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https://github.com/c-ares/c-ares/issues/683
https://github.com/c-ares/c-ares/commit/626dcb155b4daf3360e4251c64ce052e7e520b34
From 626dcb155b4daf3360e4251c64ce052e7e520b34 Mon Sep 17 00:00:00 2001
From: Brad House <brad@brad-house.com>
Date: Fri, 12 Jan 2024 09:55:42 -0500
Subject: [PATCH] Do not sanity check RR Name vs Question (#685)
It appears as though we should never sanity check the RR name vs the question name as some DNS servers may return results for alias records.
Fixes Bug: #683
Fix By: Brad House (@bradh352)
--- a/src/lib/ares__parse_into_addrinfo.c
+++ b/src/lib/ares__parse_into_addrinfo.c
@@ -81,7 +81,6 @@ ares_status_t ares__parse_into_addrinfo(const unsigned char *abuf, size_t alen,
}
for (i = 0; i < ancount; i++) {
- const char *rname = NULL;
ares_dns_rec_type_t rtype;
const ares_dns_rr_t *rr =
ares_dns_record_rr_get(dnsrec, ARES_SECTION_ANSWER, i);
@@ -91,13 +90,18 @@ ares_status_t ares__parse_into_addrinfo(const unsigned char *abuf, size_t alen,
}
rtype = ares_dns_rr_get_type(rr);
- rname = ares_dns_rr_get_name(rr);
- /* Old code did this hostname sanity check */
- if ((rtype == ARES_REC_TYPE_A || rtype == ARES_REC_TYPE_AAAA) &&
- strcasecmp(rname, hostname) != 0) {
- continue;
- }
+ /* Issue #683
+ * Old code did this hostname sanity check, however it appears this is
+ * flawed logic. Other resolvers don't do this sanity check. Leaving
+ * this code commented out for future reference.
+ *
+ * rname = ares_dns_rr_get_name(rr);
+ * if ((rtype == ARES_REC_TYPE_A || rtype == ARES_REC_TYPE_AAAA) &&
+ * strcasecmp(rname, hostname) != 0) {
+ * continue;
+ * }
+ */
if (rtype == ARES_REC_TYPE_CNAME) {
struct ares_addrinfo_cname *cname;
--- a/src/lib/ares_parse_ptr_reply.c
+++ b/src/lib/ares_parse_ptr_reply.c
@@ -113,7 +113,6 @@ int ares_parse_ptr_reply(const unsigned char *abuf, int alen_int,
/* Cycle through answers */
for (i = 0; i < ancount; i++) {
- const char *rname = NULL;
const ares_dns_rr_t *rr =
ares_dns_record_rr_get(dnsrec, ARES_SECTION_ANSWER, i);
@@ -141,17 +140,20 @@ int ares_parse_ptr_reply(const unsigned char *abuf, int alen_int,
continue;
}
- /* Old code compared the name in the rr to the ptrname, so we'll do that
- * check here, but I'm not sure its necessary */
- rname = ares_dns_rr_get_name(rr);
- if (rname == NULL) {
- /* Shouldn't be possible */
- status = ARES_EBADRESP;
- goto done;
- }
- if (strcasecmp(ptrname, rname) != 0) {
- continue;
- }
+ /* Issue #683
+ * Old code compared the name in the rr to the ptrname, but I think this
+ * is wrong since it was proven wrong for A & AAAA records. Leaving
+ * this code commented out for future reference
+ *
+ * rname = ares_dns_rr_get_name(rr);
+ * if (rname == NULL) {
+ * status = ARES_EBADRESP;
+ * goto done;
+ * }
+ * if (strcasecmp(ptrname, rname) != 0) {
+ * continue;
+ * }
+ */
/* Save most recent PTR record as the hostname */
hostname = ares_dns_rr_get_str(rr, ARES_RR_PTR_DNAME);
--- a/test/ares-test-parse-a.cc
+++ b/test/ares-test-parse-a.cc
@@ -312,13 +312,19 @@ TEST_F(LibraryTest, ParseAReplyErrors) {
EXPECT_EQ(nullptr, host);
pkt.add_question(new DNSQuestion("example.com", T_A));
- // Question != answer
+ // Question != answer, this is ok as of Issue #683
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("Axample.com", T_A));
data = pkt.data();
- EXPECT_EQ(ARES_ENODATA, ares_parse_a_reply(data.data(), (int)data.size(),
+ EXPECT_EQ(ARES_SUCCESS, ares_parse_a_reply(data.data(), (int)data.size(),
&host, info, &count));
- EXPECT_EQ(nullptr, host);
+ ASSERT_NE(nullptr, host);
+ std::stringstream ss;
+ ss << HostEnt(host);
+ EXPECT_EQ("{'Axample.com' aliases=[] addrs=[2.3.4.5]}", ss.str());
+ ares_free_hostent(host);
+ host = nullptr;
+
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("example.com", T_A));
--- a/test/ares-test-parse-aaaa.cc
+++ b/test/ares-test-parse-aaaa.cc
@@ -139,13 +139,19 @@ TEST_F(LibraryTest, ParseAaaaReplyErrors) {
EXPECT_EQ(nullptr, host);
pkt.add_question(new DNSQuestion("example.com", T_AAAA));
- // Question != answer
+ // Question != answer, this is ok as of Issue #683
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("Axample.com", T_AAAA));
data = pkt.data();
- EXPECT_EQ(ARES_ENODATA, ares_parse_aaaa_reply(data.data(), (int)data.size(),
+ EXPECT_EQ(ARES_SUCCESS, ares_parse_aaaa_reply(data.data(), (int)data.size(),
&host, info, &count));
- EXPECT_EQ(nullptr, host);
+ ASSERT_NE(nullptr, host);
+ std::stringstream ss;
+ ss << HostEnt(host);
+ EXPECT_EQ("{'Axample.com' aliases=[] addrs=[0101:0101:0202:0202:0303:0303:0404:0404]}", ss.str());
+ ares_free_hostent(host);
+
+ host = nullptr;
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("example.com", T_AAAA));
--- a/test/ares-test-parse-ptr.cc
+++ b/test/ares-test-parse-ptr.cc
@@ -163,13 +163,20 @@ TEST_F(LibraryTest, ParsePtrReplyErrors) {
addrv4, sizeof(addrv4), AF_INET, &host));
pkt.add_question(new DNSQuestion("64.48.32.16.in-addr.arpa", T_PTR));
- // Question != answer
+ // Question != answer, ok after #683
+ host = nullptr;
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("99.48.32.16.in-addr.arpa", T_PTR));
data = pkt.data();
- EXPECT_EQ(ARES_ENODATA, ares_parse_ptr_reply(data.data(), (int)data.size(),
+ EXPECT_EQ(ARES_SUCCESS, ares_parse_ptr_reply(data.data(), (int)data.size(),
addrv4, sizeof(addrv4), AF_INET, &host));
- EXPECT_EQ(nullptr, host);
+ ASSERT_NE(nullptr, host);
+ std::stringstream ss;
+ ss << HostEnt(host);
+ EXPECT_EQ("{'other.com' aliases=[other.com] addrs=[16.32.48.64]}", ss.str());
+ ares_free_hostent(host);
+
+ host = nullptr;
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("64.48.32.16.in-addr.arpa", T_PTR));
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