MAN page from Trustix openssl-0.9.7m-1tr.i586.rpm


Section: OpenSSL (1)
Updated: 2001-10-08


verify - Utility to verify certificates. 


openssl verify[-CApath directory][-CAfile file][-purpose purpose][-untrusted file][-help][-issuer_checks][-verbose][-][certificates] 


The verify command verifies certificate chains. 


-CApath directory
A directory of trusted certificates. The certificates should have namesof the form: hash.0 or have symbolic links to them of thisform (``hash'' is the hashed certificate subject name: see the -hash optionof the x509 utility). Under Unix the c_rehash script will automaticallycreate symbolic links to a directory of certificates.
-CAfile file
A file of trusted certificates. The file should contain multiple certificatesin PEM format concatenated together.
-untrusted file
A file of untrusted certificates. The file should contain multiple certificates
-purpose purpose
the intended use for the certificate. Without this option no chain verificationwill be done. Currently accepted uses are sslclient, sslserver,nssslserver, smimesign, smimeencrypt. See the VERIFY OPERATIONsection for more information.
prints out a usage message.
print extra information about the operations being performed.
print out diagnostics relating to searches for the issuer certificateof the current certificate. This shows why each candidate issuercertificate was rejected. However the presence of rejection messagesdoes not itself imply that anything is wrong: during the normalverify process several rejections may take place.
marks the last option. All arguments following this are assumed to becertificate files. This is useful if the first certificate filename beginswith a -.
one or more certificates to verify. If no certificate filenames are includedthen an attempt is made to read a certificate from standard input. They shouldall be in PEM format.


The verify program uses the same functions as the internal SSL and S/MIMEverification, therefore this description applies to these verify operationstoo.

There is one crucial difference between the verify operations performedby the verify program: wherever possible an attempt is made to continueafter an error whereas normally the verify operation would halt on thefirst error. This allows all the problems with a certificate chain to bedetermined.

The verify operation consists of a number of separate steps.

Firstly a certificate chain is built up starting from the supplied certificateand ending in the root CA. It is an error if the whole chain cannot be builtup. The chain is built up by looking up the issuers certificate of the currentcertificate. 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 numberof steps. In versions of OpenSSL before 0.9.5a the first certificate whosesubject name matched the issuer of the current certificate was assumed to bethe issuers certificate. In OpenSSL 0.9.6 and later all certificateswhose subject name matches the issuer name of the current certificate are subject to further tests. The relevant authority key identifier componentsof the current certificate (if present) must match the subject key identifier(if present) and issuer and serial number of the candidate issuer, in additionthe keyUsage extension of the candidate issuer (if present) must permitcertificate signing.

The lookup first looks in the list of untrusted certificates and if no matchis found the remaining lookups are from the trusted certificates. The root CAis always looked up in the trusted certificate list: if the certificate toverify is a root certificate then an exact match must be found in the trustedlist.

The second operation is to check every untrusted certificate's extensions forconsistency with the supplied purpose. If the -purpose option is not includedthen no checks are done. The supplied or ``leaf'' certificate must have extensionscompatible with the supplied purpose and all other certificates must also be validCA certificates. The precise extensions required are described in more detail inthe CERTIFICATE EXTENSIONS section of the x509 utility.

The third operation is to check the trust settings on the root CA. The rootCA should be trusted for the supplied purpose. For compatibility with previousversions of SSLeay and OpenSSL a certificate with no trust settings is consideredto be valid for all purposes.

The final operation is to check the validity of the certificate chain. The validityperiod is checked against the current system time and the notBefore and notAfterdates in the certificate. The certificate signatures are also checked at thispoint.

If all operations complete successfully then certificate is considered valid. Ifany operation fails then the certificate is not valid. 


When a verify operation fails the output messages can be somewhat cryptic. Thegeneral form of the error message is:

 server.pem: /C=AU/ST=Queensland/O=CryptSoft Pty Ltd/CN=Test CA (1024 bit) error 24 at 1 depth lookup:invalid CA certificate

The first line contains the name of the certificate being verified followed bythe subject name of the certificate. The second line contains the error numberand the depth. The depth is number of the certificate being verified when aproblem was detected starting with zero for the certificate being verified itselfthen 1 for the CA that signed the certificate and so on. Finally a text versionof the error number is presented.

An exhaustive list of the error codes and messages is shown below, this alsoincludes the name of the error code as defined in the header file x509_vfy.hSome of the error codes are defined but never returned: these are describedas ``unused''.

