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authenticator.ts
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authenticator.ts
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import {
HashAlgorithms,
KeyEncodings,
SecretKey,
createDigestPlaceholder
} from './utils';
import {
TOTP,
TOTPOptions,
totpCheckWithWindow,
totpCreateHmacKey,
totpOptionsValidator,
totpToken
} from './totp';
/**
* RFC4648 / RFC3548 Base32 String.
*
* Other Base32 encoding methods like Crockford's Base32
* will not be compatible with Google Authenticator.
*/
export type Base32SecretKey = SecretKey;
/**
* Interface method for [[AuthenticatorOptions.keyEncoder]].
*/
export interface KeyEncoder<T = Base32SecretKey> {
(secret: SecretKey, encoding: KeyEncodings): T;
}
/**
* Interface method for [[AuthenticatorOptions.keyDecoder]].
*/
export interface KeyDecoder<T = SecretKey> {
(encodedSecret: Base32SecretKey, encoding: KeyEncodings): T;
}
/**
* Interface method for [[AuthenticatorOptions.createRandomBytes]].
*/
export interface CreateRandomBytes<T = string> {
(size: number, encoding: KeyEncodings): T;
}
/**
* Interface for options used in Authenticator.
*
* Contains additional options in addition to
* those within TOTP.
*/
export interface AuthenticatorOptions<T = string> extends TOTPOptions<T> {
/**
* Encodes a secret key into a Base32 string before it is
* sent to the user (in QR Code etc).
*/
keyEncoder: KeyEncoder<T>;
/**
* Decodes the Base32 string given by the user into a secret.
* */
keyDecoder: KeyDecoder<T>;
/**
* Creates a random string containing the defined number of
* bytes to be used in generating a secret key.
*/
createRandomBytes: CreateRandomBytes<T>;
}
/**
* Validates the given [[AuthenticatorOptions]].
*/
export function authenticatorOptionValidator<
T extends AuthenticatorOptions<unknown> = AuthenticatorOptions<unknown>
>(options: Partial<T>): void {
totpOptionsValidator<T>(options);
if (typeof options.keyDecoder !== 'function') {
throw new Error('Expecting options.keyDecoder to be a function.');
}
if (options.keyEncoder && typeof options.keyEncoder !== 'function') {
throw new Error('Expecting options.keyEncoder to be a function.');
}
}
/**
* Returns a set of default options for authenticator at the current epoch.
*/
export function authenticatorDefaultOptions<
T extends AuthenticatorOptions<unknown> = AuthenticatorOptions<unknown>
>(): Partial<T> {
const options = {
algorithm: HashAlgorithms.SHA1,
createDigest: createDigestPlaceholder,
createHmacKey: totpCreateHmacKey,
digits: 6,
encoding: KeyEncodings.HEX,
epoch: Date.now(),
step: 30,
window: 0
};
return (options as unknown) as Partial<T>;
}
/**
* Takes an Authenticator Option object and provides presets for
* some of the missing required Authenticator option fields and validates
* the resultant options.
*/
export function authenticatorOptions<
T extends AuthenticatorOptions<unknown> = AuthenticatorOptions<unknown>
>(opt: Partial<T>): Readonly<T> {
const options = {
...authenticatorDefaultOptions<T>(),
...opt
};
authenticatorOptionValidator<T>(options);
return Object.freeze(options) as Readonly<T>;
}
/**
* Encodes a given secret key into a Base32 secret
* using a [[KeyEncoder]] method set in the options.
*
* @param secret - The [[SecretKey]] to encode into a [[Base32SecretKey]]
* @param options - An [[AuthenticatorOptions]] object
*/
export function authenticatorEncoder<
T extends AuthenticatorOptions<unknown> = AuthenticatorOptions<unknown>
>(
secret: SecretKey,
options: Pick<T, 'keyEncoder' | 'encoding'>
): ReturnType<T['keyEncoder']> {
return options.keyEncoder(secret, options.encoding) as ReturnType<
T['keyEncoder']
>;
}
/**
* Decodes a given Base32 secret to a secret key
* using a [[KeyDecoder]] method set in the options.
