Commodore Vic-20 - . , - , BBS, X.25. , . , , - - , , - . - .

-(812) 324-5353, (095) 945-8100

www.symbol.ru

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RAILS

8615859 785932

ISBN 978-5-93286-158-5

, UNIX.

Python 3

Django. - Python

Books.Ru ISBN 9785932861585, : . 2 Books.Ru . , . , (piracy@symbol.ru), .

HACKINGThe Art of Exploitation

Second edition

Jon Erickson

- 2010

High tech

: , 2- .

. . . . . . .

.

: . 2- . . . .: -, 2010. 512 ., .

ISBN 978-5-93286-158-5

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, -, . - . - Ubuntu Linux, - , .

ISBN 978-5-93286-158-5 ISBN 978-1-59327-144-2 ()

-, 2010Authorized translation of the English edition 2008 No Starch Press, Inc. This trans-lation is published and sold by permission of No Starch Press, Inc., the owner of all rights to publish and sell the same.

, - . -, , .

-. 199034, -, 16 , 7,. (812) 380-5007, www.symbol.ru. N 000054 25.12.98.

005-93, 2; 953000 .

30.09.2009. 70100 1/16. . 32 . . 1500 .

199034, -, 9 , 12.

1- ..................................................10

...........................................................................11

........................................................................11

0x100 ...........................................................................12

0x200 ...........................................................17

0x210 ? ...........................................180x220 .......................................................................190x230 ..................................................20

0x231 If-then-else ................................................................200x232 while/until......................................................220x233 for .................................................................22

0x240 ................................230x241 ..............................................................240x242 ........................................250x243 .................................................260x244 ..................................................................28

0x250 ........................................................320x251 ..........................................................330x252 x86 ..........................................................370x253 ........................................................38

0x260 ..................................................510x261 .....................................................................520x262 , , .....560x263 .................................................................580x264 .....................................................620x265 ........................................................660x266 ......................................730x267 ...................................77

0x270 ........................................................850x271 C ..................................................920x272 ...........................................................940x273 malloc() ..........................97

6

0x280 ..........................................................990x281 ........................................................990x282 ............................................ 1040x283 .................................... 1060x284 .............................................................. 1150x285 .............................................. 1190x286 ............................................ 1200x287 ......................................................... 122

0x300 ....................................................................... 135

0x310 ........................................... 1380x320 ..................................................... 139

0x321 ..................................... 1420x330 BASH .................................................... 155

0x331 ........................................ 1650x340 .................................... 173

0x341 ................................... 1730x342 ..... 180

0x350 ......................................................... 1910x351 ................................................. 1920x352 ................................... 1950x353 ................. 1970x354 ................... 1980x355 ..................................... 2050x356 ............................................ 2080x357 .dtors ............................................ 2100x358 notesearch ............... 2150x359 ................. 216

0x400 .................................................. 220

0x410 OSI .................................................................... 2200x420 ......................................................................... 223

0x421 ..................................................... 2240x422 ......................................................... 2260x423 ............................................... 2280x424 - .............................. 2290x425 ........................................... 2290x426 - ................................................. 2330x427 - .......................................... 239

0x430 ...................................................... 2440x431 .................................................. 2440x432 ....................................................... 246

7

0x433 .............................................. 2480x440 () ................................. 252

0x441 .............................. 2540x442 libpcap ...................................................... 2560x443 ............................................ 2580x444 ................................................ 268

0x450 .................................................... 2810x451 SYN- ............................................................... 2820x452 ping .................................................... 2860x453 Teardrop ................................................................. 2870x454 - ......................................................... 2870x455 .................................................. 2880x456 DoS- ........................................ 289

0x460 TCP/IP ............................................................... 2890x461 RST ......................................... 2890x462 ....................................................... 295

0x470 ...................................................... 2950x471 SYN- ...................................... 2960x472 FIN, X-mas Null- ................................ 2960x473 ............................................ 2970x474 ................... 2970x475 (shroud) ......................................... 299

0x480 - ! ......................................... 3050x481 GDB ............................................ 3060x482 ............................... 3080x483 - ................................... 311

0x500 - ( ) ................................................ 315

0x510 C ................................................................ 3150x511 Linux ...................... 318

0x520 - ........................................................... 3210x521 ................... 3210x522 GDB ................................... 3240x523 .......................................... 325

0x530 - ....................................... 3310x531 ............................................... 3350x532 ............................................................. 338

0x540 - ......................................... 3390x541 .......... 3430x542 .............. 345

0x550 - ................................... 351

8

0x600 ............................................................. 357

0x610 ............................................. 3580x620 ......................................................... 358

0x621 ..................................... 3600x622 tinyweb ......................................................... 362

0x630 ..................................... 3670x631 tinywebd ........................... 367

0x640 ...................................................... 3730x641 ...................................................... 373

0x650 ....................................................... 3750x651 .................................................... 3750x652 ................................................... 3800x653 ........................................................... 386

0x660 .......................................... 3880x661 IP- .......................... 3880x662 .................................... 392

0x670 ................................................. 3950x671 .............................. 395

0x680 ...................................................... 4000x681 ................................................... 4000x682 ................................................. 404

0x690 , .................................. 4040x691 - ASCII ................................ 407

0x6a0 .............................................. 4180x6b0 ...................................................... 419

0x6b1 libc (ret2libc) .............................................. 4190x6b2 system() .................................................... 419

0x6c0 (ASLR) ............................ 4210x6c1 BASH GDB ................................. 4230x6c2 linux-gate .................................................. 4270x6c3 ................................................... 4310x6c4 ....................................................... 4310x6c5 ............................................................. 433

0x700 ................................................................... 436

0x710 ....................................................... 4370x711 .............................................. 4370x712 ............................................. 4370x713 ............................... 4380x714 () ................. 439

9

0x720 ..................................................... 4400x721 ........................................ 441

0x730 ............................................. 4420x731 .................. 443

0x740 ........................................... 4440x741 RSA ....................................................................... 4440x742 ........ 449

0x750 ......................................................... 4500x751 (MitM) ............................ 4500x752 SSH ....................................................... 4550x753 ................................................. 458

0x760 ............................................................... 4630x761 ..................................................... 4650x762 ................................... 4670x763 - .......................................... 4690x764 .................................. 470

0x770 802.11b ........ 4810x771 WEP ........................................................ 4810x772 RC4 ................................................ 483

0x780 WEP ............................................................... 4840x781 ........................................................ 4840x782 ................ 4850x783 IV .................................. 4860x784 IP .................................................... 4870x785 -- (FMS) ..................... 488

0x800 ..................................................................... 499

0x810 ......................................................................... 5000x820 .................................................................... 502

......................................................... 503

1-

. - - , , .

PHRACK

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SECURITY FORUMS

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UNIX REVIEW

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IEEE CIPHER

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COMPUTER POWER USER (CPU) MAGAZINE

. , , - .

ABOUT.COM INTERNET/NETWORK SECURITY

. , . , , - . : , . Ubuntu Linux, x86, . , 1.

(Bill Pollock) No Starch Press , . , (Seth Benson) (Aaron Adams) , (Jack Matheson) , - (Dr. Seidel) , Commodore VIC-20 , , .

1 - www.symbol.ru/library/hacking-2ed. . .

0x100

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14 0x100

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- , - . 2001 (Edward Felten) - , - . , SDMI (Secure Digital Music Initiative), - . - - SDMI

0x100 15

(RIAA). (Digital Millennium Copyright Act, DMCA) 1998 - , - . , - , - . , - Adobe, . - , -. - : , . , ? - , , , , ? , - .

, , , , - . - , ; . - , , . , . , -.

- -, , -, . - , , , . - (Intrusion Detection Systems, IDS) - . - IDS, - IDS, IDS. : - , , - , .

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16 0x100

, , . - (www.symbol.ru/library/hacking-2ed) Linux. - , - . - x86, - Microsoft Windows Macintosh. Linux . - , - . , , .

0x200

, , , . , . , , . , . ., , , - - . - - , , - . -, , , - , , . , , , - . , .

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18 0x200

, . , .

- , , Commodore 64 , ; , - , - ; , - . , , - - . , -, - .

0x210 ? . , . , . , - , . - :

. . - , 15- , , 16- . 16- . 16- , . 5 , . : , 743.

, , - . , , -, , .

, . - , - . , . - . - , , Intel x86, , , - , - . - , .

0x220 19

- . - , - , . , , , . - - . -, . , Intel x86 - Sparc, - x86 Sparc. -, -, . x86, - Sparc . , - , - .

, - , . - . - . -, , . C, C++ FORTRAN. - , , - , .

0x220 , - . , . , - - , - . . - -. , , - , C. -.

20 0x200

0x230 , . - , , - , . , - - . -: - .

0x231 If-then-else

- . . - . if-then-else (--). :

If () then{ , ;}Else{ , ;}

, C, - , . - , - :

;If ( ){ 15- ; ; 16- ;}Else{ 16- ;}

, , , - .

0x230 21

C then , .

, , then, - BASIC, Fortran Pascal. , . - .

C, , , , .

C , , . - , . :

;If ( ){ 15- ; ; 16- ;}Else

16- ;

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If ( ) , , ;Else{ ; ;}

. if-then-else, - select/case, : , , ( if-then).

22 0x200

0x232 while/until

while (), . - . , , , , - . while , - , . :

while (){ - ; , ;}

, while, - , . -. , while, , .

until ( ), , - Perl ( C -). until while, . until :

until (){ - ; , ;}

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while ( ) ;

0x233 for

for. , - , . - for 5 :

for (5 ) 1 ;

0x240 23

for while . - :

0;while ( 5){ 1 ; 1;}

for C :

for (i=0; i

24 0x200

0x241

, for, . , , , . - , , -. , -, . , C ( ), , - , . , C -. - , - , . - -, . - , .

