Documentation for recent SRTP changes

conf/vanilla/vars.xml

@@ -57,7 +57,90 @@
       http://wiki.freeswitch.org/wiki/ZRTP (on how to enable zrtp)
   -->
   <X-PRE-PROCESS cmd="set" data="zrtp_secure_media=true"/>
+  <!--
+      Supported SRTP Crypto Suites:
+
+
+      AEAD_AES_256_GCM_8
+      ____________________________________________________________________________
+      This algorithm is identical to AEAD_AES_256_GCM (see Section 5.2 of
+      [RFC5116]), except that the tag length, t, is 8, and an
+      authentication tag with a length of 8 octets (64 bits) is used.
+      An AEAD_AES_256_GCM_8 ciphertext is exactly 8 octets longer than its
+      corresponding plaintext.
+
+
+      AEAD_AES_128_GCM_8
+      ____________________________________________________________________________
+      This algorithm is identical to AEAD_AES_128_GCM (see Section 5.1 of
+      [RFC5116]), except that the tag length, t, is 8, and an
+      authentication tag with a length of 8 octets (64 bits) is used.
+      An AEAD_AES_128_GCM_8 ciphertext is exactly 8 octets longer than its
+      corresponding plaintext.
+
+
+      AES_CM_256_HMAC_SHA1_80 | AES_CM_192_HMAC_SHA1_80 | AES_CM_128_HMAC_SHA1_80
+      ____________________________________________________________________________
+      AES_CM_128_HMAC_SHA1_80 is the SRTP default AES Counter Mode cipher
+      and HMAC-SHA1 message authentication with an 80-bit authentication
+      tag. The master-key length is 128 bits and has a default lifetime of
+      a maximum of 2^48 SRTP packets or 2^31 SRTCP packets, whichever comes
+      first.
+
+
+      AES_CM_256_HMAC_SHA1_32 | AES_CM_192_HMAC_SHA1_32 | AES_CM_128_HMAC_SHA1_32
+      ____________________________________________________________________________
+      This crypto-suite is identical to AES_CM_128_HMAC_SHA1_80 except that
+      the authentication tag is 32 bits. The length of the base64-decoded key and
+      salt value for this crypto-suite MUST be 30 octets i.e., 240 bits; otherwise,
+      the crypto attribute is considered invalid.
+
+      AES_CM_128_NULL_AUTH
+      ____________________________________________________________________________
+      The SRTP default cipher (AES-128 Counter Mode), but to use no authentication
+      method.  This policy is NOT RECOMMENDED unless it is unavoidable; see 
+      Section 7.5 of [RFC3711].
 
+
+      SRTP variables that modify behaviors based on direction/leg:
+
+      rtp_secure_media
+      ____________________________________________________________________________
+      possible values:
+          mandatory - Accept/Offer SAVP negotiation ONLY
+          optional  - Accept/Offer SAVP/AVP with SAVP preferred 
+          forbidden - More useful for inbound to deny SAVP negotiation
+          false     - implies forbidden
+          true      - implies mandatory
+
+      rtp_secure_media_inbound | rtp_secure_media_outbound
+      ____________________________________________________________________________
+      This is the same as rtp_secure_media, but would apply to either inbound
+      or outbound offers specifically.
+
+      How to specify crypto suites:
+      ____________________________________________________________________________
+      By default without specifying any crypto suites FreeSWITCH will offer
+      crypto suites from strongest to weakest accepting the strongest each
+      endpoint has in common.  If you wish to force specific crypto suites you
+      can do so by appending the suites in a comma separated list in the order
+      that you wish to offer them in.
+
+      Examples:
+
+          rtp_secure_media=mandatory:AES_CM_256_HMAC_SHA1_80,AES_CM_256_HMAC_SHA1_32
+          rtp_secure_media=true:AES_CM_256_HMAC_SHA1_80,AES_CM_256_HMAC_SHA1_32
+          rtp_secure_media=optional:AES_CM_256_HMAC_SHA1_80
+          rtp_secure_media=true:AES_CM_256_HMAC_SHA1_80
+
+      Additionally you can narrow this down on either inbound or outbound by
+      specifying as so:
+
+          rtp_secure_media_inbound=true:AEAD_AES_256_GCM_8
+          rtp_secure_media_inbound=mandatory:AEAD_AES_256_GCM_8
+          rtp_secure_media_outbound=true:AEAD_AES_128_GCM_8
+          rtp_secure_media_outbound=optional:AEAD_AES_128_GCM_8
+  -->
   <!-- 
        Examples of codec options: (module must be compiled and loaded)