Commit Graph

2 Commits

Author SHA1 Message Date
anthonyrawlins
a658a7364d Implement Beat 2: Age Encryption Envelope
This commit completes Beat 2 of the SequentialThinkingForCHORUS implementation,
adding end-to-end age encryption for all MCP communications.

## Deliverables

### 1. Age Encryption/Decryption Package (pkg/seqthink/ageio/)
- `crypto.go`: Core encryption/decryption with age
- `testkeys.go`: Test key generation and convenience functions
- `crypto_test.go`: Comprehensive unit tests (11 tests, all passing)
- `golden_test.go`: Golden tests with real MCP payloads (12 tests, all passing)

**Features:**
- File-based identity and recipient key loading
- Streaming encryption/decryption support
- Proper error handling for all failure modes
- Performance benchmarks showing 400+ MB/s throughput

**Test Coverage:**
- Round-trip encryption/decryption for various payload sizes
- Unicode and emoji support
- Large payload handling (100KB+)
- Invalid ciphertext rejection
- Wrong key detection
- Truncated/modified ciphertext detection

### 2. Encrypted Proxy Handlers (pkg/seqthink/proxy/)
- `server_encrypted.go`: Encrypted tool call handler
- Updated `server.go`: Automatic routing based on encryption config
- Content-Type enforcement: `application/age` required when encryption enabled
- Metrics tracking for encryption/decryption failures

**Flow:**
1. Client sends encrypted request with `Content-Type: application/age`
2. Wrapper decrypts using age identity
3. Wrapper calls MCP server (plaintext on loopback)
4. Wrapper encrypts response
5. Client receives encrypted response with `Content-Type: application/age`

### 3. SSE Streaming with Encryption (pkg/seqthink/proxy/sse.go)
- `handleSSEEncrypted()`: Encrypted Server-Sent Events streaming
- `handleSSEPlaintext()`: Plaintext SSE for testing
- Base64-encoded encrypted frames for SSE transport
- `DecryptSSEFrame()`: Client-side frame decryption helper
- `ReadSSEStream()`: SSE stream parsing utility

**SSE Frame Format (Encrypted):**
```
event: thought
data: <base64-encoded age-encrypted JSON>
id: 1
```

### 4. Configuration-Based Mode Switching
The wrapper now operates in two modes based on environment variables:

**Encrypted Mode** (AGE_IDENT_PATH and AGE_RECIPS_PATH set):
- All requests/responses encrypted with age
- Content-Type: application/age enforced
- SSE frames base64-encoded and encrypted

**Plaintext Mode** (no encryption paths set):
- Direct plaintext proxying for development/testing
- Standard JSON Content-Type
- Plaintext SSE frames

## Testing Results

### Unit Tests
```
PASS: TestEncryptDecryptRoundTrip (all variants)
PASS: TestEncryptEmptyData
PASS: TestDecryptEmptyData
PASS: TestDecryptInvalidCiphertext
PASS: TestDecryptWrongKey
PASS: TestStreamingEncryptDecrypt
PASS: TestConvenienceFunctions
```

### Golden Tests
```
PASS: TestGoldenEncryptionRoundTrip (7 scenarios)
  - sequential_thinking_request (283→483 bytes, 70.7% overhead)
  - sequential_thinking_revision (303→503 bytes, 66.0% overhead)
  - sequential_thinking_branching (315→515 bytes, 63.5% overhead)
  - sequential_thinking_final (320→520 bytes, 62.5% overhead)
  - large_context_payload (3800→4000 bytes, 5.3% overhead)
  - unicode_payload (264→464 bytes, 75.8% overhead)
  - special_characters (140→340 bytes, 142.9% overhead)

PASS: TestGoldenDecryptionFailures (5 scenarios)
```

### Performance Benchmarks
```
Encryption:
  - 1KB:   5.44 MB/s
  - 10KB:  52.57 MB/s
  - 100KB: 398.66 MB/s

Decryption:
  - 1KB:   9.22 MB/s
  - 10KB:  85.41 MB/s
  - 100KB: 504.46 MB/s
```

## Security Properties

 **Confidentiality**: All payloads encrypted with age (X25519+ChaCha20-Poly1305)
 **Authenticity**: age provides AEAD with Poly1305 MAC
 **Forward Secrecy**: Each encryption uses fresh ephemeral keys
 **Key Management**: File-based identity/recipient keys
 **Tampering Detection**: Modified ciphertext rejected
 **No Plaintext Leakage**: MCP server only on 127.0.0.1 loopback

## Next Steps (Beat 3)

Beat 3 will add KACHING JWT policy enforcement:
- JWT token validation (`pkg/seqthink/policy/`)
- Scope checking for `sequentialthinking.run`
- JWKS fetching and caching
- Policy denial metrics

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-10-13 08:42:28 +11:00
anthonyrawlins
3ce9811826 Implement Beat 1: Sequential Thinking Age-Encrypted Wrapper (Skeleton)
This commit completes Beat 1 of the SequentialThinkingForCHORUS implementation,
providing a functional plaintext skeleton for the age-encrypted wrapper.

## Deliverables

### 1. Main Wrapper Entry Point
- `cmd/seqthink-wrapper/main.go`: HTTP server on :8443
- Configuration loading from environment variables
- Graceful shutdown handling
- MCP server readiness checking with timeout

### 2. MCP Client Package
- `pkg/seqthink/mcpclient/client.go`: HTTP client for MCP server
- Communicates with MCP server on localhost:8000
- Health check endpoint
- Tool call endpoint with 120s timeout

### 3. Proxy Server Package
- `pkg/seqthink/proxy/server.go`: HTTP handlers for wrapper
- Health and readiness endpoints
- Tool call proxy (plaintext for Beat 1)
- SSE endpoint placeholder
- Metrics endpoint integration

### 4. Observability Package
- `pkg/seqthink/observability/logger.go`: Structured logging with zerolog
- `pkg/seqthink/observability/metrics.go`: Prometheus metrics
- Counters for requests, errors, decrypt/encrypt failures, policy denials
- Request duration histogram

### 5. Docker Infrastructure
- `deploy/seqthink/Dockerfile`: Multi-stage build
- `deploy/seqthink/entrypoint.sh`: Startup orchestration
- `deploy/seqthink/mcp_stub.py`: Minimal MCP server for testing

### 6. Build System Integration
- Updated `Makefile` with `build-seqthink` target
- Uses GOWORK=off and -mod=mod for clean builds
- `docker-seqthink` target for container builds

## Testing

Successfully builds with:
```
make build-seqthink
```

Binary successfully starts and waits for MCP server connection.

## Next Steps

Beat 2 will add:
- Age encryption/decryption (pkg/seqthink/ageio)
- Content-Type: application/age enforcement
- SSE streaming with encrypted frames
- Golden tests for crypto round-trips

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-10-13 08:35:43 +11:00