332 lines
11 KiB
C
332 lines
11 KiB
C
/* packet-sapsnc.c
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* Routines for SAP SNC (Secure Network Connection) dissection
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* Copyright 2022, Martin Gallo <martin.gallo [AT] gmail.com>
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* Code contributed by SecureAuth Corp.
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*
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* Wireshark - Network traffic analyzer
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* By Gerald Combs <gerald@wireshark.org>
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* Copyright 1998 Gerald Combs
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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/*
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* This is a basic dissector for the SAP Secure Network Connection protocol. It dissects the basic
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* SNC frame fields, and if the QoP (quality of protection) is only set to wrap/seal but not encrypt,
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* it can be used to extract the content and further dissect it on an upper layer.
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*
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* Some details and example requests can be found in pysap's documentation: https://pysap.readthedocs.io/en/latest/protocols/SAPSNC.html.
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*/
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#include <config.h>
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#include <epan/packet.h>
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#include <epan/expert.h>
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#include "packet-sapsnc.h"
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/* SAP SNC Frame Type */
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static const value_string sapsnc_frame_type_vals[] = {
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{ 0x00, "REVERSE_REQ" },
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{ 0x01, "INIT_REQ" },
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{ 0x02, "INIT" },
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{ 0x03, "INIT_ACK" },
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{ 0x04, "ACCEPT" },
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{ 0x05, "ACCEPT_ACK" },
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{ 0x06, "ACCEPT_FAILED" },
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{ 0x07, "DATA_OPEN" },
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{ 0x08, "DATA_MIC/DATA_SIGNED" },
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{ 0x09, "DATA_WRAP/DATA_SEALED" },
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{ 0x0a, "SHUTDOWN" },
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{ 0x0b, "SHUTDOWN_MSG" },
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{ 0x0c, "REJECTED" },
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{ 0x0d, "ERROR" },
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{ 0x0e, "UNKNOWN" },
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{ 0, NULL }
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};
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/* SNC Mech ID values */
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static const value_string sapsnc_mech_id_vals[] = {
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{ 0x00, "No security" },
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{ 0x01, "Generic GSS-API v2 Mechanism" },
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{ 0x02, "Kerberos 5/GSS-API v2" },
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{ 0x03, "Secude 5 GSS-API v2" },
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{ 0x04, "SAP's GSS-API v2 over NTLM(SSPI)" },
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{ 0x05, "SPKM1 GSS-API v2 library" },
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{ 0x06, "SPKM2 GSS-API v2 library" },
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{ 0x07, "reserved ID" },
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{ 0x08, "itsec" },
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{ 0x09, "SDTI Connect Agent" },
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{ 0x0a, "AccessMaster DCE" },
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{ 0, NULL }
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};
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/* SNC Quality of protection values */
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static const value_string sapsnc_qop_vals[] = {
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{ 0x00, "INVALID" },
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{ 0x01, "OPEN" },
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{ 0x02, "INTEGRITY/SIGNED" },
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{ 0x03, "PRIVACY/SEALED" },
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{ 0x07, "MIN" },
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{ 0x08, "DEFAULT" },
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{ 0x09, "MAX" },
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{ 0, NULL }
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};
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static int proto_sapsnc = -1;
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/* SNC Frame */
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static int hf_sapsnc_frame = -1;
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static int hf_sapsnc_eye_catcher = -1;
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static int hf_sapsnc_frame_type = -1;
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static int hf_sapsnc_protocol_version = -1;
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static int hf_sapsnc_header_length = -1;
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static int hf_sapsnc_token_length = -1;
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static int hf_sapsnc_data_length = -1;
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static int hf_sapsnc_mech_id = -1;
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static int hf_sapsnc_flags = -1;
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static int hf_sapsnc_qop_min = -1;
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static int hf_sapsnc_qop_max = -1;
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static int hf_sapsnc_qop_use = -1;
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static int hf_sapsnc_ext_flags = -1;
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static int hf_sapsnc_ext_field_length = -1;
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static int hf_sapsnc_ext_field = -1;
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static int hf_sapsnc_token = -1;
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static int hf_sapsnc_data = -1;
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static gint ett_sapsnc = -1;
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/* Expert info */
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static expert_field ei_sapsnc_invalid_header_length = EI_INIT;
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void proto_reg_handoff_sapsnc(void);
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void proto_register_sapsnc(void);
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/**
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* Dissect an SNC Frame. If data it's found for wrapped/signed frames, it
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* returns a new TVB buffer with the content. This function can be called
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* from any dissector that wants SNC frames to be decoded.
