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BSDftpd-ssl project <URL: http://bsdftpd-ssl.sc.ru/ >
OpenSSL/BSDftpd-ssl cipher list format description
Author: Nick Leuta <skynick@mail.sc.ru>
23 November, 2003
This document is an adapted version of the ciphers(1) man page from the
OpenSSL 0.9.7 distribution.
CONTENTS
========
1. CIPHER LIST USAGE
2. CIPHER LIST FORMAT
3. CIPHER STRINGS
4. CIPHER SUITE NAMES
5. NOTES
6. EXAMPLES
1. CIPHER LIST USAGE
--------------------
The cipher list string should be universally usable and not depend on details
of the OpenSSL library configuration (ciphers compiled in). Thus no syntax
checking takes place. Items that are not recognized, because the corresponding
ciphers are not compiled in or because they are mistyped, are simply ignored.
Failure is only flagged if no ciphers could be collected at all.
It should be noted that inclusion of a cipher to be used into the list is
a necessary condition. On the client side, the inclusion into the list is
also sufficient. On the server side, additional restrictions apply. All ciphers
have additional requirements. ADH ciphers don't need a certificate, but
DH-parameters must have been set. All other ciphers need a corresponding
certificate and the key. A RSA cipher can only be chosen, when a RSA
certificate is available, the respective is valid for DSA ciphers. Ciphers
using EDH need a certificate, the key and DH-parameters.
2. CIPHER LIST FORMAT
---------------------
The cipher list consists of one or more 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 "RC4-SHA".
It can represent a list of cipher suites containing a certain algorithm, or
cipher suites of a certain type. For example "SHA1" represents all ciphers
suites using the digest algorithm SHA1 and "SSLv3" represents all SSL v3
algorithms.
Lists of cipher suites can be combined in a single cipher string using the
"+" character. It is used as the logical "and" operation. For example
"SHA1+DES" represents all cipher suites containing the SHA1 and the DES
algorithms.
Each cipher string can be optionally preceded by the characters "!",
"-" or "+".
If "!" 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 "-" 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 "+" 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 are they
will not moved to the end of the list.
Additionally the cipher string "@STRENGTH" can be used at any point to sort
the current cipher list in order of an encryption algorithm key length.
3. CIPHER STRINGS
-----------------
The following is a list of all permitted cipher strings and their meanings.
DEFAULT
the default cipher list. This is determined at compile time and is normally
"ALL:!ADH:RC4+RSA:+SSLv2:@STRENGTH". This must be the first cipher string
specified.
ALL
all ciphers suites except the "eNULL" ciphers which must be explicitly
enabled.
HIGH
"high" encryption cipher suites. This currently means those with key lengths
larger than 128 bits.
MEDIUM
"medium" encryption cipher suites, currently those using 128 bit encryption.
LOW
"low" encryption cipher suites, currently those using 64 or 56 bit encryption
algorithms but excluding export cipher suites.
EXP, EXPORT
export encryption algorithms. Including 40 and 56 bits algorithms.
EXPORT40
40 bit export encryption algorithms
EXPORT56
56 bit export encryption algorithms.
eNULL, 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.
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.
kRSA, RSA
cipher suites using RSA key exchange.
kEDH
cipher suites using ephemeral DH key agreement.
kDHr, kDHd
cipher suites using DH key agreement and DH certificates signed by CAs with
RSA and DSS keys respectively. Not implemented.
aRSA
cipher suites using RSA authentication, i.e. the certificates carry RSA keys.
aDSS, DSS
cipher suites using DSS authentication, i.e. the certificates carry DSS keys.
aDH
cipher suites effectively using DH authentication, i.e. the certificates
carry DH keys. Not implemented.
kFZA, aFZA, eFZA, FZA
ciphers suites using FORTEZZA key exchange, authentication, encryption or
all FORTEZZA algorithms. Not implemented.
TLSv1, SSLv3, SSLv2
TLS v1.0, SSL v3.0 or SSL v2.0 cipher suites respectively.
DH
cipher suites using DH, including anonymous DH.
ADH
anonymous DH cipher suites.
AES
cipher suites using AES.
3DES
cipher suites using triple DES.
DES
cipher suites using DES (not triple DES).
RC4
cipher suites using RC4.
RC2
cipher suites using RC2.
IDEA
cipher suites using IDEA.
MD5
cipher suites using MD5.
SHA1, SHA
cipher suites using SHA1.
4. CIPHER SUITE NAMES
---------------------
The following lists give the SSL or TLS cipher suites names from the
relevant specification and their OpenSSL equivalents.
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.
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
AES ciphersuites from RFC3268, extending TLS v1.0
TLS_RSA_WITH_AES_128_CBC_SHA AES128-SHA
TLS_RSA_WITH_AES_256_CBC_SHA AES256-SHA
TLS_DH_DSS_WITH_AES_128_CBC_SHA DH-DSS-AES128-SHA
TLS_DH_DSS_WITH_AES_256_CBC_SHA DH-DSS-AES256-SHA
TLS_DH_RSA_WITH_AES_128_CBC_SHA DH-RSA-AES128-SHA
TLS_DH_RSA_WITH_AES_256_CBC_SHA DH-RSA-AES256-SHA
TLS_DHE_DSS_WITH_AES_128_CBC_SHA DHE-DSS-AES128-SHA
TLS_DHE_DSS_WITH_AES_256_CBC_SHA DHE-DSS-AES256-SHA
TLS_DHE_RSA_WITH_AES_128_CBC_SHA DHE-RSA-AES128-SHA
TLS_DHE_RSA_WITH_AES_256_CBC_SHA DHE-RSA-AES256-SHA
TLS_DH_anon_WITH_AES_128_CBC_SHA ADH-AES128-SHA
TLS_DH_anon_WITH_AES_256_CBC_SHA ADH-AES256-SHA
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
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
5. NOTES
--------
All DH modes are currently not supported by BSDftpd-ssl.
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.
6. EXAMPLES
-----------
Enable all OpenSSL ciphers including NULL ciphers:
ftps -z cipher=ALL:eNULL
Include only DES ciphers except export encryption algorithms then sort by
strength:
ftps -z cipher=DES:\!EXP:@STRENGTH