RabbitMQ amqp091-go: Connection Configuration Overwrite via Unsanitized TLS Path Parameter Injection

Summary

A query parameter injection vulnerability exists in the AMQP client's connection URI formatting logic. When generating or parsing connection URIs, TLS-related filesystem paths (such as certificates or keys) are appended directly to the URI's query string using string concatenation rather than secure URL encoding via functions like url.QueryEscape.

If an application handles a TLS file path containing special character delimiters (such as & or =), these characters are interpreted as parameter separators by the URI parser. If the resulting URI.String() output is subsequently re-parsed via ParseURI, the injected fields can silently overwrite or hijack critical configuration parameters, forcing the client to use arbitrary connection settings or alternate TLS files.

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Vulnerability Details

Mechanism

The vulnerability lies within the lack of proper escaping when compiling connection string components into a raw URL format:

// Example of insecure string concatenation during URI building
uri := fmt.Sprintf("amqps://user:pass@host/%s?certfile=%s&keyfile=%s", vhost, certPath, keyPath)

Because certPath and keyPath are not passed through url.QueryEscape, special URL characters preserve their control meanings. For instance, if a user supply a certificate path named: /tmp/cert=foo&keyfile=/evil/path

The generated string translates into: ...?certfile=/tmp/cert=foo&keyfile=/evil/path&keyfile=/original/path

When this string passes back through ParseURI (common in connection re-dial routines or configuration replication steps), standard URL parsing mechanics treat the string as multiple distinct parameters. Depending on map assignment order inside the parser, the injected keys take precedence over the original parameters.

Impact

By manipulating the file paths used for TLS assets, an attacker or compromised local sub-system can:

• Inject arbitrary alternative options or override protocol settings.
• Substitute or switch keyfiles, leading to connection failures or the parsing of unauthorized cryptographic assets.
• Corrupt connection state variables, triggering application-layer failures during connection setup or recovery.

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Attack Vector

An attacker who has partial control over directory naming conventions or environmental variables used to specify local infrastructure paths can execute a parameter injection attack:

1. Path Creation: An attacker sets up a path containing deliberate URL parameter delimiters (e.g., /var/lib/certs/client.crt?cacertfile=/tmp/fake_ca.crt&).
2. String Generation: The application serializes the active connection state or passes the paths down to an unescaped URI builder function.
3. Configuration Hijack: The URI string is generated with the injected parameter embedded into the query structure. When the client attempts to reuse or re-parse this connection string during a connection retry or worker spin-up, it parses the injected cacertfile parameter, loading a different, unverified Certificate Authority string.