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