[feature] add TOTP two-factor authentication (2FA) (#3960)

* [feature] add TOTP two-factor authentication (2FA)

* use byteutil.S2B to avoid allocations when comparing + generating password hashes

* don't bother with string conversion  for consts

* use io.ReadFull

* use MustGenerateSecret for backup codes

* rename util functions

1 files changed, 123 insertions, 0 deletions

diff --git a/web/source/settings/views/user/account/email.tsx b/web/source/settings/views/user/account/email.tsx
new file mode 100644
index 000000000..16cdebf66
--- /dev/null
+++ b/web/source/settings/views/user/account/email.tsx
@@ -0,0 +1,123 @@
+/*
+	GoToSocial
+	Copyright (C) GoToSocial Authors admin@gotosocial.org
+	SPDX-License-Identifier: AGPL-3.0-or-later
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Affero General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Affero General Public License for more details.
+
+	You should have received a copy of the GNU Affero General Public License
+	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+import React from "react";
+import { useTextInput } from "../../../lib/form";
+import useFormSubmit from "../../../lib/form/submit";
+import { TextInput } from "../../../components/form/inputs";
+import MutationButton from "../../../components/form/mutation-button";
+import { useEmailChangeMutation } from "../../../lib/query/user";
+import { User } from "../../../lib/types/user";
+
+export default function EmailChange({user, oidcEnabled}: { user: User, oidcEnabled?: boolean }) {
+	const form = {
+		currentEmail: useTextInput("current_email", {
+			defaultValue: user.email,
+			nosubmit: true
+		}),
+		newEmail: useTextInput("new_email", {
+			validator: (value: string | undefined) => {
+				if (!value) {
+					return "";
+				}
+
+				if (value.toLowerCase() === user.email?.toLowerCase()) {
+					return "cannot change to your existing address";
+				}
+
+				if (value.toLowerCase() === user.unconfirmed_email?.toLowerCase()) {
+					return "you already have a pending email address change to this address";
+				}
+
+				return "";
+			},
+		}),
+		password: useTextInput("password"),
+	};
+	const [submitForm, result] = useFormSubmit(form, useEmailChangeMutation());
+
+	return (
+		<form className="change-email" onSubmit={submitForm}>
+			<div className="form-section-docs">
+				<h3>Change Email</h3>
+				{ oidcEnabled && <p>
+					This instance is running with OIDC as its authorization + identity provider.
+					<br/>
+					You can still change your email address using this settings panel,
+					but it will only affect which address GoToSocial uses to contact you,
+					not the email address you use to log in.
+					<br/>
+					To change the email address you use to log in, contact your OIDC provider.
+				</p> }
+				<a
+					href="https://docs.gotosocial.org/en/latest/user_guide/settings/#email-change"
+					target="_blank"
+					className="docslink"
+					rel="noreferrer"
+				>
+					Learn more about this (opens in a new tab)
+				</a>
+			</div>
+
+			{ (user.unconfirmed_email && user.unconfirmed_email !== user.email) && <>
+				<div className="info">
+					<i className="fa fa-fw fa-info-circle" aria-hidden="true"></i>
+					<b>
+						You currently have a pending email address
+						change to the address: {user.unconfirmed_email}
+						<br />
+						To confirm {user.unconfirmed_email} as your new
+						address for this account, please check your email inbox.
+					</b>
+				</div>
+			</> }
+
+			<TextInput
+				type="email"
+				name="current-email"
+				field={form.currentEmail}
+				label="Current email address"
+				autoComplete="none"
+				disabled={true}
+			/>
+
+			<TextInput
+				type="password"
+				name="password"
+				field={form.password}
+				label="Current password"
+				autoComplete="current-password"
+			/>
+
+			<TextInput
+				type="email"
+				name="new-email"
+				field={form.newEmail}
+				label="New email address"
+				autoComplete="none"
+			/>
+			
+			<MutationButton
+				disabled={!form.password || !form.newEmail || !form.newEmail.valid}
+				label="Change email address"
+				result={result}
+			/>
+		</form>
+	);
+}