CSE2410 Fall 2014 Bounce

=pod

=head1 NAME

x509 - Certificate display and signing utility

=head1 SYNOPSIS

B<openssl> B<x509>

[B<-inform DER|PEM|NET>]

[B<-outform DER|PEM|NET>]

[B<-keyform DER|PEM>]

[B<-CAform DER|PEM>]

[B<-CAkeyform DER|PEM>]

[B<-in filename>]

[B<-out filename>]

[B<-serial>]

[B<-hash>]

[B<-subject_hash>]

[B<-issuer_hash>]

[B<-ocspid>]

[B<-subject>]

[B<-issuer>]

[B<-nameopt option>]

[B<-email>]

[B<-ocsp_uri>]

[B<-startdate>]

[B<-enddate>]

[B<-purpose>]

[B<-dates>]

[B<-checkend num>]

[B<-modulus>]

[B<-pubkey>]

[B<-fingerprint>]

[B<-alias>]

[B<-noout>]

[B<-trustout>]

[B<-clrtrust>]

[B<-clrreject>]

[B<-addtrust arg>]

[B<-addreject arg>]

[B<-setalias arg>]

[B<-days arg>]

[B<-set_serial n>]

[B<-signkey filename>]

[B<-passin arg>]

[B<-x509toreq>]

[B<-req>]

[B<-CA filename>]

[B<-CAkey filename>]

[B<-CAcreateserial>]

[B<-CAserial filename>]

[B<-text>]

[B<-certopt option>]

[B<-C>]

[B<-md2|-md5|-sha1|-mdc2>]

[B<-clrext>]

[B<-extfile filename>]

[B<-extensions section>]

[B<-engine id>]

=head1 DESCRIPTION

The B<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.

=head1 OPTIONS

=head2 INPUT, OUTPUT AND GENERAL PURPOSE OPTIONS

=over 4

=item B<-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 B<-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.

=item B<-outform DER|PEM|NET>

This specifies the output format, the options have the same meaning as the 

B<-inform> option.

=item B<-in filename>

This specifies the input filename to read a certificate from or standard input

if this option is not specified.

=item B<-out filename>

This specifies the output filename to write to or standard output by

default.

=item B<-md2|-md5|-sha1|-mdc2>

the digest to use. This affects any signing or display option that uses a message

digest, such as the B<-fingerprint>, B<-signkey> and B<-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.

=item B<-engine id>

specifying an engine (by its unique B<id> string) will cause B<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.

=back

=head2 DISPLAY OPTIONS

Note: the B<-alias> and B<-purpose> options are also display options

but are described in the B<TRUST SETTINGS> section.

=over 4

=item B<-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.

=item B<-certopt option>

customise the output format used with B<-text>. The B<option> argument can be

a single option or multiple options separated by commas. The B<-certopt> switch

may be also be used more than once to set multiple options. See the B<TEXT OPTIONS>

section for more information.

=item B<-noout>

this option prevents output of the encoded version of the request.

=item B<-pubkey>

outputs the the certificate's SubjectPublicKeyInfo block in PEM format.

=item B<-modulus>

this option prints out the value of the modulus of the public key

contained in the certificate.

=item B<-serial>

outputs the certificate serial number.

=item B<-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.

=item B<-issuer_hash>

outputs the "hash" of the certificate issuer name.

=item B<-ocspid>

outputs the OCSP hash values for the subject name and public key.

=item B<-hash>

synonym for "-subject_hash" for backward compatibility reasons.

=item B<-subject_hash_old>

outputs the "hash" of the certificate subject name using the older algorithm

as used by OpenSSL versions before 1.0.0.

=item B<-issuer_hash_old>

outputs the "hash" of the certificate issuer name using the older algorithm

as used by OpenSSL versions before 1.0.0.

=item B<-subject>

outputs the subject name.

=item B<-issuer>

outputs the issuer name.

=item B<-nameopt option>

option which determines how the subject or issuer names are displayed. The

B<option> argument can be a single option or multiple options separated by

commas.  Alternatively the B<-nameopt> switch may be used more than once to

set multiple options. See the B<NAME OPTIONS> section for more information.

=item B<-email>

outputs the email address(es) if any.

=item B<-ocsp_uri>

outputs the OCSP responder address(es) if any.

=item B<-startdate>

prints out the start date of the certificate, that is the notBefore date.

=item B<-enddate>

prints out the expiry date of the certificate, that is the notAfter date.

