darwin/_dirhelper.c

   1 /*
   2  * Copyright (c) 2006, 2007, 2010 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 <mach/mach.h>
  25 #include <mach/mach_error.h>
  26 #include <servers/bootstrap.h>
  27 #include <unistd.h>
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <stdbool.h>
  31 #include <membership.h>
  32 #include <pthread.h>
  33 #include <errno.h>
  34 #include <sys/types.h>
  35 #include <sys/stat.h>
  36 #include <sys/param.h>
  37 #include <uuid/uuid.h>
  38 #include <string.h>
  39 #include <libkern/OSByteOrder.h>
  40 #include <TargetConditionals.h>
  41 #include <xpc/xpc.h>
  42 #include <xpc/private.h>
  43
  44 #include "dirhelper.h"
  45 #include "dirhelper_priv.h"
  46
  47 #define BUCKETLEN       2
  48
  49 #define MUTEX_LOCK(x)   if(__is_threaded) pthread_mutex_lock(x)
  50 #define MUTEX_UNLOCK(x) if(__is_threaded) pthread_mutex_unlock(x)
  51
  52 // Use 5 bits per character, to avoid uppercase and shell magic characters
  53 #define ENCODEBITS      5
  54 #define ENCODEDSIZE     ((8 * UUID_UID_SIZE + ENCODEBITS - 1) / ENCODEBITS)
  55 #define MASK(x)         ((1 << (x)) - 1)
  56 #define UUID_UID_SIZE   (sizeof(uuid_t) + sizeof(uid_t))
  57
  58 extern int __is_threaded;
  59
  60 static const mode_t modes[] = {
  61     0755,       /* user */
  62     0700,       /* temp */
  63     0700,       /* cache */
  64 };
  65
  66 static const char *subdirs[] = {
  67     DIRHELPER_TOP_STR,
  68     DIRHELPER_TEMP_STR,
  69     DIRHELPER_CACHE_STR,
  70 };
  71
  72 static pthread_once_t userdir_control = PTHREAD_ONCE_INIT;
  73 static char *userdir = NULL;
  74
  75 // lower case letter (minus vowels), plus numbers and _, making
  76 // 32 characters.
  77 static const char encode[] = "0123456789_bcdfghjklmnpqrstvwxyz";
  78
  79 static void
  80 encode_uuid_uid(const uuid_t uuid, uid_t uid, char *str)
  81 {
  82     unsigned char buf[UUID_UID_SIZE + 1];
  83     unsigned char *bp = buf;
  84     int i;
  85     unsigned int n;
  86
  87     memcpy(bp, uuid, sizeof(uuid_t));
  88     uid = OSSwapHostToBigInt32(uid);
  89     memcpy(bp + sizeof(uuid_t), &uid, sizeof(uid_t));
  90     bp[UUID_UID_SIZE] = 0; // this ensures the last encoded byte will have trailing zeros
  91     for(i = 0; i < ENCODEDSIZE; i++) {
  92         // 5 bits has 8 states
  93         switch(i % 8) {
  94         case 0:
  95             n = *bp++;
  96             *str++ = encode[n >> 3];
  97             break;
  98         case 1:
  99             n = ((n & MASK(3)) << 8) | *bp++;
 100             *str++ = encode[n >> 6];
 101             break;
 102         case 2:
 103             n &= MASK(6);
 104             *str++ = encode[n >> 1];
 105             break;
 106         case 3:
 107             n = ((n & MASK(1)) << 8) | *bp++;
 108             *str++ = encode[n >> 4];
 109             break;
 110         case 4:
 111             n = ((n & MASK(4)) << 8) | *bp++;
 112             *str++ = encode[n >> 7];
 113             break;
 114         case 5:
 115             n &= MASK(7);
 116             *str++ = encode[n >> 2];
 117             break;
 118         case 6:
 119             n = ((n & MASK(2)) << 8) | *bp++;
 120             *str++ = encode[n >> 5];
 121             break;
 122         case 7:
 123             *str++ = encode[n & MASK(5)];
 124             break;
 125         }
 126     }
 127     *str = 0;
 128 }
 129
 130 char *
 131 __user_local_dirname(uid_t uid, dirhelper_which_t which, char *path, size_t pathlen)
 132 {
 133 #if TARGET_OS_EMBEDDED
 134     char *tmpdir;
 135 #else
 136     uuid_t uuid;
 137     char str[ENCODEDSIZE + 1];
 138 #endif
 139     int res;
 140
 141     if(which < 0 || which > DIRHELPER_USER_LOCAL_LAST) {
 142         errno = EINVAL;
 143         return NULL;
 144     }
 145
 146 #if TARGET_OS_EMBEDDED
 147     /* We only support DIRHELPER_USER_LOCAL_TEMP on embedded.
