bitcoin-auth-diagnostics

# Bitcoin Auth Diagnostics

## Overview

This skill enables comprehensive diagnosis of bitcoin-auth authentication issues across client and server implementations. Use this skill when encountering token generation failures, signature verification errors, or integration problems with the bitcoin-auth library.

## When to Use This Skill

Use this skill when:
- Bitcoin auth token verification is failing
- Investigating "invalid signature" or "invalid token" errors
- Debugging integration with bitcoin-auth in APIs (especially Sigma Auth)
- Token generation produces unexpected results
- Time skew or timestamp-related authentication failures occur
- Body hash mismatches are suspected
- Scheme confusion between bsm and brc77 exists

## Bitcoin Auth Token Format

All bitcoin-auth tokens follow this pipe-delimited format:

```
pubkey|scheme|timestamp|requestPath|signature
```

**Components:**
- `pubkey`: Hex-encoded public key (66 characters)
- `scheme`: Either `bsm` (legacy) or `brc77` (recommended)
- `timestamp`: ISO8601 format (e.g., `2025-01-15T14:30:00.000Z`)
- `requestPath`: Full path including query parameters (e.g., `/api/endpoint?param=value`)
- `signature`: Base64-encoded signature

**Example valid token:**
```
02a1b2c3d4e5f6...|brc77|2025-01-15T14:30:00.123Z|/api/status|dGVzdHNpZ25hdHVyZQ==
```

## Diagnostic Workflow

### Step 1: Token Structure Validation

First, validate the token structure before checking cryptographic validity:

```typescript
import { parseAuthToken } from 'bitcoin-auth';

const token = "..."; // The failing token
const parsed = parseAuthToken(token);

if (!parsed) {
  console.error("FAILED: Token structure is invalid");
  // Check: Does token have exactly 5 pipe-delimited parts?
  const parts = token.split('|');
  console.log(`Token has ${parts.length} parts (expected 5)`);
  console.log("Parts:", parts);

  // Common issues:
  // - Missing parts (incomplete token)
  // - Extra pipes in requestPath or other fields
  // - Invalid scheme (not 'bsm' or 'brc77')
} else {
  console.log("✅ Token structure is valid");
  console.log("Parsed token:", parsed);
}
```

### Step 2: Component Validation

Validate each component individually:

```typescript
const { pubkey, scheme, timestamp, requestPath, signature } = parsed;

// Validate public key
console.log("Public key length:", pubkey.length); // Should be 66 chars
console.log("Public key starts with 02/03:", pubkey.startsWith('02') || pubkey.startsWith('03'));

// Validate scheme
console.log("Scheme:", scheme); // Must be 'bsm' or 'brc77'

// Validate timestamp
const tokenTime = new Date(timestamp);
console.log("Token timestamp:", tokenTime.toISOString());
console.log("Current time:", new Date().toISOString());
console.log("Age (minutes):", (Date.now() - tokenTime.getTime()) / 60000);
// Default timePad is 5 minutes - token older than 5 minutes will fail

// Validate request path
console.log("Request path:", requestPath);
// Must match EXACTLY including query parameters and their order

// Validate signature
console.log("Signature (base64):", signature);
console.log("Signature length:", signature.length);
```

### Step 3: Signature Verification

If structure is valid, diagnose verification failures:

```typescript
import { verifyAuthToken } from 'bitcoin-auth';
import type { AuthPayload } from 'bitcoin-auth';

const authPayload: AuthPayload = {
  requestPath: "/api/endpoint?param=value", // Must match token exactly
  timestamp: new Date().toISOString(),       // Server's current time
  body: requestBody // Optional, must match if token was signed with body
};

const isValid = verifyAuthToken(
  token,
  authPayload,
  5,        // timePad in minutes (default 5)
  'utf8'    // bodyEncoding: 'utf8', 'hex', or 'base64'
);

if (!isValid) {
  console.error("FAILED: Signature verification failed");

  // Diagnose specific failures:

  // 1. Request path mismatch
  if (parsed.requestPath !== authPayload.requestPath) {
    console.error("❌ Request path mismatch:");
    console.error("  Token path:", parsed.requestPath);
    console.error("  Verify path:", authPayload.requestPath);
    // Common issue: Query parameter order differs
  }

  // 2. Timestamp issues
  const tokenTimestamp = new Date(parsed.timestamp);
  const targetTime = new Date(authPayload.timestamp);
  targetTime.setMinutes(targetTime.getMinutes() + 5); // Add timePad
  if (tokenTimestamp > targetTime) {
    console.error("❌ Token timestamp too far in future");
    console.error("  Token time:", tokenTimestamp.toISOString());
    console.error("  Target time:", targetTime.toISOString());
  }

  // 3. Body hash mismatch
  if (authPayload.body) {
    console.log("Verifying with body present");
    console.log("  Body encoding:", 'utf8'); // Check encoding matches
    console.log("  Body length:", authPayload.body.length);
    // Try different encodings if utf8 fails
  }

  // 4. Scheme-specific issues
  if (parsed.scheme === 'bsm') {
    console.log("Using legacy BSM signature scheme");
    // BSM uses different signature format than BRC77
  } else {
    console.log("Using BRC77 signature scheme (recommended)");
  }
}
```

### Step 4: Common Integration Issues

Check for common integration mistakes:

**Server-side (verification):**
```typescript
// ❌ WRONG: Using token's timestamp (defeats the purpose)
const authPayload = {
  requestPath,
  timestamp: parsedToken.timestamp, // DON'T DO THIS
  body
};

// ✅ CORRECT: Use server's current time
const serverTime = new Date().toISOString();
const authPayload = {
  requestPath,
  timestamp: serverTime,
  body
};
```

**Client-side (generation):**
```typescript
// ✅ Token generation
import { getAuthToken } from 'bitcoin-auth';

const token = getAuthToken({
  privateKeyWif,
  requestPath: '/api/endpoint?param=value', // Include full path with query
  body: JSON.stringify(requestBody),        // If POST/PUT with body
  scheme: 'brc77',                          // Default, recommended
  bodyEncoding: 'utf8'