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A verification library for COVID-19 Vaccine Passes in New Zealand

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# NZCP.js &emsp; [![latest version badge]][npm] [![license badge]][license] [![downloads badge]][npm]

[latest version badge]: https://img.shields.io/npm/v/@vaxxnz/nzcp
[license badge]: https://img.shields.io/npm/l/@vaxxnz/nzcp
[downloads badge]: https://img.shields.io/npm/dw/@vaxxnz/nzcp
[npm]: https://www.npmjs.com/package/@vaxxnz/nzcp
[license]: https://github.com/vaxxnz/nzcp-js/blob/main/LICENSE

A JavaScript implementation of [NZ COVID Pass](https://github.com/minhealthnz/nzcovidpass-spec) verification, New Zealand's proof of COVID-19 vaccination solution, written in TypeScript. All contributions welcome 🥳

We also have a [Rust implementation](https://github.com/vaxxnz/nzcp-rust/) available.

> This library can be used for both in browser and Node.js.

## Install

```bash
# NPM
npm i @vaxxnz/nzcp

# Yarn
yarn add @vaxxnz/nzcp
```

## Projects

This library is current used in

- [Vaxxed.as](https://vaxxed.as) An offline NZ COVID Pass verifier by @rafcontreras
- [Hello Club](https://helloclub.com) A club and member management platform with self verification of vaccination status

## Demo

- [Node.js demo on REPL.it](https://replit.com/@noway1/NZCPjs-demo)
- [React.js demo on CodeSandbox](https://codesandbox.io/s/nzcpjs-demo-4vjgb)

## Usage

### Online

```javascript
import { verifyPassURI } from "@vaxxnz/nzcp";

// Verify a live New Zealand COVID-19 Pass, resolving the DID document
const result = await verifyPassURI("NZCP:/1/2KCEVIQEIVVWK6...");
```

### Offline

```javascript
import { verifyPassURIOffline } from "@vaxxnz/nzcp";

// Verify a live New Zealand COVID-19 Pass, using a prefetched DID document
const result = verifyPassURIOffline("NZCP:/1/2KCEVIQEIVVWK6...");
```

### Successful Verification

On **successful** verification of the given pass, the `verifyPassURI` method returns the following result:

```javascript
{
  "success": true,                       // Verification Outcome
  "violates": null,                      // Error object if code is invalid
  "expires": 2031-11-02T20:05:30.000Z,   // Expiration date
  "validFrom": 2021-11-02T20:05:30.000Z, // Date when pass becomes valid
  "credentialSubject": {                 // Pass holder's details
    "givenName": "Emily",                // Pass holder's given name
    "familyName": "Example",             // Pass holder's family name
    "dob": "1970-01-01"                  // Pass holder's date of birth
  },           
  "raw": {                               // raw data returned by CWTClaims
    "jti": "urn:uuid:...",
    "iss": "did:web:nzcp.identity.health.nz",
    "nbf": 1635883530,
    "exp": 1951416330,
    "vc": {
      '@context': [ ... ],
      "version": '1.0.0',
      "type": [ ... ],
      "credentialSubject": { ... }
    }
  }
}
```

### Unsuccessful Verification

On **unsuccessful** verification of the given pass, the `verifyPassURI` method returns the following result:

```javascript
{
  "success": false,           // Verification Outcome
  "violates": {               // Error information
    "message": "Error..",     // Friendly Error Message
    "section": "0.0",         // Section of official specs under violation
    "link": "https://..",     // Link to specifications breached
    "description": "The QR.." // Simplified error message
  },
  "expires": null,            // Nothing due to error
  "validFrom": null,          // Nothing due to error
  "credentialSubject": null   // No pass holder data due to error
  "raw": null                 // No raw data due to error
}
```

### Advanced Usage

These examples show how to configure the library to supply your own trusted issuers or DID documents. This will allow you to use the library with the [example COVID Passes from the spec](https://nzcp.covid19.health.nz/#valid-worked-example).

