MAN page from Trustix openssl-0.9.7m-1tr.i586.rpm


Section: OpenSSL (1)
Updated: 2007-02-03


x509 - Certificate display and signing utility 


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][-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 beused to display certificate information, convert certificates tovarious forms, sign certificate requests like a ``mini CA'' or editcertificate trust settings.

Since there are a large number of options they will split up intovarious sections. 




-inform DER|PEM|NET
This specifies the input format normally the command will expect an X509certificate but this can change if other options such as -req arepresent. The DER format is the DER encoding of the certificate and PEMis the base64 encoding of the DER encoding with header and footer linesadded. The NET option is an obscure Netscape server format that is nowobsolete.
-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 inputif this option is not specified.
-out filename
This specifies the output filename to write to or standard output bydefault.
the digest to use. This affects any signing or display option that uses a messagedigest, such as the -fingerprint, -signkey and -CA options. If notspecified then MD5 is used. If the key being used to sign with is a DSA key thenthis option has no effect: SHA1 is always used with DSA keys.
-engine id
specifying an engine (by it's unique id string) will cause reqto attempt to obtain a functional reference to the specified engine,thus initialising it if needed. The engine will then be set as the defaultfor all available algorithms.


Note: the -alias and -purpose options are also display optionsbut are described in the TRUST SETTINGS section.
prints out the certificate in text form. Full details are output including thepublic key, signature algorithms, issuer and subject names, serial numberany extensions present and any trust settings.
-certopt option
customise the output format used with -text. The option argument can bea single option or multiple options separated by commas. The -certopt switchmay be also be used more than once to set multiple options. See the TEXT OPTIONSsection 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 keycontained in the certificate.
outputs the certificate serial number.
outputs the ``hash'' of the certificate subject name. This is used in OpenSSL toform an index to allow certificates in a directory to be looked up by subjectname.
outputs the subject name.
outputs the issuer name.
-nameopt option
option which determines how the subject or issuer names are displayed. Theoption argument can be a single option or multiple options separated bycommas. Alternatively the -nameopt switch may be used more than once toset 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 severaladditional pieces of information attached to it such as the permittedand prohibited uses of the certificate and an ``alias''.

Normally when a certificate is being verified at least one certificatemust be ``trusted''. By default a trusted certificate must be storedlocally and must be a root CA: any certificate chain ending in this CAis then usable for any purpose.

Trust settings currently are only used with a root CA. They allow a finercontrol over the purposes the root CA can be used for. For example a CAmay be trusted for SSL client but not SSL server use.

See the description of the verify utility for more information on themeaning of trust settings.

Future versions of OpenSSL will recognize trust settings on anycertificate: not just root CAs.

this causes x509 to output a trusted certificate. An ordinaryor trusted certificate can be input but by default an ordinarycertificate is output and any trust settings are discarded. With the-trustout option a trusted certificate is output. A trustedcertificate is automatically output if any trust settings are modified.
-setalias arg
sets the alias of the certificate. This will allow the certificateto 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 herebut 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 -addtrustoption.
this option performs tests on the certificate extensions and outputsthe results. For a more complete description see the CERTIFICATEEXTENSIONS section.


The x509 utility can be used to sign certificates and requests: itcan thus behave like a ``mini CA''.
-signkey filename
this option causes the input file to be self signed using the suppliedprivate key.

If the input file is a certificate it sets the issuer name to thesubject name (i.e. makes it self signed) changes the public key to thesupplied value and changes the start and end dates. The start date isset to the current time and the end date is set to a value determinedby the -days option. Any certificate extensions are retained unlessthe -clrext option is supplied.

If the input is a certificate request then a self signed certificateis created using the supplied private key using the subject name inthe request.

delete any extensions from a certificate. This option is used when acertificate is being created from another certificate (for example withthe -signkey or the -CA options). Normally all extensions areretained.
-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 defaultis 30 days.
converts a certificate into a certificate request. The -signkey optionis used to pass the required private key.
by default a certificate is expected on input. With this option acertificate request is expected instead.
-set_serial n
specifies the serial number to use. This option can be used with eitherthe -signkey or -CA options. If used in conjunction with the -CAoption 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). Negativeserial 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 ispresent x509 behaves like a ``mini CA''. The input file is signed by thisCA using this option: that is its issuer name is set to the subject nameof 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 isnot specified then it is assumed that the CA private key is present inthe 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 serialnumber specified in a file. This file consist of one line containingan even number of hex digits with the serial number to use. After eachuse 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 willhave the 1 as its serial number. Normally if the -CA option is specifiedand the serial number file does not exist it is an error.
-extfile filename
file containing certificate extensions to use. If not specified thenno extensions are added to the certificate.
-extensions section
the section to add certificate extensions from. If this option is notspecified 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.


