NAME
x509 - Certificate display and signing utility
LIBRARY
libcrypto, -lcrypto
SYNOPSIS
openssl x509 [
-inform DER|PEM|NET] [
-outform
DER|PEM|NET] [
-keyform DER|PEM] [
-CAform DER|PEM] [
-CAkeyform DER|PEM] [
-in filename] [
-out filename] [
-serial] [
-hash] [
-subject_hash] [
-issuer_hash]
[
-ocspid] [
-subject] [
-issuer] [
-nameopt
option] [
-email] [
-ocsp_uri] [
-startdate] [
-enddate] [
-purpose] [
-dates] [
-checkend num] [
-modulus] [
-pubkey] [
-fingerprint] [
-alias] [
-noout] [
-trustout] [
-clrtrust] [
-clrreject] [
-addtrust arg] [
-addreject arg] [
-setalias arg] [
-days arg] [
-set_serial n] [
-signkey filename] [
-passin arg] [
-x509toreq] [
-req] [
-CA filename]
[
-CAkey filename] [
-CAcreateserial] [
-CAserial
filename] [
-force_pubkey key] [
-text] [
-certopt
option] [
-C] [
-md2|-md5|-sha1|-mdc2] [
-clrext] [
-extfile filename] [
-extensions section] [
-engine id]
DESCRIPTION
The
x509 command is a multi purpose certificate utility. It can be used
to display certificate information, convert certificates to various forms,
sign certificate requests like a "mini CA" or edit certificate trust
settings.
Since there are a large number of options they will split up into various
sections.
OPTIONS
INPUT, OUTPUT AND GENERAL PURPOSE OPTIONS
- -inform DER|PEM|NET
- This specifies the input format normally the command will
expect an X509 certificate but this can change if other options such as
-req are present. The DER format is the DER encoding of the
certificate and PEM is the base64 encoding of the DER encoding with header
and footer lines added. The NET option is an obscure Netscape server
format that is now obsolete.
- -outform DER|PEM|NET
- This specifies the output format, the options have the same
meaning as the -inform option.
- -in filename
- This specifies the input filename to read a certificate
from or standard input if this option is not specified.
- -out filename
- This specifies the output filename to write to or standard
output by default.
- -md2|-md5|-sha1|-mdc2
- the digest to use. This affects any signing or display
option that uses a message digest, such as the -fingerprint,
-signkey and -CA options. If not specified then SHA1 is
used. If the key being used to sign with is a DSA key then this option has
no effect: SHA1 is always used with DSA keys.
- -engine id
- specifying an engine (by its unique id string) will
cause x509 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.
DISPLAY OPTIONS
Note: the
-alias and
-purpose options are also display options but
are described in the
TRUST SETTINGS section.
- -text
- prints out the certificate in text form. Full details are
output including the public key, signature algorithms, issuer and subject
names, serial number any extensions present and any trust settings.
- -certopt option
- customise the output format used with -text. The
option argument can be a single option or multiple options
separated by commas. The -certopt switch may be also be used more
than once to set multiple options. See the TEXT OPTIONS section for
more information.
- -noout
- this option prevents output of the encoded version of the
request.
- -pubkey
- outputs the the certificate's SubjectPublicKeyInfo block in
PEM format.
- -modulus
- this option prints out the value of the modulus of the
public key contained in the certificate.
- -serial
- outputs the certificate serial number.
- -subject_hash
- outputs the "hash" of the certificate subject
name. This is used in OpenSSL to form an index to allow certificates in a
directory to be looked up by subject name.
- -issuer_hash
- outputs the "hash" of the certificate issuer
name.
- -ocspid
- outputs the OCSP hash values for the subject name and
public key.
- -hash
- synonym for "-subject_hash" for backward
compatibility reasons.
- -subject_hash_old
- outputs the "hash" of the certificate subject
name using the older algorithm as used by OpenSSL versions before
1.0.0.
- -issuer_hash_old
- outputs the "hash" of the certificate issuer name
using the older algorithm as used by OpenSSL versions before 1.0.0.
- -subject
- outputs the subject name.
- -issuer
- outputs the issuer name.
- -nameopt option
- option which determines how the subject or issuer names are
displayed. The option argument can be a single option or multiple
options separated by commas. Alternatively the -nameopt switch may
be used more than once to set multiple options. See the NAME
OPTIONS section for more information.
- -email
- outputs the email address(es) if any.
- -ocsp_uri
- outputs the OCSP responder address(es) if any.
- -startdate
- prints out the start date of the certificate, that is the
notBefore date.
