From d65be9df5fc624147d09d026fb5e8dd0156ca74c Mon Sep 17 00:00:00 2001
From: Gabor Juhos <juhosg@openwrt.org>
Date: Sat, 28 Nov 2009 08:25:53 +0000
Subject: [PATCH] firmware-utils: add WNDR3700 image fixing tool (thanks to
 Anael Orlinski)

SVN-Revision: 18569
---
 Makefile       |   1 +
 src/wndr3700.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 140 insertions(+)
 create mode 100644 src/wndr3700.c

diff --git a/Makefile b/Makefile
index 5ccc0d1..ec41e08 100644
--- a/Makefile
+++ b/Makefile
@@ -52,6 +52,7 @@ define Host/Compile
 	$(call cc,pc1crypt)
 	$(call cc,osbridge-crc)
 	$(call cc2,wrt400n cyg_crc32)
+	$(call cc,wndr3700)
 endef
 
 define Host/Install
diff --git a/src/wndr3700.c b/src/wndr3700.c
new file mode 100644
index 0000000..51e5352
--- /dev/null
+++ b/src/wndr3700.c
@@ -0,0 +1,139 @@
+/*
+ * wndr3700.c - partially based on OpenWrt's add_header.c
+ *
+ * Copyright (C) 2009 Anael Orlinski  <naouel@naouel.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License,
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+/*
+ * The add_header utility used by various vendors preprends the buf
+ * image with a header containing a CRC32 value which is generated for the
+ * model id + reserved space for CRC32 + buf, then replaces the reserved
+ * area with the actual CRC32. This replacement tool mimics this behavior.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <string.h>
+#include <netinet/in.h>
+#include <inttypes.h>
+
+#define BPB 8 /* bits/byte */
+
+static uint32_t crc32[1<<BPB];
+
+static void init_crc32()
+{
+	const uint32_t poly = ntohl(0x2083b8ed);
+	int n;
+
+	for (n = 0; n < 1<<BPB; n++) {
+		uint32_t crc = n;
+		int bit;
+
+		for (bit = 0; bit < BPB; bit++)
+			crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
+		crc32[n] = crc;
+	}
+}
+
+static uint32_t crc32buf(unsigned char *buf, size_t len)
+{
+	uint32_t crc = 0xFFFFFFFF;
+
+	for (; len; len--, buf++)
+		crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
+	return ~crc;
+}
+
+struct header {
+    uint32_t magic;
+    uint32_t crc;
+    unsigned char stuff[56];
+};
+
+static void usage(const char *) __attribute__ (( __noreturn__ ));
+
+static void usage(const char *mess)
+{
+	fprintf(stderr, "Error: %s\n", mess);
+	fprintf(stderr, "Usage: wndr3700 input_file output_file\n");
+	fprintf(stderr, "\n");
+	exit(1);
+}
+
+int main(int argc, char **argv)
+{
+	off_t len;			// of original buf
+	off_t buflen;			// of the output file
+	int fd;
+	void *input_file;		// pointer to the input file (mmmapped)
+	struct header header;
+	unsigned char *buf;	// pointer to prefix + copy of original buf
+
+	// verify parameters
+
+	if (argc != 3)
+		usage("wrong number of arguments");
+
+	// mmap input_file
+	if ((fd = open(argv[1], O_RDONLY))  < 0
+	|| (len = lseek(fd, 0, SEEK_END)) < 0
+	|| (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
+	|| close(fd) < 0)
+	{
+		fprintf(stderr, "Error loading file %s: %s\n", argv[1], strerror(errno));
+		exit(1);
+	}
+
+	buflen = len;
+
+	init_crc32();
+
+        // preload header
+        memcpy(&header, input_file, sizeof(header));
+
+        header.magic = htonl(0x33373030); /* 3700 in ascii */
+	header.crc = 0;
+
+	// create a firmware image in memory and copy the input_file to it
+	buf = malloc(buflen);
+	memcpy(buf, input_file, len);
+
+	// CRC of temporary header
+	header.crc = htonl(crc32buf((unsigned char*)&header, sizeof(header)));
+
+	memcpy(buf, &header, sizeof(header));
+
+	// write the buf
+	if ((fd = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
+	|| write(fd, buf, buflen) != buflen
+	|| close(fd) < 0)
+	{
+		fprintf(stderr, "Error storing file %s: %s\n", argv[2], strerror(errno));
+		exit(2);
+ 	}
+
+	free(buf);
+
+	munmap(input_file,len);
+
+	return 0;
+}
-- 
2.30.2