0 X509_V_OK: ok
the operation was successful.
2 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate
the issuer certificate could not be found: this occurs if the issuer certificateof an untrusted certificate cannot be found.
3 X509_V_ERR_UNABLE_TO_GET_CRL unable to get certificate CRL
the CRL of a certificate could not be found. Unused.
4 X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE: unable to decrypt certificate's signature
the certificate signature could not be decrypted. This means that the actual signature valuecould not be determined rather than it not matching the expected value, this is onlymeaningful for RSA keys.
5 X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE: unable to decrypt CRL's signature
the CRL signature could not be decrypted: this means that the actual signature valuecould not be determined rather than it not matching the expected value. Unused.
6 X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY: unable to decode issuer public key
the public key in the certificate SubjectPublicKeyInfo could not be read.
7 X509_V_ERR_CERT_SIGNATURE_FAILURE: certificate signature failure
the signature of the certificate is invalid.
8 X509_V_ERR_CRL_SIGNATURE_FAILURE: CRL signature failure
the signature of the certificate is invalid. Unused.
9 X509_V_ERR_CERT_NOT_YET_VALID: certificate is not yet valid
the certificate is not yet valid: the notBefore date is after the current time.
10 X509_V_ERR_CERT_HAS_EXPIRED: certificate has expired
the certificate has expired: that is the notAfter date is before the current time.
11 X509_V_ERR_CRL_NOT_YET_VALID: CRL is not yet valid
the CRL is not yet valid. Unused.
12 X509_V_ERR_CRL_HAS_EXPIRED: CRL has expired
the CRL has expired. Unused.
13 X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD: format error in certificate's notBefore field
the certificate notBefore field contains an invalid time.
14 X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD: format error in certificate's notAfter field
the certificate notAfter field contains an invalid time.
15 X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD: format error in CRL's lastUpdate field
the CRL lastUpdate field contains an invalid time. Unused.
16 X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD: format error in CRL's nextUpdate field
the CRL nextUpdate field contains an invalid time. Unused.
17 X509_V_ERR_OUT_OF_MEM: out of memory
an error occurred trying to allocate memory. This should never happen.
18 X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT: self signed certificate
the passed certificate is self signed and the same certificate cannot be found in the list oftrusted certificates.
19 X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN: self signed certificate in certificate chain
the certificate chain could be built up using the untrusted certificates but the root could notbe found locally.
20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY: unable to get local issuer certificate
the issuer certificate of a locally looked up certificate could not be found. This normally meansthe list of trusted certificates is not complete.
21 X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE: unable to verify the first certificate
no signatures could be verified because the chain contains only one certificate and it is notself signed.
22 X509_V_ERR_CERT_CHAIN_TOO_LONG: certificate chain too long
the certificate chain length is greater than the supplied maximum depth. Unused.
23 X509_V_ERR_CERT_REVOKED: certificate revoked
the certificate has been revoked. Unused.
24 X509_V_ERR_INVALID_CA: invalid CA certificate
a CA certificate is invalid. Either it is not a CA or its extensions are not consistentwith the supplied purpose.
25 X509_V_ERR_PATH_LENGTH_EXCEEDED: path length constraint exceeded
the basicConstraints pathlength parameter has been exceeded.
26 X509_V_ERR_INVALID_PURPOSE: unsupported certificate purpose
the supplied certificate cannot be used for the specified purpose.
27 X509_V_ERR_CERT_UNTRUSTED: certificate not trusted
the root CA is not marked as trusted for the specified purpose.
28 X509_V_ERR_CERT_REJECTED: certificate rejected
the root CA is marked to reject the specified purpose.
29 X509_V_ERR_SUBJECT_ISSUER_MISMATCH: subject issuer mismatch
the current candidate issuer certificate was rejected because its subject namedid not match the issuer name of the current certificate. Only displayed whenthe -issuer_checks option is set.
30 X509_V_ERR_AKID_SKID_MISMATCH: authority and subject key identifier mismatch
the current candidate issuer certificate was rejected because its subject keyidentifier was present and did not match the authority key identifier currentcertificate. Only displayed when the -issuer_checks option is set.
31 X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH: authority and issuer serial number mismatch
the current candidate issuer certificate was rejected because its issuer nameand serial number was present and did not match the authority key identifierof the current certificate. Only displayed when the -issuer_checks option is set.
32 X509_V_ERR_KEYUSAGE_NO_CERTSIGN:key usage does not include certificate signing
the current candidate issuer certificate was rejected because its keyUsage extensiondoes not permit certificate signing.
50 X509_V_ERR_APPLICATION_VERIFICATION: application verification failure
an application specific error. Unused.


Although the issuer checks are a considerably improvement over the old technique they stillsuffer from limitations in the underlying X509_LOOKUP API. One consequence of this is thattrusted 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 onlythe certificates in the file will be recognised.

Previous versions of OpenSSL assume certificates with matching subject name are identical andmishandled them. 






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