/* packet-sip.c
 * Routines for the Session Initiation Protocol (SIP) dissection.
 * RFC 2543
 * 
 * TODO: Pay attention to Content-Type: It might not always be SDP.
 *       Add hf_* fields for filtering support.
 *       Add sip msg body dissection based on Content-Type for:
 *                SDP, MIME, and other types
 *       Align SIP methods with recent Internet Drafts or RFC
 *               (SIP INFO, rfc2976 - done)
 *               (SIP SUBSCRIBE-NOTIFY - done)
 *               (SIP REFER - done)
 *               check for other
 *
 * Copyright 2000, Heikki Vatiainen <hessu@cs.tut.fi>
 * Copyright 2001, Jean-Francois Mule <jfm@clarent.com>
 *
 * $Id: packet-sip.c,v 1.29 2002/05/09 08:27:51 guy Exp $
 *
 * Ethereal - Network traffic analyzer
 * By Gerald Combs <gerald@ethereal.com>
 * Copyright 1998 Gerald Combs
 *
 * Copied from packet-cops.c
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <glib.h>
#include <epan/packet.h>

#define TCP_PORT_SIP 5060
#define UDP_PORT_SIP 5060

/* Initialize the protocol and registered fields */
static gint proto_sip = -1;
static gint hf_msg_hdr = -1;

/* Initialize the subtree pointers */
static gint ett_sip = -1;
static gint ett_sip_hdr = -1;

static const char *sip_methods[] = {
        "<Invalid method>",      /* Pad so that the real methods start at index 1 */
        "ACK",
        "BYE",
        "CANCEL",
        "DO",
        "INFO",
        "INVITE",
        "MESSAGE",
        "NOTIFY",
        "OPTIONS",
        "PRACK",
        "QAUTH",
        "REFER",
        "REGISTER",
        "SPRACK",
        "SUBSCRIBE"
};

static gboolean sip_is_request(tvbuff_t *tvb, gint eol);
static gboolean sip_is_known_request(tvbuff_t *tvb, guint32 offset);
static gint sip_get_msg_offset(tvbuff_t *tvb, guint32 offset);
 
static dissector_handle_t sdp_handle;
static dissector_handle_t data_handle;

#define SIP2_HDR "SIP/2.0"
#define SIP2_HDR_LEN (strlen (SIP2_HDR))

/* Code to actually dissect the packets */
static void dissect_sip(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
        guint32 offset;
        gint eol, next_offset, msg_offset;
        tvbuff_t *next_tvb;
        gboolean is_request, is_known_request;
        char *req_descr;

        /*
         * Note that "tvb_strneql()" doesn't throw exceptions, so
         * "sip_is_request()" won't throw an exception.
         *
         * Note that "tvb_find_line_end()" will return a value that
         * is not longer than what's in the buffer, so the
         * "tvb_get_ptr()" call s below won't throw exceptions.
         */
        offset = 0;
        eol = tvb_find_line_end(tvb, 0, -1, &next_offset);
        /* XXX - Check for a valid status message as well. */
        is_request = sip_is_request(tvb, eol);
        is_known_request = sip_is_known_request(tvb, 0);
        /* XXX - Is this case-sensitive?  RFC 2543 didn't explicitly say. */
        if (tvb_strneql(tvb, 0, SIP2_HDR, SIP2_HDR_LEN) != 0 && ! is_request)
                goto bad;

        if (check_col(pinfo->cinfo, COL_PROTOCOL)) 
                col_set_str(pinfo->cinfo, COL_PROTOCOL, "SIP");
    
        req_descr = is_known_request ? "Request" : "Unknown request";
        if (check_col(pinfo->cinfo, COL_INFO))
                col_add_fstr(pinfo->cinfo, COL_INFO, "%s: %s",
                             is_request ? req_descr : "Status",
                             is_request ?
                             tvb_format_text(tvb, 0, eol - SIP2_HDR_LEN - 1) :
                             tvb_format_text(tvb, SIP2_HDR_LEN + 1, eol - SIP2_HDR_LEN - 1));


