keychain/ckks/CKKSItemEncrypter.m

   1 /*
   2  * Copyright (c) 2016 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 <AssertMacros.h>
  25 #import <Foundation/Foundation.h>
  26 #import <CoreFoundation/CoreFoundation.h>
  27 #import <CoreFoundation/CFPropertyList_Private.h>
  28
  29 #include <securityd/SecItemSchema.h>
  30
  31 #import "CKKSItemEncrypter.h"
  32 #import "CKKSKeychainView.h"
  33
  34 #import "CKKSOutgoingQueueEntry.h"
  35 #import "CKKSKey.h"
  36 #import "CKKSItem.h"
  37
  38 #if OCTAGON
  39
  40 @implementation CKKSItemEncrypter
  41
  42 // Make it harder to distinguish password lengths especially when password is short.
  43 + (NSData *)padData:(NSData * _Nonnull)input blockSize:(NSUInteger)blockSize additionalBlock:(BOOL)extra {
  44     // Must apply padding otherwise unpadding will choke
  45     if (blockSize == 0) {
  46         blockSize = 1;
  47         secwarning("CKKS padding function received invalid blocksize 0, using 1 instead");
  48     }
  49     NSMutableData *data = [NSMutableData dataWithData:input];
  50     NSUInteger paddingLength = blockSize - (data.length % blockSize);
  51         // Short password as determined by caller: make sure there's at least one block of padding
  52         if (extra) {
  53                 paddingLength += blockSize;
  54         }
  55     [data appendData:[NSMutableData dataWithLength:paddingLength]];
  56     uint8_t *bytes = [data mutableBytes];
  57     bytes[data.length - paddingLength] = CKKS_PADDING_MARK_BYTE;
  58     return data;
  59 }
  60
  61 + (NSData *)removePaddingFromData:(NSData * _Nonnull)input {
  62     size_t len = input.length;
  63     uint8_t const *bytes = [input bytes];
  64     size_t idx = len;
  65     while (idx > 0) {
  66         idx -= 1;
  67         switch(bytes[idx]) {
  68             case 0:
  69                 continue;
  70             case CKKS_PADDING_MARK_BYTE:
  71                 return [input subdataWithRange:NSMakeRange(0, idx)];
  72             default:
  73                 return nil;
  74         }
  75     }
  76     return nil;
  77 }
  78
  79 +(CKKSItem*)encryptCKKSItem:(CKKSItem*)baseitem
  80              dataDictionary:(NSDictionary *)dict
  81            updatingCKKSItem:(CKKSItem*)olditem
  82                   parentkey:(CKKSKey *)parentkey
  83                       error:(NSError * __autoreleasing *) error
  84 {
  85     CKKSKey *itemkey = nil;
  86
  87     // If we're updating a CKKSItem, extract its dictionary and overlay our new one on top
  88     if(olditem) {
  89         NSMutableDictionary* oldDictionary = [[CKKSItemEncrypter decryptItemToDictionary: olditem error:error] mutableCopy];
  90         if(!oldDictionary) {
  91             secerror("Couldn't decrypt old CKMirror entry: %@", (error ? *error : @"null error passed in"));
  92             return nil;
  93         }
  94
  95         // Use oldDictionary as a base, and copy in the objects from dict
  96         [oldDictionary addEntriesFromDictionary: dict];
  97         // and replace the dictionary with the new one
  98         dict = oldDictionary;
  99     }
 100
 101     // generate a new key and wrap it
 102     itemkey = [CKKSKey randomKeyWrappedByParent: parentkey error:error];
 103     if(!itemkey) {
 104         return nil;
 105     }
 106
 107     // Prepare the authenticated data dictionary. It includes the wrapped key, so prepare that first
 108     CKKSItem* encryptedItem = [[CKKSItem alloc] initCopyingCKKSItem: baseitem];
 109     encryptedItem.parentKeyUUID = parentkey.uuid;
 110     encryptedItem.wrappedkey = itemkey.wrappedkey;
 111
 112     // if we're updating a v2 item, use v2
 113     if(olditem && olditem.encver == CKKSItemEncryptionVersion2 && (int)CKKSItemEncryptionVersion2 >= (int)currentCKKSItemEncryptionVersion) {
 114         encryptedItem.encver = CKKSItemEncryptionVersion2;
 115     } else {
 116         encryptedItem.encver = currentCKKSItemEncryptionVersion;
 117     }
 118
 119     // Copy over the old item's CKRecord, updated for the new item data
 120     if(olditem.storedCKRecord) {
 121         encryptedItem.storedCKRecord = [encryptedItem updateCKRecord:olditem.storedCKRecord zoneID:olditem.storedCKRecord.recordID.zoneID];
 122     }
 123
 124     NSDictionary<NSString*, NSData*>*  authenticatedData = [encryptedItem makeAuthenticatedDataDictionaryUpdatingCKKSItem: olditem encryptionVersion:encryptedItem.encver];
 125
 126     encryptedItem.encitem = [self encryptDictionary: dict key:itemkey.aessivkey authenticatedData:authenticatedData error:error];
 127     if(!encryptedItem.encitem) {
 128         return nil;
 129     }
 130
 131     return encryptedItem;
 132 }
 133
 134 + (NSDictionary*) decryptItemToDictionaryVersionNone: (CKKSItem*) item error: (NSError * __autoreleasing *) error {
 135     return [NSPropertyListSerialization propertyListWithData:item.encitem
 136                                                      options:(NSPropertyListReadOptions)kCFPropertyListSupportedFormatBinary_v1_0
 137                                                       format:nil
 138                                                        error:error];
 139 }
 140
 141 // Note that the only difference between v1 and v2 is the authenticated data selection, so we can happily pass encver along
 142 + (NSDictionary*) decryptItemToDictionaryVersion1or2: (CKKSItem*) item error: (NSError * __autoreleasing *) error {
 143     NSDictionary* authenticatedData = nil;
 144
 145     CKKSAESSIVKey* itemkey = nil;
 146
 147     CKKSKey* key = [CKKSKey loadKeyWithUUID: item.parentKeyUUID zoneID:item.zoneID error:error];
 148     if(!key) {
 149         return nil;
 150     }
 151
 152     itemkey = [key unwrapAESKey:item.wrappedkey error:error];
 153     if(!itemkey) {
 154         return nil;
 155     }
 156
 157     // Prepare the authenticated data dictionary (pass the item as the futureproofed object, so we'll authenticate any new fields in this particular item).
