1 files changed, 458 insertions, 0 deletions
diff --git a/js/xpconnect/wrappers/AccessCheck.cpp b/js/xpconnect/wrappers/AccessCheck.cpp
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+++ b/js/xpconnect/wrappers/AccessCheck.cpp
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=4 et sw=4 tw=99: */
+/* 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 "AccessCheck.h"
+
+#include "nsJSPrincipals.h"
+#include "nsGlobalWindow.h"
+
+#include "XPCWrapper.h"
+#include "XrayWrapper.h"
+#include "FilteringWrapper.h"
+
+#include "jsfriendapi.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/LocationBinding.h"
+#include "mozilla/dom/WindowBinding.h"
+#include "mozilla/jsipc/CrossProcessObjectWrappers.h"
+#include "nsIDOMWindowCollection.h"
+#include "nsJSUtils.h"
+#include "xpcprivate.h"
+
+using namespace mozilla;
+using namespace JS;
+using namespace js;
+
+namespace xpc {
+
+nsIPrincipal*
+GetCompartmentPrincipal(JSCompartment* compartment)
+{
+    return nsJSPrincipals::get(JS_GetCompartmentPrincipals(compartment));
+}
+
+nsIPrincipal*
+GetObjectPrincipal(JSObject* obj)
+{
+    return GetCompartmentPrincipal(js::GetObjectCompartment(obj));
+}
+
+// Does the principal of compartment a subsume the principal of compartment b?
+bool
+AccessCheck::subsumes(JSCompartment* a, JSCompartment* b)
+{
+    nsIPrincipal* aprin = GetCompartmentPrincipal(a);
+    nsIPrincipal* bprin = GetCompartmentPrincipal(b);
+    return aprin->Subsumes(bprin);
+}
+
+bool
+AccessCheck::subsumes(JSObject* a, JSObject* b)
+{
+    return subsumes(js::GetObjectCompartment(a), js::GetObjectCompartment(b));
+}
+
+// Same as above, but considering document.domain.
+bool
+AccessCheck::subsumesConsideringDomain(JSCompartment* a, JSCompartment* b)
+{
+    nsIPrincipal* aprin = GetCompartmentPrincipal(a);
+    nsIPrincipal* bprin = GetCompartmentPrincipal(b);
+    return aprin->SubsumesConsideringDomain(bprin);
+}
+
+// Does the compartment of the wrapper subsumes the compartment of the wrappee?
+bool
+AccessCheck::wrapperSubsumes(JSObject* wrapper)
+{
+    MOZ_ASSERT(js::IsWrapper(wrapper));
+    JSObject* wrapped = js::UncheckedUnwrap(wrapper);
+    return AccessCheck::subsumes(js::GetObjectCompartment(wrapper),
+                                 js::GetObjectCompartment(wrapped));
+}
+
+bool
+AccessCheck::isChrome(JSCompartment* compartment)
+{
+    bool privileged;
+    nsIPrincipal* principal = GetCompartmentPrincipal(compartment);
+    return NS_SUCCEEDED(nsXPConnect::SecurityManager()->IsSystemPrincipal(principal, &privileged)) && privileged;
+}
+
+bool
+AccessCheck::isChrome(JSObject* obj)
+{
+    return isChrome(js::GetObjectCompartment(obj));
+}
+
+nsIPrincipal*
+AccessCheck::getPrincipal(JSCompartment* compartment)
+{
+    return GetCompartmentPrincipal(compartment);
+}
+
+// Hardcoded policy for cross origin property access. See the HTML5 Spec.
