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/*4.1 authentication: (http://bazaar.launchpad.net/~mysql/mysql-server/5.5/view/head:/sql/password.c)
  SERVER:  public_seed=create_random_string()           send(public_seed)
  CLIENT:  recv(public_seed)           hash_stage1=sha1("password")           hash_stage2=sha1(hash_stage1)           reply=xor(hash_stage1, sha1(public_seed,hash_stage2)
           // this three steps are done in scramble()
           send(reply)

  SERVER:  recv(reply)           hash_stage1=xor(reply, sha1(public_seed,hash_stage2))           candidate_hash2=sha1(hash_stage1)           check(candidate_hash2==hash_stage2)
server stores sha1(sha1(password)) ( hash_stag2)*/
import {  Buffer,  createHash,} from "../deps.ts";
function sha1(msg: Buffer|string, msg1?: Buffer|string, msg2?: Buffer|string) {  const hash = createHash('sha1');  hash.update(msg);  if (msg1) {    hash.update(msg1);  }
  if (msg2) {    hash.update(msg2);  }
  return hash.digest() as Buffer;}
export function xor(a: Buffer|string, b: Buffer|string) {  if (!Buffer.isBuffer(a)) {    a = Buffer.from(a, 'binary');  }
  if (!Buffer.isBuffer(b)) {    b = Buffer.from(b, 'binary');  }
  const result = Buffer.allocUnsafe(a.length);
  for (let i = 0; i < a.length; i++) {    result[i] = a[i] ^ b[i];  }  return result;}
function token(password: string, scramble1: Buffer, scramble2: Buffer) {  // TODO: use buffers (not sure why strings here)  if (!password) {    return Buffer.alloc(0);  }  const stage1 = sha1(password);  return calculateTokenFromPasswordSha(stage1, scramble1, scramble2);}
export function calculateTokenFromPasswordSha(  passwordSha: Buffer|string,  scramble1: Buffer,  scramble2: Buffer,) {  // we use AUTH 41 here, and we need only the bytes we just need.  const authPluginData1 = scramble1.slice(0, 8);  const authPluginData2 = scramble2.slice(0, 12);  const stage2 = sha1(passwordSha);  const stage3 = sha1(authPluginData1, authPluginData2, stage2);  return xor(stage3, passwordSha);}
export const calculateToken = token;
export function verifyToken(publicSeed1: string | Buffer, publicSeed2: string | Buffer, token: string | Buffer, doubleSha: string | Buffer) {  const hashStage1 = xor(token, sha1(publicSeed1, publicSeed2, doubleSha));  const candidateHash2 = sha1(hashStage1);  return candidateHash2.compare(Buffer.from(doubleSha)) === 0;}
export function doubleSha1(password: string) {  return sha1(sha1(password));}
export function xorRotating(a: string | Buffer, seed: string | Buffer) {  if (!Buffer.isBuffer(a)) {    a = Buffer.from(a, 'binary');  }
  if (!Buffer.isBuffer(seed)) {    seed = Buffer.from(seed, 'binary');  }
  const result = Buffer.allocUnsafe(a.length);  const seedLen = seed.length;
  for (let i = 0; i < a.length; i++) {    result[i] = a[i] ^ seed[i % seedLen];  }  return result;}