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Downloading DECRYPT2
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splunk

DECRYPT2

Splunk Cloud
Overview
Details
DECRYPT2 is a fork of DECRYPT by Michael Zalewski
DECRYPT is a set of Splunk commands which provide Base32, Base64, XOR, ROTX, RC4 and ROL/ROR routines which are commonly used for obfuscating malware communications and data exfiltration.

These commands can be leveraged in Splunk queries by users or automation to decipher previously indexed communications.

. _
| /_ _ ._._/ |_
/
|/ _/ _ _ < | |_ \ __\
/ /
/ \ /\ __| | \/_ || |_> > |
_ |__ >_ >
| / _|| _/||
\/ \/ \/ \/ |__|v2.3.2

                    Original author: Michael Zalewski <mjz@hexize.com>
                    New maintainer: Gareth Anderson

DECRYPT is a set of Splunk commands which provide encryption and
decryption routines commonly used in malware communication and data
exfiltration.

Installation

DECRYPT is a standard Splunk App and requires no special configuration.

Usage

DECRYPT is implemented as a single search command which exposes a number of data manipulation functions. It takes the required field to manipulate and then one or more functions as arguments.

Usage: decrypt [field=<name>] FUNCTIONS...

The following example will transform the sourcetype field into its hex representation:

... | decrypt field=sourcetype hex() emit('sourcetype')
Note: Fields must be output via the emit function. The input field is not modified in place.
If the emit function is not mentioned, an emit('decrypted') is automatically added so the data is output

Arguments

field

The field argument specifies the Splunk field to use as input.

... | decrypt field="hostname" ...
If no field argument is passed then _raw will be used by default.

If a field argument is passed and the field does not exist in the current record being processed, no error or warning will be given.

FUNCTIONS

Each function passed as an argument will be executed in order, with the output of the previous function provided as input to the next.

... | decrypt field=hostname b64 xor('s\x65cr\x65t') hex emit('decrypted')
The above example can be explained as:

Pass the value of the hostname field to b64 as input
Pass the output of b64 to xor as input with the argument 's\x65cr\x65t'
Pass the output of xor to hex as input
Pass the output of hex to emit with the argument 'decrypted'

Functions

btoa()
Encodes input to a Base64 string.

b64(), atob()
Decodes a Base64 encoded string.

b32()
Decodes a Base32 encoded string.

rotx(count)
Implements Caesarian shift. The count argument specifies the amount to shift and must be an integer.

rol(count)
Implements rotate-on-left to each character within the string using an 8 bit boundary. The count argument specifies the amount to rotate and must be an integer.

ror(count)
Implements rotate-on-right to each character within the string using an 8 bit boundary. The count argument specifies the amount to rotate and must be an integer.

xor(key)
Implements basic XOR cipher against the field with the supplied key. The key can be provided as a string or integer.

rc4(key)
Implements the RC4 cipher against the field with the supplied key. The key provided must be a string.

hex()
Transforms input into its hexadecimal representation.

unhex()
Transforms hexadecimal input into its byte form.

save(name)
Saves the current state to memory as name.

load(name)
Recalls the previously saved state name from memory.

ascii()
Transforms input into ASCII output. Non-printable characters will be replaced with a period.

emit(name)
Outputs the current state as UTF-8 to the field name.

substr(offset, count)
Returns a substring of the input, starting at the index offset with the number of characters count.

Function Arguments

Strings

Strings can be specified by encapsulating values in apostrophes (single quote). Strings accept Pythonic escape sequences, so hexadecimal and octal values can be specified with \xhh and \ooo respectively.

'This is a valid string'
'This is also \x61 valid string.'

Quotation marks (double quotes) cannot be used.

"This is not a valid string"

Integers

Integers can be specified numerically or as hexadecimal representations by prefixing values with a 0x.

The value 256 could be passed as is or as its hexadecimal representation 0x100.

Field References

The value of Splunk fields can be used in function parameters by passing the field name as an argument. All referenced fields must be complete words unbroken by whitespace.

... | decrypt field=_raw xor(sourcetype) ...
The above example demonstrates passing the sourcetype field as the key to the xor function.

Fields saved using the save command can also be referenced.

... | decrypt field=_raw substr(0,1) save('1byte') substr(1, 4096) xor(1byte) ...

Style

Functions which take no arguments do not need parenthesis in order for syntax checking to pass. The following examples will pass syntax checks and execute the same.

... | decrypt field=_raw b64 hex unhex
... | decrypt field=_raw b64() hex() unhex()
... | decrypt field=_raw b64() hex unhex
New lines can be used to break up command sequences for easier readability.

... | decrypt field=_raw
b64
hex
unhex

Recipes

XOR

... | decrypt field=data xor('secret') emit('result')

ROT13 cipher

... | decrypt field=data rotx(13) emit('result')

Base64 decode, XOR

... | decrypt field=data b64 xor('secret') emit('result')

Base64 decode, XOR with first byte

... | decrypt field=data
b64
save('bin')
substr(0, 1) emit('key')
load('bin')
substr(1, 9999) xor(key) emit('result')

Brute force RC4

... | decrypt field=data
b64
save('orig') rc4('secret') emit('rc4-secret')
load('orig') rc4('password') emit('rc4-password')
load('orig') rc4('abc123') emit('rc4-abc123')
load('orig') rc4('aabbccdd') emit('rc4-aabbccdd')

Brute force XOR key

... | decrypt field=data
b64
save('data') xor(0x01) emit('xor0x01')
load('data') xor(0x02) emit('xor0x02')
load('data') xor(0x03) emit('xor0x03')
...

