Utility to output digests in format suitable for RSA signatures.

src/platform/vboot_reference/tests/signature_digest.c

+/* 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 that outputs the message digest of the contents of a file in a
+ * format that can be used as input to OpenSSL for an RSA signature.
+ * Needed until the stable OpenSSL release supports SHA-256/512 digests for
+ * RSA signatures.
+ * Outputs DigestInfo || Digest where DigestInfo is the OID depending on the
+ * choice of the hash algorithm (see padding.c).
+ *
+ */
+
+#include "signature_digest.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "digest_utility.h"
+#include "padding.h"
+#include "sha.h"
+
+uint8_t* prepend_digestinfo(int algorithm, uint8_t* digest) {
+  const int digest_size = hash_size_map[algorithm];
+  const int digestinfo_size = digestinfo_size_map[algorithm];
+  const uint8_t* digestinfo = hash_digestinfo_map[algorithm];
+  uint8_t* p = malloc(digestinfo_size + digest_size);
+  memcpy(p, digestinfo, digestinfo_size);
+  memcpy(p + digestinfo_size, digest, digest_size);
+  return p;
+}
+
+int main(int argc, char* argv[]) {
+  int i, algorithm;
+  uint8_t* digest = NULL;
+  uint8_t* signature = NULL;
+  uint8_t* info_digest  = NULL;
+
+  if (argc != 3) {
+    fprintf(stderr, "Usage: %s <algorithm> <input file>\n\n",
+            argv[0]);
+    fprintf(stderr, "where <algorithm> is the signature algorithm to use:\n");
+    for(i = 0; i<kNumAlgorithms; i++)
+      fprintf(stderr, "\t%d for %s\n", i, algo_strings[i]);
+    return -1;
+  }
+
+  algorithm = atoi(argv[1]);
+  if (algorithm >= kNumAlgorithms) {
+    fprintf(stderr, "Invalid Algorithm!\n");
+    goto failure;
+  }
+
+  if (!(digest = calculate_digest(argv[2], algorithm)))
+    goto failure;
+
+  info_digest = prepend_digestinfo(algorithm, digest);
+  write(1, info_digest, hash_size_map[algorithm] +
+        digestinfo_size_map[algorithm]);
+
+failure:
+  free(digest);
+  free(info_digest);
+  free(signature);
+
+  return 0;
+}