From 5ff88892e43c049659a8a5aef8dfd56c3712daf0 Mon Sep 17 00:00:00 2001 From: Petr Mensik Date: Tue, 16 Jul 2024 19:49:09 +0200 Subject: [PATCH] Resolve CVE-2024-1975 6404. [security] Remove SIG(0) support from named as a countermeasure for CVE-2024-1975. [GL #4480] Resolves: CVE-2024-1975 --- bin/named/client.c | 7 +++ bin/tests/system/tsiggss/authsock.pl | 5 ++ bin/tests/system/tsiggss/tests.sh | 12 ++-- bin/tests/system/upforwd/tests.sh | 21 ++++--- doc/arm/Bv9ARM-book.xml | 22 +++---- lib/dns/message.c | 94 +++------------------------- 6 files changed, 49 insertions(+), 112 deletions(-) diff --git a/bin/named/client.c b/bin/named/client.c index 368bc94..ea121b3 100644 --- a/bin/named/client.c +++ b/bin/named/client.c @@ -3013,6 +3013,13 @@ client_request(isc_task_t *task, isc_event_t *event) { ns_client_log(client, DNS_LOGCATEGORY_SECURITY, NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3), "request is signed by a nonauthoritative key"); + } else if (result == DNS_R_NOTVERIFIEDYET && + client->message->sig0 != NULL) + { + ns_client_log(client, DNS_LOGCATEGORY_SECURITY, + NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3), + "request has a SIG(0) signature but its support " + "was removed (CVE-2024-1975)"); } else { char tsigrcode[64]; isc_buffer_t b; diff --git a/bin/tests/system/tsiggss/authsock.pl b/bin/tests/system/tsiggss/authsock.pl index ab3833d..0b231ee 100644 --- a/bin/tests/system/tsiggss/authsock.pl +++ b/bin/tests/system/tsiggss/authsock.pl @@ -31,6 +31,10 @@ if (!defined($path)) { exit(1); } +# Enable output autoflush so that it's not lost when the parent sends TERM. +select STDOUT; +$| = 1; + unlink($path); my $server = IO::Socket::UNIX->new(Local => $path, Type => SOCK_STREAM, Listen => 8) or die "unable to create socket $path"; @@ -53,6 +57,7 @@ if ($timeout != 0) { } while (my $client = $server->accept()) { + printf("accept()\n"); $client->recv(my $buf, 8, 0); my ($version, $req_len) = unpack('N N', $buf); diff --git a/bin/tests/system/tsiggss/tests.sh b/bin/tests/system/tsiggss/tests.sh index 456ce61..d0db388 100644 --- a/bin/tests/system/tsiggss/tests.sh +++ b/bin/tests/system/tsiggss/tests.sh @@ -116,7 +116,7 @@ status=$((status+ret)) echo_i "testing external update policy (CNAME) with auth sock ($n)" ret=0 -$PERL ./authsock.pl --type=CNAME --path=ns1/auth.sock --pidfile=authsock.pid --timeout=120 > /dev/null 2>&1 & +$PERL ./authsock.pl --type=CNAME --path=ns1/auth.sock --pidfile=authsock.pid --timeout=120 >authsock.log 2>&1 & sleep 1 test_update $n testcname.example.nil. CNAME "86400 CNAME testdenied.example.nil" "testdenied" || ret=1 n=$((n+1)) @@ -130,17 +130,19 @@ n=$((n+1)) if [ "$ret" -ne 0 ]; then echo_i "failed"; fi status=$((status+ret)) -echo_i "testing external policy with SIG(0) key ($n)" +echo_i "testing external policy with unsupported SIG(0) key ($n)" ret=0 -$NSUPDATE -R $RANDFILE -k ns1/Kkey.example.nil.*.private < /dev/null 2>&1 || ret=1 +$NSUPDATE -R $RANDFILE -k ns1/Kkey.example.nil.