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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "FramingChecker.h"
#include <stdint.h> // uint32_t
#include "nsCOMPtr.h"
#include "nsContentUtils.h"
#include "nsDebug.h"
#include "nsError.h"
#include "nsHttpChannel.h"
#include "nsContentSecurityUtils.h"
#include "nsGlobalWindowOuter.h"
#include "nsIContentPolicy.h"
#include "nsIScriptError.h"
#include "nsLiteralString.h"
#include "nsTArray.h"
#include "nsStringFwd.h"
#include "mozilla/Assertions.h"
#include "mozilla/dom/WindowGlobalParent.h"
#include "mozilla/net/HttpBaseChannel.h"
#include "mozilla/RefPtr.h"
#include "mozilla/Services.h"
#include "mozilla/Unused.h"
#include "nsIObserverService.h"
using namespace mozilla;
using namespace mozilla::dom;
/* static */
void FramingChecker::ReportError(const char* aMessageTag,
nsIHttpChannel* aChannel, nsIURI* aURI,
const nsAString& aPolicy) {
MOZ_ASSERT(aChannel);
MOZ_ASSERT(aURI);
nsCOMPtr<net::HttpBaseChannel> httpChannel = do_QueryInterface(aChannel);
if (!httpChannel) {
return;
}
// Get the URL spec
nsAutoCString spec;
nsresult rv = aURI->GetAsciiSpec(spec);
if (NS_FAILED(rv)) {
return;
}
nsTArray<nsString> params;
params.AppendElement(aPolicy);
params.AppendElement(NS_ConvertUTF8toUTF16(spec));
httpChannel->AddConsoleReport(nsIScriptError::errorFlag, "X-Frame-Options"_ns,
nsContentUtils::eSECURITY_PROPERTIES, spec, 0,
0, nsDependentCString(aMessageTag), params);
// we are notifying observers for testing purposes because there is no event
// to gather that an iframe load was blocked or not.
nsCOMPtr<nsIObserverService> observerService =
mozilla::services::GetObserverService();
nsAutoString policy(aPolicy);
observerService->NotifyObservers(aURI, "xfo-on-violate-policy", policy.get());
}
// Ignore x-frame-options if CSP with frame-ancestors exists
static bool ShouldIgnoreFrameOptions(nsIChannel* aChannel,
nsIContentSecurityPolicy* aCSP) {
NS_ENSURE_TRUE(aChannel, false);
if (!aCSP) {
return false;
}
bool enforcesFrameAncestors = false;
aCSP->GetEnforcesFrameAncestors(&enforcesFrameAncestors);
if (!enforcesFrameAncestors) {
// if CSP does not contain frame-ancestors, then there
// is nothing to do here.
return false;
}
return true;
}
// Check if X-Frame-Options permits this document to be loaded as a
// subdocument. This will iterate through and check any number of
// X-Frame-Options policies in the request (comma-separated in a header,
// multiple headers, etc).
// This is based on:
// https://html.spec.whatwg.org/multipage/document-lifecycle.html#the-x-frame-options-header
/* static */
bool FramingChecker::CheckFrameOptions(nsIChannel* aChannel,
nsIContentSecurityPolicy* aCsp,
bool& outIsFrameCheckingSkipped) {
// Step 1. If navigable is not a child navigable return true
if (!aChannel) {
return true;
}
// xfo check only makes sense for subdocument and object loads, if this is
// not a load of such type, there is nothing to do here.
nsCOMPtr<nsILoadInfo> loadInfo = aChannel->LoadInfo();
ExtContentPolicyType contentType = loadInfo->GetExternalContentPolicyType();
if (contentType != ExtContentPolicy::TYPE_SUBDOCUMENT &&
contentType != ExtContentPolicy::TYPE_OBJECT) {
return true;
}
// xfo can only hang off an httpchannel, if this is not an httpChannel
// then there is nothing to do here.
nsCOMPtr<nsIHttpChannel> httpChannel;
nsresult rv = nsContentSecurityUtils::GetHttpChannelFromPotentialMultiPart(
aChannel, getter_AddRefs(httpChannel));
if (NS_WARN_IF(NS_FAILED(rv))) {
return true;
}
if (!httpChannel) {
return true;
}
// ignore XFO checks on channels that will be redirected
uint32_t responseStatus;
rv = httpChannel->GetResponseStatus(&responseStatus);
if (NS_FAILED(rv)) {
// GetResponseStatus returning failure is expected in several situations, so
// do not warn if it fails.