        msg_offset = sip_get_msg_offset(tvb, offset);
        if (msg_offset < 0) {
                /*
                 * XXX - this may just mean that the entire SIP message
                 * didn't fit in this TCP segment.
                 */
                goto bad;
        }

        if (tree) {
                proto_item *ti, *th;
                proto_tree *sip_tree, *hdr_tree;

                ti = proto_tree_add_item(tree, proto_sip, tvb, 0, -1, FALSE);
                sip_tree = proto_item_add_subtree(ti, ett_sip);

                proto_tree_add_text(sip_tree, tvb, 0, next_offset, "%s line: %s",
                                    is_request ? req_descr : "Status",
                                    tvb_format_text(tvb, 0, eol));

                offset = next_offset;
                th = proto_tree_add_item(sip_tree, hf_msg_hdr, tvb, offset, msg_offset - offset, FALSE);
                hdr_tree = proto_item_add_subtree(th, ett_sip_hdr);

                /* - 2 since we have a CRLF separating the message-body */
                while (msg_offset - 2 > (int) offset) {
                        eol = tvb_find_line_end(tvb, offset, -1, &next_offset);
                        proto_tree_add_text(hdr_tree, tvb, offset, next_offset - offset, "%s",
                                            tvb_format_text(tvb, offset, eol));
                        offset = next_offset;
                }
                offset += 2;  /* Skip the CRLF mentioned above */
       }

        if (tvb_offset_exists(tvb, msg_offset)) {
                next_tvb = tvb_new_subset(tvb, msg_offset, -1, -1);
                call_dissector(sdp_handle, next_tvb, pinfo, tree);
        }

        return;

  bad:
        next_tvb = tvb_new_subset(tvb, offset, -1, -1);
        call_dissector(data_handle,next_tvb, pinfo, tree);

        return;
}

static gboolean
dissect_sip_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
        gint eol, next_offset;

        /*
         * This is a heuristic dissector, which means we get all the
         * UDP and TCP traffic not sent to a known dissector and not
         * claimed by a heuristic dissector called before us!
         * So we first check if the frame is really meant for us.
         */

        /*
         * Check for a response.
         * First, make sure we have enough data to do the check.
         */
        if (!tvb_bytes_exist(tvb, 0, SIP2_HDR_LEN)) {
                /*
                 * We don't.
                 */
                return FALSE;
        }

        /*
         * Now see if we have a response header; they begin with
         * "SIP/2.0".
         */
        if (tvb_strneql(tvb, 0, SIP2_HDR, SIP2_HDR_LEN) != 0)  {
                /*
                 * We don't, so this isn't a response; check for a request.
                 * They *end* with "SIP/2.0".
                 */
                eol = tvb_find_line_end(tvb, 0, -1, &next_offset);
                if (eol <= (gint)SIP2_HDR_LEN) {
                        /*
                         * The line isn't long enough to end with "SIP/2.0".
                         */
                        return FALSE;
                }
                if (!tvb_bytes_exist(tvb, eol - SIP2_HDR_LEN + 1, SIP2_HDR_LEN)) {
                        /*
                         * We don't have enough of the data in the line
                         * to check.
                         */
                        return FALSE;
                }

                if (tvb_strneql(tvb, eol - SIP2_HDR_LEN + 1, SIP2_HDR, SIP2_HDR_LEN - 1) != 0) {
                        /*
                         * Not a request, either.
                         */
                        return FALSE;
                }
        }

