x509(3)
X509(1) 0.9.6h (2002-11-09) X509(1)
NAME
x509 - Certificate display and signing utility
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]
[-issuer] [-nameopt option] [-email] [-startdate] [-enddate]
[-purpose] [-dates] [-modulus] [-fingerprint] [-alias]
[-noout] [-trustout] [-clrtrust] [-clrreject] [-addtrust
arg] [-addreject arg] [-setalias arg] [-days arg] [-signkey
filename] [-x509toreq] [-req] [-CA filename] [-CAkey
filename] [-CAcreateserial] [-CAserial filename] [-text]
[-C] [-md2|-md5|-sha1|-mdc2] [-clrext] [-extfile filename]
[-extensions section]
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.
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 MD5 is used. If the key being used to sign with is
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a DSA key then this option has no effect: SHA1 is always
used with DSA keys.
DISPLAY OPTIONS
Note: the -alias and -purpose options are also display
options but are described in the TRUST OPTIONS 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.
-noout
this option prevents output of the encoded version of
the request.
-modulus
this option prints out the value of the modulus of the
public key contained in the certificate.
-serial
outputs the certificate serial number.
-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.
-subject
outputs the subject name.
-issuer
outputs the issuer name.
-nameopt option
option which determine how the subject or issuer names
are displayed. This option 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.
-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.
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-dates
prints out the start and expiry dates of a certificate.
-fingerprint
prints out the digest of the DER encoded version of the
whole certificate.
-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.
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-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.
-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
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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.
-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
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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.
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_spc, spc_eq and sname options.
multiline
a multiline format. It is equivalent esc_ctrl, esc_msb,
sep_multiline, spc_eq and lname.
esc_2253
escape the "special" characters required by RFC2253 in a
field That is ,+"<>;. Additionally # is escaped at the
beginnging of a string and a space character at the
beginning or end of a string.
esc_ctrl
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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.
no_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 repesents a single character.
dump_all
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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_multiline
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.
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.
spc_eq
places spaces round the = character which follows the
field name.
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:
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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 -nameopt -escmsb
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 sslclient \
-alias "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-----
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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
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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.
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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.
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SEE ALSO
req(1), ca(1), genrsa(1), gendsa(1), verify(1)
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