From bef3d2cca3552100bbe44790c8c1a4f5bef06798 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Petr=20=C5=A0pa=C4=8Dek?= Date: Thu, 16 May 2024 12:10:41 +0200 Subject: [PATCH] Remove support for SIG(0) message verification Conflict:Case adaptation and some documents are not incorporated. Reference:https://downloads.isc.org/isc/bind9/9.18.28/patches/0003-CVE-2024-1975.patch --- bin/tests/system/tsiggss/authsock.pl | 5 ++ bin/tests/system/tsiggss/tests.sh | 12 ++-- bin/tests/system/upforwd/tests.sh | 9 ++- doc/arm/general.rst | 6 +- lib/dns/message.c | 99 ++-------------------------- lib/ns/client.c | 7 ++ 6 files changed, 33 insertions(+), 105 deletions(-) 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', $buf); diff --git a/bin/tests/system/tsiggss/tests.sh b/bin/tests/system/tsiggss/tests.sh index 632bb87..4b8a903 100644 --- a/bin/tests/system/tsiggss/tests.sh +++ b/bin/tests/system/tsiggss/tests.sh @@ -116,7 +116,7 @@ status=$((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 -k ns1/Kkey.example.nil.*.private < /dev/null 2>&1 || ret=1 +$NSUPDATE -d -k ns1/Kkey.example.nil.*.private <nsupdate.out${n} 2>&1 || true +debug server 10.53.0.1 ${PORT} zone example.nil update add fred.example.nil 120 cname foo.bar. send END output=`$DIG $DIGOPTS +short cname fred.example.nil.` -[ -n "$output" ] || ret=1 -[ $ret -eq 0 ] || echo_i "failed" +# update must have failed - SIG(0) signer is not supported +[ -n "$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=$((status+ret)) diff --git a/bin/tests/system/upforwd/tests.sh b/bin/tests/system/upforwd/tests.sh index 8062d68..fa64d22 100644 --- a/bin/tests/system/upforwd/tests.sh +++ b/bin/tests/system/upforwd/tests.sh @@ -221,18 +221,21 @@ fi if test -f keyname then - echo_i "checking update forwarding to with sig0 ($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/general.rst b/doc/arm/general.rst index 225576b..794767d 100644 --- a/doc/arm/general.rst +++ b/doc/arm/general.rst @@ -534,10 +534,8 @@ than a non-authoritative response. This is considered a feature. [2] CLASS ANY queries are not supported. This is considered a feature. -[3] When receiving a query signed with a SIG(0), the server is -only able to verify the signature if it has the key in its local -authoritative data; it cannot do recursion or validation to -retrieve unknown keys. +[3] [#rfc2931] Support for SIG(0) message verification was removed + as part of the mitigation of CVE-2024-1975. [4] Compliance is with loading and serving of A6 records only. A6 records were moved to the experimental category by :rfc:`3363`. diff --git a/lib/dns/message.c b/lib/dns/message.c index 500705e..339574a 100644 --- a/lib/dns/message.c +++ b/lib/dns/message.c @@ -3331,113 +3331,26 @@ 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 /* ifdef SKAN_MSG_DEBUG */ - if (view != NULL) { - return (dns_view_checksig(view, &msgb, msg)); - } else { - return (dns_tsig_verify(&msgb, msg, NULL, NULL)); - } + if (view != NULL) { + return (dns_view_checksig(view, &msgb, msg)); } 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) { - result = DNS_R_KEYUNAUTHORIZED; - goto freesig; - } - 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); + return (dns_tsig_verify(&msgb, msg, NULL, NULL)); } } - #define INDENT(sp) \ do { \ unsigned int __i; \ diff --git a/lib/ns/client.c b/lib/ns/client.c index 264d11d..0f8eb94 100644 --- a/lib/ns/client.c +++ b/lib/ns/client.c @@ -2063,6 +2063,13 @@ ns__client_request(isc_nmhandle_t *handle, isc_result_t eresult, 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; -- 2.33.0