matrix-sdk-crypto contains a log exposure of private key of the server-side key backup

Introduction

In Matrix, the server-side key backup stores encrypted copies of Matrix message keys. This facilitates key sharing between a user’s devices and provides a redundant copy in case all devices are lost. The key backup uses asymmetric cryptography, with each server-side key backup assigned a unique public-private key pair.

Impact

Due to a logic bug introduced in https://github.com/matrix-org/matrix-rust-sdk/pull/2961/commits/71136e44c03c79f80d6d1a2446673bc4d53a2067, the matrix-sdk-crypto crate version 0.7.0 will sometimes log the private part of the backup key pair to Rust debug logs (using the tracing crate).

Patches

This issue has been resolved in matrix-sdk-crypto version 0.7.1.

Workarounds

None.

References

• crates.io release

For more information

If you have any questions or comments about this advisory, please email us at security at matrix.org.