- -enddate
- prints out the expiry date of the certificate, that is the
notAfter date.
- -dates
- prints out the start and expiry dates of a
certificate.
- -checkend arg
- checks if the certificate expires within the next
arg seconds and exits non-zero if yes it will expire or zero if
not.
- -fingerprint
- prints out the digest of the DER encoded version of the
whole certificate (see digest options).
- -C
- this outputs the certificate in the form of a C source
file.
TRUST SETTINGS
Please note these options are currently experimental and may well change.
A
trusted certificate is an ordinary certificate which has several
additional pieces of information attached to it such as the permitted and
prohibited uses of the certificate and an "alias".
Normally when a certificate is being verified at least one certificate must be
"trusted". By default a trusted certificate must be stored locally
and must be a root CA: any certificate chain ending in this CA is then usable
for any purpose.
Trust settings currently are only used with a root CA. They allow a finer
control over the purposes the root CA can be used for. For example a CA may be
trusted for SSL client but not SSL server use.
See the description of the
verify utility for more information on the
meaning of trust settings.
Future versions of OpenSSL will recognize trust settings on any certificate: not
just root CAs.
- -trustout
- this causes x509 to output a trusted
certificate. An ordinary or trusted certificate can be input but by
default an ordinary certificate is output and any trust settings are
discarded. With the -trustout option a trusted certificate is
output. A trusted certificate is automatically output if any trust
settings are modified.
- -setalias arg
- sets the alias of the certificate. This will allow the
certificate to be referred to using a nickname for example "Steve's
Certificate".
- -alias
- outputs the certificate alias, if any.
- -clrtrust
- clears all the permitted or trusted uses of the
certificate.
- -clrreject
- clears all the prohibited or rejected uses of the
certificate.
- -addtrust arg
- adds a trusted certificate use. Any object name can be used
here but currently only clientAuth (SSL client use),
serverAuth (SSL server use) and emailProtection (S/MIME
email) are used. Other OpenSSL applications may define additional
uses.
- -addreject arg
- adds a prohibited use. It accepts the same values as the
-addtrust option.
- -purpose
- this option performs tests on the certificate extensions
and outputs the results. For a more complete description see the
CERTIFICATE EXTENSIONS section.
SIGNING OPTIONS
The
x509 utility can be used to sign certificates and requests: it can
thus behave like a "mini CA".
- -signkey filename
- this option causes the input file to be self signed using
the supplied private key.
If the input file is a certificate it sets the issuer name to the subject
name (i.e. makes it self signed) changes the public key to the supplied
value and changes the start and end dates. The start date is set to the
current time and the end date is set to a value determined by the
-days option. Any certificate extensions are retained unless the
-clrext option is supplied.
If the input is a certificate request then a self signed certificate is
created using the supplied private key using the subject name in the
request.
- -passin arg
- the key password source. For more information about the
format of arg see the PASS PHRASE ARGUMENTS section in
openssl(1).
- -clrext
- delete any extensions from a certificate. This option is
used when a certificate is being created from another certificate (for
example with the -signkey or the -CA options). Normally all
extensions are retained.
- -keyform PEM|DER
- specifies the format (DER or PEM) of the private key file
used in the -signkey option.
- -days arg
- specifies the number of days to make a certificate valid
for. The default is 30 days.
- -x509toreq
- converts a certificate into a certificate request. The
-signkey option is used to pass the required private key.
- -req
- by default a certificate is expected on input. With this
option a certificate request is expected instead.
- -set_serial n
- specifies the serial number to use. This option can be used
with either the -signkey or -CA options. If used in
conjunction with the -CA option the serial number file (as
specified by the -CAserial or -CAcreateserial options) is
not used.
The serial number can be decimal or hex (if preceded by 0x). Negative
serial numbers can also be specified but their use is not
recommended.
- -CA filename
- specifies the CA certificate to be used for signing. When
this option is present x509 behaves like a "mini CA". The
input file is signed by this CA using this option: that is its issuer name
is set to the subject name of the CA and it is digitally signed using the
CAs private key.
This option is normally combined with the -req option. Without the
-req option the input is a certificate which must be self
signed.
- -CAkey filename
- sets the CA private key to sign a certificate with. If this
option is not specified then it is assumed that the CA private key is
present in the CA certificate file.
- -CAserial filename
- sets the CA serial number file to use.
When the -CA option is used to sign a certificate it uses a serial
number specified in a file. This file consist of one line containing an
even number of hex digits with the serial number to use. After each use
the serial number is incremented and written out to the file again.
