Configuring Cipher Suites

The Cipher Suites HTTPS cluster parameter lists the supported encryption algorithms for incoming HTTPS requests. If a client request comes into FortiADC that does not use a cipher in this list, the connection is refused. If this field is blank, then any cipher suite supported by FortiADC’s SSL implementation (or by Hardware SSL Acceleration, when enabled) will be accepted.

To view or set the Cipher Suites field for a cluster, click on the cluster name in the left navigational pane, select the HTTPS cluster, and then select the Security > SSL tab in the right pane.

Default Cipher Suites

The following default setting for cipher suite is used:

AES128-SHA:DES-CBC3-SHA:RC4-SHA:RC4-MD5:AES256-SHA

For an FortiADC with hardware acceleration enabled, the following default value is used:

DES-CBC3-SHA:RC4-SHA:RC4-MD5:AES256-SHA

See Replacing the Default Certificate, Key, and Cipherspec for descriptions on replacing the default cipher suite.R

Updating the Cipher Suites Field

This field can be used to specify a custom cipher suite required by the servers in a cluster. In general, to add a cipher suite, you specify a plus sigh (+) and then the name of the suite. To specifically exclude a cipher suite, use an exclamation point (!).

For example, SSLv2 encryption is supported by default. If your servers are required to support medium and high encryption using SSLv3 only, you can add “!SSLv2” to cipher suite. For example, the following cipher suite string will cause all non-SSLv3 client requests to be refused:

AES128-SHA:DES-CBC3-SHA:RC4-SHA:RC4-MD5:AES256-SHA:!SSLv2:+SSLv3

The Cipher Suites field requires a string in the format described in the OpenSSL cipher suite documentation, at:

http://www.openssl.org/docs/apps/ciphers.html

Supported Software Cipher Suites

The following table lists the software cipher suites supported by FortiADC.

Ciphers	Key Exchange	Protocol	Authentication	Encryption	Message Authentication Code
AES256-GCM-SHA384	RSA	TLSv1.2	RSA	AESGCM(256)	AEAD
AES256-SHA256	RSA	TLSv1.2	RSA	AES(256)	SHA256
AES256-SHA	RSA	SSLv3	RSA	AES(256)	SHA1
CAMELLIA256-SHA	RSA	SSLv3	RSA	Camellia(256)	SHA1
DES-CBC3-SHA	RSA	SSLv3	RSA	3DES(168)	SHA1
AES128-GCM-SHA256	RSA	TLSv1.2	RSA	AESGCM(128)	AEAD
AES128-SHA256	RSA	TLSv1.2	RSA	AES(128)	SHA256
AES128-SHA	RSA	SSLv3	RSA	AES(128)	SHA1
SEED-SHA	RSA	SSLv3	RSA	SEED(128)	SHA1
CAMELLIA128-SHA	RSA	SSLv3	RSA	Camellia(128)	SHA1
IDEA-CBC-SHA	RSA	SSLv3	RSA	IDEA(128)	SHA1
RC4-SHA	RSA	SSLv3	RSA	RC4(128)	SHA1
RC4-MD5	RSA	SSLv3	RSA	RC4(128)	MD5
DES-CBC-SHA	RSA	SSLv3	RSA	DES(56)	SHA1
EXP-DES-CBC-SHA	RSA(512)	SSLv3	RSA	DES(40)	SHA1 export
EXP-RC2-CBC-MD5	RSA(512)	SSLv3	RSA	RC2(40)	MD5 export
EXP-RC4-MD5	RSA(512)	SSLv3	RSA	RC4(40)	MD5 export
AES256-GCM-SHA384	RSA	TLSv1.2	RSA	AESGCM(256)	AEAD

Supported PFS Ciphersuites

The following table lists the PFS ciphersuites supported by FortiADC.

