=pod

=head1 NAME

ciphers - SSL cipher display and cipher list tool.

=head1 SYNOPSIS

B<openssl> B<ciphers>
[B<-v>]
[B<-ssl2>]
[B<-ssl3>]
[B<-tls1>]
[B<cipherlist>]

=head1 DESCRIPTION

The B<cipherlist> command converts OpenSSL cipher lists into ordered
SSL cipher preference lists. It can be used as a test tool to determine
the appropriate cipherlist.

=head1 COMMAND OPTIONS

=over 4

=item B<-v>

verbose option. List ciphers with a complete description of
protocol version (SSLv2 or SSLv3; the latter includes TLS), key exchange,
authentication, encryption and mac algorithms used along with any key size
restrictions and whether the algorithm is classed as an "export" cipher.
Note that without the B<-v> option, ciphers may seem to appear twice
in a cipher list; this is when similar ciphers are available for
SSL v2 and for SSL v3/TLS v1.

=item B<-ssl3>

only include SSL v3 ciphers.

=item B<-ssl2>

only include SSL v2 ciphers.

=item B<-tls1>

only include TLS v1 ciphers.

=item B<-h>, B<-?>

print a brief usage message.

=item B<cipherlist>

a cipher list to convert to a cipher preference list. If it is not included
then the default cipher list will be used. The format is described below.

=back

=head1 CIPHER LIST FORMAT

The cipher list consists of one or more I<cipher strings> separated by colons.
Commas or spaces are also acceptable separators but colons are normally used.

The actual cipher string can take several different forms.

It can consist of a single cipher suite such as B<RC4-SHA>.

It can represent a list of cipher suites containing a certain algorithm, or
cipher suites of a certain type. For example B<SHA1> represents all ciphers
suites using the digest algorithm SHA1 and B<SSLv3> represents all SSL v3
algorithms.

Lists of cipher suites can be combined in a single cipher string using the
B<+> character. This is used as a logical B<and> operation. For example
B<SHA1+DES> represents all cipher suites containing the SHA1 B<and> the DES
algorithms.

Each cipher string can be optionally preceded by the characters B<!>,
B<-> or B<+>.

If B<!> is used then the ciphers are permanently deleted from the list.
The ciphers deleted can never reappear in the list even if they are
explicitly stated.

If B<-> is used then the ciphers are deleted from the list, but some or
all of the ciphers can be added again by later options.

If B<+> is used then the ciphers are moved to the end of the list. This
option doesn't add any new ciphers it just moves matching existing ones.

If none of these characters is present then the string is just interpreted
as a list of ciphers to be appended to the current preference list. If the
list includes any ciphers already present they will be ignored: that is they
will not moved to the end of the list.

Additionally the cipher string B<@STRENGTH> can be used at any point to sort
the current cipher list in order of encryption algorithm key length.

=head1 CIPHER STRINGS

The following is a list of all permitted cipher strings and their meanings.

=over 4

=item B<DEFAULT>

the default cipher list. This is determined at compile time and is normally
B<ALL:!ADH:RC4+RSA:+SSLv2:@STRENGTH>. This must be the first cipher string
specified.

=item B<ALL>

all ciphers suites except the B<eNULL> ciphers which must be explicitly enabled.

=item B<HIGH>

"high" encryption cipher suites. This currently means those with key lengths larger
than 128 bits.

=item B<MEDIUM>

"medium" encryption cipher suites, currently those using 128 bit encryption.

=item B<LOW>

"low" encryption cipher suites, currently those using 64 or 56 bit encryption algorithms
but excluding export cipher suites.

=item B<EXP>, B<EXPORT>

export encryption algorithms. Including 40 and 56 bits algorithms.

=item B<EXPORT40>

40 bit export encryption algorithms

=item B<EXPORT56>

56 bit export encryption algorithms.

=item B<eNULL>, B<NULL>

the "NULL" ciphers that is those offering no encryption. Because these offer no
encryption at all and are a security risk they are disabled unless explicitly
included.

=item B<aNULL>

the cipher suites offering no authentication. This is currently the anonymous
DH algorithms. These cipher suites are vulnerable to a "man in the middle"
attack and so their use is normally discouraged.

=item B<kRSA>, B<RSA>

cipher suites using RSA key exchange.

=item B<kEDH>

cipher suites using ephemeral DH key agreement.

=item B<kDHr>, B<kDHd>

cipher suites using DH key agreement and DH certificates signed by CAs with RSA
and DSS keys respectively. Not implemented.

