KeyArc API Security Patterns

Overview

Security patterns for KeyArc's zero-knowledge FastAPI backend services. Covers JWT authentication, encrypted payload validation, audit logging, and OWASP top 10 prevention.

Service Architecture Context

KeyArc uses a multi-service architecture:

Service	Visibility	Security Responsibility
Auth Service	Public	Issues JWTs, validates authHash, rate limits login
Gateway	Public	Validates JWTs, routes to private services
Account Service	Private	Trusts Gateway, uses RBAC for team permissions
Key Service	Private	Trusts Gateway, uses RBAC, validates encrypted payloads

Key security boundaries:

• Gateway handles JWT validation - private services trust user context headers from Gateway
• Auth Service is the only service that validates authHash (never passwords)
• RBAC checks happen in Account Service and Key Service using shared RBAC module
• Audit logging is a shared module used by all services

When to Use

✅ Apply this skill when:

• Creating new API endpoints in any service
• Implementing authentication/authorization
• Handling secrets or encrypted data
• Adding audit logging
• Reviewing security of existing endpoints
• Implementing rate limiting
• Handling errors that might leak data

Core Security Principles

1. Validate encrypted payloads - Never accept plaintext secrets
2. JWT token authentication - Validate using authHash, not passwords
3. Audit everything - Log all secret access (not values)
4. Fail securely - Errors don't leak sensitive data
5. Rate limit auth - Prevent brute force attacks
6. RBAC enforcement - Check permissions at API level

Endpoint Security Checklist

Before merging any new endpoint:

Auth Service endpoints:

• Rate limiting applied (5/minute for login)
• authHash validated (never password)
• Audit log entry created
• Error responses don't leak data

Gateway:

• JWT token validated
• User context headers added for downstream
• Invalid tokens rejected with 401

Account/Key Service endpoints (private):

• User context from Gateway headers (use

  Depends(get_current_user_from_gateway)

  )
• RBAC permissions checked for team operations (use shared RBAC module)
• Encrypted payloads validated - no plaintext secrets (Key Service)
• Audit log entry created
• Error responses don't leak secrets
• Input validation with Pydantic
• SQL injection prevented (use ORM)

JWT Authentication Pattern

# dependencies.py
from fastapi import Depends, HTTPException, status
from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
from jose import JWTError, jwt
from sqlalchemy.ext.asyncio import AsyncSession

security = HTTPBearer()

async def get_current_user(
    credentials: HTTPAuthorizationCredentials = Depends(security),
    db: AsyncSession = Depends(get_db)
) -> User:
    """Validate JWT token and return current user."""
    token = credentials.credentials

    try:
        payload = jwt.decode(
            token,
            SECRET_KEY,
            algorithms=[ALGORITHM]
        )
        user_id: int = payload.get("sub")
        if user_id is None:
            raise HTTPException(
                status_code=status.HTTP_401_UNAUTHORIZED,
                detail="Invalid authentication credentials"
            )
    except JWTError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid authentication credentials"
        )

    # Get user from database
    result = await db.execute(select(User).where(User.id == user_id))
    user = result.scalar_one_or_none()

    if user is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="User not found"
        )

    return user

Creating Tokens (Auth Service Only)

# src/services/auth/app/utils/security.py
from datetime import datetime, timedelta
from jose import jwt

SECRET_KEY = os.getenv("JWT_SECRET")  # From environment
ALGORITHM = "HS256"
ACCESS_TOKEN_EXPIRE_MINUTES = 120  # 2 hours

def create_access_token(data: dict) -> str:
    """Create JWT access token. Auth Service only."""
    to_encode = data.copy()
    expire = datetime.utcnow() + timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES)
    to_encode.update({"exp": expire})

    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)

Gateway User Context

The Gateway validates JWTs and passes user context to private services via headers:

# Gateway adds these headers after JWT validation:
# X-User-ID: <user_id>
# X-User-Email: <email>

# Private services (Account, Key) read user from headers:
# src/services/account/app/dependencies.py or src/services/keys/app/dependencies.py

from fastapi import Header, HTTPException

async def get_current_user_from_gateway(
    x_user_id: str = Header(..., alias="X-User-ID"),
    x_user_email: str = Header(None, alias="X-User-Email"),
) -> dict:
    """Get user context from Gateway headers. For private services only."""
    if not x_user_id:
        raise HTTPException(401, "Missing user context")

    return {
        "id": int(x_user_id),
        "email": x_user_email
    }

Important: Private services should only be accessible via Gateway (Fly.io private networking). They trust Gateway headers because external traffic cannot reach them directly.

Secure Endpoint Example

@router.post("/secrets", response_model=SecretResponse, status_code=201)
async def create_secret(
    secret_data: SecretCreate,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db)
):
    """Create a new encrypted secret."""

