Quick introduction to reverse engineering for beginners

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.text:64404FF7 push offset aLoggingActivat ; "logging activated\n" .text:64404FFC mov ecx, edi ; demangled name: ATL::CStringT::operator+=(char const *) .text:64404FFE call ds:mfc90_945 .text:64405004 mov [ebp+var_10], ebx .text:64405007 .text:64405007 loc_64405007: .text:64405007 cmp byte ptr [esi+3Dh], 0 .text:6440500B jz short bypass .text:6440500D push offset aDataCompressio ; "data compression switched off\n" .text:64405012 mov ecx, edi ; demangled name: ATL::CStringT::operator+=(char const *) .text:64405014 call ds:mfc90_945 .text:6440501A mov [ebp+var_10], ebx .text:6440501D .text:6440501D bypass: .text:6440501D mov eax, [esi+20h] .text:64405020 test eax, eax .text:64405022 jz short loc_6440503A .text:64405024 cmp dword ptr [eax+28h], 0 .text:64405028 jz short loc_6440503A .text:6440502A push offset aDataRecordMode ; "data record mode switched on\n" .text:6440502F mov ecx, edi ; demangled name: ATL::CStringT::operator+=(char const *) .text:64405031 call ds:mfc90_945 .text:64405037 mov [ebp+var_10], ebx .text:6440503A .text:6440503A loc_6440503A: .text:6440503A .text:6440503A mov ecx, edi .text:6440503C cmp [ebp+var_10], ebx .text:6440503F jnz loc_64405142 .text:64405045 push offset aForMaximumData ; "\nFor maximum data security delete\nthe s"... ; demangled name: ATL::CStringT::operator+=(char const *) .text:6440504A call ds:mfc90_945 .text:64405050 xor edi, edi .text:64405052 push edi ; fWinIni .text:64405053 lea eax, [ebp+pvParam] .text:64405056 push eax ; pvParam .text:64405057 push edi ; uiParam .text:64405058 push 30h ; uiAction .text:6440505A call ds:SystemParametersInfoA .text:64405060 mov eax, [ebp+var_34] .text:64405063 cmp eax, 1600 .text:64405068 jle short loc_64405072 .text:6440506A cdq .text:6440506B sub eax, edx 189
.text:6440506D sar eax, 1 .text:6440506F mov [ebp+var_34], eax .text:64405072 .text:64405072 loc_64405072: .text:64405072 push edi ; hWnd .text:64405073 mov [ebp+cy], 0A0h .text:6440507A call ds:GetDC .text:64405080 mov [ebp+var_10], eax .text:64405083 mov ebx, 12Ch .text:64405088 cmp eax, edi .text:6440508A jz loc_64405113 .text:64405090 push 11h ; i .text:64405092 call ds:GetStockObject .text:64405098 mov edi, ds:SelectObject .text:6440509E push eax ; h .text:6440509F push [ebp+var_10] ; hdc .text:644050A2 call edi ; SelectObject .text:644050A4 and [ebp+rc.left], 0 .text:644050A8 and [ebp+rc.top], 0 .text:644050AC mov [ebp+h], eax .text:644050AF push 401h ; format .text:644050B4 lea eax, [ebp+rc] .text:644050B7 push eax ; lprc .text:644050B8 lea ecx, [esi+2854h] .text:644050BE mov [ebp+rc.right], ebx .text:644050C1 mov [ebp+rc.bottom], 0B4h ; demangled name: ATL::CSimpleStringT::GetLength(void) .text:644050C8 call ds:mfc90_3178 .text:644050CE push eax ; cchText .text:644050CF lea ecx, [esi+2854h] ; demangled name: const char* ATL::CSimpleStringT::operator PCXSTR .text:644050D5 call ds:mfc90_910 .text:644050DB push eax ; lpchText .text:644050DC push [ebp+var_10] ; hdc .text:644050DF call ds:DrawTextA .text:644050E5 push 4 ; nIndex .text:644050E7 call ds:GetSystemMetrics .text:644050ED mov ecx, [ebp+rc.bottom] .text:644050F0 sub ecx, [ebp+rc.top] .text:644050F3 cmp [ebp+h], 0 .text:644050F7 lea eax, [eax+ecx+28h] .text:644050FB mov [ebp+cy], eax .text:644050FE jz short loc_64405108 .text:64405100 push [ebp+h] ; h .text:64405103 push [ebp+var_10] ; hdc .text:64405106 call edi ; SelectObject .text:64405108 .text:64405108 loc_64405108: .text:64405108 push [ebp+var_10] ; hDC .text:6440510B push 0 ; hWnd .text:6440510D call ds:ReleaseDC .text:64405113 190
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Quick introduction to reverse engin
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1.16 C++ classes . . . . . . . . .
