Address some security concerns in the cgpt tool.

cgpt/cmd_boot.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.
 
 #include "cgpt.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <getopt.h>
 #include <stdio.h>
@@ skipping 16 matching lines @@
          "  -b FILE      Install bootloader code in the PMBR\n"
          "  -p           Create legacy PMBR partition table\n"
          "\n"
          "With no options, it will just print the PMBR boot guid\n"
          "\n", progname);
 }
 
 
 int cmd_boot(int argc, char *argv[]) {
   struct drive drive;
-  int partition = 0;
+  uint32_t partition = 0;
   char *bootfile = 0;
   int create_pmbr = 0;
   int retval = 1;
   int gpt_retval;
-  
+
   int c;
   int errorcnt = 0;
   char *e = 0;
 
   opterr = 0;                     // quiet, you
   while ((c=getopt(argc, argv, ":hi:b:p")) != -1)
   {
     switch (c)
     {
     case 'i':
       partition = (uint32_t)strtoul(optarg, &e, 0);
       if (!*optarg || (e && *e))
       {
         Error("invalid argument to -%c: \"%s\"\n", c, optarg);
         errorcnt++;
       }
       break;
     case 'b':
       bootfile = optarg;
       break;
     case 'p':
       create_pmbr = 1;
       break;
-      
+
     case 'h':
       Usage();
       return CGPT_OK;
     case '?':
       Error("unrecognized option: -%c\n", optopt);
       errorcnt++;
       break;
     case ':':
       Error("missing argument to -%c\n", optopt);
       errorcnt++;
@@ skipping 14 matching lines @@
     return CGPT_FAILED;
   }
 
   if (CGPT_OK != DriveOpen(argv[optind], &drive))
     return CGPT_FAILED;
 
   if (CGPT_OK != ReadPMBR(&drive)) {
     Error("Unable to read PMBR\n");
     goto done;
   }
-    
+
   if (create_pmbr) {
     drive.pmbr.magic[0] = 0x1d;
     drive.pmbr.magic[1] = 0x9a;
     drive.pmbr.sig[0] = 0x55;
     drive.pmbr.sig[1] = 0xaa;
     memset(&drive.pmbr.part, 0, sizeof(drive.pmbr.part));
     drive.pmbr.part[0].f_head = 0x00;
     drive.pmbr.part[0].f_sect = 0x02;
     drive.pmbr.part[0].f_cyl = 0x00;
     drive.pmbr.part[0].type = 0xee;
@@ skipping 12 matching lines @@
       Error("GptSanityCheck() returned %d: %s\n",
             gpt_retval, GptError(gpt_retval));
       goto done;
     }
 
     if (partition > GetNumberOfEntries(&drive.gpt)) {
       Error("invalid partition number: %d\n", partition);
       goto done;
     }
 
-    int index = partition - 1;
+    uint32_t index = partition - 1;
     GptEntry *entry = GetEntry(&drive.gpt, PRIMARY, index);
     memcpy(&drive.pmbr.boot_guid, &entry->unique, sizeof(Guid));
   }
 
   if (bootfile) {
     int fd = open(bootfile, O_RDONLY);
     if (fd < 0) {
       Error("Can't read %s: %s\n", bootfile, strerror(errno));
       goto done;
     }
 
     int n = read(fd, drive.pmbr.bootcode, sizeof(drive.pmbr.bootcode));
     if (n < 1) {
       Error("problem reading %s: %s\n", bootfile, strerror(errno));
       close(fd);
       goto done;
     }
 
     close(fd);
   }
-      
-  char buf[256];
-  GuidToStr(&drive.pmbr.boot_guid, buf);
+
+  char buf[GUID_STRLEN];
+  GuidToStr(&drive.pmbr.boot_guid, buf, sizeof(buf));
   printf("%s\n", buf);
 
   // Write it all out
   if (CGPT_OK == WritePMBR(&drive))
     retval = 0;
 
 done:
   (void) DriveClose(&drive, 1);
   return retval;
 }