+static bool
+IsPermitted(CrossOriginObjectType type, JSFlatString* prop, bool set)
+{
+    size_t propLength = JS_GetStringLength(JS_FORGET_STRING_FLATNESS(prop));
+    if (!propLength)
+        return false;
+
+    char16_t propChar0 = JS_GetFlatStringCharAt(prop, 0);
+    if (type == CrossOriginLocation)
+        return dom::LocationBinding::IsPermitted(prop, propChar0, set);
+    if (type == CrossOriginWindow)
+        return dom::WindowBinding::IsPermitted(prop, propChar0, set);
+
+    return false;
+}
+
+static bool
+IsFrameId(JSContext* cx, JSObject* obj, jsid idArg)
+{
+    MOZ_ASSERT(!js::IsWrapper(obj));
+    RootedId id(cx, idArg);
+
+    nsGlobalWindow* win = WindowOrNull(obj);
+    if (!win) {
+        return false;
+    }
+
+    nsCOMPtr<nsIDOMWindowCollection> col = win->GetFrames();
+    if (!col) {
+        return false;
+    }
+
+    nsCOMPtr<mozIDOMWindowProxy> domwin;
+    if (JSID_IS_INT(id)) {
+        col->Item(JSID_TO_INT(id), getter_AddRefs(domwin));
+    } else if (JSID_IS_STRING(id)) {
+        nsAutoJSString idAsString;
+        if (!idAsString.init(cx, JSID_TO_STRING(id))) {
+            return false;
+        }
+        col->NamedItem(idAsString, getter_AddRefs(domwin));
+    }
+
+    return domwin != nullptr;
+}
+
+CrossOriginObjectType
+IdentifyCrossOriginObject(JSObject* obj)
+{
+    obj = js::UncheckedUnwrap(obj, /* stopAtWindowProxy = */ false);
+    const js::Class* clasp = js::GetObjectClass(obj);
+    MOZ_ASSERT(!XrayUtils::IsXPCWNHolderClass(Jsvalify(clasp)), "shouldn't have a holder here");
+
+    if (clasp->name[0] == 'L' && !strcmp(clasp->name, "Location"))
+        return CrossOriginLocation;
+    if (clasp->name[0] == 'W' && !strcmp(clasp->name, "Window"))
+        return CrossOriginWindow;
+
+    return CrossOriginOpaque;
+}
+
+bool
+AccessCheck::isCrossOriginAccessPermitted(JSContext* cx, HandleObject wrapper, HandleId id,
+                                          Wrapper::Action act)
+{
+    if (act == Wrapper::CALL)
+        return false;
+
+    if (act == Wrapper::ENUMERATE)
+        return true;
+
+    // For the case of getting a property descriptor, we allow if either GET or SET
+    // is allowed, and rely on FilteringWrapper to filter out any disallowed accessors.
+    if (act == Wrapper::GET_PROPERTY_DESCRIPTOR) {
+        return isCrossOriginAccessPermitted(cx, wrapper, id, Wrapper::GET) ||
+               isCrossOriginAccessPermitted(cx, wrapper, id, Wrapper::SET);
+    }
+
+    RootedObject obj(cx, js::UncheckedUnwrap(wrapper, /* stopAtWindowProxy = */ false));
+    CrossOriginObjectType type = IdentifyCrossOriginObject(obj);
+    if (JSID_IS_STRING(id)) {
+        if (IsPermitted(type, JSID_TO_FLAT_STRING(id), act == Wrapper::SET))
+            return true;
+    } else if (type != CrossOriginOpaque &&
+               IsCrossOriginWhitelistedSymbol(cx, id)) {
+        // We always allow access to @@toStringTag, @@hasInstance, and
+        // @@isConcatSpreadable.  But then we nerf them to be a value descriptor
+        // with value undefined in CrossOriginXrayWrapper.
+        return true;
+    }
+
+    if (act != Wrapper::GET)
+        return false;
+
+    // Check for frame IDs. If we're resolving named frames, make sure to only
+    // resolve ones that don't shadow native properties. See bug 860494.
+    if (type == CrossOriginWindow) {
+        if (JSID_IS_STRING(id)) {
+            bool wouldShadow = false;
+            if (!XrayUtils::HasNativeProperty(cx, wrapper, id, &wouldShadow) ||
+                wouldShadow)
+            {
+                // If the named subframe matches the name of a DOM constructor,
+                // the global resolve triggered by the HasNativeProperty call
+                // above will try to perform a CheckedUnwrap on |wrapper|, and
+                // throw a security error if it fails. That exception isn't
+                // really useful for our callers, so we silence it and just
+                // deny access to the property (since it matched a builtin).
+                //
+                // Note that this would be a problem if the resolve code ever
+                // tried to CheckedUnwrap the wrapper _before_ concluding that
+                // the name corresponds to a builtin global property, since it
+                // would mean that we'd never permit cross-origin named subframe
+                // access (something we regrettably need to support).
+                JS_ClearPendingException(cx);
+                return false;
+            }
+        }
+        return IsFrameId(cx, obj, id);
+    }
+    return false;
+}
+
+bool
+AccessCheck::checkPassToPrivilegedCode(JSContext* cx, HandleObject wrapper, HandleValue v)
+{
+    // Primitives are fine.
+    if (!v.isObject())
+        return true;
+    RootedObject obj(cx, &v.toObject());
+
+    // Non-wrappers are fine.