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*/
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tvbuff_t*
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dissect_sapsnc_frame(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32 offset)
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{
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tvbuff_t *next_tvb = NULL;
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guint8 frame_type;
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guint32 header_length, ext_field_length, token_length = 0, data_length = 0;
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proto_item *sapsnc_frame = NULL, *sapsnc_flags = NULL, *sapsnc_header_length = NULL;
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proto_tree *sapsnc_frame_tree = NULL, *sapsnc_flags_tree = NULL;
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/* Add the SNC Frame subtree */
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sapsnc_frame = proto_tree_add_item(tree, hf_sapsnc_frame, tvb, offset, -1, ENC_NA);
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sapsnc_frame_tree = proto_item_add_subtree(sapsnc_frame, ett_sapsnc);
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/* Eye catcher */
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_eye_catcher, tvb, offset, 8, ENC_ASCII|ENC_NA);
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offset+=8;
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/* Frame type */
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frame_type = tvb_get_guint8(tvb, offset);
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_frame_type, tvb, offset, 1, ENC_BIG_ENDIAN);
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offset+=1;
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/* Protocol version */
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_protocol_version, tvb, offset, 1, ENC_BIG_ENDIAN);
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offset+=1;
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/* Header length */
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sapsnc_header_length = proto_tree_add_item_ret_uint(sapsnc_frame_tree, hf_sapsnc_header_length, tvb, offset, 2, ENC_BIG_ENDIAN, &header_length);
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/* We subtracts the 10 bytes of the header already processed */
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header_length -= 10;
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/* Check the header length, it should be at least 24 bytes */
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if (header_length < 14){
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expert_add_info_format(pinfo, sapsnc_header_length, &ei_sapsnc_invalid_header_length, "Invalid header length %u", header_length);
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header_length = 14;
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} else if ((guint32)tvb_reported_length_remaining(tvb, offset) < header_length) {
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expert_add_info_format(pinfo, sapsnc_header_length, &ei_sapsnc_invalid_header_length, "Invalid captured length %d (reported %u)", tvb_reported_length_remaining(tvb, offset), header_length);
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header_length = tvb_reported_length_remaining(tvb, offset);
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}
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offset+=2;
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header_length-=2;
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/* Token length */
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proto_tree_add_item_ret_uint(sapsnc_frame_tree, hf_sapsnc_token_length, tvb, offset, 4, ENC_BIG_ENDIAN, &token_length);
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offset+=4;
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header_length-=4;
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/* Data length */
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proto_tree_add_item_ret_uint(sapsnc_frame_tree, hf_sapsnc_data_length, tvb, offset, 4, ENC_BIG_ENDIAN, &data_length);
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offset+=4;
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header_length-=4;
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/* Mech ID */
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_mech_id, tvb, offset, 2, ENC_BIG_ENDIAN);
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offset+=2;
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header_length-=2;
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/* Build a tree for the flags */
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sapsnc_flags = proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_flags, tvb, offset, 2, ENC_NA);
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sapsnc_flags_tree = proto_item_add_subtree(sapsnc_flags, ett_sapsnc);
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offset+=1;
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header_length-=1; /* Unknown flags (1 byte) */
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/* Unknown flag (1 bit) */
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proto_tree_add_bits_item(sapsnc_flags_tree, hf_sapsnc_qop_min, tvb, offset*8 + 1, 2, ENC_BIG_ENDIAN);
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proto_tree_add_bits_item(sapsnc_flags_tree, hf_sapsnc_qop_max, tvb, offset*8 + 3, 2, ENC_BIG_ENDIAN);
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proto_tree_add_bits_item(sapsnc_flags_tree, hf_sapsnc_qop_use, tvb, offset*8 + 5, 2, ENC_BIG_ENDIAN);
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/* Unknown flag (1 bit) */
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offset+=1;
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header_length-=1;
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/* If there's header remaining, we add the extra flags, length and fields */
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if (header_length >= 6 && tvb_offset_exists(tvb, offset + 6)) {
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/* Get the extra flags */
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_ext_flags, tvb, offset, 4, ENC_NA);
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offset+=4;
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/* Get the extra field length */
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proto_tree_add_item_ret_uint(sapsnc_frame_tree, hf_sapsnc_ext_field_length, tvb, offset, 2, ENC_BIG_ENDIAN, &ext_field_length);
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offset+=2;
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/* If the extra field length is valid extract those */
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if (ext_field_length > 0 && tvb_offset_exists(tvb, offset + ext_field_length)) {
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_ext_field, tvb, offset, ext_field_length, ENC_NA);
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offset+=ext_field_length;
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}
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}
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/* Token */
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if (token_length > 0 && tvb_offset_exists(tvb, offset + token_length)) {
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_token, tvb, offset, token_length, ENC_NA);
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offset+=token_length;
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}
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/* Data */
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if (data_length > 0 && tvb_offset_exists(tvb, offset + data_length)) {
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proto_tree_add_item(sapsnc_frame_tree, hf_sapsnc_data, tvb, offset, data_length, ENC_NA);
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/* If the frame contain data being wrapped or sealed, put it into a new tvb for
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further dissection of the upper layer */
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if ((frame_type == 0x07) || (frame_type == 0x08)) {
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next_tvb = tvb_new_subset_remaining(tvb, offset);
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}