=item B<-dates>

prints out the start and expiry dates of a certificate.

=item B<-checkend arg>

checks if the certificate expires within the next B<arg> seconds and exits

non-zero if yes it will expire or zero if not.

=item B<-fingerprint>

prints out the digest of the DER encoded version of the whole certificate

(see digest options).

=item B<-C>

this outputs the certificate in the form of a C source file.

=back

=head2 TRUST SETTINGS

Please note these options are currently experimental and may well change.

A B<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 B<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.

=over 4

=item B<-trustout>

this causes B<x509> to output a B<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

B<-trustout> option a trusted certificate is output. A trusted

certificate is automatically output if any trust settings are modified.

=item B<-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".

=item B<-alias>

outputs the certificate alias, if any.

=item B<-clrtrust>

clears all the permitted or trusted uses of the certificate.

=item B<-clrreject>

clears all the prohibited or rejected uses of the certificate.

=item B<-addtrust arg>

adds a trusted certificate use. Any object name can be used here

but currently only B<clientAuth> (SSL client use), B<serverAuth>

(SSL server use) and B<emailProtection> (S/MIME email) are used.

Other OpenSSL applications may define additional uses.

=item B<-addreject arg>

adds a prohibited use. It accepts the same values as the B<-addtrust>

option.

=item B<-purpose>

this option performs tests on the certificate extensions and outputs

the results. For a more complete description see the B<CERTIFICATE

EXTENSIONS> section.

=back

=head2 SIGNING OPTIONS

The B<x509> utility can be used to sign certificates and requests: it

can thus behave like a "mini CA".

=over 4

=item B<-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 B<-days> option. Any certificate extensions are retained unless

the B<-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.

=item B<-passin arg>

the key password source. For more information about the format of B<arg>

see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.

=item B<-clrext>

delete any extensions from a certificate. This option is used when a

certificate is being created from another certificate (for example with

the B<-signkey> or the B<-CA> options). Normally all extensions are

retained.

=item B<-keyform PEM|DER>

specifies the format (DER or PEM) of the private key file used in the

B<-signkey> option.

=item B<-days arg>

specifies the number of days to make a certificate valid for. The default

is 30 days.

=item B<-x509toreq>

converts a certificate into a certificate request. The B<-signkey> option

is used to pass the required private key.

=item B<-req>

by default a certificate is expected on input. With this option a

certificate request is expected instead.

=item B<-set_serial n>

specifies the serial number to use. This option can be used with either

the B<-signkey> or B<-CA> options. If used in conjunction with the B<-CA>

option the serial number file (as specified by the B<-CAserial> or

B<-CAcreateserial> options) is not used.

The serial number can be decimal or hex (if preceded by B<0x>). Negative

serial numbers can also be specified but their use is not recommended.

=item B<-CA filename>

specifies the CA certificate to be used for signing. When this option is

present B<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 B<-req> option. Without the

B<-req> option the input is a certificate which must be self signed.

=item B<-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.

=item B<-CAserial filename>

sets the CA serial number file to use.

When the B<-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".

=item B<-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 B<-CA> option is specified

and the serial number file does not exist it is an error.

=item B<-extfile filename>

file containing certificate extensions to use. If not specified then

no extensions are added to the certificate.

=item B<-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

L<x509v3_config(5)|x509v3_config(5)> manual page for details of the

extension section format.

=back

=head2 NAME OPTIONS

The B<nameopt> command line switch determines how the subject and issuer

names are displayed. If no B<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 B<-> to turn the option off. Only the first four will normally be used.

=over 4

=item B<compat>

use the old format. This is equivalent to specifying no name options at all.

=item B<RFC2253>

displays names compatible with RFC2253 equivalent to B<esc_2253>, B<esc_ctrl>,

B<esc_msb>, B<utf8>, B<dump_nostr>, B<dump_unknown>, B<dump_der>,

B<sep_comma_plus>, B<dn_rev> and B<sname>.

=item B<oneline>

a oneline format which is more readable than RFC2253. It is equivalent to

specifying the  B<esc_2253>, B<esc_ctrl>, B<esc_msb>, B<utf8>, B<dump_nostr>,

B<dump_der>, B<use_quote>, B<sep_comma_plus_space>, B<space_eq> and B<sname>

options.

=item B<multiline>

a multiline format. It is equivalent B<esc_ctrl>, B<esc_msb>, B<sep_multiline>,

B<space_eq>, B<lname> and B<align>.