*.private <nsupdate.out${n} 2>&1 || true +debug server 10.53.0.1 ${PORT} zone example.nil update add fred.example.nil 120 cname foo.bar. send END +# update must have failed - SIG(0) signer is not supported output=`$DIG $DIGOPTS +short cname fred.example.nil.` -[ -n "$output" ] || ret=1 -[ $ret -eq 0 ] || echo_i "failed" +[ -n "$output" ] && ret=1 +grep -F "signer=key.example.nil" authsock.log >/dev/null && ret=1 n=$((n+1)) if [ "$ret" -ne 0 ]; then echo_i "failed"; fi status=$((status+ret)) diff --git a/bin/tests/system/upforwd/tests.sh b/bin/tests/system/upforwd/tests.sh index ebc9ded..f5b89d4 100644 --- a/bin/tests/system/upforwd/tests.sh +++ b/bin/tests/system/upforwd/tests.sh @@ -181,19 +181,22 @@ n=`expr $n + 1` if test -f keyname then - echo_i "checking update forwarding to with sig0 ($n)" + echo_i "checking update forwarding to with sig0 (expected to fail) ($n)" ret=0 keyname=`cat keyname` - $NSUPDATE -k $keyname.private -- - <nsupdate.out.$n 2>&1 && ret=1 $DIG -p ${PORT} unsigned.example2 A @10.53.0.1 > dig.out.ns1.test$n - grep "status: NOERROR" dig.out.ns1.test$n > /dev/null || ret=1 + grep "status: NOERROR" dig.out.ns1.test$n >/dev/null && ret=1 if [ $ret != 0 ] ; then echo_i "failed"; fi status=`expr $status + $ret` n=`expr $n + 1` diff --git a/doc/arm/Bv9ARM-book.xml b/doc/arm/Bv9ARM-book.xml index acf772b..563dced 100644 --- a/doc/arm/Bv9ARM-book.xml +++ b/doc/arm/Bv9ARM-book.xml @@ -2027,7 +2027,7 @@ allow-update { !{ !localnets; any; }; key host1-host2. ;}; The TKEY process is initiated by a client or server by sending a query of type TKEY to a TKEY-aware server. The query must include an appropriate KEY record in the additional section, and - must be signed using either TSIG or SIG(0) with a previously + must be signed using TSIG with a previously established key. The server's response, if successful, contains a TKEY record in its answer section. After this transaction, both participants have enough information to calculate a @@ -2050,24 +2050,24 @@ allow-update { !{ !localnets; any; }; key host1-host2. ;};
SIG(0) - BIND partially supports DNSSEC SIG(0) + BIND partially supported DNSSEC SIG(0) transaction signatures as specified in RFC 2535 and RFC 2931. SIG(0) uses public/private keys to authenticate messages. Access control - is performed in the same manner as with TSIG keys; privileges can be + were performed in the same manner as with TSIG keys; privileges can be granted or denied in ACL directives based on the key name. - When a SIG(0) signed message is received, it is only + When a SIG(0) signed message were received, it were only verified if the key is known and trusted by the server. The - server does not attempt to recursively fetch or validate the + server did not attempt to recursively fetch or validate the key. - SIG(0) signing of multiple-message TCP streams is not supported. + SIG(0) signing of multiple-message TCP streams were not supported. - The only tool shipped with BIND 9 that - generates SIG(0) signed messages is nsupdate. + Support for SIG(0) message verification was removed + as part of the mitigation of CVE-2024-1975.
