// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * nosimg-enc.c - encode/decode "nos.img" image for XikeStor SKS8300 series
 */

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define ENCODE_BLKLEN	0x100
#define ENCODE_BLOCKS	2

static const uint8_t key[ENCODE_BLKLEN] = {
	0xee, 0xdd, 0xcc, 0x21, 0x53, 0x55, 0xee, 0xcc,
	0xdd, 0x55, 0x80, 0x7e, 0x00, 0x00, 0x00, 0x00,
	0xcd, 0xbd, 0xdf, 0xae, 0xbb, 0x9b, 0x89, 0x01,
	0x70, 0xe5, 0xcc, 0xdd, 0xf6, 0xfc, 0x83, 0x64,
	0xec, 0xdd, 0xce, 0xf1, 0xe3, 0x54, 0xfe, 0xd0,
	0xbd, 0xab, 0xdd, 0xe1, 0xe4, 0xb4, 0xd5, 0x83,
	0xed, 0xfe, 0xd0, 0xcd, 0xb6, 0x55, 0xcc, 0xa3,
	0xed, 0xd5, 0xc6, 0x7e, 0xdd, 0xcc, 0x21, 0x53,
	0xec, 0x4d, 0xdc, 0x00, 0x53, 0x55, 0xcd, 0xc3,
	0x22, 0x01, 0x80, 0x7e, 0xef, 0xbc, 0x75, 0x66,
	0xa6, 0xc0, 0xcc, 0x2f, 0xfe, 0xd0, 0xee, 0xcc,
	0xdd, 0x55, 0x01, 0x01, 0x01, 0x01, 0xc5, 0x64,
	0x99, 0x45, 0xab, 0x32, 0x55, 0x80, 0x7e, 0xef,
	0x55, 0x80, 0x7e, 0xef, 0xbc, 0x75, 0x66, 0x89,
	0xe3, 0x1d, 0x83, 0xdd, 0xfe, 0x55, 0x8e, 0xab,
	0x7d, 0x55, 0x80, 0x7e, 0xff, 0x01, 0xac, 0x66,
	0x0e, 0xc9, 0x92, 0xd9, 0x73, 0xe5, 0x01, 0x01,
	0xbd, 0xe5, 0x10, 0xce, 0x01, 0x01, 0xba, 0xe8,
	0x3e, 0xdd, 0x81, 0xa1, 0x53, 0x33, 0x01, 0x01,
	0x9a, 0xc5, 0x10, 0xaa, 0x01, 0xce, 0x8a, 0xe1,
	0xb1, 0xfb, 0x00, 0x80, 0x53, 0x77, 0x00, 0x00,
	0x70, 0xdc, 0x00, 0x01, 0x00, 0x00, 0xcb, 0xb1,
	0xa0, 0x30, 0x00, 0x00, 0x55, 0xa6, 0x00, 0x00,
	0xca, 0xbd, 0x01, 0x01, 0x00, 0x00, 0xc9, 0xb2,
	0x81, 0x90, 0x01, 0x00, 0x5a, 0x21, 0x00, 0x01,
	0x79, 0xbc, 0x01, 0x00, 0x78, 0x00, 0x7b, 0xb3,
	0xd4, 0x97, 0x01, 0x00, 0x53, 0x55, 0xa9, 0xfc,
	0xdd, 0xa5, 0x01, 0xbe, 0xaf, 0xc1, 0x75, 0xc5,
	0x8e, 0xd7, 0x77, 0x00, 0x55, 0xd0, 0x0d, 0xac,
	0x01, 0x55, 0x80, 0x7e, 0xef, 0xbc, 0x7e, 0xe6,
	0xf1, 0x6c, 0x52, 0x00, 0x33, 0x16, 0x98, 0xcc,
	0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x79, 0x88,
};

static void __attribute__((noreturn)) usage(void)
{
	fprintf(stderr, "Usage: nosimg-enc -i infile -o outfile [-d]\n");
	exit(EXIT_FAILURE);
}

static void encode_block(uint8_t *data, bool decode)
{
	int i;

	for (i = 0; i < ENCODE_BLKLEN; i++)
		data[i] -= key[i] * (decode ? -1 : 1);
}

int main(int argc, char **argv)
{
	int i, c, n, ret = EXIT_SUCCESS;
	char *ifn = NULL, *ofn = NULL;
	bool decode = false;
	uint8_t buf[0x1000];
	FILE *out, *in;

	while ((c = getopt(argc, argv, "i:o:dh")) != -1) {
		switch (c) {
		case 'i':
			ifn = optarg;
			break;
		case 'o':
			ofn = optarg;
			break;
		case 'd':
			decode = true;
			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();
	}

	/* encode/decode the first 512 bytes (0x100 x2) */
	for (i = 0; i < ENCODE_BLOCKS; i++) {
		n = fread(buf, 1, ENCODE_BLKLEN, in);
		if (n < ENCODE_BLKLEN) {
			fprintf(stderr,
				"failed to read data for encoding/decoding\n");
			ret = EXIT_FAILURE;
			goto out;
		}

		encode_block(buf, decode);
		fwrite(buf, 1, ENCODE_BLKLEN, out);
	}

	/* copy the remaining data */
	while ((n = fread(buf, 1, sizeof(buf), in)) > 0) {
		if (fwrite(buf, 1, n, out) != n) {
			fprintf(stderr, "failed to write");
			ret = EXIT_FAILURE;
			goto out;
		}
	}

	if (ferror(in)) {
		perror("failed to read");
		ret = EXIT_FAILURE;
	}

out:
	fclose(in);
	fclose(out);
	return ret;
}