Use the ciphers command of the cell management tool to configure the set of cipher suites that the cell offers to use during the SSL handshake process.

When a client makes an SSL connection to a vCloud Director cell, the cell offers to use only those ciphers that are configured on its default list of allowed ciphers. Several ciphers are not on this list, either because they are not strong enough to secure the connection, or because they are known to contribute to SSL connection failures. When you install or upgrade vCloud Director, the installation or upgrade script examines the cell's certificates. If any of the certificates are encrypted using a cipher that is not on the list of allowed ciphers, the script modifies the cell's configuration to allow use of that cipher and displays a warning. You can continue using the existing certificates despite their dependence on these ciphers, or you can take the following steps to replace the certificates and reconfigure the list of allowed ciphers:

  1. Create new certificates that do not use any of the disallowed ciphers. You can use cell-management-tool ciphers -a as shown in List All Allowed Ciphers to list all the ciphers that are allowed in the default configuration.

  2. Use the cell-management-tool certificates command to replace the cell's existing certificates with the new ones.

  3. Use the cell-management-tool ciphers command to reconfigure the list of allowed ciphers to exclude any ciphers not used by the new certificates. Excluding these ciphers can make it faster to establish an SSL connection to the cell, since the number of ciphers offered during the handshake is reduced to the practical minimum.

    Important:

    Because the VMRC console requires the use of the AES256-SHA and AES128-SHA ciphers, you cannot disallow them if your vCloud Director clients use the VMRC console.

To manage the list of allowed SSL ciphers, use a command line with the following form:

cell-management-tool ciphers options

Table 1. Cell Management Tool Options and Arguments, ciphers Subcommand

Option

Argument

Description

--help (-h)

None

Provides a summary of available commands in this category.

--all-allowed (-a)

None

List all allowed ciphers.

--compatible-reset (-c)

None

Reset to default list of allowed ciphers, and also allow ciphers used by this cell's certificates.

--disallow (-d)

Comma-separated list of cipher names, as published at http://www.openssl.org/docs/apps/ciphers.html

Disallow the ciphers in specified comma-separated list.

--list (-l)

None

List currently configured ciphers.

--reset (-r)

None

Reset to default list of allowed ciphers. If this cell's certificates use disallowed ciphers, you will not be able to make an SSL connection to the cell until you install new certificates that use an allowed cipher.

List All Allowed Ciphers

Use the --all-allowed (-a) option to list all the ciphers that the cell is currently allowed to offer during an SSL handshake.

[root@cell1 /opt/vmware/vcloud-director/bin]# ./cell-management-tool ciphers –a

* TLS_DHE_DSS_WITH_AES_256_CBC_SHA
* TLS_DHE_DSS_WITH_AES_128_CBC_SHA
* TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
* TLS_DHE_RSA_WITH_AES_256_CBC_SHA
* TLS_DHE_RSA_WITH_AES_128_CBC_SHA
* TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA
* TLS_RSA_WITH_AES_256_CBC_SHA
* TLS_RSA_WITH_AES_128_CBC_SHA
* TLS_RSA_WITH_3DES_EDE_CBC_SHA
* TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
* TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
* TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA
* TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
* TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
* TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA
* TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA
* TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA
* TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA
* TLS_ECDH_RSA_WITH_AES_256_CBC_SHA
* TLS_ECDH_RSA_WITH_AES_128_CBC_SHA
* TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA
* SSL_RSA_WITH_3DES_EDE_CBC_SHA
* SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA

Disallow Two Ciphers

Use the --disallow (-d) option to remove one or more ciphers from the list of allowed ciphers. This option requires at least one cipher name. You can supply multiple cipher names in a comma-separated list. You can obtain names for this list from the output of ciphers –a. This example removes two ciphers listed in the previous example.

[root@cell1 /opt/vmware/vcloud-director/bin]# ./cell-management-tool ciphers –d SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA,SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA