Shawn Willden | 6507c27 | 2016-01-05 22:51:48 -0700 | [diff] [blame^] | 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 | #define LOG_TAG "keystore" |
| 18 | |
| 19 | #include <arpa/inet.h> |
| 20 | #include <errno.h> |
| 21 | #include <fcntl.h> |
| 22 | #include <string.h> |
| 23 | |
| 24 | #include <cutils/log.h> |
| 25 | |
| 26 | #include "blob.h" |
| 27 | #include "entropy.h" |
| 28 | |
| 29 | #include "keystore_utils.h" |
| 30 | |
| 31 | Blob::Blob(const uint8_t* value, size_t valueLength, const uint8_t* info, uint8_t infoLength, |
| 32 | BlobType type) { |
| 33 | memset(&mBlob, 0, sizeof(mBlob)); |
| 34 | if (valueLength > VALUE_SIZE) { |
| 35 | valueLength = VALUE_SIZE; |
| 36 | ALOGW("Provided blob length too large"); |
| 37 | } |
| 38 | if (infoLength + valueLength > VALUE_SIZE) { |
| 39 | infoLength = VALUE_SIZE - valueLength; |
| 40 | ALOGW("Provided info length too large"); |
| 41 | } |
| 42 | mBlob.length = valueLength; |
| 43 | memcpy(mBlob.value, value, valueLength); |
| 44 | |
| 45 | mBlob.info = infoLength; |
| 46 | memcpy(mBlob.value + valueLength, info, infoLength); |
| 47 | |
| 48 | mBlob.version = CURRENT_BLOB_VERSION; |
| 49 | mBlob.type = uint8_t(type); |
| 50 | |
| 51 | if (type == TYPE_MASTER_KEY) { |
| 52 | mBlob.flags = KEYSTORE_FLAG_ENCRYPTED; |
| 53 | } else { |
| 54 | mBlob.flags = KEYSTORE_FLAG_NONE; |
| 55 | } |
| 56 | } |
| 57 | |
| 58 | Blob::Blob(blob b) { |
| 59 | mBlob = b; |
| 60 | } |
| 61 | |
| 62 | Blob::Blob() { |
| 63 | memset(&mBlob, 0, sizeof(mBlob)); |
| 64 | } |
| 65 | |
| 66 | bool Blob::isEncrypted() const { |
| 67 | if (mBlob.version < 2) { |
| 68 | return true; |
| 69 | } |
| 70 | |
| 71 | return mBlob.flags & KEYSTORE_FLAG_ENCRYPTED; |
| 72 | } |
| 73 | |
| 74 | void Blob::setEncrypted(bool encrypted) { |
| 75 | if (encrypted) { |
| 76 | mBlob.flags |= KEYSTORE_FLAG_ENCRYPTED; |
| 77 | } else { |
| 78 | mBlob.flags &= ~KEYSTORE_FLAG_ENCRYPTED; |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | void Blob::setFallback(bool fallback) { |
| 83 | if (fallback) { |
| 84 | mBlob.flags |= KEYSTORE_FLAG_FALLBACK; |
| 85 | } else { |
| 86 | mBlob.flags &= ~KEYSTORE_FLAG_FALLBACK; |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | ResponseCode Blob::writeBlob(const char* filename, AES_KEY* aes_key, State state, |
| 91 | Entropy* entropy) { |
| 92 | ALOGV("writing blob %s", filename); |
| 93 | if (isEncrypted()) { |
| 94 | if (state != STATE_NO_ERROR) { |
| 95 | ALOGD("couldn't insert encrypted blob while not unlocked"); |
| 96 | return LOCKED; |
| 97 | } |
| 98 | |
| 99 | if (!entropy->generate_random_data(mBlob.vector, AES_BLOCK_SIZE)) { |
| 100 | ALOGW("Could not read random data for: %s", filename); |
| 101 | return SYSTEM_ERROR; |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | // data includes the value and the value's length |
| 106 | size_t dataLength = mBlob.length + sizeof(mBlob.length); |
| 107 | // pad data to the AES_BLOCK_SIZE |
| 108 | size_t digestedLength = ((dataLength + AES_BLOCK_SIZE - 1) / AES_BLOCK_SIZE * AES_BLOCK_SIZE); |
| 109 | // encrypted data includes the digest value |
| 110 | size_t encryptedLength = digestedLength + MD5_DIGEST_LENGTH; |
| 111 | // move info after space for padding |
| 112 | memmove(&mBlob.encrypted[encryptedLength], &mBlob.value[mBlob.length], mBlob.info); |
| 113 | // zero padding area |
| 114 | memset(mBlob.value + mBlob.length, 0, digestedLength - dataLength); |
| 115 | |
| 116 | mBlob.length = htonl(mBlob.length); |
| 117 | |
| 118 | if (isEncrypted()) { |
| 119 | MD5(mBlob.digested, digestedLength, mBlob.digest); |
| 120 | |
