Kerberos Authentication with PostgreSQL Binary Protocol Proxies

Kerberos authentication for PostgreSQL is straightforward when client and server talk directly. It’s far harder when you introduce a proxy, especially one that operates at the binary protocol level. Standard proxies handle TCP streams just fine, but Kerberos adds complexity: ticket exchanges, encrypted session keys, and GSSAPI negotiation must survive the hop intact.

Postgres uses its own wire format. The binary protocol carries startup messages, authentication exchanges, query frames, and result sets with no tolerance for mangling. Combining Kerberos with binary protocol proxying means your proxy must:

• Pass through GSSAPI negotiation without breaking message boundaries.
• Avoid injecting or stripping bytes that alter length fields.
• Handle large packets during Kerberos token exchange.
• Maintain latency low enough to prevent authentication failures.

The challenge is that Kerberos is stateful. Each ticket exchange depends on precise sequencing. Any ill-timed buffer flush or read-ahead can corrupt the session. A proper Postgres binary protocol proxy must be aware of backend and frontend states, parsing headers and payload lengths while keeping authentication opaque.

Efficient implementations stream data directly while tracking frame metadata. This way, Kerberos messages remain untouched, but the proxy still knows where authentication ends and SQL begins. Once auth succeeds, the proxy can monitor queries or apply routing policies without interfering with the encrypted exchange.

Security matters. Kerberos for PostgreSQL protects credentials via tickets instead of passwords. Proxying at the binary protocol level allows for central access control, query inspection, and failover handling while keeping Kerberos—and its trust chain—fully operational.

Building this right means testing with real workloads: multi-step GSSAPI negotiations, various ticket lifetimes, and network jitter simulations. Only then can you ensure that Kerberos authentication and Postgres binary protocol proxying work together under pressure.

If you want to see Kerberos + Postgres binary protocol proxying in action without writing it from scratch, try it live at hoop.dev and deploy a working setup in minutes.