The default filename consists of the CA certificate file base name with
".srl" appended. For example if the CA certificate file is
called "mycacert.pem" it expects to find a serial number file
called "mycacert.srl".
- -CAcreateserial
- with this option the CA serial number file is created if it
does not exist: it will contain the serial number "02" and the
certificate being signed will have the 1 as its serial number. Normally if
the -CA option is specified and the serial number file does not
exist it is an error.
- -extfile filename
- file containing certificate extensions to use. If not
specified then no extensions are added to the certificate.
- -extensions section
- the section to add certificate extensions from. If this
option is not specified then the extensions should either be contained in
the unnamed (default) section or the default section should contain a
variable called "extensions" which contains the section to use.
See the x509v3_config(5) manual page for details of the extension
section format.
- -force_pubkey key
- when a certificate is created set its public key to
key instead of the key in the certificate or certificate request.
This option is useful for creating certificates where the algorithm can't
normally sign requests, for example DH.
The format or key can be specified using the -keyform
option.
NAME OPTIONS
The
nameopt command line switch determines how the subject and issuer
names are displayed. If no
nameopt switch is present the default
"oneline" format is used which is compatible with previous versions
of OpenSSL. Each option is described in detail below, all options can be
preceded by a
- to turn the option off. Only the first four will
normally be used.
- compat
- use the old format. This is equivalent to specifying no
name options at all.
- RFC2253
- displays names compatible with RFC2253 equivalent to
esc_2253, esc_ctrl, esc_msb, utf8,
dump_nostr, dump_unknown, dump_der,
sep_comma_plus, dn_rev and sname.
- oneline
- a oneline format which is more readable than RFC2253. It is
equivalent to specifying the esc_2253, esc_ctrl,
esc_msb, utf8, dump_nostr, dump_der,
use_quote, sep_comma_plus_space, space_eq and
sname options.
- multiline
- a multiline format. It is equivalent esc_ctrl,
esc_msb, sep_multiline, space_eq, lname and
align.
- esc_2253
- escape the "special" characters required by
RFC2253 in a field That is ,+"<>;. Additionally #
is escaped at the beginning of a string and a space character at the
beginning or end of a string.
- esc_ctrl
- escape control characters. That is those with ASCII values
less than 0x20 (space) and the delete (0x7f) character. They are escaped
using the RFC2253 \XX notation (where XX are two hex digits representing
the character value).
- esc_msb
- escape characters with the MSB set, that is with ASCII
values larger than 127.
- use_quote
- escapes some characters by surrounding the whole string
with " characters, without the option all escaping is done
with the \ character.
- utf8
- convert all strings to UTF8 format first. This is required
by RFC2253. If you are lucky enough to have a UTF8 compatible terminal
then the use of this option (and not setting esc_msb) may
result in the correct display of multibyte (international) characters. Is
this option is not present then multibyte characters larger than 0xff will
be represented using the format \UXXXX for 16 bits and \WXXXXXXXX for 32
bits. Also if this option is off any UTF8Strings will be converted to
their character form first.
- ignore_type
- this option does not attempt to interpret multibyte
characters in any way. That is their content octets are merely dumped as
though one octet represents each character. This is useful for diagnostic
purposes but will result in rather odd looking output.
- show_type
- show the type of the ASN1 character string. The type
precedes the field contents. For example "BMPSTRING: Hello
World".
- dump_der
- when this option is set any fields that need to be
hexdumped will be dumped using the DER encoding of the field. Otherwise
just the content octets will be displayed. Both options use the RFC2253
#XXXX... format.
- dump_nostr
- dump non character string types (for example OCTET STRING)
if this option is not set then non character string types will be
displayed as though each content octet represents a single character.
- dump_all
- dump all fields. This option when used with dump_der
allows the DER encoding of the structure to be unambiguously
determined.
- dump_unknown
- dump any field whose OID is not recognised by OpenSSL.
- sep_comma_plus, sep_comma_plus_space,
sep_semi_plus_space, sep_multiline
- these options determine the field separators. The first
character is between RDNs and the second between multiple AVAs (multiple
AVAs are very rare and their use is discouraged). The options ending in
"space" additionally place a space after the separator to make
it more readable. The sep_multiline uses a linefeed character for
the RDN separator and a spaced + for the AVA separator. It also
indents the fields by four characters. If no field separator is specified
then sep_comma_plus_space is used by default.
- dn_rev
- reverse the fields of the DN. This is required by RFC2253.
As a side effect this also reverses the order of multiple AVAs but this is
permissible.