 148      * This interface really doesn't map from OSX to embedded,
 149      * and clients of this interface will need to adapt when
 150      * porting their applications to embedded.
 151      * See: <rdar://problem/7515613>
 152      */
 153     if(which == DIRHELPER_USER_LOCAL_TEMP) {
 154         tmpdir = getenv("TMPDIR");
 155         if(!tmpdir) {
 156             errno = EINVAL;
 157             return NULL;
 158         }
 159         res = snprintf(path, pathlen, "%s", tmpdir);
 160     } else {
 161         errno = EINVAL;
 162         return NULL;
 163     }
 164 #else
 165     res = mbr_uid_to_uuid(uid, uuid);
 166     if(res != 0) {
 167         errno = res;
 168         return NULL;
 169     }
 170
 171     //
 172     // We partition the namespace so that we don't end up with too
 173     // many users in a single directory.  With 1024 buckets, we
 174     // could scale to 1,000,000 users while keeping the average
 175     // number of files in a single directory around 1000
 176     //
 177     encode_uuid_uid(uuid, uid, str);
 178     res = snprintf(path, pathlen,
 179         "%s%.*s/%s/%s",
 180         VAR_FOLDERS_PATH, BUCKETLEN, str, str + BUCKETLEN, subdirs[which]);
 181 #endif
 182     if(res >= pathlen) {
 183         errno = EINVAL;
 184         return NULL; /* buffer too small */
 185     }
 186     return path;
 187 }
 188
 189 char *
 190 __user_local_mkdir_p(char *path)
 191 {
 192     char *next;
 193     int res;
 194
 195     next = path + strlen(VAR_FOLDERS_PATH);
 196     while ((next = strchr(next, '/')) != NULL) {
 197         *next = 0; // temporarily truncate
 198         res = mkdir(path, 0755);
 199         if (res != 0 && errno != EEXIST)
 200             return NULL;
 201         *next++ = '/'; // restore the slash and increment
 202     }
 203     return path;
 204 }
 205
 206 static void userdir_allocate(void)
 207 {
 208     userdir = calloc(PATH_MAX, sizeof(char));
 209 }
 210
 211 /*
 212  * 9407258: Invalidate the dirhelper cache (userdir) of the child after fork.
 213  * There is a rare case when launchd will have userdir set, and child process
 214  * will sometimes inherit this cached value.
 215  */
 216 __private_extern__ void
 217 _dirhelper_fork_child(void)
 218 {
 219     if(userdir) *userdir = 0;
 220 }
 221
 222 __private_extern__ char *
 223 _dirhelper(dirhelper_which_t which, char *path, size_t pathlen)
 224 {
 225     static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
 226     struct stat sb;
 227
 228     if(which < 0 || which > DIRHELPER_USER_LOCAL_LAST) {
 229         errno = EINVAL;
 230         return NULL;
 231     }
 232
 233     if (pthread_once(&userdir_control, userdir_allocate)
 234         || !userdir) {
 235         errno = ENOMEM;
 236         return NULL;
 237     }
 238
 239     if(!*userdir) {
 240         MUTEX_LOCK(&lock);
 241         if (!*userdir) {
 242
 243             if(__user_local_dirname(geteuid(), DIRHELPER_USER_LOCAL, userdir, PATH_MAX) == NULL) {
 244                 MUTEX_UNLOCK(&lock);
 245                 return NULL;
 246             }
 247             /*
 248              * All dirhelper directories are now at the same level, so
 249              * we need to remove the DIRHELPER_TOP_STR suffix to get the
 250              * parent directory.
