commit c0a25aa92b612786f4e45292c4aee1d7d47123f8

Author: Florian Weimer <fweimer@redhat.com>

Date:   Sat Nov 11 11:51:08 2017 +0100

    resolv: More precise checks in res_hnok, res_dnok [BZ #22409] [BZ #22412]

    res_hnok rejected some host names used on the Internet, such as

    www-.example.com.  res_hnok and res_dnok failed to perform basic syntax

    checking on DNS domain names.

    Also fix res_mailok, res_ownok.

diff --git a/resolv/res_comp.c b/resolv/res_comp.c

index ffb2ed59147d3680..79760e891f607daa 100644

--- a/resolv/res_comp.c

+++ b/resolv/res_comp.c

@@ -1,3 +1,21 @@

+/* Domain name processing functions.

+   Copyright (C) 1995-2017 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

+   <http://www.gnu.org/licenses/>.  */

+

 /*

  * Copyright (c) 1985, 1993

  *    The Regents of the University of California.  All rights reserved.

@@ -121,110 +139,118 @@ dn_skipname(const u_char *ptr, const u_char *eom) {

 }

 libresolv_hidden_def (dn_skipname)

-/*

- * Verify that a domain name uses an acceptable character set.

- */

+/* Return true if the string consists of printable ASCII characters

+   only.  */

+static bool

+printable_string (const char *dn)

+{

+  while (true)

+    {

+      char ch = *dn;

+      if (ch == '\0')

+	return true;

+      if (ch <= ' ' || ch > '~')

+	return false;

+      ++dn;

+    }

+}

-/*

- * Note the conspicuous absence of ctype macros in these definitions.  On

- * non-ASCII hosts, we can't depend on string literals or ctype macros to

- * tell us anything about network-format data.  The rest of the BIND system

- * is not careful about this, but for some reason, we're doing it right here.

- */

-#define PERIOD 0x2e

-#define	hyphenchar(c) ((c) == 0x2d)

-#define	underscorechar(c) ((c) == 0x5f)

-#define bslashchar(c) ((c) == 0x5c)

-#define periodchar(c) ((c) == PERIOD)

-#define asterchar(c) ((c) == 0x2a)

-#define alphachar(c) (((c) >= 0x41 && (c) <= 0x5a) \

-		   || ((c) >= 0x61 && (c) <= 0x7a))

-#define digitchar(c) ((c) >= 0x30 && (c) <= 0x39)

-

-#define borderchar(c) (alphachar(c) || digitchar(c))

-#define middlechar(c) (borderchar(c) || hyphenchar(c) || underscorechar(c))

-#define	domainchar(c) ((c) > 0x20 && (c) < 0x7f)

+/* Return true if DN points to a name consisting only of [0-9a-zA-Z_-]

+   characters.  DN must be in DNS wire format, without

+   compression.  */

+static bool

+binary_hnok (const unsigned char *dn)

+{

+  while (true)

+    {

+      size_t label_length = *dn;

+      if (label_length == 0)

+	break;

+      ++dn;

+      const unsigned char *label_end = dn + label_length;

+      do

+	{

+	  unsigned char ch = *dn;

+	  if (!(('0' <= ch && ch <= '9')

+		|| ('A' <= ch && ch <= 'Z')

+		|| ('a' <= ch && ch <= 'z')

+		|| ch == '-' || ch == '_'))

+	    return false;

+	  ++dn;

+	}

+      while (dn < label_end);

+    }

+  return true;

+}

+

+/* Return true if the binary domain name has a first labels which

+   starts with '-'.  */

+static inline bool

+binary_leading_dash (const unsigned char *dn)

+{

+  return dn[0] > 0 && dn[1] == '-';

+}

+/* Return 1 if res_hnok is a valid host name.  Labels must only

+   contain [0-9a-zA-Z_-] characters, and the name must not start with

+   a '-'.  The latter is to avoid confusion with program options.  */

 int

-res_hnok(const char *dn) {

-	int pch = PERIOD, ch = *dn++;

-

-	while (ch != '\0') {

-		int nch = *dn++;

-

-		if (periodchar(ch)) {

-			(void)NULL;

-		} else if (periodchar(pch)) {

-			if (!borderchar(ch))

-				return (0);

-		} else if (periodchar(nch) || nch == '\0') {

-			if (!borderchar(ch))

-				return (0);

-		} else {

-			if (!middlechar(ch))

-				return (0);

-		}

-		pch = ch, ch = nch;

-	}

-	return (1);

+res_hnok (const char *dn)

+{

+  unsigned char buf[NS_MAXCDNAME];

+  if (!printable_string (dn)

+      || ns_name_pton (dn, buf, sizeof (buf)) < 0

+      || binary_leading_dash (buf))

+    return 0;

+  return binary_hnok (buf);

 }

 libresolv_hidden_def (res_hnok)

-/*

- * hostname-like (A, MX, WKS) owners can have "*" as their first label

- * but must otherwise be as a host name.

