-CApath directory A directory of trusted certificates. The certificates should
have names of the form: hash.0 or have symbolic links to them of
this form ("hash" is the hashed certificate subject name: see the
-hash option of the x509 utility). Under UNIX the c_rehash script
will automatically create symbolic links to a directory of certificates.
-CAfile file A file of trusted certificates. The file should contain multiple
certificates in 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 verification will be done. Currently accepted uses are
sslclient, sslserver, nssslserver, smimesign, smimeencrypt. See
the VERIFY OPERATION section for more information.
-help prints out a usage message.
-verbose print extra information about the operations being performed.
-issuer_checks print out diagnostics relating to searches for the issuer
certificate of the current certificate. This shows why each candidate
issuer certificate was rejected. However the presence of rejection
messages does not itself imply that anything is wrong: during the
normal verify process several rejections may take place.
- marks the last option. All arguments following this are assumed
to be certificate files. This is useful if the first certificate
filename begins with a -.
certificates one or more certificates to verify. If no certificate filenames
are included then an attempt is made to read a certificate from
standard input. They should all be in PEM format.
VERIFY OPERATIONThe verify program uses the same functions as the internal
SSL and S/MIME verification, therefore this description applies
to these verify operations too.
There is one crucial difference between the verify operations
performed by the verify program: wherever possible an attempt is
made to continue after an error whereas normally the verify operation
would halt on the first error. This allows all the problems with
a certificate chain to be determined.
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. In versions of OpenSSL before 0.9.5a
the first certificate whose subject name matched the issuer of the
current certificate was assumed to be the issuers certificate. In
OpenSSL 0.9.6 and later 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 SSLeay and 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.
DIAGNOSTICSWhen a verify operation fails the output messages can be somewhat
cryptic. The general 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 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.
An exhaustive 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".
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 certificate of 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 value could not be determined rather than
it not matching the expected value, this is only meaningful 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 value could 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 of trusted 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 not be 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 means the 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 not self 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 consistent with 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 name did not match the issuer name of the current certificate.
Only displayed when the -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 key identifier was present and did not match the authority
key identifier current certificate. 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 name and serial number was present and did not match
the authority key identifier of 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 extension does not permit certificate signing.
50 X509_V_ERR_APPLICATION_VERIFICATION: application
verification failure an application specific error. Unused.
RestrictionsAlthough the issuer checks are a considerably 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.
HP Open Source Security for OpenVMS Volume 2:... 
OpenSSL Command Line Interface (CLI) Reference
