The Online Certificate Status Protocol (OCSP) enables applications to
determine the (revocation) state of an identified certificate (RFC 2560).
The ocsp command performs many common OCSP tasks. It can be used
to print out requests and responses, create requests and send queries
to an OCSP responder and behave like a mini OCSP server itself.
This specifies the current issuer certificate. This option can be used
multiple times. The certificate specified in filename must be in
PEM format. This option MUST come before any -cert options.
Add the certificate filename to the request. The issuer certificate
is taken from the previous issuer option, or an error occurs if no
issuer certificate is specified.
Same as the cert option except the certificate with serial number
num is added to the request. The serial number is interpreted as a
decimal integer unless preceded by 0x. Negative integers can also
be specified by preceding the value by a - sign.
Sign the OCSP request using the certificate specified in the signer
option and the private key specified by the signkey option. If
the signkey option is not present then the private key is read
from the same file as the certificate. If neither option is specified then
the OCSP request is not signed.
Add an OCSP nonce extension to a request or disable OCSP nonce addition.
Normally if an OCSP request is input using the reqin option no
nonce is added: using the nonce option will force addition of a nonce.
If an OCSP request is being created (using cert and serial options)
a nonce is automatically added specifying no_nonce overrides this.
Read OCSP request or response file from file. These option are ignored
if OCSP request or response creation is implied by other options (for example
with serial, cert and host options).
If the host option is present then the OCSP request is sent to the host
hostname on port port. path specifies the HTTP pathname to use
or "/" by default. This is equivalent to specifying -url with scheme
http:// and the given hostname, port, and pathname.
Connection timeout to the OCSP responder in seconds.
On POSIX systems, when running as an OCSP responder, this option also limits
the time that the responder is willing to wait for the client request.
This time is measured from the time the responder accepts the connection until
the complete request is received.
Run the specified number of OCSP responder child processes, with the parent
process respawning child processes as needed.
Child processes will detect changes in the CA index file and automatically
reload it.
When running as a responder -timeout option is recommended to limit the time
each child is willing to wait for the client's OCSP response.
This option is available on POSIX systems (that support the fork() and other
required unix system-calls).
File containing additional certificates to search when attempting to locate
the OCSP response signing certificate. Some responders omit the actual signer's
certificate from the response: this option can be used to supply the necessary
certificate in such cases.
The certificates specified by the -verify_other option should be explicitly
trusted and no additional checks will be performed on them. This is useful
when the complete responder certificate chain is not available or trusting a
root CA is not appropriate.
Don't attempt to verify the OCSP response signature or the nonce
values. This option will normally only be used for debugging since it
disables all verification of the responders certificate.
Ignore certificates contained in the OCSP response when searching for the
signers certificate. With this option the signers certificate must be specified
with either the -verify_other or -VAfile options.
Don't check the signature on the OCSP response. Since this option
tolerates invalid signatures on OCSP responses it will normally only be
used for testing purposes.
Don't verify the OCSP response signers certificate at all. Since this
option allows the OCSP response to be signed by any certificate it should
only be used for testing purposes.
Don't perform any additional checks on the OCSP response signers certificate.
That is do not make any checks to see if the signers certificate is authorised
to provide the necessary status information: as a result this option should
only be used for testing purposes.
These options specify the range of times, in seconds, which will be tolerated
in an OCSP response. Each certificate status response includes a notBefore
time and an optional notAfter time. The current time should fall between
these two values, but the interval between the two times may be only a few
seconds. In practice the OCSP responder and clients clocks may not be precisely
synchronised and so such a check may fail. To avoid this the
-validity_period option can be used to specify an acceptable error range in
seconds, the default value is 5 minutes.
If the notAfter time is omitted from a response then this means that new
status information is immediately available. In this case the age of the
notBefore field is checked to see it is not older than age seconds old.
By default this additional check is not performed.
This option sets digest algorithm to use for certificate identification in the
OCSP request. Any digest supported by the OpenSSL dgst command can be used.
The default is SHA-1. This option may be used multiple times to specify the
digest used by subsequent certificate identifiers.
The indexfile parameter is the name of a text index file in ca
format containing certificate revocation information.
If the index option is specified the ocsp utility is in responder
mode, otherwise it is in client mode. The request(s) the responder
processes can be either specified on the command line (using issuer
and serial options), supplied in a file (using the reqin option)
or via external OCSP clients (if port or url is specified).
If the index option is present then the CA and rsigner options
must also be present.
Ignore malformed requests or responses: When acting as an OCSP client, retry if
a malformed response is received. When acting as an OCSP responder, continue
running instead of terminating upon receiving a malformed request.
Number of minutes or days when fresh revocation information is available:
used in the nextUpdate field. If neither option is present then the
nextUpdate field is omitted meaning fresh revocation information is
immediately available.
OCSP Response follows the rules specified in RFC2560.
Initially the OCSP responder certificate is located and the signature on
the OCSP request checked using the responder certificate's public key.
Then a normal certificate verify is performed on the OCSP responder certificate
building up a certificate chain in the process. The locations of the trusted
certificates used to build the chain can be specified by the CAfile
and CApath options or they will be looked for in the standard OpenSSL
certificates directory.
If the initial verify fails then the OCSP verify process halts with an
error.
Otherwise the issuing CA certificate in the request is compared to the OCSP
responder certificate: if there is a match then the OCSP verify succeeds.
Otherwise the OCSP responder certificate's CA is checked against the issuing
CA certificate in the request. If there is a match and the OCSPSigning
extended key usage is present in the OCSP responder certificate then the
OCSP verify succeeds.
Otherwise, if -no_explicit is not set the root CA of the OCSP responders
CA is checked to see if it is trusted for OCSP signing. If it is the OCSP
verify succeeds.
If none of these checks is successful then the OCSP verify fails.
What this effectively means if that if the OCSP responder certificate is
authorised directly by the CA it is issuing revocation information about
(and it is correctly configured) then verification will succeed.
If the OCSP responder is a "global responder" which can give details about
multiple CAs and has its own separate certificate chain then its root
CA can be trusted for OCSP signing. For example:
As noted, most of the verify options are for testing or debugging purposes.
Normally only the -CApath, -CAfile and (if the responder is a 'global
VA') -VAfile options need to be used.
The OCSP server is only useful for test and demonstration purposes: it is
not really usable as a full OCSP responder. It contains only a very
simple HTTP request handling and can only handle the POST form of OCSP
queries. It also handles requests serially meaning it cannot respond to
new requests until it has processed the current one. The text index file
format of revocation is also inefficient for large quantities of revocation
data.
It is possible to run the ocsp application in responder mode via a CGI
script using the reqin and respout options.
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