xattr_flags.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 <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <err.h>
  29 #include <errno.h>
  30 #include <sys/types.h>
  31 #include <sys/xattr.h>
  32 #include <dispatch/dispatch.h>
  33 #include <xpc/private.h>
  34
  35 #include <xattr_flags.h>
  36
  37 #define FLAG_DELIM_CHAR '#'
  38 #define FLAG_DELIM_STR "#"
  39
  40 /*
  41  * Some default propeteries for EAs we know about internally.
  42  */
  43 struct defaultList {
  44         const char *eaName;
  45         const char *propList;
  46         int flags;      // See below
  47 };
  48
  49 #define propFlagsPrefix 0x0001  // The name is a prefix, so only look at that part
  50
  51 static const struct defaultList *defaultPropertyTable = NULL;
  52
  53 static const struct defaultList
  54 defaultUnboxedPropertyTable[] = {
  55         { "com.apple.quarantine", "PCS", 0 },   // not public
  56         { "com.apple.TextEncoding", "CS", 0 },  // Content-dependent, public
  57         { "com.apple.metadata:", "PS", propFlagsPrefix },       // Don't export, keep for copy & safe save
  58         { "com.apple.security.", "S", propFlagsPrefix },
  59         { XATTR_RESOURCEFORK_NAME, "PCS", 0 },  // Don't keep for safe save
  60         { XATTR_FINDERINFO_NAME, "PCS", 0 },    // Same as ResourceFork
  61         { "com.apple.root.installed", "PC", 0}, // Don't share or sync. Copyable by entitled callers
  62         { 0, 0, 0 },
  63 };
  64
  65 static const struct defaultList
  66 defaultSandboxedPropertyTable[] = {
  67     { "com.apple.quarantine", "PCS", 0 },       // not public
  68     { "com.apple.TextEncoding", "CS", 0 },      // Content-dependent, public
  69     { "com.apple.metadata:", "PS", propFlagsPrefix },   // Don't export, keep for copy & safe save
  70     { "com.apple.security.", "N", propFlagsPrefix },
  71     { XATTR_RESOURCEFORK_NAME, "PCS", 0 },      // Don't keep for safe save
  72     { XATTR_FINDERINFO_NAME, "PCS", 0 },        // Same as ResourceFork
  73         { "com.apple.root.installed", "PC", 0}, // Don't share or sync. Copyable by entitled callers
  74     { 0, 0, 0 },
  75 };
  76
  77 /*
  78  * The property lists on an EA are set by having a suffix character,
  79  * and then a list of characters.  In general, we're choosing upper-case
  80  * to indicate the property is set, and lower-case to indicate it's to be
  81  * cleared.
  82  */
  83 struct propertyListMapping {
  84         char enable;    // Character to enable
  85         char disable;   // Character to disable -- usually lower-case of enable
  86         xattr_operation_intent_t        value;
  87 };
  88 static const struct propertyListMapping
  89 PropertyListMapTable[] = {
  90         { 'C', 'c', XATTR_FLAG_CONTENT_DEPENDENT },
  91         { 'P', 'p', XATTR_FLAG_NO_EXPORT },
  92         { 'N', 'n', XATTR_FLAG_NEVER_PRESERVE },
  93         { 'S', 's', XATTR_FLAG_SYNCABLE },
  94         { 0, 0, 0 },
  95 };
  96
  97 /*
  98  * Given a converted property list (that is, converted to the
  99  * xattr_operation_intent_t type), and an intent, determine if
 100  * it should be preserved or not.
 101  *
 102  * I've chosen to use a block instead of a simple mask on the belief
 103  * that the question may be moderately complex.  If it ends up not being
 104  * so, then this can simply be turned into a mask of which bits to check
 105  * as being exclusionary.
