CVE-2016-2088
Backport commit d7ff9a1c41bf0ba9773cb3adb08b48b9fd57c956 from the
v9_10_3_patch branch.
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-2088
https://kb.isc.org/article/AA-01351
CVE: CVE-2016-2088
Upstream-Status: Backport
Signed-off-by: Jussi Kukkonen <jussi.kukkonen@intel.com>
Original commit message from Mark Andrews <marka@isc.org> below:
4322. [security] Duplicate EDNS COOKIE options in a response could
trigger an assertion failure. (CVE-2016-2088)
[RT #41809]
(cherry picked from commit 455c0848f80a8acda27aad1466c72987cafaa029)
(cherry picked from commit 7cd300abd6ee8b8ee8730593daf742ba53f90bc3)
---
CHANGES | 4 ++++
bin/dig/dighost.c | 9 +++++++++
bin/named/client.c | 33 +++++++++++++++++++++++----------
doc/arm/notes.xml | 7 +++++++
lib/dns/resolver.c | 14 +++++++++++++-
5 files changed, 56 insertions(+), 11 deletions(-)
diff --git a/CHANGES b/CHANGES
index c5b5d2b..d2e3360 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+4322. [security] Duplicate EDNS COOKIE options in a response could
+ trigger an assertion failure. (CVE-2016-2088)
+ [RT #41809]
+
4319. [security] Fix resolver assertion failure due to improper
DNAME handling when parsing fetch reply messages.
(CVE-2016-1286) [RT #41753]
diff --git a/bin/dig/dighost.c b/bin/dig/dighost.c
index ca82f8e..340904f 100644
--- a/bin/dig/dighost.c
+++ b/bin/dig/dighost.c
@@ -3458,6 +3458,7 @@ process_opt(dig_lookup_t *l, dns_message_t *msg) {
isc_buffer_t optbuf;
isc_uint16_t optcode, optlen;
dns_rdataset_t *opt = msg->opt;
+ isc_boolean_t seen_cookie = ISC_FALSE;
result = dns_rdataset_first(opt);
if (result == ISC_R_SUCCESS) {
@@ -3470,7 +3471,15 @@ process_opt(dig_lookup_t *l, dns_message_t *msg) {
optlen = isc_buffer_getuint16(&optbuf);
switch (optcode) {
case DNS_OPT_COOKIE:
+ /*
+ * Only process the first cookie option.
+ */
+ if (seen_cookie) {
+ isc_buffer_forward(&optbuf, optlen);
+ break;
+ }
process_sit(l, msg, &optbuf, optlen);
+ seen_cookie = ISC_TRUE;
break;
default:
isc_buffer_forward(&optbuf, optlen);
diff --git a/bin/named/client.c b/bin/named/client.c
index 683305c..0d7331a 100644
--- a/bin/named/client.c
+++ b/bin/named/client.c
@@ -120,7 +120,10 @@
*/
#endif
-#define SIT_SIZE 24U /* 8 + 4 + 4 + 8 */
+#define COOKIE_SIZE 24U /* 8 + 4 + 4 + 8 */
+
+#define WANTNSID(x) (((x)->attributes & NS_CLIENTATTR_WANTNSID) != 0)
+#define WANTEXPIRE(x) (((x)->attributes & NS_CLIENTATTR_WANTEXPIRE) != 0)
/*% nameserver client manager structure */
struct ns_clientmgr {
@@ -1395,7 +1398,7 @@ ns_client_addopt(ns_client_t *client, dns_message_t *message,
{
char nsid[BUFSIZ], *nsidp;
#ifdef ISC_PLATFORM_USESIT
- unsigned char sit[SIT_SIZE];
+ unsigned char sit[COOKIE_SIZE];
#endif
isc_result_t result;
dns_view_t *view;
@@ -1420,7 +1423,7 @@ ns_client_addopt(ns_client_t *client, dns_message_t *message,
flags = client->extflags & DNS_MESSAGEEXTFLAG_REPLYPRESERVE;
/* Set EDNS options if applicable */
- if ((client->attributes & NS_CLIENTATTR_WANTNSID) != 0 &&
+ if (WANTNSID(client) &&
(ns_g_server->server_id != NULL ||
ns_g_server->server_usehostname)) {
if (ns_g_server->server_usehostname) {
@@ -1453,7 +1456,7 @@ ns_client_addopt(ns_client_t *client, dns_message_t *message,
INSIST(count < DNS_EDNSOPTIONS);
ednsopts[count].code = DNS_OPT_COOKIE;
- ednsopts[count].length = SIT_SIZE;
+ ednsopts[count].length = COOKIE_SIZE;
ednsopts[count].value = sit;
count++;
}
@@ -1661,19 +1664,26 @@ compute_sit(ns_client_t *client, isc_uint32_t when, isc_uint32_t nonce,
static void
process_sit(ns_client_t *client, isc_buffer_t *buf, size_t optlen) {
- unsigned char dbuf[SIT_SIZE];
+ unsigned char dbuf[COOKIE_SIZE];
unsigned char *old;
isc_stdtime_t now;
isc_uint32_t when;
isc_uint32_t nonce;
isc_buffer_t db;
+ /*
+ * If we have already seen a ECS option skip this ECS option.