| 121 | uint8_t vector[AES_BLOCK_SIZE]; |
| 122 | memcpy(vector, mBlob.vector, AES_BLOCK_SIZE); |
| 123 | AES_cbc_encrypt(mBlob.encrypted, mBlob.encrypted, encryptedLength, aes_key, vector, |
| 124 | AES_ENCRYPT); |
| 125 | } |
| 126 | |
| 127 | size_t headerLength = (mBlob.encrypted - (uint8_t*)&mBlob); |
| 128 | size_t fileLength = encryptedLength + headerLength + mBlob.info; |
| 129 | |
| 130 | const char* tmpFileName = ".tmp"; |
| 131 | int out = |
| 132 | TEMP_FAILURE_RETRY(open(tmpFileName, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR)); |
| 133 | if (out < 0) { |
| 134 | ALOGW("could not open file: %s: %s", tmpFileName, strerror(errno)); |
| 135 | return SYSTEM_ERROR; |
| 136 | } |
| 137 | size_t writtenBytes = writeFully(out, (uint8_t*)&mBlob, fileLength); |
| 138 | if (close(out) != 0) { |
| 139 | return SYSTEM_ERROR; |
| 140 | } |
| 141 | if (writtenBytes != fileLength) { |
| 142 | ALOGW("blob not fully written %zu != %zu", writtenBytes, fileLength); |
| 143 | unlink(tmpFileName); |
| 144 | return SYSTEM_ERROR; |
| 145 | } |
| 146 | if (rename(tmpFileName, filename) == -1) { |
| 147 | ALOGW("could not rename blob to %s: %s", filename, strerror(errno)); |
| 148 | return SYSTEM_ERROR; |
| 149 | } |
| 150 | return NO_ERROR; |
| 151 | } |
| 152 | |
| 153 | ResponseCode Blob::readBlob(const char* filename, AES_KEY* aes_key, State state) { |
| 154 | ALOGV("reading blob %s", filename); |
| 155 | int in = TEMP_FAILURE_RETRY(open(filename, O_RDONLY)); |
| 156 | if (in < 0) { |
| 157 | return (errno == ENOENT) ? KEY_NOT_FOUND : SYSTEM_ERROR; |
| 158 | } |
| 159 | // fileLength may be less than sizeof(mBlob) since the in |
| 160 | // memory version has extra padding to tolerate rounding up to |
| 161 | // the AES_BLOCK_SIZE |
| 162 | size_t fileLength = readFully(in, (uint8_t*)&mBlob, sizeof(mBlob)); |
| 163 | if (close(in) != 0) { |
| 164 | return SYSTEM_ERROR; |
| 165 | } |
| 166 | |
| 167 | if (fileLength == 0) { |
| 168 | return VALUE_CORRUPTED; |
| 169 | } |
| 170 | |
| 171 | if (isEncrypted() && (state != STATE_NO_ERROR)) { |
| 172 | return LOCKED; |
| 173 | } |
| 174 | |
| 175 | size_t headerLength = (mBlob.encrypted - (uint8_t*)&mBlob); |
| 176 | if (fileLength < headerLength) { |
| 177 | return VALUE_CORRUPTED; |
| 178 | } |
| 179 | |
| 180 | ssize_t encryptedLength = fileLength - (headerLength + mBlob.info); |
| 181 | if (encryptedLength < 0) { |
| 182 | return VALUE_CORRUPTED; |
| 183 | } |
| 184 | |
| 185 | ssize_t digestedLength; |
| 186 | if (isEncrypted()) { |
| 187 | if (encryptedLength % AES_BLOCK_SIZE != 0) { |
| 188 | return VALUE_CORRUPTED; |
| 189 | } |
| 190 | |
| 191 | AES_cbc_encrypt(mBlob.encrypted, mBlob.encrypted, encryptedLength, aes_key, mBlob.vector, |
| 192 | AES_DECRYPT); |
| 193 | digestedLength = encryptedLength - MD5_DIGEST_LENGTH; |
| 194 | uint8_t computedDigest[MD5_DIGEST_LENGTH]; |
| 195 | MD5(mBlob.digested, digestedLength, computedDigest); |
| 196 | if (memcmp(mBlob.digest, computedDigest, MD5_DIGEST_LENGTH) != 0) { |
| 197 | return VALUE_CORRUPTED; |
| 198 | } |
| 199 | } else { |
| 200 | digestedLength = encryptedLength; |
| 201 | } |
| 202 | |
| 203 | ssize_t maxValueLength = digestedLength - sizeof(mBlob.length); |
| 204 | mBlob.length = ntohl(mBlob.length); |
| 205 | if (mBlob.length < 0 || mBlob.length > maxValueLength) { |
| 206 | return VALUE_CORRUPTED; |
| 207 | } |
| 208 | if (mBlob.info != 0) { |
| 209 | // move info from after padding to after data |
| 210 | memmove(&mBlob.value[mBlob.length], &mBlob.value[maxValueLength], mBlob.info); |
| 211 | } |
| 212 | return ::NO_ERROR; |
| 213 | } |