=item B<aRSA>

cipher suites using RSA authentication, i.e. the certificates carry RSA keys.

=item B<aDSS>, B<DSS>

cipher suites using DSS authentication, i.e. the certificates carry DSS keys.

=item B<aDH>

cipher suites effectively using DH authentication, i.e. the certificates carry
DH keys.  Not implemented.

=item B<kFZA>, B<aFZA>, B<eFZA>, B<FZA>

ciphers suites using FORTEZZA key exchange, authentication, encryption or all
FORTEZZA algorithms. Not implemented.

=item B<TLSv1>, B<SSLv3>, B<SSLv2>

TLS v1.0, SSL v3.0 or SSL v2.0 cipher suites respectively.

=item B<DH>

cipher suites using DH, including anonymous DH.

=item B<ADH>

anonymous DH cipher suites.

=item B<3DES>

cipher suites using triple DES.

=item B<DES>

cipher suites using DES (not triple DES).

=item B<RC4>

cipher suites using RC4.

=item B<RC2>

cipher suites using RC2.

=item B<IDEA>

cipher suites using IDEA.

=item B<MD5>

cipher suites using MD5.

=item B<SHA1>, B<SHA>

cipher suites using SHA1.

=back

=head1 CIPHER SUITE NAMES

The following lists give the SSL or TLS cipher suites names from the
relevant specification and their OpenSSL equivalents.

=head2 SSL v3.0 cipher suites.

 SSL_RSA_WITH_NULL_MD5                   NULL-MD5
 SSL_RSA_WITH_NULL_SHA                   NULL-SHA
 SSL_RSA_EXPORT_WITH_RC4_40_MD5          EXP-RC4-MD5
 SSL_RSA_WITH_RC4_128_MD5                RC4-MD5
 SSL_RSA_WITH_RC4_128_SHA                RC4-SHA
 SSL_RSA_EXPORT_WITH_RC2_CBC_40_MD5      EXP-RC2-CBC-MD5
 SSL_RSA_WITH_IDEA_CBC_SHA               IDEA-CBC-SHA
 SSL_RSA_EXPORT_WITH_DES40_CBC_SHA       EXP-DES-CBC-SHA
 SSL_RSA_WITH_DES_CBC_SHA                DES-CBC-SHA
 SSL_RSA_WITH_3DES_EDE_CBC_SHA           DES-CBC3-SHA

 SSL_DH_DSS_EXPORT_WITH_DES40_CBC_SHA    Not implemented.
 SSL_DH_DSS_WITH_DES_CBC_SHA             Not implemented.
 SSL_DH_DSS_WITH_3DES_EDE_CBC_SHA        Not implemented.
 SSL_DH_RSA_EXPORT_WITH_DES40_CBC_SHA    Not implemented.
 SSL_DH_RSA_WITH_DES_CBC_SHA             Not implemented.
 SSL_DH_RSA_WITH_3DES_EDE_CBC_SHA        Not implemented.
 SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA   EXP-EDH-DSS-DES-CBC-SHA
 SSL_DHE_DSS_WITH_DES_CBC_SHA            EDH-DSS-CBC-SHA
 SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA       EDH-DSS-DES-CBC3-SHA
 SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA   EXP-EDH-RSA-DES-CBC-SHA
 SSL_DHE_RSA_WITH_DES_CBC_SHA            EDH-RSA-DES-CBC-SHA
 SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA       EDH-RSA-DES-CBC3-SHA

 SSL_DH_anon_EXPORT_WITH_RC4_40_MD5      EXP-ADH-RC4-MD5
 SSL_DH_anon_WITH_RC4_128_MD5            ADH-RC4-MD5
 SSL_DH_anon_EXPORT_WITH_DES40_CBC_SHA   EXP-ADH-DES-CBC-SHA
 SSL_DH_anon_WITH_DES_CBC_SHA            ADH-DES-CBC-SHA
 SSL_DH_anon_WITH_3DES_EDE_CBC_SHA       ADH-DES-CBC3-SHA

 SSL_FORTEZZA_KEA_WITH_NULL_SHA          Not implemented.
 SSL_FORTEZZA_KEA_WITH_FORTEZZA_CBC_SHA  Not implemented.
 SSL_FORTEZZA_KEA_WITH_RC4_128_SHA       Not implemented.

=head2 TLS v1.0 cipher suites.

