Security Architecture

OpenSIN implements defense-in-depth security across every layer of the stack, from the CLI tool system to the A2A fleet communication.

Threat Model

OpenSIN agents execute arbitrary code, access filesystems, make network requests, and communicate with external services. The security architecture addresses:

Threat	Mitigation
Shell injection	execFile instead of exec, argument array passing
Destructive commands	Pattern-based command blocking (rm -rf /, mkfs, dd, fork bombs)
Path traversal	Workspace-scoped file operations with path validation
Credential leakage	No secrets in logs, environment variable isolation
Malicious MCP servers	Permission gates, user confirmation for dangerous operations
Agent impersonation	JWT-based A2A authentication, mutual TLS
Data exfiltration	Network egress monitoring, allowlisted domains

CLI Security Layer

Tool Permission System

Every tool operation goes through a permission check before execution:

import { PermissionManager } from '@opensin/sdk'

const permissions = new PermissionManager({
  mode: 'interactive', // ask user for dangerous ops
  allowlist: ['/workspace/**'],
  denylist: ['/etc/**', '/usr/**', '~/.ssh/**'],
})

// Check before file write
const allowed = await permissions.check({
  tool: 'write',
  path: '/workspace/src/app.ts',
  action: 'create',
})

Bash Tool Hardening

The bash tool uses execFile (not exec) to prevent shell injection and blocks known destructive patterns:

// Blocked patterns (13 categories):
const DANGEROUS_PATTERNS = [
  /rm\s+(-[a-z]*f[a-z]*\s+)?\/\s*$/,     // rm -rf /
  /mkfs/,                                   // filesystem format
  /dd\s+.*of=\/dev/,                        // disk overwrite
  /:\(\)\s*\{\s*:\|:\s*&\s*\}/,            // fork bomb
  /chmod\s+777\s+\//,                       // world-writable root
  /git\s+reset\s+--hard/,                   // destructive git reset
  /sudo\s+rm/,                              // sudo removal
  // ... 6 more patterns
]

Grep Safety

The grep tool defaults to literal string search (not regex) to prevent ReDoS attacks:

// Safe by default - literal matching
grep({ pattern: "user.password", path: "./src" })

// Opt-in regex with try/catch protection
grep({ pattern: "user\\.pass.*", path: "./src", useRegex: true })

A2A Security

Authentication

All agent-to-agent communication requires authentication:

Agent A                          Agent B
   │                                │
   │── Bearer Token (JWT) ────────>│
   │                                │── Verify signature
   │                                │── Check expiration
   │                                │── Validate claims
   │<── 200 OK + Task Result ──────│

Token Structure

{
  "sub": "sin-hermes",
  "iss": "opensin-auth",
  "aud": "sin-solver",
  "iat": 1712000000,
  "exp": 1712003600,
  "scope": ["task:send", "task:read"],
  "fleet_id": "production"
}

Transport Security

• Production: HTTPS required (TLS 1.3)
• Internal fleet: Cloudflare Tunnel (zero-trust networking)
• Development: HTTP allowed only on localhost

MCP Security

MCP servers expose powerful capabilities. OpenSIN gates access through:

1. Server allowlist: Only approved MCP servers can be loaded
2. Tool-level permissions: Each MCP tool has a risk classification
3. Confirmation gates: High-risk operations require explicit user approval
4. Sandboxing: MCP processes run with minimal filesystem access

{
  "mcpServers": {
    "sin-google-apps": {
      "permissions": {
        "read": "auto-approve",
        "write": "confirm",
        "delete": "confirm",
        "admin": "deny"
      }
    }
  }
}

Secret Management

• No hardcoded secrets: All credentials stored in environment variables or secure vaults
• SIN-PasswordManager: A2A agent for centralized credential management
• Token rotation: Automatic rotation via LaunchDaemon watchers
• Auth isolation: Each agent has its own credential scope

Credential Hierarchy

~/.config/opencode/auth/          # Auth tokens (never synced)
~/.config/opencode/auth.json      # Primary auth (local only)
~/.config/opencode/token.json     # API keys (local only)

Audit & Compliance

• All tool invocations logged with timestamp, user, action, and result
• A2A task history persisted to Supabase
• Git-based audit trail for all code changes
• GitLab LogCenter for centralized log aggregation

Reporting Vulnerabilities

See SECURITY.md for responsible disclosure guidelines.