristics
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#### **Best Case** (Cached Decision):
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1. Input validation: ~1μs
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2. Cache lookup: ~100μs (SQLite SELECT)
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3. **Total: ~101μs**
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#### **Worst Case** (Full Validation + Rule Evaluation):
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1. Input validation: ~1μs
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2. Base64 decoding: ~50μs
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3. JSON parsing: ~100μs
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4. Signature verification: ~2000μs (ECDSA)
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5. Database queries: ~500μs (6 rule checks)
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6. Cache storage: ~100μs
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7. **Total: ~2751μs (~2.7ms)**
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#### **Typical Case** (Valid Request, Rules Enabled):
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1. Full validation: ~2200μs
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2. Cache miss, 2-3 rule checks: ~200μs
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3. **Total: ~2400μs (~2.4ms)**
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### Security Order Rationale
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The rule evaluation order is specifically designed for security:
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1. **Blacklists First** - Immediate denial of known bad actors
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2. **Resource Limits** - Prevent resource exhaustion attacks
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3. **Whitelists Last** - Only allow after passing all security checks
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4. **Default Deny** - If whitelists exist but don't match, deny
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This ensures that even if an attacker bypasses one layer, subsequent layers will catch the attack.
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## Core API
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### Primary Function
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```c
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int nostr_validate_request(nostr_request_t* request, nostr_request_result_t* result);
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```
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This single function handles:
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- Nostr event signature validation
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- Event structure validation (required fields, timestamps)
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- Authentication rule evaluation
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- Public key extraction and validation
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### Request Structure
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```c
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typedef struct {
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const char* event_json; // Raw Nostr event JSON
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const char* app_id; // Application identifier ("ginxsom", "c-relay")
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const char* operation; // Operation type ("upload", "delete", "list")
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const char* content_hash; // SHA-256 hash for file operations (optional)
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const char* mime_type; // MIME type for upload operations (optional)
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size_t content_size; // File size for upload operations (0 if N/A)
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} nostr_request_t;
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```
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### Result Structure
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```c
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typedef struct {
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int is_valid; // 1 if request is valid, 0 otherwise
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int error_code; // Specific error code (see Error Codes)
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char error_message[512]; // Human-readable error description
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char pubkey[65]; // Extracted public key (hex, null-terminated)
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time_t timestamp; // Event timestamp
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char event_id[65]; // Event ID (hex, null-terminated)
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} nostr_request_result_t;
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```
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## Authentication Rules System
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The system supports priority-based authentication rules that are evaluated in order:
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### Rule Types
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1. **NOSTR_AUTH_RULE_PUBKEY_WHITELIST** - Allow specific public keys
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2. **NOSTR_AUTH_RULE_PUBKEY_BLACKLIST** - Block specific public keys
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3. **NOSTR_AUTH_RULE_HASH_BLACKLIST** - Block specific content hashes
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4. **NOSTR_AUTH_RULE_MIME_RESTRICTION** - Restrict allowed MIME types
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5. **NOSTR_AUTH_RULE_SIZE_LIMIT** - Enforce maximum file sizes
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### Rule Evaluation
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- Rules are processed by priority (lower numbers = higher priority)
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- First matching rule determines the outcome
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- ALLOW rules permit the request
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- DENY rules reject the request
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- If no rules match, the default action is ALLOW
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### Rule Caching
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The system includes an intelligent caching mechanism:
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- LRU (Least Recently Used) eviction policy
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- Configurable cache size (default: 1000 entries)
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- Cache keys based on pubkey + operation + content hash
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- Automatic cache invalidation when rules change
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## Database Backend
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### Pluggable Architecture
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The system uses a pluggable database backend interface:
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```c
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typedef struct {
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int (*init)(const char* connection_string, void** context);
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int (*get_rules)(void* context, const char* app_id,
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nostr_auth_rule_t** rules, int* count);
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int (*cleanup)(void* context);
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} nostr_db_backend_t;
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```
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### SQLite Implementation
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Default implementation uses SQLite with the following schema:
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```sql
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-- Authentication rules table (per application)
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CREATE TABLE auth_rules_[APP_ID] (
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id INTEGER PRIMARY KEY AUTOINCREMENT,
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priority INTEGER NOT NULL,
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rule_type INTEGER NOT NULL,
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action INTEGER NOT NULL,
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pattern TEXT,
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value_int INTEGER,
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created_at INTEGER DEFAULT (strftime('%s', 'now')),
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updated_at INTEGER DEFAULT (strftime('%s', 'now'))
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);
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```
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## Error Codes
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The system uses specific error codes for different failure scenarios:
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- **-50**: `NOSTR_AUTH_ERROR_INVALID_EVENT` - Malformed Nostr event
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- **-51**: `NOSTR_AUTH_ERROR_INVALID_SIGNATURE` - Invalid event signature
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- **-52**: `NOSTR_AUTH_ERROR_PUBKEY_BLOCKED` - Public key is blacklisted
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- **-53**: `NOSTR_AUTH_ERROR_HASH_BLOCKED` - Content hash is blacklisted
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- **-54**: `NOSTR_AUTH_ERROR_MIME_RESTRICTED` - MIME type not allowed
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- **-55**: `NOSTR_AUTH_ERROR_SIZE_EXCEEDED` - File size limit exceeded
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## Usage Examples
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### Basic Validation
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```c
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#include "nostr_core/request_validator.h"
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// Initialize the system (once per application)
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int result = nostr_request_validator_init("db/myapp.db", "myapp");
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if (result != 0) {
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fprintf(stderr, "Failed to initialize validator: %d\n", result);
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return -1;
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}
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// Validate a request
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nostr_request_t request = {
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.event_json = "{\"kind\":24242,\"pubkey\":\"abc123...\",\"sig\":\"def456...\"}",
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.app_id = "myapp",
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.operation = "upload",
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.content_hash = "sha256hash...",
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.mime_type = "text/plain",
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.content_size = 1024
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};
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nostr_request_result_t result;
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int status = nostr_validate_request(&request, &result);
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if (result.is_valid) {
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printf("Request authorized for pubkey: %s\n", result.pubkey);
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} else {
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printf("Request denied: %s (code: %d)\n", result.error_message, result.error_code);
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}
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```
|
|
|
|
### Ginxsom Integration
|
|
|
|
The ginxsom application has been updated to use this system:
|
|
|
|
```c
|
|
// Replace old authenticate_request_with_rules() calls with:
|
|
nostr_request_t auth_request = {
|
|
.event_json = event_json,
|
|
.app_id = "ginxsom",
|
|
.operation = "upload", // or "list", "delete"
|
|
.content_hash = calculated_hash,
|
|
.mime_type = detected_mime_type,
|
|
.content_size = file_size
|
|
};
|
|
|
|
nostr_request_result_t auth_result;
|
|
int auth_status = nostr_validate_request(&auth_request, &auth_result);
|
|
|
|
if (!auth_result.is_valid) {
|
|
printf("Status: 403\r\n");
|
|
printf("Content-Type: application/json\r\n\r\n");
|
|
printf("{\"error\":\"Authentication failed\",\"message\":\"%s\"}\n",
|
|
auth_result.error_message);
|
|
return;
|
|
}
|
|
|
|
// Use auth_result.pubkey for the authenticated public key
|
|
```
|
|
|