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.
OPTIONS
This command operates as either a client or a server. The options are described below, divided into those two modes.
OCSP Client Options
-help
Print out a usage message.
-out filename
specify output filename, default is standard output.
-issuer filename
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.
-cert filename
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.
-serial num
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.
-signer filename, -signkey filename
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.
-sign_other filename
Additional certificates to include in the signed request.
-nonce, -no_nonce
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.
-req_text, -resp_text, -text
print out the text form of the OCSP request, response or both respectively.
-reqout file, -respout file
write out the DER encoded certificate request or response to file.
-reqin file, -respin file
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).
-url responder_url
specify the responder URL. Both HTTP and HTTPS (SSL/TLS) URLs can be specified.
-host hostname:port, -path pathname
if the host option is present then the OCSP request is sent to the host hostname on port port. path specifies the HTTP path name to use or "/" by default. This is equivalent to specifying -url with scheme http:// and the given hostname, port, and pathname.
-header name=value
Adds the header name with the specified value to the OCSP request that is sent to the responder. This may be repeated.
-timeout seconds
connection timeout to the OCSP responder in seconds
-CAfile file, -CApath pathname
file or pathname containing trusted CA certificates. These are used to verify the signature on the OCSP response.
-no-CAfile
Do not load the trusted CA certificates from the default file location
-no-CApath
Do not load the trusted CA certificates from the default directory location
indexfile is 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.
-CA file
CA certificate corresponding to the revocation information in indexfile.
-rsigner file
The certificate to sign OCSP responses with.
-rother file
Additional certificates to include in the OCSP response.
-resp_no_certs
Don't include any certificates in the OCSP response.
-resp_key_id
Identify the signer certificate using the key ID, default is to use the subject name.
-rkey file
The private key to sign OCSP responses with: if not present the file specified in the rsigner option is used.
-port portnum
Port to listen for OCSP requests on. The port may also be specified using the url option.
-nrequest number
The OCSP server will exit after receiving number requests, default unlimited.
-nmin minutes, -ndays days
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 verification.
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:
Alternatively the responder certificate itself can be explicitly trusted with the -VAfile option.
NOTES
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.
The -no_alt_chains options was first added to OpenSSL 1.1.0.
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Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.