NAME
ciphers — SSL cipher display and cipher list tool
Synopsis
openssl ciphers [-v] [-ssl2] [-ssl3] [-tls1] [cipherlist]
DESCRIPTION
The 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.
COMMAND OPTIONS
-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 -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.
-ssl3
only include SSL v3 ciphers.
-ssl2
only include SSL v2 ciphers.
-tls1
only include TLS v1 ciphers.
-h, -?
print a brief usage message.
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.
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. This is used as a 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 is 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 encryption algorithm
key length.
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.
COMPLEMENTOFDEFAULT
the ciphers included in ALL, but not enabled by default. Currently
this is ADH. Note that this rule does not cover eNULL, which is
not included by ALL (use COMPLEMENTOFALL if necessary).
ALL
all ciphers suites except the eNULL ciphers which must be
explicitly enabled.
COMPLEMENTOFALL
the cipher suites not enabled by ALL, currently being eNULL.
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.
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.
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' |
Include all RC4 ciphers but leave out those without authentication:
openssl ciphers -v 'RC4:!COMPLEMENTOFDEFAULT' |
Include all chiphers with RSA authentication but leave out
ciphers without encryption.
openssl ciphers -v 'RSA:!COMPLEMENTOFALL' |
SEE ALSO
s_client(1), s_server(1), ssl(3)
HISTORY
The COMPLENTOFALL and COMPLEMENTOFDEFAULT selection options
were added in version 0.9.7.
