1 /* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef KEYSTORE_BLOB_H_ 18 #define KEYSTORE_BLOB_H_ 19 20 #include <stdint.h> 21 22 #include <openssl/aes.h> 23 #include <openssl/md5.h> 24 25 #include <condition_variable> 26 #include <functional> 27 #include <keystore/keymaster_types.h> 28 #include <keystore/keystore.h> 29 #include <list> 30 #include <mutex> 31 #include <set> 32 #include <sstream> 33 #include <vector> 34 35 constexpr size_t kValueSize = 32768; 36 constexpr size_t kAesKeySize = 128 / 8; 37 constexpr size_t kGcmTagLength = 128 / 8; 38 constexpr size_t kGcmIvLength = 96 / 8; 39 constexpr size_t kAes128KeySizeBytes = 128 / 8; 40 41 /* Here is the file format. There are two parts in blob.value, the secret and 42 * the description. The secret is stored in ciphertext, and its original size 43 * can be found in blob.length. The description is stored after the secret in 44 * plaintext, and its size is specified in blob.info. The total size of the two 45 * parts must be no more than kValueSize bytes. The first field is the version, 46 * the second is the blob's type, and the third byte is flags. Fields other 47 * than blob.info, blob.length, and blob.value are modified by encryptBlob() 48 * and decryptBlob(). Thus they should not be accessed from outside. */ 49 50 struct __attribute__((packed)) blobv3 { 51 uint8_t version; 52 uint8_t type; 53 uint8_t flags; 54 uint8_t info; 55 uint8_t initialization_vector[AES_BLOCK_SIZE]; // Only 96 bits is used, rest is zeroed. 56 uint8_t aead_tag[kGcmTagLength]; 57 int32_t length; // in network byte order, only for backward compatibility 58 uint8_t value[kValueSize + AES_BLOCK_SIZE]; 59 }; 60 61 struct __attribute__((packed)) blobv2 { 62 uint8_t version; 63 uint8_t type; 64 uint8_t flags; 65 uint8_t info; 66 uint8_t vector[AES_BLOCK_SIZE]; 67 uint8_t encrypted[0]; // Marks offset to encrypted data. 68 uint8_t digest[MD5_DIGEST_LENGTH]; 69 uint8_t digested[0]; // Marks offset to digested data. 70 int32_t length; // in network byte order 71 uint8_t value[kValueSize + AES_BLOCK_SIZE]; 72 }; 73 74 static_assert(sizeof(blobv3) == sizeof(blobv2) && 75 offsetof(blobv3, initialization_vector) == offsetof(blobv2, vector) && 76 offsetof(blobv3, aead_tag) == offsetof(blobv2, digest) && 77 offsetof(blobv3, aead_tag) == offsetof(blobv2, encrypted) && 78 offsetof(blobv3, length) == offsetof(blobv2, length) && 79 offsetof(blobv3, value) == offsetof(blobv2, value), 80 "Oops. Blob layout changed."); 81 82 static const uint8_t CURRENT_BLOB_VERSION = 3; 83 84 typedef enum { 85 TYPE_ANY = 0, // meta type that matches anything 86 TYPE_GENERIC = 1, 87 TYPE_MASTER_KEY = 2, 88 TYPE_KEY_PAIR = 3, 89 TYPE_KEYMASTER_10 = 4, 90 TYPE_KEY_CHARACTERISTICS = 5, 91 TYPE_KEY_CHARACTERISTICS_CACHE = 6, 92 TYPE_MASTER_KEY_AES256 = 7, 93 } BlobType; 94 95 class LockedKeyBlobEntry; 96 97 /** 98 * The Blob represents the content of a KeyBlobEntry. 99 * 100 * BEWARE: It is only save to call any member function of a Blob b if bool(b) yields true. 101 * Exceptions are putKeyCharacteristics(), the assignment operators and operator bool. 102 */ 103 class Blob { 104 friend LockedKeyBlobEntry; 105 106 public: 107 Blob(const uint8_t* value, size_t valueLength, const uint8_t* info, uint8_t infoLength, 108 BlobType type); 109 explicit Blob(blobv3 b); 110 Blob(); 111 Blob(const Blob& rhs); 112 Blob(Blob&& rhs); 113 ~Blob()114 ~Blob() { 115 if (mBlob) *mBlob = {}; 116 } 117 118 Blob& operator=(const Blob& rhs); 119 Blob& operator=(Blob&& rhs); 120 explicit operator bool() const { return bool(mBlob); } 121 getValue()122 const uint8_t* getValue() const { return mBlob->value; } 123 getLength()124 int32_t getLength() const { return mBlob->length; } 125 getInfo()126 const uint8_t* getInfo() const { return mBlob->value + mBlob->length; } getInfoLength()127 uint8_t getInfoLength() const { return mBlob->info; } 128 getVersion()129 uint8_t getVersion() const { return mBlob->version; } 130 131 bool isEncrypted() const; 132 void setEncrypted(bool encrypted); 133 134 bool isSuperEncrypted() const; 135 void setSuperEncrypted(bool superEncrypted); 136 137 bool isCriticalToDeviceEncryption() const; 138 void setCriticalToDeviceEncryption(bool critical); 139 isFallback()140 bool isFallback() const { return mBlob->flags & KEYSTORE_FLAG_FALLBACK; } 141 void setFallback(bool fallback); 142 setVersion(uint8_t version)143 void setVersion(uint8_t version) { mBlob->version = version; } getType()144 BlobType getType() const { return BlobType(mBlob->type); } setType(BlobType type)145 void setType(BlobType type) { mBlob->type = uint8_t(type); } 146 147 keystore::SecurityLevel getSecurityLevel() const; 148 void setSecurityLevel(keystore::SecurityLevel); 149 150 std::tuple<bool, keystore::AuthorizationSet, keystore::AuthorizationSet> 151 getKeyCharacteristics() const; 152 153 bool putKeyCharacteristics(const keystore::AuthorizationSet& hwEnforced, 154 const keystore::AuthorizationSet& swEnforced); 155 156 private: 157 std::unique_ptr<blobv3> mBlob; 158 159 ResponseCode readBlob(const std::string& filename, const std::vector<uint8_t>& aes_key, 160 State state); 161 }; 162 163 /** 164 * A KeyBlobEntry represents a full qualified key blob as known by Keystore. The key blob 165 * is given by the uid of the owning app and the alias used by the app to refer to this key. 166 * The user_dir_ is technically implied by the uid, but computation of the user directory is 167 * done in the user state database. Which is why we also cache it here. 168 * 169 * The KeyBlobEntry knows the location of the key blob files (which may include a characteristics 170 * cache file) but does not allow read or write access to the content. It also does not imply 171 * the existence of the files. 172 * 173 * KeyBlobEntry abstracts, to some extent, from the the file system based storage of key blobs. 174 * An evolution of KeyBlobEntry may be used for key blob storage based on a back end other than 175 * file system, e.g., SQL database or other. 176 * 177 * For access to the key blob content the programmer has to acquire a LockedKeyBlobEntry (see 178 * below). 179 */ 180 class KeyBlobEntry { 181 private: 182 std::string alias_; 183 std::string user_dir_; 184 uid_t uid_; 185 bool masterkey_; 186 187 public: 188 KeyBlobEntry(std::string alias, std::string user_dir, uid_t uid, bool masterkey = false) alias_(std::move (alias))189 : alias_(std::move(alias)), user_dir_(std::move(user_dir)), uid_(uid), 190 masterkey_(masterkey) {} 191 192 std::string getKeyBlobBaseName() const; 193 std::string getKeyBlobPath() const; 194 195 std::string getCharacteristicsBlobBaseName() const; 196 std::string getCharacteristicsBlobPath() const; 197 198 bool hasKeyBlob() const; 199 bool hasCharacteristicsBlob() const; 200 201 bool operator<(const KeyBlobEntry& rhs) const { 202 return std::tie(uid_, alias_, user_dir_) < std::tie(rhs.uid_, rhs.alias_, rhs.user_dir_); 203 } 204 bool operator==(const KeyBlobEntry& rhs) const { 205 return std::tie(uid_, alias_, user_dir_) == std::tie(rhs.uid_, rhs.alias_, rhs.user_dir_); 206 } 207 bool operator!=(const KeyBlobEntry& rhs) const { return !(*this == rhs); } 208 alias()209 inline const std::string& alias() const { return alias_; } user_dir()210 inline const std::string& user_dir() const { return user_dir_; } uid()211 inline uid_t uid() const { return uid_; } 212 }; 213 214 /** 215 * The LockedKeyBlobEntry is a proxy object to KeyBlobEntry that expresses exclusive ownership 216 * of a KeyBlobEntry. LockedKeyBlobEntries can be acquired by calling 217 * LockedKeyBlobEntry::get() or LockedKeyBlobEntry::list(). 