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}
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return next_tvb;
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}
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/**
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* Dissects SNC packets
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*/
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static int
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dissect_sapsnc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
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{
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/* Add the protocol to the column */
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col_add_str(pinfo->cinfo, COL_PROTOCOL, ", SAPSNC");
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/* Clear out stuff in the info column */
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col_clear(pinfo->cinfo,COL_INFO);
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/* Call the SNC frame dissection function */
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dissect_sapsnc_frame(tvb, pinfo, tree, 0);
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return tvb_reported_length(tvb);
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}
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void
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proto_register_sapsnc(void)
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{
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static hf_register_info hf[] = {
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/* SNC Frame */
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{ &hf_sapsnc_frame,
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{ "SNC Frame", "sapsnc.frame", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_eye_catcher,
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{ "SNC Eye Catcher", "sapsnc.eyecatcher", FT_STRING, BASE_NONE, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_frame_type,
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{ "SNC Frame Type", "sapsnc.frame.type", FT_UINT8, BASE_HEX, VALS(sapsnc_frame_type_vals), 0x0, NULL, HFILL }},
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{ &hf_sapsnc_protocol_version,
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{ "SNC Protocol Version", "sapsnc.frame.protocolversion", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_header_length,
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{ "SNC Header length", "sapsnc.frame.header_length", FT_UINT16, BASE_DEC, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_token_length,
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{ "SNC Token length", "sapsnc.frame.tokenlength", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_data_length,
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{ "SNC Data length", "sapsnc.frame.datalength", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_mech_id,
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{ "SNC Mech ID", "sapsnc.frame.mech_id", FT_UINT16, BASE_HEX, VALS(sapsnc_mech_id_vals), 0x0, NULL, HFILL }},
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{ &hf_sapsnc_flags,
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{ "SNC Flags", "sapsnc.frame.flags", FT_UINT16, BASE_HEX, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_qop_min,
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{ "SNC QOP Min", "sapsnc.frame.qop_min", FT_UINT8, BASE_HEX, VALS(sapsnc_qop_vals), 0x0, NULL, HFILL }},
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{ &hf_sapsnc_qop_max,
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{ "SNC QOP Max", "sapsnc.frame.qop_max", FT_UINT8, BASE_HEX, VALS(sapsnc_qop_vals), 0x0, NULL, HFILL }},
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{ &hf_sapsnc_qop_use,
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{ "SNC QOP Use", "sapsnc.frame.qop_use", FT_UINT8, BASE_HEX, VALS(sapsnc_qop_vals), 0x0, NULL, HFILL }},
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{ &hf_sapsnc_ext_flags,
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{ "SNC Extensions Flags", "sapsnc.frame.ext_flags", FT_UINT32, BASE_HEX, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_ext_field_length,
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{ "SNC Extensions Field length", "sapsnc.frame.ext_field_length", FT_UINT16, BASE_DEC, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_ext_field,
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{ "SNC Extensions Field", "sapsnc.frame.ext_field", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_token,
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{ "SNC Token", "sapsnc.frame.token", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }},
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{ &hf_sapsnc_data,
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{ "SNC Data", "sapsnc.frame.data", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }},
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};
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/* Setup protocol subtree array */
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static gint *ett[] = {
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&ett_sapsnc
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};
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/* Register the expert info */
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static ei_register_info ei[] = {
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{ &ei_sapsnc_invalid_header_length, { "sapsnc.frame.header_length_invalid", PI_MALFORMED, PI_WARN, "Invalid header length", EXPFILL }},
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};
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expert_module_t* sapsnc_expert;
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/* Register the protocol */
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proto_sapsnc = proto_register_protocol("SAP SNC Protocol", "SAPSNC", "sapsnc");
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proto_register_field_array(proto_sapsnc, hf, array_length(hf));
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proto_register_subtree_array(ett, array_length(ett));
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sapsnc_expert = expert_register_protocol(proto_sapsnc);
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expert_register_field_array(sapsnc_expert, ei, array_length(ei));
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register_dissector("sapsnc", dissect_sapsnc, proto_sapsnc);
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}
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/**
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* Register Hand off for the SAP SNC Protocol
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*/
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void
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proto_reg_handoff_sapsnc(void)
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{
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static gboolean initialized = FALSE;
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if (!initialized) {
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create_dissector_handle(dissect_sapsnc, proto_sapsnc);
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initialized = TRUE;
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}
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}
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/*
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* Editor modelines - https://www.wireshark.org/tools/modelines.html
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*
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* Local variables:
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* c-basic-offset: 8
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* tab-width: 8
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* indent-tabs-mode: t
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* End:
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*
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* vi: set shiftwidth=8 tabstop=8 noexpandtab:
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* :indentSize=8:tabSize=8:noTabs=false:
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*/
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