blob: 30cff76f08b5350555235e2a2c8a46d919687474 [file] [log] [blame]
// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <lib/fidl/coding.h>
#include <lib/fidl/envelope_frames.h>
#include <lib/fidl/internal.h>
#include <lib/fidl/visitor.h>
#include <lib/fidl/walker.h>
#include <stdalign.h>
#include <zircon/assert.h>
#include <zircon/compiler.h>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#ifdef __Fuchsia__
#include <zircon/syscalls.h>
#endif
// TODO(kulakowski) Design zx_status_t error values.
namespace {
struct Position;
struct StartingPoint {
uint8_t* const addr;
Position ToPosition() const;
};
struct Position {
uint32_t offset;
Position operator+(uint32_t size) const { return Position{offset + size}; }
Position& operator+=(uint32_t size) {
offset += size;
return *this;
}
template <typename T>
constexpr T* Get(StartingPoint start) const {
return reinterpret_cast<T*>(start.addr + offset);
}
};
Position StartingPoint::ToPosition() const { return Position{0}; }
constexpr uintptr_t kAllocPresenceMarker = FIDL_ALLOC_PRESENT;
constexpr uintptr_t kAllocAbsenceMarker = FIDL_ALLOC_ABSENT;
using EnvelopeState = ::fidl::EnvelopeFrames::EnvelopeState;
class FidlDecoder final
: public fidl::Visitor<fidl::MutatingVisitorTrait, StartingPoint, Position> {
public:
FidlDecoder(void* bytes, uint32_t num_bytes, const zx_handle_t* handles, uint32_t num_handles,
uint32_t next_out_of_line, const char** out_error_msg)
: bytes_(static_cast<uint8_t*>(bytes)),
num_bytes_(num_bytes),
handles_(handles),
num_handles_(num_handles),
next_out_of_line_(next_out_of_line),
out_error_msg_(out_error_msg) {}
using StartingPoint = StartingPoint;
using Position = Position;
static constexpr bool kContinueAfterConstraintViolation = false;
static constexpr bool kAllowNonNullableCollectionsToBeAbsent = false;
Status VisitPointer(Position ptr_position, ObjectPointerPointer object_ptr_ptr,
uint32_t inline_size, Position* out_position) {
if (reinterpret_cast<uintptr_t>(*object_ptr_ptr) != kAllocPresenceMarker) {
SetError("decoder encountered invalid pointer");
return Status::kConstraintViolationError;
}
uint32_t new_offset;
if (!fidl::AddOutOfLine(next_out_of_line_, inline_size, &new_offset)) {
SetError("overflow updating out-of-line offset");
return Status::kMemoryError;
}
if (new_offset > num_bytes_) {
SetError("message tried to decode more than provided number of bytes");
return Status::kMemoryError;
}
auto status = ValidatePadding(&bytes_[next_out_of_line_ + inline_size],
new_offset - next_out_of_line_ - inline_size);
if (status != Status::kSuccess) {
return status;
}
*out_position = Position{next_out_of_line_};
*object_ptr_ptr = reinterpret_cast<void*>(&bytes_[next_out_of_line_]);
next_out_of_line_ = new_offset;
return Status::kSuccess;
}
Status VisitHandle(Position handle_position, HandlePointer handle) {
if (*handle != FIDL_HANDLE_PRESENT) {
SetError("message tried to decode a garbage handle");
return Status::kConstraintViolationError;
}
if (handle_idx_ == num_handles_) {
SetError("message decoded too many handles");
return Status::kConstraintViolationError;
}
if (handles_ == nullptr) {
SetError("decoder noticed a handle is present but the handle table is empty");
*handle = ZX_HANDLE_INVALID;
return Status::kConstraintViolationError;
}
if (handles_[handle_idx_] == ZX_HANDLE_INVALID) {
SetError("invalid handle detected in handle table");
return Status::kConstraintViolationError;
}
*handle = handles_[handle_idx_];
handle_idx_++;
return Status::kSuccess;
}
Status VisitInternalPadding(Position padding_position, uint32_t padding_length) {
auto padding_ptr = padding_position.template Get<const uint8_t>(StartingPoint{bytes_});
return ValidatePadding(padding_ptr, padding_length);
}
Status EnterEnvelope(Position envelope_position, EnvelopePointer envelope,
const fidl_type_t* payload_type) {
if (envelope->presence == kAllocAbsenceMarker &&
(envelope->num_bytes != 0 || envelope->num_handles != 0)) {
SetError("Envelope has absent data pointer, yet has data and/or handles");
return Status::kConstraintViolationError;
}
if (envelope->presence != kAllocAbsenceMarker && envelope->num_bytes == 0) {
SetError("Envelope has present data pointer, but zero byte count");
return Status::kConstraintViolationError;
}
uint32_t expected_handle_count;
if (add_overflow(handle_idx_, envelope->num_handles, &expected_handle_count) ||
expected_handle_count > num_handles_) {
SetError("Envelope has more handles than expected");
return Status::kConstraintViolationError;
}
// Remember the current watermark of bytes and handles, so that after processing
// the envelope, we can validate that the claimed num_bytes/num_handles matches the reality.
