| /* |
| * Copyright 2015 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "ocb_utils.h" |
| |
| #include <assert.h> |
| |
| #include <new> |
| |
| #include <openssl/aes.h> |
| #include <openssl/sha.h> |
| |
| #include <hardware/keymaster_defs.h> |
| #include <keymaster/authorization_set.h> |
| #include <keymaster/android_keymaster_utils.h> |
| |
| #include "openssl_err.h" |
| |
| namespace keymaster { |
| |
| class AeCtx { |
| public: |
| AeCtx() : ctx_(ae_allocate(NULL)) {} |
| ~AeCtx() { |
| ae_clear(ctx_); |
| ae_free(ctx_); |
| } |
| |
| ae_ctx* get() { return ctx_; } |
| |
| private: |
| ae_ctx* ctx_; |
| }; |
| |
| static keymaster_error_t BuildDerivationData(const AuthorizationSet& hw_enforced, |
| const AuthorizationSet& sw_enforced, |
| const AuthorizationSet& hidden, |
| UniquePtr<uint8_t[]>* derivation_data, |
| size_t* derivation_data_length) { |
| *derivation_data_length = |
| hidden.SerializedSize() + hw_enforced.SerializedSize() + sw_enforced.SerializedSize(); |
| derivation_data->reset(new (std::nothrow) uint8_t[*derivation_data_length]); |
| if (!derivation_data->get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| uint8_t* buf = derivation_data->get(); |
| uint8_t* end = derivation_data->get() + *derivation_data_length; |
| buf = hidden.Serialize(buf, end); |
| buf = hw_enforced.Serialize(buf, end); |
| buf = sw_enforced.Serialize(buf, end); |
| |
| return KM_ERROR_OK; |
| } |
| |
| static keymaster_error_t InitializeKeyWrappingContext(const AuthorizationSet& hw_enforced, |
| const AuthorizationSet& sw_enforced, |
| const AuthorizationSet& hidden, |
| const KeymasterKeyBlob& master_key, |
| AeCtx* ctx) { |
| size_t derivation_data_length; |
| UniquePtr<uint8_t[]> derivation_data; |
| keymaster_error_t error = BuildDerivationData(hw_enforced, sw_enforced, hidden, |
| &derivation_data, &derivation_data_length); |
| if (error != KM_ERROR_OK) |
| return error; |
| |
| SHA256_CTX sha256_ctx; |
| UniquePtr<uint8_t[]> hash_buf(new (std::nothrow) uint8_t[SHA256_DIGEST_LENGTH]); |
| if (!hash_buf.get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| Eraser hash_eraser(hash_buf.get(), SHA256_DIGEST_LENGTH); |
| UniquePtr<uint8_t[]> derived_key(new (std::nothrow) uint8_t[AES_BLOCK_SIZE]); |
| if (!derived_key.get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| Eraser derived_key_eraser(derived_key.get(), AES_BLOCK_SIZE); |
| |
| if (!ctx->get() || !hash_buf.get() || !derived_key.get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| // Hash derivation data. |
| Eraser sha256_ctx_eraser(sha256_ctx); |
| SHA256_Init(&sha256_ctx); |
| SHA256_Update(&sha256_ctx, derivation_data.get(), derivation_data_length); |
| SHA256_Final(hash_buf.get(), &sha256_ctx); |
| |
| // Encrypt hash with master key to build derived key. |
| AES_KEY aes_key; |
| Eraser aes_key_eraser(AES_KEY); |
| if (0 != |
| AES_set_encrypt_key(master_key.key_material, master_key.key_material_size * 8, &aes_key)) |
| return TranslateLastOpenSslError(); |
| |
| AES_encrypt(hash_buf.get(), derived_key.get(), &aes_key); |
| |
| // Set up AES OCB context using derived key. |
| if (ae_init(ctx->get(), derived_key.get(), AES_BLOCK_SIZE /* key length */, OCB_NONCE_LENGTH, |
