132 lines
2.4 KiB
ArmAsm
132 lines
2.4 KiB
ArmAsm
bits 64
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global _start
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_start:
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push rbp
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push rsp
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push rbx
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push r12
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push r13
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push r14
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push r15
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mov rdi, 1
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lea rsi, [rel msg]
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mov rbx, rsi
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sub rbx, qword [rel text_section] ;text_section address because of this and that
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mov r8, qword [rel section_size] ;text_section size
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shr r8, 2
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inc r8
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inc r8
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inc r8
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inc r8
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mov r9, 0 ;increment register
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mov r10, 0 ;increment register
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xor r10, r10
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xor r13, r13
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mov r13d, dword [rel private_key]
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xor r12, r12
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mov r12d, dword [rel private_key + 4]
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;shr r12, 32
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push r13 ; push rsa.d
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push r12 ; push rsa.n
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jmp decrypt_loop
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; rbx is adress of text(encrypted) section
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; r8 is section size
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; r9 is index
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; rax is cypher that needs to be converted to message
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; dword [rsp + 16] is rsa.d
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; dword [rsp + 8] is rsa.n
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; qword [rsp] is cypher backup
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decrypt_once:
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mov r11, 0x100000000
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sq_mul_bit_index:
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shr r11, 1
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mov r12, r11
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and r12, qword [rsp + 16]
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jz sq_mul_bit_index
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sq_mul_loop:
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shr r11, 1
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cmp r11, 0
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je decrypt_loop2
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mul rax,
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; modulo n ...
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mov r13, qword [rsp + 8]
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xor rdx, rdx
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div r13
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mov rax, rdx
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; modulo n ...
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mov r12, r11
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and r12, qword [rsp + 16]
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cmp r12, 0
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je sq_mul_loop
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mov r13, qword [rsp]
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mul r13
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; modulo n ...
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mov r13, qword [rsp + 8]
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xor rdx, rdx
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div r13
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mov rax, rdx
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; modulo n ...
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jmp sq_mul_loop
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decrypt_loop:
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cmp r8, r10
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je end_decrypt
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xor rax, rax
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mov eax, dword [rbx + r9]
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push rax
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;push r10
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jmp decrypt_once
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decrypt_loop2:
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sub rax, 42 ; remove 42 of result (avoid 0 values)
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sub rax, r10 ; remove index of result (caesar like cypher so 0/42 values are differents)
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; unpadding and write back here
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mov dword [rbx + r9], 0
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mov rcx, r10
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mov r15, r10
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shr r15, 5
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shl r15, 2
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inc rcx
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shl rcx, 59
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shr rcx, 59
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shl rax, cl
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mov r14, r9
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sub r14, r15
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add [rbx + r14], eax
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mov rcx, rax
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shr rcx, 32
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cmp r9, 0
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je first_block_skip
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add [rbx + r14 - 4], ecx
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first_block_skip:
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; unpadding and write back here
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pop rax
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add r9, 4
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inc r10
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jmp decrypt_loop
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end_decrypt:
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mov rdx, 14
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mov rax, 1
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syscall
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pop r12 ; pop rsa.n
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pop r12 ; pop rsa.d
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pop r15
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pop r14
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pop r13
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pop r12
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pop rbx
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pop rsp
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pop rbp
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jmp 0xdadadada ; this needs to be just before that
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msg db "....WOODY....",10 ; that needs to be just after this
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text_section dq 0xbabababababababa
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section_size dq 0xcacacacacacacaca
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private_key dq 0xabcdefabcdefabcd
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