- nofname, sname, lname, oid
- these options alter how the field name is displayed.
nofname does not display the field at all. sname uses the
"short name" form (CN for commonName for example). lname
uses the long form. oid represents the OID in numerical form and is
useful for diagnostic purpose.
- align
- align field values for a more readable output. Only usable
with sep_multiline.
- space_eq
- places spaces round the = character which follows
the field name.
TEXT OPTIONS
As well as customising the name output format, it is also possible to customise
the actual fields printed using the
certopt options when the
text option is present. The default behaviour is to print all fields.
- compatible
- use the old format. This is equivalent to specifying no
output options at all.
- no_header
- don't print header information: that is the lines saying
"Certificate" and "Data".
- no_version
- don't print out the version number.
- no_serial
- don't print out the serial number.
- no_signame
- don't print out the signature algorithm used.
- no_validity
- don't print the validity, that is the notBefore and
notAfter fields.
- no_subject
- don't print out the subject name.
- no_issuer
- don't print out the issuer name.
- no_pubkey
- don't print out the public key.
- no_sigdump
- don't give a hexadecimal dump of the certificate
signature.
- no_aux
- don't print out certificate trust information.
- no_extensions
- don't print out any X509V3 extensions.
- ext_default
- retain default extension behaviour: attempt to print out
unsupported certificate extensions.
- ext_error
- print an error message for unsupported certificate
extensions.
- ext_parse
- ASN1 parse unsupported extensions.
- ext_dump
- hex dump unsupported extensions.
- ca_default
- the value used by the ca utility, equivalent to
no_issuer, no_pubkey, no_header, and
no_version.
EXAMPLES
Note: in these examples the '\' means the example should be all on one line.
Display the contents of a certificate:
openssl x509 -in cert.pem -noout -text
Display the certificate serial number:
openssl x509 -in cert.pem -noout -serial
Display the certificate subject name:
openssl x509 -in cert.pem -noout -subject
Display the certificate subject name in RFC2253 form:
openssl x509 -in cert.pem -noout -subject -nameopt RFC2253
Display the certificate subject name in oneline form on a terminal supporting
UTF8:
openssl x509 -in cert.pem -noout -subject -nameopt oneline,-esc_msb
Display the certificate MD5 fingerprint:
openssl x509 -in cert.pem -noout -fingerprint
Display the certificate SHA1 fingerprint:
openssl x509 -sha1 -in cert.pem -noout -fingerprint
Convert a certificate from PEM to DER format:
openssl x509 -in cert.pem -inform PEM -out cert.der -outform DER
Convert a certificate to a certificate request:
openssl x509 -x509toreq -in cert.pem -out req.pem -signkey key.pem
Convert a certificate request into a self signed certificate using extensions
for a CA:
openssl x509 -req -in careq.pem -extfile openssl.cnf -extensions v3_ca \
-signkey key.pem -out cacert.pem
Sign a certificate request using the CA certificate above and add user
certificate extensions:
openssl x509 -req -in req.pem -extfile openssl.cnf -extensions v3_usr \
-CA cacert.pem -CAkey key.pem -CAcreateserial
Set a certificate to be trusted for SSL client use and change set its alias to
"Steve's Class 1 CA"
openssl x509 -in cert.pem -addtrust clientAuth \
-setalias "Steve's Class 1 CA" -out trust.pem
NOTES
The PEM format uses the header and footer lines:
-----BEGIN CERTIFICATE-----
-----END CERTIFICATE-----
it will also handle files containing:
-----BEGIN X509 CERTIFICATE-----
-----END X509 CERTIFICATE-----
Trusted certificates have the lines
-----BEGIN TRUSTED CERTIFICATE-----
-----END TRUSTED CERTIFICATE-----
The conversion to UTF8 format used with the name options assumes that T61Strings
use the ISO8859-1 character set. This is wrong but Netscape and MSIE do this
as do many certificates. So although this is incorrect it is more likely to
display the majority of certificates correctly.
The
-fingerprint option takes the digest of the DER encoded certificate.
This is commonly called a "fingerprint". Because of the nature of
message digests the fingerprint of a certificate is unique to that certificate
and two certificates with the same fingerprint can be considered to be the
same.
The Netscape fingerprint uses MD5 whereas MSIE uses SHA1.
The
-email option searches the subject name and the subject alternative
name extension. Only unique email addresses will be printed out: it will not
print the same address more than once.
CERTIFICATE EXTENSIONS
The
-purpose option checks the certificate extensions and determines what
the certificate can be used for. The actual checks done are rather complex and
include various hacks and workarounds to handle broken certificates and
software.
