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Empty TXT records were not being preserved (#922)

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When parsing, preserve empty TXT records.

Fixes #921
Fix-By: Brad House (@bradh352)
v1.32
Brad House 2 weeks ago
parent 42469b0b11
commit b335522ce7
3 changed files with 75 additions and 29 deletions
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  1. 8
      src/lib/ares__buf.c
  2. 11
      src/lib/ares_dns_multistring.c
  3. 47
      test/ares-test-parse-txt.cc

8
src/lib/ares__buf.c
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@ -971,10 +971,10 @@ ares_status_t ares__buf_parse_dns_abinstr(ares__buf_t *buf,
break; /* LCOV_EXCL_LINE: DefensiveCoding */
}
if (len) {
/* When used by the _str() parser, it really needs to be validated to
* be a valid printable ascii string. Do that here */
if (validate_printable && ares__buf_len(buf) >= len) {
if (len && validate_printable && ares__buf_len(buf) >= len) {
size_t mylen;
const char *data = (const char *)ares__buf_peek(buf, &mylen);
if (!ares__str_isprint(data, len)) {
@ -985,10 +985,12 @@ ares_status_t ares__buf_parse_dns_abinstr(ares__buf_t *buf,
if (strs != NULL) {
unsigned char *data = NULL;
if (len) {
status = ares__buf_fetch_bytes_dup(buf, len, ARES_TRUE, &data);
if (status != ARES_SUCCESS) {
break;
}
}
status = ares__dns_multistring_add_own(*strs, data, len);
if (status != ARES_SUCCESS) {
ares_free(data);
@ -1000,7 +1002,7 @@ ares_status_t ares__buf_parse_dns_abinstr(ares__buf_t *buf,
break;
}
}
}
}
if (status != ARES_SUCCESS && strs != NULL) {

11
src/lib/ares_dns_multistring.c
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@ -138,6 +138,17 @@ ares_status_t ares__dns_multistring_add_own(ares__dns_multistring_t *strs,
strs->alloc = newalloc;
}
/* Issue #921, ares_dns_multistring_get() doesn't have a way to indicate
* success or fail on a zero-length string which is actually valid. So we
* are going to allocate a 1-byte buffer to use as a placeholder in this
* case */
if (str == NULL) {
str = ares_malloc_zero(1);
if (str == NULL) {
return ARES_ENOMEM;
}
}
strs->strs[strs->cnt].data = str;
strs->strs[strs->cnt].len = len;
strs->cnt++;

