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/* packet-gpef.c
* Routines for dissection of Group Policy : Encrypted File System Extension
* Described in Microsoft document MS-GPEF.pdf
* Copyright 2008, Ronnie Sahlberg
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include "packet-windows-common.h"
#include <epan/asn1.h>
#include "packet-x509af.h"
void proto_register_gpef(void);
static int proto_gpef = -1;
static int hf_gpef_keycount = -1;
static int hf_gpef_efskey = -1;
static int hf_gpef_efskey_length1 = -1;
static int hf_gpef_efskey_length2 = -1;
static int hf_gpef_efskey_sid_offset = -1;
static int hf_gpef_efskey_cert_offset = -1;
static int hf_gpef_efskey_cert_length = -1;
static int hf_gpef_efskey_certificate = -1;
static gint ett_gpef = -1;
static gint ett_gpef_efskey = -1;
/* MS-GPEF section 2.2.1.2.2 EfsKey*/
static int
dissect_gpef_efskey(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *parent_tree)
{
proto_item *item = NULL;
proto_tree *tree = NULL;
int old_offset = offset;
guint32 length1, sid_offset;
guint32 cert_length, cert_offset;
tvbuff_t *next_tvb;
asn1_ctx_t asn1_ctx;
asn1_ctx_init(&asn1_ctx, ASN1_ENC_BER, TRUE, pinfo);
if (parent_tree) {
item = proto_tree_add_item(parent_tree, hf_gpef_efskey, tvb, -1, -1, ENC_NA);
tree = proto_item_add_subtree(item, ett_gpef_efskey);
}
/* length 1 */
length1 = tvb_get_letohl(tvb, offset);
proto_tree_add_item(tree, hf_gpef_efskey_length1, tvb, offset, 4, ENC_LITTLE_ENDIAN);
offset += 4;
/* length 2 */
proto_tree_add_item(tree, hf_gpef_efskey_length2, tvb, offset, 4, ENC_LITTLE_ENDIAN);
offset += 4;
/* sid offset */
sid_offset = tvb_get_letohl(tvb, offset);
proto_tree_add_item(tree, hf_gpef_efskey_sid_offset, tvb, offset, 4, ENC_LITTLE_ENDIAN);
offset += 4;
/* reserved */
offset += 4;
/* cert length */
cert_length = tvb_get_letohl(tvb, offset);
proto_tree_add_item(tree, hf_gpef_efskey_cert_length, tvb, offset, 4, ENC_LITTLE_ENDIAN);
offset += 4;
/* cert offset */
cert_offset = tvb_get_letohl(tvb, offset);
proto_tree_add_item(tree, hf_gpef_efskey_cert_offset, tvb, offset, 4, ENC_LITTLE_ENDIAN);
/*offset += 4;*/
/* reserved, must be 0x20 0x00 0x00 0x00 */
/*offset += 4;*/
/* sid */
dissect_nt_sid(tvb, old_offset+4+sid_offset, tree, "sid", NULL, -1);
/* certificate */
next_tvb = tvb_new_subset_length(tvb, old_offset+4+cert_offset, cert_length);
(void)dissect_x509af_Certificate(FALSE, next_tvb, 0, &asn1_ctx, tree, hf_gpef_efskey_certificate);
offset = old_offset + length1;
proto_item_set_len(item, offset-old_offset);
return offset;
}
/* MS-GPEF section 2.2.1.2.1 */
static int
dissect_gpef_efsblob(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void *data _U_)
{
int offset = 0;
proto_tree *tree;
proto_item *item;
guint32 count;
item = proto_tree_add_item(parent_tree, proto_gpef, tvb, 0, -1, ENC_NA);
tree = proto_item_add_subtree(item, ett_gpef);
/* reserved, must be 0x01 0x00 0x01 0x00 */
offset += 4;
/* key count */
count = tvb_get_letohl(tvb, offset);
proto_tree_add_item(tree, hf_gpef_keycount, tvb, offset, 4, ENC_LITTLE_ENDIAN);
offset += 4;
while (count--) {
offset = dissect_gpef_efskey(tvb, offset, pinfo, tree);
}
return offset;
}
void
proto_register_gpef(void)
{
static hf_register_info hf[] = {
{ &hf_gpef_keycount,
{ "Key Count", "gpef.key_count", FT_UINT32, BASE_DEC, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey_length1,
{ "Length1", "gpef.efskey.length1", FT_UINT32, BASE_DEC, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey_length2,
{ "Length2", "gpef.efskey.length2", FT_UINT32, BASE_DEC, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey_sid_offset,
{ "SID Offset", "gpef.efskey.sid_offset", FT_UINT32, BASE_DEC, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey_cert_offset,
{ "Cert Offset", "gpef.efskey.cert_offset", FT_UINT32, BASE_DEC, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey_cert_length,
{ "Cert Length", "gpef.efskey.cert_length", FT_UINT32, BASE_DEC, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey,
{ "EfsKey", "gpef.efskey", FT_NONE, BASE_NONE, NULL,
0x0, NULL, HFILL }},
{ &hf_gpef_efskey_certificate,
{ "Certificate", "gpef.efskey.certificate", FT_NONE, BASE_NONE, NULL,
0x0, NULL, HFILL }},
};
static gint *ett[] = {
&ett_gpef,
&ett_gpef_efskey,
};
proto_gpef = proto_register_protocol("GPEF", "GPEF", "gpef");
proto_register_field_array(proto_gpef, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
register_dissector("efsblob", dissect_gpef_efsblob, proto_gpef);
}
/*
* 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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