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Fix bug in 0x20 encoding.

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We must only compare case when mapping an answer from upstream
to a forwarding record, not when checking a query to see if it's a
duplicate. Since the saved query name is scrambled, that ensures
that almost all such checks will wrongly fail.

Thanks to Peter Tirsek for an exemplary bug report for this.
This commit is contained in:
Simon Kelley
2025-02-06 10:32:29 +00:00
parent a1a214c393
commit e44165c0f7
2 changed files with 13 additions and 2 deletions
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1
src/dnsmasq.h
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@@ -775,6 +775,7 @@ struct dyndir {
#define FREC_DO_QUESTION 64 #define FREC_DO_QUESTION 64
#define FREC_HAS_PHEADER 128 #define FREC_HAS_PHEADER 128
#define FREC_GONE_TO_TCP 256 #define FREC_GONE_TO_TCP 256
#define FREC_ANSWER 512
struct frec { struct frec {
struct frec_src { struct frec_src {

14
src/forward.c
View File

@@ -1098,7 +1098,7 @@ void reply_query(int fd, time_t now)
GETSHORT(rrtype, p); GETSHORT(rrtype, p);
GETSHORT(class, p); GETSHORT(class, p);
if (!(forward = lookup_frec(daemon->namebuff, class, rrtype, ntohs(header->id), 0, 0))) if (!(forward = lookup_frec(daemon->namebuff, class, rrtype, ntohs(header->id), FREC_ANSWER, 0)))
return; return;
filter_servers(forward->sentto->arrayposn, F_SERVER, &first, &last); filter_servers(forward->sentto->arrayposn, F_SERVER, &first, &last);
@@ -3057,6 +3057,16 @@ static struct frec *lookup_frec(char *target, int class, int rrtype, int id, int
{ {
struct frec *f; struct frec *f;
struct dns_header *header; struct dns_header *header;
int compare_mode = EXTR_NAME_COMPARE;
/* Only compare case-sensitive when matching frec to a an recieved anwer,
not when looking for a duplicated question. */
if (flags & FREC_ANSWER)
{
flags &= ~FREC_ANSWER;
if (!option_bool(OPT_NO_0x20))
compare_mode = EXTR_NAME_NOCASE;
}
for (f = daemon->frec_list; f; f = f->next) for (f = daemon->frec_list; f; f = f->next)
if (f->sentto && if (f->sentto &&
@@ -3068,7 +3078,7 @@ static struct frec *lookup_frec(char *target, int class, int rrtype, int id, int
int hclass, hrrtype, rc; int hclass, hrrtype, rc;
/* Case sensitive compare for DNS-0x20 encoding. */ /* Case sensitive compare for DNS-0x20 encoding. */
if ((rc = extract_name(header, f->stash_len, &p, target, option_bool(OPT_NO_0x20) ? EXTR_NAME_COMPARE : EXTR_NAME_NOCASE, 4))) if ((rc = extract_name(header, f->stash_len, &p, target, compare_mode, 4)))
{ {
GETSHORT(hrrtype, p); GETSHORT(hrrtype, p);
GETSHORT(hclass, p); GETSHORT(hclass, p);