Contributors

Shannon Davis (Splunk)

Release Notes

2.3.4

New functionality based on pull requests by Steven (malvidin) on github

decode
escape
unescape
tr

2.3.3

  • Minor update to license file
  • The field .decrypt_failure__ is not only output when there is an error (previously always output)
  • If the emit function is ommitted, the output now defaults to 'decrypted' as the field name

2.3.2

Fork of version 2.3.1 of DECRYPT app from SplunkBase (under MIT license)
- Updated python SDK to version 1.6.15
- default.meta file now includes read * and write to admin, power
- Created a README.md file

2.3.1

Feb. 16, 2021
- Bug fix for distributed search environments

2.3.0

  • Unicode support
  • Introduce ascii command
  • Command change to SCPv2
  • Changes to save/load command mechanics

2.2.1

  • Bug fix and minor package metadata updates

2.2

  • Addition of Base32 decoding
  • Addition of Base64 decoding alias (b64)

2.1

  • Works with Splunk 8.x
  • Bug fix to work in distributed search environments

2.0

  • Rearchitected due to a limitation with passing binary data between commands
  • Introduced SAVE/LOAD/EMIT/HEX/UNHEX functions

1.0

  • Initial release

Release Notes

Version 2.3.10
June 20, 2022

Merged pull request from Steven (malvidin on github)

When Splunk sends a CSV that contains null bytes to Python 3.7, the CSV Reader error is not helpful
This update provides a warning to advise of the null character in the data (sed/rex/eval/replace can be used to remove the NUL character)

Version 2.3.9
June 14, 2022

Updated Splunk python SDK to 1.6.20

Version 2.3.8
April 30, 2022

Merged pull request from Steven (malvidin on github)

  • New find function
  • New b32re, and b64re functions that use the reverse endian decoding used by the SunBurst DGA
Version 2.3.7
April 23, 2022

Merged pull request from Steven (malvidin on github)

  • New rev function
  • Decreased differences with python2

Updated Splunk python SDK to 1.6.19

Version 2.3.6
Feb. 27, 2022

Updated the metadata file to include the sc_admin role

Version 2.3.5
Jan. 29, 2022

Merged pull request from Steven (malvidin on github)

  • Escape ASCII control characters
  • New functionality based on pull requests by Steven (malvidin) on GitHub

htmlescape
htmlunescape

Note: htmlescape is not implemented for Python 2

Updated Splunk python SDK to 1.6.18

Version 2.3.4
Aug. 15, 2021

Note the Splunk Python Readiness app incorrectly flags this as not compatible, I've tested on python3 without an issue

New functionality based on pull requests by Steven (malvidin) on github
decode
escape
unescape
tr

This is a fork of the DECRYPT app by Michael Zalewski which is now archived
Version 2.3.3
- Minor update to license file
- The field .decrypt_failure__ is not only output when there is an error (previously always output)
- If the emit function is ommitted, the output now defaults to 'decrypted' as the field name

DECRYPT is a set of Splunk commands which provide Base32, Base64, XOR, ROTX, RC4 and ROL/ROR routines which are commonly used for obfuscating malware communications and data exfiltration.

These commands can be leveraged in Splunk queries by users or automation to decipher previously indexed communications.

Version 2.3.3
June 25, 2021

Note the Splunk Python Readiness app incorrectly flags this as not compatible, I've tested on python3 without an issue

This is a fork of the DECRYPT app by Michael Zalewski which is now archived
Version 2.3.3
- Minor update to license file
- The field .decrypt_failure__ is not only output when there is an error (previously always output)
- If the emit function is ommitted, the output now defaults to 'decrypted' as the field name

Version 2.3.2
- Fork of version 2.3.1 of Decryt from SplunkBase (under MIT license)
- Updated python SDK to 1.6.15
- default.meta file now includes read * and write to admin, power
- Created README.md file

DECRYPT is a set of Splunk commands which provide Base32, Base64, XOR, ROTX, RC4 and ROL/ROR routines which are commonly used for obfuscating malware communications and data exfiltration.

These commands can be leveraged in Splunk queries by users or automation to decipher previously indexed communications.

Version 2.3.2
May 29, 2021

This is a fork of the DECRYPT app by Michael Zalewski which is now archived

Version 2.3.2
- Fork of version 2.3.1 of Decryt from SplunkBase (under MIT license)
- Updated python SDK to 1.6.15
- default.meta file now includes read * and write to admin, power
- Created README.md file

DECRYPT is a set of Splunk commands which provide Base32, Base64, XOR, ROTX, RC4 and ROL/ROR routines which are commonly used for obfuscating malware communications and data exfiltration.

These commands can be leveraged in Splunk queries by users or automation to decipher previously indexed communications.


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