NAME
ca - sample minimal CA application
LIBRARY
libcrypto, -lcrypto
SYNOPSIS
openssl ca [
-verbose] [
-config filename] [
-name section] [
-gencrl] [
-revoke 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] [
-multivalue-rdn]
DESCRIPTION
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.
CA OPTIONS
- -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.
- -infiles
- 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
".pem" appended.
- -cert
- 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.
- -selfsign
- 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 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
certificate.
- -passin arg
- the key password source. For more information about the
format of arg see the PASS PHRASE ARGUMENTS section in
openssl(1).
- -verbose
- this prints extra details about the operations being
performed.
- -notext
- 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.
- -msie_hack
- 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.
- -preserveDN
- 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.
- -noemailDN
- 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.
- -batch
- 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:w 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 used).
- -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.
- -utf8
- 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.
- -multivalue-rdn
- this option causes the -subj argument to be interpretedt
with full support for multivalued RDNs. Example:
/DC=org/DC=OpenSSL/DC=users/UID=123456+CN=John Doe
If -multi-rdn is not used then the UID value is 123456+CN=John
Doe.
CRL OPTIONS
- -gencrl
- 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.
- -updatedb
- 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 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.
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
section:
RANDFILE preserve
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.
- oid_file
- 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.
- oid_section
- 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.
- new_certs_dir
- the same as the -outdir command line option. It
specifies the directory where new certificates will be placed.
Mandatory.
- certificate
- the same as -cert. It gives the file containing the
CA certificate. Mandatory.
- private_key
- same as the -keyfile option. The file containing the
CA private key. Mandatory.
- RANDFILE
- a file used to read and write random number seed
information, or an EGD socket (see RAND_egd(3)).
- default_days
- the same as the -days option. The number of days to
certify a certificate for.
- default_startdate
- the same as the -startdate option. The start date to
certify a certificate for. If not set the current time is used.
- default_enddate
- 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.
- default_md
- the same as the -md option. The message digest to
use. Mandatory.
- database
- the text database file to use. Mandatory. This file must be
present though initially it will be empty.
- unique_subject
- 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.
- serial
- a text file containing the next serial number to use in
hex. Mandatory. This file must be present and contain a valid serial
number.
- crlnumber
- 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.
- x509_extensions
- the same as -extensions.
- crl_extensions
- the same as -crlexts.
- preserve
- the same as -preserveDN
- email_in_dn
- 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.
- msie_hack
- the same as -msie_hack
- policy
- 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.
- copy_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.
POLICY FORMAT
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.
SPKAC FORMAT
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.
EXAMPLES
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):
SPKAC=MIG0MGAwXDANBgkqhkiG9w0BAQEFAANLADBIAkEAn7PDhCeV/xIxUg8V70YRxK2A5
CN=Steve Test
emailAddress=steve@openssl.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
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
FILES
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.
/etc/openssl/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
ENVIRONMENT VARIABLES
OPENSSL_CONF reflects the location of master configuration file it can be
overridden by the
-config command line option.
RESTRICTIONS
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.
BUGS
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 configurable.
Cancelling some commands by refusing to certify a certificate can create an
empty file.
WARNINGS
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 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 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 valid.
SEE ALSO
openssl_req(1),
openssl_spkac(1),
openssl_x509(1),
CA.pl(1),
openssl.cnf(5),
x509v3_config(5)