Provided by: gnutls-bin_3.8.3-1.1ubuntu3.4_amd64 
NAME
ocsptool - GnuTLS OCSP tool
SYNOPSIS
ocsptool [-flags] [-flag [value]] [--option-name[[=| ]value]]
All arguments must be options.
DESCRIPTION
On verification
Responses are typically signed/issued by designated certificates or certificate authorities and thus this
tool requires on verification the certificate of the issuer or the full certificate chain in order to
determine the appropriate signing authority. The specified certificate of the issuer is assumed trusted.
OPTIONS
-d num, --debug=num Enable debugging. This option takes an integer number as its argument. The value of
num is constrained to being:
in the range 0 through 9999
Specifies the debug level.
-V, --verbose More verbose output.
--infile=file Input file.
--outfile=str Output file.
--ask=server name|url Ask an OCSP/HTTP server on a certificate validity.
Connects to the specified HTTP OCSP server and queries on the validity of the loaded certificate. Its
argument can be a URL or a plain server name. It can be combined with --load-chain, where it checks all
certificates in the provided chain, or with --load-cert and --load-issuer options. The latter checks the
provided certificate against its specified issuer certificate.
-e, --verify-response Verify response.
Verifies the provided OCSP response against the system trust anchors (unless --load-trust is provided).
It requires the --load-signer or --load-chain options to obtain the signer of the OCSP response.
-i, --request-info Print information on a OCSP request.
Display detailed information on the provided OCSP request.
-j, --response-info Print information on a OCSP response.
Display detailed information on the provided OCSP response.
-q, --generate-request Generates an OCSP request.
--nonce, --no-nonce Use (or not) a nonce to OCSP request. The no-nonce form will disable the option.
--load-chain=file Reads a set of certificates forming a chain from file.
--load-issuer=file Reads issuer's certificate from file.
--load-cert=file Reads the 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.
When verifying an OCSP response read the trust anchors from the provided file. When this is not provided,
the system's trust anchors will be used.
--load-signer=file Reads the OCSP response signer from file. This option must not appear in combination
with any of the following options: load-trust.
--inder, --no-inder Use DER format for input certificates and private keys. The no-inder form will
disable the option.
--outder Use DER format for output of responses (this is the default).
The output will be in DER encoded format. Unlike other GnuTLS tools, this is the default for this tool
--outpem Use PEM format for output of responses.
The output will be in PEM format.
-Q file, --load-request=file Reads the DER encoded OCSP request from file.
-S file, --load-response=file Reads the DER encoded OCSP response from file.
--ignore-errors Ignore any verification errors.
--verify-allow-broken Allow broken algorithms, such as MD5 for verification.
This can be combined with --verify-response.
--attime=timestamp Perform validation at the timestamp instead of the system time.
timestamp is an instance in time encoded as Unix time or in a human
readable timestring such as "29 Feb 2004", "2004-02-29". Full documentation available at
<https://www.gnu.org/software/coreutils/manual/html_node/Date-input-formats.html> or locally via info
'(coreutils) date invocation'.
-v arg, --version=arg 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.
-h, --help Display usage information and exit.
-!, --more-help Pass the extended usage information through a pager.
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 --save-cert chain.pem
The saved certificates normally contain a pointer to where the OCSP responder is located, in the
Authority Information Access Information extension. For example, from certtool -i < chain.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: https://ocsp.CAcert.org/
This means that ocsptool can discover the servers to contact over HTTP. We can now request
information on the chain certificates.
$ ocsptool --ask --load-chain chain.pem
The request is sent via HTTP to the OCSP server address found in the certificates. It is possible
to override the address of the OCSP server as well as ask information on a particular certificate
using --load-cert and --load-issuer.
$ ocsptool --ask https://ocsp.CAcert.org/ --load-chain chain.pem
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.
SEE ALSO
certtool (1)
AUTHORS
COPYRIGHT
Copyright (C) 2020-2023 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
3.8.3 16 Jan 2024 ocsptool(1)