darwin/_dirhelper.c

   1 /*
   2  * Copyright (c) 2006, 2007 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
  42 #include "dirhelper.h"
  43 #include "dirhelper_priv.h"
  44
  45 #define BUCKETLEN       2
  46
  47 #define MUTEX_LOCK(x)   if(__is_threaded) pthread_mutex_lock(x)
  48 #define MUTEX_UNLOCK(x) if(__is_threaded) pthread_mutex_unlock(x)
  49
  50 #define ENCODEBITS      6
  51 #define ENCODEDSIZE     ((8 * UUID_UID_SIZE + ENCODEBITS - 1) / ENCODEBITS)
  52 #define UUID_UID_SIZE   (sizeof(uuid_t) + sizeof(uid_t))
  53
  54 extern int __is_threaded;
  55
  56 static const mode_t modes[] = {
  57     0,          /* unused */
  58     0700,       /* temp */
  59     0700,       /* cache */
  60 };
  61
  62 static const char *subdirs[] = {
  63     DIRHELPER_TOP_STR,
  64     DIRHELPER_TEMP_STR,
  65     DIRHELPER_CACHE_STR,
  66 };
  67
  68 static const char encode[] = "+-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  69
  70 static void
  71 encode_uuid_uid(uuid_t uuid, uid_t uid, char *str)
  72 {
  73     unsigned char buf[UUID_UID_SIZE + 1];
  74     unsigned char *bp = buf;
  75     int i = 0;
  76     unsigned int n;
  77
  78     memcpy(bp, uuid, sizeof(uuid_t));
  79     uid = OSSwapHostToBigInt32(uid);
  80     memcpy(bp + sizeof(uuid_t), &uid, sizeof(uid_t));
  81     bp[UUID_UID_SIZE] = 0; // this ensures the last encoded byte will have trailing zeros
  82     while(i < ENCODEDSIZE) {
  83         switch(i % 4) {
  84         case 0:
  85             n = *bp++;
  86             *str++ = encode[n >> 2];
  87             break;
  88         case 1:
  89             n = ((n & 0x3) << 8) | *bp++;
  90             *str++ = encode[n >> 4];
  91             break;
  92         case 2:
  93             n = ((n & 0xf) << 8) | *bp++;
  94             *str++ = encode[n >> 6];
  95             break;
  96         case 3:
  97             *str++ = encode[n & 0x3f];
  98             break;
  99         }
 100         i++;
 101     }
 102     *str = 0;
 103 }
 104
 105 char *
 106 __user_local_dirname(uid_t uid, dirhelper_which_t which, char *path, size_t pathlen)
 107 {
 108 #if TARGET_OS_EMBEDDED
 109     char *tmpdir;
 110 #else
 111     uuid_t uuid;
 112     char str[ENCODEDSIZE + 1];
 113 #endif
 114     int res;
 115
 116     if(which < 0 || which > DIRHELPER_USER_LOCAL_LAST) {
 117         errno = EINVAL;
 118         return NULL;
 119     }
 120
 121 #if TARGET_OS_EMBEDDED
 122     tmpdir = getenv("TMPDIR");
 123     if(!tmpdir) {
 124         errno = EINVAL;
 125         return NULL;
 126     }
 127
 128     res = snprintf(path, pathlen, "%s/%s", tmpdir, subdirs[which]);
 129 #else
 130     res = mbr_uid_to_uuid(uid, uuid);
 131     if(res != 0) {
 132         errno = res;
 133         return NULL;
 134     }
 135
 136     //
 137     // We partition the namespace so that we don't end up with too
 138     // many users in a single directory.  With 4096 buckets, we
 139     // could scale to 1,000,000 users while keeping the average
 140     // number of files in a single directory below 250
 141     //
 142     encode_uuid_uid(uuid, uid, str);
 143     res = snprintf(path, pathlen,
 144         "%s%.*s/%s/%s",
 145         VAR_FOLDERS_PATH, BUCKETLEN, str, str, subdirs[which]);
 146 #endif
 147     if(res >= pathlen) {
 148         errno = EINVAL;
 149         return NULL; /* buffer too small */
 150     }
 151     return path;
 152 }
 153
 154 char *
 155 __user_local_mkdir_p(char *path)
 156 {
 157     char *next;
 158     int res;
 159
 160     next = path + strlen(VAR_FOLDERS_PATH);