 TLS_RSA_WITH_NULL_MD5                   NULL-MD5
 TLS_RSA_WITH_NULL_SHA                   NULL-SHA
 TLS_RSA_EXPORT_WITH_RC4_40_MD5          EXP-RC4-MD5
 TLS_RSA_WITH_RC4_128_MD5                RC4-MD5
 TLS_RSA_WITH_RC4_128_SHA                RC4-SHA
 TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5      EXP-RC2-CBC-MD5
 TLS_RSA_WITH_IDEA_CBC_SHA               IDEA-CBC-SHA
 TLS_RSA_EXPORT_WITH_DES40_CBC_SHA       EXP-DES-CBC-SHA
 TLS_RSA_WITH_DES_CBC_SHA                DES-CBC-SHA
 TLS_RSA_WITH_3DES_EDE_CBC_SHA           DES-CBC3-SHA

 TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA    Not implemented.
 TLS_DH_DSS_WITH_DES_CBC_SHA             Not implemented.
 TLS_DH_DSS_WITH_3DES_EDE_CBC_SHA        Not implemented.
 TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA    Not implemented.
 TLS_DH_RSA_WITH_DES_CBC_SHA             Not implemented.
 TLS_DH_RSA_WITH_3DES_EDE_CBC_SHA        Not implemented.
 TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA   EXP-EDH-DSS-DES-CBC-SHA
 TLS_DHE_DSS_WITH_DES_CBC_SHA            EDH-DSS-CBC-SHA
 TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA       EDH-DSS-DES-CBC3-SHA
 TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA   EXP-EDH-RSA-DES-CBC-SHA
 TLS_DHE_RSA_WITH_DES_CBC_SHA            EDH-RSA-DES-CBC-SHA
 TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA       EDH-RSA-DES-CBC3-SHA

 TLS_DH_anon_EXPORT_WITH_RC4_40_MD5      EXP-ADH-RC4-MD5
 TLS_DH_anon_WITH_RC4_128_MD5            ADH-RC4-MD5
 TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA   EXP-ADH-DES-CBC-SHA
 TLS_DH_anon_WITH_DES_CBC_SHA            ADH-DES-CBC-SHA
 TLS_DH_anon_WITH_3DES_EDE_CBC_SHA       ADH-DES-CBC3-SHA

=head2 Additional Export 1024 and other cipher suites

Note: these ciphers can also be used in SSL v3.

 TLS_RSA_EXPORT1024_WITH_DES_CBC_SHA     EXP1024-DES-CBC-SHA
 TLS_RSA_EXPORT1024_WITH_RC4_56_SHA      EXP1024-RC4-SHA
 TLS_DHE_DSS_EXPORT1024_WITH_DES_CBC_SHA EXP1024-DHE-DSS-DES-CBC-SHA
 TLS_DHE_DSS_EXPORT1024_WITH_RC4_56_SHA  EXP1024-DHE-DSS-RC4-SHA
 TLS_DHE_DSS_WITH_RC4_128_SHA            DHE-DSS-RC4-SHA

=head2 SSL v2.0 cipher suites.

 SSL_CK_RC4_128_WITH_MD5                 RC4-MD5
 SSL_CK_RC4_128_EXPORT40_WITH_MD5        EXP-RC4-MD5
 SSL_CK_RC2_128_CBC_WITH_MD5             RC2-MD5
 SSL_CK_RC2_128_CBC_EXPORT40_WITH_MD5    EXP-RC2-MD5
 SSL_CK_IDEA_128_CBC_WITH_MD5            IDEA-CBC-MD5
 SSL_CK_DES_64_CBC_WITH_MD5              DES-CBC-MD5
 SSL_CK_DES_192_EDE3_CBC_WITH_MD5        DES-CBC3-MD5

=head1 NOTES

The non-ephemeral DH modes are currently unimplemented in OpenSSL
because there is no support for DH certificates.

Some compiled versions of OpenSSL may not include all the ciphers
listed here because some ciphers were excluded at compile time.

=head1 EXAMPLES

Verbose listing of all OpenSSL ciphers including NULL ciphers:

 openssl ciphers -v 'ALL:eNULL'

Include all ciphers except NULL and anonymous DH then sort by
strength:

 openssl ciphers -v 'ALL:!ADH:@STRENGTH'

Include only 3DES ciphers and then place RSA ciphers last:

 openssl ciphers -v '3DES:+RSA'

=head1 SEE ALSO

L<s_client(1)|s_client(1)>, L<s_server(1)|s_server(1)>, L<ssl(3)|ssl(3)>

=cut