#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <libgen.h>
#include <getopt.h>
#include <stdarg.h>
#include <errno.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#if (__BYTE_ORDER == __BIG_ENDIAN)
#  define HOST_TO_BE32(x)       (x)
#  define BE32_TO_HOST(x)       (x)
#  define HOST_TO_LE32(x)       bswap_32(x)
#  define LE32_TO_HOST(x)       bswap_32(x)
#else
#  define HOST_TO_BE32(x)       bswap_32(x)
#  define BE32_TO_HOST(x)       bswap_32(x)
#  define HOST_TO_LE32(x)       (x)
#  define LE32_TO_HOST(x)       (x)
#endif

/* Fixed header flags */
#define HEADER_FLAGS            0x020e0000

/* Recognized Hardware ID magic */
#define HWID_HAME_MPR_A1_L8     0x32473352
#define HWID_PORAY_R50B         0x31353033
#define HWID_PORAY_R50D         0x33353033
#define HWID_PORAY_R50E         0x34353033
#define HWID_PORAY_M3           0x31353335
#define HWID_PORAY_M4           0x32353335
#define HWID_PORAY_Q3           0x33353335
#define HWID_PORAY_X5_X6        0x35353335
#define HWID_PORAY_X8           0x36353335
#define HWID_PORAY_X1           0x38353335
#define HWID_NEXX_WT1520        0x30353332
#define HWID_NEXX_WT3020        0x30323033
#define HWID_A5_V11             0x32473352

/* Recognized XOR obfuscation keys */
#define KEY_HAME                0
#define KEY_PORAY_1             1
#define KEY_PORAY_2             2
#define KEY_PORAY_3             3
#define KEY_PORAY_4             4
#define KEY_NEXX_1              5
#define KEY_NEXX_2              6
#define KEY_A5_V11              7

/* XOR key length */
#define KEY_LEN                 15

struct file_info {
        char            *file_name;     /* Name of the file */
        uint32_t        file_size;      /* Length of the file */
};

struct fw_header {
        uint32_t        hw_id;          /* Hardware id */
        uint32_t        firmware_len;   /* Firmware data length */
        uint32_t        flags;          /* Header flags */
        uint8_t         pad[16];
} __attribute__ ((packed));

struct flash_layout {
        char            *id;
        uint32_t        fw_max_len;
};

struct board_info {
        char            *id;
        uint32_t        hw_id;
        char            *layout_id;
        uint32_t        key;
};

/*
 * Globals
 */
static char *ofname;
static char *progname;

static char *board_id;
static struct board_info *board;
static char *layout_id;
static struct flash_layout *layout;
static char *opt_hw_id;
static uint32_t hw_id;
static struct file_info firmware_info;
static uint32_t firmware_len = 0;

static int inspect = 0;
static int extract = 0;

static uint8_t key[][KEY_LEN] = {
  {0xC8, 0x3C, 0x3A, 0x93, 0xA2, 0x95, 0xC3, 0x63, 0x48, 0x45, 0x58, 0x09, 0x12, 0x03, 0x08},
  {0x89, 0x6B, 0x5A, 0x93, 0x92, 0x95, 0xC3, 0x63, 0xD0, 0xA3, 0x9C, 0x92, 0x2E, 0xE6, 0xC7},
  {0xC9, 0x1C, 0x3A, 0x93, 0x92, 0x95, 0xC3, 0x63, 0xD0, 0xA3, 0x9C, 0x92, 0x2E, 0xE6, 0xC7},
  {0x19, 0x1B, 0x3A, 0x93, 0x92, 0x95, 0xC3, 0x63, 0xD0, 0xA3, 0x9C, 0x92, 0x2E, 0xE6, 0xC7},
  {0x79, 0x7B, 0x7A, 0x93, 0x92, 0x95, 0xC3, 0x63, 0xD0, 0xA3, 0x9C, 0x92, 0x2E, 0xE6, 0xC7},
  {0x19, 0x1C, 0x4A, 0x93, 0x96, 0x95, 0xC3, 0x63, 0xD0, 0xA3, 0x9C, 0x92, 0x2E, 0x16, 0xC6},
  {0x39, 0x1C, 0x4A, 0x93, 0x96, 0x95, 0xC3, 0x63, 0xD0, 0xA3, 0x9C, 0x92, 0x2E, 0x16, 0xC6},
  {0xC8, 0x3C, 0x3A, 0x93, 0xA2, 0x95, 0xC3, 0x63, 0x48, 0x45, 0x58, 0x09, 0x20, 0x11, 0x08},
};

