Cudy router WR3000 /dev/mtd3 (bdinfo) decoder written in C for getting SN, MAC and WiFi PIN in OpenWrt or elsewhere (must be run on aarch64 system!)

bddecoder.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <openssl/des.h>

const unsigned char KEY[] = {0x97, 0x5e, 0x07, 0x19, 0xc4, 0xd5, 0x92, 0x79};

#define SKIP_BYTES 4
#define READ_SIZE 56700

char *trim(char *str) {
    char *end;

    while(isspace((unsigned char)*str)) str++;

    if(*str == 0) return str;

    end = str + strlen(str) - 1;
    while(end > str && isspace((unsigned char)*end)) end--;

    *(end+1) = 0;

    return str;
}

int main(int argc, char *argv[]) {
    const char *mtd_dev = "/dev/mtd3";
    if (argc > 1) {
        mtd_dev = argv[1];
    }

    FILE *f = fopen(mtd_dev, "rb");
    if (!f) {
        perror("Greska pri otvaranju uredjaja");
        return 1;
    }

    unsigned char *buffer = calloc(1, READ_SIZE + 1);
    if (!buffer) {
        printf("Greska: Nema memorije\n");
        fclose(f);
        return 1;
    }

    fseek(f, SKIP_BYTES, SEEK_SET);
    size_t read_bytes = fread(buffer, 1, READ_SIZE, f);
    fclose(f);

    DES_cblock key_block;
    DES_key_schedule schedule;
    memcpy(key_block, KEY, 8);
    DES_set_key_unchecked(&key_block, &schedule);
    DES_cblock iv = {0, 0, 0, 0, 0, 0, 0, 0};

    DES_ncbc_encrypt(buffer, buffer, READ_SIZE, &schedule, &iv, DES_DECRYPT);

    char *ptr = (char *)buffer;
    char *line_start = ptr;
    
    for (size_t i = 0; i < read_bytes; i++) {
        if (ptr[i] == '\n' || ptr[i] == '\r' || ptr[i] == '\0') {
            ptr[i] = '\0';
            
            if (strlen(line_start) > 0) {
                char *delimiter = strchr(line_start, '=');
                if (delimiter) {
                    *delimiter = '\0';
                    char *key = trim(line_start);
                    char *val = trim(delimiter + 1);

                    if (strcmp(key, "pin") == 0) {
                        printf("PIN: %s\n", val);
                    } else if (strcmp(key, "sn") == 0) {
                        printf("SN:  %s\n", val);
                    } else if (strcmp(key, "mac") == 0) {
                        printf("MAC: %s\n", val);
                    }
                }
            }
            line_start = ptr + i + 1;
        }
    }

    free(buffer);
    return 0;
}

build.sh

# sudo apt install build-essential libssl-dev
# must be run on aarch64 system!
gcc -static -o bddecoder bddecoder.c -lcrypto -Wno-deprecated-declarations