The verify operation consists of a number of separate steps.
Firstly a certificate chain is built up starting from the supplied certificate and ending in the root CA. It is an error if the whole chain cannot be built up. The chain is built up by looking up the issuers certificate of the current certificate. If a certificate is found which is its own issuer it is assumed to be the root CA.
The process of 'looking up the issuers certificate' itself involves a number of steps. After all certificates whose subject name matches the issuer name of the current certificate are subject to further tests. The relevant authority key identifier components of the current certificate (if present) must match the subject key identifier (if present) and issuer and serial number of the candidate issuer, in addition the keyUsage extension of the candidate issuer (if present) must permit certificate signing.
The lookup first looks in the list of untrusted certificates and if no match is found the remaining lookups are from the trusted certificates. The root CA is always looked up in the trusted certificate list: if the certificate to verify is a root certificate then an exact match must be found in the trusted list.
The second operation is to check every untrusted certificate's extensions for consistency with the supplied purpose. If the -purpose option is not included then no checks are done. The supplied or "leaf" certificate must have extensions compatible with the supplied purpose and all other certificates must also be valid CA certificates. The precise extensions required are described in more detail in the CERTIFICATE EXTENSIONS section of the x509 utility.
The third operation is to check the trust settings on the root CA. The root CA should be trusted for the supplied purpose. For compatibility with previous versions of OpenSSL, a certificate with no trust settings is considered to be valid for all purposes.
The final operation is to check the validity of the certificate chain. The validity period is checked against the current system time and the notBefore and notAfter dates in the certificate. The certificate signatures are also checked at this point.
If all operations complete successfully then certificate is considered valid. If any operation fails then the certificate is not valid.
When a verify operation fails the output messages can be somewhat cryptic. The general form of the error message is:
The first line contains the name of the certificate being verified followed by the subject name of the certificate. The second line contains the error number and the depth. The depth is number of the certificate being verified when a problem was detected starting with zero for the certificate being verified itself then 1 for the CA that signed the certificate and so on. Finally a text version of the error number is presented.
A partial list of the error codes and messages is shown below, this also includes the name of the error code as defined in the header file x509_vfy.h Some of the error codes are defined but never returned: these are described as "unused".
- X509_V_OK
-
The operation was successful.
- X509_V_ERR_UNSPECIFIED
-
Unspecified error; should not happen.
- X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT
-
The issuer certificate of a looked up certificate could not be found. This normally means the list of trusted certificates is not complete.
- X509_V_ERR_UNABLE_TO_GET_CRL
-
The CRL of a certificate could not be found.
- X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE
-
The certificate signature could not be decrypted. This means that the actual signature value could not be determined rather than it not matching the expected value, this is only meaningful for RSA keys.
- X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE
-
The CRL signature could not be decrypted: this means that the actual signature value could not be determined rather than it not matching the expected value. Unused.
- X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY
-
The public key in the certificate SubjectPublicKeyInfo could not be read.
- X509_V_ERR_CERT_SIGNATURE_FAILURE
-
The signature of the certificate is invalid.
- X509_V_ERR_CRL_SIGNATURE_FAILURE
-
The signature of the certificate is invalid.
- X509_V_ERR_CERT_NOT_YET_VALID
-
The certificate is not yet valid: the notBefore date is after the current time.
- X509_V_ERR_CERT_HAS_EXPIRED
-
The certificate has expired: that is the notAfter date is before the current time.
- X509_V_ERR_CRL_NOT_YET_VALID
-
The CRL is not yet valid.
- X509_V_ERR_CRL_HAS_EXPIRED
-
The CRL has expired.
- X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD
-
The certificate notBefore field contains an invalid time.
- X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD
-
The certificate notAfter field contains an invalid time.
- X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD
-
The CRL lastUpdate field contains an invalid time.
- X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD
-
The CRL nextUpdate field contains an invalid time.
- X509_V_ERR_OUT_OF_MEM
-
An error occurred trying to allocate memory. This should never happen.
- X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT
-
The passed certificate is self-signed and the same certificate cannot be found in the list of trusted certificates.
- X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN
-
The certificate chain could be built up using the untrusted certificates but the root could not be found locally.
- X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY
-
The issuer certificate could not be found: this occurs if the issuer certificate of an untrusted certificate cannot be found.
- X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE
-
No signatures could be verified because the chain contains only one certificate and it is not self signed.
- X509_V_ERR_CERT_CHAIN_TOO_LONG
-
The certificate chain length is greater than the supplied maximum depth. Unused.
- X509_V_ERR_CERT_REVOKED
-
The certificate has been revoked.
- X509_V_ERR_INVALID_CA
-
A CA certificate is invalid. Either it is not a CA or its extensions are not consistent with the supplied purpose.
- X509_V_ERR_PATH_LENGTH_EXCEEDED
-
The basicConstraints pathlength parameter has been exceeded.
- X509_V_ERR_INVALID_PURPOSE
-
The supplied certificate cannot be used for the specified purpose.
- X509_V_ERR_CERT_UNTRUSTED
-
the root CA is not marked as trusted for the specified purpose.
- X509_V_ERR_CERT_REJECTED
-
The root CA is marked to reject the specified purpose.
