ocsptool(1) - Man pages

ocsptool(1) User Commands ocsptool(1)

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 de-
termine 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 an-
chors (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 an-
chors 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.

-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 parame-
ter 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 con-
taining 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 cer-
tificates 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 Ex-
tended 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 cer-
tificate, so the --load-trust code would fail. The second is if you
want to avoid the indirect mode where the OCSP response signer certifi-
cate 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.josef-
sson.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 re-
sponder is located, in the Authority Information Access Information ex-
tension. For example, from certtool -i < chain.pem there is this in-
formation:

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.