Add generic wrappers for performing message digest operations.

src/platform/vboot_reference/include/sha_utility.h

+/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Utility functions for message digests.
+*/
+
+#ifndef VBOOT_REFERENCE_SHA_UTILITY_H_
+#define VBOOT_REFERENCE_SHA_UTILITY_H_
+
+#include <inttypes.h>
+
+#include "sha.h"
+
+#define SHA1_DIGEST_ALGORITHM 0
+#define SHA256_DIGEST_ALGORITHM 1
+#define SHA512_DIGEST_ALGORITHM 2
+
+/* A generic digest context structure which can be used to represent
+ * the SHA*_CTX for multiple digest algorithms.
+ */
+typedef struct DigestContext {
+  SHA1_CTX* sha1_ctx;
+  SHA256_CTX* sha256_ctx;
+  SHA512_CTX* sha512_ctx;
+  int algorithm;  /* Hashing algorithm to use. */
+} DigestContext;
+
+/* Wrappers for message digest algorithms. These are useful when the hashing
+ * operation is being done in parallel with something else. DigestContext tracks
+ * and stores the state of any digest algorithms (one at a time).
+ */
+
+/* Initialize a digest context for use with signature algorithm [algorithm]. */
+void DigestInit(DigestContext* ctx, int sig_algorithm);
+void DigestUpdate(DigestContext* ctx, const uint8_t* data, int len);
+
+/* Caller owns the returned digest and must free it. */
+uint8_t* DigestFinal(DigestContext* ctx);
+
+/* Returns the appropriate digest for the data in [input_file]
+ * based on the signature [algorithm].
+ * Caller owns the returned digest and must free it.
+ */
+uint8_t* DigestFile(char* input_file, int sig_algorithm);
+
+/* Returns the appropriate digest of [buf] of length
+ * [len] based on the signature [algorithm].
+ * Caller owns the returned digest and must free it.
+ */
+uint8_t* DigestBuf(uint8_t* buf, int len, int sig_algorithm);
+
+#endif  /* VBOOT_REFERENCE_SHA_UTILITY_H_ */