PgDoorman rejects PostgreSQL StartupMessage packets containing an empty parameter value.

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Summary

PgDoorman rejects PostgreSQL StartupMessage packets containing an empty parameter value.

This affects clients using lib/pq. In particular, lib/pq v1.11.1 always includes the options parameter in the startup packet, even when its value is empty:

options\0\0

PgDoorman's parse_params() ignores every empty null-terminated string. As a result, it keeps the options key but drops its empty value, producing an odd number of parsed strings and rejecting the connection.

Error

Protocol synchronization error: Invalid client startup message: Expected key-value pairs, but received 7 parameters

Environment

• PgDoorman version: 3.10.7
• PostgreSQL driver: github.com/lib/pq v1.11.1
• PostgreSQL SSL mode: disabled

Steps to reproduce

postgresql://my-user:my-password@pg-doorman-address:6432/my-database?sslmode=disable

PgDoorman rejects the startup packet with:

Invalid client startup message: Expected key-value pairs, but received 7 parameters

A representative startup parameter sequence is:

user\0my-user\0
database\0my-database\0
options\0\0
client_encoding\0UTF8\0
\0

Expected behavior

PgDoorman should accept empty parameter values.

In the PostgreSQL startup protocol:

• An empty parameter name marks the end of the parameter list.
• A parameter value may be empty.
• options\0\0 should therefore be parsed as options = "", not as a missing value.

Actual behavior

In src/messages/protocol.rs, parse_params() only pushes a parsed string when it is non-empty:

if !tmp.is_empty() {
    buf.push(tmp.clone());
    tmp.clear();
}

This removes both:

• the final empty parameter-list terminator;
• legitimate empty parameter values.

After the empty options value is discarded, PgDoorman sees seven strings and reports an invalid key/value pair count.

Note

Upgrading clients to lib/pq v1.11.2 fixes the issue, as they stop sending empty options.
link to release

Workaround

Setting a non-empty options value allows the client to connect:

postgresql://my-user:my-password@pg-doorman-address:6432/my-database?sslmode=disable%20options='-c%20application_name=my-application'

This workaround has been tested successfully.

AI disclosure

This issue was drafted with assistance from ChatGPT. The reported behavior, reproduction steps, workaround, and technical details were manually verified before submission.