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