Logchain

Python Logging based on blockchain 📜 ⛓️.

Logs get chained

The current log line contains the signature of the previous line with your secret.

• detect lines deleted / lost
• detect logs tampering

Philosophy

The package is intended to be a lightweight util for generating incorruptible logs.

For this pupose we rely as much as possible on standard packages: few dependencies, high quality.

The formatters are easy extensible by simply deriving from Basic.

Usage

Install

pip install logchain

Choose your log type

Many types of logs are supported out-of-the-box:

• Basic raw text, relying on the standard formatter
• Json structured log lines with static & dynamic fields
• CSV work in progress

You can write a custom formatter in 20-ish lines.

Init once in main

from logchain import LogChainer

# Initialize a default chainer.
theLogger = LogChainer()

# Register the formatter to the logger.
theLogger.initLogging()

Have a look at the comprehensive guide of constructor parameters.

Use everywhere with python logging module

import logging

logging.debug("My message")
logging.info("Some information")

Check your logs integrity afterwards

from logchain import LogChainer

aLogChain = [
	"2020-03-30 13:38:00.782|0ec90b9839fdd964|TestChaining.py:20 test_logging_happy_case hello gg",
	"2020-03-30 13:38:00.782|2e3f1b4a7b946fb1|TestChaining.py:21 test_logging_happy_case voila1",
	"2020-03-30 13:38:00.782|10d1ab606618492a|TestChaining.py:22 test_logging_happy_case voila2",
	"2020-03-30 13:38:00.782|805757e144f4e385|TestChaining.py:23 test_logging_happy_case voila5",
	"2020-03-30 13:38:00.782|3bda90b5af77d3fe|TestChaining.py:24 test_logging_happy_case voila4"
]
result = LogChainer.verify(aLogChain)

if not result:
	print("Last good line", result.prevLine)
	print("First bad line", result.line)
else:
	print("All right")

Constructor parameters

They are passed as a dict and/or named arguments.

from logchain import LogChainer

theLogger = LogChainer(verbosity = 3, secret = "mySignatureKey")

params = {"verbosity": 3, "secret": "mySignatureKey"}
theLogger = LogChainer(params, timestampFmt = "iso")

The default format is %(timestamp)s %(levelLetters)s %(fileLine)-15s %(funcName)-15s %(message)-60s |%(signature)s. It relies on some extra fields like the signature at its end.

Logchain extra logging fields

We enrich the standard logging record with some handy fields:

The timestamp field offers more flexibility than asctime in regards to:

• the precision; can go up to the micro seconds (msecs cannot)
• the decimal separator; you choose, '.' by default
• utc or local timezone
• customize the format only in one place: timestampFmt

Dynamic logging fields

The package is suitable for server/app logging which context changes from one transaction to another. Here is an example of setting contextual information throughout the lifecycle of an app:

App.py

class App:
	def __init__(self, appName, logger):
		self.logger = logger
		self.logger.setField(appName = appName)
		logging.info("Creating the app")

	def handleTransaction(self, userId, callback):
		with self.logger.managedField(uId = userId, trxId = secrets.token_urlsafe(8)):
			callback()

	def close(self):
		logging.info("Closing the app")

Callbacks.py

	# The log chain in transparent for the callbacks
	def callback1():
		logging.warn("Something happened")

	def callback2():
		logging.info("Serving a resource")

main.py

def main():
	theLogger = logchain.LogChainer(formatterCls = logchain.formatters.Json)
	theLogger.initLogging()

	app = App("MyApp", theLogger)
	app.handleTransaction("user1", callback1)
	app.handleTransaction("user1", callback2)
	app.close()

You can either use:

• setField: set a permanant field, remove it by setting it to None.
• managedField: set a temporary field for the scope of the context manager.

Contributing

Install

The code is hosted on Gitlab 🦊

Simply clone and submit pull requests.

Testing

The unit tests are located in the test folder which contains the __main__.py entrypoint.

# Run all
python test

# Get additional options
python test --help

Delivery

Use to the awesome Poetry tool for this purpose:

poetry build
poetry publish