C , , . : int ( ), float ( 1) char ( ). - , , :

int a, b;float k;char z;

a b , k ( 3,14), z - , A w. - - =.

int a = 13, b;float k;char z = A;

k = 3.14;z = w;b = a + 5;

- : a 13, k 3,14, z w, b - 18, 13 + 5 = 18.

1 , - . . .

0x240 25

; C -.

0x242

b = a + 7 -. , C .

. (- ) , . a 13, 13 5, - 2 3 , , a % 5 = 3. , - a b , b = a / 5 b - 2, . - 2,6, .

+ b = a + 5

- b = a - 5

* b = a * 5

/ b = a / 5

% b = a % 5

, . C - . , - , .

i = i + 1 i++ ++i 1

i = i 1 i-- --i 1

- . - i++ ++i. , - i 1 , - , i 1 - . .

26 0x200

int a, b;a = 5;b = a++ * 6;

b - 30, 6, b = a++ * 6; :

b = a * 6;a = a + 1;

b = ++a * 6; a , :

a = a + 1;b = a * 6;

, b 36, a - 6.

. , - , - 12, (, i = i + 12). .

i = i + 12 i+=12

i = i - 12 i-=12

i = i * 12 i*=12

i = i / 12 i/=12

0x243

. . C - , -.

< (a < b)

> (a > b)

0x240 27

= b)

== (a == b)

!= (a != b)

, , . -: , - . a = 7 7 a, a == 7 - , a 7. ( -, Pascal, , - :=.) , - . - .

!(a < b) (a >= b)

- .

|| ((a < b) || (a < c))

&& ((a < b) && !(a < c))

, , - , , a b a c. , , , , a b a c. - .

, - . , () -, /. -, 1 , 0 .

while ( == 1){ - ; , ;}

28 0x200

, . C , , . 1, -, 0 . 1 1, 1, 0, 0. , - .

while (){ - ; , ;}

, , - .

while (() && !(_)){ - ; If(!( - __)) , ;}

, - , 1 0 - . , , .

0x244

, - . , (function). - , (subroutine), (procedure). , -, : - , , - , . , - , , ( - ). - , . -, .

Function (_){ _;

0x240 29

; , ; while( ) { ; ; } _; while( ) { if( < 5 ) ; } ; _; }

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, ; , - . , .

C -. , , , - . , - , .

C function, - , . . - ( , - x), :

int factorial(int x){ int i; for(i=1; i < x; i++) x *= i; return x;}

, - 1 x , - . return - x . - -

30 0x200

, .

int a=5, b;b = factorial(a);

b 120, factorial - 5 120.

, C , - . , , - . , - . - - , - , . factorial():

int factorial(int);

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, , , () , void. () -, . . -, : - , . , , . C- .

void (_, __){ ; __ = ; while(__ != __) { ; __ = ; } _; ; , ; while( )

0x240 31

{ ; ; } _; while( ) { if( < 5 ) ; } ; _ }

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;while ( ) ;if ( ){ (, 15- ); (, ); (, 16- );}else (, 16- ); (, );for (i=0; i

32 0x200

0x250 , C - , - C. C , Linux x86. Linux - , , - x86 . , , - C.

, , x861. - . - Linux, . Linux- - . , - .

. firstprog.c C-, 10 Hello, world!.

firstprog.c#include

int main(){ int i; for(i=0; i < 10; i++) // 10 . { printf(Hello, world!\n); // . } return 0; // , .}

C- , main(). (//) , .

, - C, / (I/O),

1 www.symbol.ru/library/hacking-2ed. . .

0x250 33

stdio. - . /usr/include/stdio.h, , - /. - main() printf() /, printf(). - stdio.h. C . , - , . , . -, , - GCC .

GNU Compiler Collection (GCC) C, - C , . - , - a.out. , ?

reader@hacking:~/booksrc $ gcc firstprog.creader@hacking:~/booksrc $ ls -l a.out-rwxr-xr-x 1 reader reader 6621 2007-09-06 22:16 a.outreader@hacking:~/booksrc $ ./a.outHello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!Hello, world!reader@hacking:~/booksrc $

0x251

, -. , C. : - C , -, . , , - . , , . , , C . , . -

34 0x200

C , . a.out , - (). , - C -. - x86. Sparc (- Sun) PowerPC ( - ). , - , C .

, , - , . , - . , - , . - x86. - ? GNU objdump, - . , - , main().

reader@hacking:~/booksrc $ objdump -D a.out | grep -A20 main.:08048374 : 8048374: 55 push %ebp 8048375: 89 e5 mov %esp,%ebp 8048377: 83 ec 08 sub $0x8,%esp 804837a: 83 e4 f0 and $0xfffffff0,%esp 804837d: b8 00 00 00 00 mov $0x0,%eax 8048382: 29 c4 sub %eax,%esp 8048384: c7 45 fc 00 00 00 00 movl $0x0,0xfffffffc(%ebp) 804838b: 83 7d fc 09 cmpl $0x9,0xfffffffc(%ebp) 804838f: 7e 02 jle 8048393 8048391: eb 13 jmp 80483a6 8048393: c7 04 24 84 84 04 08 movl $0x8048484,(%esp) 804839a: e8 01 ff ff ff call 80482a0 804839f: 8d 45 fc lea 0xfffffffc(%ebp),%eax 80483a2: ff 00 incl (%eax) 80483a4: eb e5 jmp 804838b 80483a6: c9 leave 80483a7: c3 ret 80483a8: 90 nop 80483a9: 90 nop 80483aa: 90 nopreader@hacking:~/booksrc $

objdump , ,

0x250 35

grep , 20 - main.:. - , 16. - , 10 . 0 9 0 9, 10 15 A F. , 8 , - 1 () 0 (). 256 (28) - .

( 0x8048374) -. - , - . - ; .

, , , . , - , -, . Intel x86 32- , 64-. 32- - 232 ( 4 294 967 296) , 64- 264

(1,84467441 1019) . 64- , 32-, - 32- .

- x86. , , , - . - 0101010110001001111001011000001111101100111100001 . . . , , - , - , -.

, , . -, . . ret , 0xc3 11000011. C - , . , - , . , .

36 0x200

. x86, AT&T Intel. AT&T, Linux . AT&T - % $, (- ). - Intel, objdump -M intel .

reader@hacking:~/booksrc $ objdump -M intel -D a.out | grep -A20 main.:08048374 : 8048374: 55 push ebp 8048375: 89 e5 mov ebp,esp 8048377: 83 ec 08 sub esp,0x8 804837a: 83 e4 f0 and esp,0xfffffff0 804837d: b8 00 00 00 00 mov eax,0x0 8048382: 29 c4 sub esp,eax 8048384: c7 45 fc 00 00 00 00 mov DWORD PTR [ebp-4],0x0 804838b: 83 7d fc 09 cmp DWORD PTR [ebp-4],0x9 804838f: 7e 02 jle 8048393 8048391: eb 13 jmp 80483a6 8048393: c7 04 24 84 84 04 08 mov DWORD PTR [esp],0x8048484 804839a: e8 01 ff ff ff call 80482a0 804839f: 8d 45 fc lea eax,[ebp-4] 80483a2: ff 00 inc DWORD PTR [eax] 80483a4: eb e5 jmp 804838b 80483a6: c9 leave 80483a7: c3 ret 80483a8: 90 nop 80483a9: 90 nop 80483aa: 90 nopreader@hacking:~/booksrc $

Intel , . -, , . , - / . - , - , - - . , , . , - , - .

, - .

0x250 37

, - .

...

0x252 x86

x86 , . - , , -. GNU GDB. - , - .

, - , XVII , . , , , . , - .

, GDB .

reader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) break mainBreakpoint 1 at 0x804837a(gdb) runStarting program: /home/reader/booksrc/a.out

Breakpoint 1, 0x0804837a in main ()(gdb) info registerseax 0xbffff894 -1073743724ecx 0x48e0fe81 1222704769edx 0x1 1ebx 0xb7fd6ff4 -1208127500esp 0xbffff800 0xbffff800ebp 0xbffff808 0xbffff808esi 0xb8000ce0 -1207956256edi 0x0 0eip 0x804837a 0x804837a eflags 0x286 [ PF SF IF ]cs 0x73 115ss 0x7b 123ds 0x7b 123es 0x7b 123fs 0x0 0gs 0x33 51

38 0x200

(gdb) quitThe program is running. Exit anyway? (y or n) yreader@hacking:~/booksrc $

main() (breakpoint), . GDB , - - .

(EAX, ECX, EDX EBX) - . (Accumulator), (Counter), (Data) - (Base). , - .

(ESP, EBP, ESI EDI) - , - . (Stack Pointer), (Base Pointer), - (Source Index) (Destination Index). , 32-- , . -, . , - , . , , .

EIP (Instruction Pointer); . - , , , EIP . , . - 0x804838a.

EFLAGS , . , , . , - .

0x253

Intel, . GDB - Intel set disassembly

0x250 39

intel, set dis intel. - GDB, .gdbinit, - .

reader@hacking:~/booksrc $ gdb -q(gdb) set dis intel(gdb) quitreader@hacking:~/booksrc $ echo set dis intel > ~/.gdbinitreader@hacking:~/booksrc $ cat ~/.gdbinitset dis intelreader@hacking:~/booksrc $

GDB Intel, - . Intel :

,

, - . - : mov (move) , sub (subtract), inc (increment) . , ESP EBP, 8 ESP ( ESP).

