2016-03-27 23:04:33 +03:00
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#!/usr/bin/env ruby
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2017-09-19 03:43:21 +03:00
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require 'unicorn_engine'
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require 'unicorn_engine/x86_const'
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2016-03-27 23:04:33 +03:00
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2017-09-19 03:43:21 +03:00
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include UnicornEngine
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2016-03-27 23:04:33 +03:00
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F_GRANULARITY = 0x8
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F_PROT_32 = 0x4
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F_LONG = 0x2
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F_AVAILABLE = 0x1
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A_PRESENT = 0x80
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A_PRIV_3 = 0x60
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A_PRIV_2 = 0x40
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A_PRIV_1 = 0x20
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A_PRIV_0 = 0x0
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2017-08-29 13:03:52 +03:00
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A_CODE = 0x8
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A_DATA = 0x0
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2016-03-27 23:04:33 +03:00
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A_TSS = 0x0
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A_GATE = 0x0
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A_DATA_WRITABLE = 0x2
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A_CODE_READABLE = 0x2
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A_DIR_CON_BIT = 0x4
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S_GDT = 0x0
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S_LDT = 0x4
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S_PRIV_3 = 0x3
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S_PRIV_2 = 0x2
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S_PRIV_1 = 0x1
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S_PRIV_0 = 0x0
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def create_selector(idx, flags)
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to_ret = flags
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to_ret |= idx << 3
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return to_ret
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end
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def create_gdt_entry(base, limit, access, flags)
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to_ret = limit & 0xffff;
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to_ret |= (base & 0xffffff) << 16;
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to_ret |= (access & 0xff) << 40;
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to_ret |= ((limit >> 16) & 0xf) << 48;
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to_ret |= (flags & 0xff) << 52;
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to_ret |= ((base >> 24) & 0xff) << 56;
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return [to_ret].pack('Q')
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end
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def write_gdt(uc, gdt, mem)
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gdt.each_index do |idx|
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offset = idx * GDT_ENTRY_SIZE
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uc.mem_write(mem + offset, gdt[idx])
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end
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end
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CODE_ADDR = 0x40000
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CODE_SIZE = 0x1000
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GDT_ADDR = 0x3000
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GDT_LIMIT = 0x1000
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GDT_ENTRY_SIZE = 0x8
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GS_SEGMENT_ADDR = 0x5000
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GS_SEGMENT_SIZE = 0x1000
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uc = Uc.new UC_ARCH_X86, UC_MODE_32
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uc.mem_map(GDT_ADDR, GDT_LIMIT)
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uc.mem_map(GS_SEGMENT_ADDR, GS_SEGMENT_SIZE)
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uc.mem_map(CODE_ADDR, CODE_SIZE)
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gdt = Array.new (31) {|i| create_gdt_entry(0,0,0,0)}
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gdt[15] = create_gdt_entry(GS_SEGMENT_ADDR, GS_SEGMENT_SIZE, A_PRESENT | A_DATA | A_DATA_WRITABLE | A_PRIV_3 | A_DIR_CON_BIT, F_PROT_32)
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gdt[16] = create_gdt_entry(0, 0xfffff000 , A_PRESENT | A_DATA | A_DATA_WRITABLE | A_PRIV_3 | A_DIR_CON_BIT, F_PROT_32) # Data Segment
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gdt[17] = create_gdt_entry(0, 0xfffff000 , A_PRESENT | A_CODE | A_CODE_READABLE | A_PRIV_3 | A_DIR_CON_BIT, F_PROT_32) # Code Segment
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gdt[18] = create_gdt_entry(0, 0xfffff000 , A_PRESENT | A_DATA | A_DATA_WRITABLE | A_PRIV_0 | A_DIR_CON_BIT, F_PROT_32) # Stack Segment
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write_gdt(uc, gdt, GDT_ADDR)
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uc.reg_write(UC_X86_REG_GDTR, [0, GDT_ADDR, gdt.length * GDT_ENTRY_SIZE-1, 0x0])
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selector = create_selector(15, S_GDT | S_PRIV_3)
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uc.reg_write(UC_X86_REG_GS, selector)
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selector = create_selector(16, S_GDT | S_PRIV_3)
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uc.reg_write(UC_X86_REG_DS, selector)
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selector = create_selector(17, S_GDT | S_PRIV_3)
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uc.reg_write(UC_X86_REG_CS, selector)
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selector = create_selector(18, S_GDT | S_PRIV_0)
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uc.reg_write(UC_X86_REG_SS, selector)
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