tzlinkd/tzlinkd.c

   1 /*
   2  * Copyright (c) 2013 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #include <xpc/xpc.h>
  25 #include <xpc/private.h>
  26 #include <notify.h>
  27 #include <tzfile.h>
  28
  29 #include "tzlink_internal.h"
  30
  31 static bool peer_entitled(xpc_connection_t);
  32 static int set_timezone(const char *);
  33 static int build_source_path(char *, size_t, const char *);
  34 static int validate_source_path(const char *);
  35
  36 int
  37 main(void)
  38 {
  39         dispatch_queue_t queue;
  40         xpc_connection_t listener;
  41
  42         xpc_track_activity();
  43
  44         queue = dispatch_queue_create(TZLINK_SERVICE_NAME, NULL);
  45
  46         listener = xpc_connection_create_mach_service(TZLINK_SERVICE_NAME, queue, XPC_CONNECTION_MACH_SERVICE_LISTENER);
  47         xpc_connection_set_event_handler(listener, ^(xpc_object_t peer) {
  48                 if (xpc_get_type(peer) != XPC_TYPE_CONNECTION) {
  49                         return;
  50                 }
  51
  52                 xpc_connection_set_target_queue(peer, queue);
  53                 xpc_connection_set_event_handler(peer, ^(xpc_object_t request) {
  54                         xpc_object_t reply;
  55                         const char *tz;
  56                         int error;
  57
  58                         if (xpc_get_type(request) != XPC_TYPE_DICTIONARY) {
  59                                 return;
  60                         }
  61
  62                         if (peer_entitled(peer)) {
  63                                 tz = xpc_dictionary_get_string(request, TZLINK_KEY_REQUEST_TIMEZONE);
  64                                 error = tz ? set_timezone(tz) : EINVAL;
  65                         } else {
  66                                 error = EPERM;
  67                         }
  68
  69                         reply = xpc_dictionary_create_reply(request);
  70                         xpc_dictionary_set_uint64(reply, TZLINK_KEY_REPLY_ERROR, (uint64_t)error);
  71                         xpc_connection_send_message(peer, reply);
  72                         xpc_release(reply);
  73                 });
  74                 xpc_connection_resume(peer);
  75         });
  76         xpc_connection_resume(listener);
  77
  78         dispatch_main();
  79 }
  80
  81 static bool
  82 peer_entitled(xpc_connection_t peer)
  83 {
  84         xpc_object_t val;
  85         bool entitled;
  86
  87         entitled = false;
  88
  89         val = xpc_connection_copy_entitlement_value(peer, TZLINK_ENTITLEMENT);
  90         if (val != NULL) {
  91                 entitled = xpc_bool_get_value(val);
  92                 xpc_release(val);
  93         }
  94
  95         return entitled;
  96 }
  97
  98 static int
  99 set_timezone(const char *tz)
 100 {
 101         char srcpath[PATH_MAX];
 102         int error;
 103
 104         error = build_source_path(srcpath, sizeof(srcpath), tz);
 105         if (error != 0) {
 106                 return error;
 107         }
 108
 109         error = validate_source_path(srcpath);
 110         if (error != 0) {
 111                 return error;
 112         }
 113
 114         (void)unlink(TZDEFAULT);
 115         if (symlink(srcpath, TZDEFAULT) != 0) {
 116                 return errno ? errno : EFAULT;
 117         }
 118
 119         /*
 120          * notifyd posts "com.apple.system.timezone" automatically,
 121          * but we also need post this. Sigh.
 122          */
 123         (void)notify_post("SignificantTimeChangeNotification");
 124
 125         return 0;
 126 }
 127
 128 /* Create path from input. */
 129 static int
 130 build_source_path(char *path, size_t size, const char *tz)
 131 {
 132         char *str, *str0;
 133         char *pathcomp;
 134         int error;
 135
 136         if (strlcpy(path, TZDIR, size) >= size) {
 137                 return ENAMETOOLONG;
 138         }
 139
 140         error = 0;
 141
 142         /* Attempt to validate the input; construct a clean path as we go. */
 143         str0 = str = strdup(tz);
 144         while ((pathcomp = strsep(&str, "/")) != NULL) {
 145                 if (pathcomp[0] == '\0' || pathcomp[0] == '.') {
 146                         error = EINVAL;
 147                         break;
 148                 }
 149                 if (strlcat(path, "/", size) >= size) {
 150                         error = ENAMETOOLONG;
 151                         break;
 152                 }
 153                 if (strlcat(path, pathcomp, size) >= size) {
 154                         error = ENAMETOOLONG;
 155                         break;
 156                 }
 157         }
 158         free(str0);
 159
 160         return error;
 161 }
 162
 163 /* Validate path. */
 164 static int
 165 validate_source_path(const char *path)
 166 {
 167         struct stat sb;
 168
 169         if (lstat(path, &sb) != 0) {
 170                 return errno ? errno : EFAULT;
 171         }
 172
 173         /* Ensure that the time zone file is... */
 174
 175         /* ... a regular file. */
 176         if (!S_ISREG(sb.st_mode)) {
 177                 return ENOENT;
 178         }
 179
 180         /* ... owned by root:wheel */
 181         if (sb.st_uid != 0 || sb.st_gid != 0) {
 182                 return ENOENT;
 183         }
 184
 185         /* ... 0644 perms */
 186         if ((sb.st_mode & ACCESSPERMS) != 0644) {
 187                 return ENOENT;
 188         }
 189
 190         /* ... is a real tzfile (starts with TZif) */
 191         // TODO: Validate contents of file.
 192
 193         return 0;
 194 }