firmware-utils: add nec-enc

nec-enc provides firmware encoding/decoding with model specific key
for NEC devices.

known devices:

  - Aterm WF1200CR
  - Aterm WG1200CR
  - Aterm WG2600HS

usage:

  nec-enc -i infile -o outfile -k key

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
[checkpatch fixes, marked usage as noreturn, added static function,
moved buf* from stack to the global data segment]

diff --git a/Makefile b/Makefile
index 864a3df15d8b87b84d150e4a8ef6e5f7886e4a05..7745b7bab20ad3c9658794dfc68c17e0635ccfe2 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -85,6 +85,7 @@ define Host/Compile
        $(call cc,mkdlinkfw mkdlinkfw-lib, -lz -Wall --std=c99)
        $(call cc,dns313-header, -Wall)
        $(call cc,mksercommfw, -Wall)
+       $(call cc,nec-enc, -Wall)
 endef
 
 define Host/Install

diff --git a/src/nec-enc.c b/src/nec-enc.c
new file mode 100644 (file)
index 0000000..3c4e387
--- /dev/null
+++ b/src/nec-enc.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * nec-enc.c - encode/decode nec firmware with key
+ *
+ * based on xorimage.c in OpenWrt
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#define KEY_LEN     16
+#define PATTERN_LEN 251
+
+static int
+xor_pattern(uint8_t *data, size_t len, const char *key, int k_len, int k_off)
+{
+       int offset = k_off;
+
+       while (len--) {
+               *data ^= key[offset];
+               data++;
+               offset = (offset + 1) % k_len;
+       }
+
+       return offset;
+}
+
+static void xor_data(uint8_t *data, size_t len, const uint8_t *pattern)
+{
+       for (int i = 0; i < len; i++) {
+               *data ^= pattern[i];
+               data++;
+       }
+}
+
+static void __attribute__((noreturn)) usage(void)
+{
+       fprintf(stderr, "Usage: nec-enc -i infile -o outfile -k <key>\n");
+       exit(EXIT_FAILURE);
+}
+
+static unsigned char buf_pattern[4096], buf[4096];
+
+int main(int argc, char **argv)
+{
+       int k_off = 0, ptn = 0, c, ret = EXIT_SUCCESS;
+       char *ifn = NULL, *ofn = NULL, *key = NULL;
+       size_t n, k_len;
+       FILE *out, *in;
+
+       while ((c = getopt(argc, argv, "i:o:k:h")) != -1) {
+               switch (c) {
+               case 'i':
+                       ifn = optarg;
+                       break;
+               case 'o':
+                       ofn = optarg;
+                       break;
+               case 'k':
+                       key = optarg;
+                       break;
+               case 'h':
+               default:
+                       usage();
+               }
+       }
+
+       if (optind != argc || optind == 1) {
+               fprintf(stderr, "illegal arg \"%s\"\n", argv[optind]);
+               usage();
+       }
+
+       in = fopen(ifn, "r");
+       if (!in) {
+               perror("can not open input file");
+               usage();
+       }
+
+       out = fopen(ofn, "w");
+       if (!out) {
+               perror("can not open output file");
+               usage();
+       }
+
+       if (!key) {
+               fprintf(stderr, "key is not specified\n");
+               usage();
+       }
+
+       k_len = strnlen(key, KEY_LEN + 1);
+       if (k_len == 0 || k_len > KEY_LEN) {
+               fprintf(stderr, "key length is not in range (0,%d)\n", KEY_LEN);
+               usage();
+       }
+
+       while ((n = fread(buf, 1, sizeof(buf), in)) > 0) {
+               for (int i = 0; i < n; i++) {
+                       buf_pattern[i] = ptn + 1;
+                       ptn++;
+
+                       if (ptn > 250)
+                               ptn = 0;
+               }
+
+               k_off = xor_pattern(buf_pattern, n, key, k_len, k_off);
+               xor_data(buf, n, buf_pattern);
+
+               if (fwrite(buf, 1, n, out) != n) {
+                       perror("failed to write");
+                       ret = EXIT_FAILURE;
+                       goto out;
+               }
+       }
+
+       if (ferror(in)) {
+               perror("failed to read");
+               ret = EXIT_FAILURE;
+               goto out;
+       }
+
+out:
+       fclose(in);
+       fclose(out);
+       return ret;
+}