+    if (!js::IsWrapper(obj))
+        return true;
+
+    // CPOWs use COWs (in the unprivileged junk scope) for all child->parent
+    // references. Without this test, the child process wouldn't be able to
+    // pass any objects at all to CPOWs.
+    if (mozilla::jsipc::IsWrappedCPOW(obj) &&
+        js::GetObjectCompartment(wrapper) == js::GetObjectCompartment(xpc::UnprivilegedJunkScope()) &&
+        XRE_IsParentProcess())
+    {
+        return true;
+    }
+
+    // COWs are fine to pass to chrome if and only if they have __exposedProps__,
+    // since presumably content should never have a reason to pass an opaque
+    // object back to chrome.
+    if (AccessCheck::isChrome(js::UncheckedUnwrap(wrapper)) && WrapperFactory::IsCOW(obj)) {
+        RootedObject target(cx, js::UncheckedUnwrap(obj));
+        JSAutoCompartment ac(cx, target);
+        RootedId id(cx, GetJSIDByIndex(cx, XPCJSContext::IDX_EXPOSEDPROPS));
+        bool found = false;
+        if (!JS_HasPropertyById(cx, target, id, &found))
+            return false;
+        if (found)
+            return true;
+    }
+
+    // Same-origin wrappers are fine.
+    if (AccessCheck::wrapperSubsumes(obj))
+        return true;
+
+    // Badness.
+    JS_ReportErrorASCII(cx, "Permission denied to pass object to privileged code");
+    return false;
+}
+
+bool
+AccessCheck::checkPassToPrivilegedCode(JSContext* cx, HandleObject wrapper, const CallArgs& args)
+{
+    if (!checkPassToPrivilegedCode(cx, wrapper, args.thisv()))
+        return false;
+    for (size_t i = 0; i < args.length(); ++i) {
+        if (!checkPassToPrivilegedCode(cx, wrapper, args[i]))
+            return false;
+    }
+    return true;
+}
+
+enum Access { READ = (1<<0), WRITE = (1<<1), NO_ACCESS = 0 };
+
+static void
+EnterAndThrowASCII(JSContext* cx, JSObject* wrapper, const char* msg)
+{
+    JSAutoCompartment ac(cx, wrapper);
+    JS_ReportErrorASCII(cx, "%s", msg);
+}
+
+bool
+ExposedPropertiesOnly::check(JSContext* cx, HandleObject wrapper, HandleId id, Wrapper::Action act)
+{
+    RootedObject wrappedObject(cx, Wrapper::wrappedObject(wrapper));
+
+    if (act == Wrapper::CALL)
+        return false;
+
+    // For the case of getting a property descriptor, we allow if either GET or SET
+    // is allowed, and rely on FilteringWrapper to filter out any disallowed accessors.
+    if (act == Wrapper::GET_PROPERTY_DESCRIPTOR) {
+        return check(cx, wrapper, id, Wrapper::GET) ||
+               check(cx, wrapper, id, Wrapper::SET);
+    }
+
+    RootedId exposedPropsId(cx, GetJSIDByIndex(cx, XPCJSContext::IDX_EXPOSEDPROPS));
+
+    // We need to enter the wrappee's compartment to look at __exposedProps__,
+    // but we want to be in the wrapper's compartment if we call Deny().
+    //
+    // Unfortunately, |cx| can be in either compartment when we call ::check. :-(
+    JSAutoCompartment ac(cx, wrappedObject);
+
+    bool found = false;
+    if (!JS_HasPropertyById(cx, wrappedObject, exposedPropsId, &found))
+        return false;
+
+    // If no __exposedProps__ existed, deny access.
+    if (!found) {
+        // Previously we automatically granted access to indexed properties and
+        // .length for Array COWs. We're not doing that anymore, so make sure to
+        // let people know what's going on.
