Add encryptCallData() to gasless chapter and example

docs/gasless.md

@@ -19,9 +19,9 @@ recipient contract decodes the meta-transaction, verifies both signatures and
 executes the original transaction.
 
 Oasis Sapphire supports two transaction relaying methods: The **on-chain
-signer** exposes the Oasis-specific contract state encryption functionality
-while the **gas station network** method is a standardized approach known in
-other blockchains as well.
+signer** is trustless and utilizes the Oasis-specific contract state encryption
+while the **gas station network** service is known from other blockchains as
+well.
 
 :::caution
 
@@ -34,11 +34,15 @@ features such as the browser support are not fully implemented yet.
 
 ## On-Chain Signer
 
-The on-chain signer is a smart contract which receives the user's transaction,
-checks whether the transaction is valid, wraps it into a meta-transaction
-(which includes paying for the transaction fee) and returns it back to the user
-in [EIP-155] format. These steps are executed as a confidential call. Finally,
-the user submits the generated transaction to the network.
+The on-chain signer is a smart contract which:
+1. receives the user's transaction,
+2. checks whether the transaction is valid,
+3. wraps it into a meta-transaction (which includes paying for the transaction
+   fee) and
+4. returns it back to the user in the [EIP-155] format.
+
+The steps above are executed as a confidential read-only call. Finally, the user
+then submits the obtained transaction to the network.
 
 ![Diagram of the On-Chain Signing](images/gasless-on-chain-signer.svg)
 
