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The following guide deploys the Minimus Postgres image together with custom certificates generated with OpenSSL to help you get started. Run the code to try it for yourself.

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Components

  • Postgres image: Postgres container configured with the secure configuration for client authentication.
  • certgen.sh script: Generates a custom CA, server, and client certificates using OpenSSL.
  • minidebug image: A Minimus dev toolkit that provides a shell, OpenSSL, and other utilities used to generate the certificates.
  • psql installed

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What this guide demonstrates

  • TLS handshake validation
  • Server/client certificate trust
  • Basic auth and Postgres operations
  • Image compatibility

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Directory Structure

.
├── certgen.sh             # Certificate generation script
├── create-certs.yml       # Compose file to run certgen container
├── entrypoint.sh          # Custom PostgreSQL entrypoint to set permissions
├── pg_hba.conf            # Custom pg_hba config to require SSL and client certs
└── docker-compose.yml     # Compose file to run PostgresDB

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Deploy Postgres with TLS certificates

1

Save certgen.sh

Save the following script to a file named certgen.sh. The script is used to generate the TLS certificates and store them in a certs folder on the host.
certgen.sh
#!/bin/sh
# Company: Minimus
# Author: Alexander Haytovich

set -e
cd /certs

echo "[INFO] Creating OpenSSL config for server..."
cat > openssl.cnf <<EOF
[req]
distinguished_name = req_distinguished_name
req_extensions = v3_server
prompt = no

[req_distinguished_name]
CN = postgres

[v3_server]
keyUsage = keyEncipherment, dataEncipherment
extendedKeyUsage = serverAuth
subjectAltName = @alt_names

[alt_names]
DNS.1 = postgres
DNS.2 = localhost
IP.1 = 127.0.0.1
IP.2 = 192.168.30.0
IP.3 = 192.168.30.2
IP.4 = 192.168.30.3



[v3_ca]
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical, CA:true
keyUsage = critical, keyCertSign, cRLSign
EOF

echo "[INFO] Creating OpenSSL config for client..."
cat > client_openssl.cnf <<EOF
[req]
distinguished_name = req_distinguished_name
req_extensions = v3_client
prompt = no

[req_distinguished_name]
CN = testuser

[v3_client]
keyUsage = critical, digitalSignature, keyEncipherment
extendedKeyUsage = clientAuth
EOF

echo "[INFO] Generating CA certificate..."
openssl genrsa -out ca-key.pem 2048
openssl req -x509 -new -nodes -key ca-key.pem \
  -sha256 -days 365 -out ca.pem \
  -subj "/CN=Test CA" \
  -extensions v3_ca -config openssl.cnf

echo "[INFO] Generating server key and CSR..."
openssl genrsa -out server-key.pem 2048
openssl req -new -key server-key.pem -out server.csr -config openssl.cnf -extensions v3_server

echo "[INFO] Signing server certificate..."
openssl x509 -req -in server.csr -CA ca.pem -CAkey ca-key.pem -CAcreateserial \
  -out server-cert.pem -days 365 -sha256 \
  -extfile openssl.cnf -extensions v3_server

echo "[INFO] Generating client certificate..."
openssl genrsa -out client-key.pem 2048
openssl req -new -key client-key.pem -out client.csr \
  -config client_openssl.cnf -extensions v3_client
openssl x509 -req -in client.csr -CA ca.pem -CAkey ca-key.pem -CAcreateserial \
  -out client-cert.pem -days 365 -sha256 \
  -extfile client_openssl.cnf -extensions v3_client

# Ensure private key is root-owned and protected (for PostgreSQL)
echo "[INFO] Fixing permissions for client-key.pem..."

#python client not running as root, changing client permissions to user 1000 that is running the python client
chown 1000:1000 /certs/client-key.pem
chmod 600 /certs/client-key.pem


echo "[SUCCESS] Certificates created:"
2

Save create-certs.yml

Save the following YAML file to run with Docker Compose. It uses the Minimus minidebug image to generate the certificates with the certgen.shshell script. Minidebug is a Minimus dev toolkit that provides a shell, OpenSSL, and other utilities.The certificates will be persisted in the certs volume on the host.
create-certs.yml
services:
  create_certs:
    image: reg.mini.dev/minidebug:latest
    container_name: create_certs
    volumes:
    - ./certs:/certs
    - ./certgen.sh:/certgen.sh:ro
    entrypoint:
    - /bin/sh
    - /certgen.sh
    network_mode: none
3

