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