8048375: 89 e5 mov ebp,esp8048377: 83 ec 08 sub esp,0x8

, . cmp , -, j ( jump ), ( ). - 4- (DWORD), EBP, 4, 9. jle ( jump if less than or equal to , ) . 4- - 9, - 0x8048393. jmp ( ). 4- 9, - 0x80483a6.

804838b: 83 7d fc 09 cmp DWORD PTR [ebp-4],0x9804838f: 7e 02 jle 8048393 8048391: eb 13 jmp 80483a6

-, Intel, - , .

40 0x200

GCC -g, - , - GDB .

reader@hacking:~/booksrc $ gcc -g firstprog.creader@hacking:~/booksrc $ ls -l a.out-rwxr-xr-x 1 matrix users 11977 Jul 4 17:29 a.outreader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/libthread_db.so.1.(gdb) list1 #include 23 int main()4 {5 int i;6 for(i=0; i < 10; i++)7 {8 printf(Hello, world!\n);9 }10 }(gdb) disassemble mainDump of assembler code for function main():0x08048384 : push ebp0x08048385 : mov ebp,esp0x08048387 : sub esp,0x80x0804838a : and esp,0xfffffff00x0804838d : mov eax,0x00x08048392 : sub esp,eax0x08048394 : mov DWORD PTR [ebp-4],0x00x0804839b : cmp DWORD PTR [ebp-4],0x90x0804839f : jle 0x80483a3 0x080483a1 : jmp 0x80483b6 0x080483a3 : mov DWORD PTR [esp],0x80484d40x080483aa : call 0x80482a8 0x080483af : lea eax,[ebp-4]0x080483b2 : inc DWORD PTR [eax]0x080483b4 : jmp 0x804839b 0x080483b6 : leave0x080483b7 : retEnd of assembler dump.(gdb) break mainBreakpoint 1 at 0x8048394: file firstprog.c, line 6.(gdb) runStarting program: /hacking/a.out

Breakpoint 1, main() at firstprog.c:66 for(i=0; i < 10; i++)(gdb) info register eipeip 0x8048394 0x8048394(gdb)

0x250 41

main(). main() . , - , . - main(), main(). EIP ( ).

: EIP , - main() (- ). ( ) . , main(). , C -, , . , -, , . , - GDB .

GDB - x ( examine). - . - : , , . , , , . - . - , GDB, - , , - , . - , - , - .

x - . : . , , - . -:

o (octal).

x (hexadecimal).

u (unsigned decimal).

t (binary).

42 0x200

examine - . EIP. GDB -, info register eip i r eip.

(gdb) i r eipeip 0x8048384 0x8048384 (gdb) x/o 0x80483840x8048384 : 077042707(gdb) x/x $eip0x8048384 : 0x00fc45c7(gdb) x/u $eip0x8048384 : 16532935(gdb) x/t $eip0x8048384 : 00000000111111000100010111000111(gdb)

, EIP, , - , EIP. - , $eip -, EIP . - 077042707 0x00fc45c7, 16532935 00000000111111000100010111000111. exam-ine , - .

(gdb) x/2x $eip0x8048384 : 0x00fc45c7 0x83000000(gdb) x/12x $eip0x8048384 : 0x00fc45c7 0x83000000 0x7e09fc7d 0xc713eb020x8048394 : 0x84842404 0x01e80804 0x8dffffff 0x00fffc450x80483a4 : 0xc3c9e5eb 0x90909090 0x90909090 0x5de58955(gdb)

, - . , , . :

b 1 (byte)

h (halfword), 2

w (word), 4

g (giant), 8

, . , DWORD, . - DWORD . (short) . -

0x250 43

, GDB - .

(gdb) x/8xb $eip0x8048384 : 0xc7 0x45 0xfc 0x00 0x00 0x00 0x00 0x83(gdb) x/8xh $eip0x8048384 : 0x45c7 0x00fc 0x0000 0x8300 0xfc7d 0x7e09 0xeb02 0xc713(gdb) x/8xw $eip0x8048384 : 0x00fc45c7 0x83000000 0x7e09fc7d 0xc713eb020x8048394 : 0x84842404 0x01e80804 0x8dffffff 0x00fffc45(gdb)

. examine 8 , , examine, , - . examine -, 0xc7 0x45, -, , 0x45c7 - . - , 0x00fc45c7, - 0xc7, 0x45, 0xfc 0x00.

, x86 - (little-endian byte order), - . , - , -. GDB , , - - . -, .

(gdb) x/4xb $eip0x8048384 : 0xc7 0x45 0xfc 0x00(gdb) x/4ub $eip0x8048384 : 199 69 252 0(gdb) x/1xw $eip0x8048384 : 0x00fc45c7(gdb) x/1uw $eip0x8048384 : 16532935(gdb) quitThe program is running. Exit anyway? (y or n) yreader@hacking:~/booksrc $ bc -ql199*(256^3) + 69*(256^2) + 252*(256^1) + 0*(256^0)33432524800*(256^3) + 252*(256^2) + 69*(256^1) + 199*(256^0)16532935

44 0x200

quitreader@hacking:~/booksrc $

, . bc , , 3343252480. - , . - , .

examine - GDB . , GDB , . examine i ( instruction), .

reader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) break main

Breakpoint 1 at 0x8048384: file firstprog.c, line 6.(gdb) runStarting program: /home/reader/booksrc/a.out

Breakpoint 1, main () at firstprog.c:66 for(i=0; i < 10; i++)(gdb) i r $eipeip 0x8048384 0x8048384 (gdb) x/i $eip0x8048384 : mov DWORD PTR [ebp-4],0x0(gdb) x/3i $eip0x8048384 : mov DWORD PTR [ebp-4],0x00x804838b : cmp DWORD PTR [ebp-4],0x90x804838f : jle 0x8048393 (gdb) x/7xb $eip0x8048384 : 0xc7 0x45 0xfc 0x00 0x00 0x00(gdb) x/i $eip0x8048384 : mov DWORD PTR [ebp-4],0x0(gdb)

GDB a.out main(). EIP , , .

objdump , , EIP, - .

8048384: c7 45 fc 00 00 00 00 mov DWORD PTR [ebp-4],0x0

0x250 45

0 , 4 , EBP. , i C; i - , 4 x86. -, i for. - , - . .

(gdb) i r ebpebp 0xbffff808 0xbffff808(gdb) x/4xb $ebp - 40xbffff804: 0xc0 0x83 0x04 0x08(gdb) x/4xb 0xbffff8040xbffff804: 0xc0 0x83 0x04 0x08(gdb) print $ebp - 4$1 = (void *) 0xbffff804(gdb) x/4xb $10xbffff804: 0xc0 0x83 0x04 0x08(gdb) x/xw $10xbffff804: 0x080483c0(gdb)

, EBP 0xbffff808, - , - 4 , 0xbffff804. - examine , . print, - . $1, - -. : - 4 , - .

nexti ( next instruction). , - EIP, EIP .

(gdb) nexti0x0804838b 6 for(i=0; i < 10; i++)(gdb) x/4xb $10xbffff804: 0x00 0x00 0x00 0x00(gdb) x/dw $10xbffff804: 0(gdb) i r eipeip 0x804838b 0x804838b (gdb) x/i $eip0x804838b : cmp DWORD PTR [ebp-4],0x9(gdb)

46 0x200

, 4 EBP 4, , - i. EIP . .

(gdb) x/10i $eip0x804838b : cmp DWORD PTR [ebp-4],0x90x804838f : jle 0x8048393 0x8048391 : jmp 0x80483a6 0x8048393 : mov DWORD PTR [esp],0x80484840x804839a : call 0x80482a0 0x804839f : lea eax,[ebp-4]0x80483a2 : inc DWORD PTR [eax]0x80483a4 : jmp 0x804838b 0x80483a6 : leave0x80483a7 : ret(gdb)

cmp ( compare) , , i C, - 9. jle - . - ( EFLAGS), , EIP - . , 0x8048393, i - 9. , EIP -, . EIP 0x80483a6. if-then-else: i 9, - 0x8048393; - 0x80483a6. 0x8048393 ( ) , , 0x80483a6 ( ) .

, , 9, 0, , 0 9, - EIP 0x8048393.

(gdb) nexti0x0804838f 6 for(i=0; i < 10; i++)(gdb) x/i $eip0x804838f : jle 0x8048393 (gdb) nexti8 printf(Hello, world!\n);(gdb) i r eipeip 0x8048393 0x8048393 (gdb) x/2i $eip0x8048393 : mov DWORD PTR [esp],0x80484840x804839a : call 0x80482a0 (gdb)

0x250 47

, 0x8048393, -. mov, 0x8048484 -, ESP. - ESP?

(gdb) i r espesp 0xbffff800 0xbffff800(gdb)

ESP 0xbffff800, mov 0x8048484. ? 0x8048484? -.

(gdb) x/2xw 0x80484840x8048484: 0x6c6c6548 0x6f57206f(gdb) x/6xb 0x80484840x8048484: 0x48 0x65 0x6c 0x6c 0x6f 0x20(gdb) x/6ub 0x80484840x8048484: 72 101 108 108 111 32(gdb)

- , . , - . , ASCII. ASCII , - ( ), . 0x48, 0x65, 0x6c 0x6f ASCII, - . ASCII man ascii, UNIX.

