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Section: OpenSSL (1)
ca - sample minimal CA application
command is a minimal CA
application. It can be usedto sign certificate requests in a variety of forms and generateCRLs it also maintains a text database of issued certificatesand their status.
The options descriptions will be divided into each purpose.
- -config filename
- specifies the configuration file to use.
- -name section
- specifies the configuration file section to use (overridesdefault_ca in the ca section).
- -in filename
- an input filename containing a single certificate request to besigned 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 challengeand additional field values to be signed by the CA. See the SPKAC FORMATsection for information on the required format.
- if present this should be the last option, all subsequent argumentsare assumed to the the names of files containing certificate requests.
- -out filename
- the output file to output certificates to. The default is standardoutput. The certificate details will also be printed out to thisfile.
- -outdir directory
- the directory to output certificates to. The certificate will bewritten 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 somesystems the command line arguments are visible (e.g. Unix withthe 'ps' utility) this option should be used with caution.
- -passin arg
- the key password source. For more information about the format of argsee the PASS PHRASE ARGUMENTS section in openssl(1).
- 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 thedate is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure).
- -enddate date
- this allows the expiry date to be explicitly set. The format of thedate 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 inthe configuration file which decides which fields should be mandatoryor match the CA certificate. Check out the POLICY FORMAT sectionfor more information.
- this is a legacy option to make ca work with very old versions ofthe IE certificate enrollment control ``certenr3''. It used UniversalStringsfor almost everything. Since the old control has various security bugsits use is strongly discouraged. The newer control ``Xenroll'' does notneed this option.
- Normally the DN order of a certificate is the same as the order of thefields in the relevant policy section. When this option is set the order is the same as the request. This is largely for compatibility with theolder IE enrollment control which would only accept certificates if theirDNs match the order of the request. This is not needed for Xenroll.
- The DN of a certificate can contain the EMAIL field if present in therequest DN, however it is good policy just having the e-mail set intothe altName extension of the certificate. When this option is set theEMAIL field is removed from the certificate' subject and set only inthe, eventually present, extensions. The email_in_dn keyword can beused in the configuration file to enable this behaviour.
- this sets the batch mode. In this mode no questions will be askedand all certificates will be certified automatically.
- -extensions section
- the section of the configuration file containing certificate extensionsto be added when a certificate is issued (defaults to x509_extensionsunless the -extfile option is used). If no extension section ispresent then, a V1 certificate is created. If the extension sectionis present (even if it is empty), then a V3 certificate is created.
- -extfile file
- an additional configuration file to read certificate extensions from(using the default section unless the -extensions option is alsoused).
- -engine id
- specifying an engine (by it's unique id string) will cause reqto attempt to obtain a functional reference to the specified engine,thus initialising it if needed. The engine will then be set as the defaultfor all available algorithms.
- 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 fromnow 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.
- -crl_reason reason
- revocation reason, where reason is one of: unspecified, keyCompromise,CACompromise, affiliationChanged, superseded, cessationOfOperation,certificateHold or removeFromCRL. The matching of reason is caseinsensitive. Setting any revocation reason will make the CRL v2.
In practive removeFromCRL is not particularly useful because it is only usedin delta CRLs which are not currently implemented.
- -crl_hold instruction
- This sets the CRL revocation reason code to certificateHold and the holdinstruction to instruction which must be an OID. Although any OID can beused only holdInstructionNone (the use of which is discouraged by RFC2459)holdInstructionCallIssuer or holdInstructionReject will normally be used.
- -crl_compromise time
- This sets the revocation reason to keyCompromise and the compromise time totime. time should be in GeneralizedTime format that is YYYYMMDDHHMMSSZ.
- -crl_CA_compromise time
- This is the same as crl_compromise except the revocation reason is set toCACompromise.
- -subj arg
- supersedes subject name given in the request.The arg must be formatted as /type0=value0/type1=value1/type2=...,characters may be escaped by \ (backslash), no spaces are skipped.
- -crlexts section
- the section of the configuration file containing CRL extensions toinclude. If no CRL extension section is present then a V1 CRL iscreated, if the CRL extension section is present (even if it isempty) then a V2 CRL is created. The CRL extensions specified areCRL extensions and not CRL entry extensions. It should be notedthat some software (for example Netscape) can't handle V2 CRLs.
CONFIGURATION FILE OPTIONS
The section of the configuration file containing options for ca
is found as follows: If the -name
command line option is used,then it names the section to be used. Otherwise the section tobe used must be named in the default_ca
option of the ca
sectionof the configuration file (or in the default section of theconfiguration file). Besides default_ca
, the following options areread directly from the ca
msie_hackWith the exception of RANDFILE
, this is probably a bug and maychange in future releases.
Many of the configuration file options are identical to command lineoptions. Where the option is present in the configuration fileand the command line the command line value is used. Where anoption is described as mandatory then it must be present inthe configuration file or the command line equivalent (ifany) used.
- This specifies a file containing additional OBJECT IDENTIFIERS.Each line of the file should consist of the numerical form of theobject identifier followed by white space then the short name followedby white space and finally the long name.
- This specifies a section in the configuration file containing extraobject identifiers. Each line should consist of the short name of theobject identifier followed by = and the numerical form. The shortand long names are the same when this option is used.
- the same as the -outdir command line option. It specifiesthe directory where new certificates will be placed. Mandatory.
- the same as -cert. It gives the file containing the CAcertificate. Mandatory.
- same as the -keyfile option. The file containing theCA private key. Mandatory.
- a file used to read and write random number seed information, oran EGD socket (see RAND_egd(3)).
- the same as the -days option. The number of days to certifya certificate for.
- the same as the -startdate option. The start date to certifya certificate for. If not set the current time is used.
