fix: Adjustment in the recording of temporary files and periodic cleaning

src/utils/poll-update-decrypt-message.ts

@@ -0,0 +1,164 @@
+// Built around ShellTear's POC at #2215#issuecomment-1292885678 on @adiwajshing/baileys
+// Copyright ~ purpshell
+
+import crypto from 'node:crypto';
+
+const enc = new TextEncoder();
+/**
+ * Decrypt PollUpdate messages
+ */
+export class PollUpdateDecrypt {
+  /**
+   * Compare the SHA-256 hashes of the poll options from the update to find the original choices
+   * @param options Options from the poll creation message
+   * @param pollOptionHash hash from `this.decrypt()`
+   * @returns the original option, can be empty when none are currently selected
+   */
+  static async compare(options: string[], pollOptionHashes: string[]): Promise<string[]> {
+    const selectedOptions = [];
+    for (const option of options) {
+      const hash = Buffer.from(
+        await crypto.webcrypto.subtle.digest('SHA-256', new TextEncoder().encode(option)),
+      )
+        .toString('hex')
+        .toUpperCase();
+      for (const pollOptionHash of pollOptionHashes) {
+        if (pollOptionHash === hash) {
+          selectedOptions.push(option);
+        }
+      }
+    }
+    return selectedOptions;
+  }
+
+  /**
+   * decrypt a poll message update
+   * @param encPayload from the update
+   * @param encIv from the update
+   * @param encKey from the original poll
+   * @param pollMsgSender sender jid of the pollCreation message
+   * @param pollMsgId id of the pollCreation message
+   * @param voteMsgSender sender of the pollUpdate message
+   * @returns The option or empty array if something went wrong OR everything was unticked
+   */
+  static async decrypt(
+    encKey: Uint8Array,
+    encPayload: Uint8Array,
+    encIv: Uint8Array,
+    pollMsgSender: string,
+    pollMsgId: string,
+    voteMsgSender: string,
+  ): Promise<string[]> {
+    const stanzaId = enc.encode(pollMsgId);
+    const parentMsgOriginalSender = enc.encode(pollMsgSender);
+    const modificationSender = enc.encode(voteMsgSender);
+    const modificationType = enc.encode('Poll Vote');
+    const pad = new Uint8Array([1]);
+
+    const signMe = new Uint8Array([
+      ...stanzaId,
+      ...parentMsgOriginalSender,
+      ...modificationSender,
+      ...modificationType,
+      pad,
+    ] as any);
+
+    const createSignKey = async (n: Uint8Array = new Uint8Array(32)) => {
+      return await crypto.webcrypto.subtle.importKey(
+        'raw',
+        n,
+        { name: 'HMAC', hash: 'SHA-256' },
+        false,
+        ['sign'],
+      );
+    };
+
+    const sign = async (
+      n: crypto.webcrypto.BufferSource,
+      key: crypto.webcrypto.CryptoKey,
+    ) => {
+      return await crypto.webcrypto.subtle.sign(
+        { name: 'HMAC', hash: 'SHA-256' },
+        key,
+        n,
+      );
+    };
+
+    let key = await createSignKey();
+
+    const temp = await sign(encKey, key);
+
+    key = await createSignKey(new Uint8Array(temp));
+
+    const decryptionKey = new Uint8Array(await sign(signMe, key));
+
+    const additionalData = enc.encode(`${pollMsgId}\u0000${voteMsgSender}`);
+
+    const decryptedMessage = await this._decryptMessage(
+      encPayload,
+      encIv,
+      additionalData,
+      decryptionKey,
+    );
+
+    const pollOptionHash = this._decodeMessage(decryptedMessage);
+
+    // '0A20' in hex represents unicode " " and "\n" thus declaring the end of one option
+    // we want multiple hashes to make it easier to iterate and understand for your use cases
+    return pollOptionHash.split('0A20') || [];
+  }
+
+  /**
+   * Internal method to decrypt the message after gathering all information
+   * @deprecated Use `this.decrypt()` instead, only use this if you know what you are doing
+   * @param encPayload
+   * @param encIv
+   * @param additionalData
+   * @param decryptionKey
+   * @returns
+   */
+  static async _decryptMessage(
+    encPayload: Uint8Array,
+    encIv: Uint8Array,
+    additionalData: Uint8Array,
+    decryptionKey: Uint8Array,
+  ) {
+    const tagSize_multiplier = 16;
+    const encoded = encPayload;
+    const key = await crypto.webcrypto.subtle.importKey(
+      'raw',
+      decryptionKey,
+      'AES-GCM',
+      false,
+      ['encrypt', 'decrypt'],
+    );
+    const decrypted = await crypto.webcrypto.subtle.decrypt(
+      {
+        name: 'AES-GCM',
+        iv: encIv,
+        additionalData: additionalData,
+        tagLength: 8 * tagSize_multiplier,
+      },
+      key,
+      encoded,
+    );
+    return new Uint8Array(decrypted).slice(2); // remove 2 bytes (OA20)(space+newline)
+  }
+
+  /**
+   * Decode the message from `this._decryptMessage()`
+   * @param decryptedMessage the message from `this._decrpytMessage()`
+   * @returns
+   */
+  static _decodeMessage(decryptedMessage: Uint8Array) {
+    const n = [48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 65, 66, 67, 68, 69, 70];
+    const outarr: number[] = [];
+
+    for (let i = 0; i < decryptedMessage.length; i++) {
+      const val = decryptedMessage[i];
+      outarr.push(n[val >> 4], n[15 & val]);
+    }
+
+    return String.fromCharCode(...outarr);
+  }
+}