+        bool isArray;
+        if (!JS_IsArrayObject(cx, wrappedObject, &isArray))
+            return false;
+        if (!isArray)
+            isArray = JS_IsTypedArrayObject(wrappedObject);
+        bool isIndexedAccessOnArray = isArray && JSID_IS_INT(id) && JSID_TO_INT(id) >= 0;
+        bool isLengthAccessOnArray = isArray && JSID_IS_STRING(id) &&
+                                     JS_FlatStringEqualsAscii(JSID_TO_FLAT_STRING(id), "length");
+        if (isIndexedAccessOnArray || isLengthAccessOnArray) {
+            JSAutoCompartment ac2(cx, wrapper);
+            ReportWrapperDenial(cx, id, WrapperDenialForCOW,
+                                "Access to elements and length of privileged Array not permitted");
+        }
+
+        return false;
+    }
+
+    if (id == JSID_VOID)
+        return true;
+
+    Rooted<PropertyDescriptor> desc(cx);
+    if (!JS_GetPropertyDescriptorById(cx, wrappedObject, exposedPropsId, &desc))
+        return false;
+
+    if (!desc.object())
+        return false;
+
+    if (desc.hasGetterOrSetter()) {
+        EnterAndThrowASCII(cx, wrapper, "__exposedProps__ must be a value property");
+        return false;
+    }
+
+    RootedValue exposedProps(cx, desc.value());
+    if (exposedProps.isNullOrUndefined())
+        return false;
+
+    if (!exposedProps.isObject()) {
+        EnterAndThrowASCII(cx, wrapper, "__exposedProps__ must be undefined, null, or an Object");
+        return false;
+    }
+
+    RootedObject hallpass(cx, &exposedProps.toObject());
+
+    if (!AccessCheck::subsumes(js::UncheckedUnwrap(hallpass), wrappedObject)) {
+        EnterAndThrowASCII(cx, wrapper, "Invalid __exposedProps__");
+        return false;
+    }
+
+    Access access = NO_ACCESS;
+
+    if (!JS_GetPropertyDescriptorById(cx, hallpass, id, &desc)) {
+        return false; // Error
+    }
+    if (!desc.object() || !desc.enumerable())
+        return false;
+
+    if (!desc.value().isString()) {
+        EnterAndThrowASCII(cx, wrapper, "property must be a string");
+        return false;
+    }
+
+    JSFlatString* flat = JS_FlattenString(cx, desc.value().toString());
+    if (!flat)
+        return false;
+
+    size_t length = JS_GetStringLength(JS_FORGET_STRING_FLATNESS(flat));
+
+    for (size_t i = 0; i < length; ++i) {
+        char16_t ch = JS_GetFlatStringCharAt(flat, i);
+        switch (ch) {
+        case 'r':
+            if (access & READ) {
+                EnterAndThrowASCII(cx, wrapper, "duplicate 'readable' property flag");
+                return false;
+            }
+            access = Access(access | READ);
+            break;
+
+        case 'w':
+            if (access & WRITE) {
+                EnterAndThrowASCII(cx, wrapper, "duplicate 'writable' property flag");
+                return false;
+            }
+            access = Access(access | WRITE);
+            break;
+
+        default:
+            EnterAndThrowASCII(cx, wrapper, "properties can only be readable or read and writable");
+            return false;
+        }
+    }
+
+    if (access == NO_ACCESS) {
+        EnterAndThrowASCII(cx, wrapper, "specified properties must have a permission bit set");
+        return false;
+    }
+
+    if ((act == Wrapper::SET && !(access & WRITE)) ||
+        (act != Wrapper::SET && !(access & READ))) {
+        return false;
+    }
+
+    // Inspect the property on the underlying object to check for red flags.
+    if (!JS_GetPropertyDescriptorById(cx, wrappedObject, id, &desc))
+        return false;
+
+    // Reject accessor properties.
+    if (desc.hasGetterOrSetter()) {
+        EnterAndThrowASCII(cx, wrapper, "Exposing privileged accessor properties is prohibited");
+        return false;
+    }
+
+    // Reject privileged or cross-origin callables.
+    if (desc.value().isObject()) {
+        RootedObject maybeCallable(cx, js::UncheckedUnwrap(&desc.value().toObject()));
+        if (JS::IsCallable(maybeCallable) && !AccessCheck::subsumes(wrapper, maybeCallable)) {
+            EnterAndThrowASCII(cx, wrapper, "Exposing privileged or cross-origin callable is prohibited");
+            return false;
+        }
+    }
+
+    return true;
+}
+
+bool
+ExposedPropertiesOnly::deny(js::Wrapper::Action act, HandleId id)
+{
+    // Fail silently for GET, ENUMERATE, and GET_PROPERTY_DESCRIPTOR.
+    if (act == js::Wrapper::GET || act == js::Wrapper::ENUMERATE ||
+        act == js::Wrapper::GET_PROPERTY_DESCRIPTOR)
+    {
+        AutoJSContext cx;
+        return ReportWrapperDenial(cx, id, WrapperDenialForCOW,
+                                   "Access to privileged JS object not permitted");
+    }
+
+    return false;
+}
+
+} // namespace xpc