ASCII Table Oct Dec Hex Char Oct Dec Hex Char ----------------------------------------------------------- 000 0 00 NUL \0 100 64 40 @ 001 1 01 SOH 101 65 41 A 002 2 02 STX 102 66 42 B 003 3 03 ETX 103 67 43 C 004 4 04 EOT 104 68 44 D 005 5 05 ENQ 105 69 45 E 006 6 06 ACK 106 70 46 F 007 7 07 BEL \a 107 71 47 G 010 8 08 BS \b 110 72 48 H 011 9 09 HT \t 111 73 49 I 012 10 0A LF \n 112 74 4A J 013 11 0B VT \v 113 75 4B K 014 12 0C FF \f 114 76 4C L 015 13 0D CR \r 115 77 4D M

48 0x200

016 14 0E SO 116 78 4E N 017 15 0F SI 117 79 4F O 020 16 10 DLE 120 80 50 P 021 17 11 DC1 121 81 51 Q 022 18 12 DC2 122 82 52 R 023 19 13 DC3 123 83 53 S 024 20 14 DC4 124 84 54 T 025 21 15 NAK 125 85 55 U 026 22 16 SYN 126 86 56 V 027 23 17 ETB 127 87 57 W 030 24 18 CAN 130 88 58 X 031 25 19 EM 131 89 59 Y 032 26 1A SUB 132 90 5A Z 033 27 1B ESC 133 91 5B [ 034 28 1C FS 134 92 5C \ \\ 035 29 1D GS 135 93 5D ] 036 30 1E RS 136 94 5E ^ 037 31 1F US 137 95 5F _ 040 32 20 SPACE 140 96 60 ` 041 33 21 ! 141 97 61 a 042 34 22 142 98 62 b 043 35 23 # 143 99 63 c 044 36 24 $ 144 100 64 d 045 37 25 % 145 101 65 e 046 38 26 & 146 102 66 f 047 39 27 147 103 67 g 050 40 28 ( 150 104 68 h 051 41 29 ) 151 105 69 i 052 42 2A * 152 106 6A j 053 43 2B + 153 107 6B k 054 44 2C , 154 108 6C l 055 45 2D - 155 109 6D m 056 46 2E . 156 110 6E n 057 47 2F / 157 111 6F o 060 48 30 0 160 112 70 p 061 49 31 1 161 113 71 q 062 50 32 2 162 114 72 r 063 51 33 3 163 115 73 s 064 52 34 4 164 116 74 t 065 53 35 5 165 117 75 u 066 54 36 6 166 118 76 v 067 55 37 7 167 119 77 w 070 56 38 8 170 120 78 x 071 57 39 9 171 121 79 y 072 58 3A : 172 122 7A z 073 59 3B ; 173 123 7B { 074 60 3C < 174 124 7C | 075 61 3D = 175 125 7D } 076 62 3E > 176 126 7E ~ 077 63 3F ? 177 127 7F DEL

0x250 49

, GDB examine - . c - ASCII, s .

(gdb) x/6cb 0x80484840x8048484: 72 H 101 e 108 l 108 l 111 o 32 (gdb) x/s 0x80484840x8048484: Hello, world!\n(gdb)

, 0x8048484 Hello, world!\n. - printf(), , (0x8048484) , ESP, - -. , ESP.

(gdb) x/2i $eip0x8048393 : mov DWORD PTR [esp],0x80484840x804839a : call 0x80482a0 (gdb) x/xw $esp0xbffff800: 0xb8000ce0(gdb) nexti0x0804839a 8 printf(Hello, world!\n);(gdb) x/xw $esp0xbffff800: 0x08048484(gdb)

printf(), - . , -.

(gdb) x/i $eip0x804839a : call 0x80482a0 (gdb) nextiHello, world!6 for(i=0; i < 10; i++)(gdb)

GDB, -. .

(gdb) x/2i $eip0x804839f : lea eax,[ebp-4]0x80483a2 : inc DWORD PTR [eax](gdb)

, i 1. lea ( Load Effective Address -) EBP 4 EAX. .

50 0x200

(gdb) x/i $eip0x804839f : lea eax,[ebp-4](gdb) print $ebp - 4$2 = (void *) 0xbffff804(gdb) x/x $20xbffff804: 0x00000000(gdb) i r eaxeax 0xd 13(gdb) nexti0x080483a2 6 for(i=0; i < 10; i++)(gdb) i r eaxeax 0xbffff804 -1073743868(gdb) x/xw $eax0xbffff804: 0x00000000(gdb) x/dw $eax0xbffff804: 0(gdb)

inc 1 , - ( EAX). - .

(gdb) x/i $eip0x80483a2 : inc DWORD PTR [eax](gdb) x/dw $eax0xbffff804: 0(gdb) nexti0x080483a4 6 for(i=0; i < 10; i++)(gdb) x/dw $eax0xbffff804: 1(gdb)

, EBP 4 (0xbffff804), 1. C, for i.

.

(gdb) x/i $eip0x80483a4 : jmp 0x804838b (gdb)

- 0x804838b. - EIP.

, , , - C .

(gdb) disass mainDump of assembler code for function main:0x08048374 : push ebp0x08048375 : mov ebp,esp0x08048377 : sub esp,0x8

0x260 51

0x0804837a : and esp,0xfffffff00x0804837d : mov eax,0x00x08048382 : sub esp,eax0x08048384 : mov DWORD PTR [ebp-4],0x00x0804838b : cmp DWORD PTR [ebp-4],0x90x0804838f : jle 0x8048393 0x08048391 : jmp 0x80483a6 0x08048393 : mov DWORD PTR [esp],0x80484840x0804839a : call 0x80482a0 0x0804839f : lea eax,[ebp-4]0x080483a2 : inc DWORD PTR [eax]0x080483a4 : jmp 0x804838b 0x080483a6 : leave0x080483a7 : retEnd of assembler dump.(gdb) list1 #include 23 int main()4 {5 int i;6 for(i=0; i < 10; i++)7 {8 printf(Hello, world!\n);9 }10 }(gdb)

, , for, , - printf(). - , - printf() , 10. jle , - -, .

0x260 , , C. - , - . - , - . , , C - , - .

52 0x200

0x261

Hello, world!\n, printf() - , , . C n . - 20 20 , . . char_array.c .

char_array.c#include

int main(){ char str_a[20]; str_a[0] = H; str_a[1] = e; str_a[2] = l; str_a[3] = l; str_a[4] = o; str_a[5] = ,; str_a[6] = ; str_a[7] = w; str_a[8] = o; str_a[9] = r; str_a[10] = l; str_a[11] = d; str_a[12] = !; str_a[13] = \n; str_a[14] = 0; printf(str_a);}

GCC -o, - , . , char_array.

reader@hacking:~/booksrc $ gcc -o char_array char_array.creader@hacking:~/booksrc $ ./char_arrayHello, world!reader@hacking:~/booksrc $

str_a 20 , . : 0, 1. , 0 (null, ).

, 20 , 12. - , , -

0x260 53

, . . , printf() - Hello.

, - , . , strcpy() - , - - ( ). - , Intel: , - .

char_array.c strcpy(), - . char_array string.h, - .

char_array2.c#include #include

int main() { char str_a[20]; strcpy(str_a, Hello, world!\n); printf(str_a);}

GDB. - , - strcpy(), , . , - . strcpy() , .

reader@hacking:~/booksrc $ gcc -g -o char_array2 char_array2.creader@hacking:~/booksrc $ gdb -q ./char_array2Using host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) list1 #include 2 #include 34 int main() {5 char str_a[20];67 strcpy(str_a, Hello, world!\n);

54 0x200

8 printf(str_a);9 }(gdb) break 6Breakpoint 1 at 0x80483c4: file char_array2.c, line 6.(gdb) break strcpyFunction strcpy not defined.Make breakpoint pending on future shared library load? (y or [n]) yBreakpoint 2 (strcpy) pending.(gdb) break 8Breakpoint 3 at 0x80483d7: file char_array2.c, line 8.(gdb)

strcpy(). EIP , . : , EIP, , .

(gdb) runStarting program: /home/reader/booksrc/char_array2Breakpoint 4 at 0xb7f076f4Pending breakpoint strcpy resolved

Breakpoint 1, main () at char_array2.c:77 strcpy(str_a, Hello, world!\n);(gdb) i r eipeip 0x80483c4 0x80483c4 (gdb) x/5i $eip0x80483c4 : mov DWORD PTR [esp+4],0x80484c40x80483cc : lea eax,[ebp-40]0x80483cf : mov DWORD PTR [esp],eax0x80483d2 : call 0x80482c4 0x80483d7 : lea eax,[ebp-40](gdb) continueContinuing.

Breakpoint 4, 0xb7f076f4 in strcpy () from /lib/tls/i686/cmov/libc.so.6(gdb) i r eipeip 0xb7f076f4 0xb7f076f4 (gdb) x/5i $eip0xb7f076f4 : mov esi,DWORD PTR [ebp+8]0xb7f076f7 : mov eax,DWORD PTR [ebp+12]0xb7f076fa : mov ecx,esi0xb7f076fc : sub ecx,eax0xb7f076fe : mov edx,eax(gdb) continueContinuing.

Breakpoint 3, main () at char_array2.c:88 printf(str_a);(gdb) i r eipeip 0x80483d7 0x80483d7 (gdb) x/5i $eip

0x260 55

0x80483d7 : lea eax,[ebp-40]0x80483da : mov DWORD PTR [esp],eax0x80483dd : call 0x80482d4 0x80483e2 : leave0x80483e3 : ret(gdb)

, EIP , , strcpy() -. EIP strcpy(), EIP - main(). , EIP strcpy() . , . EIP - . GDB bt ( backtrace), - , . - .

