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bind/bind-9.18-CVE-2026-11721.patch
AlmaLinux RelEng Bot c9ad8bab07 import UBI bind-9.18.33-15.el10_2.10
2026-08-17 01:00:41 -04:00

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From 107fba6767a792bf9022dbfc8a75e3dc61c0d76d Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Tue, 14 Apr 2026 12:24:33 +1000
Subject: [PATCH] Invalid signed wildcard records were being accepted
An RRSIG whose Labels field indicates fewer labels than its signer
name requires was being accepted. When such a record covers a
wildcard, the validator reconstructs a wildcard owner name above the
signer's zone and caches it as secure. RFC 8198 cache synthesis
(synth-from-dnssec) then serves that forged wildcard for unrelated
names, poisoning the cache.
These records are now rejected, both when an RRSIG is parsed and when
its signature is verified.
(cherry picked from commit 084ca5ee10515e461d46b63df9660b8394bc7de9)
(cherry picked from commit 15089066b15f826d7487c3d160b5872820f84b83)
---
lib/dns/dnssec.c | 43 +++++++++++++++++++++++---------
lib/dns/rdata/generic/rrsig_46.c | 37 ++++++++++++++++++++-------
2 files changed, 59 insertions(+), 21 deletions(-)
diff --git a/lib/dns/dnssec.c b/lib/dns/dnssec.c
index 662136db87..86f03680e9 100644
--- a/lib/dns/dnssec.c
+++ b/lib/dns/dnssec.c
@@ -137,11 +137,11 @@ dns_dnssec_keyfromrdata(const dns_name_t *name, const dns_rdata_t *rdata,
isc_buffer_t b;
isc_region_t r;
- INSIST(name != NULL);
- INSIST(rdata != NULL);
- INSIST(mctx != NULL);
- INSIST(key != NULL);
- INSIST(*key == NULL);
+ REQUIRE(name != NULL);
+ REQUIRE(rdata != NULL);
+ REQUIRE(mctx != NULL);
+ REQUIRE(key != NULL);
+ REQUIRE(*key == NULL);
REQUIRE(rdata->type == dns_rdatatype_key ||
rdata->type == dns_rdatatype_dnskey);
@@ -195,12 +195,14 @@ dns_dnssec_sign(const dns_name_t *name, dns_rdataset_t *set, dst_key_t *key,
isc_buffer_t *databuf = NULL;
char data[256 + 8];
uint32_t flags;
+ unsigned int labels;
unsigned int sigsize;
dns_fixedname_t fnewname;
dns_fixedname_t fsigner;
REQUIRE(name != NULL);
- REQUIRE(dns_name_countlabels(name) <= 255);
+ labels = dns_name_countlabels(name);
+ REQUIRE(labels <= 255 && labels > 0);
REQUIRE(set != NULL);
REQUIRE(key != NULL);
REQUIRE(inception != NULL);
@@ -240,7 +242,7 @@ dns_dnssec_sign(const dns_name_t *name, dns_rdataset_t *set, dst_key_t *key,
sig.covered = set->type;
sig.algorithm = dst_key_alg(key);
- sig.labels = dns_name_countlabels(name) - 1;
+ sig.labels = labels - 1;
if (dns_name_iswildcard(name)) {
sig.labels--;
}
@@ -384,11 +386,14 @@ dns_dnssec_verify(const dns_name_t *name, dns_rdataset_t *set, dst_key_t *key,
isc_result_t ret;
unsigned char data[300];
dst_context_t *ctx = NULL;
- int labels = 0;
+ unsigned int labels;
+ unsigned int siglabels;
uint32_t flags;
bool downcase = false;
REQUIRE(name != NULL);
+ labels = dns_name_countlabels(name);
+ REQUIRE(labels > 0);
REQUIRE(set != NULL);
REQUIRE(key != NULL);
REQUIRE(mctx != NULL);
@@ -403,6 +408,21 @@ dns_dnssec_verify(const dns_name_t *name, dns_rdataset_t *set, dst_key_t *key,
return DNS_R_SIGINVALID;
}
+ /*
+ * The RRSIG labels field can't indicate fewer labels than the
+ * signer. Also the labels shouldn't be greater than that of
+ * the owner name.
+ *
+ * sig.labels doesn't include the root label, so add 1 to account
+ * for it.
+ */
+ siglabels = sig.labels + 1;
+ if (siglabels < dns_name_countlabels(&sig.signer) || siglabels > labels)
+ {
+ inc_stat(dns_dnssecstats_fail);
+ return DNS_R_SIGINVALID;
+ }
+
if (isc_serial_lt(sig.timeexpire, sig.timesigned)) {
inc_stat(dns_dnssecstats_fail);
return DNS_R_SIGINVALID;
@@ -482,10 +502,9 @@ again:
* If the name is an expanded wildcard, use the wildcard name.
