commit bb8adbba4f5d9237a144786ba8e504039beff161
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Aug 30 10:02:49 2022 +0200
resolv: Add the __ns_samebinaryname function
During packet parsing, only the binary name is available. If the name
equality check is performed before conversion to text, we can sometimes
skip the last step.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
(cherry picked from commit 394085a34d25a51513019a4dc411acd3527fbd33)
diff --git a/include/arpa/nameser.h b/include/arpa/nameser.h
index 53f1dbc7c3f659e9..bb1dede187cf1500 100644
--- a/include/arpa/nameser.h
+++ b/include/arpa/nameser.h
@@ -55,6 +55,12 @@ int __ns_name_ntop (const unsigned char *, char *, size_t) __THROW;
int __ns_name_unpack (const unsigned char *, const unsigned char *,
const unsigned char *, unsigned char *, size_t) __THROW;
+/* Like ns_samename, but for uncompressed binary names. Return true
+ if the two arguments compare are equal as case-insensitive domain
+ names. */
+_Bool __ns_samebinaryname (const unsigned char *, const unsigned char *)
+ attribute_hidden;
+
#define ns_msg_getflag(handle, flag) \
(((handle)._flags & _ns_flagdata[flag].mask) >> _ns_flagdata[flag].shift)
diff --git a/resolv/Makefile b/resolv/Makefile
index 567f4c2dcf5749df..0b4fa30716af3b8a 100644
--- a/resolv/Makefile
+++ b/resolv/Makefile
@@ -46,6 +46,7 @@ routines := \
ns_name_skip \
ns_name_uncompress \
ns_name_unpack \
+ ns_samebinaryname \
ns_samename \
nsap_addr \
nss_dns_functions \
@@ -107,6 +108,10 @@ tests += \
tests-internal += tst-resolv-txnid-collision
tests-static += tst-resolv-txnid-collision
+# Likewise for __ns_samebinaryname.
+tests-internal += tst-ns_samebinaryname
+tests-static += tst-ns_samebinaryname
+
# These tests need libdl.
ifeq (yes,$(build-shared))
tests += \
diff --git a/resolv/ns_samebinaryname.c b/resolv/ns_samebinaryname.c
new file mode 100644
index 0000000000000000..9a47d8e97a84c759
--- /dev/null
+++ b/resolv/ns_samebinaryname.c
@@ -0,0 +1,55 @@
+/* Compare two binary domain names for quality.
+ Copyright (C) 2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <arpa/nameser.h>
+#include <stdbool.h>
+
+/* Convert ASCII letters to upper case. */
+static inline int
+ascii_toupper (unsigned char ch)
+{
+ if (ch >= 'a' && ch <= 'z')
+ return ch - 'a' + 'A';
+ else
+ return ch;
+}
+
+bool
+__ns_samebinaryname (const unsigned char *a, const unsigned char *b)
+{
+ while (*a != 0 && *b != 0)
+ {
+ if (*a != *b)
+ /* Different label length. */
+ return false;
+ int labellen = *a;
+ ++a;
+ ++b;
+ for (int i = 0; i < labellen; ++i)
+ {
+ if (*a != *b && ascii_toupper (*a) != ascii_toupper (*b))
+ /* Different character in label. */
+ return false;
+ ++a;
+ ++b;
+ }
+ }
+
+ /* Match if both names are at the root label. */
+ return *a == 0 && *b == 0;
+}
diff --git a/resolv/tst-ns_samebinaryname.c b/resolv/tst-ns_samebinaryname.c
new file mode 100644
index 0000000000000000..b06ac610b4cde8be
--- /dev/null
+++ b/resolv/tst-ns_samebinaryname.c
@@ -0,0 +1,62 @@
+/* Test the __ns_samebinaryname function.
+ Copyright (C) 2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <arpa/nameser.h>
+#include <array_length.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <support/check.h>
+
+/* First character denotes the comparison group: All names with the
+ same first character are expected to compare equal. */
+static const char *const cases[] =
+ {
+ " ",
+ "1\001a", "1\001A",
+ "2\002ab", "2\002aB", "2\002Ab", "2\002AB",
+ "3\001a\002ab", "3\001A\002ab",
+ "w\003www\007example\003com", "w\003Www\007Example\003Com",
+ "w\003WWW\007EXAMPLE\003COM",
+ "W\003WWW", "W\003www",
+ };
+
+static int
+do_test (void)
+{
+ for (int i = 0; i < array_length (cases); ++i)
+ for (int j = 0; j < array_length (cases); ++j)
+ {
+ unsigned char *a = (unsigned char *) &cases[i][1];
+ unsigned char *b = (unsigned char *) &cases[j][1];
+ bool actual = __ns_samebinaryname (a, b);
+ bool expected = cases[i][0] == cases[j][0];
+ if (actual != expected)
+ {
+ char a1[NS_MAXDNAME];
+ TEST_VERIFY (ns_name_ntop (a, a1, sizeof (a1)) > 0);
+ char b1[NS_MAXDNAME];
+ TEST_VERIFY (ns_name_ntop (b, b1, sizeof (b1)) > 0);
+ printf ("error: \"%s\" \"%s\": expected %s\n",
+ a1, b1, expected ? "equal" : "unqueal");
+ support_record_failure ();
+ }
+ }
+ return 0;
+}
+
+#include <support/test-driver.c>