        /*
         * The message seems to be a valid SIP message!
         */
        dissect_sip(tvb, pinfo, tree);

        return TRUE;
}


/* Returns the offset to the start of the optional message-body, or
 * -1 if not found.
 */
static gint sip_get_msg_offset(tvbuff_t *tvb, guint32 offset)
{
        gint eol;

        while ((eol = tvb_find_guint8(tvb, offset, -1, '\r')) > 0
            && tvb_bytes_exist(tvb, eol, 4)) {
                if (tvb_get_guint8(tvb, eol + 1) == '\n' && 
                    tvb_get_guint8(tvb, eol + 2) == '\r' && 
                    tvb_get_guint8(tvb, eol + 3) == '\n')
                        return eol + 4;
                offset = eol + 2;
        }

        return -1;
}

/* From section 4.1 of RFC 2543:
 *
 * Request-Line  =  Method SP Request-URI SP SIP-Version CRLF
 */ 

static gboolean sip_is_request(tvbuff_t *tvb, gint eol)
{
        gint meth_len, req_len, req_colon_pos;
        guint8 req_start, ver_start, ver_len;

        meth_len = tvb_find_guint8(tvb, 0, -1, ' ');
        req_start = meth_len + 1;
        req_len = tvb_find_guint8(tvb, req_start, -1, ' ') - meth_len - 1;
        req_colon_pos = tvb_find_guint8(tvb, req_start + 1, -1, ':');
        ver_start = meth_len + req_len + 2;
        ver_len = eol - req_len - meth_len - 2; /*CRLF, plus two spaces */

        /* Do we have:
         *   A method of at least one character?
         *   A URI consisting of at least three characters?
         *   A version string length matching that of SIP2_HDR?
         */
        if (meth_len <= 0 || req_len <= 3 || ver_len != SIP2_HDR_LEN)
                return FALSE;

        /* Does our method have a colon character? */
        if (req_colon_pos < 0 || req_colon_pos > ver_start)
                return FALSE;
        /* XXX - Check for a proper URI prefix? */
        
        /* Do we have a proper version string? */
        if (tvb_strneql(tvb, ver_start, SIP2_HDR, SIP2_HDR_LEN))
                return TRUE;

        return TRUE;
}

static gboolean sip_is_known_request(tvbuff_t *tvb, guint32 offset)
{
        guint8 i, meth_len;

        meth_len = tvb_find_guint8(tvb, 0, -1, ' ');

        for (i = 1; i < array_length(sip_methods); i++) {
                if ((meth_len == strlen(sip_methods[i])) && tvb_strneql(tvb, offset, sip_methods[i], strlen(sip_methods[i])) == 0)
                        return TRUE;
        }

        return FALSE;
}

/* Register the protocol with Ethereal */
void proto_register_sip(void)
{                 

        /* Setup list of header fields */
        static hf_register_info hf[] = {

                { &hf_msg_hdr,
                        { "Message Header",           "sip.msg_hdr",
                        FT_NONE, 0, NULL, 0,
                        "Message Header in SIP message", HFILL }
                },
        };

        /* Setup protocol subtree array */
        static gint *ett[] = {
                &ett_sip,
                &ett_sip_hdr,
        };

        /* Register the protocol name and description */
        proto_sip = proto_register_protocol("Session Initiation Protocol",
            "SIP", "sip");

        /* Required function calls to register the header fields and subtrees used */
        proto_register_field_array(proto_sip, hf, array_length(hf));
        proto_register_subtree_array(ett, array_length(ett));
}

void
proto_reg_handoff_sip(void)
{
        dissector_handle_t sip_handle;

        sip_handle = create_dissector_handle(dissect_sip, proto_sip);
        dissector_add("tcp.port", TCP_PORT_SIP, sip_handle);
        dissector_add("udp.port", UDP_PORT_SIP, sip_handle);

        heur_dissector_add( "udp", dissect_sip_heur, proto_sip );
        heur_dissector_add( "tcp", dissect_sip_heur, proto_sip );

        /*
         * Get a handle for the SDP dissector.
         */
        sdp_handle = find_dissector("sdp");
        data_handle = find_dissector("data");
}