inet/idna.c

   1 /* IDNA functions, forwarding to implementations in libidn2.
   2    Copyright (C) 2018-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <allocate_once.h>
  20 #include <dlfcn.h>
  21 #include <inet/net-internal.h>
  22 #include <netdb.h>
  23 #include <stdbool.h>
  24 #include <pointer_guard.h>
  25
  26 /* Use the soname and version to locate libidn2, to ensure a
  27    compatible ABI.  */
  28 #define LIBIDN2_SONAME "libidn2.so.0"
  29 #define LIBIDN2_VERSION "IDN2_0.0.0"
  30
  31 /* Return codes from libidn2.  */
  32 enum
  33   {
  34     IDN2_OK = 0,
  35     IDN2_MALLOC = -100,
  36   };
  37
  38 /* Functions from libidn2.  */
  39 struct functions
  40 {
  41   void *handle;
  42   int (*lookup_ul) (const char *src, char **result, int flags);
  43   int (*to_unicode_lzlz) (const char *name, char **result, int flags);
  44 };
  45
  46 static void *
  47 functions_allocate (void *closure)
  48 {
  49   struct functions *result = malloc (sizeof (*result));
  50   if (result == NULL)
  51     return NULL;
  52
  53   void *handle = __libc_dlopen (LIBIDN2_SONAME);
  54   if (handle == NULL)
  55     /* Do not cache open failures.  The library may appear
  56        later.  */
  57     {
  58       free (result);
  59       return NULL;
  60     }
  61
  62   void *ptr_lookup_ul
  63     = __libc_dlvsym (handle, "idn2_lookup_ul", LIBIDN2_VERSION);
  64   void *ptr_to_unicode_lzlz
  65     = __libc_dlvsym (handle, "idn2_to_unicode_lzlz", LIBIDN2_VERSION);
  66   if (ptr_lookup_ul == NULL || ptr_to_unicode_lzlz == NULL)
  67     {
  68       __libc_dlclose (handle);
  69       free (result);
  70       return NULL;
  71     }
  72
  73   result->handle = handle;
  74   result->lookup_ul = ptr_lookup_ul;
  75   result->to_unicode_lzlz = ptr_to_unicode_lzlz;
  76   PTR_MANGLE (result->lookup_ul);
  77   PTR_MANGLE (result->to_unicode_lzlz);
  78
  79   return result;
  80 }
  81
  82 static void
  83 functions_deallocate (void *closure, void *ptr)
  84 {
  85   struct functions *functions = ptr;
  86   __libc_dlclose (functions->handle);
  87   free (functions);
  88 }
  89
  90 /* Ensure that *functions is initialized and return the value of the
  91    pointer.  If the library cannot be loaded, return NULL.  */
  92 static inline struct functions *
  93 get_functions (void)
  94 {
  95   static void *functions;
  96   return allocate_once (&functions, functions_allocate, functions_deallocate,
  97                         NULL);
  98 }
  99
 100 /* strdup with an EAI_* error code.  */
 101 static int
 102 gai_strdup (const char *name, char **result)
 103 {
 104   char *ptr = __strdup (name);
 105   if (ptr == NULL)
 106     return EAI_MEMORY;
 107   *result = ptr;
 108   return 0;
 109 }
 110
 111 int
 112 __idna_to_dns_encoding (const char *name, char **result)
 113 {
 114   switch (__idna_name_classify (name))
 115     {
 116     case idna_name_ascii:
 117       /* Nothing to convert.  */
 118       return gai_strdup (name, result);
 119     case idna_name_nonascii:
 120       /* Encoding needed.  Handled below.  */
 121       break;
 122     case idna_name_nonascii_backslash:
 123     case idna_name_encoding_error:
 124       return EAI_IDN_ENCODE;
 125     case idna_name_memory_error:
 126       return EAI_MEMORY;
 127     case idna_name_error:
 128       return EAI_SYSTEM;
 129     }
 130
 131   struct functions *functions = get_functions ();
 132   if (functions == NULL)
 133     /* We report this as an encoding error (assuming that libidn2 is
 134        not installed), although the root cause may be a temporary
 135        error condition due to resource shortage.  */
 136     return EAI_IDN_ENCODE;
 137   char *ptr = NULL;
 138   __typeof__ (functions->lookup_ul) fptr = functions->lookup_ul;
 139   PTR_DEMANGLE (fptr);
 140   int ret = fptr (name, &ptr, 0);
 141   if (ret == 0)
 142     {
 143       /* Assume that idn2_free is equivalent to free.  */
 144       *result = ptr;
 145       return 0;
 146     }
 147   else if (ret == IDN2_MALLOC)
 148     return EAI_MEMORY;
 149   else
 150     return EAI_IDN_ENCODE;
 151 }
 152 libc_hidden_def (__idna_to_dns_encoding)
 153
 154 int
 155 __idna_from_dns_encoding (const char *name, char **result)
 156 {
 157   struct functions *functions = get_functions ();
 158   if (functions == NULL)
 159     /* Simply use the encoded name, assuming that it is not punycode
 160        (but even a punycode name would be syntactically valid).  */
 161     return gai_strdup (name, result);
 162   char *ptr = NULL;
 163   __typeof__ (functions->to_unicode_lzlz) fptr = functions->to_unicode_lzlz;
 164   PTR_DEMANGLE (fptr);
 165   int ret = fptr (name, &ptr, 0);
 166   if (ret == 0)
 167     {
 168       /* Assume that idn2_free is equivalent to free.  */
 169       *result = ptr;
 170       return 0;
 171     }
 172   else if (ret == IDN2_MALLOC)
 173     return EAI_MEMORY;
 174   else
 175     return EAI_IDN_ENCODE;
 176 }
 177 libc_hidden_def (__idna_from_dns_encoding)