x509 - Certificate display and signing utility
[-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] [-subject] [-issuer] [-nameopt option] [-email] [-startdate] [-enddate] [-purpose] [-dates] [-modulus] [-fingerprint] [-alias] [-noout] [-trustout] [-clrtrust] [-clrreject] [-addtrust arg] [-addreject arg] [-setalias arg] [-days arg] [-set_serial n] [-signkey filename] [-x509toreq] [-req] [-CA filename] [-CAkey filename] [-CAcreateserial] [-CAserial filename] [-text] [-C] [-md2|-md5|-sha1|-mdc2] [-clrext] [-extfile filename] [-extensions section] [-engine id]
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
- -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
- -outform DER|PEM|NET
This specifies the output format, the options have the same meaning as the
- -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
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
- -engine id
specifying an engine (by it's unique id string) will cause req
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.
Note: the -alias and -purpose options are also display options but are described in the TRUST SETTINGS section.
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.
this option prevents output of the encoded version of the request.
this option prints out the value of the modulus of the public key contained
in the certificate.
outputs the certificate serial number.
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.
outputs the ``hash'' of the certificate issuer name.
synonym for ``-hash'' for backward compatibility reasons.
outputs the subject name.
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.
outputs the email
address(es) if any.
prints out the start date of the certificate, that is the notBefore date.
prints out the expiry date of the certificate, that is the notAfter date.
prints out the start and expiry dates of a certificate.
prints out the digest of the DER encoded version of the whole certificate
(see digest options).
this outputs the certificate in the form of a C source file.
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.
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.
-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''.
outputs the certificate alias, if any.
clears all the permitted or trusted uses of the certificate.
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
- -addreject arg
adds a prohibited use. It accepts the same values as the -addtrust
this option performs tests on the certificate extensions and outputs the
results. For a more complete description see the CERTIFICATE
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
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
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
- -days arg
specifies the number of days to make a certificate valid for. The default
is 30 days.
converts a certificate into a certificate request. The -signkey option is used to pass the required private key.
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
- -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
- -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
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
- -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.
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.
use the old format. This is equivalent to specifying no name options at
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.
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
a multiline format. It is equivalent esc_ctrl, esc_msb, sep_multiline,
space_eq, lname and align.
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.
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
escape characters with the MSB set, that is with ASCII values larger than
escapes some characters by surrounding the whole string with " characters, without the option all escaping is done with the \ character.
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.
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 the type of the ASN1 character string. The type precedes the field
contents. For example ``BMPSTRING: Hello World''.
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
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 fields. This option when used with dump_der allows the DER encoding of the structure to be unambiguously determined.
dump any field whose OID is not recognised by OpenSSL.
- sep_comma_plus, sep_comma_plus_space, sep_semi_plus_space,
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.
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 field values for a more readable output. Only usable with
places spaces round the = character which follows the field name.
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.
use the old format. This is equivalent to specifying no output options at
don't print header information: that is the lines saying ``Certificate''
don't print out the version number.
don't print out the serial number.
don't print out the signature algorithm used.
don't print the validity, that is the notBefore and notAfter fields.
don't print out the subject name.
don't print out the issuer name.
don't print out the public key.
don't give a hexadecimal dump of the certificate signature.
don't print out certificate trust information.
don't print out any X509V3 extensions.
retain default extension behaviour: attempt to print out unsupported
print an error message for unsupported certificate extensions.
ASN1 parse unsupported extensions.
hex dump unsupported extensions.
the value used by the ca utility, equivalent to no_issuer, no_pubkey, no_header,
no_version, no_sigdump and no_signame.
Note: in these examples the '\' means the example should be all on one
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
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
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
The PEM format uses the header and footer lines:
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.
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
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
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
- 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
- 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
- CRL Signing CA
The normal CA tests apply. Except in this case the basicConstraints
extension must be present.
Extensions in certificates are not transferred to certificate requests and
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.
req(1), ca(1), genrsa(1),
Before OpenSSL 0.9.8, the default digest for RSA keys was MD5.