Introduce samsungtools to decrypt samsung firmware

Samsung provides many firmware upgrade in the format of a .dat
file, at least for nearly all YP's (checked for Q2, R0, T10, Z5).
This is a simple cyclic xor which a fixed key, a md5 sum and a
header specifying the model/version/region.

Change-Id: Ib0461a74196383189fd2d8162da444a85a229c60

utils/samsungtools/fwdecrypt.c

@@ -0,0 +1,131 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2012 Amaury Pouly
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "samsung.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <getopt.h>
+
+static bool g_debug = false;
+static char *g_out_prefix = NULL;
+
+static void usage(void)
+{
+    printf("Usage: fwdecrypt [options] firmware\n");
+    printf("Options:\n");
+    printf("  -o <prefix>\tSet output file\n");
+    printf("  -f/--force\tForce to continue on errors\n");
+    printf("  -?/--help\tDisplay this message\n");
+    printf("  -d/--debug\tDisplay debug messages\n");
+    exit(1);
+}
+
+static int s_read(void *user, int offset, void *buf, int size)
+{
+    FILE *f = user;
+    if(fseek(f, offset, SEEK_SET) != 0)
+        return 0;
+    return fread(buf, 1, size, f);
+}
+
+static void s_printf(void *user, bool error, const char *fmt, ...)
+{
+    if(!g_debug && !error)
+        return;
+    (void) user;
+    va_list args;
+    va_start(args, fmt);
+    vprintf(fmt, args);
+    va_end(args);
+}
+
+int main(int argc, char **argv)
+{
+    if(argc <= 1)
+        usage();
+
+    while(1)
+    {
+        static struct option long_options[] =
+        {
+            {"help", no_argument, 0, '?'},
+            {"debug", no_argument, 0, 'd'},
+            {0, 0, 0, 0}
+        };
+
+        int c = getopt_long(argc, argv, "?do:", long_options, NULL);
+        if(c == -1)
+            break;
+        switch(c)
+        {
+            case -1:
+                break;
+            case 'd':
+                g_debug = true;
+                break;
+            case '?':
+                usage();
+                break;
+            case 'o':
+                g_out_prefix = optarg;
+                break;
+            default:
+                abort();
+        }
+    }
+
+    if(optind != argc - 1)
+        usage();
+
+    FILE *f = fopen(argv[optind], "rb");
+    if(f == NULL)
+    {
+        printf("Cannot open file for reading: %m\n");
+        return 1;
+    }
+
+    enum samsung_error_t err;
+    struct samsung_firmware_t *fw = samsung_read(s_read, s_printf,
+        f, &err);
+    if(fw == NULL || err != SAMSUNG_SUCCESS)
+    {
+        printf("Error reading firmware: %d\n", err);
+        samsung_free(fw);
+        return 1;
+    }
+    fclose(f);
+
+    if(g_out_prefix)
+    {
+        f = fopen(g_out_prefix, "wb");
+        if(f == NULL)
+        {
+            printf("Cannot open file for writing: %m\n");
+            return 2;
+        }
+        fwrite(fw->data, 1, fw->data_size, f);
+        fclose(f);
+    }
+
+    samsung_free(fw);
+
+    return 0;
+}