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88 lines
3.6 KiB
88 lines
3.6 KiB
# secure-json-parse
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[](https://dev.azure.com/fastify/fastify/_build/latest?definitionId=8&branchName=master) [](http://standardjs.com/)
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`JSON.parse()` drop-in replacement with prototype poisoning protection.
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## Introduction
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Consider this:
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```js
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> const a = '{"__proto__":{ "b":5}}';
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'{"__proto__":{ "b":5}}'
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> const b = JSON.parse(a);
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{ __proto__: { b: 5 } }
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> b.b;
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undefined
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> const c = Object.assign({}, b);
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{}
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> c.b
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5
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```
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The problem is that `JSON.parse()` retains the `__proto__` property as a plain object key. By
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itself, this is not a security issue. However, as soon as that object is assigned to another or
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iterated on and values copied, the `__proto__` property leaks and becomes the object's prototype.
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## Install
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```
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npm install secure-json-parse
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```
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## Usage
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Pass the option object as a second (or third) parameter for configuring the action to take in case of a bad JSON, if nothing is configured, the default is to throw a `SyntaxError`.<br/>
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You can choose which action to perform in case `__proto__` is present, and in case `constructor` is present.
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```js
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const sjson = require('secure-json-parse')
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const goodJson = '{ "a": 5, "b": 6 }'
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const badJson = '{ "a": 5, "b": 6, "__proto__": { "x": 7 }, "constructor": {"prototype": {"bar": "baz"} } }'
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console.log(JSON.parse(goodJson), sjson.parse(goodJson, { protoAction: 'remove', constructorAction: 'remove' }))
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console.log(JSON.parse(badJson), sjson.parse(badJson, { protoAction: 'remove', constructorAction: 'remove' }))
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```
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## API
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### `sjson.parse(text, [reviver], [options])`
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Parses a given JSON-formatted text into an object where:
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- `text` - the JSON text string.
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- `reviver` - the `JSON.parse()` optional `reviver` argument.
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- `options` - optional configuration object where:
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- `protoAction` - optional string with one of:
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- `'error'` - throw a `SyntaxError` when a `__proto__` key is found. This is the default value.
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- `'remove'` - deletes any `__proto__` keys from the result object.
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- `'ignore'` - skips all validation (same as calling `JSON.parse()` directly).
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- `constructorAction` - optional string with one of:
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- `'error'` - throw a `SyntaxError` when a `constructor` key is found. This is the default value.
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- `'remove'` - deletes any `constructor` keys from the result object.
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- `'ignore'` - skips all validation (same as calling `JSON.parse()` directly).
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### `sjson.scan(obj, [options])`
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Scans a given object for prototype properties where:
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- `obj` - the object being scanned.
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- `options` - optional configuration object where:
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- `protoAction` - optional string with one of:
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- `'error'` - throw a `SyntaxError` when a `__proto__` key is found. This is the default value.
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- `'remove'` - deletes any `__proto__` keys from the input `obj`.
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- `constructorAction` - optional string with one of:
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- `'error'` - throw a `SyntaxError` when a `constructor` key is found. This is the default value.
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- `'remove'` - deletes any `constructor` keys from the input `obj`.
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# Acknowledgements
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This project has been forked from [hapijs/bourne](https://github.com/hapijs/bourne).
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All the credits before the commit [4690682](https://github.com/hapijs/bourne/commit/4690682c6cdaa06590da7b2485d5df91c09da889) goes to the hapijs/bourne project contributors.
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After, the project will be maintained by the Fastify team.
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# License
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Licensed under BSD-3-Clause.
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