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4.2.6 Invoking ocsptool
Ocsptool is a program that can parse and print information about OCSP requests/responses, generate requests and verify responses.
This section was generated by AutoGen,
using the agtexi-cmd template and the option descriptions for the ocsptool program.
This software is released under the GNU General Public License, version 3 or later.
ocsptool help/usage (‘--help’)
This is the automatically generated usage text for ocsptool.
The text printed is the same whether selected with the help option
(‘--help’) or the more-help option (‘--more-help’). more-help will print
the usage text by passing it through a pager program.
more-help is disabled on platforms without a working
fork(2) function. The PAGER environment variable is
used to select the program, defaulting to ‘more’. Both will exit
with a status code of 0.
ocsptool - GnuTLS OCSP tool
Usage: ocsptool [ -<flag> [<val>] | --<name>[{=| }<val>] ]...
-d, --debug=num Enable debugging
- it must be in the range:
0 to 9999
-V, --verbose More verbose output
- may appear multiple times
--infile=file Input file
- file must pre-exist
--outfile=str Output file
--ask[=arg] Ask an OCSP/HTTP server on a certificate validity
- requires these options:
load-cert
load-issuer
-e, --verify-response Verify response
-i, --request-info Print information on a OCSP request
-j, --response-info Print information on a OCSP response
-q, --generate-request Generate an OCSP request
--nonce Don't add nonce to OCSP request
- disabled as '--no-nonce'
--load-issuer=file Read issuer certificate from file
- file must pre-exist
--load-cert=file Read certificate to check from file
- file must pre-exist
--load-trust=file Read OCSP trust anchors from file
- prohibits the option 'load-signer'
- file must pre-exist
--load-signer=file Read OCSP response signer from file
- prohibits the option 'load-trust'
- file must pre-exist
--inder Use DER format for input certificates and private keys
- disabled as '--no-inder'
-Q, --load-request=file Read DER encoded OCSP request from file
- file must pre-exist
-S, --load-response=file Read DER encoded OCSP response from file
- file must pre-exist
-v, --version[=arg] output version information and exit
-h, --help display extended usage information and exit
-!, --more-help extended usage information passed thru pager
Options are specified by doubled hyphens and their name or by a single
hyphen and the flag character.
Ocsptool is a program that can parse and print information about OCSP
requests/responses, generate requests and verify responses.
Please send bug reports to: <@PACKAGE_BUGREPORT@>
debug option (-d)
This is the “enable debugging” option. This option takes a number argument. Specifies the debug level.
ask option
This is the “ask an ocsp/http server on a certificate validity” option. This option takes an optional string argument ‘server name|url’.
This option has some usage constraints. It:
- must appear in combination with the following options: load-cert, load-issuer.
Connects to the specified HTTP OCSP server and queries on the validity of the loaded certificate.
ocsptool exit status
One of the following exit values will be returned:
- ‘0 (EXIT_SUCCESS)’
Successful program execution.
- ‘1 (EXIT_FAILURE)’
The operation failed or the command syntax was not valid.
ocsptool See Also
ocsptool Examples
Print information about an OCSP request
To parse an OCSP request and print information about the content, the
-i or --request-info parameter may be used as follows.
The -Q parameter specify the name of the file containing the
OCSP request, and it should contain the OCSP request in binary DER
format.
$ ocsptool -i -Q ocsp-request.der
The input file may also be sent to standard input like this:
$ cat ocsp-request.der | ocsptool --request-info
Print information about an OCSP response
Similar to parsing OCSP requests, OCSP responses can be parsed using
the -j or --response-info as follows.
$ ocsptool -j -Q ocsp-response.der $ cat ocsp-response.der | ocsptool --response-info
Generate an OCSP request
The -q or --generate-request parameters are used to
generate an OCSP request. By default the OCSP request is written to
standard output in binary DER format, but can be stored in a file
using --outfile. To generate an OCSP request the issuer of the
certificate to check needs to be specified with --load-issuer
and the certificate to check with --load-cert. By default PEM
format is used for these files, although --inder can be used to
specify that the input files are in DER format.
$ ocsptool -q --load-issuer issuer.pem --load-cert client.pem \
--outfile ocsp-request.der
When generating OCSP requests, the tool will add an OCSP extension
containing a nonce. This behaviour can be disabled by specifying
--no-nonce.
Verify signature in OCSP response
To verify the signature in an OCSP response the -e or
--verify-response parameter is used. The tool will read an
OCSP response in DER format from standard input, or from the file
specified by --load-response. The OCSP response is verified
against a set of trust anchors, which are specified using
--load-trust. The trust anchors are concatenated certificates
in PEM format. The certificate that signed the OCSP response needs to
be in the set of trust anchors, or the issuer of the signer
certificate needs to be in the set of trust anchors and the OCSP
Extended Key Usage bit has to be asserted in the signer certificate.
$ ocsptool -e --load-trust issuer.pem \
--load-response ocsp-response.der
The tool will print status of verification.
Verify signature in OCSP response against given certificate
It is possible to override the normal trust logic if you know that a
certain certificate is supposed to have signed the OCSP response, and
you want to use it to check the signature. This is achieved using
--load-signer instead of --load-trust. This will load
one certificate and it will be used to verify the signature in the
OCSP response. It will not check the Extended Key Usage bit.
$ ocsptool -e --load-signer ocsp-signer.pem \
--load-response ocsp-response.der
This approach is normally only relevant in two situations. The first
is when the OCSP response does not contain a copy of the signer
certificate, so the --load-trust code would fail. The second
is if you want to avoid the indirect mode where the OCSP response
signer certificate is signed by a trust anchor.
Real-world example
Here is an example of how to generate an OCSP request for a
certificate and to verify the response. For illustration we’ll use
the blog.josefsson.org host, which (as of writing) uses a
certificate from CACert. First we’ll use gnutls-cli to get a
copy of the server certificate chain. The server is not required to
send this information, but this particular one is configured to do so.
$ echo | gnutls-cli -p 443 blog.josefsson.org --print-cert > chain.pem
Use a text editor on chain.pem to create three files for each
separate certificates, called cert.pem for the first
certificate for the domain itself, secondly issuer.pem for the
intermediate certificate and root.pem for the final root
certificate.
The domain certificate normally contains a pointer to where the OCSP
responder is located, in the Authority Information Access Information
extension. For example, from certtool -i < cert.pem there is
this information:
Authority Information Access Information (not critical): Access Method: 1.3.6.1.5.5.7.48.1 (id-ad-ocsp) Access Location URI: http://ocsp.CAcert.org/
This means the CA support OCSP queries over HTTP. We are now ready to create a OCSP request for the certificate.
$ ocsptool --ask ocsp.CAcert.org --load-issuer issuer.pem \
--load-cert cert.pem --outfile ocsp-response.der
The request is sent via HTTP to the OCSP server address specified. If the address is ommited ocsptool will use the address stored in the certificate.
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