src/resolve/resolved-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include "dns-def.h"
   4 #include "dns-domain.h"
   5 #include "hostname-util.h"
   6 #include "idn-util.h"
   7 #include "resolved-util.h"
   8 #include "utf8.h"
   9
  10 int resolve_system_hostname(char **full_hostname, char **first_label) {
  11         _cleanup_free_ char *h = NULL, *n = NULL;
  12 #if HAVE_LIBIDN2
  13         _cleanup_free_ char *utf8 = NULL;
  14 #elif HAVE_LIBIDN
  15         int k;
  16 #endif
  17         char label[DNS_LABEL_MAX];
  18         const char *p, *decoded;
  19         int r;
  20
  21         /* Return the full hostname in *full_hostname, if nonnull.
  22          *
  23          * Extract and normalize the first label of the locally configured hostname, check it's not
  24          * "localhost", and return it in *first_label, if nonnull. */
  25
  26         r = gethostname_strict(&h);
  27         if (r < 0)
  28                 return log_debug_errno(r, "Can't determine system hostname: %m");
  29
  30         p = h;
  31         r = dns_label_unescape(&p, label, sizeof label, 0);
  32         if (r < 0)
  33                 return log_debug_errno(r, "Failed to unescape hostname: %m");
  34         if (r == 0)
  35                 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
  36                                        "Couldn't find a single label in hostname.");
  37
  38 #if HAVE_LIBIDN || HAVE_LIBIDN2
  39         r = dlopen_idn();
  40         if (r < 0) {
  41                 log_debug_errno(r, "Failed to initialize IDN support, ignoring: %m");
  42                 decoded = label; /* no decoding */
  43         } else
  44 #endif
  45         {
  46 #if HAVE_LIBIDN2
  47                 r = sym_idn2_to_unicode_8z8z(label, &utf8, 0);
  48                 if (r != IDN2_OK)
  49                         return log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN),
  50                                                "Failed to undo IDNA: %s", sym_idn2_strerror(r));
  51                 assert(utf8_is_valid(utf8));
  52
  53                 r = strlen(utf8);
  54                 decoded = utf8;
  55 #elif HAVE_LIBIDN
  56                 k = dns_label_undo_idna(label, r, label, sizeof label);
  57                 if (k < 0)
  58                         return log_debug_errno(k, "Failed to undo IDNA: %m");
  59                 if (k > 0)
  60                         r = k;
  61
  62                 if (!utf8_is_valid(label))
  63                         return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
  64                                                "System hostname is not UTF-8 clean.");
  65                 decoded = label;
  66 #else
  67                 decoded = label; /* no decoding */
  68 #endif
  69         }
  70
  71         r = dns_label_escape_new(decoded, r, &n);
  72         if (r < 0)
  73                 return log_debug_errno(r, "Failed to escape hostname: %m");
  74
  75         if (is_localhost(n))
  76                 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
  77                                        "System hostname is 'localhost', ignoring.");
  78
  79         if (full_hostname)
  80                 *full_hostname = TAKE_PTR(h);
  81         if (first_label)
  82                 *first_label = TAKE_PTR(n);
  83         return 0;
  84 }