- X509_V_ERR_SUBJECT_ISSUER_MISMATCH
-
not used as of OpenSSL 1.1.0 as a result of the deprecation of the -issuer_checks option.
- X509_V_ERR_AKID_SKID_MISMATCH
-
Not used as of OpenSSL 1.1.0 as a result of the deprecation of the -issuer_checks option.
- X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH
-
Not used as of OpenSSL 1.1.0 as a result of the deprecation of the -issuer_checks option.
- X509_V_ERR_KEYUSAGE_NO_CERTSIGN
-
Not used as of OpenSSL 1.1.0 as a result of the deprecation of the -issuer_checks option.
- X509_V_ERR_UNABLE_TO_GET_CRL_ISSUER
-
Unable to get CRL issuer certificate.
- X509_V_ERR_UNHANDLED_CRITICAL_EXTENSION
-
Unhandled critical extension.
- X509_V_ERR_KEYUSAGE_NO_CRL_SIGN
-
Key usage does not include CRL signing.
- X509_V_ERR_UNHANDLED_CRITICAL_CRL_EXTENSION
-
Unhandled critical CRL extension.
- X509_V_ERR_INVALID_NON_CA
-
Invalid non-CA certificate has CA markings.
- X509_V_ERR_PROXY_PATH_LENGTH_EXCEEDED
-
Proxy path length constraint exceeded.
- X509_V_ERR_PROXY_SUBJECT_INVALID
-
Proxy certificate subject is invalid. It MUST be the same as the issuer with a single CN component added.
- X509_V_ERR_KEYUSAGE_NO_DIGITAL_SIGNATURE
-
Key usage does not include digital signature.
- X509_V_ERR_PROXY_CERTIFICATES_NOT_ALLOWED
-
Proxy certificates not allowed, please use -allow_proxy_certs.
- X509_V_ERR_INVALID_EXTENSION
-
Invalid or inconsistent certificate extension.
- X509_V_ERR_INVALID_POLICY_EXTENSION
-
Invalid or inconsistent certificate policy extension.
- X509_V_ERR_NO_EXPLICIT_POLICY
-
No explicit policy.
- X509_V_ERR_DIFFERENT_CRL_SCOPE
-
Different CRL scope.
- X509_V_ERR_UNSUPPORTED_EXTENSION_FEATURE
-
Unsupported extension feature.
- X509_V_ERR_UNNESTED_RESOURCE
-
RFC 3779 resource not subset of parent's resources.
- X509_V_ERR_PERMITTED_VIOLATION
-
Permitted subtree violation.
- X509_V_ERR_EXCLUDED_VIOLATION
-
Excluded subtree violation.
- X509_V_ERR_SUBTREE_MINMAX
-
Name constraints minimum and maximum not supported.
- X509_V_ERR_APPLICATION_VERIFICATION
-
Application verification failure. Unused.
- X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE
-
Unsupported name constraint type.
- X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX
-
Unsupported or invalid name constraint syntax.
- X509_V_ERR_UNSUPPORTED_NAME_SYNTAX
-
Unsupported or invalid name syntax.
- X509_V_ERR_CRL_PATH_VALIDATION_ERROR
-
CRL path validation error.
- X509_V_ERR_PATH_LOOP
-
Path loop.
- X509_V_ERR_SUITE_B_INVALID_VERSION
-
Suite B: certificate version invalid.
- X509_V_ERR_SUITE_B_INVALID_ALGORITHM
-
Suite B: invalid public key algorithm.
- X509_V_ERR_SUITE_B_INVALID_CURVE
-
Suite B: invalid ECC curve.
- X509_V_ERR_SUITE_B_INVALID_SIGNATURE_ALGORITHM
-
Suite B: invalid signature algorithm.
- X509_V_ERR_SUITE_B_LOS_NOT_ALLOWED
-
Suite B: curve not allowed for this LOS.
- X509_V_ERR_SUITE_B_CANNOT_SIGN_P_384_WITH_P_256
-
Suite B: cannot sign P-384 with P-256.
- X509_V_ERR_HOSTNAME_MISMATCH
-
Hostname mismatch.
- X509_V_ERR_EMAIL_MISMATCH
-
Email address mismatch.
- X509_V_ERR_IP_ADDRESS_MISMATCH
-
IP address mismatch.
- X509_V_ERR_DANE_NO_MATCH
-
DANE TLSA authentication is enabled, but no TLSA records matched the certificate chain. This error is only possible in BUGS
Although the issuer checks are a considerable improvement over the old technique they still suffer from limitations in the underlying X509_LOOKUP API. One consequence of this is that trusted certificates with matching subject name must either appear in a file (as specified by the -CAfile option) or a directory (as specified by -CApath). If they occur in both then only the certificates in the file will be recognised.
Previous versions of OpenSSL assume certificates with matching subject name are identical and mishandled them.
Previous versions of this documentation swapped the meaning of the X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT and X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY error codes.
SEE ALSO
HISTORY
The -show_chain option was first added to OpenSSL 1.1.0.
The -issuer_checks option is deprecated as of OpenSSL 1.1.0 and is silently ignored.
COPYRIGHT
Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.