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] [-sigopt nm:v] [-create_serial]
[-rand_serial] [-multivalue-rdn] [-rand 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.
- -config filename
- Specifies the configuration file to use. Optional; for a description of
the default value, see "COMMAND SUMMARY" in
- -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
- -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
- If present this should be the last option, all subsequent arguments are
taken as 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 ".pem"
- 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.
- -sigopt nm:v
- Pass options to the signature algorithm during sign or verify operations.
Names and values of these options are algorithm-specific.
- -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).
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
- -passin arg
- The key password source. For more information about the format of
arg see "Pass Phrase Options" in openssl(1).
- 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), or YYYYMMDDHHMMSSZ
(the same as an ASN1 GeneralizedTime structure). In both formats, seconds
SS and timezone Z must be present.
- -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), or
YYYYMMDDHHMMSSZ (the same as an ASN1 GeneralizedTime structure). In both
formats, seconds SS and timezone Z must be present.
- -days arg
- The number of days to certify the certificate for.
- -md alg
- 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.
- -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
- 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 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
- -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=.... Keyword characters may be
escaped by \ (backslash), and whitespace is retained. Empty values are
permitted, but the corresponding type will not be included in the
- 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
- 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
- -rand file...
- 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.
- [-writerand file]
- Writes random data to the specified file upon exit. This can be
used with a subsequent -rand flag.
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.
- 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.
- -valid filename
- A filename containing a certificate to add a Valid certificate entry.
- -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 practice removeFromCRL is not particularly useful
because it is only used in delta CRLs which are not currently
- -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
- -crl_CA_compromise time
- This is the same as crl_compromise except the revocation reason is
set to CACompromise.
- -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.
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.
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.
- 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
- 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. 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 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 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
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
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
A sample configuration file with the relevant sections for
[ 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
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 ignored.
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
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
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