strings f1vm_32bit | grep -i flag No direct flag. But there’s a section: [+] Flag is encrypted in VM memory.
f1vm_32bit (ELF 32-bit executable) 2. Initial Analysis file f1vm_32bit Output:
enc = bytes.fromhex("25 73 12 45 9A 34 22 11 ...") key = 0xDEADBEEF flag = '' for i, b in enumerate(enc): shift = (i * 8) % 32 key_byte = (key >> shift) & 0xFF flag += chr(b ^ key_byte) print(flag) Output: f1vm 32 bit
| Opcode | Mnemonic | Operands | |--------|--------------|-------------------------| | 0x01 | MOV reg, imm | reg (1 byte), imm (4 bytes) | | 0x02 | ADD reg, reg | src, dst | | 0x03 | XOR reg, reg | | | 0x10 | PUSH reg | | | 0x11 | POP reg | | | 0x20 | JMP addr | 4-byte address | | 0x21 | JZ addr | jump if reg0 == 0 | | 0xFF | HALT | |
25 73 12 45 9A 34 22 11 ... – that’s the encrypted flag. Write a simple emulator in Python to trace execution without actually running the binary. strings f1vm_32bit | grep -i flag No direct flag
Run the binary:
The VM initializes reg0 as the bytecode length, reg1 as the starting address of encrypted flag. The flag is likely embedded as encrypted bytes in the VM’s memory[] . In the binary, locate the .rodata section – there’s a 512-byte chunk starting at 0x804B040 containing the bytecode + encrypted data. Initial Analysis file f1vm_32bit Output: enc = bytes
./f1vm_32bit Output:
