To round out the work done by mihi for x86 stages back in the day,
this PR provides x64 Windows stage encryption in RC4 via assembly
written/modified by max3raza during adjacent work on DNS tunneled
transport.
Stage encryption differs from encoding in that there is no decoder
stub or key materiel carried with the stage which can be used by
defensive systems to decode and identify the contents. Persistence
payloads, oob-delivered stage0, and other contexts benefit heavily
from this as their subsequent stage is difficult to detect/identify,
and the chance of accidental execution of the wrong payload/stage
is drastically reduced if separate keys are in play for individual
targets - acquiring the wrong stage will result in decryption
failure and prevent further execution.
For historical context, all of the RC4 stagers implement in-place
decryption via stage0 for the contents of stage1 using the provided
passphrase converted to a key and embedded in stage0 as part of the
payload.
Testing:
In-house testing with Max - we got sessions, loaded extensions.
Notes:
All credit for the work goes to Max3raza - big ups for getting
this knocked out.
This is a repackaging effort for the work i originally pushed in
6035. This segment of the PR provides UDP session handlers for
bind and reverse sessions, a Windows Metasm stager (really the
TCP stager with a small change), and a pair of socat payloads for
testing simple UDP shells. Netcat or any scripting language with
a sockets library is sufficient to use these sessions as they are
stateless and simple.
Testing of this PR requires rex/core #1 and rex/socket #2
The SSL testing which was being done on 6035 is backed out, left
for a later time when we can do DTLS properly.
Powershell payloads were generating using the :generate method
mixed in from Payload::Windows::Exec which is a binary payload
mixin.
Address the breakage by implementing a generate method which simply
outputs the script code produced by the module with no additional
content prepended or appended.
While here, cleanup the commandline generation for the script being
produced by having Rex do it (this permits changes made in Rex to
benefit all consumers).
As a bonus, drop the IEX invocation since it'll trip up AMSI and
upgrade to the scripblock execution semantic.
Credit for finding this little gem goes to bperry - i dont usually
use the native powershell command shells, and managed to miss this
for a long time. Thanks boss.
Testing:
Local in pry
@bperry: Could you test and ping me back if this is right?
The Session GUID will identify active sessions, and is the beginning of
work that will allow for tracking of sessions that have come back alive
after failing or switching transports.
Summus6