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feat(docs): Authwit how tos #6220

Merged
merged 16 commits into from
May 21, 2024
4 changes: 2 additions & 2 deletions docs/docs/aztec/concepts/accounts/authwit.md
Original file line number Diff line number Diff line change
Expand Up @@ -178,7 +178,7 @@ For the transfer, this could be done simply by appending a nonce to the argument
action = H(defi, token, transfer_selector, H(alice_account, defi, 1000, nonce));
```

Beware that the account contract will be unable to emit the nullifier since it is checked with a static call, so the calling contract must do it. This is similar to nonces in ERC20 tokens today. We provide a small library that handles this which we will see in the [developer documentation](guides/smart_contracts/writing_contracts/common_patterns/authwit.md).
Beware that the account contract will be unable to emit the nullifier since it is checked with a static call, so the calling contract must do it. This is similar to nonces in ERC20 tokens today. We provide a small library that handles this which we will see in the [developer documentation](../../../guides/smart_contracts/writing_contracts/authwit.md).

### Differences to approval

Expand All @@ -192,4 +192,4 @@ We don't need to limit ourselves to the `transfer` function, we can use the same

### Next Steps

Check out the [developer documentation](guides/smart_contracts/writing_contracts/common_patterns/authwit.md) to see how to implement this in your own contracts.
Check out the [developer documentation](../../../guides/smart_contracts/writing_contracts/authwit.md) to see how to implement this in your own contracts.
121 changes: 121 additions & 0 deletions docs/docs/guides/js_apps/authwit.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,121 @@
---
title: How to use authentication witnesses (authwit)
---

This page assumes you have authwit set up correctly in your contract. To learn how to do that, [go here](../smart_contracts/writing_contracts/authwit.md).

For an introduction to authentication witnesses on Aztec, [read this explainer](../../aztec/concepts/accounts/authwit.md).

## Import libraries

These are all the libraries you might need for using authwits in Aztec.js:

