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72 lines
2.6 KiB
72 lines
2.6 KiB
#pragma once
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#include <obf/pass.hpp>
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namespace theo::obf {
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/// <summary>
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/// This pass is used to generate transformations and jmp code to change RIP to
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/// the next instruction.
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///
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/// given the following code (get pml4 address from cr3):
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///
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/// get_pml4:
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/// 0: 48 c7 c0 ff 0f 00 00 mov rax,0xfff
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/// 7: 48 f7 d0 not rax
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/// a: 0f 20 da mov rdx,cr3
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/// d: 48 21 c2 and rdx,rax
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/// 10: b1 00 mov cl,0x0
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/// 12: 48 d3 e2 shl rdx,cl
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/// 15: 48 89 d0 mov rax,rdx
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/// 18: c3 ret
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///
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/// this pass will break up each instruction so that it can be anywhere in a
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/// linear virtual address space. this pass will not work on rip relative code,
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/// however clang will not generate such code when compiled with
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/// "-mcmodel=large"
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///
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/// get_pml4@0:
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/// mov rax, 0xFFF
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/// push [next_inst_addr_enc]
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/// xor [rsp], 0x3243342
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/// ; a random number of transformations here...
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/// ret
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/// next_inst_addr_enc:
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/// ; encrypted address of the next instruction goes here.
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///
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/// get_pml4@7:
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/// not rax
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/// push [next_inst_addr_enc]
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/// xor [rsp], 0x93983498
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/// ; a random number of transformations here...
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/// ret
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/// next_inst_addr_enc:
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/// ; encrypted address of the next instruction goes here.
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///
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/// this process is continued for each instruction in the function. the last
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/// instruction "ret" will have no code generated for it as there is no next
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/// instruction.
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///
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///
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/// this pass also only runs at the instruction level, theodosius internally
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/// breaks up functions inside of the ".split" section into individual
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/// instruction symbols. this process also creates a psuedo relocation which
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/// simply tells this pass that there needs to be a relocation to the next
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/// symbol. the offset for these psuedo relocations is zero.
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/// </summary>
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class next_inst_pass_t : public pass_t {
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explicit next_inst_pass_t() : pass_t(decomp::sym_type_t::instruction) {
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xed_state_t istate{XED_MACHINE_MODE_LONG_64, XED_ADDRESS_WIDTH_64b};
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xed_decoded_inst_zero_set_mode(&m_tmp_inst, &istate);
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xed_decode(&m_tmp_inst, m_type_inst_bytes, sizeof(m_type_inst_bytes));
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};
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public:
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static next_inst_pass_t* get();
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void run(decomp::symbol_t* sym);
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private:
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std::optional<recomp::reloc_t*> has_next_inst_reloc(decomp::symbol_t*);
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xed_decoded_inst_t m_tmp_inst;
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std::uint8_t m_type_inst_bytes[9] = {0x48, 0xC7, 0x44, 0x24, 0x08,
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0x44, 0x33, 0x22, 0x11};
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};
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} // namespace theo::obf
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