- */

+/* Hostname-like (A, MX, WKS) owners can have "*" as their first label

+   but must otherwise be as a host name.  */

 int

-res_ownok(const char *dn) {

-	if (asterchar(dn[0])) {

-		if (periodchar(dn[1]))

-			return (res_hnok(dn+2));

-		if (dn[1] == '\0')

-			return (1);

-	}

-	return (res_hnok(dn));

+res_ownok (const char *dn)

+{

+  unsigned char buf[NS_MAXCDNAME];

+  if (!printable_string (dn)

+      || ns_name_pton (dn, buf, sizeof (buf)) < 0

+      || binary_leading_dash (buf))

+    return 0;

+  if (buf[0] == 1 && buf [1] == '*')

+    /* Skip over the leading "*." part.  */

+    return binary_hnok (buf + 2);

+  else

+    return binary_hnok (buf);

 }

-/*

- * SOA RNAMEs and RP RNAMEs can have any printable character in their first

- * label, but the rest of the name has to look like a host name.

- */

+/* SOA RNAMEs and RP RNAMEs can have any byte in their first label,

+   but the rest of the name has to look like a host name.  */

 int

-res_mailok(const char *dn) {

-	int ch, escaped = 0;

-

-	/* "." is a valid missing representation */

-	if (*dn == '\0')

-		return (1);

-

-	/* otherwise <label>.<hostname> */

-	while ((ch = *dn++) != '\0') {

-		if (!domainchar(ch))

-			return (0);

-		if (!escaped && periodchar(ch))

-			break;

-		if (escaped)

-			escaped = 0;

-		else if (bslashchar(ch))

-			escaped = 1;

-	}

-	if (periodchar(ch))

-		return (res_hnok(dn));

-	return (0);

+res_mailok (const char *dn)

+{

+  unsigned char buf[NS_MAXCDNAME];

+  if (!printable_string (dn)

+      || ns_name_pton (dn, buf, sizeof (buf)) < 0)

+    return 0;

+  unsigned char label_length = buf[0];

+  /* "." is a valid missing representation */

+  if (label_length == 0)

+    return 1;

+  /* Skip over the first label.  */

+  unsigned char *tail = buf + 1 + label_length;

+  if (*tail == 0)

+    /* More than one label is required (except for ".").  */

+    return 0;

+  return binary_hnok (tail);

 }

-/*

- * This function is quite liberal, since RFC 1034's character sets are only

- * recommendations.

- */

+/* Return 1 if DN is a syntactically valid domain name.  Empty names

+   are accepted.  */

 int

-res_dnok(const char *dn) {

-	int ch;

-

-	while ((ch = *dn++) != '\0')

-		if (!domainchar(ch))

-			return (0);

-	return (1);

+res_dnok (const char *dn)

+{

+  unsigned char buf[NS_MAXCDNAME];

+  return printable_string (dn) && ns_name_pton (dn, buf, sizeof (buf)) >= 0;

 }

 libresolv_hidden_def (res_dnok)

diff --git a/resolv/tst-res_hnok.c b/resolv/tst-res_hnok.c

index 9c923038218e965c..314477a2ce2661c0 100644

--- a/resolv/tst-res_hnok.c

+++ b/resolv/tst-res_hnok.c

@@ -51,19 +51,31 @@ static const struct test_case tests[] =

   {

     { "", allok },

     { ".", allok },

+    { "..", 0 },

     { "www", allnomailok },

+    { "www.", allnomailok },

     { "example", allnomailok },

     { "example.com", allok },

     { "www.example.com", allok },

     { "www.example.com.", allok },

+    { "www-.example.com.", allok },

+    { "www.-example.com.", allok },

     { "*.example.com", dnok | mailok | ownok },

     { "-v", dnok },

     { "-v.example.com", mailok | dnok },

     { "**.example.com", dnok | mailok },

+    { "www.example.com\\", 0 },

     { STRING63, allnomailok },

+    { STRING63 ".", allnomailok },

+    { STRING63 "\\.", 0 },

+    { STRING63 "z", 0 },

     { STRING63 ".example.com", allok },

     { STRING63 "." STRING63 "." STRING63 "." STRING60 "z", allok },

+    { STRING63 "." STRING63 "." STRING63 "." STRING60 "z.", allok },

+    { STRING63 "." STRING63 "." STRING63 "." STRING60 "zz", 0 },

+    { STRING63 "." STRING63 "." STRING63 "." STRING60 "zzz", 0 },

     { "hostmaster@mail.example.com", dnok | mailok },

+    { "hostmaster\\@mail.example.com", dnok | mailok },

     { "with whitespace", 0 },

     { "with\twhitespace", 0 },

     { "with\nwhitespace", 0 },

@@ -116,6 +128,12 @@ one_char (const char *prefix, const char *accepted, const char *suffix,

     }

 }

+#define LETTERSDIGITS \

+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

+

+#define PRINTABLE \

+  "!\"#$%&'()*+,/:;<=>?@[\\]^`{|}~"

+

 static int

 do_test (void)

 {

@@ -131,20 +149,18 @@ do_test (void)

     }

   one_char

-    ("", "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.",

-     "", "res_hnok", res_hnok);

+    ("", LETTERSDIGITS "._", "", "res_hnok", res_hnok);

   one_char

     ("middle",

-     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-_",

+     LETTERSDIGITS ".-_\\", /* "middle\\suffix" == "middlesuffix", so good.  */

      "suffix", "res_hnok", res_hnok);

   one_char

     ("middle",

-     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-_"

-     "!\"#$%&'()*+,/:;<=>?@[\\]^`{|}~",

+     LETTERSDIGITS ".-_" PRINTABLE,

      "suffix.example", "res_mailok", res_mailok);

   one_char

     ("mailbox.middle",

-     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-_",

+     LETTERSDIGITS ".-_\\",

      "suffix.example", "res_mailok", res_mailok);

   return 0;