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/* packet-bencode.c
* Routines for bencode dissection
* Copyright (C) 2004,2013 Jelmer Vernooij <jelmer@samba.org>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* Copied from packet-pop.c
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/expert.h>
#include <epan/strutil.h>
void proto_register_bencode(void);
static int proto_bencode;
static int hf_bencode_str_length;
static int hf_bencode_str;
static int hf_bencode_int;
static int hf_bencode_dict;
static int hf_bencode_dict_entry;
static int hf_bencode_list;
static int hf_bencode_truncated_data;
static int ett_bencode_dict;
static int ett_bencode_dict_entry;
static int ett_bencode_list;
static expert_field ei_bencode_str;
static expert_field ei_bencode_str_length;
static expert_field ei_bencode_int;
static expert_field ei_bencode_nest;
static expert_field ei_bencode_dict_key;
static expert_field ei_bencode_dict_value;
static expert_field ei_bencode_invalid;
static int dissect_bencoding_str(tvbuff_t *tvb, packet_info *pinfo,
int offset, int length, proto_tree *tree, proto_item *ti, int treeadd)
{
uint8_t ch;
int stringlen = 0, nextstringlen;
int used;
int izero = 0;
if (length < 2) {
proto_tree_add_expert(tree, pinfo, &ei_bencode_str, tvb, offset, length);
return -1;
}
used = 0;
while (length >= 1) {
ch = tvb_get_uint8(tvb, offset + used);
length--;
used++;
if ((ch == ':') && (used > 1)) {
if ((stringlen > length) || (stringlen < 0)) {
proto_tree_add_expert(tree, pinfo, &ei_bencode_str_length, tvb, offset, length);
return -1;
}
if (tree) {
proto_tree_add_uint(tree, hf_bencode_str_length, tvb, offset, used, stringlen);
proto_tree_add_item(tree, hf_bencode_str, tvb, offset + used, stringlen, ENC_ASCII);
if (treeadd == 1) {
proto_item_append_text(ti, " Key: %s",
tvb_format_text(pinfo->pool, tvb, offset + used, stringlen));
}
if (treeadd == 2) {
proto_item_append_text(ti, " Value: %s",
tvb_format_text(pinfo->pool, tvb, offset + used, stringlen));
}
}
return used + stringlen;
}
if (!izero && (ch >= '0') && (ch <= '9')) {
if ((ch == '0') && (used == 1)) {
izero = 1;
}
nextstringlen = (stringlen * 10) + (ch - '0');
if (nextstringlen >= stringlen) {
stringlen = nextstringlen;
continue;
}
}
proto_tree_add_expert(tree, pinfo, &ei_bencode_str, tvb, offset, length);
return -1;
}
proto_tree_add_item(tree, hf_bencode_truncated_data, tvb, offset, length, ENC_NA);
return -1;
}
static int dissect_bencoding_int(tvbuff_t *tvb, packet_info *pinfo,
int offset, int length, proto_tree *tree, proto_item *ti, int treeadd)
{
int32_t ival = 0;
int neg = 0;
int izero = 0;
int used;
uint8_t ch;
if (length<3) {
proto_tree_add_expert(tree, pinfo, &ei_bencode_int, tvb, offset, length);
return -1;
}
length--;
used = 1;
while (length >= 1) {
ch = tvb_get_uint8(tvb, offset + used);
length--;
used++;
switch (ch) {
case 'e':
if (tree) {
if (neg) ival = -ival;
proto_tree_add_int(tree, hf_bencode_int, tvb, offset, used, ival);
if (treeadd == 2) {
proto_item_append_text(ti, " Value: %d", ival);
}
}
return used;
case '-':
if (used == 2) {
neg = 1;
break;
}
/* Fall through */
default:
if (!((ch == '0') && (used == 3) && neg)) { /* -0 is invalid */
if ((ch == '0') && (used == 2)) { /* as is 0[0-9]+ */
izero = 1;
break;
}
if (!izero && (ch >= '0') && (ch <= '9')) {
ival = (ival * 10) + (ch - '0');
break;
}
}
proto_tree_add_expert(tree, pinfo, &ei_bencode_int, tvb, offset, length);
return -1;
}
}
proto_tree_add_item(tree, hf_bencode_truncated_data, tvb, offset, length, ENC_NA);
return -1;
}
// NOLINTNEXTLINE(misc-no-recursion)
static int dissect_bencoding_rec(tvbuff_t *tvb, packet_info *pinfo,
int offset, int length, proto_tree *tree, int level, proto_item *treei, int treeadd)
{
uint8_t op;
int oplen = 0, op1len, op2len;
int used;
proto_item *ti = NULL, *td = NULL;
proto_tree *itree = NULL, *dtree = NULL;
if (level > 10) {
proto_tree_add_expert(tree, pinfo, &ei_bencode_nest, tvb, offset, -1);
return -1;
}
if (length < 1) {
proto_tree_add_item(tree, hf_bencode_truncated_data, tvb, offset, -1, ENC_NA);
return length;
}
op = tvb_get_uint8(tvb, offset);
oplen = length;
switch (op) {
case 'd':
td = proto_tree_add_item(tree, hf_bencode_dict, tvb, offset, oplen, ENC_NA);
dtree = proto_item_add_subtree(td, ett_bencode_dict);
used = 1;
length--;
while (length >= 1) {
op = tvb_get_uint8(tvb, offset + used);
if (op == 'e') {
return used + 1;
}
op1len = dissect_bencoding_str(tvb, pinfo, offset + used, length, NULL, NULL, 0);
if (op1len < 0) {
proto_tree_add_expert(dtree, pinfo, &ei_bencode_dict_key, tvb, offset + used, -1);
