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proto: Ensure that representation strings are printable, valid UTF-8 

The proto_item_XXX_text() routines and proto_tree_add_XXX_format[_value]
functions allow dissectors to alter the representation string for
a protocol tree item with data that may come from arbitrary packet data.
These values are displayed by tshark or wireshark, so they should made
into printable, valid UTF-8.

This means that dissectors no longer need to call format_text before using
those functions (though, if they want to produce some other kind of
printable string, such as with format_text_wsp, they still can.)

Also, mark when appending and prepending text truncates a string that
was not previously truncated (except for a small number of cases where
it is difficult to determine if it was truncated before.)

Part of #18317
This commit is contained in:
John Thacker 2022-09-07 09:50:42 -04:00 committed by A Wireshark GitLab Utility
parent e5951765d8
commit a48298a93a
1 changed files with 57 additions and 17 deletions
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74
epan/proto.c
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@ -219,6 +219,7 @@ static int hfinfo_bitoffset(const header_field_info *hfinfo);
static int hfinfo_mask_bitwidth(const header_field_info *hfinfo);
static int hfinfo_container_bitwidth(const header_field_info *hfinfo);
static inline gsize label_concat(char *label_str, gsize pos, const char *str);
static void label_mark_truncated(char *label_str, gsize name_pos);
#define LABEL_MARK_TRUNCATED_START(label_str) label_mark_truncated(label_str, 0)
@ -6332,7 +6333,8 @@ proto_tree_set_representation_value(proto_item *pi, const char *format, va_list
/* If the tree (GUI) or item isn't visible it's pointless for us to generate the protocol
* items string representation */
if (PTREE_DATA(pi)->visible && !proto_item_is_hidden(pi)) {
int ret = 0;
gsize name_pos, ret = 0;
char *str, *tmp;
field_info *fi = PITEM_FINFO(pi);
header_field_info *hf;
@ -6353,22 +6355,24 @@ proto_tree_set_representation_value(proto_item *pi, const char *format, va_list
val <<= hfinfo_bitshift(hf);
p = decode_bitfield_value(fi->rep->representation, val, hf->bitmask, hfinfo_container_bitwidth(hf));
ret = (int) (p - fi->rep->representation);
ret = (p - fi->rep->representation);
}
/* put in the hf name */
ret += snprintf(fi->rep->representation + ret, ITEM_LABEL_LENGTH - ret, "%s: ", hf->name);
name_pos = ret = label_concat(fi->rep->representation, ret, hf->name);
ret = label_concat(fi->rep->representation, ret, ": ");
/* If possible, Put in the value of the string */
if (ret < ITEM_LABEL_LENGTH) {
ret += vsnprintf(fi->rep->representation + ret,
ITEM_LABEL_LENGTH - ret, format, ap);
}
str = ws_strdup_vprintf(format, ap);
tmp = format_text_string(NULL, str);
wmem_free(NULL, str);
ret = label_concat(fi->rep->representation, ret, tmp);
wmem_free(NULL, tmp);
if (ret >= ITEM_LABEL_LENGTH) {
/* Uh oh, we don't have enough room. Tell the user
* that the field is truncated.
*/
LABEL_MARK_TRUNCATED_START(fi->rep->representation);
label_mark_truncated(fi->rep->representation, name_pos);
}
}
}
@ -6379,15 +6383,20 @@ proto_tree_set_representation_value(proto_item *pi, const char *format, va_list
static void
proto_tree_set_representation(proto_item *pi, const char *format, va_list ap)
{
int ret; /*tmp return value */
gsize ret; /*tmp return value */
char *str, *tmp;
field_info *fi = PITEM_FINFO(pi);
DISSECTOR_ASSERT(fi);
if (!proto_item_is_hidden(pi)) {
ITEM_LABEL_NEW(PNODE_POOL(pi), fi->rep);
ret = vsnprintf(fi->rep->representation, ITEM_LABEL_LENGTH,
format, ap);
str = ws_strdup_vprintf(format, ap);
tmp = format_text_string(NULL, str);
wmem_free(NULL, str);
ret = label_concat(fi->rep->representation, 0, tmp);
wmem_free(NULL, tmp);
if (ret >= ITEM_LABEL_LENGTH) {
/* Uh oh, we don't have enough room. Tell the user
* that the field is truncated.
@ -7023,6 +7032,7 @@ proto_item_append_text(proto_item *pi, const char *format, ...)
{
field_info *fi = NULL;
size_t curlen;
char *str, *tmp;
va_list ap;
TRY_TO_FAKE_THIS_REPR_VOID(pi);
@ -7043,11 +7053,28 @@ proto_item_append_text(proto_item *pi, const char *format, ...)
}
curlen = strlen(fi->rep->representation);
if (ITEM_LABEL_LENGTH > curlen) {
/* curlen doesn't include the \0 byte.
* XXX: If curlen + 4 > ITEM_LABEL_LENGTH, we can't tell if
* the representation has already been truncated (of an up
* to 4 byte UTF-8 character) or is just at the maximum length
* unless we search for " [truncated]" (which may not be
* at the start.)
* It's safer to do nothing.
*/
if (ITEM_LABEL_LENGTH > (curlen + 4)) {
va_start(ap, format);
vsnprintf(fi->rep->representation + curlen,
ITEM_LABEL_LENGTH - (gulong) curlen, format, ap);
str = ws_strdup_vprintf(format, ap);
va_end(ap);
tmp = format_text_string(NULL, str);
wmem_free(NULL, str);
curlen = label_concat(fi->rep->representation, curlen, tmp);
wmem_free(NULL, tmp);
if (curlen >= ITEM_LABEL_LENGTH) {
/* Uh oh, we don't have enough room. Tell the user
* that the field is truncated.
*/
LABEL_MARK_TRUNCATED_START(fi->rep->representation);
}
}
}
}
@ -7057,7 +7084,9 @@ void
proto_item_prepend_text(proto_item *pi, const char *format, ...)
{
field_info *fi = NULL;
gsize pos;
char representation[ITEM_LABEL_LENGTH];
char *str, *tmp;
va_list ap;
TRY_TO_FAKE_THIS_REPR_VOID(pi);
@ -7079,10 +7108,21 @@ proto_item_prepend_text(proto_item *pi, const char *format, ...)
(void) g_strlcpy(representation, fi->rep->representation, ITEM_LABEL_LENGTH);
va_start(ap, format);
vsnprintf(fi->rep->representation,
ITEM_LABEL_LENGTH, format, ap);
str = ws_strdup_vprintf(format, ap);
va_end(ap);
(void) g_strlcat(fi->rep->representation, representation, ITEM_LABEL_LENGTH);
tmp = format_text_string(NULL, str);
wmem_free(NULL, str);
pos = label_concat(fi->rep->representation, 0, tmp);
wmem_free(NULL, tmp);
pos = label_concat(fi->rep->representation, pos, representation);
/* XXX: As above, if the old representation is close to the label
* length, it might already be marked as truncated. */
if (pos >= ITEM_LABEL_LENGTH && (strlen(representation) + 4) <= ITEM_LABEL_LENGTH) {
/* Uh oh, we don't have enough room. Tell the user
* that the field is truncated.
*/
LABEL_MARK_TRUNCATED_START(fi->rep->representation);
}
}
}