The nameopt command line switch determines how the subject and issuernames 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 bya - 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 all.
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 tospecifying the esc_2253, esc_ctrl, esc_msb, utf8, dump_nostr,dump_der, use_quote, sep_comma_plus_space, space_eq and snameoptions.
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 stringand a space character at the beginning or end of a string.
escape control characters. That is those with ASCII values less than0x20 (space) and the delete (0x7f) character. They are escaped using theRFC2253 \XX notation (where XX are two hex digits representing thecharacter value).
escape characters with the MSB set, that is with ASCII values larger than127.
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. Ifyou are lucky enough to have a UTF8 compatible terminal then the useof this option (and not setting esc_msb) may result in the correctdisplay of multibyte (international) characters. Is this option is notpresent then multibyte characters larger than 0xff will be representedusing the format \UXXXX for 16 bits and \WXXXXXXXX for 32 bits.Also if this option is off any UTF8Strings will be converted to theircharacter form first.
this option does not attempt to interpret multibyte characters in anyway. That is their content octets are merely dumped as though one octetrepresents each character. This is useful for diagnostic purposes butwill result in rather odd looking output.
show the type of the ASN1 character string. The type precedes thefield contents. For example ``BMPSTRING: Hello World''.
when this option is set any fields that need to be hexdumped willbe dumped using the DER encoding of the field. Otherwise just thecontent octets will be displayed. Both options use the RFC2253#XXXX... format.
dump non character string types (for example OCTET STRING) if thisoption is not set then non character string types will be displayedas though each content octet represents a single character.
dump all fields. This option when used with dump_der allows theDER 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, sep_multiline
these options determine the field separators. The first character isbetween RDNs and the second between multiple AVAs (multiple AVAs arevery rare and their use is discouraged). The options ending in``space'' additionally place a space after the separator to make itmore readable. The sep_multiline uses a linefeed character forthe RDN separator and a spaced + for the AVA separator. It alsoindents the fields by four characters.
reverse the fields of the DN. This is required by RFC2253. As a sideeffect this also reverses the order of multiple AVAs but this ispermissible.
nofname, sname, lname, oid
these options alter how the field name is displayed. nofname doesnot 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 fordiagnostic purpose.
align field values for a more readable output. Only usable withsep_multiline.
places spaces round the = character which follows the fieldname.


As well as customising the name output format, it is also possible tocustomise the actual fields printed using the certopt options whenthe 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 all.
don't print header information: that is the lines saying ``Certificate'' and ``Data''.
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 certificate extensions.
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 oneline.

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 terminalsupporting 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 usingextensions 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 usercertificate 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


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


The conversion to UTF8 format used with the name options assumes thatT61Strings use the ISO8859-1 character set. This is wrong but Netscapeand MSIE do this as do many certificates. So although this is incorrectit 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 messagedigests the fingerprint of a certificate is unique to that certificate andtwo 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 alternativename extension. Only unique email addresses will be printed out: it willnot print the same address more than once. 


The -purpose option checks the certificate extensions and determineswhat the certificate can be used for. The actual checks done are rathercomplex and include various hacks and workarounds to handle brokencertificates and software.

The same code is used when verifying untrusted certificates in chainsso this section is useful if a chain is rejected by the verify code.

The basicConstraints extension CA flag is used to determine whether thecertificate 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 theCA flag set to true.

If the basicConstraints extension is absent then the certificate isconsidered to be a ``possible CA'' other extensions are checked accordingto the intended use of the certificate. A warning is given in this casebecause the certificate should really not be regarded as a CA: howeverit is allowed to be a CA to work around some broken software.

If the certificate is a V1 certificate (and thus has no extensions) andit is self signed it is also assumed to be a CA but a warning is againgiven: this is to work around the problem of Verisign roots which are V1self signed certificates.

If the keyUsage extension is present then additional restraints aremade on the uses of the certificate. A CA certificate must have thekeyCertSign bit set if the keyUsage extension is present.

The extended key usage extension places additional restrictions on thecertificate 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 aboutbasicConstraints and keyUsage and V1 certificates above apply to allCA certificates.

SSL Client
The extended key usage extension must be absent or include the ``web clientauthentication'' OID. keyUsage must be absent or it must have thedigitalSignature bit set. Netscape certificate type must be absent or it musthave the SSL client bit set.
SSL Client CA
The extended key usage extension must be absent or include the ``web clientauthentication'' OID. Netscape certificate type must be absent or it must havethe SSL CA bit set: this is used as a work around if the basicConstraintsextension is absent.
SSL Server
The extended key usage extension must be absent or include the ``web serverauthentication'' and/or one of the SGC OIDs. keyUsage must be absent or itmust 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 serverauthentication'' and/or one of the SGC OIDs. Netscape certificate type mustbe absent or the SSL CA bit must be set: this is used as a work around if thebasicConstraints extension is absent.
Netscape SSL Server
For Netscape SSL clients to connect to an SSL server it must have thekeyEncipherment bit set if the keyUsage extension is present. This isn'talways 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 ``emailprotection'' OID. Netscape certificate type must be absent or should have theS/MIME bit set. If the S/MIME bit is not set in netscape certificate typethen 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 mustbe set if the keyUsage extension is present.
S/MIME Encryption
In addition to the common S/MIME tests the keyEncipherment bit must be setif the keyUsage extension is present.
The extended key usage extension must be absent or include the ``emailprotection'' OID. Netscape certificate type must be absent or must have theS/MIME CA bit set: this is used as a work around if the basicConstraintsextension is absent.
CRL Signing
The keyUsage extension must be absent or it must have the CRL signing bitset.
CRL Signing CA
The normal CA tests apply. Except in this case the basicConstraints extensionmust be present.


Extensions in certificates are not transferred to certificate requests andvice versa.

It is possible to produce invalid certificates or requests by specifying thewrong private key or using inconsistent options in some cases: these shouldbe checked.

There should be options to explicitly set such things as start and enddates rather than an offset from the current time.

The code to implement the verify behaviour described in the TRUST SETTINGSis currently being developed. It thus describes the intended behaviour ratherthan the current behaviour. It is hoped that it will represent reality inOpenSSL 0.9.5 and later. 


req(1), ca(1), genrsa(1),gendsa(1), verify(1)




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