Section: OpenSSL (1)
ca - sample minimal CA application
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.
- -name section
specifies the configuration file section to use (overrides
default_ca in the ca section).
- -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 SPKAC FORMAT
section for information on the required input and output 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 in PEM format (except that -spkac outputs DER format).
- -outdir directory
the directory to output certificates to. The certificate will be
written to a filename consisting of the serial number in hex with
the CA certificate file.
- -keyfile filename
the private key to sign requests with.
- -keyform PEM|DER
the format of the data in the private key file.
The default is PEM.
- -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.
indicates the issued certificates are to be signed with the key
the certificate requests were signed with (given with -keyfile).
Cerificate requests signed with a different key are ignored. If
-spkac, -ss_cert or -gencrl are given, -selfsign is
A consequence of using -selfsign is that the self-signed
certificate appears among the entries in the certificate database
(see the configuration option database), and uses the same
serial number counter as all other certificates sign with the
- -passin arg
the key password source. For more information about the format of arg
see 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 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.
The DN of a certificate can contain the EMAIL field if present in the
request DN, however it is good policy just having the e-mail set into
the altName extension of the certificate. When this option is set the
EMAIL field is removed from the certificate' subject and set only in
the, eventually present, extensions. The email_in_dn keyword can be
used in the configuration file to enable this behaviour.
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 (defaults to x509_extensions
unless the -extfile option is used). 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. See the
x509v3_config(5) manual page for details of the
extension section format.
- -extfile file
an additional configuration file to read certificate extensions from
(using the default section unless the -extensions option is also
- -engine id
specifying an engine (by its unique id string) will cause ca
to attempt to obtain a functional reference to the specified engine,
thus initialising it if needed. The engine will then be set as the default
for all available algorithms.
- -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.
this option causes field values to be interpreted as UTF8 strings, by
default they are interpreted as ASCII. This means that the field
values, whether prompted from a terminal or obtained from a
configuration file, must be valid UTF8 strings.
this option causes the -subj argument to be interpretedt with full
support for multivalued RDNs. Example:
If -multi-rdn is not used then the UID value is 123456+CN=John Doe.
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.
- -status serial
displays the revocation status of the certificate with the specified
serial number and exits.
Updates the database index to purge expired certificates.
- -crl_reason reason
revocation reason, where reason is one of: unspecified, keyCompromise,
CACompromise, affiliationChanged, superseded, cessationOfOperation,
certificateHold or removeFromCRL. The matching of reason is case
insensitive. Setting any revocation reason will make the CRL v2.
In practive removeFromCRL is not particularly useful because it is only used
in delta CRLs which are not currently implemented.
- -crl_hold instruction
This sets the CRL revocation reason code to certificateHold and the hold
instruction to instruction which must be an OID. Although any OID can be
used 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 to
time. 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 to
- -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. See
x509v3_config(5) manual page for details of the
extension section format.
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 to
be used must be named in the default_ca
option of the ca
of the configuration file (or in the default section of the
configuration file). Besides default_ca
, the following options are
read directly from the ca
With the exception of RANDFILE
, this is probably a bug and may
change in future releases.
Many of the configuration file options 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
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
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
- 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.
if the value yes is given, the valid certificate entries in the
database must have unique subjects. if the value no is given,
several valid certificate entries may have the exact same subject.
The default value is yes, to be compatible with older (pre 0.9.8)
versions of OpenSSL. However, to make CA certificate roll-over easier,
it's recommended to use the value no, especially if combined with
the -selfsign command line option.
Note that it is valid in some circumstances for certificates to be created
without any subject. In the case where there are multiple certificates without
subjects this does not count as a duplicate.
a text file containing the next serial number to use in hex. Mandatory.
This file must be present and contain a valid serial number.
a text file containing the next CRL number to use in hex. The crl number
will be inserted in the CRLs only if this file exists. If this file is
present, it must contain a valid CRL 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 removed
from the DN of the certificate simply set this to 'no'. If not present
the 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 section
for more information.
- name_opt, cert_opt
these options allow the format used to display the certificate details
when asking the user to confirm signing. All the options supported by
the x509 utilities -nameopt and -certopt switches can be used
here, except the no_signame and no_sigdump are permanently set
and cannot be disabled (this is because the certificate signature cannot
be displayed because the certificate has not been signed at this point).
For convenience the values ca_default are accepted by both to produce
a reasonable output.
If neither option is present the format used in earlier versions of
OpenSSL is used. Use of the old format is strongly discouraged because
it only displays fields mentioned in the policy section, mishandles
multicharacter 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 are
ignored and not copied to the certificate. If set to copy then any
extensions present in the request that are not already present are copied
to the certificate. If set to copyall then all extensions in the
request are copied to the certificate: if the extension is already present
in the certificate it is deleted first. See the WARNINGS section before
using this option.
The main use of this option is to allow a certificate request to supply
values for certain extensions such as subjectAltName.
The policy section consists of a set of variables corresponding to
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
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 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 '.'.
When processing SPKAC format, the output is DER if the -out
flag is used, but PEM format if sending to stdout or the -outdir
flag is used.
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
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
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):
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
name_opt = ca_default # Subject name display option
cert_opt = 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 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
however there is no option to do this.
V2 CRL features like delta CRLs 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.
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. To
enforce the absence of the EMAIL field within the DN, as suggested by
RFCs, regardless the contents of the request' subject the -noemailDN
option can be used. The behaviour should be more friendly and
Cancelling some commands by refusing to certify a certificate can
create an empty file.
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 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 is
done on the various files and attempts to run more than one ca command
on the same database can have unpredictable results.
The copy_extensions option should be used with caution. If care is
not taken then it can be a security risk. For example if a certificate
request contains a basicConstraints extension with CA:TRUE and the
copy_extensions value is set to copyall and the user does not spot
this when the certificate is displayed then this will hand the requestor
a valid CA certificate.
This situation can be avoided by setting copy_extensions to copy
and including basicConstraints with CA:FALSE in the configuration file.
Then if the request contains a basicConstraints extension it will be
It is advisable to also include values for other extensions such
as 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.