    # Validate encrypted payload format
    if not is_valid_ciphertext(secret_data.encrypted_value):
        raise HTTPException(400, "Invalid encrypted format")

    # Create secret (store ciphertext only)
    secret = Secret(
        user_id=current_user.id,
        name=secret_data.name,
        encrypted_value=secret_data.encrypted_value,
        folder_id=secret_data.folder_id,
        tags=secret_data.tags
    )

    db.add(secret)
    await db.commit()
    await db.refresh(secret)

    # Audit log (NO secret value!)
    await create_audit_log(
        db=db,
        user_id=current_user.id,
        action="secret.create",
        resource_type="secret",
        resource_id=secret.id,
        ip_address=request.client.host  # From request context
    )

    return secret

Pydantic Schemas for Security

from pydantic import BaseModel, EmailStr, Field, validator

class SecretCreate(BaseModel):
    """Schema for creating a secret."""
    name: str = Field(min_length=1, max_length=255)
    encrypted_value: str = Field(min_length=1)
    folder_id: int | None = None
    tags: list[str] = Field(default_factory=list)

    @validator('encrypted_value')
    def validate_encrypted(cls, v):
        """Ensure value is actually encrypted (base64)."""
        try:
            import base64
            base64.b64decode(v)
            return v
        except Exception:
            raise ValueError('encrypted_value must be base64-encoded ciphertext')

class LoginRequest(BaseModel):
    """Login request with auth hash (NOT password)."""
    email: EmailStr
    auth_hash: str = Field(min_length=1)

    # NO password field! Only authHash!

Audit Logging

async def create_audit_log(
    db: AsyncSession,
    user_id: int,
    action: str,
    resource_type: str,
    resource_id: int,
    ip_address: str,
    metadata: dict | None = None
) -> AuditLog:
    """Create audit log entry."""
    log = AuditLog(
        user_id=user_id,
        action=action,  # 'secret.view', 'secret.create', 'secret.delete', etc.
        resource_type=resource_type,
        resource_id=resource_id,
        ip_address=ip_address,
        metadata=metadata,  # Never include secret values!
        timestamp=datetime.utcnow()
    )

    db.add(log)
    await db.flush()  # Don't commit yet (part of larger transaction)

    return log

# Usage in endpoint:
await create_audit_log(
    db=db,
    user_id=current_user.id,
    action="secret.view",
    resource_type="secret",
    resource_id=secret_id,
    ip_address=request.client.host
)

RBAC Permission Checking

async def check_team_permission(
    user_id: int,
    team_id: int,
    required_role: str,  # 'owner', 'admin', 'member'
    db: AsyncSession
) -> TeamMembership:
    """Check if user has required role in team."""
    result = await db.execute(
        select(TeamMembership).where(
            TeamMembership.user_id == user_id,
            TeamMembership.team_id == team_id
        )
    )
    membership = result.scalar_one_or_none()

    if not membership:
        raise HTTPException(403, "Not a team member")

    role_hierarchy = {'member': 0, 'admin': 1, 'owner': 2}
    if role_hierarchy.get(membership.role, -1) < role_hierarchy.get(required_role, 999):
        raise HTTPException(403, "Insufficient permissions")

    return membership

Rate Limiting

from slowapi import Limiter
from slowapi.util import get_remote_address

limiter = Limiter(key_func=get_remote_address)

@router.post("/auth/login")
@limiter.limit("5/minute")  # 5 attempts per minute per IP
async def login(
    request: Request,
    login_data: LoginRequest,
    db: AsyncSession = Depends(get_db)
):
    # ... login logic

Error Handling (Secure)

# ❌ BAD: Leaks sensitive data
@router.get("/secrets/{secret_id}")
async def get_secret(secret_id: int):
    secret = await db.get(Secret, secret_id)
    if not secret:
        raise HTTPException(404, f"Secret {secret.encrypted_value} not found")  # LEAK!

# ✅ GOOD: Generic errors
@router.get("/secrets/{secret_id}")
async def get_secret(
    secret_id: int,
    current_user: User = Depends(get_current_user),
    db: AsyncSession = Depends(get_db)
):
    secret = await db.get(Secret, secret_id)

    if not secret:
        raise HTTPException(404, "Secret not found")

    # Check ownership
    if secret.user_id != current_user.id:
        # Same error (don't reveal if secret exists)
        raise HTTPException(404, "Secret not found")

    # Audit log
    await create_audit_log(
        db=db,
        user_id=current_user.id,
        action="secret.view",
        resource_type="secret",
        resource_id=secret_id,
        ip_address=request.client.host
    )

    await db.commit()

    return secret

OWASP Top 10 Quick Reference

See

owasp-checklist.md

for detailed prevention patterns.

Vulnerability	Prevention
Injection	SQLAlchemy ORM, parameterized queries
Broken Auth	JWT tokens, rate limiting, authHash validation
Sensitive Data Exposure	All secrets encrypted, HTTPS only
XXE	Validate XML inputs
Broken Access Control	RBAC enforced at API level
Security Misconfiguration	Secure defaults, no debug in production
XSS	Angular handles this, validate API responses
Insecure Deserialization	Validate Pydantic models
Known Vulnerabilities	Dependabot enabled
Insufficient Logging	Comprehensive audit logs

See Also

• jwt-patterns.md

  - Detailed JWT implementation

• audit-logging.md

  - Comprehensive audit logging requirements

• owasp-checklist.md

  - Detailed OWASP top 10 prevention

Key Principles

1. Validate encrypted payloads: Never accept plaintext secrets
2. Auth with JWT: Token-based, stateless authentication
3. Audit everything: Log access, not values
4. RBAC at API layer: Enforce permissions in endpoints
5. Rate limit sensitive endpoints: Prevent brute force
6. Secure error handling: Generic errors, no leaks
7. Input validation: Always use Pydantic schemas

Security is not optional - apply these patterns to every endpoint.