CA(1SSL) OpenSSL CA(1SSL)
openssl-ca, ca - sample minimal CA application
openssl ca [-help] [-verbose] [-config filename] [-name section]
[-gencrl] [-revoke file] [-valid file] [-status serial] [-updatedb]
[-crl_reason reason] [-crl_hold instruction] [-crl_compromise time]
[-crl_CA_compromise time] [-crldays days] [-crlhours hours] [-crlexts
section] [-startdate date] [-enddate date] [-days arg] [-md arg]
[-policy arg] [-keyfile arg] [-keyform PEM|DER] [-key arg] [-passin
arg] [-cert file] [-selfsign] [-in file] [-out file] [-notext] [-outdir
dir] [-infiles] [-spkac file] [-ss_cert file] [-preserveDN]
[-noemailDN] [-batch] [-msie_hack] [-extensions section] [-extfile
section] [-engine id] [-subj arg] [-utf8] [-create_serial]
[-rand_serial] [-multivalue-rdn] [-rand file...] [-writerand file]
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.
Print out a usage message.
This prints extra details about the operations being performed.
Specifies the configuration file to use. Optional; for a
description of the default value, see "COMMAND SUMMARY" in
Specifies the configuration file section to use (overrides
default_ca in the ca section).
An input filename containing a single certificate request to be
signed by the CA.
A single self-signed certificate to be signed by the CA.
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
If present this should be the last option, all subsequent arguments
are taken as the names of files containing certificate requests.
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).
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.
The private key to sign requests with.
The format of the data in the private key file. The default is
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).
Certificate requests signed with a different key are ignored. If
-spkac, -ss_cert or -gencrl are given, -selfsign is ignored.
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 self-signed
The key password source. For more information about the format of
arg see the PASS PHRASE ARGUMENTS section in openssl(1).
Don't output the text form of a certificate to the output file.
This allows the start date to be explicitly set. The format of the
date is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure), or
YYYYMMDDHHMMSSZ (the same as an ASN1 GeneralizedTime structure). In
both formats, seconds SS and timezone Z must be present.
This allows the expiry date to be explicitly set. The format of the
date is YYMMDDHHMMSSZ (the same as an ASN1 UTCTime structure), or
YYYYMMDDHHMMSSZ (the same as an ASN1 GeneralizedTime structure). In
both formats, seconds SS and timezone Z must be present.
The number of days to certify the certificate for.
The message digest to use. Any digest supported by the OpenSSL
dgst command can be used. For signing algorithms that do not
support a digest (i.e. Ed25519 and Ed448) any message digest that
is set is ignored. This option also applies to CRLs.
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 deprecated 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.
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
This sets the batch mode. In this mode no questions will be asked
and all certificates will be certified automatically.
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:w x509v3_config(5) manual page for
details of the extension section format.
An additional configuration file to read certificate extensions
from (using the default section unless the -extensions option is
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.
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.
If reading serial from the text file as specified in the
configuration fails, specifying this option creates a new random
serial to be used as next serial number. To get random serial
numbers, use the -rand_serial flag instead; this should only be
used for simple error-recovery.
Generate a large random number to use as the serial number. This
overrides any option or configuration to use a serial number file.
This option causes the -subj argument to be interpreted with full
support for multivalued RDNs. Example:
If -multi-rdn is not used then the UID value is 123456+CN=John Doe.
A file or files containing random data used to seed the random
number generator. Multiple files can be specified separated by an
OS-dependent character. The separator is ; for MS-Windows, , for
OpenVMS, and : for all others.
Writes random data to the specified file upon exit. This can be
used with a subsequent -rand flag.
This option generates a CRL based on information in the index file.
The number of days before the next CRL is due. That is the days
from now to place in the CRL nextUpdate field.
The number of hours before the next CRL is due.
A filename containing a certificate to revoke.
A filename containing a certificate to add a Valid certificate
Displays the revocation status of the certificate with the
specified serial number and exits.
Updates the database index to purge expired certificates.
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 practice removeFromCRL is not particularly useful because it is
only used in delta CRLs which are not currently implemented.
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.
This sets the revocation reason to keyCompromise and the compromise
time to time. time should be in GeneralizedTime format that is
This is the same as crl_compromise except the revocation reason is
set to CACompromise.
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
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 section 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
msie_hack 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 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.
Same as the -keyfile option. The file containing the CA private
At startup the specified file is loaded into the random number
generator, and at exit 256 bytes will be written to it.
The same as the -days option. The number of days to certify a
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.
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. Mandatory except where the signing
algorithm does not require a digest (i.e. Ed25519 and Ed448).
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
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
The same as -msie_hack
The same as -policy. Mandatory. See the POLICY FORMAT section for
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
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
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 '.'.
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, a serial number
file and an empty index file and placing them in the relevant
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):
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
#rand_serial = yes # for random serial#'s
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
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.
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 script
CA.pl helps 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
Canceling some commands by refusing to certify a certificate can create
an empty file.
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 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 requester 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.
Since OpenSSL 1.1.1, the program follows RFC5280. Specifically,
certificate validity period (specified by any of -startdate, -enddate
and -days) will be encoded as UTCTime if the dates are earlier than
year 2049 (included), and as GeneralizedTime if the dates are in year
2050 or later.
req(1), spkac(1), x509(1), CA.pl(1), config(5), x509v3_config(5)
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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
1.1.1 2022-07-04 CA(1SSL)
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