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gthreadedresolver: Handle error returns from dn_expand() in headers

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It is possible for `dn_expand()` to fail; if so, it’ll return `-1`,
which will mess up subsequent parsing.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This commit is contained in:
Philip Withnall 2022-03-18 15:51:20 +00:00
parent 263ca69da8
commit 8b73d7bbf9
1 changed files with 30 additions and 3 deletions
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33
gio/gthreadedresolver.c
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@ -712,8 +712,22 @@ g_resolver_records_from_res_query (const gchar *rrname,
count = ntohs (header->qdcount);
while (count-- && p < end)
{
p += dn_expand (answer, end, p, namebuf, sizeof (namebuf));
p += 4;
int expand_result;
expand_result = dn_expand (answer, end, p, namebuf, sizeof (namebuf));
if (expand_result < 0 || end - p < expand_result + 4)
{
/* Not possible to recover parsing as the length of the rest of the
* record is unknown or is too short. */
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
/* Translators: the first placeholder is a domain name, the
* second is an error message */
_("Error resolving “%s”: %s"), rrname, _("Malformed DNS packet"));
return NULL;
}
p += expand_result;
p += 4; /* skip TYPE and CLASS */
/* To silence gcc warnings */
namebuf[0] = namebuf[1];
@ -723,7 +737,20 @@ g_resolver_records_from_res_query (const gchar *rrname,
count = ntohs (header->ancount);
while (count-- && p < end)
{
p += dn_expand (answer, end, p, namebuf, sizeof (namebuf));
int expand_result;
expand_result = dn_expand (answer, end, p, namebuf, sizeof (namebuf));
if (expand_result < 0 || end - p < expand_result + 10)
{
/* Not possible to recover parsing as the length of the rest of the
* record is unknown or is too short. */
g_set_error (error, G_RESOLVER_ERROR, G_RESOLVER_ERROR_INTERNAL,
_("Error resolving “%s”"), rrname);
g_list_free_full (records, (GDestroyNotify) g_variant_unref);
return NULL;
}
p += expand_result;
GETSHORT (type, p);
GETSHORT (qclass, p);
p += 4; /* ignore the ttl (type=long) value */