Two years ago, I glanced at Matrix's Olm library and immediately found several side-channel vulnerabilities. After dragging their feet for 90 days, they ended up not bothering to fix any of it. The Matrix.org security team also failed to notify many of the alternative clients about the impending disclosure--a fact that became more annoying when…

Soatok is a blog or publication authored by Soatok Dhole, a security researcher and privacy advocate. Readers can explore articles covering topics such as cryptography, privacy-enhancing technologies, and digital rights. Additionally, they can learn about cybersecurity threats, encryption protocols, and strategies for protecting online privacy.

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Security researcher Soatok discovered multiple cryptographic vulnerabilities in Matrix's Rust library vodozemac, including a critical flaw where the Olm Diffie-Hellman implementation accepts all-zero public keys (the identity element), leading to predictable shared secrets. Additional issues include silent downgrades from V2 to V1 protocol (truncating MACs from 256 to 64 bits), weak ECIES CheckCode implementation, and disabled strict Ed25519 verification by default. The researcher provided patches and proof-of-concept exploits, disclosed publicly after one week rather than the typical 90 days due to Matrix's poor handling of previous vulnerability reports. Both the deprecated libolm and newer vodozemac libraries are affected by the identity element vulnerability.

Cryptographic Issues in Matrix’s Rust Library Vodozemac