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March 2, 2026 21:03
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legacy ARM compiler's ORC to ELF converter
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| """ | |
| Origin unknown (local timestamp 04/06/2020) | |
| """ | |
| def derive_key(n): | |
| from cryptography.hazmat.backends import default_backend | |
| import cryptography.hazmat.primitives.hashes as hashes | |
| digest = hashes.Hash(hashes.SHA1(), backend=default_backend()) | |
| digest.update(n.to_bytes(4, "little")) | |
| return digest.finalize() | |
| def derive_section_row_key(write_addr, rown): | |
| c = write_addr * 0x4C - 1 + rown * 0x140 | |
| return derive_key(c) | |
| def derive_symtab_row_key(nent, rown): | |
| c = (nent * 4 - rown) * 0x520 | |
| return derive_key(c) | |
| def scramble_memory_buf(buf, keystream, encrypt): | |
| bufsize = len(buf) | |
| indicies = list(range(0, len(buf))) | |
| # Create an array of selections from an index vector | |
| transpose_table = [ | |
| indicies.pop(keystream[(idx - 1) % len(keystream)] % len(indicies)) | |
| for idx in reversed(range(len(buf))) | |
| ] | |
| output = [0] * len(buf) | |
| for idx in range(len(buf)): | |
| if encrypt: | |
| output[transpose_table[idx]] = buf[idx] | |
| else: | |
| output[idx] = buf[transpose_table[idx]] | |
| return output | |
| def scramble_section_row(buf, write_addr, rown, encrypt): | |
| assert len(buf) == 0x28 | |
| keystream = derive_section_row_key(write_addr, rown) | |
| return scramble_memory_buf(buf, keystream, encrypt) | |
| def scramble_symtab_row(buf, nent, rown, encrypt): | |
| assert len(buf) == 0x10 | |
| keystream = derive_symtab_row_key(nent, rown) | |
| return scramble_memory_buf(buf, keystream, encrypt) | |
| def decode_file(fname, sym_shuffle_after): | |
| d = open(fname, "rb").read() | |
| new_d = bytearray(d) | |
| new_d[:4] = b"\x7FELF" | |
| new_d[0x12:0x14] = b"\x28\x00" | |
| e_shoff = int.from_bytes(d[0x20:0x24], "little") | |
| e_shentsize = int.from_bytes(d[0x2E:0x30], "little") | |
| e_shnum = int.from_bytes(d[0x30:0x32], "little") | |
| symtab = None | |
| for i in range(e_shnum): | |
| ba = e_shoff + i * e_shentsize | |
| rowd = d[ba: ba + e_shentsize] | |
| unscramble = scramble_section_row(rowd, e_shoff, i, True) | |
| #print(" ".join("%02x" % i for i in unscramble)) | |
| new_d[ba: ba+e_shentsize] = unscramble | |
| sh_type = int.from_bytes(unscramble[0x4:0x8], "little") | |
| # if symtab | |
| if sh_type == 2: | |
| sh_offset = int.from_bytes(unscramble[0x10:0x14], "little") | |
| sh_size = int.from_bytes(unscramble[0x14:0x18], "little") | |
| symtab = sh_offset, sh_size | |
| print("symtab at %08x size = %08x" % (sh_offset, sh_size)) | |
| if symtab is not None: | |
| symtab_base, symtab_size = symtab | |
| assert symtab_size % 0x10 == 0 | |
| nmemb = symtab_size // 0x10 | |
| for idx in range(nmemb): | |
| ba = symtab_base + 0x10 * idx | |
| row = d[ba:ba+0x10] | |
| if idx > sym_shuffle_after: | |
| row = scramble_symtab_row(row, nmemb, idx, True) | |
| new_d[ba:ba+0x10]=row | |
| #print(" ".join("%02x" % i for i in row)) | |
| open(fname + ".elf", "wb").write(new_d) | |
| import sys | |
| decode_file(sys.argv[1], 14) |
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