Sandbox the PostgreSQL MCP server. Database connections need special handling.
What it needs
| Resource | Access | Details |
|---|
| Filesystem | Read | .pgpass and .postgresql credentials |
| Network | DB hosts | PostgreSQL server hostnames |
| Env | PG* variables | Connection details (host, port, password) |
Complete Policy
command: ["node", "@modelcontextprotocol/server-postgres"]
filesystem:
read:
- "./config/.pgpass" # Password file
- "./config/.postgresql" # SSL/connection config
write: [] # It does not write DB server files
network:
allow:
- "localhost" # Local DB
- "db.internal.example.com" # Remote DB (put your own hostname)
env:
allow:
- "PGHOST"
- "PGPORT"
- "PGUSER"
- "PGPASSWORD"
- "PGSSLMODE"
- "HOME"
limits:
memory_mb: 512
timeout_s: 600
How to run
# Step 1: Install the server
npm install -g @modelcontextprotocol/server-postgres
# Step 2: Set connection variables
export PGHOST="localhost"
export PGPORT="5432"
export PGUSER="myuser"
export PGPASSWORD="mypassword"
export PGSSLMODE="prefer"
# Step 3: Run sandboxed
warden run --policy policy-postgres.yaml
Tips
- Never put
PGPASSWORD in the policy, it comes from the shell
- Give the exact path to the
.pgpass file (relative to the policy file)
- If you have multiple DB hosts, add all of them to
network.allow
- Use
timeout_s: 600 for migrations
Security
- Never put
PGPASSWORD in the policy file
- Check the
.pgpass file permissions (600)
- Use
require for the SSL mode in production
Troubleshooting
| Error | Fix |
|---|
connection refused | Check PGHOST + PGPORT and add the host to network.allow |
password authentication failed | Is PGPASSWORD set in the shell? |
| SSL errors | Set PGSSLMODE |
Resources