```typescript
import {
computeAuthWitMessageHash,
computeInnerAuthWitHash,
computeOuterAuthWitHash,
} from "@aztec/aztec.js";
```

You may not need all of these.

## Publicly deploy accounts

:::note
This is only required if you are using authwits in public
:::

If you are using public authwit (ie using `assert_current_call_valid_authwit_public` in your contract), you will need to deploy the following accounts publicly:

1. The account that is giving permission to an account to act on behalf of it (authwit giver)
2. The account that does the action (authwit receiver)

Here is an example implementation:

#include_code public_deploy_accounts yarn-project/end-to-end/src/fixtures/utils.ts typescript

You would then call this like so:

#include_code public_deploy_accounts yarn-project/end-to-end/src/e2e_authwit.test.ts typescript

## Define the action

When creating an authwit, you will need to pass the authwit giver, the authwit receiver (who will perform the action), and the action that is being authorized. The action can be a smart contract function call, or alternatively, arbitrary data.

### When the action is a function call

You can define the action like this:

#include_code authwit_computeAuthWitMessageHash yarn-project/end-to-end/src/e2e_blacklist_token_contract/transfer_private.test.ts typescript

In this example,

- `asset` refers to a token contract
- `withWallet(wallets[1])` is specifying the authwit receiver (`wallets[1]`) will do this action
- `.methods.transfer()` is specifying that the action is calling the `transfer` method on the token contract
- `(wallets[0].getAddress(), wallets[1].getAddress(), amount, nonce);` are the args of this method - it will send the `amount` from `wallets[0]` to `wallets[1]`

### Arbitrary message

You can hash your own authwit message by creating an inner hash with the data, like this:

#include_code compute_inner_authwit_hash yarn-project/end-to-end/src/e2e_authwit.test.ts typescript

Then create the outer hash by hashing the inner hash with the authwit receiver address, chainId, and version:

#include_code compute_outer_authwit_hash yarn-project/end-to-end/src/e2e_authwit.test.ts typescript

## Create the authwit

There are slightly different interfaces depending on whether your contract is checking the authwit in private or public.

Public authwits are stored in the account contract and batched with the authwit action call, so a user must send a transaction to update their account contract, authorizing an action before the authorized contract's public call will succeed.

Private execution uses oracles and are executed locally by the PXE, so the authwit needs to be created by the authwit giver and then added to the authwit receiver's PXE.

### Private

This is expected to be used alongside [private authwits in Aztec.nr contract](../smart_contracts/writing_contracts/authwit.md#private-functions).

Create a private authwit like this:

#include_code create_authwit yarn-project/end-to-end/src/e2e_blacklist_token_contract/transfer_private.test.ts typescript

In this example,

- `wallets[0]` is the authwit giver
- `wallets[1]` is the authwit reciever and caller of the function
- `action` was [defined previously](#define-the-action)

If you created an artbitrary message, you can create the authwit by replacing these params with the outer hash:
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Just curious what some use cases of creating authwits for arbitrary messages would be. Should we add some examples here or in another doc?

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i can't think of any myself. it's a comment in the codebase here

* in case the message is not a "call" to a function, but arbitrary data.

have asked jan


#include_code compute_outer_authwit_hash yarn-project/end-to-end/src/e2e_authwit.test.ts typescript

Then add it to the wallet of the authwit receiver (the caller of the function):

#include_code add_authwit yarn-project/end-to-end/src/e2e_blacklist_token_contract/transfer_private.test.ts typescript

### Public

This is expected to be used alongside [public authwits in Aztec.nr contract](../smart_contracts/writing_contracts/authwit.md#public-functions).

Set a public authwit like this:

#include_code set_public_authwit yarn-project/end-to-end/src/e2e_blacklist_token_contract/transfer_public.test.ts typescript

Remember it is a transaction and calls a method in the account contract. In this example,

- `wallets[0]` is the authwit giver
- `wallets[1]` is the authwit reciever and caller of the function
- `action` was [defined previously](#define-the-action)
- `true` sets the `authorized` boolean (`false` would revoke this authwit)

If you created an arbitrary message, you would replace the first param struct with the outer hash:

#include_code set_public_authwit yarn-project/end-to-end/src/e2e_authwit.test.ts typescript

## Further reading

- [An explainer of authentication witnesses](../../aztec/concepts/accounts/authwit.md)
- [Authwits in Aztec.nr](../smart_contracts/writing_contracts/authwit.md)
Original file line number Diff line number Diff line change
Expand Up @@ -3,15 +3,19 @@ title: Authentication Witness
description: Developer Documentation to use Authentication Witness for authentication actions on Aztec.
---

This page introduces the authwit library and how you can use it in your Aztec.nr smart contracts. [Skip to the usage](#usage).

For a guide on using authwit in Aztec.js, [read this](../../js_apps/authwit.md).

## Prerequisite reading

- [Authwit](guides/smart_contracts/writing_contracts/common_patterns/authwit.md)
- [Authwit](../../../aztec/concepts/accounts/authwit.md)

## Introduction

Authentication Witness is a scheme for authentication actions on Aztec, so users can allow third-parties (eg protocols or other users) to execute an action on their behalf.

How it works logically is explained in the [concepts](guides/smart_contracts/writing_contracts/common_patterns/authwit.md) but we will do a short recap here.
How it works logically is explained in the [concepts](../../../aztec/concepts/accounts/authwit.md) but we will do a short recap here.

An authentication witness is defined for a specific action, such as allowing a Defi protocol to transfer funds on behalf of the user. An action is here something that could be explained as `A is allowed to perform X operation on behalf of B` and we define it as a hash computed as such:

Expand Down Expand Up @@ -117,7 +121,7 @@ Very similar to the above, we have variations that work in the public domain. Th

## Usage

Ok, enough talking, how the hell do we use this?
Ok, enough talking, how do we use this?

### Importing it

Expand Down Expand Up @@ -151,6 +155,8 @@ Cool, so we have a function that checks if the current call is authenticated, bu

#include_code authwit_transfer_example /yarn-project/end-to-end/src/e2e_token_contract/transfer_private.test.ts typescript

Learn more about authwits in Aztec.js by [following this guide](../../js_apps/authwit.md).

### Public Functions

With private functions covered, how can we use this in a public function? Well, the answer is that we simply change one name of a function and then we are good to go :eyes: (almost).
Expand All @@ -163,7 +169,7 @@ With private functions covered, how can we use this in a public function? Well,

Authenticating an action in the public domain is quite similar to the private domain, with the difference that we are executing a function on the account contract to add the witness, if you recall, this is because we don't have access to the oracle in the public domain.

In the snippet below, this is done as a separate contract call, but can also be done as part of a batch as mentioned in the [Accounts concepts](guides/smart_contracts/writing_contracts/common_patterns/authwit.md#what-about-public).
In the snippet below, this is done as a separate contract call, but can also be done as part of a batch as mentioned in the [Accounts concepts](../../../aztec/concepts/accounts/authwit.md#what-about-public).

#include_code authwit_public_transfer_example /yarn-project/end-to-end/src/e2e_token_contract/transfer_public.test.ts typescript

Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ This is the core Aztec library that is required for every Aztec.nr smart contrac
authwit = { git="https://github.com/AztecProtocol/aztec-packages/", tag="#include_aztec_version", directory="noir-projects/aztec-nr/authwit"}
```

This allows you to use authentication witnesses in your contract. Find more about its usage [here](guides/smart_contracts/writing_contracts/common_patterns/authwit.md).
This allows you to use authentication witnesses in your contract. Find more about its usage [here](../../guides/smart_contracts/writing_contracts/authwit.md).