@@ -77,7 +81,8 @@ private key containing enough balance to cover transaction fees should be
 provided in the constructor.
 
 ```solidity
-import {EIP155Signer} from "@oasisprotocol/sapphire-contracts/contracts/EIP155Signer.sol";
+import { encryptCallData } from "@oasisprotocol/sapphire-contracts/contracts/CalldataEncryption.sol";
+import { EIP155Signer } from "@oasisprotocol/sapphire-contracts/contracts/EIP155Signer.sol";
 
 struct EthereumKeypair {
   address addr;
@@ -121,7 +126,7 @@ contract Gasless {
           gasLimit: 250000,
           to: address(this),
           value: 0,
-          data: abi.encodeCall(this.proxy, data),
+          data: encryptCallData(abi.encodeCall(this.proxy, data)),
           chainId: block.chainid
         })
       );
@@ -214,9 +219,15 @@ you must consider the following:
 
 #### Confidentiality
 
-Both the inner- and the meta-transaction are stored on-chain unencrypted. Use
-`Sapphire.encrypt()` and `Sapphire.decrypt()` call on the inner-transaction with
-an encryption key generated and stored inside a confidential contract state.
+The [`encryptCallData()`] helper above will generate an ephemeral key and encrypt
+the transaction's calldata. Omit this call to generate a plain transaction. You
+can also explicitly encrypt specific function arguments of the inner-transaction
+by calling [`Sapphire.encrypt()`] using a private key stored somewhere in your
+smart contract and then [`Sapphire.decrypt()`] when executing the transaction.
+
+[`encryptCallData()`]: https://api.docs.oasis.io/sol/sapphire-contracts/contracts/CalldataEncryption.sol/function.encryptCallData.html#encryptcalldatabytes
+[`Sapphire.encrypt()`]: https://api.docs.oasis.io/sol/sapphire-contracts/contracts/Sapphire.sol/library.Sapphire.html#encrypt-1
+[`Sapphire.decrypt()`]: https://api.docs.oasis.io/sol/sapphire-contracts/contracts/Sapphire.sol/library.Sapphire.html#decrypt-1
 
 #### Gas Cost and Gas Limit
 

examples/onchain-signer/contracts/Gasless.sol

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.8.19;
+pragma solidity ^0.8.20;
 
+import {encryptCallData} from "@oasisprotocol/sapphire-contracts/contracts/CalldataEncryption.sol";
 import {EIP155Signer} from "@oasisprotocol/sapphire-contracts/contracts/EIP155Signer.sol";
 
 struct EthereumKeypair {
@@ -25,8 +26,27 @@ contract Gasless {
         bytes memory innercall
     ) external view returns (bytes memory output) {
         bytes memory data = abi.encode(innercallAddr, innercall);
+        return
+            EIP155Signer.sign(
+                kp.addr,
+                kp.secret,
+                EIP155Signer.EthTx({
+                    nonce: kp.nonce,
+                    gasPrice: 100_000_000_000,
+                    gasLimit: 250000,
+                    to: address(this),
+                    value: 0,
+                    data: encryptCallData(abi.encodeCall(this.proxy, data)),
+                    chainId: block.chainid
+                })
+            );
+    }
 
-        // Call will invoke proxy().
+    function makeProxyTxPlain(
+        address innercallAddr,
+        bytes memory innercall
+    ) external view returns (bytes memory output) {
+        bytes memory data = abi.encode(innercallAddr, innercall);
         return
             EIP155Signer.sign(
                 kp.addr,

examples/onchain-signer/hardhat.config.ts

@@ -26,7 +26,17 @@ const config: HardhatUserConfig = {
     'sapphire-testnet': { ...sapphireTestnet, accounts },
     'sapphire-localnet': { ...sapphireLocalnet, accounts },
   },
-  solidity: '0.8.20',
+  solidity: {
+    version: '0.8.20',
+    settings: {
+      // XXX: Needs to match https://github.com/oasisprotocol/sapphire-paratime/blob/main/contracts/hardhat.config.ts
+      optimizer: {
+        enabled: true,
+        runs: (1 << 32) - 1,
+      },
+      viaIR: true,
+    },
+  },
 };
 
 export default config;

examples/onchain-signer/test/CommentBox.ts

@@ -1,4 +1,5 @@
 import { expect } from 'chai';
+import { Context } from 'mocha';
 import { ethers } from 'hardhat';
 import { parseEther, Wallet } from 'ethers';
 import { CommentBox, Gasless } from '../typechain-types';
@@ -33,55 +34,60 @@ describe('CommentBox', function () {
     console.log('    . gasless pubkey', wallet.address);
   });
 
-  it('Should comment', async function () {
-    this.timeout(10000);
+  async function commentGasless(comment: string, plain: boolean) {
+    const provider = ethers.provider;
+
+    const innercall = commentBox.interface.encodeFunctionData('comment', [
+      comment,
+    ]);
 
     const prevCommentCount = await commentBox.commentCount();
+    let tx: string;
+    if (plain) {
+      tx = await gasless.makeProxyTxPlain(
+        await commentBox.getAddress(),
+        innercall,
+      );
+    } else {
+      tx = await gasless.makeProxyTx(await commentBox.getAddress(), innercall);
+    }
 
-    const tx = await commentBox.comment('Hello, world!');
-    await tx.wait();
+    // TODO: https://github.com/oasisprotocol/sapphire-paratime/issues/179
+    const response = await provider.broadcastTransaction(tx);
+    await response.wait();
 
-    // Sapphire Mainnet/Testnet: Wait a few moments for nodes to catch up.
-    const chainId = (await ethers.provider.getNetwork()).chainId;
-    if (chainId == BigInt(23294) || chainId == BigInt(23295)) {
-      await new Promise((r) => setTimeout(r, 6_000));
-    }
+    const receipt = await provider.getTransactionReceipt(response.hash);
+    if (!receipt || receipt.status != 1) throw new Error('tx failed');
 
     expect(await commentBox.commentCount()).eq(prevCommentCount + BigInt(1));
-  });
+  }
+
+  it('Should comment', async function () {
+    const prevCommentCount = await commentBox.commentCount();
 
-  it('Should comment gasless', async function () {
-    this.timeout(10000);
+    const tx = await commentBox.comment('Hello, world!');
+    await tx.wait();
 
-    const provider = ethers.provider;
+    expect(await commentBox.commentCount()).eq(prevCommentCount + BigInt(1));
+  });
 
-    // You can set up sapphire-localnet image and run the test like this:
-    // docker run -it -p8545:8545 -p8546:8546 ghcr.io/oasisprotocol/sapphire-localnet -to 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
-    // npx hardhat test --grep proxy --network sapphire-localnet
-    const chainId = (await provider.getNetwork()).chainId;
-    if (chainId == BigInt(1337)) {
+  it('Should comment gasless (encrypted)', async function () {
+    // Set up sapphire-localnet image to run this test:
+    // docker run -it -p8544-8548:8544-8548 ghcr.io/oasisprotocol/sapphire-localnet
+    if ((await ethers.provider.getNetwork()).chainId == BigInt(1337)) {
       this.skip();
     }
 
-    const innercall = commentBox.interface.encodeFunctionData('comment', [
-      'Hello, free world!',
-    ]);
+    await commentGasless('Hello, c10l world', false);
+  });
 
-    // Sapphire Mainnet/Testnet: Wait a few moments for nodes to catch up.
-    if (chainId == BigInt(23294) || chainId == BigInt(23295)) {
-      await new Promise((r) => setTimeout(r, 6_000));
+  it('Should comment gasless (plain)', async function () {
+    // Set up sapphire-localnet image to run this test:
+    // docker run -it -p8544-8548:8544-8548 ghcr.io/oasisprotocol/sapphire-localnet
+    if ((await ethers.provider.getNetwork()).chainId == BigInt(1337)) {
+      this.skip();
     }
 
-    const tx = await gasless.makeProxyTx(
-      await commentBox.getAddress(),
-      innercall,
-    );
-
-    // TODO: https://github.com/oasisprotocol/sapphire-paratime/issues/179
-    const response = await provider.broadcastTransaction(tx);
-    await response.wait();
-
-    const receipt = await provider.getTransactionReceipt(response.hash);
-    if (!receipt || receipt.status != 1) throw new Error('tx failed');
+    await commentGasless('Hello, plain world', true);
   });
 });