Redirect at previous page after a successful login

After the user was authenticated a redirect to the site which
linked the user to the login page is done. This fixes FS#32481.

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

web/html/login.php

@@ -42,6 +42,11 @@ html_header('AUR ' . __("Login"));
 			<p>
 				<input type="submit" class="button" value="<?php  print __("Login"); ?>" />
 				<a href="<?= get_uri('/passreset/') ?>">[<?= __('Forgot Password') ?>]</a>
+				<?php if (in_request('referer') !== ""): ?>
+				<input id="id_referer" type="hidden" name="referer" value="<?= in_request('referer') ?>" />
+				<?php elseif (isset($_SERVER['HTTP_REFERER'])): ?>
+				<input id="id_referer" type="hidden" name="referer" value="<?= htmlspecialchars($_SERVER['HTTP_REFERER'], ENT_QUOTES) ?>" />
+				<?php endif; ?>
 			</p>
 		</fieldset>
 	</form>

web/lib/acctfuncs.inc.php

@@ -544,7 +544,12 @@ function try_login() {
 	}
 
 	setcookie("AURSID", $new_sid, $cookie_time, "/", null, !empty($_SERVER['HTTPS']), true);
-	header("Location: " . get_uri('/'));
+
+	$referer = in_request('referer');
+	if (strpos($referer, aur_location()) !== 0) {
+		$referer = '/';
+	}
+	header("Location: " . get_uri($referer));
 	$login_error = "";
 }