=item B<esc_2253>

escape the "special" characters required by RFC2253 in a field That is

B<,+"E<lt>E<gt>;>. Additionally B<#> is escaped at the beginning of a string

and a space character at the beginning or end of a string.

=item B<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).

=item B<esc_msb>

escape characters with the MSB set, that is with ASCII values larger than

127.

=item B<use_quote>

escapes some characters by surrounding the whole string with B<"> characters,

without the option all escaping is done with the B<\> character.

=item B<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 B<not> setting B<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.

=item B<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.

=item B<show_type>

show the type of the ASN1 character string. The type precedes the

field contents. For example "BMPSTRING: Hello World".

=item B<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

B<#XXXX...> format.

=item B<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.

=item B<dump_all>

dump all fields. This option when used with B<dump_der> allows the

DER encoding of the structure to be unambiguously determined.

=item B<dump_unknown>

dump any field whose OID is not recognised by OpenSSL.

=item B<sep_comma_plus>, B<sep_comma_plus_space>, B<sep_semi_plus_space>,

B<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 B<sep_multiline> uses a linefeed character for

the RDN separator and a spaced B<+> for the AVA separator. It also

indents the fields by four characters.

=item B<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.

=item B<nofname>, B<sname>, B<lname>, B<oid>

these options alter how the field name is displayed. B<nofname> does

not display the field at all. B<sname> uses the "short name" form

(CN for commonName for example). B<lname> uses the long form.

B<oid> represents the OID in numerical form and is useful for

diagnostic purpose.

=item B<align>

align field values for a more readable output. Only usable with

B<sep_multiline>.

=item B<space_eq>

places spaces round the B<=> character which follows the field

name.

=back

=head2 TEXT OPTIONS

As well as customising the name output format, it is also possible to

customise the actual fields printed using the B<certopt> options when

the B<text> option is present. The default behaviour is to print all fields.

=over 4

=item B<compatible>

use the old format. This is equivalent to specifying no output options at all.

=item B<no_header>

don't print header information: that is the lines saying "Certificate" and "Data".

=item B<no_version>

don't print out the version number.

=item B<no_serial>

don't print out the serial number.

=item B<no_signame>

don't print out the signature algorithm used.

=item B<no_validity>

don't print the validity, that is the B<notBefore> and B<notAfter> fields.

=item B<no_subject>

don't print out the subject name.

=item B<no_issuer>

don't print out the issuer name.

=item B<no_pubkey>

don't print out the public key.

=item B<no_sigdump>

don't give a hexadecimal dump of the certificate signature.

=item B<no_aux>

don't print out certificate trust information.

=item B<no_extensions>

don't print out any X509V3 extensions.

=item B<ext_default>

retain default extension behaviour: attempt to print out unsupported certificate extensions.

=item B<ext_error>

print an error message for unsupported certificate extensions.

=item B<ext_parse>

ASN1 parse unsupported extensions.

=item B<ext_dump>

hex dump unsupported extensions.

=item B<ca_default>

the value used by the B<ca> utility, equivalent to B<no_issuer>, B<no_pubkey>, B<no_header>,

B<no_version>, B<no_sigdump> and B<no_signame>.

=back

=head1 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

=head1 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 B<-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 B<-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.

=head1 CERTIFICATE EXTENSIONS

The B<-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. B<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 B<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 B<all>

CA certificates.

=over 4

=item B<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.

=item B<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.

=item B<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.

=item B<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.

=item B<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.

=item B<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.

=item B<S/MIME Signing>

In addition to the common S/MIME client tests the digitalSignature bit must

be set if the keyUsage extension is present.

=item B<S/MIME Encryption>

In addition to the common S/MIME tests the keyEncipherment bit must be set

if the keyUsage extension is present.

=item B<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. 

=item B<CRL Signing>

The keyUsage extension must be absent or it must have the CRL signing bit

set.

=item B<CRL Signing CA>

The normal CA tests apply. Except in this case the basicConstraints extension

must be present.

=back

=head1 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 B<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.

=head1 SEE ALSO

L<req(1)|req(1)>, L<ca(1)|ca(1)>, L<genrsa(1)|genrsa(1)>,

L<gendsa(1)|gendsa(1)>, L<verify(1)|verify(1)>,

L<x509v3_config(5)|x509v3_config(5)> 

=head1 HISTORY

Before OpenSSL 0.9.8, the default digest for RSA keys was MD5.

The hash algorithm used in the B<-subject_hash> and B<-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 B<c_rehash> or similar. 

=cut