libsignal-service-rs Doesn't Check Origin of Sync Messages

Vulnerability Description

libsignal-service-rs is a Rust version of the libsignal-service-java library which implements the core functionality to communicate with Signal servers. Prior to commit 82d70f6720e762898f34ae76b0894b0297d9b2f8, any contact may forge a sync message, impersonating another device of the local user. The origin of sync messages is not checked. Patched libsignal-service can be found after commit 82d70f6720e762898f34ae76b0894b0297d9b2f8. The `Metadata` struct contains an additional `was_encrypted` field, which breaks the API, but should be easily resolvable. No known workarounds are available.

References

• https://github.com/whisperfish/libsignal-service-rs/security/advisories/GHSA-r58q-66g9-h6g8
• https://github.com/whisperfish/libsignal-service-rs/commit/82d70f6720e762898f34ae76b0894b0297d9b2f8