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Fix possible error code mangling in psa_mac_verify_finish

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If psa_mac_finish_internal fails (which can only happen due to bad
parameters or hardware problem), the error code was converted to
PSA_ERROR_INVALID_SIGNATURE if the uninitialized stack variable
actual_mac happened to contain the expected MAC. This is a minor bug
but it may be possible to leverage it as part of a longer attack path
in some scenarios.

Reported externally. Found by static analysis.
This commit is contained in:
Gilles Peskine 2020-01-20 16:31:06 +01:00
parent 448d1cc854
commit 28cd41676e
1 changed files with 2 additions and 0 deletions
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2
library/psa_crypto.c
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@ -3030,6 +3030,8 @@ psa_status_t psa_mac_verify_finish( psa_mac_operation_t *operation,
status = psa_mac_finish_internal( operation,
actual_mac, sizeof( actual_mac ) );
if( status != PSA_SUCCESS )
goto cleanup;
if( safer_memcmp( mac, actual_mac, mac_length ) != 0 )
status = PSA_ERROR_INVALID_SIGNATURE;