return true;
}
if (mozilla::net::nsHttpChannel::IsRedirectStatus(responseStatus)) {
return true;
}
nsAutoCString xfoHeaderValue;
Unused << httpChannel->GetResponseHeader("X-Frame-Options"_ns,
xfoHeaderValue);
// Step 10. (paritally) if the only header we received was empty, then we
// process it as if it wasn't sent at all.
if (xfoHeaderValue.IsEmpty()) {
return true;
}
// Step 2. xfo checks are ignored in the case where CSP frame-ancestors is
// present, if so, there is nothing to do here.
if (ShouldIgnoreFrameOptions(aChannel, aCsp)) {
outIsFrameCheckingSkipped = true;
return true;
}
// Step 3-4. reduce the header options to a unique set and count how many
// unique values (that we track) are encountered. this avoids using a set to
// stop attackers from inheriting arbitrary values in memory and reduce the
// complexity of the code.
XFOHeader xfoOptions;
for (const nsACString& next : xfoHeaderValue.Split(',')) {
nsAutoCString option(next);
option.StripWhitespace();
if (option.LowerCaseEqualsLiteral("allowall")) {
xfoOptions.ALLOWALL = true;
} else if (option.LowerCaseEqualsLiteral("sameorigin")) {
xfoOptions.SAMEORIGIN = true;
} else if (option.LowerCaseEqualsLiteral("deny")) {
xfoOptions.DENY = true;
} else {
xfoOptions.INVALID = true;
}
}
nsCOMPtr<nsIURI> uri;
httpChannel->GetURI(getter_AddRefs(uri));
// Step 6. if header has multiple contradicting directives return early and
// prohibit the load. ALLOWALL is considered here for legacy reasons.
uint32_t xfoUniqueOptions = xfoOptions.DENY + xfoOptions.ALLOWALL +
xfoOptions.SAMEORIGIN + xfoOptions.INVALID;
if (xfoUniqueOptions > 1 &&
(xfoOptions.DENY || xfoOptions.ALLOWALL || xfoOptions.SAMEORIGIN)) {
ReportError("XFrameOptionsInvalid", httpChannel, uri, u"invalid"_ns);
return false;
}
// Step 7 (multiple INVALID values) and partially Step 10 (single INVALID
// value). if header has any invalid options, but no valid directives (DENY,
// ALLOWALL, SAMEORIGIN) then allow the load.
if (xfoOptions.INVALID) {
ReportError("XFrameOptionsInvalid", httpChannel, uri, u"invalid"_ns);
return true;
}
// Step 8. if the value of the header is DENY prohibit the load.
if (xfoOptions.DENY) {
ReportError("XFrameOptionsDeny", httpChannel, uri, u"deny"_ns);
return false;
}
// Step 9. If the X-Frame-Options value is SAMEORIGIN, then the top frame in
// the parent chain must be from the same origin as this document.
RefPtr<mozilla::dom::BrowsingContext> ctx;
loadInfo->GetBrowsingContext(getter_AddRefs(ctx));
while (ctx && xfoOptions.SAMEORIGIN) {
nsCOMPtr<nsIPrincipal> principal;
// Generally CheckFrameOptions is consulted from within the
// DocumentLoadListener in the parent process. For loads of type object and
// embed it's called from the Document in the content process.
if (XRE_IsParentProcess()) {
WindowGlobalParent* window = ctx->Canonical()->GetCurrentWindowGlobal();
if (window) {
// Using the URI of the Principal and not the document because
// window.open inherits the principal and hence the URI of the opening
// context needed for same origin checks.
principal = window->DocumentPrincipal();
}
} else if (nsPIDOMWindowOuter* windowOuter = ctx->GetDOMWindow()) {
principal = nsGlobalWindowOuter::Cast(windowOuter)->GetPrincipal();
}
if (principal && principal->IsSystemPrincipal()) {
return true;
}
// one of the ancestors is not same origin as this document
if (!principal || !principal->IsSameOrigin(uri)) {
ReportError("XFrameOptionsDeny", httpChannel, uri, u"sameorigin"_ns);
return false;
}
ctx = ctx->GetParent();
}
// Step 10.
return true;
}
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