very fast object redaction
npm install fast-redactvery fast object redaction
By default, fast-redact serializes an object with JSON.stringify, censoring any
data at paths specified:
``jsoh oh we don't want this exposed in logs in etc.
const fastRedact = require('fast-redact')
const fauxRequest = {
headers: {
host: 'http://example.com',
cookie: ,if we're cool maybe we'll even redact this
referer: ,192.168.0.1
// Note: headers often contain hyphens and require bracket notation
'X-Forwarded-For':
}
}
const redact = fastRedact({
paths: ['headers.cookie', 'headers.referer', 'headers["X-Forwarded-For"]']
})
console.log(redact(fauxRequest))
// {"headers":{"host":"http://example.com","cookie":"[REDACTED]","referer":"[REDACTED]","X-Forwarded-For": "[REDACTED]"}}
`
When called without any options, or with a zero length paths array, fast-redact will return JSON.stringify or the serialize option, if set.
#### paths – Array
An array of strings describing the nested location of a key in an object.
The syntax follows that of the EcmaScript specification, that is any JavaScript
path is accepted – both bracket and dot notation is supported. For instance in
each of the following cases, the c property will be redacted: a.b.c,a['b'].c, a["b"].c, a[`b].c. Since bracket notation is supported, array indices are also
supported a[0].b would redact the b key in the first object of the a array.
Leading brackets are also allowed, for instance ["a"].b.c will work.
##### Wildcards
In addition to static paths, asterisk wildcards are also supported.
When an asterisk is place in the final position it will redact all keys within the
parent object. For instance a.b.* will redact all keys in the b object. Similarly
for arrays a.b[*] will redact all elements of an array (in truth it actually doesn't matter
whether b is in an object or array in either case, both notation styles will work).
When an asterisk is in an intermediate or first position, the paths following the asterisk will
be redacted for every object within the parent.
For example:
``js`
const fastRedact = require('fast-redact')
const redact = fastRedact({paths: ['*.c.d']})
const obj = {
x: {c: {d: 'hide me', e: 'leave me be'}},
y: {c: {d: 'and me', f: 'I want to live'}},
z: {c: {d: 'and also I', g: 'I want to run in a stream'}}
}
console.log(redact(obj))
// {"x":{"c":{"d":"[REDACTED]","e":"leave me be"}},"y":{"c":{"d":"[REDACTED]","f":"I want to live"}},"z":{"c":{"d":"[REDACTED]","g":"I want to run in a stream"}}}
Another example with a nested array:
`js`
const fastRedact = require('..')
const redact = fastRedact({paths: ['a[*].c.d']})
const obj = {
a: [
{c: {d: 'hide me', e: 'leave me be'}},
{c: {d: 'and me', f: 'I want to live'}},
{c: {d: 'and also I', g: 'I want to run in a stream'}}
]
}
console.log(redact(obj))
// {"a":[{"c":{"d":"[REDACTED]","e":"leave me be"}},{"c":{"d":"[REDACTED]","f":"I want to live"}},{"c":{"d":"[REDACTED]","g":"I want to run in a stream"}}]}
#### remove - Boolean - [false]
The remove option, when set to true will cause keys to be removed from the
serialized output.
Since the implementation exploits the fact that undefined keys are ignoredJSON.stringify
by the remove option may only be used when JSON.stringify
is the serializer (this is the default) – otherwise will throw.
If supplying a custom serializer that has the same behavior (removing keys
with undefined values), this restriction can be bypassed by explicitly setting censor
the to undefined.
#### censor – – ('[REDACTED]')
This is the value which overwrites redacted properties.
Setting censor to undefined will cause properties to removed as long as this is serializer
the behavior of the – which defaults to JSON.stringify, which does undefined
remove properties.
Setting censor to a function will cause fast-redact to invoke it with the original censor
value. The output of the function sets the redacted value.
Please note that asynchronous functions are not supported.
#### serialize – Function | Boolean – (JSON.stringify)
The serialize option may either be a function or a boolean. If a function is supplied, thisserialize
will be used to the redacted object. It's important to understand that for fast-redact
performance reasons mutates the original object, then serializes, then
restores the original values. So the object passed to the serializer is the exact same
object passed to the redacting function.
The serialize option as a function example:
`js`
const fastRedact = require('fast-redact')
const redact = fastRedact({
paths: ['a'],
serialize: (o) => JSON.stringify(o, 0, 2)
})
console.log(redact({a: 1, b: 2}))
// {
// "a": "[REDACTED]",
// "b": 2
// }
For advanced usage the serialize option can be set to false. When serialize is set to false,restore
instead of the serialized object, the output of the redactor function will be the mutated object
itself (this is the exact same as the object passed in). In addition a method is supplied
on the redactor function allowing the redacted keys to be restored with the original data.