- the same as the -enddate option. Either this option ordefault_days (or the command line equivalents) must bepresent.
- default_crl_hours default_crl_days
- the same as the -crlhours and the -crldays options. Thesewill only be used if neither command line option is present. Atleast 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 presentthough 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 -noemailDN. If you want the EMAIL field to be removedfrom the DN of the certificate simply set this to 'no'. If not presentthe default is to allow for the EMAIL filed in the certificate's DN.
- the same as -msie_hack
- the same as -policy. Mandatory. See the POLICY FORMAT sectionfor more information.
- nameopt, certopt
- these options allow the format used to display the certificate detailswhen asking the user to confirm signing. All the options supported bythe x509 utilities -nameopt and -certopt switches can be usedhere, except the no_signame and no_sigdump are permanently setand cannot be disabled (this is because the certificate signature cannotbe displayed because the certificate has not been signed at this point).
For convenience the values ca_default are accepted by both to producea reasonable output.
If neither option is present the format used in earlier versions ofOpenSSL is used. Use of the old format is strongly discouraged becauseit only displays fields mentioned in the policy section, mishandlesmulticharacter string types and does not display extensions.
- determines how extensions in certificate requests should be handled.If set to none or this option is not present then extensions areignored and not copied to the certificate. If set to copy then anyextensions present in the request that are not already present are copiedto the certificate. If set to copyall then all extensions in therequest are copied to the certificate: if the extension is already presentin the certificate it is deleted first. See the WARNINGS section beforeusing this option.
The main use of this option is to allow a certificate request to supplyvalues for certain extensions such as subjectAltName.
The policy section consists of a set of variables corresponding tocertificate DN
fields. If the value is ``match'' then the field valuemust match the same field in the CA
certificate. If the value is``supplied'' then it must be present. If the value is ``optional'' thenit may be present. Any fields not mentioned in the policy sectionare silently deleted, unless the -preserveDN
option is set butthis can be regarded more of a quirk than intended behaviour.
The input to the -spkac
command line option is a Netscapesigned public key and challenge. This will usually come fromthe KEYGEN
tag in an HTML
form to create a new private key. It is however possible to create SPKACs using the spkac
The file should contain the variable SPKAC set to the value ofthe SPKAC and also the required DN components as name value pairs.If you need to include the same component twice then it can bepreceded by a number and a '.'.
Note: these examples assume that the ca
directory structure isalready set up and the relevant files already exist. This usuallyinvolves creating a CA
certificate and private key with req
, aserial number file and an empty index file and placing them inthe relevant directories.
To use the sample configuration file below the directories demoCA,demoCA/private and demoCA/newcerts would be created. The CAcertificate would be copied to demoCA/cacert.pem and its privatekey to demoCA/private/cakey.pem. A file demoCA/serial would becreated containing for example ``01'' and the empty index filedemoCA/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):
SPKAC=MIG0MGAwXDANBgkqhkiG9w0BAQEFAANLADBIAkEAn7PDhCeV/xIxUg8V70YRxK2A5 CN=Steve Test emailAddress=steveAATTopenssl.org 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 email_in_dn = no # Don't add the email into cert DN
nameopt = ca_default # Subject name display option certopt = ca_default # Certificate display option copy_extensions = none # Don't copy extensions from request
[ policy_any ] countryName = supplied stateOrProvinceName = optional organizationName = optional organizationalUnitName = optional commonName = supplied emailAddress = optional
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
reflects the location of master configuration file it canbe 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 possibleto rebuild the index file from all the issued certificates and a currentCRL:
however there is no option to do this.
V2 CRL features like delta CRL support and CRL numbers are not currentlysupported.
Although several requests can be input and handled at once it is onlypossible to include one SPKAC or self signed certificate.
The use of an in memory text database can cause problems when largenumbers of certificates are present because, as the name impliesthe database has to be kept in memory.
It is not possible to certify two certificates with the same DN: thisis a side effect of how the text database is indexed and it cannot easilybe fixed without introducing other problems. Some S/MIME clients can usetwo certificates with the same DN for separate signing and encryptionkeys.
The ca command really needs rewriting or the required functionalityexposed at either a command or interface level so a more friendly utility(perl script or GUI) can handle things properly. The scripts CA.sh andCA.pl help a little but not very much.
Any fields in a request that are not present in a policy are silentlydeleted. This does not happen if the -preserveDN option is used. Toenforce the absence of the EMAIL field within the DN, as suggested byRFCs, regardless the contents of the request' subject the -noemailDNoption can be used. The behaviour should be more friendly andconfigurable.
Cancelling some commands by refusing to certify a certificate cancreate an empty file.
command is quirky and at times downright unfriendly.
The ca utility was originally meant as an example of how to do thingsin a CA. It was not supposed to 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 isdone on the various files and attempts to run more than one ca commandon the same database can have unpredictable results.
The copy_extensions option should be used with caution. If care isnot taken then it can be a security risk. For example if a certificaterequest contains a basicConstraints extension with CA:TRUE and thecopy_extensions value is set to copyall and the user does not spotthis when the certificate is displayed then this will hand the requestora valid CA certificate.
This situation can be avoided by setting copy_extensions to copyand including basicConstraints with CA:FALSE in the configuration file.Then if the request contains a basicConstraints extension it will beignored.
It is advisable to also include values for other extensions suchas keyUsage to prevent a request supplying its own values.
Additional restrictions can be placed on the CA certificate itself.For example if the CA certificate has:
basicConstraints = CA:TRUE, pathlen:0
then even if a certificate is issued with CA:TRUE it will not be valid.
- CA OPTIONS
- CRL OPTIONS
- CONFIGURATION FILE OPTIONS
- POLICY FORMAT
- SPKAC FORMAT
- ENVIRONMENT VARIABLES
- SEE ALSO
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