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/*
* qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
* Copyright (C) 2026 Danilo M. <danix@danix.xyz>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "requestinterceptor.h"
#include <QWebEngineUrlRequestInfo>
RequestInterceptor::RequestInterceptor(QObject *parent)
: QWebEngineUrlRequestInterceptor(parent)
{
}
bool RequestInterceptor::shouldAllow(const QUrl &url)
{
// QUrl::scheme() always normalizes to lowercase (verified: QUrl("HTTP://x/y")
// .scheme() == "http"), so a lowercase-literal compare cannot be bypassed
// by unusual casing, in either the allow or the deny direction.
const QString scheme = url.scheme();
// data: is never allowed here. It is permitted for the main-frame
// document only, which is handled in interceptRequest() where the resource
// type is known: a message body can put data: in <img src> or
// <iframe src>, and those must stay blocked.
// The document's origin is the qtmaildir: base URL, so requests can still
// arrive on that scheme once the document is live.
// This is the ONLY trusted qtmaildir: URL: everything else on this scheme
// is denied, including sub-paths of it. A hostile message body can put
// arbitrary qtmaildir: URLs in <img src>, <link href>, etc., so this
// cannot be a whole-scheme allow; it must be an exact match against the
// one URL the application itself chose. If setDocumentUrl() was never
// called, m_documentUrl is a default-constructed (invalid, empty) QUrl,
// which cannot equal any real request URL, so this fails closed.
if (scheme == QLatin1String("qtmaildir")) {
if (!m_documentUrl.isEmpty() && url == m_documentUrl)
return true;
m_blockedAnything = true;
return false;
}
// Inline parts of the current message only.
if (scheme == QLatin1String("cid")) {
// QUrl keeps a cid: body in path(), not host() or userName(), even
// when it contains '@' (verified empirically: QUrl("cid:logo@example.org")
// .path() == "logo@example.org", host() and userName() are empty).
// path() also returns the percent-decoded form, so a percent-encoded
// id (e.g. "%6Cogo@example.org") compares equal to its decoded form,
// not to some other allowed id: it cannot be used to smuggle a
// foreign id past the allowlist, only to spell an already-legitimate
// id differently.
const QString id = url.path();
if (m_allowedCids.contains(id))
return true;
m_blockedAnything = true;
return false;
}
if (scheme == QLatin1String("http") || scheme == QLatin1String("https")) {
if (m_allowRemote)
return true;
m_blockedAnything = true;
return false;
}
// Everything else, including file:, javascript:, data:, blob:, about:,
// chrome:, qrc:, filesystem:, protocol-relative URLs (empty scheme with a
// host), and empty/malformed URLs (empty scheme), is denied
// unconditionally. There is no flag that enables it.
m_blockedAnything = true;
return false;
}
void RequestInterceptor::interceptRequest(QWebEngineUrlRequestInfo &info)
{
// The main-frame document arrives as a data: URL, because setHtml() does
// not fetch the base URL it is given: it navigates to a data: URL carrying
// the markup and applies the base URL afterwards as the document's origin.
// (Verified empirically on Qt 6.11. The qtmaildir: rule in shouldAllow()
// was written on the opposite assumption, and until this was found every
// document load was blocked and the pane rendered blank.)
//
// Scoping this to ResourceTypeMainFrame is what keeps it from being a
// hole: those bytes are the ones HtmlBuilder produced a moment earlier and
// they arrive in the navigation itself rather than over any transport,
// while a data: URL written into a message body reaches this function as
// an image, stylesheet or subframe and is still denied by shouldAllow().
if (info.resourceType() == QWebEngineUrlRequestInfo::ResourceTypeMainFrame
&& info.requestUrl().scheme() == QLatin1String("data")) {
return;
}
if (!shouldAllow(info.requestUrl()))
info.block(true);
}
void RequestInterceptor::resetForNewMessage()
{
m_allowRemote = false;
m_blockedAnything = false;
}
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