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PGT-Proxy

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PostgreSQL TLS Proxy is an intermediary server to easily and securely connect TLS enabled PG clients to TLS enabled PG servers.

About PGT-Proxy

Getting started?

The easiest way to get started is via PGT-Proxy's Docker image on on DockerHub. It allows you to securely connect to PG servers living in AWS, Azure, or even on-prem.

Architecture Diagram

Architecture Diagram

Motivations

  1. Enable full TLS verification of PG servers using non-public certificate authorities
  2. For PG servers located in private networks, securely expose them to IP addresses outside their private networks
  3. Enforce TLS communication from PG clients to PG servers

How? PGT-Proxy only ever communicates through TLS. PGT-Proxy enables you to specify the proxy's TLS private key and certificate when it acts as a PG server. PGT-Proxy enable you to specify the certificate authorities it trusts when it acts as a PG client.

Tenets

  1. Security
  2. Frictionless experience for PG clients

Discussion

  1. Enable full TLS verification of PG servers with non-public certificate authorities.
    • PG clients can run full TLS verification when they trust the certificate authority of the PG server.
    • Fully managed PG services often do not use public certificate authorities, which blocks PG clients from verifying the PG server they are connected to.
    • For example, AWS (Aurora / RDS) requires PG clients to trust a certificate authority specific to the region the PG server is deployed in [source].
    • Another example, Google Cloud SQL requires PG clients to trust a certificate authority specific to the PG server itself [sources: 1, 2].
    • PGT-Proxy is responsible for centrally trusting the PG server's certificate authority (avoiding friction on PG clients), and providing a verifiable certificate issued by a public certificate authority (enabling PG clients to run a full TLS verification).
  2. For PG servers located in private networks, securely expose them to IP addresses outside their private networks
    • Exposing PG's entire private network to a VPN or the public internet violates the principle of least access, thus it is not secure.
    • SSH tunnels impose a high degree of friction on PG clients and end-users who may have OS and network restrictions.
    • Load balancers (e.g., AWS NLB, AWS ALB) and reverse proxies (e.g., nginx) would be great, but they do not support PG's TLS protocol. How come? PG's TLS protocol requires bidirectional transmission of special bytes before engaging in the TLS handshake.
    • PGT-Proxy acts as a reverse proxy with support for PG's TLS protocol.
  3. Enforce TLS communication from PG clients to PG servers
    • PG servers might support plaintext mode for legacy reasons (enable trusted access within a private network).
    • Nevertheless, all PG clients should run TLS when communicating from an insecure network
    • If PGT-Proxy is the only way to access a PG server from an insecure network, PGT-Proxy will make sure that all clients are communicating using TLS, even if the PG server supports plaintext.

Usage

Build the binary and run it.

cargo build --release

./target/release/pgt_proxy \
    --server-private-key-path key.key \
    --server-certificate-path cert.pem \
    --server-port 9000 \
    --client-connection-host-or-ip c-abcdef.cluster-crawki488h3k.eu-west-1.rds.amazonaws.com \
    --client-connection-port 5432 \
    --client-tls-validation-host c-abcdef.cluster-crawki488h3k.eu-west-1.rds.amazonaws.com \
    --client-ca-roots-path path-to-aws-rds-ca-roots # will only read files ending in .pem

Connect to the proxy. Notice that channel binding is disabled, because PGT-Proxy is after all a proxy, and PG detects it as such.

psql "sslmode=full-verify host=hostname_in_certificate.com hostaddr=127.0.0.1 port=9000 user=admin password=XXX dbname=postgres channel_binding=disable"

Future Work

Possible

  • Client to PGT-Proxy bi-directional TLS validation (mutual tls)
  • PGT-Proxy to server bi-directional TLS validation (mutual tls)
  • Multiple destination PG servers

Will (Most Likely) Not Be Supported Soon

  • Enforcing PG clients to send "full-verify". Not possible without a custom client as of Postgres Version 16. In the PG protocol, PG clients only send an indication of their intent to use TLS, not details about the TLS verification type they will run.
  • PG connection pooling (PGT-Proxy is transparent, you're free to place a pool in front of your PG server)
  • Channel binding support