Logchain NPM | npm.io

Logchain

Logging secured by 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 easily extensible by simply deriving from Basic.

Usage

Install

npm 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

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

Init once in main

import { LogChainer } from "logchain"

// Initialize a default chainer.
const chainer = new LogChainer()

// Register the formatter to the logger.
chainer.initLogging()

Have a look at the comprehensive guide of constructor parameters.

Use everywhere with standard logging

Standard console methods are overriden once per program.

console.log("the basic log")
console.debug("the debug")
console.info("the info")
console.warn("the warning")
console.error("the error")

Check your logs integrity afterwards

import { LogChainer } from "logchain"

const aLogChain = [
	"2020-06-03T22:00:17.566Z LOG basicChaining.test.js:28 the basic log |43d85615af018369",
	"2020-06-03T22:00:17.567Z DEBU basicChaining.test.js:29 the debug |2cdcac6830d7d094",
	"2020-06-03T22:00:17.568Z INFO basicChaining.test.js:30 the info |72f847d26583d23d",
	"2020-06-03T22:00:17.568Z WARN basicChaining.test.js:31 the warning |095e94f80e612f95",
	"2020-06-03T22:00:17.569Z ERRO basicChaining.test.js:32 the error |618c0f4dd07a3942"
]

const chainer = new LogChainer({secret: "9b06b72c717e8d9f8c1393e11f2635c5"})
const result = chainer.verify(aLogChain)

if(result.value)
{
	console.log("All right")
}
else
{
	console.log("Last good line", result.prevLine)
	console.log("First bad line", result.line)
}

Constructor parameters

They are passed as an object.

import { LogChainer } from "logchain"

const chainer = new LogChainer({verbosity: 3, secret: "mySignatureKey"})

Param Type	Default value	Description
formatterCls class	formatters.Basic	Type of logging to perform, raw text, json, custom
template string	see below	Placeholder string used by raw-text loggers
secret string	random of 128 chars	Signature key to compute the line signature
seed string	random of 64 chars	Random string to sign into the first log line
stream stream	stdout	Where the logs are sent, file/console/custom stream
verbosity int	0	Number 0..5 mapped to a logging.level

Logchain record logging fields

We make the record with some handy fields:

Name	Description
fileLine	Widespread `filename:lineno`
levelLetter	First letter of the logging level names
msg	The text being logged
process	The PID as int
processName	The process name
signature	The digital signature of the previous line. Include it in all your lines to benefit from the chaining
timestamp	ISO8601 precise to the milliseconds