mbedtls/ChangeLog.d/x509-add-tag-check-to-algorithm-params
Paul Elliott ca17ebfbc0 Add tag check to cert algorithm check
Add missing tag check for algorithm parameters when comparing the
signature in the description part of the cert against the actual
signature whilst loading a certificate. This was found by a
certificate (created by fuzzing) that openssl would not verify, but
mbedtls would.

Regression test added (one of the client certs modified accordingly)

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
2020-11-26 16:34:16 +00:00

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Security
* Fix a compliance issue whereby we were not checking the tag on the
algorithm parameters (only the size) when comparing the signature in the
description part of the cert to the real signature. This meant that a
NULL algorithm parameters entry would look identical to an array of REAL
(size zero) to the library and thus the certificate would be considered
valid. However, if the parameters do not match in *any* way then the
certificate should be considered invalid, and indeed OpenSSL marks these
certs as invalid when mbedtls did not.
Many thanks to guidovranken who found this issue via differential fuzzing
and reported it in #3629.