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c-ares: patch CVE-2026-69184

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Pick patch per [1].

[1] https://security-tracker.debian.org/tracker/CVE-2026-69184

Signed-off-by: Peter Marko <peter.marko@siemens.com>
Signed-off-by: Anuj Mittal <anuj.mittal@oss.qualcomm.com>
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Peter Marko authored and Anuj Mittal committed 2026-10-26 10:10:41 +05:30
1 parent 9c30658af2
commit 4e6937fa8f
2 files changed
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meta-oe/recipes-support/c-ares/c-ares/CVE-2026-69184.patch
+295
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@@ -0,0 +1,295 @@
From 5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b Mon Sep 17 00:00:00 2001
From: "c-ares-backport-gha[bot]"
<299594594+c-ares-backport-gha[bot]@users.noreply.github.com>
Date: Sun, 5 Jul 2026 05:41:49 +0000
Subject: [PATCH] [Backport v1.34] enforce 255 octet name limit when parsing
dns names (#1210)
# Description
Backport of #1164 to `v1.34`.
Signed-off-by: Syed Mohammed Nayyar <jmestwa@gmail.com>
Co-authored-by: jmestwa-coder <jmestwa@gmail.com>
CVE: CVE-2026-69184
Upstream-Status: Backport [https://github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b]
Signed-off-by: Peter Marko <peter.marko@siemens.com>
---
src/lib/ares_dns_name.c | 42 +++++++++-
test/ares-test-parse.cc | 176 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 216 insertions(+), 2 deletions(-)
diff --git a/src/lib/ares_dns_name.c b/src/lib/ares_dns_name.c
index b7fdf594..134f3edc 100644
--- a/src/lib/ares_dns_name.c
+++ b/src/lib/ares_dns_name.c
@@ -27,6 +27,18 @@
#include "ares.h"
#include "ares_private.h"
+/* RFC 1035 3.1 limits a name to 255 octets. We track presentation length
+ * (label octets plus one separator before each label after the first), which is
+ * up to ~2 octets looser than the strict wire limit and so never rejects a
+ * compliant name. Shared by the read and write paths. */
+#define ARES_MAX_NAME_PRESENTATION_LEN 255
+
+/* A name of <= 255 octets holds at most 128 labels, so it can never legitimately
+ * require more than that many compression-pointer jumps. Bounding the number of
+ * indirections stops a name built purely from pointers (which never adds label
+ * bytes, so the length cap never fires) from being walked without limit. */
+#define ARES_MAX_INDIRS 128
+
typedef struct {
char *name;
size_t name_len;
@@ -50,7 +62,7 @@ static ares_status_t ares__nameoffset_create(ares__llist_t **list,
ares_nameoffset_t *off = NULL;
if (list == NULL || name == NULL || ares_strlen(name) == 0 ||
- ares_strlen(name) > 255) {
+ ares_strlen(name) > ARES_MAX_NAME_PRESENTATION_LEN) {
return ARES_EFORMERR;
}
@@ -341,7 +353,7 @@ static ares_status_t ares_split_dns_name(ares_dns_labels_t *labels,
}
/* Can't exceed maximum (unescaped) length */
- if (labels->num && total_len + labels->num - 1 > 255) {
+ if (labels->num && total_len + labels->num - 1 > ARES_MAX_NAME_PRESENTATION_LEN) {
status = ARES_EBADNAME;
goto done;
}
@@ -541,6 +553,8 @@ ares_status_t ares__dns_name_parse(ares__buf_t *buf, char **name,
ares_status_t status;
ares__buf_t *namebuf = NULL;
size_t label_start = ares__buf_get_position(buf);
+ size_t name_len = 0;
+ size_t indir = 0;
if (buf == NULL) {
return ARES_EFORMERR;
@@ -612,6 +626,16 @@ ares_status_t ares__dns_name_parse(ares__buf_t *buf, char **name,
goto fail;
}
+ /* Bound the number of indirections. A name made purely of pointers never
+ * adds label bytes, so the length cap below can't stop it; the
+ * strictly-decreasing rule alone still allows thousands of jumps per name.