(gdb) runThe program being debugged has been started already.Start it from the beginning? (y or n) yStarting program: /home/reader/booksrc/char_array2Error in re-setting breakpoint 4:Function strcpy not defined.

Breakpoint 1, main () at char_array2.c:77 strcpy(str_a, Hello, world!\n);(gdb) bt#0 main () at char_array2.c:7(gdb) contContinuing.

Breakpoint 4, 0xb7f076f4 in strcpy () from /lib/tls/i686/cmov/libc.so.6(gdb) bt#0 0xb7f076f4 in strcpy () from /lib/tls/i686/cmov/libc.so.6#1 0x080483d7 in main () at char_array2.c:7(gdb) contContinuing.

Breakpoint 3, main () at char_array2.c:88 printf(str_a);(gdb) bt#0 main () at char_array2.c:8(gdb)

- strcpy(). , strcpy() . , Linux - 2.6.11. .

56 0x200

0x262 , ,

C , , . , . , , . 32- 0 ( ) 4 294 967 295 ( ). 32- - 32 , , 232 . 32- - 2 147 483 648 2 147 483 647. , - , , : - . , , - (twos complement). - : , 0. - , , 1. , - - .

pcalc - , -, . - 8- .

reader@hacking:~/booksrc $ pcalc 0y01001001 73 0x49 0y1001001reader@hacking:~/booksrc $ pcalc 0y10110110 + 1 183 0xb7 0y10110111reader@hacking:~/booksrc $ pcalc 0y01001001 + 0y10110111 256 0x100 0y100000000reader@hacking:~/booksrc $

, 01001001 - 73. 1, 73 (10110111). -, 0 8 . pcalc - 256, , 8-- . -, , . , - .

0x260 57

C - unsigned, -. unsigned int.

, , , - long short. , - . C sizeof(), - . , - - , . - datatype_sizes.c sizeof().

datatype_sizes.c#include

int main() { printf(The int data type is\t\t %d bytes\n, sizeof(int)); printf(The unsigned int data type is\t %d bytes\n, sizeof(unsigned int)); printf(The short int data type is\t %d bytes\n, sizeof(short int)); printf(The long int data type is\t %d bytes\n, sizeof(long int)); printf(The long long int data type is %d bytes\n, sizeof(long long int)); printf(The float data type is\t %d bytes\n, sizeof(float)); printf(The char data type is\t\t %d bytes\n, sizeof(char));}

printf() -, . , - , sizeof(). , - .

reader@hacking:~/booksrc $ gcc datatype_sizes.creader@hacking:~/booksrc $ ./a.outThe int data type is 4 bytesThe unsigned int data type is 4 bytesThe short int data type is 2 bytesThe long int data type is 4 bytesThe long long int data type is 8 bytesThe float data type is 4 bytesThe char data type is 1 bytesreader@hacking:~/booksrc $

, x86 - 4 . - 4 , 1 . -

58 0x200

long short 1 -, .

0x263

EIP , - . C. , - . , - , . , - - . . , .

C , . x86 32- -, 32 (4 ). (*), -. - , . pointer.c char, 1 .

pointer.c#include #include

int main() { char str_a[20]; // 20 char *pointer; // char *pointer2; //

strcpy(str_a, Hello, world!\n); pointer = str_a; // . printf(pointer);

pointer2 = pointer + 2; // 2 . printf(pointer2); // . strcpy(pointer2, y you guys!\n); // . printf(pointer); // .}

, . -

1 . double (8 ) long double (16 , 80 ). . .

0x260 59

. printf() strcpy() . - 2, - .

reader@hacking:~/booksrc $ gcc -o pointer pointer.creader@hacking:~/booksrc $ ./pointerHello, world!llo, world!Hey you guys!reader@hacking:~/booksrc $

GDB. -, 10- . - , Hello, world!\n str_a - .

reader@hacking:~/booksrc $ gcc -g -o pointer pointer.creader@hacking:~/booksrc $ gdb -q ./pointerUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) list1 #include 2 #include 34 int main() {5 char str_a[20]; // 20 6 char *pointer; // 7 char *pointer2; // 89 strcpy(str_a, Hello, world!\n);10 pointer = str_a; // .11 printf(pointer);1213 pointer2 = pointer + 2; // 2 .14 printf(pointer2); // .15 strcpy(pointer2, y you guys!\n); // .16 printf(pointer); // .17 }(gdb) break 11Breakpoint 1 at 0x80483dd: file pointer.c, line 11.(gdb) runStarting program: /home/reader/booksrc/pointer

Breakpoint 1, main () at pointer.c:1111 printf(pointer);(gdb) x/xw pointer0xbffff7e0: 0x6c6c6548(gdb) x/s pointer0xbffff7e0: Hello, world!\n(gdb)

60 0x200

, , -, 0xbffff7e0. , - , 0xbffff7e0.

, -, . , . (&), - . -, . GDB, C.

(gdb) x/xw &pointer0xbffff7dc: 0xbffff7e0(gdb) print &pointer$1 = (char **) 0xbffff7dc(gdb) print pointer$2 = 0xbffff7e0 Hello, world!\n(gdb)

, pointer 0xbffff7dc 0xbffff7e0.

, . addressof.c -, . - .

addressof.c#include

int main() { int int_var = 5; int *int_ptr;

int_ptr = &int_var; // int_var int_ptr}

, , , .

reader@hacking:~/booksrc $ gcc -g addressof.creader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) list1 #include 23 int main() {4 int int_var = 5;5 int *int_ptr;67 int_ptr = &int_var; // int_var int_ptr8 }

0x260 61

(gdb) break 8Breakpoint 1 at 0x8048361: file addressof.c, line 8.(gdb) runStarting program: /home/reader/booksrc/a.outBreakpoint 1, main () at addressof.c:88 }(gdb) print int_var$1 = 5(gdb) print &int_var$2 = (int *) 0xbffff804(gdb) print int_ptr$3 = (int *) 0xbffff804(gdb) print &int_ptr$4 = (int **) 0xbffff800(gdb)

, - . -. print int_var, - , . print , int_ptr int_var, - int_ptr.

, - (dereference). -, , , . , . GDB, C. GDB , int_ptr.

(gdb) print *int_ptr$5 = 5

addressof2.c, . printf() - , . .

addressof2.c#include

int main() { int int_var = 5; int *int_ptr; int_ptr = &int_var; // int_var int_ptr.

printf(int_ptr = 0x%08x\n, int_ptr); printf(&int_ptr = 0x%08x\n, &int_ptr); printf(*int_ptr = 0x%08x\n\n, *int_ptr); printf(int_var is located at 0x%08x and contains %d\n, &int_var, int_var);

62 0x200

printf(int_ptr is located at 0x%08x, contains 0x%08x, and points to %d\n\n, &int_ptr, int_ptr, *int_ptr);}

addressof2.c :

reader@hacking:~/booksrc $ gcc addressof2.creader@hacking:~/booksrc $ ./a.outint_ptr = 0xbffff834&int_ptr = 0xbffff830*int_ptr = 0x00000005

int_var is located at 0xbffff834 and contains 5int_ptr is located at 0xbffff830, contains 0xbffff834, and points to 5

reader@hacking:~/booksrc $

, , , - .

0x264

printf() -. , . , escape-, - .

, printf(), Hello, world!\n , - . Escape- -, , - , . - (%) - , -, examine GDB.

%d

%u

%x

0x260 63

, . , , :

%s

%n

%s ; , . %n , . -, - .

, - . fmt_strings.c .

fmt_strings.c#include

int main() { char string[10]; int A = -73; unsigned int B = 31337;

strcpy(string, sample); // printf([A] Dec: %d, Hex: %x, Unsigned: %u\n, A, A, A); printf([B] Dec: %d, Hex: %x, Unsigned: %u\n, B, B, B); printf([field width on B] 3: %3u, 10: %10u, %08u\n, B, B, B); printf([string] %s Address %08x\n, string, string);

// () %x printf(variable A is at address: %08x\n, &A);}

printf() . printf() &A, A. - .

reader@hacking:~/booksrc $ gcc -o fmt_strings fmt_strings.creader@hacking:~/booksrc $ ./fmt_strings[A] Dec: -73, Hex: ffffffb7, Unsigned: 4294967223[B] Dec: 31337, Hex: 7a69, Unsigned: 31337

64 0x200

[field width on B] 3: 31337, 10: 31337, 00031337[string] sample Address bffff870variable A is at address: bffff86creader@hacking:~/booksrc $

printf() A B . , A B - . %d - , %u , .

A %u, . , - A , - , - . - , - .

, [field width on B], -, . , - . : , , - . , , 3, 5 . 10, 5 . , 0, . , - 08 00031337.

, [string], - %s. , - , , , %s - .

A, - . - .

, %d, %u, %x. , - , 0, . %s , . .

/, scanf(), printf(),

0x260 65

, . scanf() , , , . - - . input.c .

input.c#include #include

int main() { char message[10]; int count, i;

strcpy(message, Hello, world!);

printf(Repeat how many times? ); scanf(%d, &count);

for(i=0; i < count; i++) printf(%3d - %s\n, i, message);}

input.c scanf() count. .

reader@hacking:~/booksrc $ gcc -o input input.creader@hacking:~/booksrc $ ./inputRepeat how many times? 3 0 - Hello, world! 1 - Hello, world! 2 - Hello, world!reader@hacking:~/booksrc $ ./inputRepeat how many times? 12 0 - Hello, world! 1 - Hello, world! 2 - Hello, world! 3 - Hello, world! 4 - Hello, world! 5 - Hello, world! 6 - Hello, world! 7 - Hello, world! 8 - Hello, world! 9 - Hello, world! 10 - Hello, world! 11 - Hello, world!reader@hacking:~/booksrc $

, - . , , , .