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Preface Here (will be) some of my n
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1.1 Hello, world! Let’s start wit
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1.2 Stack Stack — is one of the m
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(_snprintf() function works just li
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1.3 printf() with several arguments
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1.4 scanf() Now let’s use scanf()
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GCC replaced first printf() call to
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}; return 0; printf ("What you ente
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1.5 Passing arguments via stack Now
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1.6 One more word about results ret
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push OFFSET $SG741 ; ’a
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1.8 switch()/case/default 1.8.1 Few
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1.8.2 A lot of cases If switch() st
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loc_804840C: ; DATA XREF: .rodata:0
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et 0 _main ENDP Nothing very specia
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add esp, 1Ch xor eax, eax ; return
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C/C++ standard defines char type as
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eax=eax+ecx return eax ... and this
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mov eax, ecx imul edx sar edx, 1 mo
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; current stack state: ST(0) = resu
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; in local stack here 8 bytes still
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fld QWORD PTR _a$[esp-4] ; current
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In other words, fnstsw ax / sahf in
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1.13 Arrays Array is just a set of
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mov [esp+70h+var_70], eax call _pri
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jge SHORT $LN1@main mov ecx, DWORD
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ebp 0x15 0x15 esi 0x0 0 edi 0x0 0 e
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1.14 Bit fields A lot of functions
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So, let’s download Linux Kernel 2
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There are some redundant code prese
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y 10 just by dropping last digit (3
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_key$ = 8 ; size = 4 _len$ = 12 ; s
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1.15 Structures It can be defined t
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call DWORD PTR __imp__GetSystemTime
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1.15.4 Fields packing in structure
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}; int b; struct outer_struct { cha
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}; printf ("stepping=%d\n", tmp->st
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call ___printf_chk mov eax, esi shr
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mov edx, DWORD PTR _t$[ebp] or edx,
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1.16 C++ classes I placed a C++ cla
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push ecx mov DWORD PTR _this$[ebp],
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call _ZN1c4dumpEv lea eax, [esp+20h
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1.17 Unions 1.17.1 Pseudo-random nu
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xor eax, eax pop esi mov esp, ebp p
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Let’s compile it in MSVC 2010 (I
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comp() function: public comp comp p
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Some compilers can do vectorization
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mov ecx, [esp+10h+var_10] mov edx,
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GCC In all other cases, non-SSE2 co
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add ebx, edx lea esi, [esi+0] loc_8
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movdqa xmm1, XMMWORD PTR [ecx+16] a
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1.20 x86-64 It’s a 64-bit extensi
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} x40 = a3 | x31; x41 = x24 & ~x37;
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or ebx, DWORD PTR _x6$[esp+36] mov
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and r11, r8 and rsi, r8 and r10, r1
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pop rdi pop rsi ret 0 s1 ENDP Nothi
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2.1 LEA instruction LEA (Load Effec
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2.3 npad It’s an assembler macro
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2.4 Signed number representations T
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call function function: .. do somet
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3.2 String Debugging messages are o
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.text:3011E91B DD 1E fstp qword ptr
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loc_80483F2: pop ebp retn _f endp 4
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loc_8048444: loc_8048448: loc_80484
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public f2 f2 proc near push ebp mov
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loc_804840A: loc_804842E: loc_80484
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mov esi, DWORD PTR _k$[esp+16] push
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or eax, edx retn f endp 4.1.8 Task
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4.2 Middle level 4.2.1 Task 2.1 Wel
Page 144 and 145: mov [edx+eax], bl mov ebx, edi mov
Page 146 and 147: loc_80485AB: ; CODE XREF: f+1E0 ; f
Page 148 and 149: mov [ecx+eax], dl inc eax cmp ebx,
Page 150 and 151: Chapter 5 Tools ∙ IDA as disassem
Page 152 and 153: Chapter 7 More examples 147
Page 154 and 155: .text:00541050 arg_0 = dword ptr 4
Page 156 and 157: .text:005410F3 .text:005410F3 loc_5
Page 158 and 159: .text:005411A9 pop ebx .text:005411
Page 160 and 161: .text:00541249 .text:00541249 next_
Page 162 and 163: .text:005412FC mov esi, offset cube
Page 164 and 165: .text:005413DC call _fwrite ; write
Page 166 and 167: .text:005414A7 push ecx ; Filename
Page 168 and 169: .text:005413A3 mov ecx, [esp+44h+pa
Page 170 and 171: .text:00541408 push offset aRb ; "r
Page 172 and 173: }; }; return; fseek (f, 0, SEEK_END
Page 174 and 175: .text:005411B5 mov ebp, eax Check f
Page 176 and 177: .text:0054124C inc ebp .text:005412
Page 178 and 179: This instruction clears bit, in oth
Page 180 and 181: .text:005410CD add esp, 40h .text:0
Page 182 and 183: }; for (i=0; i
Page 184 and 185: }; tmp[y][z]=get_bit (row, y, z); f
Page 186 and 187: }; fread (buf, flen, 1, f); fclose
Page 188 and 189: 7.2 SAP client network traffic comp
Page 190 and 191: .text:64413F68 .text:64413F68 loc_6
Page 192 and 193: .text:64405171 call dbg .text:64405
Page 196 and 197: .text:64405113 loc_64405113: .text:
Page 198 and 199: Now let’s dig deeper and find con
Page 200 and 201: .text:64411E0B .text:64411E0B loc_6
Page 202 and 203: Chapter 8 Other things 8.1 Compiler
Page 204 and 205: Chapter 9 Tasks solutions 9.1 Easy
Page 206 and 207: 9.1.5 Task 1.5 Hint #1: Keep in min
Page 208 and 209: } 9.1.8 Task 1.8 Solution: two 100*
Page 210 and 211: #define PUSH(low, high) ((void) ((t
Page 212 and 213: } } ignore one or both. Otherwise,
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Quick introduction to reverse engineering for beginners

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