hacking-the-art-of-exploitation

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don’t have malicious intent; instead, they help vendors fix their vulnerable software. Without hackers, the vulnerabilities and holes in software would remain undiscovered. Unfortunately, the legal system is slow and mostly ignorant with regard to technology. Often, draconian laws are passed and excessive sentences are given to try to scare people away from looking closely. This is childish logic—discouraging hackers from exploring and looking for vulnerabilities doesn’t solve anything. Convincing everyone the emperor is wearing fancy new clothes doesn’t change the reality that he’s naked. Undiscovered vulnerabilities just lie in wait for someone much more malicious than an average hacker to discover them. The danger of software vulnerabilities is that the payload could be anything. Replicating Internet worms are relatively benign when compared to the nightmare terrorism scenarios these laws are so afraid of. Restricting hackers with laws can make the worst-case scenarios more likely, since it leaves more undiscovered vulnerabilities to be exploited by those who aren’t bound by the law and want to do real damage. Some could argue that if there weren’t hackers, there would be no reason to fix these undiscovered vulnerabilities. That is one perspective, but personally I prefer progress over stagnation. Hackers play a very important role in the co-evolution of technology. Without hackers, there would be little reason for computer security to improve. Besides, as long as the questions “Why?” and “What if?” are asked, hackers will always exist. A world without hackers would be a world without curiosity and innovation. Hopefully, this book has explained some basic techniques of hacking and perhaps even the spirit of it. Technology is always changing and expanding, so there will always be new hacks. There will always be new vulnerabilities in software, ambiguities in protocol specifications, and a myriad of other oversights. The knowledge gained from this book is just a starting point. It’s up to you to expand upon it by continually figuring out how things work, wondering about the possibilities, and thinking of the things that the developers didn’t think of. It’s up to you to make the best of these discoveries and apply this knowledge however you see fit. Information itself isn’t a crime. 0x810 References Aleph1. “Smashing the Stack for Fun and Profit.” Phrack, no. 49, online publication at http://www.phrack.org/issues.html?issue=49&id=14#article Bennett, C., F. Bessette, and G. Brassard. “Experimental Quantum Cryptography.” Journal of Cryptology, vol. 5, no. 1 (1992), 3–28. Borisov, N., I. Goldberg, and D. Wagner. “Security of the WEP Algorithm.” Online publication at http://www.isaac.cs.berkeley.edu/isaac/ wep-faq.html Brassard, G. and P. Bratley. Fundamentals of Algorithmics. Englewood Cliffs, NJ: Prentice Hall, 1995. 452 0x800
CNET News. “40-Bit Crypto Proves No Problem.” Online publication at http://www.news.com/News/Item/0,4,7483,00.html Conover, M. (Shok). “w00w00 on Heap Overflows.” Online publication at http://www.w00w00.org/files/articles/heaptut.txt Electronic Frontier Foundation. “Felten vs. RIAA.” Online publication at http://www.eff.org/IP/DMCA/Felten_v_RIAA Eller, R. (caezar). “Bypassing MSB Data Filters for Buffer Overflow Exploits on Intel Platforms.” Online publication at http://community.core-sdi .com/~juliano/bypass-msb.txt Fluhrer, S., I. Mantin, and A. Shamir. “Weaknesses in the Key Scheduling Algorithm of RC4.” Online publication at http://citeseer.ist.psu.edu/ fluhrer01weaknesses.html Grover, L. “Quantum Mechanics Helps in Searching for a Needle in a Haystack.” Physical Review Letters, vol. 79, no. 2 (1997), 325–28. Joncheray, L. “Simple Active Attack Against TCP.” Online publication at http://www.insecure.org/stf/iphijack.txt Levy, S. Hackers: Heroes of the Computer Revolution. New York: Doubleday, 1984. McCullagh, D. “Russian Adobe Hacker Busted,” Wired News, July 17, 2001. Online publication at http://www.wired.com/news/politics/ 0,1283,45298,00.html The NASM Development Team. “NASM—The Netwide Assembler (Manual),” version 0.98.34. Online publication at http://nasm .sourceforge.net Rieck, K. “Fuzzy Fingerprints: Attacking Vulnerabilities in the Human Brain.” Online publication at http://freeworld.thc.org/papers/ffp.pdf Schneier, B. Applied Cryptography: Protocols, Algorithms, and Source Code in C, 2nd ed. New York: John Wiley & Sons, 1996. Scut and Team Teso. “Exploiting Format String Vulnerabilities,” version 1.2. Available online at private users’ websites. Shor, P. “Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer.” SIAM Journal of Computing, vol. 26 (1997), 1484–509. Online publication at http://www.arxiv.org/abs/ quant-ph/9508027 Smith, N. “Stack Smashing Vulnerabilities in the UNIX Operating System.” Available online at private users’ websites. Solar Designer. “Getting Around Non-Executable Stack (and Fix).” BugTraq post, August 10, 1997. Stinson, D. Cryptography: Theory and Practice. Boca Raton, FL: CRC Press, 1995. Zwicky, E., S. Cooper, and D. Chapman. Building Internet Firewalls, 2nd ed. Sebastopol, CA: O’Reilly, 2000. Conclusion 453
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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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ESP up (toward lower memory address
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eader@hacking:~/booksrc $ gcc -o pr
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At the end, the shellcode has been
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esp 0xbffffa2c 0xbffffa2c eax 0x0 0
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functions are shared, so any progra
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A quick binary search shows that th
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eginning of the buffer. When a prog
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The breakpoint is set at the last i
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Bouncing off linux-gate refers to a
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matrix@loki /hacking $ for i in `se
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manual page for execve() for detail
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for(i=0; i < 90; i+=4) // Fill buff
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encryption, credit card transaction
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through the incorrect filter, its p
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This means that, in general, the gr
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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
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: 0x800 CONCLUSION Hacking tends to b
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
Page 485 and 486: text segment, of memory, 69 then ke
Page 488 and 489: More No-Nonsense Books from NO STAR
Page 490: UPDATES Visit http://www.nostarch.c
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