The same code is used when verifying untrusted certificates in chains so this
section is useful if a chain is rejected by the verify code.
The basicConstraints extension CA flag is used to determine whether the
certificate can be used as a CA. If the CA flag is true then it is a CA, if
the CA flag is false then it is not a CA.
All CAs should have the CA
flag set to true.
If the basicConstraints extension is absent then the certificate is considered
to be a "possible CA" other extensions are checked according to the
intended use of the certificate. A warning is given in this case because the
certificate should really not be regarded as a CA: however it is allowed to be
a CA to work around some broken software.
If the certificate is a V1 certificate (and thus has no extensions) and it is
self signed it is also assumed to be a CA but a warning is again given: this
is to work around the problem of Verisign roots which are V1 self signed
certificates.
If the keyUsage extension is present then additional restraints are made on the
uses of the certificate. A CA certificate
must have the keyCertSign bit
set if the keyUsage extension is present.
The extended key usage extension places additional restrictions on the
certificate uses. If this extension is present (whether critical or not) the
key can only be used for the purposes specified.
A complete description of each test is given below. The comments about
basicConstraints and keyUsage and V1 certificates above apply to
all CA
certificates.
- SSL Client
- The extended key usage extension must be absent or include
the "web client authentication" OID. keyUsage must be absent or
it must have the digitalSignature bit set. Netscape certificate type must
be absent or it must have the SSL client bit set.
- SSL Client CA
- The extended key usage extension must be absent or include
the "web client authentication" OID. Netscape certificate type
must be absent or it must have the SSL CA bit set: this is used as a work
around if the basicConstraints extension is absent.
- SSL Server
- The extended key usage extension must be absent or include
the "web server authentication" and/or one of the SGC OIDs.
keyUsage must be absent or it must have the digitalSignature, the
keyEncipherment set or both bits set. Netscape certificate type must be
absent or have the SSL server bit set.
- SSL Server CA
- The extended key usage extension must be absent or include
the "web server authentication" and/or one of the SGC OIDs.
Netscape certificate type must be absent or the SSL CA bit must be set:
this is used as a work around if the basicConstraints extension is
absent.
- Netscape SSL Server
- For Netscape SSL clients to connect to an SSL server it
must have the keyEncipherment bit set if the keyUsage extension is
present. This isn't always valid because some cipher suites use the key
for digital signing. Otherwise it is the same as a normal SSL server.
- Common S/MIME Client Tests
- The extended key usage extension must be absent or include
the "email protection" OID. Netscape certificate type must be
absent or should have the S/MIME bit set. If the S/MIME bit is not set in
netscape certificate type then the SSL client bit is tolerated as an
alternative but a warning is shown: this is because some Verisign
certificates don't set the S/MIME bit.
- S/MIME Signing
- In addition to the common S/MIME client tests the
digitalSignature bit must be set if the keyUsage extension is
present.
- S/MIME Encryption
- In addition to the common S/MIME tests the keyEncipherment
bit must be set if the keyUsage extension is present.
- S/MIME CA
- The extended key usage extension must be absent or include
the "email protection" OID. Netscape certificate type must be
absent or must have the S/MIME CA bit set: this is used as a work around
if the basicConstraints extension is absent.
- CRL Signing
- The keyUsage extension must be absent or it must have the
CRL signing bit set.
- CRL Signing CA
- The normal CA tests apply. Except in this case the
basicConstraints extension must be present.
BUGS
Extensions in certificates are not transferred to certificate requests and vice
versa.
It is possible to produce invalid certificates or requests by specifying the
wrong private key or using inconsistent options in some cases: these should be
checked.
There should be options to explicitly set such things as start and end dates
rather than an offset from the current time.
The code to implement the verify behaviour described in the
TRUST
SETTINGS is currently being developed. It thus describes the intended
behaviour rather than the current behaviour. It is hoped that it will
represent reality in OpenSSL 0.9.5 and later.
SEE ALSO
openssl_req(1),
openssl_ca(1),
openssl_genrsa(1),
openssl_gendsa(1),
openssl_verify(1),
x509v3_config(5)
HISTORY
Before OpenSSL 0.9.8, the default digest for RSA keys was MD5.
The hash algorithm used in the
-subject_hash and
-issuer_hash
options before OpenSSL 1.0.0 was based on the deprecated MD5 algorithm and the
encoding of the distinguished name. In OpenSSL 1.0.0 and later it is based on
a canonical version of the DN using SHA1. This means that any directories
using the old form must have their links rebuilt using
c_rehash or
similar.