Generate certificates

Run the following to generate the certificates:
docker compose -f create-certs.yml up

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TLS certificates

The script certgen.sh generates the following self-signed certificates:
  • Self-signed CA certificate (ca.pem)
  • Server certificates (server-cert.pem, server-key.pem) with SANs: postgres, localhost, 127.0.0.1, and 192.168.30.3
  • Client certificates for testuser(client.pem, client-key.pem)
Client private key permissions are set to 0600 and owned by UID 1000 . Certificate permissions are adjusted to support non-root containers. The certificates will be mounted into the Postgres container.
4

Save custom entrypoint

entrypoint.sh
#!/bin/bash
set -e
# Fix ownership so postgres can use the private key
echo "[INFO] Fixing ownership and permissions of /certs..."
chown postgres:postgres /certs/server-key.pem
echo "[INFO] Fixing file permissions..."
# Restrict private key access
chmod 600 /certs/server-key.pem

echo "[INFO] Launching PostgreSQL..."
exec docker-entrypoint.sh "$@"
Make sure the entrypoint script is executable on your host. If necessary, give it execute permissions:
chmod +x ./entrypoint.sh
5

Save custom HBA

PostgreSQL’s default access rules are defined in the file pg_hba.conf. Save the following configuration to mount it and customize the Host-Based Authentication rules.
pg_hba.conf
# Allow local socket connections without SSL (for internal psql commands)
local   all             all                                     trust

# Allow readonly_user to connect using password over SSL
hostssl all readonly_user 0.0.0.0/0 scram-sha-256

# Allow remote SSL connections with client cert validation
hostssl all             all             0.0.0.0/0               cert clientcert=verify-full
6

Save Docker Compose script

Save the following Docker Compose script to a file nameddocker-compose.yml. This script sets up the Postgres service with a healthcheck, mounts a volume with the certificates, the custom entrypoint and the custom HBA config, and maps port 5432.
docker-compose.yml
services:
  postgres:
    image: reg.mini.dev/postgres
    container_name: pg_ssl
    environment:
      POSTGRES_USER: testuser
      POSTGRES_PASSWORD: testpass
      POSTGRES_DB: testdb
    volumes:
    - pgdata:/var/lib/postgresql/data
    - ./certs:/certs
    - ./entrypoint.sh:/entrypoint.sh:ro
    - ./pg_hba.conf:/etc/postgresql/pg_hba.conf
    ports:
    - 5432:5432
    healthcheck:
      test:
      - CMD
      - pg_isready
      - -U
      - testuser
      - -d
      - testdb
      interval: 5s
      retries: 10
    entrypoint:
    - /entrypoint.sh
    command: "postgres\n  -c ssl=on\n  -c ssl_cert_file=/certs/server-cert.pem\n \
      \ -c ssl_key_file=/certs/server-key.pem\n  -c ssl_ca_file=/certs/ca.pem\n  -c\
      \ hba_file=/etc/postgresql/pg_hba.conf\n"
volumes:
  pgdata: null
7

Run Postgres

Start the Postgres container:
docker compose -f docker-compose.yml up
8

Run tests over psql

Use psql to connect over TLS and run tests. For example, here are a few commands you can try out:
  1. Connect to the db: 
    psql "host=127.0.0.1 \
port=5432 \
dbname=testdb \
user=testuser \
sslmode=verify-ca \
sslrootcert=./certs/ca.pem \
sslcert=./certs/client-cert.pem \
sslkey=./certs/client-key.pem"
  2. Show all schemas in current database: 
    \dn
  3. Show server version: 
    SELECT version();
  4. Check that TLS is active: 
    SHOW ssl;
SHOW ssl_cert_file;
SHOW ssl_key_file;