@gemini-wallet/core/src/utils/calculateWalletAddress.ts

Core SDK for Gemini Wallet integration with popup communication

import {
  type Address,
  encodeAbiParameters,
  encodeFunctionData,
  encodePacked,
  getCreate2Address,
  type Hex,
  keccak256,
} from "viem";

// WebAuthn validator data structure
export interface WebAuthnValidatorData {
  pubKeyX: bigint;
  pubKeyY: bigint;
}

// Parameters for calculating wallet address
export interface CalculateWalletAddressParams {
  publicKey: Hex; // Combined 64-byte hex string (32 bytes X + 32 bytes Y)
  credentialId: string; // Base64URL encoded credential ID
  index?: bigint; // Optional, defaults to 0
}

// Embedded contract addresses for Horizon deployment
const CONTRACT_ADDRESSES = {
  ACCOUNT_IMPLEMENTATION: "0x0006050168DE255a8672ACaD4821e721CBA44337" as const,
  ATTESTER: "0x000474392a9cd86a4687354f1Ce2964B52e97484" as const,
  BOOTSTRAPPER: "0x00000000D3254452a909E4eeD47455Af7E27C289" as const,
  FACTORY: "0x00E58DF70FaB983a324c4C068c82d20407579FaC" as const,
  REGISTRY: "0x000000000069E2a187AEFFb852bF3cCdC95151B2" as const,
  WEBAUTHN_VALIDATOR: "0xbA45a2BFb8De3D24cA9D7F1B551E14dFF5d690Fd" as const,
};

/**
 * Calculate smart wallet address from public key and credential ID
 * This handles all validation and setup internally
 */
export function calculateWalletAddress(
  params: CalculateWalletAddressParams,
): Address {
  const { publicKey, credentialId, index = 0n } = params;

  // Validate input
  if (!publicKey.startsWith("0x") || publicKey.length !== 130) {
    throw new Error(
      "Invalid public key: must be 64-byte hex string (0x + 128 chars)",
    );
  }

  // Extract X and Y coordinates
  const pubKeyX = `0x${publicKey.slice(2, 66)}` as Hex;
  const pubKeyY = `0x${publicKey.slice(66, 130)}` as Hex;

  // Convert to WebAuthnValidatorData
  const webAuthnData: WebAuthnValidatorData = {
    pubKeyX: BigInt(pubKeyX),
    pubKeyY: BigInt(pubKeyY),
  };

  // Validate the key is on the secp256r1 curve
  if (!validateWebAuthnKey(webAuthnData)) {
    throw new Error(
      "Invalid WebAuthn key: coordinates are not on secp256r1 curve",
    );
  }

  // Calculate authenticator ID hash from credential ID
  const authenticatorIdHash = generateAuthenticatorIdHash(credentialId);

  // Use the internal calculation with embedded addresses
  return calculateAddressInternal({
    authenticatorIdHash,
    index,
    webAuthnData,
  });
}

/**
 * Generate authenticator ID hash from credential ID
 */
export function generateAuthenticatorIdHash(credentialId: string): Hex {
  // Convert base64url to bytes
  const padding = "=".repeat((4 - (credentialId.length % 4)) % 4);
  const base64 = credentialId.replace(/-/g, "+").replace(/_/g, "/") + padding;

  const binaryString = atob(base64);
  const bytes = new Uint8Array(binaryString.length);
  for (let i = 0; i < binaryString.length; i++) {
    bytes[i] = binaryString.charCodeAt(i);
  }

  return keccak256(bytes);
}

/**
 * Validate WebAuthn public key offchain
 * Mirrors the contract's _validateWebAuthnKey function
 */
export function validateWebAuthnKey(
  webAuthnData: WebAuthnValidatorData,
): boolean {
  const SECP256R1_P =
    0xffffffff00000001000000000000000000000000ffffffffffffffffffffffffn;
  const SECP256R1_B =
    0x5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604bn;

  const { pubKeyX, pubKeyY } = webAuthnData;

  // Check if coordinates are valid
  if (
    pubKeyX === 0n ||
    pubKeyY === 0n ||
    pubKeyX >= SECP256R1_P ||
    pubKeyY >= SECP256R1_P
  ) {
    return false;
  }

  // Validate curve membership: Y² ≡ X³ - 3X + B (mod P)
  const ySquared = (pubKeyY * pubKeyY) % SECP256R1_P;
  const xCubed = (pubKeyX * pubKeyX * pubKeyX) % SECP256R1_P;
  const threeX = (3n * pubKeyX) % SECP256R1_P;
  const rightSide = (xCubed + SECP256R1_P - threeX + SECP256R1_B) % SECP256R1_P;

  return ySquared === rightSide;
}

/**
 * Internal calculation method using embedded contract addresses
 */
function calculateAddressInternal(params: {
  webAuthnData: WebAuthnValidatorData;
  authenticatorIdHash: Hex;
  index: bigint;
}): Address {
  const { webAuthnData, authenticatorIdHash, index } = params;

