Initial commit
This commit is contained in:
@@ -0,0 +1,106 @@
|
||||
From 257ac0c5f7732cbc6aa96fdd3b06602234593aca Mon Sep 17 00:00:00 2001
|
||||
From: Simon Kelley <simon@thekelleys.org.uk>
|
||||
Date: Thu, 12 Nov 2020 18:49:23 +0000
|
||||
Subject: Check destination of DNS UDP query replies.
|
||||
|
||||
At any time, dnsmasq will have a set of sockets open, bound to
|
||||
random ports, on which it sends queries to upstream nameservers.
|
||||
This patch fixes the existing problem that a reply for ANY in-flight
|
||||
query would be accepted via ANY open port, which increases the
|
||||
chances of an attacker flooding answers "in the blind" in an
|
||||
attempt to poison the DNS cache. CERT VU#434904 refers.
|
||||
---
|
||||
CHANGELOG | 6 +++++-
|
||||
src/forward.c | 37 ++++++++++++++++++++++++++++---------
|
||||
2 files changed, 33 insertions(+), 10 deletions(-)
|
||||
|
||||
--- a/CHANGELOG
|
||||
+++ b/CHANGELOG
|
||||
@@ -2,8 +2,12 @@
|
||||
dnsmasq with DNSSEC compiled in and enabled is vulnerable to this,
|
||||
referenced by CERT VU#434904.
|
||||
|
||||
+ Be sure to only accept UDP DNS query replies at the address
|
||||
+ from which the query was originated. This keeps as much entropy
|
||||
+ in the {query-ID, random-port} tuple as possible, help defeat
|
||||
+ cache poisoning attacks. Refer: CERT VU#434904.
|
||||
+
|
||||
|
||||
->>>>>>> Fix remote buffer overflow CERT VU#434904
|
||||
version 2.81
|
||||
Impove cache behaviour for TCP connections. For ease of
|
||||
implementaion, dnsmasq has always forked a new process to handle
|
||||
--- a/src/forward.c
|
||||
+++ b/src/forward.c
|
||||
@@ -16,7 +16,7 @@
|
||||
|
||||
#include "dnsmasq.h"
|
||||
|
||||
-static struct frec *lookup_frec(unsigned short id, void *hash);
|
||||
+static struct frec *lookup_frec(unsigned short id, int fd, int family, void *hash);
|
||||
static struct frec *lookup_frec_by_sender(unsigned short id,
|
||||
union mysockaddr *addr,
|
||||
void *hash);
|
||||
@@ -797,7 +797,7 @@ void reply_query(int fd, int family, tim
|
||||
crc = questions_crc(header, n, daemon->namebuff);
|
||||
#endif
|
||||
|
||||
- if (!(forward = lookup_frec(ntohs(header->id), hash)))
|
||||
+ if (!(forward = lookup_frec(ntohs(header->id), fd, family, hash)))
|
||||
return;
|
||||
|
||||
#ifdef HAVE_DUMPFILE
|
||||
@@ -2289,14 +2289,25 @@ struct frec *get_new_frec(time_t now, in
|
||||
}
|
||||
|
||||
/* crc is all-ones if not known. */
|
||||
-static struct frec *lookup_frec(unsigned short id, void *hash)
|
||||
+static struct frec *lookup_frec(unsigned short id, int fd, int family, void *hash)
|
||||
{
|
||||
struct frec *f;
|
||||
|
||||
for(f = daemon->frec_list; f; f = f->next)
|
||||
if (f->sentto && f->new_id == id &&
|
||||
(!hash || memcmp(hash, f->hash, HASH_SIZE) == 0))
|
||||
- return f;
|
||||
+ {
|
||||
+ /* sent from random port */
|
||||
+ if (family == AF_INET && f->rfd4 && f->rfd4->fd == fd)
|
||||
+ return f;
|
||||
+
|
||||
+ if (family == AF_INET6 && f->rfd6 && f->rfd6->fd == fd)
|
||||
+ return f;
|
||||
+
|
||||
+ /* sent to upstream from bound socket. */
|
||||
+ if (f->sentto->sfd && f->sentto->sfd->fd == fd)
|
||||
+ return f;
|
||||
+ }
|
||||
|
||||
return NULL;
|
||||
}
|
||||
@@ -2357,12 +2368,20 @@ void server_gone(struct server *server)
|
||||
static unsigned short get_id(void)
|
||||
{
|
||||
unsigned short ret = 0;
|
||||
+ struct frec *f;
|
||||
|
||||
- do
|
||||
- ret = rand16();
|
||||
- while (lookup_frec(ret, NULL));
|
||||
-
|
||||
- return ret;
|
||||
+ while (1)
|
||||
+ {
|
||||
+ ret = rand16();
|
||||
+
|
||||
+ /* ensure id is unique. */
|
||||
+ for (f = daemon->frec_list; f; f = f->next)
|
||||
+ if (f->sentto && f->new_id == ret)
|
||||
+ break;
|
||||
+
|
||||
+ if (!f)
|
||||
+ return ret;
|
||||
+ }
|
||||
}
|
||||
|
||||
|
||||
Reference in New Issue
Block a user