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RTPS: string dissection, unicode improvements 

Add a local function `rtps_strlcpy()` which ensures its destination is
truncated on a clean unicode character boundary. Use this function for
getting the rtps type and topic names, where #19359 was triggered.
(Function may also be useful elsewhere in this dissector, but I'm
leaving that for other devs in order to reduce gold plating.)

Tweak `rtps_util_add_string()` to explicitly dissect the field
containing the string's length to make overall dissection more explicit.
Also rework `tvb_get_string_enc()`+`proto_tree_add_string()` to
`proto_tree_add_item()`.
This commit is contained in:
David Perry 2023-10-24 16:51:44 -04:00 committed by AndersBroman
parent e21f61ed70
commit a35aa997ad
1 changed files with 28 additions and 7 deletions
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35
epan/dissectors/packet-rtps.c
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@ -55,6 +55,7 @@
#include "zlib.h"
#include <epan/crc32-tvb.h>
#include <wsutil/crc32.h>
#include <wsutil/str_util.h>
#include <gcrypt.h>
void proto_register_rtps(void);
@ -915,6 +916,7 @@ static int hf_rtps_parameter_id_toc = -1;
static int hf_rtps_parameter_id_rti = -1;
static int hf_rtps_parameter_id_adl = -1;
static int hf_rtps_parameter_length = -1;
static int hf_rtps_string_length = -1;
static int hf_rtps_coherent_set_start = -1;
static int hf_rtps_coherent_set_end = -1;
static int hf_rtps_param_topic_name = -1;
@ -2803,6 +2805,13 @@ static const fragment_items rtps_frag_items = {
static const true_false_string tfs_little_big_endianness = { "Little-Endian", "Big-Endian" };
/* #19359 - ensure strings we copy aren't truncated halfway through a Unicode codepoint */
static void rtps_strlcpy(char *dest, const char *src, size_t dest_size)
{
(void) g_strlcpy(dest, src, dest_size);
ws_utf8_truncate(dest, dest_size);
}
static gint check_offset_addition(gint offset, guint32 value, proto_tree *tree, packet_info *pinfo, tvbuff_t *tvb)
{
gint new_offset = offset + (gint)value;
@ -4477,15 +4486,15 @@ static void rtps_util_add_generic_guid_v1(proto_tree *tree, tvbuff_t *tvb, gint
/* ------------------------------------------------------------------------- */
/* Insert in the protocol tree the next data interpreted as a String
* Returns the new offset (after reading the string)
* XXX - should check that string length field makes sense, possibly by
* comparing to a passed-in container length (cf. #19359)
*/
static gint rtps_util_add_string(proto_tree *tree, tvbuff_t *tvb, gint offset,
int hf_item, const guint encoding) {
guint8 *retVal = NULL;
guint32 size = tvb_get_guint32(tvb, offset, encoding);
guint32 size;
retVal = tvb_get_string_enc(wmem_packet_scope(), tvb, offset+4, size, ENC_ASCII);
proto_tree_add_string(tree, hf_item, tvb, offset, size+4, retVal);
proto_tree_add_item_ret_uint(tree, hf_rtps_string_length, tvb, offset, 4, encoding, &size);
proto_tree_add_item(tree, hf_item, tvb, offset+4, size, ENC_ASCII);
/* NDDS align strings at 4-bytes word. So:
* string_length: 4 -> buffer_length = 4;
@ -6464,13 +6473,13 @@ static void rtps_util_store_type_mapping(packet_info *pinfo _U_, tvbuff_t *tvb,
break;
}
case TOPIC_INFO_ADD_TOPIC_NAME: {
(void) g_strlcpy(type_mapping_object->topic_name, value, MAX_TOPIC_AND_TYPE_LENGTH);
rtps_strlcpy(type_mapping_object->topic_name, value, MAX_TOPIC_AND_TYPE_LENGTH);
type_mapping_object->fields_visited =
type_mapping_object->fields_visited | TOPIC_INFO_ADD_TOPIC_NAME;
break;
}
case TOPIC_INFO_ADD_TYPE_NAME: {
(void) g_strlcpy(type_mapping_object->type_name, value, MAX_TOPIC_AND_TYPE_LENGTH);
rtps_strlcpy(type_mapping_object->type_name, value, MAX_TOPIC_AND_TYPE_LENGTH);
type_mapping_object->fields_visited =
type_mapping_object->fields_visited | TOPIC_INFO_ADD_TYPE_NAME;
break;
@ -14776,6 +14785,18 @@ void proto_register_rtps(void) {
HFILL }
},
/* String Length ---------------------------------------------------- */
{ &hf_rtps_string_length, {
"String length",
"rtps.param.string.length",
FT_UINT32,
BASE_DEC,
NULL,
0,
NULL,
HFILL }
},
/* Parameter / Topic --------------------------------------------------- */
{ &hf_rtps_param_topic_name, {
"topic",