• Eric Biggers's avatar
    X.509: fix BUG_ON() when hash algorithm is unsupported · 437499ee
    Eric Biggers authored
    The X.509 parser mishandles the case where the certificate's signature's
    hash algorithm is not available in the crypto API.  In this case,
    x509_get_sig_params() doesn't allocate the cert->sig->digest buffer;
    this part seems to be intentional.  However,
    public_key_verify_signature() is still called via
    x509_check_for_self_signed(), which triggers the 'BUG_ON(!sig->digest)'.
    
    Fix this by making public_key_verify_signature() return -ENOPKG if the
    hash buffer has not been allocated.
    
    Reproducer when all the CONFIG_CRYPTO_SHA512* options are disabled:
    
        openssl req -new -sha512 -x509 -batch -nodes -outform der \
            | keyctl padd asymmetric desc @s
    
    Fixes: 6c2dc5ae ("X.509: Extract signature digest and make self-signed cert checks earlier")
    Reported-by: 's avatarPaolo Valente <paolo.valente@linaro.org>
    Cc: Paolo Valente <paolo.valente@linaro.org>
    Cc: <stable@vger.kernel.org> # v4.7+
    Signed-off-by: 's avatarEric Biggers <ebiggers@google.com>
    Signed-off-by: 's avatarDavid Howells <dhowells@redhat.com>
    437499ee