+ */
+ if ((client->attributes & NS_CLIENTATTR_WANTSIT) != 0) {
+ isc_buffer_forward(buf, optlen);
+ return;
+ }
client->attributes |= NS_CLIENTATTR_WANTSIT;
isc_stats_increment(ns_g_server->nsstats,
dns_nsstatscounter_sitopt);
- if (optlen != SIT_SIZE) {
+ if (optlen != COOKIE_SIZE) {
/*
* Not our token.
*/
@@ -1717,14 +1727,13 @@ process_sit(ns_client_t *client, isc_buffer_t *buf, size_t optlen) {
isc_buffer_init(&db, dbuf, sizeof(dbuf));
compute_sit(client, when, nonce, &db);
- if (!isc_safe_memequal(old, dbuf, SIT_SIZE)) {
+ if (!isc_safe_memequal(old, dbuf, COOKIE_SIZE)) {
isc_stats_increment(ns_g_server->nsstats,
dns_nsstatscounter_sitnomatch);
return;
}
isc_stats_increment(ns_g_server->nsstats,
dns_nsstatscounter_sitmatch);
-
client->attributes |= NS_CLIENTATTR_HAVESIT;
}
#endif
@@ -1783,7 +1792,9 @@ process_opt(ns_client_t *client, dns_rdataset_t *opt) {
optlen = isc_buffer_getuint16(&optbuf);
switch (optcode) {
case DNS_OPT_NSID:
- isc_stats_increment(ns_g_server->nsstats,
+ if (!WANTNSID(client))
+ isc_stats_increment(
+ ns_g_server->nsstats,
dns_nsstatscounter_nsidopt);
client->attributes |= NS_CLIENTATTR_WANTNSID;
isc_buffer_forward(&optbuf, optlen);
@@ -1794,7 +1805,9 @@ process_opt(ns_client_t *client, dns_rdataset_t *opt) {
break;
#endif
case DNS_OPT_EXPIRE:
- isc_stats_increment(ns_g_server->nsstats,
+ if (!WANTEXPIRE(client))
+ isc_stats_increment(
+ ns_g_server->nsstats,
dns_nsstatscounter_expireopt);
client->attributes |= NS_CLIENTATTR_WANTEXPIRE;
isc_buffer_forward(&optbuf, optlen);
diff --git a/doc/arm/notes.xml b/doc/arm/notes.xml
index ebf4f55..095eb5b 100644
--- a/doc/arm/notes.xml
+++ b/doc/arm/notes.xml
@@ -51,6 +51,13 @@
<title>Security Fixes</title>
<itemizedlist>
<listitem>
+ <para>
+ Duplicate EDNS COOKIE options in a response could trigger
+ an assertion failure. This flaw is disclosed in CVE-2016-2088.
+ [RT #41809]
+ </para>
+ </listitem>
+ <listitem>
<para>
Specific APL data could trigger an INSIST. This flaw
was discovered by Brian Mitchell and is disclosed in
diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index a797e3f..ba1ae23 100644
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -7502,7 +7502,9 @@ process_opt(resquery_t *query, dns_rdataset_t *opt) {
unsigned char *sit;
dns_adbaddrinfo_t *addrinfo;
unsigned char cookie[8];
+ isc_boolean_t seen_cookie = ISC_FALSE;
#endif
+ isc_boolean_t seen_nsid = ISC_FALSE;
result = dns_rdataset_first(opt);
if (result == ISC_R_SUCCESS) {
@@ -7516,14 +7518,23 @@ process_opt(resquery_t *query, dns_rdataset_t *opt) {
INSIST(optlen <= isc_buffer_remaininglength(&optbuf));
switch (optcode) {
case DNS_OPT_NSID:
- if (query->options & DNS_FETCHOPT_WANTNSID)
+ if (!seen_nsid &&
+ query->options & DNS_FETCHOPT_WANTNSID)
log_nsid(&optbuf, optlen, query,
ISC_LOG_DEBUG(3),
query->fctx->res->mctx);
isc_buffer_forward(&optbuf, optlen);
+ seen_nsid = ISC_TRUE;
break;
#ifdef ISC_PLATFORM_USESIT
case DNS_OPT_COOKIE:
+ /*
+ * Only process the first cookie option.
+ */
+ if (seen_cookie) {
+ isc_buffer_forward(&optbuf, optlen);
+ break;
+ }
sit = isc_buffer_current(&optbuf);
compute_cc(query, cookie, sizeof(cookie));
INSIST(query->fctx->rmessage->sitbad == 0 &&
@@ -7541,6 +7552,7 @@ process_opt(resquery_t *query, dns_rdataset_t *opt) {
isc_buffer_forward(&optbuf, optlen);
inc_stats(query->fctx->res,
dns_resstatscounter_sitin);
+ seen_cookie = ISC_TRUE;
break;
#endif
default:
--
2.1.4