Ciphers	Key Exhange
ECDHE-RSA-AES256-GCM-SHA384	RSA
ECDHE-ECDSA-AES256-GCM-SHA384	ECDSA
ECDHE-RSA-AES256-SHA384	RSA
ECDHE-ECDSA-AES256-SHA384	ECDSA
ECDHE-RSA-AES256-SHA	RSA
ECDHE-ECDSA-AES256-SHA	ECDSA
DHE-DSS-AES256-GCM-SHA384	DSS
DHE-RSA-AES256-GCM-SHA384	RSA
DHE-RSA-AES256-SHA256	RSA
DHE-DSS-AES256-SHA256	DSS
DHE-RSA-AES256-SHA	RSA
DHE-DSS-AES256-SHA	DSS
DHE-RSA-CAMELLIA256-SHA	RSA
DHE-DSS-CAMELLIA256-SHA	DSS
ECDHE-RSA-AES128-GCM-SHA256	RSA
ECDHE-ECDSA-AES128-GCM-SHA256	ECDA
ECDHE-RSA-AES128-SHA256	RSA
ECDHE-ECDSA-AES128-SHA256	ECDSA
ECDHE-RSA-AES128-SHA	RSA
ECDHE-ECDSA-AES128-SHA	ECDSA
DHE-DSS-AES128-GCM-SHA256	DSS
DHE-RSA-AES128-GCM-SHA256	RSA
DHE-RSA-AES128-SHA256	RSA
DHE-DSS-AES128-SHA256	DSS
DHE-RSA-AES128-SHA	RSA
DHE-DSS-AES128-SHA	DSS
DHE-RSA-SEED-SHA	RSA
DHE-DSS-SEED-SHA	DSS
DHE-RSA-CAMELLIA128-SHA	RSA
DHE-DSS-CAMELLIA128-SHA	DSS
ECDHE-RSA-RC4-SHA	RSA
ECDHE-ECDSA-RC4-SHA	ECDSA
ECDHE-RSA-DES-CBC3-SHA	RSA
ECDHE-ECDSA-DES-CBC3-SHA	ECDSA

Supported Hardware Cipher Suites

Ciphers	Protocol	Key Exchange	Authentication	Encryption	Message Authentication Code
TLS1_RSA_EXPORT1024_WITH_RC4_56_MD5	<=TLS 1.1	RSA	RSA	RC4	MD5 export
TLS1_RSA_EXPORT1024_WITH_RC4_56_SHA;	<=TLS 1.1	RSA	RSA	RC4	SHA export
SSL3_RSA_RC4_40_MD5	<=TLS 1.1	RSA	RSA	RC4 (40)	MD5
TLS1_RSA_EXPORT1024_WITH_DES_CBC_SHA	<=TLS 1.1	RSA	RSA	DES	SHA
SSL3_RSA_DES_40_CBC_SHA;	<=TLS 1.1	RSA	RSA	DES (40)	SHA
SSL3_RSA_DES_64_CBC_SHA	<=TLS 1.1	RSA	RSA	DES (64)	SHA
SSL3_RSA_RC4_128_MD5	SSL 3.0	RSA	RSA	RC4 (128)	SHA
SSL3_RSA_RC4_128_SHA	SSL 3.0	RSA	RSA	RC4 (128)	SHA
SSL3_RSA_DES_192_CBC3_SHA	SSL 3.0	RSA	RSA	DES (192)	MD5
SSL2_RC4_128_WITH_MD5	SSL 2.0	RSA	RSA	RC4 (128)	MD5
SSL2_RC4_128_EXPORT40_WITH_MD5	SSL 2.0	RSA	RSA	RC4 (128)	MD5
SSL2_DES_64_CBC_WITH_MD5	SSL 2.0	RSA	RSA	DES (64)	MD5
SSL2_DES_192_EDE3_CBC_WITH_MD5	SSL 2.0	RSA	RSA	DES (192)	MD5
TLS1_RSA_WITH_AES_128_SHA	TLS 1.0	RSA	RSA	AES (128)	SHA
TLS_RSA_WITH_AES_256_SHA	TLS 1.0	RSA	RSA	AES (256)	SHA
TLS_RSA_WITH_AES_128_SHA256	TLS 1.2	RSA	RSA	AES (128)	SHA (256)
TLS_RSA_WITH_AES_256_SHA256	TLS 1.2	RSA	RSA	AES (256)	SHA (256)
TLS1_RSA_WITH_AES_128_GCM_SHA256	TLS 1.2	RSA	RSA	AESGCM (128)	SHA (256)
TLS1_RSA_WITH_AES_256_GCM_SHA384	TLS 1.2	RSA	RSA	AESGCM (256)	SHA (384)

Choosing the Cipher Suite for an HTTPS Cluster Connection

The cipher suite parameter for an HTTPS cluster lists all of the ciphers that can be negotiated between FortiADC and an incoming client attempting to connect to an HTTPS cluster. Similarly, the client application will have its own list of ciphers that it supports. The client and FortiADC need to go through a process of negotiating the cipher that will be used for the client connection -- if they cannot find a match, the connection will fail. The process of negotiating a cipher for a client connection is as follows:

During the SSL handshake phase of the connection, the client sends FortiADC a list of the ciphers it supports.
FortiADC examines the client cipher list in the order it is specified, chooses the first cipher that matches a cipher specified in the cluster’s Cipher Suite parameter, and responds to the client. If none of the ciphers offered by the client are in the Cipher Suite list for the cluster, the SSL handshake fails.

It is therefore vital that you ensure that there is at least one match between the list of ciphers supported by clients connecting to an HTTPS cluster and the Cipher Suite list for the cluster.