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ISBN : 978-2-7460-9712-4
EAN : 9782746097124
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CentOS 2.1AS







ca − sample minimal CA application


openssl ca [−verbose] [−config filename] [−name section] [−gencrl] [−revoke file] [−crldays days] [−crlhours hours] [−crlexts section] [−startdate date] [−enddate date] [−days arg] [−md arg] [−policy arg] [−keyfile arg] [−key arg] [−passin arg] [−cert file] [−in file] [−out file] [−notext] [−outdir dir] [−infiles] [−spkac file] [−ss_cert file] [−preserveDN] [−batch] [−msie_hack] [−extensions section]


The ca command is a minimal CA application. It can be used to sign certificate requests in a variety of forms and generate CRLs it also maintains a text database of issued certificates and their status.

The options descriptions will be divided into each purpose.


−config filename

specifies the configuration file to use.

−in filename

an input filename containing a single certificate request to be signed by the CA .

−ss_cert filename

a single self signed certificate to be signed by the CA .

−spkac filename

a file containing a single Netscape signed public key and challenge and additional field values to be signed by the CA . See the NOTES section for information on the required format.


if present this should be the last option, all subsequent arguments are assumed to the the names of files containing certificate requests.

−out filename

the output file to output certificates to. The default is standard output. The certificate details will also be printed out to this file.

−outdir directory

the directory to output certificates to. The certificate will be written to a filename consisting of the serial number in hex with ".pem" appended.


the CA certificate file.

−keyfile filename

the private key to sign requests with.

−key password

the password used to encrypt the private key. Since on some systems the command line arguments are visible (e.g. Unix with the ’ps’ utility) this option should be used with caution.

−passin arg

the key password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1). =item −verbose

this prints extra details about the operations being performed.


don’t output the text form of a certificate to the output file.

−startdate date

this allows the start date to be explicitly set. The format of the date is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure).

−enddate date

this allows the expiry date to be explicitly set. The format of the date is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure).

−days arg

the number of days to certify the certificate for.

−md alg

the message digest to use. Possible values include md5, sha1 and mdc2. This option also applies to CRLs.

−policy arg

this option defines the CA "policy" to use. This is a section in the configuration file which decides which fields should be mandatory or match the CA certificate. Check out the POLICY FORMAT section for more information.


this is a legacy option to make ca work with very old versions of the IE certificate enrollment control "certenr3". It used UniversalStrings for almost everything. Since the old control has various security bugs its use is strongly discouraged. The newer control "Xenroll" does not need this option.


Normally the DN order of a certificate is the same as the order of the fields in the relevant policy section. When this option is set the order is the same as the request. This is largely for compatibility with the older IE enrollment control which would only accept certificates if their DNs match the order of the request. This is not needed for Xenroll.


this sets the batch mode. In this mode no questions will be asked and all certificates will be certified automatically.

−extensions section

the section of the configuration file containing certificate extensions to be added when a certificate is issued. If no extension section is present then a V1 certificate is created. If the extension section is present (even if it is empty) then a V3 certificate is created.



this option generates a CRL based on information in the index file.

−crldays num

the number of days before the next CRL is due. That is the days from now to place in the CRL nextUpdate field.

−crlhours num

the number of hours before the next CRL is due.

−revoke filename

a filename containing a certificate to revoke.

−crlexts section

the section of the configuration file containing CRL extensions to include. If no CRL extension section is present then a V1 CRL is created, if the CRL extension section is present (even if it is empty) then a V2 CRL is created. The CRL extensions specified are CRL extensions and not CRL entry extensions. It should be noted that some software (for example Netscape) can’t handle V2 CRLs.


The options for ca are contained in the ca section of the configuration file. Many of these are identical to command line options. Where the option is present in the configuration file and the command line the command line value is used. Where an option is described as mandatory then it must be present in the configuration file or the command line equivalent (if any) used.

This specifies a file containing additional OBJECT IDENTIFIERS . Each line of the file should consist of the numerical form of the object identifier followed by white space then the short name followed by white space and finally the long name.


This specifies a section in the configuration file containing extra object identifiers. Each line should consist of the short name of the object identifier followed by = and the numerical form. The short and long names are the same when this option is used.


the same as the −outdir command line option. It specifies the directory where new certificates will be placed. Mandatory.


the same as −cert. It gives the file containing the CA certificate. Mandatory.


same as the −keyfile option. The file containing the CA private key. Mandatory.


a file used to read and write random number seed information, or an EGD socket (see RAND_egd(3)).


the same as the −days option. The number of days to certify a certificate for.


the same as the −startdate option. The start date to certify a certificate for. If not set the current time is used.


the same as the −enddate option. Either this option or default_days (or the command line equivalents) must be present.

default_crl_hours default_crl_days

the same as the −crlhours and the −crldays options. These will only be used if neither command line option is present. At least one of these must be present to generate a CRL .


the same as the −md option. The message digest to use. Mandatory.


the text database file to use. Mandatory. This file must be present though initially it will be empty.


a text file containing the next serial number to use in hex. Mandatory. This file must be present and contain a valid serial number.


the same as −extensions.


the same as −crlexts.


the same as −preserveDN


the same as −msie_hack


the same as −policy. Mandatory. See the POLICY FORMAT section for more information.