*
* @param secret - The [[Base32SecretKey]] to decode
* @param options - An [[AuthenticatorOptions]] object
*/
export function authenticatorDecoder<
T extends AuthenticatorOptions<unknown> = AuthenticatorOptions<unknown>
>(
secret: Base32SecretKey,
options: Pick<T, 'keyDecoder' | 'encoding'>
): ReturnType<T['keyDecoder']> {
return options.keyDecoder(secret, options.encoding) as ReturnType<
T['keyDecoder']
>;
}
/**
* Generates a random Base32 Secret Key.
*
* @param numberOfBytes - Number of bytes per secret key
* @param options.createRandomBytes
* @param options.encoding
* @param options.keyEncoder
*/
export function authenticatorGenerateSecret<
T extends AuthenticatorOptions = AuthenticatorOptions
>(
numberOfBytes: number,
options: Pick<T, 'keyEncoder' | 'encoding' | 'createRandomBytes'>
): Base32SecretKey {
const key = options.createRandomBytes(numberOfBytes, options.encoding);
return authenticatorEncoder<T>(key, options);
}
/**
* Generates the Authenticator based token.
*
* tl;dr: Authenticator = TOTP + Base32 Secret
*
* **References**
*
* - https://en.wikipedia.org/wiki/Google_Authenticator
*
* @param secret - [[Base32SecretKey]]
* @param options - An [[AuthenticatorOptions]] object.
*/
export function authenticatorToken<
T extends AuthenticatorOptions = AuthenticatorOptions
>(secret: Base32SecretKey, options: Readonly<T>): string {
return totpToken<T>(authenticatorDecoder<T>(secret, options), options);
}
/**
* Decodes the encodedSecret and passes it to [[totpCheckWithWindow]]
*
* @param token - The token to check
* @param secret - The [[Base32SecretKey]]
* @param options - An [[AuthenticatorOptions]] object.
*/
export function authenticatorCheckWithWindow<
T extends AuthenticatorOptions = AuthenticatorOptions
>(token: string, secret: Base32SecretKey, options: Readonly<T>): number | null {
return totpCheckWithWindow<T>(
token,
authenticatorDecoder<T>(secret, options),
options
);
}
/**
* A class wrapper containing all Authenticator methods.
*/
export class Authenticator<
T extends AuthenticatorOptions<string> = AuthenticatorOptions<string>
> extends TOTP<T> {
/**
* Creates a new instance with all defaultOptions and options reset.
*/
public create(defaultOptions: Partial<T> = {}): Authenticator<T> {
return new Authenticator<T>(defaultOptions);
}
/**
* Returns a set of options at the current moment,
* polyfilled with some of the missing required options.
*
* Refer to [[authenticatorOptions]]
*/
public allOptions(): Readonly<T> {
return authenticatorOptions<T>(this.options);
}
/**
* Reference: [[authenticatorToken]]
*/
public generate(secret: Base32SecretKey): string {
return authenticatorToken<T>(secret, this.allOptions());
}
/**
* Reference: [[authenticatorCheckWithWindow]]
*/
public checkDelta(token: string, secret: Base32SecretKey): number | null {
return authenticatorCheckWithWindow<T>(token, secret, this.allOptions());
}
/**
* Reference: [[authenticatorEncoder]]
*/
public encode(secret: SecretKey): Base32SecretKey {
return authenticatorEncoder<T>(secret, this.allOptions());
}
/**
* Reference: [[authenticatorDecoder]]
*/
public decode(secret: Base32SecretKey): SecretKey {
return authenticatorDecoder<T>(secret, this.allOptions());
}
/**
* Reference: [[authenticatorGenerateSecret]]
*/
public generateSecret(numberOfBytes = 10): Base32SecretKey {
return authenticatorGenerateSecret<T>(numberOfBytes, this.allOptions());
}
}