66 0x200

, , -, .

0x265

(typecasting) -, , , - . - , , . :

(__)

, , - typecasting.c.

typecasting.c#include

int main() { int a, b; float c, d;

a = 13; b = 5;

c = a / b; // . d = (float) a / (float) b; // , // float.

printf([integers]\t a = %d\t b = %d\n, a, b); printf([floats]\t c = %f\t d = %f\n, c, d);}

typecasting.c.

reader@hacking:~/booksrc $ gcc typecasting.creader@hacking:~/booksrc $ ./a.out[integers] a = 13 b = 5[floats] c = 2.000000 d = 2.600000reader@hacking:~/booksrc $

, 13 5 - 2, - . , - , 2,6.

0x260 67

, - -. , C - . - . , - . -. , . pointer_types.c . %p, . -, 0x%08x.

pointer_types.c#include

int main() { int i;

char char_array[5] = {a, b, c, d, e}; int int_array[5] = {1, 2, 3, 4, 5};

char *char_pointer; int *int_pointer;

char_pointer = char_array; int_pointer = int_array;

for(i=0; i < 5; i++) { // int_pointer. printf([integer pointer] points to %p, which contains the integer %d\n, int_pointer, *int_pointer); int_pointer = int_pointer + 1; }

for(i=0; i < 5; i++) { // char_pointer. printf([char pointer] points to %p, which contains the char %c\n, char_pointer, *char_pointer); char_pointer = char_pointer + 1; }}

: , . - , - . for - -. : -

68 0x200

%d %c, printf() -. *.

reader@hacking:~/booksrc $ gcc pointer_types.creader@hacking:~/booksrc $ ./a.out[integer pointer] points to 0xbffff7f0, which contains the integer 1[integer pointer] points to 0xbffff7f4, which contains the integer 2[integer pointer] points to 0xbffff7f8, which contains the integer 3[integer pointer] points to 0xbffff7fc, which contains the integer 4[integer pointer] points to 0xbffff800, which contains the integer 5[char pointer] points to 0xbffff810, which contains the char a[char pointer] points to 0xbffff811, which contains the char b[char pointer] points to 0xbffff812, which contains the char c[char pointer] points to 0xbffff813, which contains the char d[char pointer] points to 0xbffff814, which contains the char ereader@hacking:~/booksrc $

int_pointer char_pointer 1, - -. char 1 , 1 . integer 4 , 4 .

pointer_types2.c , - int_pointer -.

pointer_types2.c#include

int main() { int i;

char char_array[5] = {a, b, c, d, e}; int int_array[5] = {1, 2, 3, 4, 5};

char *char_pointer; int *int_pointer;

char_pointer = int_array; // char_pointer int_pointer int_pointer = char_array; //

for(i=0; i < 5; i++) { // int_pointer. printf([integer pointer] points to %p, which contains the integer %d\n, int_pointer, *int_pointer); int_pointer = int_pointer + 1; }

0x260 69

for(i=0; i < 5; i++) { // char_pointer. printf([char pointer] points to %p, which contains the integer %d\n, char_pointer, *char_pointer); char_pointer = char_pointer + 1; }}

, -.

reader@hacking:~/booksrc $ gcc pointer_types2.cpointer_types2.c: In function `main:pointer_types2.c:12: warning: assignment from incompatible pointer typepointer_types2.c:13: warning: assignment from incompatible pointer typereader@hacking:~/booksrc $

, , -. , , -. , , , , -.

reader@hacking:~/booksrc $ ./a.out[integer pointer] points to 0xbffff810, which contains the char a[integer pointer] points to 0xbffff814, which contains the char e[integer pointer] points to 0xbffff818, which contains the char 8[integer pointer] points to 0xbffff81c, which contains the char [integer pointer] points to 0xbffff820, which contains the char ?[char pointer] points to 0xbffff7f0, which contains the integer 1[char pointer] points to 0xbffff7f1, which contains the integer 0[char pointer] points to 0xbffff7f2, which contains the integer 0[char pointer] points to 0xbffff7f3, which contains the integer 0[char pointer] points to 0xbffff7f4, which contains the integer 2reader@hacking:~/booksrc $

int_pointer , - 5 , . , 1 4. char_pointer - 1, 20 ( 4-- ) . 4- , , . 4- 0x00000001 0x01, 0x00, 0x00, 0x00.

, . - , , . -

70 0x200

pointer_types3.c, - .

pointer_types3.c#include

int main() { int i;

char char_array[5] = {a, b, c, d, e}; int int_array[5] = {1, 2, 3, 4, 5};

char *char_pointer; int *int_pointer;

char_pointer = (char *) int_array; // int_pointer = (int *) char_array; // .

for(i=0; i < 5; i++) { // int_pointer. printf([integer pointer] points to %p, which contains the integer %d\n, int_pointer, *int_pointer); int_pointer = (int *) ((char *) int_pointer + 1); }

for(i=0; i < 5; i++) { // char_pointer.

printf([char pointer] points to %p, which contains the integer %d\n, char_pointer, *char_pointer); char_pointer = (char *) ((int *) char_pointer + 1); }}

. - C , - . , 1 , - . . , .

reader@hacking:~/booksrc $ gcc pointer_types3.creader@hacking:~/booksrc $ ./a.out[integer pointer] points to 0xbffff810, which contains the char a[integer pointer] points to 0xbffff811, which contains the char b[integer pointer] points to 0xbffff812, which contains the char c[integer pointer] points to 0xbffff813, which contains the char d[integer pointer] points to 0xbffff814, which contains the char e[char pointer] points to 0xbffff7f0, which contains the integer 1[char pointer] points to 0xbffff7f4, which contains the integer 2[char pointer] points to 0xbffff7f8, which contains the integer 3

0x260 71

[char pointer] points to 0xbffff7fc, which contains the integer 4[char pointer] points to 0xbffff800, which contains the integer 5reader@hacking:~/booksrc $

, , . C - void.

- . -, , . , , . -, void - , - . - , , .

pointer_types3.c , void, . , void , . void - . pointer_types4.c, void.

pointer_types4.c#include

int main() { int i;

char char_array[5] = {a, b, c, d, e}; int int_array[5] = {1, 2, 3, 4, 5};

void *void_pointer;

void_pointer = (void *) char_array;

for(i=0; i < 5; i++) { // char. printf([char pointer] points to %p, which contains the char %c\n, void_pointer, *((char *) void_pointer)); void_pointer = (void *) ((char *) void_pointer + 1); }

void_pointer = (void *) int_array;

for(i=0; i < 5; i++) { // int. printf([integer pointer] points to %p, which contains the integer %d\n, void_pointer, *((int *) void_pointer));

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void_pointer = (void *) ((int *) void_pointer + 1); }}

pointer_types4.c :

reader@hacking:~/booksrc $ gcc pointer_types4.creader@hacking:~/booksrc $ ./a.out[char pointer] points to 0xbffff810, which contains the char a[char pointer] points to 0xbffff811, which contains the char b[char pointer] points to 0xbffff812, which contains the char c[char pointer] points to 0xbffff813, which contains the char d[char pointer] points to 0xbffff814, which contains the char e[integer pointer] points to 0xbffff7f0, which contains the integer 1[integer pointer] points to 0xbffff7f4, which contains the integer 2[integer pointer] points to 0xbffff7f8, which contains the integer 3[integer pointer] points to 0xbffff7fc, which contains the integer 4[integer pointer] points to 0xbffff800, which contains the integer 5reader@hacking:~/booksrc $

pointer_types4.c pointer_types3.c - . void , , - .

, - void . , void - , - . pointer_types5.c - .

pointer_types5.c#include

int main() { int i;

char char_array[5] = {a, b, c, d, e}; int int_array[5] = {1, 2, 3, 4, 5};

unsigned int hacky_nonpointer;

hacky_nonpointer = (unsigned int) char_array;

for(i=0; i < 5; i++) { // char. printf([hacky_nonpointer] points to %p, which contains the char %c\n, hacky_nonpointer, *((char *) hacky_nonpointer)); hacky_nonpointer = hacky_nonpointer + sizeof(char); }

0x260 73

hacky_nonpointer = (unsigned int) int_array;

for(i=0; i < 5; i++) { // int. printf([hacky_nonpointer] points to %p, which contains the integer %d\n, hacky_nonpointer, *((int *) hacky_nonpointer)); hacky_nonpointer = hacky_nonpointer + sizeof(int); }}

, - , .

: - - sizeof() , - .

reader@hacking:~/booksrc $ gcc pointer_types5.creader@hacking:~/booksrc $ ./a.out[hacky_nonpointer] points to 0xbffff810, which contains the char a[hacky_nonpointer] points to 0xbffff811, which contains the char b[hacky_nonpointer] points to 0xbffff812, which contains the char c[hacky_nonpointer] points to 0xbffff813, which contains the char d[hacky_nonpointer] points to 0xbffff814, which contains the char e[hacky_nonpointer] points to 0xbffff7f0, which contains the integer 1[hacky_nonpointer] points to 0xbffff7f4, which contains the integer 2[hacky_nonpointer] points to 0xbffff7f8, which contains the integer 3[hacky_nonpointer] points to 0xbffff7fc, which contains the integer 4[hacky_nonpointer] points to 0xbffff800, which contains the integer 5reader@hacking:~/booksrc $

C, , - . , - . , , - .

