#!/usr/bin/env python3

# https://github.com/mncoppola/ws30/blob/master/basefind.py

import gc
import os
import re
import signal
import struct
import sys
from operator import itemgetter

chars = "A-Za-z0-9/\\-:.,_$%'\"()[\]<> "
min_length = 10
scores = []
top_score = 0

regexp = bytes("[{}]{{{:d},}}".format(chars, min_length), "us-ascii")
pattern = re.compile(regexp)
regexpc = bytes("[{}]{{1,}}".format(chars), "us-ascii")
patternc = re.compile(regexpc)

def high_scores(signal, frame):
    print("\nTop 20 base address candidates:")
    for score in sorted(scores, key=itemgetter(1), reverse=True)[:20]:
        print("0x{:x}\t{:d}".format(*score))
    sys.exit(0)

def get_pointers(filename):
    table = {}
    with open(filename, "rb") as f:
        while True:
            try:
                value = struct.unpack("<L", f.read(4))[0]
                try:
                    table[value] += 1
                except KeyError:
                    table[value] = 1
            except:
                break
    return table

def get_strings(filename, size):
    table = set()
    offset = 0
    with open(filename, "rb") as f:
        while True:
            if offset >= size:
                break
            f.seek(offset)
            try:
                data = f.read(10)
            except:
                break
            match = pattern.match(data)
            if match:
                f.seek(offset - 1)
                try:
                    char = f.read(1)
                except:
                    continue
                if not patternc.match(char):
                    table.add(offset)
                    offset += len(match.group(0))
            offset += 1
    return table

if __name__ == "__main__":
    import argparse
    parser = argparse.ArgumentParser()
    def auto_int(x):
        return int(x, 0)
    parser.add_argument("--min_addr",  type=auto_int, help="start searching at this address", default=0)
    parser.add_argument("--max_addr",  type=auto_int, help="stop searching at this address", default=0xfe000000)
    parser.add_argument("--page_size", type=auto_int, help="search every this many byte", default=0x1000)
    parser.add_argument("infile", help="file to scan")
    args = parser.parse_args()

    size = os.path.getsize(args.infile)
    scores = []

    print("Scanning binary for strings...")
    str_table = get_strings(args.infile, size)
    print("Total strings found: {:d}".format(len(str_table)))

    print("Scanning binary for pointers...")
    ptr_table = get_pointers(args.infile)
    print("Total pointers found: {:d}".format(len(ptr_table)))

    gc.disable()
    signal.signal(signal.SIGINT, high_scores)

    for base in range(args.min_addr, args.max_addr, args.page_size):
        if base % ( args.page_size * 1000 ) == 0:
            print("Trying base address 0x{:x}".format(base))
            print("\u001b[F\u001b[K", end="")
        score = 0
        ptrs = list(ptr_table.keys())
        for ptr in ptrs:
            if ptr < base:
                #print("Removing pointer 0x{:x} from table".format(ptr))
                del ptr_table[ptr]
                continue
            if ptr >= (base + size):
                continue
            offset = ptr - base
            if offset in str_table:
                score += ptr_table[ptr]
        if score:
            scores.append((base, score))
            if score > top_score:
                top_score = score
                print("New highest score, 0x{:x}: {:d}".format(base, score))

    high_scores(0, 0)