  // Use embedded contract addresses
  const factoryAddress = CONTRACT_ADDRESSES.FACTORY;
  const accountImplementation = CONTRACT_ADDRESSES.ACCOUNT_IMPLEMENTATION;
  const webAuthnValidator = CONTRACT_ADDRESSES.WEBAUTHN_VALIDATOR;
  const attester = CONTRACT_ADDRESSES.ATTESTER;
  const bootstrapper = CONTRACT_ADDRESSES.BOOTSTRAPPER;
  const registry = CONTRACT_ADDRESSES.REGISTRY;

  // Generate cross-chain consistent salt (same as contract)
  const salt = keccak256(
    encodePacked(
      ["uint256", "uint256", "bytes32", "uint256"],
      [webAuthnData.pubKeyX, webAuthnData.pubKeyY, authenticatorIdHash, index],
    ),
  );

  // Prepare validator initialization data (WebAuthnValidatorData + authenticatorIdHash)
  const validatorInitData = encodeAbiParameters(
    [
      {
        components: [
          { name: "pubKeyX", type: "uint256" },
          { name: "pubKeyY", type: "uint256" },
        ],
        type: "tuple",
      },
      { type: "bytes32" },
    ],
    [webAuthnData, authenticatorIdHash],
  );

  // Create RegistryConfig struct
  const registryConfig = {
    attesters: [attester],
    registry,
    threshold: 1n,
  };

  // Encode the bootstrap call
  const bootstrapCall = encodeFunctionData({
    abi: [
      {
        inputs: [
          { name: "validator", type: "address" },
          { name: "validatorInitData", type: "bytes" },
          {
            components: [
              { name: "registry", type: "address" },
              { name: "attesters", type: "address[]" },
              { name: "threshold", type: "uint8" },
            ],
            name: "registryConfig",
            type: "tuple",
          },
        ],
        name: "initNexusWithSingleValidator",
        type: "function",
      },
    ],
    args: [webAuthnValidator, validatorInitData, registryConfig],
    functionName: "initNexusWithSingleValidator",
  });

  // Format initialization data as expected by ProxyLib
  const initData = encodeAbiParameters(
    [{ type: "address" }, { type: "bytes" }],
    [bootstrapper, bootstrapCall],
  );

  // Calculate CREATE2 address using the same logic as ProxyLib.predictProxyAddress
  return predictProxyAddress(
    accountImplementation,
    salt,
    initData,
    factoryAddress,
  );
}

/**
 * Predicts the proxy address using CREATE2
 * Mirrors ProxyLib.predictProxyAddress functionality exactly
 */
function predictProxyAddress(
  implementation: Address,
  salt: Hex,
  initData: Hex,
  deployer: Address,
): Address {
  // Encode the call to INexus.initializeAccount with initData
  const initializeCall = encodeFunctionData({
    abi: [
      {
        inputs: [{ name: "data", type: "bytes" }],
        name: "initializeAccount",
        type: "function",
      },
    ],
    args: [initData],
    functionName: "initializeAccount",
  });

  // Encode constructor arguments for NexusProxy
  const constructorArgs = encodeAbiParameters(
    [{ type: "address" }, { type: "bytes" }],
    [implementation, initializeCall],
  );

  // Calculate initCodeHash using actual compiled NexusProxy creation bytecode
  const nexusProxyCreationCode =
    "0x60806040526102c8803803806100148161018c565b92833981016040828203126101885781516001600160a01b03811692909190838303610188576020810151906001600160401b03821161018857019281601f8501121561018857835161006e610069826101c5565b61018c565b9481865260208601936020838301011161018857815f926020809301865e8601015260017f90b772c2cb8a51aa7a8a65fc23543c6d022d5b3f8e2b92eed79fba7eef8293005d823b15610176577f360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc80546001600160a01b031916821790557fbc7cd75a20ee27fd9adebab32041f755214dbc6bffa90cc0225b39da2e5c2d3b5f80a282511561015e575f8091610146945190845af43d15610156573d91610137610069846101c5565b9283523d5f602085013e6101e0565b505b6040516089908161023f8239f35b6060916101e0565b50505034156101485763b398979f60e01b5f5260045ffd5b634c9c8ce360e01b5f5260045260245ffd5b5f80fd5b6040519190601f01601f191682016001600160401b038111838210176101b157604052565b634e487b7160e01b5f52604160045260245ffd5b6001600160401b0381116101b157601f01601f191660200190565b9061020457508051156101f557805190602001fd5b63d6bda27560e01b5f5260045ffd5b81511580610235575b610215575090565b639996b31560e01b5f9081526001600160a01b0391909116600452602490fd5b50803b1561020d56fe608060405236156051577f360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc545f9081906001600160a01b0316368280378136915af43d5f803e15604d573d5ff35b3d5ffd5b00fea264697066735822122041b5f70a351952142223f22504ca7b4e6d975f3a302d114ff820442fcf815ac264736f6c634300081b0033" as const;

  const initCodeHash = keccak256(
    encodePacked(["bytes", "bytes"], [nexusProxyCreationCode, constructorArgs]),
  );

  // Standard CREATE2 formula
  return getCreate2Address({
    bytecodeHash: initCodeHash,
    from: deployer,
    salt,
  });
}