static struct flash_layout layouts[] = {
        {
                .id             = "4M",
                .fw_max_len     = 0x3c0000,
        }, {
                .id             = "8M",
                .fw_max_len     = 0x7c0000,
        }, {
                .id             = "16M",
                .fw_max_len     = 0xf80000,
        }
};

static struct board_info boards[] = {
        {
                .id             = "A5-V11",
                .hw_id          = HWID_A5_V11,
                .layout_id      = "4M",
                .key            = KEY_A5_V11,
        }, {
                .id             = "MPR-A1",
                .hw_id          = HWID_HAME_MPR_A1_L8,
                .layout_id      = "4M",
                .key            = KEY_HAME,
        }, {
                .id             = "MPR-L8",
                .hw_id          = HWID_HAME_MPR_A1_L8,
                .layout_id      = "4M",
                .key            = KEY_HAME,
        }, {
                .id             = "R50B",
                .hw_id          = HWID_PORAY_R50B,
                .layout_id      = "4M",
                .key            = KEY_PORAY_2,
        }, {
                .id             = "R50D",
                .hw_id          = HWID_PORAY_R50D,
                .layout_id      = "4M",
                .key            = KEY_PORAY_3,
        }, {
                .id             = "R50E",
                .hw_id          = HWID_PORAY_R50E,
                .layout_id      = "4M",
                .key            = KEY_PORAY_4,
        }, {
                .id             = "M3",
                .hw_id          = HWID_PORAY_M3,
                .layout_id      = "4M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "M4",
                .hw_id          = HWID_PORAY_M4,
                .layout_id      = "4M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "Q3",
                .hw_id          = HWID_PORAY_Q3,
                .layout_id      = "4M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "X5 or X6",
                .hw_id          = HWID_PORAY_X5_X6,
                .layout_id      = "8M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "X5",
                .hw_id          = HWID_PORAY_X5_X6,
                .layout_id      = "8M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "X6",
                .hw_id          = HWID_PORAY_X5_X6,
                .layout_id      = "8M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "X8",
                .hw_id          = HWID_PORAY_X8,
                .layout_id      = "8M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "X1",
                .hw_id          = HWID_PORAY_X1,
                .layout_id      = "8M",
                .key            = KEY_PORAY_1,
        }, {
                .id             = "WT1520",
                .hw_id          = HWID_NEXX_WT1520,
                .layout_id      = "4M",
                .key            = KEY_NEXX_1,
        }, {
                .id             = "WT1520",
                .hw_id          = HWID_NEXX_WT1520,
                .layout_id      = "8M",
                .key            = KEY_NEXX_1,
        }, {
                .id             = "WT3020",
                .hw_id          = HWID_NEXX_WT3020,
                .layout_id      = "4M",
                .key            = KEY_NEXX_2,
        }, {
                .id             = "WT3020",
                .hw_id          = HWID_NEXX_WT3020,
                .layout_id      = "8M",
                .key            = KEY_NEXX_2,
        }, {
                .id             = "WT3020",
                .hw_id          = HWID_NEXX_WT3020,
                .layout_id      = "16M",
                .key            = KEY_NEXX_2,
        }, {



                /* terminating entry */
        }
};

/*
 * Message macros
 */
#define ERR(fmt, ...) do { \
        fflush(0); \
        fprintf(stderr, "[%s] *** error: " fmt "\n", \
                        progname, ## __VA_ARGS__ ); \
} while (0)

#define ERRS(fmt, ...) do { \
        int save = errno; \
        fflush(0); \
        fprintf(stderr, "[%s] *** error: " fmt ":%s\n", \
                        progname, ## __VA_ARGS__, strerror(save)); \
} while (0)

#define DBG(fmt, ...) do { \
        fprintf(stderr, "[%s] " fmt "\n", progname, ## __VA_ARGS__ ); \
} while (0)

