doc: add SIP keywords

doc/userguide/rules/index.rst

@@ -24,6 +24,7 @@ Suricata Rules
    kerberos-keywords
    snmp-keywords
    base64-keywords
+   sip-keywords
    app-layer
    xbits
    thresholding

doc/userguide/rules/sip-keywords.rst

@@ -0,0 +1,179 @@
+SIP Keywords
+============
+
+The SIP keywords are implemented as sticky buffers and can be used to match on fields in SIP messages.
+
+============================== ==================
+Keyword                        Direction
+============================== ==================
+sip.method                     Request
+sip.uri                        Request
+sip.request_line               Request
+sip.stat_code                  Response
+sip.stat_msg                   Response
+sip.response_line              Response
+sip.protocol                   Both
+============================== ==================
+
+sip.method
+----------
+
+This keyword matches on the method found in a SIP request.
+
+Syntax
+~~~~~~
+
+::
+
+  sip.method; content:<method>;
+
+Examples of methods are:
+
+* INVITE
+* BYE
+* REGISTER
+* CANCEL
+* ACK
+* OPTIONS
+
+Examples
+~~~~~~~~
+
+::
+
+  sip.method; content:"INVITE";
+
+sip.uri
+-------
+
+This keyword matches on the uri found in a SIP request.
+
+Syntax
+~~~~~~
+
+::
+
+  sip.uri; content:<uri>;
+
+Where <uri> is an uri that follows the SIP URI scheme.
+
+Examples
+~~~~~~~~
+
+::
+
+  sip.uri; content:"sip:sip.url.org";
+
+sip.request_line
+----------------
+
+This keyword forces the whole SIP request line to be inspected.
+
+Syntax
+~~~~~~
+
+::
+
+  sip.request_line; content:<request_line>;
+
+Where <request_line> is a partial or full line.
+
+Examples
+~~~~~~~~
+
+::
+
+  sip.request_line; content:"REGISTER sip:sip.url.org SIP/2.0"
+
+sip.stat_code
+-------------
+
+This keyword matches on the status code found in a SIP response.
+
+Syntax
+~~~~~~
+
+::
+
+  sip.stat_code; content:<stat_code>
+
+Where <status_code> belongs to one of the following groups of codes:
+
+* 1xx - Provisional Responses
+* 2xx - Successful Responses
+* 3xx - Redirection Responses
+* 4xx - Client Failure Responses
+* 5xx - Server Failure Responses
+* 6xx - Global Failure Responses
+
+Examples
+~~~~~~~~
+
+::
+
+  sip.stat_code; content:"100";
+
+sip.stat_msg
+------------
+
+This keyword matches on the status message found in a SIP response.
+
+Syntax
+~~~~~~
+
+::
+
+  sip.stat_msg; content:<stat_msg>
+
+Where <stat_msg> is a reason phrase associated to a status code.
+
+Examples
+~~~~~~~~
+
+::
+
+  sip.stat_msg; content:"Trying";
+
+sip.response_line
+-----------------
+
+This keyword forces the whole SIP response line to be inspected.
+
+Syntax
+~~~~~~
+
+::
+
+  sip.response_line; content:<response_line>;
+
+Where <response_line> is a partial or full line.
+
+Examples
+~~~~~~~~
+
+::
+
+  sip.response_line; content:"SIP/2.0 100 OK"
+
+sip.protocol
+------------
+
+This keyword matches the protocol field from a SIP request or response line.
+
+If the response line is 'SIP/2.0 100 OK', then this buffer will contain 'SIP/2.0'
+
+Syntax
+~~~~~~
+
+::
+
+  sip.protocol; content:<protocol>
+
+Where <protocol> is the SIP protocol version.
+
+Example
+~~~~~~~
+
+::
+
+  sip.protocol; content:"SIP/2.0"