0x266

, , - . scanf(), - . .

C main(), : . -

74 0x200

, . commandline.c.

commandline.c#include

int main(int arg_count, char *arg_list[]) { int i; printf(There were %d arguments provided:\n, arg_count); for(i=0; i < arg_count; i++) printf(argument #%d\t-\t%s\n, i, arg_list[i]);}

reader@hacking:~/booksrc $ gcc -o commandline commandline.creader@hacking:~/booksrc $ ./commandlineThere were 1 arguments provided:argument #0 - ./commandlinereader@hacking:~/booksrc $ ./commandline this is a testThere were 5 arguments provided:argument #0 - ./commandlineargument #1 - thisargument #2 - isargument #3 - aargument #4 - testreader@hacking:~/booksrc $

-, ( ) , .

, . , . , - , , . atoi() ( ASCII to integer), - ASCII- . - , , . convert.c.

convert.c#include

void usage(char *program_name) { printf(Usage: %s \n, program_name); exit(1);}

int main(int argc, char *argv[]) {

0x260 75

int i, count;

if(argc < 3) // 3, usage(argv[0]); // , , .

count = atoi(argv[2]); // 2- . printf(Repeating %d times..\n, count);

for(i=0; i < count; i++) printf(%3d - %s\n, i, argv[1]); // 1- .}

convert.c.

reader@hacking:~/booksrc $ gcc convert.creader@hacking:~/booksrc $ ./a.outUsage: ./a.out reader@hacking:~/booksrc $ ./a.out Hello, world! 3Repeating 3 times.. 0 - Hello, world! 1 - Hello, world! 2 - Hello, world!reader@hacking:~/booksrc $

, if - . - , . C - . - if, , -, . convert2.c.

convert2.c#include

void usage(char *program_name) { printf(Usage: %s \n, program_name); exit(1);}

int main(int argc, char *argv[]) { int i, count;

// if(argc < 3) // 3, // usage(argv[0]); // , , // .

count = atoi(argv[2]); // 2- . printf(Repeating %d times..\n, count);

76 0x200

for(i=0; i < count; i++) printf(%3d - %s\n, i, argv[1]); // 1- .}

convert2.c.

reader@hacking:~/booksrc $ gcc convert2.creader@hacking:~/booksrc $ ./a.out testSegmentation fault (core dumped)reader@hacking:~/booksrc $

, , . - .

( ), - , . , , - (segmentation fault). - GDB.

reader@hacking:~/booksrc $ gcc -g convert2.creader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) run testStarting program: /home/reader/booksrc/a.out test

Program received signal SIGSEGV, Segmentation fault.0xb7ec819b in ?? () from /lib/tls/i686/cmov/libc.so.6(gdb) where#0 0xb7ec819b in ?? () from /lib/tls/i686/cmov/libc.so.6#1 0xb800183c in ?? ()#2 0x00000000 in ?? ()(gdb) break mainBreakpoint 1 at 0x8048419: file convert2.c, line 14.(gdb) run testThe program being debugged has been started already.Start it from the beginning? (y or n) yStarting program: /home/reader/booksrc/a.out test

Breakpoint 1, main (argc=2, argv=0xbffff894) at convert2.c:1414 count = atoi(argv[2]); // 2- // .(gdb) contContinuing.

Program received signal SIGSEGV, Segmentation fault.0xb7ec819b in ?? () from /lib/tls/i686/cmov/libc.so.6(gdb) x/3xw 0xbffff8940xbffff894: 0xbffff9b3 0xbffff9ce 0x00000000

0x260 77

(gdb) x/s 0xbffff9b30xbffff9b3: /home/reader/booksrc/a.out(gdb) x/s 0xbffff9ce0xbffff9ce: test(gdb) x/s 0x000000000x0: (gdb) quitThe program is running. Exit anyway? (y or n) yreader@hacking:~/booksrc $

GDB test, . where - , - . - main , ( ). - , . x/3xw , , , . , test, , . - .

0x267

, C, -, -. -, . , - , - . printf() scope.c.

scope.c#include

void func3() { int i = 11; printf(\t\t\t[in func3] i = %d\n, i);}

void func2() { int i = 7; printf(\t\t[in func2] i = %d\n, i); func3(); printf(\t\t[back in func2] i = %d\n, i);}

78 0x200

void func1() { int i = 5; printf(\t[in func1] i = %d\n, i); func2(); printf(\t[back in func1] i = %d\n, i);}

int main() { int i = 3; printf([in main] i = %d\n, i); func1(); printf([back in main] i = %d\n, i);}

- .

reader@hacking:~/booksrc $ gcc scope.creader@hacking:~/booksrc $ ./a.out[in main] i = 3 [in func1] i = 5 [in func2] i = 7 [in func3] i = 11 [back in func2] i = 7 [back in func1] i = 5[back in main] i = 3reader@hacking:~/booksrc $

i - . : main() - i 3 func1(), - i 5. func1() i - 5 func2(), 7, . , i.

, . -, - . scope2.c j - 42. - , -.

scope2.c#include

int j = 42; // j

void func3() { int i = 11, j = 999; // j - func3().

0x260 79

printf(\t\t\t[in func3] i = %d, j = %d\n, i, j);}

void func2() { int i = 7; printf(\t\t[in func2] i = %d, j = %d\n, i, j); printf(\t\t[in func2] setting j = 1337\n); j = 1337; // j func3(); printf(\t\t[back in func2] i = %d, j = %d\n, i, j);}

void func1() { int i = 5; printf(\t[in func1] i = %d, j = %d\n, i, j); func2(); printf(\t[back in func1] i = %d, j = %d\n, i, j);}

int main() { int i = 3; printf([in main] i = %d, j = %d\n, i, j); func1(); printf([back in main] i = %d, j = %d\n, i, j);}

scope2.c:

reader@hacking:~/booksrc $ gcc scope2.creader@hacking:~/booksrc $ ./a.out[in main] i = 3, j = 42 [in func1] i = 5, j = 42 [in func2] i = 7, j = 42 [in func2] setting j = 1337 [in func3] i = 11, j = 999 [back in func2] i = 7, j = 1337 [back in func1] i = 5, j = 1337[back in main] i = 3, j = 1337reader@hacking:~/booksrc $

, j func2() - , , func3(), j. - . - , , , . - j , . - , -. , ,

80 0x200

. , scope3.c - .

scope3.c#include

int j = 42; // j .

void func3() { int i = 11, j = 999; // j func3() printf(\t\t\t[in func3] i @ 0x%08x = %d\n, &i, i); printf(\t\t\t[in func3] j @ 0x%08x = %d\n, &j, j);}

void func2() { int i = 7; printf(\t\t[in func2] i @ 0x%08x = %d\n, &i, i); printf(\t\t[in func2] j @ 0x%08x = %d\n, &j, j); printf(\t\t[in func2] setting j = 1337\n); j = 1337; // Writing to j func3(); printf(\t\t[back in func2] i @ 0x%08x = %d\n, &i, i); printf(\t\t[back in func2] j @ 0x%08x = %d\n, &j, j);}

void func1() { int i = 5; printf(\t[in func1] i @ 0x%08x = %d\n, &i, i); printf(\t[in func1] j @ 0x%08x = %d\n, &j, j); func2(); printf(\t[back in func1] i @ 0x%08x = %d\n, &i, i); printf(\t[back in func1] j @ 0x%08x = %d\n, &j, j);}

int main() { int i = 3; printf([in main] i @ 0x%08x = %d\n, &i, i); printf([in main] j @ 0x%08x = %d\n, &j, j); func1(); printf([back in main] i @ 0x%08x = %d\n, &i, i); printf([back in main] j @ 0x%08x = %d\n, &j, j);}

scope3.c:

reader@hacking:~/booksrc $ gcc scope3.creader@hacking:~/booksrc $ ./a.out[in main] i @ 0xbffff834 = 3[in main] j @ 0x08049988 = 42 [in func1] i @ 0xbffff814 = 5 [in func1] j @ 0x08049988 = 42

0x260 81

[in func2] i @ 0xbffff7f4 = 7 [in func2] j @ 0x08049988 = 42 [in func2] setting j = 1337 [in func3] i @ 0xbffff7d4 = 11 [in func3] j @ 0xbffff7d0 = 999 [back in func2] i @ 0xbffff7f4 = 7 [back in func2] j @ 0x08049988 = 1337 [back in func1] i @ 0xbffff814 = 5 [back in func1] j @ 0x08049988 = 1337[back in main] i @ 0xbffff834 = 3[back in main] j @ 0x08049988 = 1337reader@hacking:~/booksrc $

, j, func3(), j . j func3() 0xbffff7d0, j 0x08049988. , i, .

, GDB func3(). backtrace - , .

reader@hacking:~/booksrc $ gcc -g scope3.creader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) list 11 #include 23 int j = 42; // j .45 void func3() {6 int i = 11, j = 999; // j func3().7 printf(\t\t\t[in func3] i @ 0x%08x = %d\n, &i, i);8 printf(\t\t\t[in func3] j @ 0x%08x = %d\n, &j, j);9 }10(gdb) break 7Breakpoint 1 at 0x8048388: file scope3.c, line 7.(gdb) runStarting program: /home/reader/booksrc/a.out[in main] i @ 0xbffff804 = 3[in main] j @ 0x08049988 = 42 [in func1] i @ 0xbffff7e4 = 5 [in func1] j @ 0x08049988 = 42 [in func2] i @ 0xbffff7c4 = 7 [in func2] j @ 0x08049988 = 42 [in func2] setting j = 1337

Breakpoint 1, func3 () at scope3.c:77 printf(\t\t\t[in func3] i @ 0x%08x = %d\n, &i, i);(gdb) bt

82 0x200

#0 func3 () at scope3.c:7#1 0x0804841d in func2 () at scope3.c:17#2 0x0804849f in func1 () at scope3.c:26#3 0x0804852b in main () at scope3.c:35(gdb)

, . - , (stack frame). . - -. GDB, backtrace full ().