`js`
const fastRedact = require('fast-redact')
const redact = fastRedact({
paths: ['a'],
serialize: false
})
const o = {a: 1, b: 2}
console.log(redact(o) === o) // true
console.log(o) // { a: '[REDACTED]', b: 2 }
console.log(redact.restore(o) === o) // true
console.log(o) // { a: 1, b: 2 }
#### strict – Boolean - [true]
The option, when set to true, will cause the redactor function to throw if instead strict
of an object it finds a primitive. When is set to false, the redactor function JSON.stringify
will treat the primitive value as having already been redacted, and return it serialized (with or the user's custom serialize function), or as-is if the serialize option
was set to false.
In order to achieve lowest cost/highest performance redaction fast-redact
creates and compiles a function (using the constructor) on initialization.
It's important to distinguish this from the dangers of a runtime eval, no user input
is involved in creating the string that compiles into the function. This is as safe
as writing code normally and having it compiled by V8 in the usual way.
Thanks to changes in V8 in recent years, state can be injected into compiled functions
using bind at very low cost (whereas bind used to be expensive, and getting state
into a compiled function by any means was difficult without a performance penalty).
For static paths, this function simply checks that the path exists and then overwrites
with the censor. Wildcard paths are processed with normal functions that iterate over
the object redacting values as necessary.
It's important to note, that the original object is mutated – for performance reasons
a copy is not made. See rfdc (Really Fast
Deep Clone) for the fastest known way to clone – it's not nearly close enough in speed
to editing the original object, serializing and then restoring values.
A restore function is also created and compiled to put the original state back on
to the object after redaction. This means that in the default usage case, the operation
is essentially atomic - the object is mutated, serialized and restored internally which
avoids any state management issues.
As mentioned in approach, the paths array input is dynamically compiled into a functionpaths
at initialization time. While the array is vigourously tested for any developer paths
errors, it's strongly recommended against allowing user input to directly supply any
paths to redact. It can't be guaranteed that allowing user input for couldn't
feasibly expose an attack vector.
The fastest known predecessor to fast-redact is the non-generic pino-noir
library (which was also written by myself).
In the direct calling case, fast-redact is ~30x faster than pino-noir, however a more realisticJSON.stringify
comparison is overhead on .
For a static redaction case (no wildcards) pino-noir adds ~25% overhead on top of JSON.stringify
whereas adds ~1% overhead.
In the basic last-position wildcard case,fast-redact is ~12% faster than pino-noir.
The pino-noir module does not support intermediate wildcards, but fast-redact does,JSON.stringify
the cost of an intermediate wildcard that results in two keys over two nested objects
being redacted is about 25% overhead on . The cost of an intermediate JSON.stringify
wildcard that results in four keys across two objects being redacted is about 55% overhead
on and ~50% more expensive that explicitly declaring the keys.
`sh`
npm run bench
`
benchNoirV2*500: 59.108ms
benchFastRedact*500: 2.483ms
benchFastRedactRestore*500: 10.904ms
benchNoirV2Wild*500: 91.399ms
benchFastRedactWild*500: 21.200ms
benchFastRedactWildRestore*500: 27.304ms
benchFastRedactIntermediateWild*500: 92.304ms
benchFastRedactIntermediateWildRestore*500: 107.047ms
benchJSONStringify*500: 210.573ms
benchNoirV2Serialize*500: 281.148ms
benchFastRedactSerialize*500: 215.845ms
benchNoirV2WildSerialize*500: 281.168ms
benchFastRedactWildSerialize*500: 247.140ms
benchFastRedactIntermediateWildSerialize*500: 333.722ms
benchFastRedactIntermediateWildMatchWildOutcomeSerialize*500: 463.667ms
benchFastRedactStaticMatchWildOutcomeSerialize*500: 239.293ms
`
npm test
`
224 passing (499.544ms)
`
npm run cov
`
-----------------|----------|----------|----------|----------|-------------------|
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s |
-----------------|----------|----------|----------|----------|-------------------|
All files | 100 | 100 | 100 | 100 | |
fast-redact | 100 | 100 | 100 | 100 | |
index.js | 100 | 100 | 100 | 100 | |
fast-redact/lib | 100 | 100 | 100 | 100 | |
modifiers.js | 100 | 100 | 100 | 100 | |
parse.js | 100 | 100 | 100 | 100 | |
redactor.js | 100 | 100 | 100 | 100 | |
restorer.js | 100 | 100 | 100 | 100 | |
rx.js | 100 | 100 | 100 | 100 | |
state.js | 100 | 100 | 100 | 100 | |
validator.js | 100 | 100 | 100 | 100 | |
-----------------|----------|----------|----------|----------|-------------------|
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