Vboot reference: A basic user-land verified boot firmware signing and verification utility.

src/platform/vboot_reference/utils/file_keys.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 functions for file and key handling.
  */
 
 #include "file_keys.h"
 
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "padding.h"
 #include "rsa_utility.h"
 #include "utility.h"
 
-uint8_t* BufferFromFile(char* input_file, int* len) {
+uint8_t* BufferFromFile(const char* input_file, uint32_t* len) {
   int fd;
   struct stat stat_fd;
   uint8_t* buf = NULL;
 
   if ((fd = open(input_file, O_RDONLY)) == -1) {
     fprintf(stderr, "Couldn't open file.\n");
     return NULL;
   }
 
   if (-1 == fstat(fd, &stat_fd)) {
     fprintf(stderr, "Couldn't stat key file\n");
     return NULL;
   }
   *len = stat_fd.st_size;
 
   /* Read entire key binary blob into a buffer. */
   buf = (uint8_t*) Malloc(*len);
   if (!buf)
     return NULL;
 
   if (*len != read(fd, buf, *len)) {
     fprintf(stderr, "Couldn't read key into a buffer.\n");
     return NULL;
   }
 
   close(fd);
   return buf;
 }
 
-RSAPublicKey* RSAPublicKeyFromFile(char* input_file) {
-  int len;
+RSAPublicKey* RSAPublicKeyFromFile(const char* input_file) {
+  uint32_t len;
+  RSAPublicKey* key;
   uint8_t* buf = BufferFromFile(input_file, &len);
-  RSAPublicKey* key = RSAPublicKeyFromBuf(buf, len);
+  if (buf)
+    key = RSAPublicKeyFromBuf(buf, len);
   Free(buf);
   return key;
 }
 
-uint8_t* SignatureFile(char* input_file, char* key_file, int algorithm) {
+uint8_t* SignatureFile(const char* input_file, const char* key_file,
+                       int algorithm) {
   char* sign_utility = "./sign_data.sh";
   char* cmd;  /* Command line to invoke. */
   int cmd_len;
   FILE* cmd_out;  /* File descriptor to command output. */
   uint8_t* signature = NULL;
   int signature_size = siglen_map[algorithm] * sizeof(uint32_t);
 
   /* Build command line:
    * sign_data.sh <algorithm> <key file> <input file>
    */
@@ skipping 16 matching lines @@
   if (fread(signature, signature_size, 1, cmd_out) != 1) {
     fprintf(stderr, "Couldn't read signature.\n");
     pclose(cmd_out);
     Free(signature);
     return NULL;
   }
 
   pclose(cmd_out);
   return signature;
 }