veritatisdoloremque
Version:
Monorepo for the Firebase JavaScript SDK
56 lines (47 loc) • 1.95 kB
text/typescript
/**
* @license
* Copyright 2019 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import { bufferToBase64UrlSafe } from './buffer-to-base64-url-safe';
export const VALID_FID_PATTERN = /^[cdef][\w-]{21}$/;
export const INVALID_FID = '';
/**
* Generates a new FID using random values from Web Crypto API.
* Returns an empty string if FID generation fails for any reason.
*/
export function generateFid(): string {
try {
// A valid FID has exactly 22 base64 characters, which is 132 bits, or 16.5
// bytes. our implementation generates a 17 byte array instead.
const fidByteArray = new Uint8Array(17);
const crypto =
self.crypto || ((self as unknown) as { msCrypto: Crypto }).msCrypto;
crypto.getRandomValues(fidByteArray);
// Replace the first 4 random bits with the constant FID header of 0b0111.
fidByteArray[0] = 0b01110000 + (fidByteArray[0] % 0b00010000);
const fid = encode(fidByteArray);
return VALID_FID_PATTERN.test(fid) ? fid : INVALID_FID;
} catch {
// FID generation errored
return INVALID_FID;
}
}
/** Converts a FID Uint8Array to a base64 string representation. */
function encode(fidByteArray: Uint8Array): string {
const b64String = bufferToBase64UrlSafe(fidByteArray);
// Remove the 23rd character that was added because of the extra 4 bits at the
// end of our 17 byte array, and the '=' padding.
return b64String.substr(0, 22);
}