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test(dns): extend idn-hostname coverage for Bidi, A-label and ContextJ rules #2489

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test(dns): extend idn-hostname coverage for Bidi, A-label and ContextJ rules #2489

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60 changes: 60 additions & 0 deletions test/dns/idn_hostname_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -593,3 +593,63 @@ TEST(DNS_idn_hostname, label_with_out_of_order_combining_marks_rejected) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname("a\xcc\x81\xcc\x96"));
EXPECT_FALSE(sourcemeta::core::is_hostname("a\xcc\x81\xcc\x96"));
}

// --- additional coverage: subtle cases (whole-name Bidi, A-label
// re-validation, non-canonical Punycode, per-occurrence ContextJ) ---

// RFC 5893 sec 2: a digit-first label is invalid in a Bidi domain name
// (whole-name rule)
TEST(DNS_idn_hostname, invalid_bidi_digit_first_in_bidi_domain) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname("\x30\x61\x2e\xd7\x90"));
}

// RFC 5893 sec 2 cond 1: label must start with L, R or AL
TEST(DNS_idn_hostname, invalid_bidi_single_label_digit_then_rtl) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname("\x30\xd8\xa7"));
}
Comment on lines +602 to +609

// RFC 5893 sec 2 cond 5: an LTR label may not contain an RTL letter
TEST(DNS_idn_hostname, invalid_bidi_ltr_label_with_rtl_letter) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname("\x61\xd7\x90"));
}

// RFC 5890 sec 2.3.2.1 + 5892 sec 2.6: decodes to U+00A1 (DISALLOWED)
TEST(DNS_idn_hostname, invalid_a_label_decodes_to_disallowed) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname("\x78\x6e\x2d\x2d\x37\x61"));

@augmentcode augmentcode Bot Jun 11, 2026 •
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These A-label cases are pure ASCII; since is_hostname() also re-validates xn-- labels via idna_is_valid_a_label, consider asserting EXPECT_FALSE(sourcemeta::core::is_hostname(...)) here as well to pin behavior for the ASCII-only API.

Severity: low

Other Locations
  • test/dns/idn_hostname_test.cc:622
  • test/dns/idn_hostname_test.cc:627
  • test/dns/idn_hostname_test.cc:632

Fix This in Augment

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@cubic-dev-ai cubic-dev-ai Bot Jun 11, 2026

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P3: This A-label is pure ASCII and is_hostname() also validates xn-- labels. Add a corresponding EXPECT_FALSE(sourcemeta::core::is_hostname(...)) assertion here (and for the other A-label tests at lines 622, 627, 632) to pin behavior for the ASCII-only validation path consistently with the pattern used elsewhere in this file.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At test/dns/idn_hostname_test.cc, line 617:

<comment>This A-label is pure ASCII and `is_hostname()` also validates `xn--` labels. Add a corresponding `EXPECT_FALSE(sourcemeta::core::is_hostname(...))` assertion here (and for the other A-label tests at lines 622, 627, 632) to pin behavior for the ASCII-only validation path consistently with the pattern used elsewhere in this file.</comment>

<file context>
@@ -593,3 +593,56 @@ TEST(DNS_idn_hostname, label_with_out_of_order_combining_marks_rejected) {
+
+// RFC 5890 sec 2.3.2.1 + 5892 sec 2.6: decodes to U+00A1 (DISALLOWED)
+TEST(DNS_idn_hostname, invalid_a_label_decodes_to_disallowed) {
+  EXPECT_FALSE(sourcemeta::core::is_idn_hostname("\x78\x6e\x2d\x2d\x37\x61"));
+}
+
</file context>

}

// RFC 5890 sec 2.3.2.1: A-label decodes to the all-ASCII label example
TEST(DNS_idn_hostname, invalid_a_label_decodes_to_ascii_only) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname(
"\x78\x6e\x2d\x2d\x65\x78\x61\x6d\x70\x6c\x65\x2d"));
}

// RFC 5890 sec 2.3.2.1 + 5893: decodes to a-grave + Hebrew aleph
TEST(DNS_idn_hostname, invalid_a_label_decodes_to_bidi_violation) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname(
"\x78\x6e\x2d\x2d\x30\x63\x61\x32\x34\x77"));
}

// RFC 5891 sec 5.4: non-canonical Punycode; canonical form is xn--9uc
TEST(DNS_idn_hostname, invalid_noncanonical_punycode) {
EXPECT_FALSE(
sourcemeta::core::is_idn_hostname("\x78\x6e\x2d\x2d\x2d\x39\x75\x63"));
}
Comment on lines +634 to +637

// RFC 5892 sec 2.6: fullwidth digits U+FF11..U+FF13 are DISALLOWED
TEST(DNS_idn_hostname, invalid_fullwidth_digits) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname(
"\xef\xbc\x91\xef\xbc\x92\xef\xbc\x93"));
}

// RFC 5892 sec 2.6: U+200B (ZERO WIDTH SPACE) is DISALLOWED
TEST(DNS_idn_hostname, invalid_zero_width_space) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname("\x61\xe2\x80\x8b\x62"));
}
Comment on lines +646 to +648

// RFC 5892 appendix A.1 (errata 3312): the ZWNJ rule must hold at every
// occurrence
TEST(DNS_idn_hostname, invalid_zwnj_failing_at_one_occurrence) {
EXPECT_FALSE(sourcemeta::core::is_idn_hostname(
"\xe0\xa4\x95\xe0\xa5\x8d\xe2\x80\x8c\xe0\xa4\xb7\x78\xe2\x80\x8c\x79"));
}
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