 158     authenticatedData = [item makeAuthenticatedDataDictionaryUpdatingCKKSItem:item encryptionVersion:item.encver];
 159
 160     NSDictionary* result = [self decryptDictionary: item.encitem key:itemkey authenticatedData:authenticatedData error:error];
 161     if(!result) {
 162         secwarning("ckks: couldn't decrypt item %@", *error);
 163     }
 164     return result;
 165 }
 166
 167 + (NSDictionary*) decryptItemToDictionary: (CKKSItem*) item error: (NSError * __autoreleasing *) error {
 168     switch (item.encver) {
 169         case CKKSItemEncryptionVersion1:
 170             return [CKKSItemEncrypter decryptItemToDictionaryVersion1or2:item error:error];
 171         case CKKSItemEncryptionVersion2:
 172             return [CKKSItemEncrypter decryptItemToDictionaryVersion1or2:item error:error];
 173         case CKKSItemEncryptionVersionNone: /* version 0 was no encrypted, no longer supported */
 174         default:
 175         {
 176             NSError *localError = [NSError errorWithDomain:@"securityd"
 177                                                       code:1
 178                                                   userInfo:@{NSLocalizedDescriptionKey:
 179                                                                  [NSString stringWithFormat:@"Unrecognized encryption version: %lu", (unsigned long)item.encver]}];
 180             secerror("decryptItemToDictionary %@", localError);
 181             if (error) {
 182                 *error = localError;
 183             }
 184             return nil;
 185         }
 186     }
 187 }
 188
 189 + (NSData*)encryptDictionary: (NSDictionary*) dict key: (CKKSAESSIVKey*) key authenticatedData: (NSDictionary<NSString*, NSData*>*) ad  error: (NSError * __autoreleasing *) error {
 190     NSData* data = [NSPropertyListSerialization dataWithPropertyList:dict
 191                                                               format:NSPropertyListBinaryFormat_v1_0
 192                                                              options:0
 193                                                                error:error];
 194     if(!data) {
 195         return nil;
 196     }
 197     // Hide password length. Apply extra padding to short passwords.
 198         data = [CKKSItemEncrypter padData:data
 199                                                         blockSize:SecCKKSItemPaddingBlockSize
 200                                           additionalBlock:[(NSData *)dict[@"v_Data"] length] < SecCKKSItemPaddingBlockSize];
 201
 202     return [key encryptData: data authenticatedData: ad error: error];
 203 }
 204
 205 + (NSDictionary*)decryptDictionary: (NSData*) encitem key: (CKKSAESSIVKey*) aeskey authenticatedData: (NSDictionary<NSString*, NSData*>*) ad  error: (NSError * __autoreleasing *) error {
 206     NSData* plaintext = [aeskey decryptData: encitem authenticatedData: ad error: error];
 207     if(!plaintext) {
 208         return nil;
 209     }
 210     plaintext = [CKKSItemEncrypter removePaddingFromData:plaintext];
 211     if(!plaintext) {
 212         if (error) *error = [NSError errorWithDomain:@"securityd"
 213                                                 code:errSecInvalidData
 214                                             userInfo:@{NSLocalizedDescriptionKey: @"Could not remove padding from decrypted item: malformed data"}];
 215         return nil;
 216     }
 217     return [NSPropertyListSerialization propertyListWithData:plaintext
 218                                                     options:(NSPropertyListReadOptions)kCFPropertyListSupportedFormatBinary_v1_0
 219                                                      format:nil
 220                                                       error:error];
 221 }
 222
 223 @end
 224
 225 #endif