return op1len;
}
op2len = -1;
if ((length - op1len) > 2) {
increment_dissection_depth(pinfo);
op2len = dissect_bencoding_rec(tvb, pinfo, offset + used + op1len, length - op1len, NULL, level + 1, NULL, 0);
decrement_dissection_depth(pinfo);
}
if (op2len < 0) {
proto_tree_add_expert(dtree, pinfo, &ei_bencode_dict_value, tvb, offset + used + op1len, -1);
return op2len;
}
ti = proto_tree_add_item(dtree, hf_bencode_dict_entry, tvb, offset + used, op1len + op2len, ENC_NA);
itree = proto_item_add_subtree(ti, ett_bencode_dict_entry);
dissect_bencoding_str(tvb, pinfo, offset + used, length, itree, ti, 1);
increment_dissection_depth(pinfo);
dissect_bencoding_rec(tvb, pinfo, offset + used + op1len, length - op1len, itree, level + 1, ti, 2);
decrement_dissection_depth(pinfo);
used += op1len + op2len;
length -= op1len + op2len;
}
proto_tree_add_item(dtree, hf_bencode_truncated_data, tvb, offset + used, length ? -1 : 0, ENC_NA);
return -1;
case 'l':
ti = proto_tree_add_item(tree, hf_bencode_list, tvb, offset, oplen, ENC_NA);
itree = proto_item_add_subtree(ti, ett_bencode_list);
used = 1;
length--;
increment_dissection_depth(pinfo);
while (length >= 1) {
op = tvb_get_uint8(tvb, offset + used);
if (op == 'e') {
return used + 1;
}
oplen = dissect_bencoding_rec(tvb, pinfo, offset + used, length, itree, level + 1, ti, 0);
if (oplen < 1) {
decrement_dissection_depth(pinfo);
return oplen;
}
used += oplen;
length -= oplen;
}
decrement_dissection_depth(pinfo);
proto_tree_add_item(itree, hf_bencode_truncated_data, tvb, offset + used, -1, ENC_NA);
return -1;
case 'i':
return dissect_bencoding_int(tvb, pinfo, offset, length, tree, treei, treeadd);
default:
if ((op >= '1') && (op <= '9')) {
return dissect_bencoding_str(tvb, pinfo, offset, length, tree, treei, treeadd);
}
proto_tree_add_expert(tree, pinfo, &ei_bencode_invalid, tvb, offset, -1);
}
return -1;
}
static int dissect_bencoding(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
{
dissect_bencoding_rec(tvb, pinfo, 0, tvb_reported_length(tvb), tree, 0, NULL, 0);
return tvb_captured_length(tvb);
}
void
proto_register_bencode(void)
{
static hf_register_info hf[] = {
{ &hf_bencode_str_length,
{ "String Length", "bencode.str.length", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL }
},
{ &hf_bencode_str,
{ "String", "bencode.str", FT_STRING, BASE_NONE, NULL, 0x0, NULL, HFILL }
},
{ &hf_bencode_int,
{ "Integer", "bencode.int", FT_INT32, BASE_DEC, NULL, 0x0, NULL, HFILL }
},
{ &hf_bencode_dict,
{ "Dictionary", "bencode.dict", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }
},
{ &hf_bencode_dict_entry,
{ "Entry", "bencode.dict.entry", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }
},
{ &hf_bencode_list,
{ "List", "bencode.list", FT_NONE, BASE_NONE, NULL, 0x0, NULL, HFILL }
},
{ &hf_bencode_truncated_data,
{ "Truncated Data", "bencode.truncated_data", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL }
},
};
static int *ett[] = {
&ett_bencode_dict,
&ett_bencode_dict_entry,
&ett_bencode_list,
};
static ei_register_info ei[] = {
{ &ei_bencode_str, { "bencode.str.invalid", PI_MALFORMED, PI_ERROR, "Decode Aborted: Invalid String", EXPFILL }},
{ &ei_bencode_str_length, { "bencode.str.length.invalid", PI_MALFORMED, PI_ERROR, "Decode Aborted: Invalid String Length", EXPFILL }},
{ &ei_bencode_int, { "bencode.int.invalid", PI_MALFORMED, PI_ERROR, "Decode Aborted: Invalid Integer", EXPFILL }},
{ &ei_bencode_nest, { "bencode.nest", PI_MALFORMED, PI_ERROR, "Decode Aborted: Nested Too Deep", EXPFILL }},
{ &ei_bencode_dict_key, { "bencode.dict.key_invalid", PI_MALFORMED, PI_ERROR, "Decode Aborted: Invalid Dictionary Key", EXPFILL }},
{ &ei_bencode_dict_value, { "bencode.dict.value_invalid", PI_MALFORMED, PI_ERROR, "Decode Aborted: Invalid Dictionary Value", EXPFILL }},
{ &ei_bencode_invalid, { "bencode.invalid", PI_MALFORMED, PI_ERROR, "Invalid Bencoding", EXPFILL }},
};
expert_module_t* expert_bencode;
proto_bencode = proto_register_protocol("Bencode", "Bencode", "bencode");
register_dissector("bencode", dissect_bencoding, proto_bencode);
proto_register_field_array(proto_bencode, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
expert_bencode = expert_register_protocol(proto_bencode);
expert_register_field_array(expert_bencode, ei, array_length(ei));
}
/*
* Editor modelines - https://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 3
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=3 tabstop=8 expandtab:
* :indentSize=3:tabSize=8:noTabs=true:
*/
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