 161     while ((next = strchr(next, '/')) != NULL) {
 162         *next = 0; // temporarily truncate
 163         res = mkdir(path, 0755);
 164         if (res != 0 && errno != EEXIST)
 165             return NULL;
 166         *next++ = '/'; // restore the slash and increment
 167     }
 168     return path;
 169 }
 170
 171 __private_extern__ char *
 172 _dirhelper(dirhelper_which_t which, char *path, size_t pathlen)
 173 {
 174     static char userdir[PATH_MAX];
 175     static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
 176     int res;
 177     struct stat sb;
 178
 179     if(which < 0 || which > DIRHELPER_USER_LOCAL_LAST) {
 180         errno = EINVAL;
 181         return NULL;
 182     }
 183
 184     if(!*userdir) {
 185         MUTEX_LOCK(&lock);
 186         if (!*userdir) {
 187
 188             if(__user_local_dirname(geteuid(), DIRHELPER_USER_LOCAL, userdir, sizeof(userdir)) == NULL) {
 189                 MUTEX_UNLOCK(&lock);
 190                 return NULL;
 191             }
 192             /*
 193              * check if userdir exists, and if not, either do the work
 194              * ourself if we are root, or call
 195              * __dirhelper_create_user_local to create it (we have to
 196              * check again afterwards).
 197              */
 198             if(stat(userdir, &sb) < 0) {
 199                 mach_port_t mp;
 200
 201                 if(errno != ENOENT) { /* some unknown error */
 202                     *userdir = 0;
 203                     MUTEX_UNLOCK(&lock);
 204                     return NULL;
 205                 }
 206                 /*
 207                  * If we are root, lets do what dirhelper does for us.
 208                  */
 209                 if (geteuid() == 0) {
 210                     if (__user_local_mkdir_p(userdir) == NULL) {
 211                         *userdir = 0;
 212                         MUTEX_UNLOCK(&lock);
 213                         return NULL;
 214                     }
 215                 } else {
 216                     if(bootstrap_look_up(bootstrap_port, DIRHELPER_BOOTSTRAP_NAME, &mp) != KERN_SUCCESS) {
 217                         errno = EPERM;
 218                     server_error:
 219                         mach_port_deallocate(mach_task_self(), mp);
 220                         MUTEX_UNLOCK(&lock);
 221                         return NULL;
 222                     }
 223                     if(__dirhelper_create_user_local(mp) != KERN_SUCCESS) {
 224                         errno = EPERM;
 225                         goto server_error;
 226                     }
 227                     /* double check that the directory really got created */
 228                     if(stat(userdir, &sb) < 0) {
 229                         goto server_error;
 230                     }
 231                     mach_port_deallocate(mach_task_self(), mp);
 232                 }
 233             }
 234         }
 235         MUTEX_UNLOCK(&lock);
 236     }
 237
 238     if(pathlen < strlen(userdir) + strlen(subdirs[which]) + 1) {
 239         errno = EINVAL;
 240         return NULL; /* buffer too small */
 241     }
 242     strcpy(path, userdir);
 243     strcat(path, subdirs[which]);
 244
 245     /*
 246      * now for subdirectories, create it with the appropriate permissions
 247      * if it doesn't already exist.
 248      */
 249     if(which != DIRHELPER_USER_LOCAL) {
 250         res = mkdir(path, modes[which]);
 251         if(res != 0 && errno != EEXIST)
 252             return NULL;
 253     }
 254
 255     return path;
 256 }