Ubuntu Manpage: ocsptool - GnuTLS OCSP tool

Provided by: gnutls-bin_3.4.10-4ubuntu1.9_amd64

NAME

       ocsptool - GnuTLS OCSP tool

SYNOPSIS

       ocsptool [-flags] [-flag [value]] [--option-name[[=| ]value]]

       All arguments must be options.

DESCRIPTION

       Ocsptool  is  a  program  that  can  parse  and print information about OCSP requests/responses, generate
       requests and verify responses.

OPTIONS

-d number, --debug=number Enable debugging. This option takes an integer number as its argument. The
value of number is constrained to being:
in the range 0 through 9999

Specifies the debug level.

-V, --verbose More verbose output. This option may appear an unlimited number of times.

--infile=file Input file.

--outfile=string Output file.

--ask [=server name|url] Ask an OCSP/HTTP server on a certificate validity. This option 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.

-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, - Fl -no-nonce Use (or not) a nonce to OCSP request. The no-nonce form will disable the option.

--load-issuer=file Read issuer certificate from file.

--load-cert=file Read certificate to check from file.

--load-trust=file Read OCSP trust anchors from file. This option must not appear in combination with any
of the following options: load-signer.

--load-signer=file Read OCSP response signer from file. This option must not appear in combination with
any of the following options: load-trust.

--inder, - Fl -no-inder Use DER format for input certificates and private keys. The no-inder form will
disable the option.

-Q file, --load-request=file Read DER encoded OCSP request from file.

-S file, --load-response=file Read DER encoded OCSP response from file.

-h, --help Display usage information and exit.

-!, --more-help Pass the extended usage information through a pager.

-v [{v|c|n --version [{v|c|n}]}] Output version of program and exit. The default mode is `v', a simple
version. The `c' mode will print copyright information and `n' will print the full copyright notice.

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.

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.

       70  (EX_SOFTWARE) libopts had an internal operational error.  Please report it to autogen-
       users@lists.sourceforge.net.  Thank you.

       SEE ALSO
                  certtool (1)

AUTHORS

       Nikos Mavrogiannopoulos, Simon Josefsson and others; see  /usr/share/doc/gnutls/AUTHORS  for  a  complete
       list.

COPYRIGHT

       Copyright  (C)  2000-2016  Free  Software  Foundation,  and  others all rights reserved.  This program is
       released under the terms of the GNU General Public License, version 3 or later.

BUGS

       Please send bug reports to: bugs@gnutls.org

NOTES

       This manual page was AutoGen-erated from the ocsptool option definitions.

3.4.10                                             2021-08-27                                        ocsptool(1)