The following example shows how to use the example trusted issuer for online verification:

```javascript
import { verifyPassURI, TRUSTED_ISSUERS } from "@vaxxnz/nzcp";

// Trusted issuer for the example COVID Passes
// "did:web:nzcp.covid19.health.nz"
const exampleTrustedIssuer = TRUSTED_ISSUERS.MOH_EXAMPLE;

// Alternatively you could supply a trusted issuer for live COVID Passes
// If you omit the trusted issuer, the library will use the live DID document
// "did:web:nzcp.identity.health.nz"
const liveTrustedIssuer = TRUSTED_ISSUERS.MOH_LIVE;

const result = await verifyPassURI(
  "NZCP:/1/2KCEVIQEIVVWK6...",            // COVID-19 Pass to be verified
  { trustedIssuer: exampleTrustedIssuer } // Supply your own trusted issuer to overwrite the default
);
```

The following example shows how use the example DID document for offline verification:

```javascript
import { verifyPassURIOffline, DID_DOCUMENTS } from "@vaxxnz/nzcp";

// DID Document for the example COVID Passes
// Prefetched version of https://nzcp.covid19.health.nz/.well-known/did.json
const exampleDIDDocument = DID_DOCUMENTS.MOH_EXAMPLE;

// Alternatively you could supply a DID document for live COVID Passes
// If you omit the DID Document, the library will use the live DID document
// Prefetched version of https://nzcp.identity.health.nz/.well-known/did.json
const liveTrustedIssuer = DID_DOCUMENTS.MOH_LIVE;

const result = verifyPassURIOffline(
  "NZCP:/1/2KCEVIQEIVVWK6...",          // COVID-19 Pass to be verified
  { didDocument: exampleDIDDocument }   // Supply your own DID document to overwrite the default
);
```

## Online VS Offline

Currently for a Node.js/React Native project we recomend using `verifyPassURI` and for a browser based application to use `verifyPassURIOffline`.

The difference between the `verifyPassURI` and `verifyPassURIOffline` interfaces is:
 - `verifyPassURI`: This will resolve the DID document (which contains the Ministry of Health public key) from the web according to https://nzcp.covid19.health.nz/#ref:DID-CORE and then validate the DID document is from the MoH trusted issuer.
 - `verifyPassURIOffline`: This will use a prefetched version of https://nzcp.identity.health.nz/.well-known/did.json to verify against

There is a CORS policy on https://nzcp.identity.health.nz/.well-known/did.json which makes it currently unable to be fetched from the browser. The only option for browser based verifiers is currently to use the `verifyPassURIOffline` function. The Ministry Of Health is aware of this issue and is working to resolve it.

Offline scanners or scanners opperating in poor network conditions will also need to use `verifyPassURIOffline`. Since `verifyPassURI` requires an Internet connection to resolve the DID document.

NZCP.js has decided to support both use cases but which one to use is a decision that the user of this library is in the best position to make. If you have a network connection and want to be completely correct (and to specification) use `verifyPassURI`. If you want speed, don't have a network connection or don't mind using a prefetched DID document, use `verifyPassURIOffline`.

If you want to supply your own trusted issuer or DID document parameters, you can follow the Advanced Usage guide above.

## React Native

The library runs well with a few polyfills. An example of which polyfills you might have to set up [can be found here](https://github.com/vaxxnz/nzcp-js/issues/2#issuecomment-972808289).

## Support

See something that can be improved? [Report an Issue](https://github.com/vaxxnz/nzcp-js/issues) or contact us to [report a security concern](mailto:info@vaxx.nz).

Want to help us build a better library? We welcome contributions via [pull requests](https://github.com/vaxxnz/nzcp-js/pulls) and welcome you to our wider [Vaxx.nz](https://vaxx.nz) community on Discord: [Join our Discord community](https://discord.gg/nkbnqhR8A8).

---

## NPM

[@vaxxnz/nzcp](https://www.npmjs.com/package/@vaxxnz/nzcp)

## Contribute

```bash
# Install dependencies
yarn install
```

```bash
# Use developer scripts
yarn lint
yarn build-all
```

## Run tests
- Create `.env` in the root directory of the project
  - see `.env.example` for an example.
- Run `yarn test` or `yarn test-watch`

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