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From a337a1ba7d15853fb56deef1f464529af6e3a1cf Mon Sep 17 00:00:00 2001
From: Evgeny Vereshchagin <evvers@ya.ru>
Date: Mon, 23 Oct 2023 20:29:31 +0000
Subject: [PATCH 1/2] core: reject overly long TXT resource records
Closes https://github.com/lathiat/avahi/issues/455
CVE-2023-38469
---
avahi-core/rr.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/avahi-core/rr.c b/avahi-core/rr.c
index 2bb89244..9c04ebbd 100644
--- a/avahi-core/rr.c
+++ b/avahi-core/rr.c
@@ -32,6 +32,7 @@
#include <avahi-common/malloc.h>
#include <avahi-common/defs.h>
+#include "dns.h"
#include "rr.h"
#include "log.h"
#include "util.h"
@@ -689,11 +690,17 @@ int avahi_record_is_valid(AvahiRecord *r) {
case AVAHI_DNS_TYPE_TXT: {
AvahiStringList *strlst;
+ size_t used = 0;
- for (strlst = r->data.txt.string_list; strlst; strlst = strlst->next)
+ for (strlst = r->data.txt.string_list; strlst; strlst = strlst->next) {
if (strlst->size > 255 || strlst->size <= 0)
return 0;
+ used += 1+strlst->size;
+ if (used > AVAHI_DNS_RDATA_MAX)
+ return 0;
+ }
+
return 1;
}
}
From c6cab87df290448a63323c8ca759baa516166237 Mon Sep 17 00:00:00 2001
From: Evgeny Vereshchagin <evvers@ya.ru>
Date: Wed, 25 Oct 2023 18:15:42 +0000
Subject: [PATCH 2/2] tests: pass overly long TXT resource records
to make sure they don't crash avahi any more.
It reproduces https://github.com/lathiat/avahi/issues/455
---
avahi-client/client-test.c | 14 ++++++++++++++
2 files changed, 20 insertions(+)
diff --git a/avahi-client/client-test.c b/avahi-client/client-test.c
index ba979988..da0e43ad 100644
--- a/avahi-client/client-test.c
+++ b/avahi-client/client-test.c
@@ -22,6 +22,7 @@
#endif
#include <stdio.h>
+#include <string.h>
#include <assert.h>
#include <avahi-client/client.h>
@@ -33,6 +34,8 @@
#include <avahi-common/malloc.h>
#include <avahi-common/timeval.h>
+#include <avahi-core/dns.h>
+
static const AvahiPoll *poll_api = NULL;
static AvahiSimplePoll *simple_poll = NULL;
@@ -222,6 +225,9 @@ int main (AVAHI_GCC_UNUSED int argc, AVAHI_GCC_UNUSED char *argv[]) {
uint32_t cookie;
struct timeval tv;
AvahiAddress a;
+ uint8_t rdata[AVAHI_DNS_RDATA_MAX+1];
+ AvahiStringList *txt = NULL;
+ int r;
simple_poll = avahi_simple_poll_new();
poll_api = avahi_simple_poll_get(simple_poll);
@@ -261,6 +267,14 @@ int main (AVAHI_GCC_UNUSED int argc, AVAHI_GCC_UNUSED char *argv[]) {
error = avahi_entry_group_add_record (group, AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC, 0, "TestX", 0x01, 0x10, 120, "", 0);
assert(error != AVAHI_OK);
+ memset(rdata, 1, sizeof(rdata));
+ r = avahi_string_list_parse(rdata, sizeof(rdata), &txt);
+ assert(r >= 0);
+ assert(avahi_string_list_serialize(txt, NULL, 0) == sizeof(rdata));
+ error = avahi_entry_group_add_service_strlst(group, AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC, 0, "TestX", "_qotd._tcp", NULL, NULL, 123, txt);
+ assert(error == AVAHI_ERR_INVALID_RECORD);
+ avahi_string_list_free(txt);
+
avahi_entry_group_commit (group);
domain = avahi_domain_browser_new (avahi, AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC, NULL, AVAHI_DOMAIN_BROWSER_BROWSE, 0, avahi_domain_browser_callback, (char*) "omghai3u");
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