add vote uniqueness, public key caching, relative poll timeframe, auth/rate limiting, modern UI styling, and error handling
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211
app/utils/crypto.ts
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211
app/utils/crypto.ts
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// utils/crypto.ts
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import type { SignedData, VoteData, PollMetadata } from "./types";
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export const generateUserKeyPair = async () => {
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return await window.crypto.subtle.generateKey(
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{
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name: "RSASSA-PKCS1-v1_5",
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modulusLength: 2048,
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publicExponent: new Uint8Array([1, 0, 1]), // 65537
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hash: "SHA-256",
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},
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true, // extractable
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["sign", "verify"]
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);
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};
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export const signVote = async (data: any, privateKey: CryptoKey) => {
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const encoder = new TextEncoder();
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const encodedData = encoder.encode(JSON.stringify(data));
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const signature = await window.crypto.subtle.sign(
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"RSASSA-PKCS1-v1_5",
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privateKey,
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encodedData
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);
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// Convert to Base64 or Hex to store in Yjs easily
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return btoa(String.fromCharCode(...new Uint8Array(signature)));
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};
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export const verifyVote = async (data: any, signatureStr: string, publicKey: CryptoKey) => {
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const encoder = new TextEncoder();
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const encodedData = encoder.encode(JSON.stringify(data));
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// Convert Base64 back to Uint8Array
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const signature = Uint8Array.from(atob(signatureStr), c => c.charCodeAt(0));
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return await window.crypto.subtle.verify(
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"RSASSA-PKCS1-v1_5",
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publicKey,
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signature,
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encodedData
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);
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};
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/**
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* Verifies a specific vote within an array of votes by
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* reconstructing the "signed state" at that point in time.
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*/
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export const verifyChainedVote = async (
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voteData: SignedData<VoteData>[],
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index: number,
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publicKeysCache?: Record<string, CryptoKey>,
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pollMetadata?: PollMetadata
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) => {
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const voteToVerify = voteData[index];
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console.log("Verifying vote: " + voteToVerify)
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if(voteToVerify) {
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// 1. Check vote timestamp against poll duration if metadata is available
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if (pollMetadata) {
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const voteTime = new Date(voteToVerify.data.timestamp).getTime();
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const timeSinceCreation = voteTime - pollMetadata.createdAt;
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if (timeSinceCreation > pollMetadata.duration) {
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console.error(`Vote timestamp exceeds poll duration: ${timeSinceCreation}ms > ${pollMetadata.duration}ms`);
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return false;
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}
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}
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// 2. Reconstruct the exact data state the user signed
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// We need the array exactly as it was when they pushed their vote
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const historicalState = voteData.slice(0, index + 1).map((v, i) => {
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if (i === index) {
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// For the current vote, the signature must be empty string
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// because it wasn't signed yet when passed to signVote
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return { ...v, signature: "" };
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}
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return v;
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});
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try {
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// 3. Get public key from cache or fetch from API
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let pubKey: CryptoKey;
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if (publicKeysCache && publicKeysCache[voteToVerify.data.userid]) {
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pubKey = publicKeysCache[voteToVerify.data.userid];
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console.log("Using cached public key for user:", voteToVerify.data.userid);
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} else {
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const response = await $fetch<{ public_key: string }>(`/api/users/${voteToVerify.data.userid}`);
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console.log("Got key from API: ",response)
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pubKey = await stringToCryptoKey(response.public_key, 'public');
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}
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console.log("Using pubKey to verify Vote.")
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// 4. Verify: Does this historicalState match the signature?
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return await verifyVote(historicalState, voteToVerify.signature, pubKey);
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} catch (err) {
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console.error("Verification failed")
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console.error(err);
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return false;
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}
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}
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console.error("Vote is undefined or null");
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return false;
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};
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export const verifyAllVotesForOption = async (
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votes: SignedData<VoteData>[],
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publicKeysCache?: Record<string, CryptoKey>,
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pollMetadata?: PollMetadata
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) => {
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console.log("verifying votes for option ",votes);
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for (let i = votes.length-1; i >= 0 ; i--) {
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const isValid = await verifyChainedVote(votes, i, publicKeysCache, pollMetadata);
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if(!isValid){
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console.error("Error! Invalid Vote at: " + i,votes)
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return false;
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}
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}
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return true;
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};
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// Helper to convert ArrayBuffer to Base64 string
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const bufferToBase64 = (buf: ArrayBuffer) =>
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window.btoa(String.fromCharCode(...new Uint8Array(buf)));
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export const exportPublicKey = async (key: CryptoKey) => {
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// Export Public Key
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const exportedPublic = await window.crypto.subtle.exportKey("spki", key);
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const publicKeyString = bufferToBase64(exportedPublic);
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return publicKeyString;
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};
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export const exportPrivateKey = async (key: CryptoKey) => {
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// Export Private Key
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const exportedPrivate = await window.crypto.subtle.exportKey("pkcs8", key);
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const privateKeyString = bufferToBase64(exportedPrivate);
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return privateKeyString;
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};
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/**
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* Converts a Base64 string back into a usable CryptoKey object
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* @param keyStr The Base64 string (without PEM headers)
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* @param type 'public' or 'private'
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*/
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export const stringToCryptoKey = async (keyStr: string, type: 'public' | 'private'): Promise<CryptoKey> => {
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// 1. Convert Base64 string to a Uint8Array (binary)
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const binaryString = window.atob(keyStr);
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const bytes = new Uint8Array(binaryString.length);
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for (let i = 0; i < binaryString.length; i++) {
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bytes[i] = binaryString.charCodeAt(i);
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}
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// 2. Identify the format based on the key type
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// Public keys usually use 'spki', Private keys use 'pkcs8'
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const format = type === 'public' ? 'spki' : 'pkcs8';
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const usages: KeyUsage[] = type === 'public' ? ['verify'] : ['sign'];
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// 3. Import the key
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return await window.crypto.subtle.importKey(
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format,
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bytes.buffer,
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{
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name: "RSASSA-PKCS1-v1_5",
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hash: "SHA-256",
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},
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true, // extractable (set to false if you want to lock it in memory)
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usages
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);
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};
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export const savePrivateKeyToFile = (privateKeyStr: string, filename: string) => {
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// Optional: Wrap in PEM headers for standard formatting
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const pemHeader = "-----BEGIN PRIVATE KEY-----\n";
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const pemFooter = "\n-----END PRIVATE KEY-----";
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const fileContent = pemHeader + privateKeyStr + pemFooter;
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const blob = new Blob([fileContent], { type: "text/plain" });
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const url = URL.createObjectURL(blob);
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const link = document.createElement("a");
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link.href = url;
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link.download = filename;
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document.body.appendChild(link);
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link.click();
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// Cleanup
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document.body.removeChild(link);
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URL.revokeObjectURL(url);
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};
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export const loadPrivateKeyFromFile = async (file: File): Promise<string> => {
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return new Promise((resolve, reject) => {
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const reader = new FileReader();
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reader.onload = (e) => {
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const content = e.target?.result as string;
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// Clean up the string by removing PEM headers and newlines
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const cleanKey = content
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.replace("-----BEGIN PRIVATE KEY-----", "")
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.replace("-----END PRIVATE KEY-----", "")
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.replace(/\s+/g, ""); // Removes all whitespace/newlines
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resolve(cleanKey);
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};
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reader.onerror = () => reject("Error reading file");
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reader.readAsText(file);
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});
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};
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