DECRYPT2
Overview
Details
DECRYPT is a set of Splunk commands which provide Base32, Base64, XOR, ROTX, RC4, ROL/ROR, hex, ascii, substr, decode (python codec), escape, unescape, htmlescape, htmlunescape, tr, rev, find, substr, slice, zlib_inflate, Base32 reverse endian, Base64 reverse endian, Base58 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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| /____ ___________ ___.__._______/ |
/ |/ _/ ____ < | |____ \ __\
/ // \ /\ _| | \/___ || |> > |
_ |_ >_ >| / ____|| /||
\/ \/ \/ \/ ||
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')
If the emit function is not mentioned, an emit('decrypted') is automatically added so the data is output
Note: Fields must be output via the emit function. The input field is not modified in place.
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.
Note: 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
hostnamefield tob64as input - Pass the output of
b64toxoras input with the argument's\x65cr\x65t' - Pass the output of
xortohexas input - Pass the output of
hextoemitwith the argument'decrypted', creating adecryptedfield
Functions
btoa()
Encodes input to a Base64 string.
b64(), atob()
Decodes a Base64 encoded string.
b32()
Decodes a Base32 encoded string.
b58()
Decodes a Base58 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. Set the count to 'null' to return from the start offset to the end of the input.
slice(start, end)
Returns a slice of the input, starting at start offset to the end offset. Set the end to 'null' to go to the end of the input.
decode('codec')
Returns a decoded version of the input based on the codec, python codec list is available on https://docs.python.org/3/library/codecs.html#standard-encodings
escape
Returns a string where control characters, \, and non-ASCII characters are backslash escaped (e.g. \x0a, \\, \x80).
unescape
Returns a string run through python unicode_escape (i.e. return the unicode point(s)). Reverses escape. Also unescapes Unicode codepoints (\uxxxx or \Uxxxxxxxx), which escape does not produce.
htmlescape
Returns a string with &, <, and > XML escaped like &.
htmlunescape
Returns a string with HTML references like > and > unescaped to >.
tr('from', 'to')
Takes an argument to translate "from" and an argument of characters to translate "to" and then returns a result with the result (similar to tr in Unix).
rev()
Returns the input in reverse order.
find('subseq', start)
Returns the index of a subsequence "subseq" starting at index "start", or -1 if the subsequence is not found.
b32re()
Returns a reverse-endian base32 decoded string, as used in the SunBurst DGA.
b64re()
Returns a reverse-endian base64 decoded string.
zlib_inflate()
Returns zlib.decompress() inflated bytes. The window size (wbits) must be provided.
Note: you must use single quotes around the strings.
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')
...
Reverse the data field
... | decrypt field=data rev
Find the index of a subsequence in a data field
... | decrypt field=data find('subseq', 0)
Decrypt SunBurst DGA with reverse endian base32
... | decrypt field=data tr('ph2eifo3n5utg1j8d94qrvbmk0sal76c', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567') b32re
Contributors
Shannon Davis (Splunk)
Steven (malvidin on github)
Release Notes
2.4.0
Merged pull request from Steven (malvidin on github)
This new version includes:
- Removal of python2 support
- Cleanup code formatting
- Remove unused COMMA handling
- Add slice function
Note that 2.3.14 will be the last version of decrypt2 supporting python2
2.3.14
Merged pull request from Steven (malvidin on github)
This new version includes:
- Improved handling of negative integers
- Update so xor doesn't accept negative integers
- substr now accepts a null as count to return to end of string
2.3.13
Merged pull request from Steven (malvidin on github)
This new version includes:
- Added zlib_inflate function
- Updated Splunk python SDK to 1.7.3
2.3.12
Merged pull request from Steven (malvidin on github)
This new version includes:
- A fix to base58 to deal with empty input
- A setting for slice length and max length on base58
2.3.11
Merged pull request from Steven (malvidin on github)
This new version includes:
- New base58 decode function (b58)
- Updated python SDK to 1.7.2
2.3.10
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)
2.3.9
Updated Splunk python SDK to 1.6.20
2.3.8
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
2.3.7
Merged pull request from Steven (malvidin on github)
- New rev function
- Decreased differences with python2
Updated Splunk python SDK to 1.6.19
2.3.6
Updated metdata file to include sc_admin role for Splunk Cloud
2.3.5
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
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 omitted, 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 2.4.3
Updated Splunk python SDK from 2.0.1 to 2.0.2 as per Splunk cloud compatibility requirements
Version 2.4.2
Updated python SDK to 2.0.1
Version 2.4.1
- Added support for null argument padding, so
find('decrypt2')is equivalent tofind('decrypt2', 0) - Added zlib_deflate for internal validation of zlib_inflate, which can also be used for information analysis
- Add basic entropy calculation
Version 2.4.0
Merged pull request from Steven (malvidin on github)
This new version includes:
- Removal of python2 support
- Cleanup code formatting
- Remove unused COMMA handling
- Add slice function
Note that 2.3.14 will be the last version of decrypt2 supporting python2
Version 2.3.14
Merged pull request from Steven (malvidin on github)
This new version includes:
- Improved handling of negative integers
- Update so xor doesn't accept negative integers
- substr now accepts a null as count to return to end of string
Version 2.3.13
Merged pull request from Steven (malvidin on github)
This new version includes:
Added zlib_inflate function
Updated Splunk python SDK to 1.7.3
Version 2.3.12
Merged pull request from Steven (malvidin on github)
This new version includes:
- A fix to base58 to deal with empty input
- A setting for slice length and max length on base58
Version 2.3.11
Merged pull request from Steven (malvidin on github)
This new version includes:
- New base58 decode function (b58)
- Updated python SDK to 1.7.2
Version 2.3.10
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
Updated Splunk python SDK to 1.6.20
Version 2.3.8
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
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
Updated the metadata file to include the sc_admin role
Version 2.3.5
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
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
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
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.