| OCB_TAG_LENGTH) != AE_SUCCESS) { |
| memset_s(ctx->get(), 0, ae_ctx_sizeof()); |
| return KM_ERROR_UNKNOWN_ERROR; |
| } |
| |
| return KM_ERROR_OK; |
| } |
| |
| keymaster_error_t OcbEncryptKey(const AuthorizationSet& hw_enforced, |
| const AuthorizationSet& sw_enforced, const AuthorizationSet& hidden, |
| const KeymasterKeyBlob& master_key, |
| const KeymasterKeyBlob& plaintext, const Buffer& nonce, |
| KeymasterKeyBlob* ciphertext, Buffer* tag) { |
| assert(ciphertext && tag); |
| |
| if (nonce.available_read() != OCB_NONCE_LENGTH) |
| return KM_ERROR_INVALID_ARGUMENT; |
| |
| AeCtx ctx; |
| if (!ctx.get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| keymaster_error_t error = |
| InitializeKeyWrappingContext(hw_enforced, sw_enforced, hidden, master_key, &ctx); |
| if (error != KM_ERROR_OK) |
| return error; |
| |
| if (!ciphertext->Reset(plaintext.key_material_size)) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| int ae_err = ae_encrypt(ctx.get(), nonce.peek_read(), plaintext.key_material, |
| plaintext.key_material_size, NULL /* additional data */, |
| 0 /* additional data length */, ciphertext->writable_data(), |
| tag->peek_write(), 1 /* final */); |
| if (ae_err < 0) { |
| LOG_E("Error %d while encrypting key", ae_err); |
| return KM_ERROR_UNKNOWN_ERROR; |
| } |
| if (!tag->advance_write(OCB_TAG_LENGTH)) |
| return KM_ERROR_UNKNOWN_ERROR; |
| assert(ae_err == static_cast<int>(plaintext.key_material_size)); |
| return KM_ERROR_OK; |
| } |
| |
| keymaster_error_t OcbDecryptKey(const AuthorizationSet& hw_enforced, |
| const AuthorizationSet& sw_enforced, const AuthorizationSet& hidden, |
| const KeymasterKeyBlob& master_key, |
| const KeymasterKeyBlob& ciphertext, const Buffer& nonce, |
| const Buffer& tag, KeymasterKeyBlob* plaintext) { |
| assert(plaintext); |
| |
| if (nonce.available_read() != OCB_NONCE_LENGTH || tag.available_read() != OCB_TAG_LENGTH) |
| return KM_ERROR_INVALID_ARGUMENT; |
| |
| AeCtx ctx; |
| if (!ctx.get()) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| keymaster_error_t error = |
| InitializeKeyWrappingContext(hw_enforced, sw_enforced, hidden, master_key, &ctx); |
| if (error != KM_ERROR_OK) |
| return error; |
| |
| if (!plaintext->Reset(ciphertext.key_material_size)) |
| return KM_ERROR_MEMORY_ALLOCATION_FAILED; |
| |
| int ae_err = ae_decrypt(ctx.get(), nonce.peek_read(), ciphertext.key_material, |
| ciphertext.key_material_size, NULL /* additional data */, |
| 0 /* additional data length */, plaintext->writable_data(), |
| tag.peek_read(), 1 /* final */); |
| if (ae_err == AE_INVALID) { |
| // Authentication failed! Decryption probably succeeded(ish), but we don't want to return |
| // any data when the authentication fails, so clear it. |
| plaintext->Clear(); |
| LOG_E("Failed to validate authentication tag during key decryption", 0); |
| return KM_ERROR_INVALID_KEY_BLOB; |
| } else if (ae_err < 0) { |
| LOG_E("Failed to decrypt key, error: %d", ae_err); |
| return KM_ERROR_UNKNOWN_ERROR; |
| } |
| assert(ae_err == static_cast<int>(ciphertext.key_material_size)); |
| return KM_ERROR_OK; |
| } |
| |
| } // namespace keymaster |