VERIFY(1ssl)

NAME

verify - Utility to verify certificates.

SYNOPSIS

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

DESCRIPTION

The verify command verifies certificate chains.

COMMAND OPTIONS

-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.

-check_ss_sig

Verify the signature on the self-signed root CA. This is disabled
by default because it doesn't add any security.

- 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 OPERATION

The 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.

DIAGNOSTICS

When 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 of a looked up certificate could not be
found. This normally means the list of trusted certificates is not complete.

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 could not be found: this occurs if the
issuer certificate of an untrusted certificate cannot be found.

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.

BUGS

Although 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.

Previous versions of this documentation swapped the meaning of the
X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT and 20 X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY error codes.

SEE ALSO

x509(1)

0.9.8o 2010-02-23 VERIFY(1SSL)