+ * No legitimate <= 255 octet name needs more than 128 labels/jumps. */
+ indir++;
+ if (indir > ARES_MAX_INDIRS) {
+ status = ARES_EBADNAME;
+ goto fail;
+ }
+
/* First time we make a jump, save the current position */
if (save_offset == 0) {
save_offset = ares__buf_get_position(buf);
@@ -635,6 +659,20 @@ ares_status_t ares__dns_name_parse(ares__buf_t *buf, char **name,
/* New label */
+ /* RFC 1035 3.1 limits a name to 255 octets. Enforce it during
+ * decompression so labels reached through a chain of pointers can't expand a
+ * single name without bound. Track the presentation length (label data plus
+ * the separator that precedes each label after the first), matching
+ * ares_split_dns_name() on the write side. */
+ if (name_len) {
+ name_len++;
+ }
+ name_len += c;
+ if (name_len > ARES_MAX_NAME_PRESENTATION_LEN) {
+ status = ARES_EBADNAME;
+ goto fail;
+ }
+
/* Labels are separated by periods */
if (ares__buf_len(namebuf) != 0 && name != NULL) {
status = ares__buf_append_byte(namebuf, '.');
diff --git a/test/ares-test-parse.cc b/test/ares-test-parse.cc
index 81fd7deb..399c94dd 100644
--- a/test/ares-test-parse.cc
+++ b/test/ares-test-parse.cc
@@ -219,5 +219,181 @@ TEST_F(LibraryTest, ParseMalformedRRCount) {
EXPECT_EQ(nullptr, dnsrec);
}
+TEST_F(LibraryTest, ParseRejectsOverlongName) {
+ // RFC 1035 3.1 limits a name to 255 octets. A longer name (here built from
+ // six 63-octet labels) must be rejected instead of expanded.
+ std::vector<byte> data = {
+ 0x12, 0x34, 0x81, 0x80,
+ 0x00, 0x01, // num questions
+ 0x00, 0x01, // num answer RRs
+ 0x00, 0x00, // num authority RRs
+ 0x00, 0x00, // num additional RRs
+ // Question
+ 0x01, 'a', 0x00,
+ 0x00, 0x01, // type A
+ 0x00, 0x01, // class IN
+ };
+ // Answer name: 6 x 63 label octets + 5 separators = 383 presentation octets
+ // (> 255), then root terminator
+ for (int i = 0; i < 6; i++) {
+ data.push_back(63);
+ for (int j = 0; j < 63; j++) {
+ data.push_back('a');
+ }
+ }
+ data.push_back(0x00);
+ std::vector<byte> tail = {
+ 0x00, 0x01, // type A
+ 0x00, 0x01, // class IN
+ 0x00, 0x00, 0x00, 0x00, // TTL
+ 0x00, 0x04, // rdata length
+ 0x01, 0x02, 0x03, 0x04,
+ };
+ data.insert(data.end(), tail.begin(), tail.end());
+
+ ares_dns_record_t *dnsrec = NULL;
+ EXPECT_EQ(ARES_EBADNAME, ares_dns_parse(data.data(), data.size(), 0, &dnsrec));
+ EXPECT_EQ(nullptr, dnsrec);
+}
+
+TEST_F(LibraryTest, ParseRejectsOverlongNameViaPointers) {
+ // The answer name is one 63-octet label followed by a compression pointer back
+ // to the question name (four 63-octet labels). Expanded that is 5 x 63 label
+ // octets + 4 separators = 319 presentation octets (> 255), so the length has
+ // to accumulate across the pointer jump for this to be rejected.
+ std::vector<byte> data = {
+ 0x12, 0x34, 0x81, 0x80,
+ 0x00, 0x01, // num questions
+ 0x00, 0x01, // num answer RRs
+ 0x00, 0x00, // num authority RRs
+ 0x00, 0x00, // num additional RRs
+ };
+ // Question name: 4 x 63 label octets + 3 separators = 255 presentation octets,
+ // exactly the limit, so the question itself is accepted.
+ for (int i = 0; i < 4; i++) {
+ data.push_back(63);
+ for (int j = 0; j < 63; j++) {
+ data.push_back('a');
+ }
+ }
+ data.push_back(0x00);
+ std::vector<byte> qtail = {0x00, 0x01, 0x00, 0x01}; // type A, class IN
+ data.insert(data.end(), qtail.begin(), qtail.end());
+ // Answer name: one 63-octet label, then a pointer to the question name.
+ data.push_back(63);
+ for (int j = 0; j < 63; j++) {
+ data.push_back('a');
+ }
+ data.push_back(0xc0);
+ data.push_back(0x0c); // -> offset 12, start of question name
+ std::vector<byte> tail = {
+ 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 1, 2, 3, 4,
+ };
+ data.insert(data.end(), tail.begin(), tail.end());
+ ares_dns_record_t *dnsrec = NULL;
+ EXPECT_EQ(ARES_EBADNAME, ares_dns_parse(data.data(), data.size(), 0, &dnsrec));
+ EXPECT_EQ(nullptr, dnsrec);
+}
+
+TEST_F(LibraryTest, ParseRejectsPointerChain) {
+ // A name built purely from compression pointers adds no label octets, so the
+ // length cap alone can never stop it. A long backward chain of pointers is
+ // hidden in the opaque rdata of a raw RR, and a second RR's name points at the
+ // top of the chain; walking it must trip the indirection cap and return
+ // EBADNAME rather than following every jump.
