http://docs.splunk.com/Documentation/Splunk/6.1.5/Admin/Inputsconf
I suspect your question may have been pre-dated 6.1.5, but you can select tls1.2 as the sslVersion in the inputconf.
sslVersions =
* Comma-separated list of SSL versions to support
* The versions available are "ssl2", "ssl3", "tls1.0", "tls1.1", and "tls1.2"
* The special version "" selects all supported versions. The version "tls"
selects all versions tls1.0 or newer
* If a version is prefixed with "-" it is removed from the list
* When configured in FIPS mode ssl2 and ssl3 are always disabled regardless of this configuration
* Defaults to ",-ssl2". (anything newer than SSLv2)
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