The policy section consists of a set of variables corresponding to certificate DN fields. If the value is "match" then the field value must match the same field in the CA certificate. If the value is "supplied" then it must be present. If the value is "optional" then it may be present. Any fields not mentioned in the policy section are silently deleted, unless the −preserveDN option is set but this can be regarded more of a quirk than intended behaviour.


The input to the −spkac command line option is a Netscape signed public key and challenge. This will usually come from the KEYGEN tag in an HTML form to create a new private key. It is however possible to create SPKACs using the spkac utility.

The file should contain the variable SPKAC set to the value of the SPKAC and also the required DN components as name value pairs. If you need to include the same component twice then it can be preceded by a number and a ’.’.


Note: these examples assume that the ca directory structure is already set up and the relevant files already exist. This usually involves creating a CA certificate and private key with req, a serial number file and an empty index file and placing them in the relevant directories.

To use the sample configuration file below the directories demoCA, demoCA/private and demoCA/newcerts would be created. The CA certificate would be copied to demoCA/cacert.pem and its private key to demoCA/private/cakey.pem. A file demoCA/serial would be created containing for example "01" and the empty index file demoCA/index.txt.

Sign a certificate request:

 openssl ca -in req.pem -out newcert.pem

Sign a certificate request, using CA extensions:

 openssl ca -in req.pem -extensions v3_ca -out newcert.pem

Generate a CRL

 openssl ca -gencrl -out crl.pem

Sign several requests:

 openssl ca -infiles req1.pem req2.pem req3.pem

Certify a Netscape SPKAC:

 openssl ca -spkac spkac.txt

A sample SPKAC file (the SPKAC line has been truncated for clarity):

 CN=Steve Test
 0.OU=OpenSSL Group
 1.OU=Another Group

A sample configuration file with the relevant sections for ca:

 [ ca ]
 default_ca      = CA_default            # The default ca section
 [ CA_default ]
 dir            = ./demoCA              # top dir
 database       = $dir/index.txt        # index file.
 new_certs_dir  = $dir/newcerts         # new certs dir
 certificate    = $dir/cacert.pem       # The CA cert
 serial         = $dir/serial           # serial no file
 private_key    = $dir/private/cakey.pem# CA private key
 RANDFILE       = $dir/private/.rand    # random number file
 default_days   = 365                   # how long to certify for
 default_crl_days= 30                   # how long before next CRL
 default_md     = md5                   # md to use
 policy         = policy_any            # default policy

 [ policy_any ]
 countryName            = supplied
 stateOrProvinceName    = optional
 organizationName       = optional
 organizationalUnitName = optional
 commonName             = supplied
 emailAddress           = optional


The ca command is quirky and at times downright unfriendly.

The ca utility was originally meant as an example of how to do things in a CA. It was not supposed be be used as a full blown CA itself: nevertheless some people are using it for this purpose.

The ca command is effectively a single user command: no locking is done on the various files and attempts to run more than one ca command on the same database can have unpredictable results.


Note: the location of all files can change either by compile time options, configuration file entries, environment variables or command line options. The values below reflect the default values.

 /usr/local/ssl/lib/openssl.cnf - master configuration file
 ./demoCA                       - main CA directory
 ./demoCA/cacert.pem            - CA certificate
 ./demoCA/private/cakey.pem     - CA private key
 ./demoCA/serial                - CA serial number file
 ./demoCA/serial.old            - CA serial number backup file
 ./demoCA/index.txt             - CA text database file
 ./demoCA/index.txt.old         - CA text database backup file
 ./demoCA/certs                 - certificate output file
 ./demoCA/.rnd                  - CA random seed information


OPENSSL_CONF reflects the location of master configuration file it can be overridden by the −config command line option.


The text database index file is a critical part of the process and if corrupted it can be difficult to fix. It is theoretically possible to rebuild the index file from all the issued certificates and a current CRL: however there is no option to do this.

CRL entry extensions cannot currently be created: only CRL extensions can be added.

V2 CRL features like delta CRL support and CRL numbers are not currently supported.

Although several requests can be input and handled at once it is only possible to include one SPKAC or self signed certificate.


The use of an in memory text database can cause problems when large numbers of certificates are present because, as the name implies the database has to be kept in memory.

Certificate request extensions are ignored: some kind of "policy" should be included to use certain static extensions and certain extensions from the request.

It is not possible to certify two certificates with the same DN: this is a side effect of how the text database is indexed and it cannot easily be fixed without introducing other problems. Some S/MIME clients can use two certificates with the same DN for separate signing and encryption keys.

The ca command really needs rewriting or the required functionality exposed at either a command or interface level so a more friendly utility (perl script or GUI) can handle things properly. The scripts CA.sh and CA.pl help a little but not very much.

Any fields in a request that are not present in a policy are silently deleted. This does not happen if the −preserveDN option is used but the extra fields are not displayed when the user is asked to certify a request. The behaviour should be more friendly and configurable.

Cancelling some commands by refusing to certify a certificate can create an empty file.


req(1), spkac(1), x509(1), CA.pl(1), config(5)