Fix some problems with CRL revocation checking #1051
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There are some circumstances in which check_revocation_crl() will incorrectly indicate that a CRL lists the server's certificate as revoked. testssl#1046 is one of them. Another is any case in which the server's certificate cannot be validated using any of the certificates in the trust store that OpenSSL uses (e.g., the server's certificate was issued by a local CA). In both of these cases, "openssl verify" fails, for some reason other than "certificate revoked", and check_revocation_crl() assumes that any failure of "openssl verify" is the result of certificate revocation. This PR addresses the problem in two ways. First, it adds the "-partial_chain" option to the "openssl verify" command line whenever $OPENSSL supports that option (it is not supported by LibreSSL or by versions of OpenSSL earlier than 1.0.2). This will fix most of the problems when a version of OpenSSL that supports "-partial_chain" is used. Even if the "-partial_chain" option is provided, OpenSSL needs to have at least one CA certificate so that it can get the public key needed to verify the signatures on the server's certificate and on the CRL. So, if the server doesn't send any CA certificates and the server's certificate was not issued by a CA in the trust store, then the verify command will fail even if the "-partial_chain" option is provided. So, as a fail-safe, this PR changes check_revocation_crl() to check the error message that the verify command provides when it fails so that testssl.sh only reports a certificate a revoked if the verify command fails with a reason of "certificate revoked". Note that this PR also fixes two other minor issues. It incorporates testssl#1047, which corrects a typo, and it redirects $OPENSSL's output on line 1479 in order to suppress any error messages that $OPENSSL might print (e.g., "WARNING: can't open config file").
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This PR fixes problems with check_revocation_crl() sometimes reporting that a certificate is revoked even when it isn't, and with check_revocation_ocsp() sometimes reporting "error querying OCSP responder" even if the OCSP responder provided a good response. The most common reason for this to happen is that OpenSSL cannot validate the server's certificate (even without status checking). PR testssl#1051 attempted to get status checking to work even in cases in which the server's certificate could not be validated. This PR instead addresses the problem by not checking status if determine_trust() was unable to validate the server's certificate. In some cases the server's certificate can be validated using some, but not all of the bundles of trusted certificates. For example, I have encountered some sites that can be validated using the Microsoft and Apple bundles, but not the Linux or Mozilla bundles. This PR introduces GOOD_CA_BUNDLE to store a bundle that could be used to successfully validate the server's certificate. If there is no such bundle, then neither check_revocation_crl() nor check_revocation_ocsp() is run. When check_revocation_crl() and check_revocation_ocsp() are called, the status checks within them closely match the validation check in determine_trust(), which helps to ensure that if the check fails it is because of the status information. As noted in testssl#1057, at least one CA provides incorrect information when the CRL is downloaded, so validation could fail for a reason other than the certificate being revoked. So, this PR adds a check of the reason that validation failed and only reports "revoked" if the validation failed for that reason. As noted in testssl#1056, it is not possible to perform an OCSP query without access to the certificate issuer's public key. So, with this PR check_revocation_ocsp() is only called if the server's provided at least one intermediate certificate (i.e., the issuer's certificate, which contains the issuer's public key).
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Closing this PR as #1067 provides an alternative solution. |
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There are some circumstances in which
check_revocation_crl()will incorrectly indicate that a CRL lists the server's certificate as revoked. #1046 is one of them. Another is any case in which the server's certificate cannot be validated using any of the certificates in the trust store that OpenSSL uses (e.g., the server's certificate was issued by a local CA). In both of these cases, "openssl verify" fails, for some reason other than "certificate revoked", andcheck_revocation_crl()assumes that any failure of "openssl verify" is the result of certificate revocation.This PR addresses the problem in two ways. First, it adds the "-partial_chain" option to the "openssl verify" command line whenever
$OPENSSLsupports that option (it is not supported by LibreSSL or by versions of OpenSSL earlier than 1.0.2). This will fix most of the problems when a version of OpenSSL that supports "-partial_chain" is used.However, even if the "-partial_chain" option is provided, OpenSSL needs to have at least one CA certificate so that it can get the public key needed to verify the signatures on the server's certificate and on the CRL. So, if the server doesn't send any CA certificates and the server's certificate was not issued by a CA in the trust store, then the verify command will fail even if the "-partial_chain" option is provided.
So, as a fail-safe, this PR changes
check_revocation_crl()to check the error message that the verify command provides when it fails so that testssl.sh only reports a certificate a revoked if the verify command fails with a reason of "certificate revoked".Note that this PR also fixes two other minor issues. It incorporates #1047, which corrects a typo, and it redirects $OPENSSL's output on line 1479 in order to suppress any error messages that $OPENSSL might print (e.g., "WARNING: can't open config file").