 106  */
 107 static const struct divineIntent {
 108         xattr_operation_intent_t intent;
 109         int (^checker)(xattr_flags_t);
 110 } intentTable[] = {
 111         { XATTR_OPERATION_INTENT_COPY, ^(xattr_flags_t flags) {
 112                         if (flags & XATTR_FLAG_NEVER_PRESERVE)
 113                                 return 0;
 114                         return 1;
 115                 } },
 116         { XATTR_OPERATION_INTENT_SAVE, ^(xattr_flags_t flags) {
 117                         if (flags & (XATTR_FLAG_CONTENT_DEPENDENT | XATTR_FLAG_NEVER_PRESERVE))
 118                                 return 0;
 119                         return 1;
 120                 } },
 121         { XATTR_OPERATION_INTENT_SHARE, ^(xattr_flags_t flags) {
 122                         if ((flags & (XATTR_FLAG_NO_EXPORT | XATTR_FLAG_NEVER_PRESERVE)) != 0)
 123                                 return 0;
 124                         return 1;
 125                 } },
 126         { XATTR_OPERATION_INTENT_SYNC, ^(xattr_flags_t flags) {
 127                         return (flags & (XATTR_FLAG_SYNCABLE | XATTR_FLAG_NEVER_PRESERVE)) == XATTR_FLAG_SYNCABLE;
 128                 } },
 129         { 0, 0 },
 130 };
 131
 132
 133 /*
 134  * If an EA name is in the default list, find it, and return the property
 135  * list string for it.
 136  */
 137 static const char *
 138 nameInDefaultList(const char *eaname)
 139 {
 140         const struct defaultList *retval;
 141         static dispatch_once_t onceToken;
 142
 143         dispatch_once(&onceToken, ^{
 144                 if (_xpc_runtime_is_app_sandboxed()) {
 145                         defaultPropertyTable = defaultSandboxedPropertyTable;
 146                 } else {
 147                         defaultPropertyTable = defaultUnboxedPropertyTable;
 148                 }
 149         });
 150
 151         for (retval = defaultPropertyTable; retval->eaName; retval++) {
 152                 if ((retval->flags & propFlagsPrefix) != 0 &&
 153                     strncmp(retval->eaName, eaname, strlen(retval->eaName)) == 0)
 154                         return retval->propList;
 155                 if (strcmp(retval->eaName, eaname) == 0)
 156                         return retval->propList;
 157         }
 158         return NULL;
 159 }
 160
 161 /*
 162  * Given an EA name, see if it has a property list in it, and
 163  * return a pointer to it.  All this is doing is looking for
 164  * the delimiter, and returning the string after that.  Returns
 165  * NULL if the delimiter isn't found.  Note that an empty string
 166  * is a valid property list, as far as we're concerned.
 167  */
 168 static const char *
 169 findPropertyList(const char *eaname)
 170 {
 171         const char *ptr = strrchr(eaname, '#');
 172         if (ptr)
 173                 return ptr+1;
 174         return NULL;
 175 }
 176
 177 /*
 178  * Convert a property list string (e.g., "pCd") into a
 179  * xattr_operation_intent_t type.
 180  */
 181 static xattr_operation_intent_t
 182 stringToProperties(const char *proplist)
 183 {
 184         xattr_operation_intent_t retval = 0;
 185         const char *ptr;
 186
 187         // A switch would be more efficient, but less generic.
 188         for (ptr = proplist; *ptr; ptr++) {
 189                 const struct propertyListMapping *mapPtr;
 190                 for (mapPtr = PropertyListMapTable; mapPtr->enable; mapPtr++) {
 191                         if (*ptr == mapPtr->enable) {
 192                                 retval |= mapPtr->value;
 193                         } else if (*ptr == mapPtr->disable) {
 194                                 retval &= ~mapPtr->value;
 195                         }
 196                 }
 197         }
 198         return retval;
 199 }
 200
 201 /*
 202  * Given an EA name (e.g., "com.apple.lfs.hfs.test"), and a
 203  * xattr_operation_intent_t value (it's currently an integral value, so
 204  * just a bitmask), cycle through the list of known properties, and return
 205  * a string with the EA name, and the property list appended.  E.g., we
 206  * might return "com.apple.lfs.hfs.test#pD".
 207  *
 208  * The tricky part of this funciton is that it will not append any letters
 209  * if the value is only the default properites.  In that case, it will copy
 210  * the EA name, and return that.
 211  *
 212  * It returns NULL if there was an error.  The two errors right now are
 213  * no memory (strdup failed), in which case it will set errno to ENOMEM; and
 214  * the resulting EA name is longer than XATTR_MAXNAMELEN, in which case it
 215  * sets errno to ENAMETOOLONG.