218 * 219 * LockedKeyBlobEntries are movable but not copyable. By convention they can only 220 * be taken by the dispatcher thread of keystore, but not by any keymaster worker thread. 221 * The dispatcher thread may transfer ownership of a locked entry to a keymaster worker thread. 222 * 223 * Locked entries are tracked on the stack or as members of movable functor objects passed to the 224 * keymaster worker request queues. Locks are relinquished as the locked entry gets destroyed, e.g., 225 * when it goes out of scope or when the owning request functor gets destroyed. 226 * 227 * LockedKeyBlobEntry::list(), which must only be called by the dispatcher, blocks until all 228 * LockedKeyBlobEntries have been destroyed. Thereby list acts as a fence to make sure it gets a 229 * consistent view of the key blob database. Under the assumption that keymaster worker requests 230 * cannot run or block indefinitely and cannot grab new locked entries, progress is guaranteed. 231 * It then grabs locked entries in accordance with the given filter rule. 232 * 233 * LockedKeyBlobEntry allow access to the proxied KeyBlobEntry interface through the operator->. 234 * They add additional functionality to access and modify the key blob's content on disk. 235 * LockedKeyBlobEntry ensures atomic operations on the persistently stored key blobs on a per 236 * entry granularity. 237 */ 238 class LockedKeyBlobEntry { 239 private: 240 static std::set<KeyBlobEntry> locked_blobs_; 241 static std::mutex locked_blobs_mutex_; 242 static std::condition_variable locked_blobs_mutex_cond_var_; 243 244 const KeyBlobEntry* entry_; 245 // NOLINTNEXTLINE(google-explicit-constructor) LockedKeyBlobEntry(const KeyBlobEntry & entry)246 LockedKeyBlobEntry(const KeyBlobEntry& entry) : entry_(&entry) {} 247 248 static void put(const KeyBlobEntry& entry); 249 LockedKeyBlobEntry(const LockedKeyBlobEntry&) = delete; 250 LockedKeyBlobEntry& operator=(const LockedKeyBlobEntry&) = delete; 251 252 public: LockedKeyBlobEntry()253 LockedKeyBlobEntry() : entry_(nullptr){}; 254 ~LockedKeyBlobEntry(); LockedKeyBlobEntry(LockedKeyBlobEntry && rhs)255 LockedKeyBlobEntry(LockedKeyBlobEntry&& rhs) : entry_(rhs.entry_) { rhs.entry_ = nullptr; } 256 LockedKeyBlobEntry& operator=(LockedKeyBlobEntry&& rhs) { 257 // as dummy goes out of scope it relinquishes the lock on this 258 LockedKeyBlobEntry dummy(std::move(*this)); 259 entry_ = rhs.entry_; 260 rhs.entry_ = nullptr; 261 return *this; 262 } 263 static LockedKeyBlobEntry get(KeyBlobEntry entry); 264 static std::tuple<ResponseCode, std::list<LockedKeyBlobEntry>> 265 list(const std::string& user_dir, 266 std::function<bool(uid_t, const std::string&)> filter = 267 [](uid_t, const std::string&) -> bool { return true; }); 268 269 ResponseCode writeBlobs(Blob keyBlob, Blob characteristicsBlob, 270 const std::vector<uint8_t>& aes_key, State state) const; 271 std::tuple<ResponseCode, Blob, Blob> readBlobs(const std::vector<uint8_t>& aes_key, 272 State state) const; 273 ResponseCode deleteBlobs() const; 274 275 inline explicit operator bool() const { return entry_ != nullptr; } 276 inline const KeyBlobEntry& operator*() const { return *entry_; } 277 inline const KeyBlobEntry* operator->() const { return entry_; } 278 }; 279 280 // Visible for testing 281 std::string encodeKeyName(const std::string& keyName); 282 std::string decodeKeyName(const std::string& encodedName); 283 284 #endif // KEYSTORE_BLOB_H_ 285