*/
dns_fixedname_init(&fnewname);
- labels = dns_name_countlabels(name) - 1;
RUNTIME_CHECK(dns_name_downcase(name, dns_fixedname_name(&fnewname),
NULL) == ISC_R_SUCCESS);
- if (labels - sig.labels > 0) {
+ if (labels > siglabels) {
dns_name_split(dns_fixedname_name(&fnewname), sig.labels + 1,
NULL, dns_fixedname_name(&fnewname));
}
@@ -496,7 +515,7 @@ again:
* Create an envelope for each rdata: <name|type|class|ttl>.
*/
isc_buffer_init(&envbuf, data, sizeof(data));
- if (labels - sig.labels > 0) {
+ if (labels > siglabels) {
isc_buffer_putuint8(&envbuf, 1);
isc_buffer_putuint8(&envbuf, '*');
memmove(data + 2, r.base, r.length);
@@ -592,7 +611,7 @@ cleanup_struct:
inc_stat(dns_dnssecstats_fail);
}
- if (ret == ISC_R_SUCCESS && labels - sig.labels > 0) {
+ if (ret == ISC_R_SUCCESS && labels > siglabels) {
if (wild != NULL) {
RUNTIME_CHECK(dns_name_concatenate(
dns_wildcardname,
diff --git a/lib/dns/rdata/generic/rrsig_46.c b/lib/dns/rdata/generic/rrsig_46.c
index 2cc315bdea..53648f1bfa 100644
--- a/lib/dns/rdata/generic/rrsig_46.c
+++ b/lib/dns/rdata/generic/rrsig_46.c
@@ -23,12 +23,12 @@
static isc_result_t
fromtext_rrsig(ARGS_FROMTEXT) {
isc_token_t token;
- unsigned char c;
+ unsigned char alg, labels;
long i;
dns_rdatatype_t covered;
- char *e;
+ char *e = NULL;
isc_result_t result;
- dns_name_t name;
+ dns_name_t signer;
isc_buffer_t buffer;
uint32_t time_signed, time_expire;
@@ -61,8 +61,8 @@ fromtext_rrsig(ARGS_FROMTEXT) {
*/
RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
false));
- RETTOK(dns_secalg_fromtext(&c, &token.value.as_textregion));
- RETERR(mem_tobuffer(target, &c, 1));
+ RETTOK(dns_secalg_fromtext(&alg, &token.value.as_textregion));
+ RETERR(mem_tobuffer(target, &alg, 1));
/*
* Labels.
@@ -72,8 +72,8 @@ fromtext_rrsig(ARGS_FROMTEXT) {
if (token.value.as_ulong > 0xffU) {
RETTOK(ISC_R_RANGE);
}
- c = (unsigned char)token.value.as_ulong;
- RETERR(mem_tobuffer(target, &c, 1));
+ labels = (unsigned char)token.value.as_ulong;
+ RETERR(mem_tobuffer(target, &labels, 1));
/*
* Original ttl.
@@ -144,12 +144,20 @@ fromtext_rrsig(ARGS_FROMTEXT) {
*/
RETERR(isc_lex_getmastertoken(lexer, &token, isc_tokentype_string,
false));
- dns_name_init(&name, NULL);
+ dns_name_init(&signer, NULL);
buffer_fromregion(&buffer, &token.value.as_region);
if (origin == NULL) {
origin = dns_rootname;
}
- RETTOK(dns_name_fromtext(&name, &buffer, origin, options, target));
+ RETTOK(dns_name_fromtext(&signer, &buffer, origin, options, target));
+
+ /*
+ * (RRSIG labels doesn't include the root label, so add one
+ * to normalize it before checking against the signer.)
+ */
+ if ((unsigned int)(labels + 1) < dns_name_countlabels(&signer)) {
+ RETTOK(ISC_R_RANGE);
+ }
/*
* Sig.
@@ -278,6 +286,7 @@ static isc_result_t
fromwire_rrsig(ARGS_FROMWIRE) {
isc_region_t sr;
dns_name_t name;
+ unsigned char labels;
REQUIRE(type == dns_rdatatype_rrsig);
@@ -300,6 +309,8 @@ fromwire_rrsig(ARGS_FROMWIRE) {
return ISC_R_UNEXPECTEDEND;
}
+ labels = sr.base[3];
+
isc_buffer_forward(source, 18);
RETERR(mem_tobuffer(target, sr.base, 18));
@@ -309,6 +320,14 @@ fromwire_rrsig(ARGS_FROMWIRE) {
dns_name_init(&name, NULL);
RETERR(dns_name_fromwire(&name, source, dctx, options, target));
+ /*
+ * (RRSIG labels doesn't include the root label, so add one
+ * to normalize it before checking against the signer.)
+ */
+ if ((unsigned int)(labels + 1) < dns_name_countlabels(&name)) {
+ RETERR(DNS_R_FORMERR);
+ }
+
/*
* Sig.
*/
--
2.55.0
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