/*
 * Find a board by its name
 */
static struct board_info *find_board(char *id)
{
        struct board_info *ret;
        struct board_info *board;

        ret = NULL;
        for (board = boards; board->id != NULL; board++){
                if (strcasecmp(id, board->id) == 0) {
                        ret = board;
                        break;
                }
        };

        return ret;
}

/*
 * Find a board by its hardware ID
 */
static struct board_info *find_board_by_hwid(uint32_t hw_id)
{
        struct board_info *board;

        for (board = boards; board->id != NULL; board++) {
                if (hw_id == board->hw_id)
                        return board;
        };

        return NULL;
}

/*
 * Find a Flash memory layout by its name
 */
static struct flash_layout *find_layout(char *id)
{
        struct flash_layout *ret;
        struct flash_layout *l;

        ret = NULL;
        for (l = layouts; l->id != NULL; l++){
                if (strcasecmp(id, l->id) == 0) {
                        ret = l;
                        break;
                }
        };

        return ret;
}

/*
 * Display usage
 */
static void usage(int status)
{
        FILE *stream = (status != EXIT_SUCCESS) ? stderr : stdout;

        fprintf(stream, "Usage: %s [OPTIONS...]\n", progname);
        fprintf(stream,
"\n"
"Options:\n"
"  -B <board>      create image for the board specified with <board>\n"
"  -H <hwid>       use hardware id specified with <hwid>\n"
"  -F <id>         use flash layout specified with <id>\n"
"  -f <file>       read firmware image from the file <file>\n"
"  -o <file>       write output to the file <file>\n"
"  -i              inspect given firmware file (requires -f)\n"
"  -x              extract combined kernel and rootfs while inspecting (implies -i)\n"
"  -h              show this screen\n"
        );

        exit(status);
}

/*
 * Get file statistics
 */
static int get_file_stat(struct file_info *fdata)
{
        struct stat st;
        int res;

        if (fdata->file_name == NULL) {
                return 0;
        }
        res = stat(fdata->file_name, &st);
        if (res){
                ERRS("stat failed on %s", fdata->file_name);
                return res;
        }

        fdata->file_size = st.st_size;
        return 0;
}

/*
 * Read file into buffer
 */
static int read_to_buf(struct file_info *fdata, uint8_t *buf)
{
        FILE *f;
        int ret = EXIT_FAILURE;

        f = fopen(fdata->file_name, "rb");
        if (f == NULL) {
                ERRS("could not open \"%s\" for reading", fdata->file_name);
                goto out;
        }

        errno = 0;
        fread(buf, fdata->file_size, 1, f);
        if (errno != 0) {
                ERRS("unable to read from file \"%s\"", fdata->file_name);
                goto out_close;
        }

        ret = EXIT_SUCCESS;

 out_close:
        fclose(f);
 out:
        return ret;
}

/*
 * Check command line options
 */
static int check_options(void)
{
        int ret;

        if (firmware_info.file_name == NULL) {
                ERR("no firmware image specified");
                return -1;
        }

        ret = get_file_stat(&firmware_info);
        if (ret)
                return ret;

        if (inspect)
                return 0;

        if (board_id == NULL && opt_hw_id == NULL) {
                ERR("either board or hardware id must be specified");
                return -1;
        }

        if (board_id) {
                board = find_board(board_id);
                if (board == NULL) {
                        ERR("unknown/unsupported board id \"%s\"", board_id);
                        return -1;
                }
                if (layout_id == NULL) {
                        layout_id = board->layout_id;
                }
                hw_id = board->hw_id;
        } else {
                hw_id = strtoul(opt_hw_id, NULL, 0);
                board = find_board_by_hwid(hw_id);
                if (layout_id == NULL) {
                        layout_id = board->layout_id;
                }
        }

        layout = find_layout(layout_id);
        if (layout == NULL) {
                ERR("unknown flash layout \"%s\"", layout_id);
                return -1;
        }

        firmware_len = firmware_info.file_size;

        if (firmware_info.file_size >
                layout->fw_max_len - sizeof (struct fw_header)) {
                ERR("firmware image is too big");
                return -1;
        }

        if (ofname == NULL) {
                ERR("no output file specified");
                return -1;
        }
        return 0;
}

/*
 * Fill in firmware header
 */
static void fill_header(uint8_t *buf)
{
        struct fw_header *hdr = (struct fw_header *) buf;

        memset(hdr, 0, sizeof (struct fw_header));
        hdr->hw_id = HOST_TO_LE32(hw_id);
        hdr->firmware_len = HOST_TO_LE32(firmware_len);
        hdr->flags = HOST_TO_LE32(HEADER_FLAGS);
}

