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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] [-fin-
gerprint] [-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 sec-
tion] [-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 vari-
ous 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 MD5 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 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.
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.
-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 determines how the subject or issuer names are dis-
played. 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.
-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.
-fingerprint
prints out the digest of the DER encoded version of the whole cer-
tificate (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 exam-
ple 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 cer-
tificate: 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 cer-
tificate is output and any trust settings are discarded. With the
-trustout option a trusted certificate is output. A trusted cer-
tificate is automatically output if any trust settings are modi-
fied.
-setalias arg
sets the alias of the certificate. This will allow the certificate
to be referred to using a nickname for example "Steve's Certifi-
cate".
-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 out-
puts the results. For a more complete description see the CERTIFI-
CATE 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 sup-
plied 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 certifi-
cate 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 exam-
ple 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). Nega-
tive serial numbers can also be specified but their use is not rec-
ommended.
-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 contain-
ing 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 certifi-
cate 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.
NAME OPTIONS
The nameopt command line switch determines how the subject and issuer
names are displayed. If no nameopt switch is present the default "one-
line" 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 nor-
mally 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 equiva-
lent 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_multi-
line, spc_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 repre-
senting 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 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_multi-
line
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 repre-
sents the OID in numerical form and is useful for diagnostic pur-
pose.
align
align field values for a more readable output. Only usable with
sep_multiline.
spc_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 "Certifi-
cate" 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 unsup-
ported 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_pub-
key, no_header, no_version, no_sigdump and no_signame.
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 sup-
porting UTF8:
openssl x509 -in cert.pem -noout -subject -nameopt oneline,-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 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 certifi-
cate. 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 con-
sidered 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 cer-
tificates 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 cer-
tificate 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 sign-
ing 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 specify-
ing 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 SET-
TINGS 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
req(1),ca(1),genrsa(1),gendsa(1),verify(1)
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