if (!envelope_frames_.Push(EnvelopeState(next_out_of_line_, handle_idx_))) {
SetError("Overly deep nested envelopes");
return Status::kConstraintViolationError;
}
// If we do not have the coding table for this payload,
// treat it as unknown and close its contained handles
if (envelope->presence != kAllocAbsenceMarker && payload_type == nullptr &&
envelope->num_handles > 0) {
memcpy(&unknown_handles_[unknown_handle_idx_], &handles_[handle_idx_],
envelope->num_handles * sizeof(zx_handle_t));
handle_idx_ += envelope->num_handles;
unknown_handle_idx_ += envelope->num_handles;
}
return Status::kSuccess;
}
Status LeaveEnvelope(Position envelope_position, EnvelopePointer envelope) {
// Now that the envelope has been consumed, check the correctness of the envelope header.
auto& starting_state = envelope_frames_.Pop();
uint32_t num_bytes = next_out_of_line_ - starting_state.bytes_so_far;
uint32_t num_handles = handle_idx_ - starting_state.handles_so_far;
if (envelope->num_bytes != num_bytes) {
SetError("Envelope num_bytes was mis-sized");
return Status::kConstraintViolationError;
}
if (envelope->num_handles != num_handles) {
SetError("Envelope num_handles was mis-sized");
return Status::kConstraintViolationError;
}
return Status::kSuccess;
}
void OnError(const char* error) { SetError(error); }
zx_status_t status() const { return status_; }
bool DidConsumeAllBytes() const { return next_out_of_line_ == num_bytes_; }
bool DidConsumeAllHandles() const { return handle_idx_ == num_handles_; }
uint32_t unknown_handle_idx() const { return unknown_handle_idx_; }
const zx_handle_t* unknown_handles() const { return unknown_handles_; }
private:
void SetError(const char* error) {
if (status_ != ZX_OK) {
return;
}
status_ = ZX_ERR_INVALID_ARGS;
if (!out_error_msg_) {
return;
}
*out_error_msg_ = error;
}
Status ValidatePadding(const uint8_t* padding_ptr, uint32_t padding_length) {
for (uint32_t i = 0; i < padding_length; i++) {
if (padding_ptr[i] != 0) {
SetError("non-zero padding bytes detected");
return Status::kConstraintViolationError;
}
}
return Status::kSuccess;
}
// Message state passed in to the constructor.
uint8_t* const bytes_;
const uint32_t num_bytes_;
const zx_handle_t* const handles_;
const uint32_t num_handles_;
uint32_t next_out_of_line_;
const char** const out_error_msg_;
// Decoder state
zx_status_t status_ = ZX_OK;
uint32_t handle_idx_ = 0;
uint32_t unknown_handle_idx_ = 0;
zx_handle_t unknown_handles_[ZX_CHANNEL_MAX_MSG_HANDLES];
fidl::EnvelopeFrames envelope_frames_;
};
} // namespace
zx_status_t fidl_decode(const fidl_type_t* type, void* bytes, uint32_t num_bytes,
const zx_handle_t* handles, uint32_t num_handles,
const char** out_error_msg) {
auto drop_all_handles = [&]() {
#ifdef __Fuchsia__
// Return value intentionally ignored. This is best-effort cleanup.
(void)zx_handle_close_many(handles, num_handles);
#endif
};
auto set_error = [&out_error_msg](const char* msg) {
if (out_error_msg)
*out_error_msg = msg;
};
if (handles == nullptr && num_handles != 0) {
set_error("Cannot provide non-zero handle count and null handle pointer");
return ZX_ERR_INVALID_ARGS;
}
if (bytes == nullptr) {
set_error("Cannot decode null bytes");
drop_all_handles();
return ZX_ERR_INVALID_ARGS;
}
if (!fidl::IsAligned(reinterpret_cast<uint8_t*>(bytes))) {
set_error("Bytes must be aligned to FIDL_ALIGNMENT");
drop_all_handles();
return ZX_ERR_INVALID_ARGS;
}
uint32_t next_out_of_line;
zx_status_t status;
if ((status = fidl::StartingOutOfLineOffset(type, num_bytes, &next_out_of_line, out_error_msg)) !=
ZX_OK) {
drop_all_handles();
return status;
}
FidlDecoder decoder(bytes, num_bytes, handles, num_handles, next_out_of_line, out_error_msg);
fidl::Walk(decoder, type, StartingPoint{reinterpret_cast<uint8_t*>(bytes)});
if (decoder.status() != ZX_OK) {
drop_all_handles();
return decoder.status();
}
if (!decoder.DidConsumeAllBytes()) {
set_error("message did not decode all provided bytes");
drop_all_handles();
return ZX_ERR_INVALID_ARGS;
}
if (!decoder.DidConsumeAllHandles()) {
set_error("message did not decode all provided handles");
drop_all_handles();
return ZX_ERR_INVALID_ARGS;
}
#ifdef __Fuchsia__
if (decoder.unknown_handle_idx() > 0) {
(void)zx_handle_close_many(decoder.unknown_handles(), decoder.unknown_handle_idx());
}
#endif
return ZX_OK;
}
zx_status_t fidl_decode_msg(const fidl_type_t* type, fidl_msg_t* msg, const char** out_error_msg) {
return fidl_decode(type, msg->bytes, msg->num_bytes, msg->handles, msg->num_handles,
out_error_msg);
}