@@ -12655,7 +12655,7 @@ example.com. NS ns2.example.net. either grants or denies permission for one or more names in the zone to be updated by one or more identities. Identity is determined by the key that - signed the update request, using either TSIG or SIG(0). + signed the update request, using TSIG. In most cases, update-policy rules only apply to key-based identities. There is no way to specify update permissions based on client source @@ -12742,7 +12742,7 @@ example.com. NS ns2.example.net. The identity field must be set to a fully qualified domain name. In most cases, this - represents the name of the TSIG or SIG(0) key that must be + represents the name of the TSIG key that must be used to sign the update request. If the specified name is a wildcard, it is subject to DNS wildcard expansion, and the rule may apply to multiple identities. When a TKEY exchange @@ -15952,7 +15952,7 @@ HOST-127.EXAMPLE. MX 0 . ACLs match clients on the basis of up to three characteristics: - 1) The client's IP address; 2) the TSIG or SIG(0) key that was + 1) The client's IP address; 2) the TSIG key that was used to sign the request, if any; and 3) an address prefix encoded in an EDNS Client-Subnet option, if any. diff --git a/lib/dns/message.c b/lib/dns/message.c index a44eb2d..9ea2b9e 100644 --- a/lib/dns/message.c +++ b/lib/dns/message.c @@ -3373,103 +3373,23 @@ dns_message_dumpsig(dns_message_t *msg, char *txt1) { isc_result_t dns_message_checksig(dns_message_t *msg, dns_view_t *view) { - isc_buffer_t b, msgb; + isc_buffer_t msgb; REQUIRE(DNS_MESSAGE_VALID(msg)); - if (msg->tsigkey == NULL && msg->tsig == NULL && msg->sig0 == NULL) + if (msg->tsigkey == NULL && msg->tsig == NULL) return (ISC_R_SUCCESS); INSIST(msg->saved.base != NULL); isc_buffer_init(&msgb, msg->saved.base, msg->saved.length); isc_buffer_add(&msgb, msg->saved.length); - if (msg->tsigkey != NULL || msg->tsig != NULL) { #ifdef SKAN_MSG_DEBUG - dns_message_dumpsig(msg, "dns_message_checksig#1"); + dns_message_dumpsig(msg, "dns_message_checksig#1"); #endif - if (view != NULL) - return (dns_view_checksig(view, &msgb, msg)); - else - return (dns_tsig_verify(&msgb, msg, NULL, NULL)); - } else { - dns_rdata_t rdata = DNS_RDATA_INIT; - dns_rdata_sig_t sig; - dns_rdataset_t keyset; - isc_result_t result; - - result = dns_rdataset_first(msg->sig0); - INSIST(result == ISC_R_SUCCESS); - dns_rdataset_current(msg->sig0, &rdata); - - /* - * This can occur when the message is a dynamic update, since - * the rdata length checking is relaxed. This should not - * happen in a well-formed message, since the SIG(0) is only - * looked for in the additional section, and the dynamic update - * meta-records are in the prerequisite and update sections. - */ - if (rdata.length == 0) - return (ISC_R_UNEXPECTEDEND); - - result = dns_rdata_tostruct(&rdata, &sig, msg->mctx); - if (result != ISC_R_SUCCESS) - return (result); - - dns_rdataset_init(&keyset); - if (view == NULL) - return (DNS_R_KEYUNAUTHORIZED); - result = dns_view_simplefind(view, &sig.signer, - dns_rdatatype_key /* SIG(0) */, - 0, 0, false, &keyset, NULL); - - if (result != ISC_R_SUCCESS) { - /* XXXBEW Should possibly create a fetch here */ - result = DNS_R_KEYUNAUTHORIZED; - goto freesig; - } else if (keyset.trust < dns_trust_secure) { - /* XXXBEW Should call a validator here */ - result = DNS_R_KEYUNAUTHORIZED; - goto freesig; - } - result = dns_rdataset_first(&keyset); - INSIST(result == ISC_R_SUCCESS); - for (; - result == ISC_R_SUCCESS; - result = dns_rdataset_next(&keyset)) - { - dst_key_t *key = NULL; - - dns_rdata_reset(&rdata); - dns_rdataset_current(&keyset, &rdata); - isc_buffer_init(&b, rdata.data, rdata.length); - isc_buffer_add(&b, rdata.length); - - result = dst_key_fromdns(&sig.signer, rdata.rdclass, - &b, view->mctx, &key); - if (result != ISC_R_SUCCESS) - continue; - if (dst_key_alg(key) != sig.algorithm || - dst_key_id(key) != sig.keyid || - !(dst_key_proto(key) == DNS_KEYPROTO_DNSSEC || - dst_key_proto(key) == DNS_KEYPROTO_ANY)) - { - dst_key_free(&key); - continue; - } - result = dns_dnssec_verifymessage(&msgb, msg, key); - dst_key_free(&key); - if (result == ISC_R_SUCCESS) - break; - } - if (result == ISC_R_NOMORE) - result = DNS_R_KEYUNAUTHORIZED; - - freesig: - if (dns_rdataset_isassociated(&keyset)) - dns_rdataset_disassociate(&keyset); - dns_rdata_freestruct(&sig); - return (result); - } + if (view != NULL) + return (dns_view_checksig(view, &msgb, msg)); + else + return (dns_tsig_verify(&msgb, msg, NULL, NULL)); } #define INDENT(sp) \ -- 2.45.2