 251              */
 252             userdir[strlen(userdir) - (sizeof(DIRHELPER_TOP_STR) - 1)] = 0;
 253             /*
 254              * check if userdir exists, and if not, either do the work
 255              * ourself if we are root, or call
 256              * __dirhelper_create_user_local to create it (we have to
 257              * check again afterwards).
 258              */
 259             if(stat(userdir, &sb) < 0) {
 260                 mach_port_t mp;
 261
 262                 if(errno != ENOENT) { /* some unknown error */
 263                     *userdir = 0;
 264                     MUTEX_UNLOCK(&lock);
 265                     return NULL;
 266                 }
 267                 /*
 268                  * If we are root, lets do what dirhelper does for us.
 269                  */
 270                 if (geteuid() == 0) {
 271                     if (__user_local_mkdir_p(userdir) == NULL) {
 272                         *userdir = 0;
 273                         MUTEX_UNLOCK(&lock);
 274                         return NULL;
 275                     }
 276                 } else {
 277                     if(bootstrap_look_up(bootstrap_port, DIRHELPER_BOOTSTRAP_NAME, &mp) != KERN_SUCCESS) {
 278                         errno = EPERM;
 279                     server_error:
 280                         mach_port_deallocate(mach_task_self(), mp);
 281                         MUTEX_UNLOCK(&lock);
 282                         return NULL;
 283                     }
 284                     if(__dirhelper_create_user_local(mp) != KERN_SUCCESS) {
 285                         errno = EPERM;
 286                         goto server_error;
 287                     }
 288                     /* double check that the directory really got created */
 289                     if(stat(userdir, &sb) < 0) {
 290                         goto server_error;
 291                     }
 292                     mach_port_deallocate(mach_task_self(), mp);
 293                 }
 294             }
 295         }
 296         MUTEX_UNLOCK(&lock);
 297     }
 298
 299     if(pathlen < strlen(userdir) + strlen(subdirs[which]) + 1) {
 300         errno = EINVAL;
 301         return NULL; /* buffer too small */
 302     }
 303     strcpy(path, userdir);
 304     strcat(path, subdirs[which]);
 305
 306     /*
 307      * now for subdirectories, create it with the appropriate permissions
 308      * if it doesn't already exist. On OS X, if we're under App Sandbox, we
 309      * rely on xpchelper having created the subdir for us.
 310      */
 311 #if !TARGET_OS_EMBEDDED
 312     if (!_xpc_runtime_is_app_sandboxed())
 313 #endif
 314     if(mkdir(path, modes[which]) != 0 && errno != EEXIST)
 315         return NULL;
 316
 317 #if !TARGET_OS_EMBEDDED
 318     if (_xpc_runtime_is_app_sandboxed()) {
 319         /*
 320          * if xpchelper didn't make the subdir for us, bail since we don't have
 321          * permission to create it ourselves.
 322          */
 323         if(stat(path, &sb) < 0) {
 324             errno = EPERM;
 325             return NULL;
 326         }
 327
 328         /*
 329          * sandboxed applications get per-application directories named
 330          * after the container
 331          */
 332         char *container_id = getenv(XPC_ENV_SANDBOX_CONTAINER_ID);
 333         if(!container_id) {
 334             errno = EINVAL;
 335             return NULL;
 336         }
 337
 338         /*
 339          * container ID doesn't end in a slash, so +2 is for slash and \0
 340          */
 341         if (pathlen < strlen(path) + strlen(container_id) + 2) {
 342             errno = EINVAL;
 343             return NULL; /* buffer too small */
 344         }
 345
 346         strcat(path, container_id);
 347         strcat(path, "/");
 348
 349         /*
 350          * create per-app subdirectory with the appropriate permissions
 351          * if it doesn't already exist.
 352          */
 353         if(mkdir(path, modes[which]) != 0 && errno != EEXIST)
 354             return NULL;
 355     }
 356 #endif
 357
 358     return path;
 359 }