(gdb) bt full#0 func3 () at scope3.c:7 i = 11 j = 999#1 0x0804841d in func2 () at scope3.c:17 i = 7#2 0x0804849f in func1 () at scope3.c:26 i = 5#3 0x0804852b in main () at scope3.c:35 i = 3(gdb)

, - j func3(). - j.

, , - static. , - ; , . , . static.c.

static.c#include

void function() { // int var = 5; static int static_var = 5; //

printf(\t[in function] var = %d\n, var); printf(\t[in function] static_var = %d\n, static_var); var++; // 1 var. static_var++; // 1 static_var.}

0x260 83

int main() { // main int i; static int static_var = 1337; // //

for(i=0; i < 5; i++) { // 5 printf([in main] static_var = %d\n, static_var); function(); // . }}

static_var : - main() function(). , , . function 1. - , - .

reader@hacking:~/booksrc $ gcc static.creader@hacking:~/booksrc $ ./a.out[in main] static_var = 1337 [in function] var = 5 [in function] static_var = 5[in main] static_var = 1337 [in function] var = 5 [in function] static_var = 6[in main] static_var = 1337 [in function] var = 5 [in function] static_var = 7[in main] static_var = 1337 [in function] var = 5 [in function] static_var = 8[in main] static_var = 1337 [in function] var = 5 [in function] static_var = 9reader@hacking:~/booksrc $

: static_var - function(). , - , , - . , - - , static_var main() 1337.

, , . , -, static2.c.

84 0x200

static2.c#include

void function() { // int var = 5; static int static_var = 5; //

printf(\t[in function] var @ %p = %d\n, &var, var); printf(\t[in function] static_var @ %p = %d\n, &static_var, static_var); var++; // 1 var. static_var++; // 1 static_var.}

int main() { // main int i; static int static_var = 1337; // ,

for(i=0; i < 5; i++) { // loop 5 times printf([in main] static_var @ %p = %d\n, &static_var, static_var); function(); // . }}

static2.c:

reader@hacking:~/booksrc $ gcc static2.creader@hacking:~/booksrc $ ./a.out[in main] static_var @ 0x804968c = 1337 [in function] var @ 0xbffff814 = 5 [in function] static_var @ 0x8049688 = 5[in main] static_var @ 0x804968c = 1337 [in function] var @ 0xbffff814 = 5 [in function] static_var @ 0x8049688 = 6[in main] static_var @ 0x804968c = 1337 [in function] var @ 0xbffff814 = 5 [in function] static_var @ 0x8049688 = 7[in main] static_var @ 0x804968c = 1337 [in function] var @ 0xbffff814 = 5 [in function] static_var @ 0x8049688 = 8[in main] static_var @ 0x804968c = 1337 [in function] var @ 0xbffff814 = 5 [in function] static_var @ 0x8049688 = 9reader@hacking:~/booksrc $

, static_var main() - function(), (0x804968c 0x8049688 ). , -, , , 0xbffff814, , 0x0804968c 0x8049688. , :

0x270 85

. , .

0x270 , , : , (text), (data), bss, (heap) (stack). , .

text . - . - - , - , -. EIP - text. -, :

1. , EIP.

2. EIP .

3. , 1.

4. 1.

, EIP . , . 3 EIP , - 1 , , EIP.

text : , -. : - , , . - , - , . -, , .

bss - . data , bss . , . , ( j ).

86 0x200

, .

(heap) . - - . , -. (allocator) (deallocator): , , . - , . , , . - , - .

(stack) ; - . - GDB. , - , - (). EIP, , , EIP , . -. .

. - (FILO), , , , . - : -, . - (pushing), - (popping).

, () . - ESP, . - , . - , - , .

FILO, , , - . . , , -

0x270 87

EBP, (frame pointer, FP) (local base, LB). , - , , : (saved frame pointer, SFP) . SFP EBP -, EIP -, . .

stack_example.c : main() test_function().

stack_example.cvoid test_function(int a, int b, int c, int d) { int flag; char buffer[10]; flag = 31337; buffer[0] = A;}int main() { test_function(1, 2, 3, 4);}

test_function - : a, b, c d. 4- flag 10- buf-fer. , - text. - , GDB. - main() test_function(). main() 0x08048357, test_function() 0x08048344. ( -) . - . . . - -, .

reader@hacking:~/booksrc $ gcc -g stack_example.creader@hacking:~/booksrc $ gdb -q ./a.outUsing host libthread_db library /lib/tls/i686/cmov/libthread_db.so.1.(gdb) disass mainDump of assembler code for function main():0x08048357 : push ebp0x08048358 : mov ebp,esp0x0804835a : sub esp,0x180x0804835d : and esp,0xfffffff0

88 0x200

0x08048360 : mov eax,0x00x08048365 : sub esp,eax0x08048367 : mov DWORD PTR [esp+12],0x40x0804836f : mov DWORD PTR [esp+8],0x30x08048377 : mov DWORD PTR [esp+4],0x20x0804837f : mov DWORD PTR [esp],0x10x08048386 : call 0x8048344 0x0804838b : leave0x0804838c : retEnd of assembler dump(gdb) disass test_function()Dump of assembler code for function test_function:0x08048344 : push ebp0x08048345 : mov ebp,esp0x08048347 : sub esp,0x280x0804834a : mov DWORD PTR [ebp-12],0x7a690x08048351 : mov BYTE PTR [ebp-40],0x410x08048355 : leave0x08048356 : retEnd of assembler dump(gdb)

main(), test_function().

test_function() main() - , . (- FILO). 1, 2, 3 4, 4, 3, 2 1. d, c, b a . , , main() -.

(gdb) disass mainDump of assembler code for function main:0x08048357 : push ebp0x08048358 : mov ebp,esp0x0804835a : sub esp,0x180x0804835d : and esp,0xfffffff00x08048360 : mov eax,0x00x08048365 : sub esp,eax0x08048367 : mov DWORD PTR [esp+12],0x40x0804836f : mov DWORD PTR [esp+8],0x30x08048377 : mov DWORD PTR [esp+4],0x20x0804837f : mov DWORD PTR [esp],0x10x08048386 : call 0x8048344 0x0804838b : leave0x0804838c : retEnd of assembler dump(gdb)

0x270 89

call , test_func-tion() 0x08048344. -, , EIP, - , 3 -. 0x0804838b, main() leave.

call EIP test_function(); -, test_function() . EBP. - (SFP) - EBP . ESP - EBP, . - (flag buffer). - ESP. , . 2.1.

buffer

flag

(SFP)

(ret)

a

b

c

d

(EBP)

. 2.1.

GDB , . main() - test_function() test_function(). GDB , - , test_function().

-, ESP ( ), EBP ( ) EIP ( ).

90 0x200

(gdb) list main45 flag = 31337;6 buffer[0] = A;7 }89 int main() {10 test_function(1, 2, 3, 4);11 }(gdb) break 10Breakpoint 1 at 0x8048367: file stack_example.c, line 10.(gdb) break test_functionBreakpoint 2 at 0x804834a: file stack_example.c, line 5.(gdb) runStarting program: /home/reader/booksrc/a.out

Breakpoint 1, main () at stack_example.c:1010 test_function(1, 2, 3, 4);(gdb) i r esp ebp eipesp 0xbffff7f0 0xbffff7f0ebp 0xbffff808 0xbffff808eip 0x8048367 0x8048367 (gdb) x/5i $eip0x8048367 : mov DWORD PTR [esp+12],0x40x804836f : mov DWORD PTR [esp+8],0x30x8048377 : mov DWORD PTR [esp+4],0x20x804837f : mov DWORD PTR [esp],0x10x8048386 : call 0x8048344 (gdb)

, - test_function(). - , - ESP, 0xbffff7f0. test_function(), - . - . - (flag buffer) - (EBP).

(gdb) contContinuing.

Breakpoint 2, test_function (a=1, b=2, c=3, d=4) at stack_example.c:55 flag = 31337;(gdb) i r esp ebp eipesp 0xbffff7c0 0xbffff7c0ebp 0xbffff7e8 0xbffff7e8eip 0x804834a 0x804834a (gdb) disass test_functionDump of assembler code for function test_function:

0x270 91

0x08048344 : push ebp0x08048345 : mov ebp,esp0x08048347 : sub esp,0x280x0804834a : mov DWORD PTR [ebp-12],0x7a690x08048351 : mov BYTE PTR [ebp-40],0x410x08048355 : leave0x08048356 : retEnd of assembler dump.(gdb) print $ebp-12$1 = (void *) 0xbffff7dc(gdb) print $ebp-40$2 = (void *) 0xbffff7c0(gdb) x/16xw $esp0xbffff7c0: 1 0x00000000 0x08049548 0xbffff7d8 0x080482490xbffff7d0: 0xb7f9f729 0xb7fd6ff4 0xbffff808 2 0x080483b90xbffff7e0: 0xb7fd6ff4 0xbffff89c 3 0xbffff808 4 0x0804838b0xbffff7f0: 5 0x00000001 0x00000002 0x00000003 0x00000004(gdb)

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92 0x200

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0x271 C

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