 216  *
 217  * (Note that it also uses ENAMETOOLONG if the buffer it's trying to set
 218  * gets too large.  I honestly can't see how that would happen, but it's there
 219  * for sanity checking.  That would require having more than 64 bits to use.)
 220  */
 221 char *
 222 xattr_name_with_flags(const char *orig, xattr_flags_t propList)
 223 {
 224         char *retval = NULL;
 225         char suffix[66] = { 0 }; // 66:  uint64_t for property types, plus '#', plus NUL
 226         char *cur = suffix;
 227         const struct propertyListMapping *mapPtr;
 228
 229         *cur++ = '#';
 230         for (mapPtr = PropertyListMapTable; mapPtr->enable; mapPtr++) {
 231                 if ((propList & mapPtr->value) != 0) {
 232                         *cur++ = mapPtr->enable;
 233                 }
 234                 if (cur >= (suffix + sizeof(suffix))) {
 235                         errno = ENAMETOOLONG;
 236                         return NULL;
 237                 }
 238
 239         }
 240
 241
 242         if (cur == suffix + 1) {
 243                 // No changes made
 244                 retval = strdup(orig);
 245                 if (retval == NULL)
 246                         errno = ENOMEM;
 247         } else {
 248                 const char *defaultEntry = NULL;
 249                 if ((defaultEntry = nameInDefaultList(orig)) != NULL &&
 250                     strcmp(defaultEntry, suffix + 1) == 0) {
 251                         // Just use the name passed in
 252                         retval = strdup(orig);
 253                 } else {
 254                         asprintf(&retval, "%s%s", orig, suffix);
 255                 }
 256                 if (retval == NULL) {
 257                         errno = ENOMEM;
 258                 } else {
 259                         if (strlen(retval) > XATTR_MAXNAMELEN) {
 260                                 free(retval);
 261                                 retval = NULL;
 262                                 errno = ENAMETOOLONG;
 263                         }
 264                 }
 265         }
 266         return retval;
 267 }
 268
 269 char *
 270 xattr_name_without_flags(const char *eaname)
 271 {
 272         char *retval = NULL;
 273         char *tmp;
 274
 275         if ((tmp = strrchr(eaname, FLAG_DELIM_CHAR)) == NULL) {
 276                 retval = strdup(eaname);
 277         } else {
 278                 retval = calloc(tmp - eaname + 1, 1);
 279                 if (retval) {
 280                         strlcpy(retval, eaname, tmp - eaname + 1);
 281                 }
 282         }
 283         if (retval == NULL) {
 284                 errno = ENOMEM;
 285         }
 286         return retval;
 287 }
 288
 289 int
 290 xattr_intent_with_flags(xattr_operation_intent_t intent, xattr_flags_t flags)
 291 {
 292         const struct divineIntent *ip;
 293
 294         for (ip = intentTable; ip->intent; ip++) {
 295                 if (ip->intent == intent) {
 296                         return ip->checker(flags);
 297                 }
 298         }
 299         if ((flags & XATTR_FLAG_NEVER_PRESERVE) != 0)
 300                 return 0;       // Special case, don't try to copy this one
 301
 302         return 1;       // Default
 303 }
 304
 305 xattr_flags_t
 306 xattr_flags_from_name(const char *eaname)
 307 {
 308         xattr_flags_t retval = 0;
 309         const char *propList;
 310
 311         propList = findPropertyList(eaname);
 312         if (propList == NULL) {
 313                 propList = nameInDefaultList(eaname);
 314         }
 315         if (propList != NULL) {
 316                 retval = stringToProperties(propList);
 317         }
 318
 319         return retval;
 320 }
 321
 322 /*
 323  * Indicate whether an EA should be preserved, when using the
 324  * given intent.
 325  *
 326  * This returns 0 if it should not be preserved, and 1 if it should.
 327  *
 328  * It simply looks through the tables we have above, and compares the
 329  * xattr_operation_intent_t for the EA with the intent.  If the
 330  * EA doesn't have any properties, and it's not on the default list, the
 331  * default is to preserve it.
 332  */
 333
 334 int
 335 xattr_preserve_for_intent(const char *eaname, xattr_operation_intent_t intent)
 336 {
 337         xattr_flags_t flags = xattr_flags_from_name(eaname);
 338
 339         return xattr_intent_with_flags(intent, flags);
 340 }
 341
 342 #include "xattr_properties.h"