## Address note

Expand Down
13 changes: 10 additions & 3 deletions yarn-project/end-to-end/src/e2e_authwit.test.ts
Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,9 @@ describe('e2e_authwit_tests', () => {

beforeAll(async () => {
({ wallets } = await setup(2));
// docs:start:public_deploy_accounts
await publicDeployAccounts(wallets[0], wallets.slice(0, 2));
// docs:end:public_deploy_accounts

const nodeInfo = await wallets[0].getNodeInfo();
chainId = new Fr(nodeInfo.chainId);
Expand All @@ -28,10 +30,15 @@ describe('e2e_authwit_tests', () => {
describe('Private', () => {
describe('arbitrary data', () => {
it('happy path', async () => {
// docs:start:compute_inner_authwit_hash
const innerHash = computeInnerAuthWitHash([Fr.fromString('0xdead')]);
// docs:end:compute_inner_authwit_hash
// docs:start:compute_outer_authwit_hash
const outerHash = computeOuterAuthWitHash(wallets[1].getAddress(), chainId, version, innerHash);

// docs:end:compute_outer_authwit_hash
// docs:start:create_authwit
const witness = await wallets[0].createAuthWit(outerHash);
// docs:end:create_authwit
await wallets[1].addAuthWitness(witness);

// Check that the authwit is valid in private for wallets[0]
Expand Down Expand Up @@ -186,14 +193,14 @@ describe('e2e_authwit_tests', () => {
it('happy path', async () => {
const innerHash = computeInnerAuthWitHash([Fr.fromString('0xdead'), Fr.fromString('0x01')]);
const outerHash = computeOuterAuthWitHash(wallets[1].getAddress(), chainId, version, innerHash);

expect(await wallets[0].lookupValidity(wallets[0].getAddress(), outerHash)).toEqual({
isValidInPrivate: false,
isValidInPublic: false,
});

// docs:start:set_public_authwit
await wallets[0].setPublicAuthWit(outerHash, true).send().wait();

// docs:end:set_public_authwit
expect(await wallets[0].lookupValidity(wallets[0].getAddress(), outerHash)).toEqual({
isValidInPrivate: false,
isValidInPublic: true,
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -54,9 +54,12 @@ describe('e2e_blacklist_token_contract transfer private', () => {
.withWallet(wallets[1])
.methods.transfer(wallets[0].getAddress(), wallets[1].getAddress(), amount, nonce);
// docs:end:authwit_computeAuthWitMessageHash

// docs:start:create_authwit
const witness = await wallets[0].createAuthWit({ caller: wallets[1].getAddress(), action });
// docs:end:create_authwit
// docs:start:add_authwit
await wallets[1].addAuthWitness(witness);
// docs:end:add_authwit
// docs:end:authwit_transfer_example

// Perform the transfer
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -112,8 +112,9 @@ describe('e2e_blacklist_token_contract transfer public', () => {
.methods.transfer_public(wallets[0].getAddress(), wallets[1].getAddress(), amount, nonce);

// We need to compute the message we want to sign and add it to the wallet as approved
// docs:start:set_public_authwit
await wallets[0].setPublicAuthWit({ caller: wallets[1].getAddress(), action }, true).send().wait();

// docs:end:set_public_authwit
// Perform the transfer
await expect(action.prove()).rejects.toThrow(U128_UNDERFLOW_ERROR);

Expand Down Expand Up @@ -154,7 +155,6 @@ describe('e2e_blacklist_token_contract transfer public', () => {
.withWallet(wallets[1])
.methods.transfer_public(wallets[0].getAddress(), wallets[1].getAddress(), amount, nonce);
await wallets[0].setPublicAuthWit({ caller: wallets[0].getAddress(), action }, true).send().wait();

// Perform the transfer
await expect(action.prove()).rejects.toThrow('Assertion failed: Message not authorized by account');

Expand Down
3 changes: 3 additions & 0 deletions yarn-project/end-to-end/src/fixtures/utils.ts
Original file line number Diff line number Diff line change
Expand Up @@ -443,6 +443,8 @@ export async function setup(
* @param sender - Wallet to send the deployment tx.
* @param accountsToDeploy - Which accounts to publicly deploy.
*/

// docs:start:public_deploy_accounts
export async function publicDeployAccounts(sender: Wallet, accountsToDeploy: Wallet[]) {
const accountAddressesToDeploy = accountsToDeploy.map(a => a.getAddress());
const instances = await Promise.all(accountAddressesToDeploy.map(account => sender.getContractInstance(account)));
Expand All @@ -452,6 +454,7 @@ export async function publicDeployAccounts(sender: Wallet, accountsToDeploy: Wal
]);
await batch.send().wait();
}
// docs:end:public_deploy_accounts

/**
* Sets the timestamp of the next block.
Expand Down
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