47
test/ares-test-parse-txt.cc vendored
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@ -38,7 +38,7 @@ TEST_F(LibraryTest, ParseTxtReplyOK) {
std::string expected2a = "txt2a";
std::string expected2b("ABC\0ABC", 7);
pkt.set_qid(0x1234).set_response().set_aa()
.add_question(new DNSQuestion("example.com", T_MX))
.add_question(new DNSQuestion("example.com", T_TXT))
.add_answer(new DNSTxtRR("example.com", 100, {expected1}))
.add_answer(new DNSTxtRR("example.com", 100, {expected2a, expected2b}));
std::vector<byte> data = pkt.data();
@ -68,7 +68,7 @@ TEST_F(LibraryTest, ParseTxtExtReplyOK) {
std::string expected2a = "txt2a";
std::string expected2b("ABC\0ABC", 7);
pkt.set_qid(0x1234).set_response().set_aa()
.add_question(new DNSQuestion("example.com", T_MX))
.add_question(new DNSQuestion("example.com", T_TXT))
.add_answer(new DNSTxtRR("example.com", 100, {expected1}))
.add_answer(new DNSTxtRR("example.com", 100, {expected2a, expected2b}));
std::vector<byte> data = pkt.data();
@ -95,6 +95,39 @@ TEST_F(LibraryTest, ParseTxtExtReplyOK) {
ares_free_data(txt);
}
TEST_F(LibraryTest, ParseTxtEmpty) {
DNSPacket pkt;
std::string expected1 = "";
pkt.set_qid(0x1234).set_response().set_aa()
.add_question(new DNSQuestion("example.com", T_TXT))
.add_answer(new DNSTxtRR("example.com", 100, {expected1}));
std::vector<byte> data = pkt.data();
ares_dns_record_t *dnsrec = NULL;
ares_dns_rr_t *rr = NULL;
EXPECT_EQ(ARES_SUCCESS, ares_dns_parse(data.data(), data.size(), 0, &dnsrec));
EXPECT_EQ(1, ares_dns_record_rr_cnt(dnsrec, ARES_SECTION_ANSWER));
rr = ares_dns_record_rr_get(dnsrec, ARES_SECTION_ANSWER, 0);
ASSERT_NE(nullptr, rr);
EXPECT_EQ(ARES_REC_TYPE_TXT, ares_dns_rr_get_type(rr));
size_t txtdata_len;
const unsigned char *txtdata;
/* Using array methodology */
EXPECT_EQ(1, ares_dns_rr_get_abin_cnt(rr, ARES_RR_TXT_DATA));
txtdata = ares_dns_rr_get_abin(rr, ARES_RR_TXT_DATA, 0, &txtdata_len);
EXPECT_EQ(txtdata_len, 0);
EXPECT_NE(nullptr, txtdata);
/* Using combined methodology */
txtdata = ares_dns_rr_get_bin(rr, ARES_RR_TXT_DATA, &txtdata_len);
EXPECT_EQ(txtdata_len, 0);
EXPECT_NE(nullptr, txtdata);
ares_dns_record_destroy(dnsrec); dnsrec = NULL;
}
TEST_F(LibraryTest, ParseTxtMalformedReply1) {
std::vector<byte> data = {
0x12, 0x34, // qid
@ -213,7 +246,7 @@ TEST_F(LibraryTest, ParseTxtReplyErrors) {
std::string expected2a = "txt2a";
std::string expected2b = "txt2b";
pkt.set_qid(0x1234).set_response().set_aa()
.add_question(new DNSQuestion("example.com", T_MX))
.add_question(new DNSQuestion("example.com", T_TXT))
.add_answer(new DNSTxtRR("example.com", 100, {expected1}))
.add_answer(new DNSTxtRR("example.com", 100, {expected1}))
.add_answer(new DNSTxtRR("example.com", 100, {expected2a, expected2b}));
@ -227,7 +260,7 @@ TEST_F(LibraryTest, ParseTxtReplyErrors) {
txt = nullptr;
EXPECT_EQ(ARES_EBADRESP, ares_parse_txt_reply(data.data(), (int)data.size(), &txt));
EXPECT_EQ(nullptr, txt);
pkt.add_question(new DNSQuestion("example.com", T_MX));
pkt.add_question(new DNSQuestion("example.com", T_TXT));
#ifdef DISABLED
// Question != answer
@ -240,13 +273,13 @@ TEST_F(LibraryTest, ParseTxtReplyErrors) {
#endif
// Two questions.
pkt.add_question(new DNSQuestion("example.com", T_MX));
pkt.add_question(new DNSQuestion("example.com", T_TXT));
data = pkt.data();
txt = nullptr;
EXPECT_EQ(ARES_EBADRESP, ares_parse_txt_reply(data.data(), (int)data.size(), &txt));
EXPECT_EQ(nullptr, txt);
pkt.questions_.clear();
pkt.add_question(new DNSQuestion("example.com", T_MX));
pkt.add_question(new DNSQuestion("example.com", T_TXT));
// No answer.
pkt.answers_.clear();
@ -274,7 +307,7 @@ TEST_F(LibraryTest, ParseTxtReplyAllocFail) {
std::string expected2a = "txt2a";
std::string expected2b = "txt2b";
pkt.set_qid(0x1234).set_response().set_aa()
.add_question(new DNSQuestion("example.com", T_MX))
.add_question(new DNSQuestion("example.com", T_TXT))
.add_answer(new DNSCnameRR("example.com", 300, "c.example.com"))
.add_answer(new DNSTxtRR("c.example.com", 100, {expected1}))
.add_answer(new DNSTxtRR("c.example.com", 100, {expected1}))

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