fix(dnssec): validate short RSA DNSKEY blobs

debian/changelog

@@ -1,3 +1,9 @@
+systemd (255.2-4deepin31) unstable; urgency=medium
+
+  * Fix DNSSEC: validate short RSA DNSKEY blobs to prevent out-of-bounds read
+
+ -- jiabowen <jiabowen@uniontech.com>  Wed, 03 Jun 2026 14:22:00 +0800
+
 systemd (255.2-4deepin30) unstable; urgency=medium
 
   * Fix tmpfiles x11 socket age-based cleanup causing unexpected removal

debian/patches/fix-dnssec-validate-short-rsa-dnskey.patch

@@ -0,0 +1,108 @@
+diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c
+index 017c370b0e..f33bba28ff 100644
+--- a/src/resolve/resolved-dns-dnssec.c
++++ b/src/resolve/resolved-dns-dnssec.c
+@@ -141,10 +141,15 @@ static int dnssec_rsa_verify(
+         assert(rrsig);
+         assert(dnskey);
+
++        if (dnskey->dnskey.key_size < 1)
++                return -EINVAL;
++
+         if (*(uint8_t*) dnskey->dnskey.key == 0) {
+                 /* exponent is > 255 bytes long */
+
+-                exponent = (uint8_t*) dnskey->dnskey.key + 3;
++                if (dnskey->dnskey.key_size < 3)
++                        return -EINVAL;
++
+                 exponent_size =
+                         ((size_t) (((uint8_t*) dnskey->dnskey.key)[1]) << 8) |
+                         ((size_t) ((uint8_t*) dnskey->dnskey.key)[2]);
+@@ -155,13 +160,12 @@ static int dnssec_rsa_verify(
+                 if (3 + exponent_size >= dnskey->dnskey.key_size)
+                         return -EINVAL;
+
++                exponent = (uint8_t*) dnskey->dnskey.key + 3;
+                 modulus = (uint8_t*) dnskey->dnskey.key + 3 + exponent_size;
+                 modulus_size = dnskey->dnskey.key_size - 3 - exponent_size;
+
+         } else {
+                 /* exponent is <= 255 bytes long */
+-
+-                exponent = (uint8_t*) dnskey->dnskey.key + 1;
+                 exponent_size = (size_t) ((uint8_t*) dnskey->dnskey.key)[0];
+
+                 if (exponent_size <= 0)
+@@ -170,6 +174,7 @@ static int dnssec_rsa_verify(
+                 if (1 + exponent_size >= dnskey->dnskey.key_size)
+                         return -EINVAL;
+
++                exponent = (uint8_t*) dnskey->dnskey.key + 1;
+                 modulus = (uint8_t*) dnskey->dnskey.key + 1 + exponent_size;
+                 modulus_size = dnskey->dnskey.key_size - 1 - exponent_size;
+         }
+diff --git a/src/resolve/test-dnssec.c b/src/resolve/test-dnssec.c
+index eaa4ef9959..f6ea6214f4 100644
+--- a/src/resolve/test-dnssec.c
++++ b/src/resolve/test-dnssec.c
+@@ -521,6 +521,59 @@ TEST(dnssec_verify_rrset) {
+         assert_se(result == DNSSEC_VALIDATED);
+ }
+
++TEST(dnssec_verify_rrset_invalid_rsa_dnskey) {
++        static const uint8_t signature_blob[] = { 0x00 };
++        static const uint8_t dnskey_blob[] = { 0x00 };
++
++        _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *a = NULL, *rrsig = NULL, *dnskey = NULL;
++        _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
++        DnssecResult result;
++
++        ASSERT_NOT_NULL(a = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, "example.com."));
++
++        a->a.in_addr.s_addr = inet_addr("192.0.2.1");
++
++        ASSERT_NOT_NULL(dnskey = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_DNSKEY, "example.com."));
++
++        dnskey->dnskey.flags = DNSKEY_FLAG_ZONE_KEY;
++        dnskey->dnskey.protocol = 3;
++        dnskey->dnskey.algorithm = DNSSEC_ALGORITHM_RSASHA256;
++        dnskey->dnskey.key_size = sizeof(dnskey_blob);
++        ASSERT_NOT_NULL(dnskey->dnskey.key = memdup(dnskey_blob, sizeof(dnskey_blob)));
++
++        ASSERT_NOT_NULL(rrsig = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_RRSIG, "example.com."));
++
++        rrsig->rrsig.type_covered = DNS_TYPE_A;
++        rrsig->rrsig.algorithm = DNSSEC_ALGORITHM_RSASHA256;
++        rrsig->rrsig.labels = 2;
++        rrsig->rrsig.original_ttl = 3600;
++        rrsig->rrsig.expiration = 2000000000;
++        rrsig->rrsig.inception = 1000000000;
++        rrsig->rrsig.key_tag = dnssec_keytag(dnskey, false);
++        ASSERT_NOT_NULL(rrsig->rrsig.signer = strdup("example.com."));
++        rrsig->rrsig.signature_size = sizeof(signature_blob);
++        ASSERT_NOT_NULL(rrsig->rrsig.signature = memdup(signature_blob, rrsig->rrsig.signature_size));
++
++        ASSERT_GT(dnssec_key_match_rrsig(a->key, rrsig), 0);
++        ASSERT_GT(dnssec_rrsig_match_dnskey(rrsig, dnskey, false), 0);
++
++        ASSERT_NOT_NULL(answer = dns_answer_new(1));
++        ASSERT_OK(dns_answer_add(answer, a, 0, DNS_ANSWER_AUTHENTICATED, NULL));
++
++        ASSERT_ERROR(dnssec_verify_rrset(answer, a->key, rrsig, dnskey,
++                                         rrsig->rrsig.inception * USEC_PER_SEC, &result),
++                     EINVAL);
++
++        dnskey->dnskey.key = mfree(dnskey->dnskey.key);
++        dnskey->dnskey.key_size = 0;
++        rrsig->rrsig.key_tag = dnssec_keytag(dnskey, false);
++
++        ASSERT_GT(dnssec_rrsig_match_dnskey(rrsig, dnskey, false), 0);
++        ASSERT_ERROR(dnssec_verify_rrset(answer, a->key, rrsig, dnskey,
++                                         rrsig->rrsig.inception * USEC_PER_SEC, &result),
++                     EINVAL);
++}
++
+ TEST(dnssec_verify_rrset2) {
+         static const uint8_t signature_blob[] = {
+                 0x48, 0x45, 0xc8, 0x8b, 0xc0, 0x14, 0x92, 0xf5, 0x15, 0xc6, 0x84, 0x9d, 0x2f, 0xe3, 0x32, 0x11,

debian/patches/series

@@ -42,3 +42,4 @@ hwdb-reject-oob-fnmatch.patch
 exec-invoke-chdir-after-chroot.patch
 uniontech-skip-clock-restore-for-timesyncd.patch
 fix-tmpfiles-x11-cleanup.patch
+fix-dnssec-validate-short-rsa-dnskey.patch