Crate secure_json_parse 

Parse JSON while blocking prototype-poisoning keys.

This crate parses untrusted JSON and detects two key patterns that pollute a JavaScript object’s prototype once the parsed value is copied, merged, or iterated:

1. a key literally named __proto__
2. a key named constructor whose value is an object that contains a prototype key (a constructor.prototype nesting)

For each pattern you choose an Action: error out, remove the key, or ignore it and behave like a plain JSON parse. A safe flag turns any detected violation into Ok(None) instead of an error.

The parsed value is a serde_json::Value. In a Value tree __proto__ and constructor are ordinary map keys, so the danger is latent rather than immediate. The job here is to detect, remove, or reject those keys before the value reaches code that would treat them as a prototype.

Quick start

use secure_json_parse::{parse, Action, Options, Error};

// Default options error on a forbidden key.
let err = parse(r#"{"__proto__": {"x": 7}}"#, &Options::default());
assert!(matches!(err, Err(Error::ForbiddenProperty)));

// Remove the key instead.
let opts = Options::default().proto_action(Action::Remove);
let value = parse(r#"{"a": 5, "__proto__": {"x": 7}}"#, &opts).unwrap().unwrap();
assert_eq!(value, serde_json::json!({"a": 5}));

Safe parsing

safe_parse folds every outcome into one three-valued result:

use secure_json_parse::{safe_parse, SafeOutcome};

// Clean input parses to a value.
assert!(matches!(safe_parse(r#"{"a": 1}"#), SafeOutcome::Value(_)));
// A forbidden key yields Violation.
assert!(matches!(safe_parse(r#"{"__proto__": {}}"#), SafeOutcome::Violation));
// Malformed JSON yields Malformed.
assert!(matches!(safe_parse(r#"{"a": "#), SafeOutcome::Malformed));

Structs

Options

Configuration for parse, parse_bytes, and scan.

Enums

Action

What to do when a forbidden key is found.

Error

Why a parse failed.

SafeOutcome

The three outcomes of safe_parse.

Functions

parse

Parse JSON text and apply prototype-poisoning checks.

parse_bytes

Parse JSON bytes and apply prototype-poisoning checks.

safe_parse

Parse JSON text and fold every outcome into a SafeOutcome.

safe_parse_bytes

Parse JSON bytes and fold every outcome into a SafeOutcome.

scan

Walk a parsed value and apply the prototype-poisoning checks.