/*
 * Compute firmware checksum
 */
static uint16_t checksum_fw(uint8_t *data, int len)
{
        int i;
        int32_t checksum = 0;

        for (i = 0; i < len - 1; i += 2) {
                checksum += (data[i + 1] << 8) | data[i];
        }
        if (i < len) {
                checksum += data[i];
        }
        checksum = checksum + (checksum >> 16) + 0xffff;
        checksum = ~(checksum + (checksum >> 16)) & 0xffff;
        return (uint16_t) checksum;
}

/*
 * (De)obfuscate firmware using an XOR operation with a fixed length key
 */
static void xor_fw(uint8_t *data, int len)
{
        int i;

        for (i = 0; i <= len; i++) {
                data[i] ^= key[board->key][i % KEY_LEN];
        }
}

/*
 * Write firmware to file
 */
static int write_fw(uint8_t *data, int len)
{
        FILE *f;
        int ret = EXIT_FAILURE;

        f = fopen(ofname, "wb");
        if (f == NULL) {
                ERRS("could not open \"%s\" for writing", ofname);
                goto out;
        }

        errno = 0;
        fwrite(data, len, 1, f);
        if (errno) {
                ERRS("unable to write output file");
                goto out_flush;
        }

        DBG("firmware file \"%s\" completed", ofname);

        ret = EXIT_SUCCESS;

 out_flush:
        fflush(f);
        fclose(f);
        if (ret != EXIT_SUCCESS) {
                unlink(ofname);
        }
 out:
        return ret;
}

/*
 * Build firmware file
 */
static int build_fw(void)
{
        int buflen;
        uint8_t *buf, *p;
        int ret = EXIT_FAILURE;
        int writelen = 0;
        uint16_t checksum;

        buflen = layout->fw_max_len;

        buf = (uint8_t *) malloc(buflen);
        if (!buf) {
                ERR("no memory for buffer\n");
                goto out;
        }

        memset(buf, 0xff, buflen);
        p = buf + sizeof (struct fw_header);
        ret = read_to_buf(&firmware_info, p);
        if (ret) {
                goto out_free_buf;
        }
        writelen = sizeof (struct fw_header) + firmware_len + 2;

        /* Fill in header */
        fill_header(buf);

        /* Compute firmware checksum */
        checksum = checksum_fw(buf + sizeof (struct fw_header), firmware_len);

        /* Cannot use network order function because checksum is not word-aligned */
        buf[writelen - 1] = checksum >> 8;
        buf[writelen - 2] = checksum & 0xff;

        /* XOR obfuscate firmware */
        xor_fw(buf + sizeof (struct fw_header), firmware_len + 2);

        /* Write firmware file */
        ret = write_fw(buf, writelen);
        if (ret) {
                goto out_free_buf;
        }
        ret = EXIT_SUCCESS;

 out_free_buf:
        free(buf);
 out:
        return ret;
}

/* Helper functions to inspect_fw() representing different output formats */
static inline void inspect_fw_pstr(char *label, char *str)
{
        printf("%-23s: %s\n", label, str);
}

static inline void inspect_fw_phex(char *label, uint32_t val)
{
        printf("%-23s: 0x%08x\n", label, val);
}

static inline void inspect_fw_phexpost(char *label,
                                       uint32_t val, char *post)
{
        printf("%-23s: 0x%08x (%s)\n", label, val, post);
}

static inline void inspect_fw_phexdef(char *label,
                                      uint32_t val, uint32_t defval)
{
        printf("%-23s: 0x%08x                  ", label, val);

        if (val == defval) {
                printf("(== OpenWrt default)\n");
        } else {
                printf("(OpenWrt default: 0x%08x)\n", defval);
        }
}

static inline void inspect_fw_phexexp(char *label,
                                      uint32_t val, uint32_t expval)
{
        printf("%-23s: 0x%08x ", label, val);

        if (val == expval) {
                printf("(ok)\n");
        } else {
                printf("(expected: 0x%08x)\n", expval);
        }
}

static inline void inspect_fw_phexdec(char *label, uint32_t val)
{
        printf("%-23s: 0x%08x / %8u bytes\n", label, val, val);
}

