MatrixSSL 4.2.1 and earlier contains a timing side channel in ECDSA signature generation. This allows a local or a remote attacker, able to measure the duration of hundreds to thousands of signing operations, to compute the private key used. The issue occurs because crypto/pubkey/ecc_math.c scalar multiplication leaks the bit length of the scalar.

References

• https://nvd.nist.gov/vuln/detail/CVE-2019-13629
• https://eprint.iacr.org/2011/232.pdf
• https://minerva.crocs.fi.muni.cz/
• https://tches.iacr.org/index.php/TCHES/article/view/7337
• http://www.openwall.com/lists/oss-security/2019/10/02/2