Add HMAC-SHA256 support.
Change-Id: I64c7bdf77388e3cb491b702c52c6746d32f317b0
diff --git a/hmac_operation.cpp b/hmac_operation.cpp
new file mode 100644
index 0000000..1620105
--- /dev/null
+++ b/hmac_operation.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright 2014 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 "hmac_operation.h"
+
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+
+namespace keymaster {
+
+HmacOperation::HmacOperation(keymaster_purpose_t purpose, const Logger& logger,
+ const uint8_t* key_data, size_t key_data_size,
+ keymaster_digest_t digest, size_t tag_length)
+ : Operation(purpose, logger), error_(KM_ERROR_OK), tag_length_(tag_length) {
+ // Initialize CTX first, so dtor won't crash even if we error out later.
+ HMAC_CTX_init(&ctx_);
+
+ const EVP_MD* md;
+ switch (digest) {
+ case KM_DIGEST_SHA_2_256:
+ md = EVP_sha256();
+ break;
+ default:
+ error_ = KM_ERROR_UNSUPPORTED_DIGEST;
+ return;
+ }
+
+ if ((int)tag_length_ > EVP_MD_size(md)) {
+ error_ = KM_ERROR_UNSUPPORTED_MAC_LENGTH;
+ return;
+ }
+
+ HMAC_Init_ex(&ctx_, key_data, key_data_size, md, NULL /* engine */);
+}
+
+HmacOperation::~HmacOperation() {
+ HMAC_CTX_cleanup(&ctx_);
+}
+
+keymaster_error_t HmacOperation::Begin() {
+ return error_;
+}
+
+keymaster_error_t HmacOperation::Update(const Buffer& input, Buffer* /* output */,
+ size_t* input_consumed) {
+ if (!HMAC_Update(&ctx_, input.peek_read(), input.available_read()))
+ return KM_ERROR_UNKNOWN_ERROR;
+ *input_consumed = input.available_read();
+ return KM_ERROR_OK;
+}
+
+keymaster_error_t HmacOperation::Abort() {
+ return KM_ERROR_OK;
+}
+
+keymaster_error_t HmacOperation::Finish(const Buffer& signature, Buffer* output) {
+ uint8_t digest[EVP_MAX_MD_SIZE];
+ unsigned int digest_len;
+ if (!HMAC_Final(&ctx_, digest, &digest_len))
+ return KM_ERROR_UNKNOWN_ERROR;
+
+ switch (purpose()) {
+ case KM_PURPOSE_SIGN:
+ output->reserve(tag_length_);
+ output->write(digest, tag_length_);
+ return KM_ERROR_OK;
+ case KM_PURPOSE_VERIFY:
+ if (signature.available_read() != tag_length_)
+ return KM_ERROR_INVALID_INPUT_LENGTH;
+ if (memcmp(signature.peek_read(), digest, tag_length_) != 0)
+ return KM_ERROR_VERIFICATION_FAILED;
+ return KM_ERROR_OK;
+ default:
+ return KM_ERROR_UNSUPPORTED_PURPOSE;
+ }
+}
+
+} // namespace keymaster