static inline void inspect_fw_pchecksum(char *label,
                                        uint16_t val, uint16_t expval)
{
        printf("%-23s: 0x%04x     ", label, val);
        if (val == expval) {
                printf("(ok)\n");
        } else {
                printf("(expected: 0x%04x)\n", expval);
        }
}

static int inspect_fw(void)
{
        uint8_t *buf;
        struct fw_header *hdr;
        int ret = EXIT_FAILURE;
        uint16_t computed_checksum, file_checksum;

        buf = (uint8_t *) malloc(firmware_info.file_size);
        if (!buf) {
                ERR("no memory for buffer!\n");
                goto out;
        }

        ret = read_to_buf(&firmware_info, buf);
        if (ret) {
                goto out_free_buf;
        }
        hdr = (struct fw_header *)buf;

        inspect_fw_pstr("File name", firmware_info.file_name);
        inspect_fw_phexdec("File size", firmware_info.file_size);

        printf("\n");

        inspect_fw_phexdec("Header size", sizeof (struct fw_header));
        board = find_board_by_hwid(LE32_TO_HOST(hdr->hw_id));
        if (board) {
                layout = find_layout(board->layout_id);
                inspect_fw_phexpost("Hardware ID",
                                    LE32_TO_HOST( hdr->hw_id), board->id);
        } else {
                inspect_fw_phexpost("Hardware ID",
                                    LE32_TO_HOST(hdr->hw_id), "unknown");
        }
        inspect_fw_phexdec("Firmware data length",
                           LE32_TO_HOST(hdr->firmware_len));

        inspect_fw_phexexp("Flags",
                           LE32_TO_HOST(hdr->flags), HEADER_FLAGS);
        printf("\n");

        /* XOR unobfuscate firmware */
        xor_fw(buf + sizeof (struct fw_header), LE32_TO_HOST(hdr->firmware_len) + 2);

        /* Compute firmware checksum */
        computed_checksum = checksum_fw(buf + sizeof (struct fw_header), LE32_TO_HOST(hdr->firmware_len));

        /* Cannot use network order function because checksum is not word-aligned */
        file_checksum = (buf[firmware_info.file_size - 1] << 8) | buf[firmware_info.file_size - 2];
        inspect_fw_pchecksum("Firmware checksum", computed_checksum, file_checksum);

        /* Verify checksum */
        if (computed_checksum != file_checksum) {
                ret = -1;
                ERR("checksums do not match");
                goto out_free_buf;
        }

        printf("\n");

        if (extract) {
                FILE *fp;
                char *filename;

                if (ofname == NULL) {
                        filename = malloc(strlen(firmware_info.file_name) + 10);
                        sprintf(filename, "%s-firmware", firmware_info.file_name);
                } else {
                        filename = ofname;
                }
                printf("Extracting firmware to \"%s\"...\n", filename);
                fp = fopen(filename, "wb");
                if (fp) {
                  if (!fwrite(buf + sizeof (struct fw_header),
                                    LE32_TO_HOST(hdr->firmware_len), 1, fp)) {
                                ERRS("error in fwrite(): %s", strerror(errno));
                        }
                        fclose(fp);
                } else {
                        ERRS("error in fopen(): %s", strerror(errno));
                }
                if (ofname == NULL) {
                        free(filename);
                }
                printf("\n");
        }

 out_free_buf:
        free(buf);
 out:
        return ret;
}

/*
 * Main entry point
 */
int main(int argc, char *argv[])
{
        int ret = EXIT_FAILURE;

        progname = basename(argv[0]);

        int c;

        while ((c = getopt(argc, argv, "B:H:F:f:o:ixh")) != -1) {
                switch (c) {
                case 'B':
                        board_id = optarg;
                        break;
                case 'H':
                        opt_hw_id = optarg;
                        break;
                case 'F':
                        layout_id = optarg;
                        break;
                case 'f':
                        firmware_info.file_name = optarg;
                        break;
                case 'o':
                        ofname = optarg;
                        break;
                case 'i':
                        inspect = 1;
                        break;
                case 'x':
                        inspect = 1;
                        extract = 1;
                        break;
                case 'h':
                        usage(EXIT_SUCCESS);
                        break;
                default:
                        usage(EXIT_FAILURE);
                        break;
                }
        }

        ret = check_options();
        if (ret) {
                goto out;
        }
        if (!inspect) {
                ret = build_fw();
        } else {
                ret = inspect_fw();
        }

 out:
        return ret;
}