+ std::vector<byte> data = {
+ 0x12, 0x34, 0x81, 0x80,
+ 0x00, 0x01, // num questions
+ 0x00, 0x02, // num answer RRs
+ 0x00, 0x00, // num authority RRs
+ 0x00, 0x00, // num additional RRs
+ // Question
+ 0x01, 'a', 0x00,
+ 0x00, 0x01, // type A
+ 0x00, 0x01, // class IN
+ // RR1: raw RR (unknown type) whose rdata carries the pointer chain
+ 0x00, // name = root
+ 0xff, 0xfe, // type (unknown -> stored raw, rdata not name-parsed)
+ 0x00, 0x01, // class IN
+ 0x00, 0x00, 0x00, 0x00, // TTL
+ };
+ // The chain lives in RR1's rdata, which begins two octets past here (after the
+ // rdlength we are about to write), so compute absolute offsets from there.
+ const size_t rdata_off = data.size() + 2;
+ std::vector<byte> chain;
+ chain.push_back(0x00); // deepest target: root terminator
+ size_t prev = rdata_off; // absolute offset of the root
+ size_t top = prev;
+ const int N = 200; // well past the 128 indirection cap
+ for (int i = 0; i < N; i++) {
+ size_t here = rdata_off + chain.size();
+ chain.push_back(0xc0 | ((prev >> 8) & 0x3f));
+ chain.push_back(prev & 0xff);
+ top = here;
+ prev = here;
+ }
+ data.push_back((chain.size() >> 8) & 0xff); // rdlength
+ data.push_back(chain.size() & 0xff);
+ data.insert(data.end(), chain.begin(), chain.end());
+ // RR2: name = pointer to the top of the chain.
+ data.push_back(0xc0 | ((top >> 8) & 0x3f));
+ data.push_back(top & 0xff);
+ std::vector<byte> tail = {
+ 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 1, 2, 3, 4,
+ };
+ data.insert(data.end(), tail.begin(), tail.end());
+
+ ares_dns_record_t *dnsrec = NULL;
+ EXPECT_EQ(ARES_EBADNAME, ares_dns_parse(data.data(), data.size(), 0, &dnsrec));
+ EXPECT_EQ(nullptr, dnsrec);
+}
+
+TEST_F(LibraryTest, ParseAcceptsMaxLengthName) {
+ // Exactly 255 presentation octets: 4 x 63 = 252 + 3 separators = 255, which
+ // must still be accepted (the bound is "> 255", not ">= 255").
+ std::vector<byte> data = {
+ 0x12, 0x34, 0x81, 0x80, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00,
+ 0x00, 0x00, 0x01, 'a', 0x00, 0x00, 0x01, 0x00, 0x01,
+ };
+ for (int i = 0; i < 4; i++) {
+ data.push_back(63);
+ for (int j = 0; j < 63; j++) {
+ data.push_back('a');
+ }
+ }
+ data.push_back(0x00);
+ std::vector<byte> tail = {
+ 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 1, 2, 3, 4,
+ };
+ data.insert(data.end(), tail.begin(), tail.end());
+ ares_dns_record_t *dnsrec = NULL;
+ EXPECT_EQ(ARES_SUCCESS, ares_dns_parse(data.data(), data.size(), 0, &dnsrec));
+ EXPECT_NE(nullptr, dnsrec);
+ ares_dns_record_destroy(dnsrec);
+}
+
+TEST_F(LibraryTest, ParseRejectsName256) {
+ // One octet over: labels 63,63,63,62,1 = 252 + 4 separators = 256 -> reject.
+ std::vector<byte> data = {
+ 0x12, 0x34, 0x81, 0x80, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00,
+ 0x00, 0x00, 0x01, 'a', 0x00, 0x00, 0x01, 0x00, 0x01,
+ };
+ const int lens[] = {63, 63, 63, 62, 1};
+ for (int i = 0; i < 5; i++) {
+ data.push_back(static_cast<byte>(lens[i]));
+ for (int j = 0; j < lens[i]; j++) {
+ data.push_back('a');
+ }
+ }
+ data.push_back(0x00);
+ std::vector<byte> tail = {
+ 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 1, 2, 3, 4,
+ };
+ data.insert(data.end(), tail.begin(), tail.end());
+ ares_dns_record_t *dnsrec = NULL;
+ EXPECT_EQ(ARES_EBADNAME, ares_dns_parse(data.data(), data.size(), 0, &dnsrec));
+ EXPECT_EQ(nullptr, dnsrec);
+}
+
} // namespace test
} // namespace ares
meta-oe/recipes-support/c-ares/c-ares_1.27.0.bb
+1
View File
@@ -8,6 +8,7 @@ LIC_FILES_CHKSUM = "file://LICENSE.md;md5=fdbc58a6da11a9f68aa73c453818decc"
SRC_URI = "https://github.com/c-ares/c-ares/releases/download/cares-1_27_0/${BPN}-${PV}.tar.gz \
file://run-ptest \
file://CVE-2026-69186.patch \
file://CVE-2026-69184.patch \
"
SRC_URI[sha256sum] = "0a72be66959955c43e2af2fbd03418e82a2bd5464604ec9a62147e37aceb420b"