handler/mac: Log a warning when an exception message has a suspicious

util/mach/mach_message.h

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #ifndef CRASHPAD_UTIL_MACH_MACH_MESSAGE_H_
 #define CRASHPAD_UTIL_MACH_MACH_MESSAGE_H_
 
 #include <mach/mach.h>
 #include <stdint.h>
+#include <sys/types.h>
 
 namespace crashpad {
 
+//! \brief A Mach message option specifying that an audit trailer should be
+//!     delivered during a receive operation.
+//!
+//! This constant is provided because the macros normally used to request this
+//! behavior are cumbersome.
+const mach_msg_option_t kMachMessageReceiveAuditTrailer =
+    MACH_RCV_TRAILER_TYPE(MACH_MSG_TRAILER_FORMAT_0) |
+    MACH_RCV_TRAILER_ELEMENTS(MACH_RCV_TRAILER_AUDIT);
+
 //! \brief Special constants used as `mach_msg_timeout_t` values.
 enum : mach_msg_timeout_t {
   //! \brief When passed to MachMessageDeadlineFromTimeout(), that function will
   //!     return #kMachMessageDeadlineNonblocking.
   kMachMessageTimeoutNonblocking = 0,
 
   //! \brief When passed to MachMessageDeadlineFromTimeout(), that function will
   //!     return #kMachMessageDeadlineWaitIndefinitely.
   kMachMessageTimeoutWaitIndefinitely = 0xffffffff,
 };
@@ skipping 108 matching lines @@
 //! for sending do not contain trailers.
 //!
 //! \param[in] header A pointer to a received Mach message.
 //!
 //! \return A pointer to the trailer following the received Mach message’s body.
 //!     The contents of the trailer depend on the options provided to
 //!     `mach_msg()` or a similar function when the message was received.
 const mach_msg_trailer_t* MachMessageTrailerFromHeader(
     const mach_msg_header_t* header);
 
+//! \brief Returns the process ID of a Mach message’s sender from its audit
+//!     trailer.
+//!
+//! For the audit trailer to be present, the message must have been received
+//! with #kMachMessageReceiveAuditTrailer or its macro equivalent specified in
+//! the receive options.
+//!
+//! If the kernel is the message’s sender, a process ID of `0` will be returned.
+//!
+//! \param[in] trailer The trailer received with a Mach message.
+//!
+//! \return The process ID of the message’s sender, or `-1` on failure with a
+//!     message logged. It is considered a failure for \a trailer to not contain
+//!     audit information.
+pid_t AuditPIDFromMachMessageTrailer(const mach_msg_trailer_t* trailer);
+
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_MACH_MACH_MESSAGE_H_