breakpad/src/processor/exploitability_linux.cc

// Copyright (c) 2013 Google Inc.
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// exploitability_linux.cc: Linux specific exploitability engine.
//
// Provides a guess at the exploitability of the crash for the Linux
// platform given a minidump and process_state.
//
// Author: Matthew Riley

#include "processor/exploitability_linux.h"

#include "google_breakpad/processor/process_state.h"
#include "google_breakpad/processor/call_stack.h"
#include "google_breakpad/processor/stack_frame.h"
#include "processor/logging.h"

namespace {

// This function in libc is called if the program was compiled with
// -fstack-protector and a function's stack canary changes.
const char kStackCheckFailureFunction[] = "__stack_chk_fail";

// This function in libc is called if the program was compiled with
// -D_FORTIFY_SOURCE=2, a function like strcpy() is called, and the runtime
// can determine that the call would overflow the target buffer.
const char kBoundsCheckFailureFunction[] = "__chk_fail";

}  // namespace

namespace google_breakpad {

ExploitabilityLinux::ExploitabilityLinux(Minidump *dump,
                                         ProcessState *process_state)
    : Exploitability(dump, process_state) { }

ExploitabilityRating ExploitabilityLinux::CheckPlatformExploitability() {
  // Check the crashing thread for functions suggesting a buffer overflow or
  // stack smash.
  if (process_state_->requesting_thread() != -1) {
    CallStack* crashing_thread =
        process_state_->threads()->at(process_state_->requesting_thread());
    const vector<StackFrame*>& crashing_thread_frames =
        *crashing_thread->frames();
    for (size_t i = 0; i < crashing_thread_frames.size(); ++i) {
      if (crashing_thread_frames[i]->function_name ==
          kStackCheckFailureFunction) {
        return EXPLOITABILITY_HIGH;
      }

      if (crashing_thread_frames[i]->function_name ==
          kBoundsCheckFailureFunction) {
        return EXPLOITABILITY_HIGH;
      }
    }
  }

  // Check if the instruction pointer is in a valid instruction region
  // by finding if it maps to an executable part of memory.
  uint64_t instruction_ptr = 0;

  // Getting exception data. (It should exist for all minidumps.)
  MinidumpException *exception = dump_->GetException();
  if (exception == NULL) {
    BPLOG(INFO) << "No exception record.";
    return EXPLOITABILITY_ERR_PROCESSING;
  }
  const MinidumpContext *context = exception->GetContext();
  if (context == NULL) {
    BPLOG(INFO) << "No exception context.";
    return EXPLOITABILITY_ERR_PROCESSING;
  }

  // Getting instruction pointer based off architecture.
  uint32_t architecture = context->GetContextCPU();
  switch (architecture) {
    case MD_CONTEXT_X86:
      instruction_ptr = context->GetContextX86()->eip;
      break;
    case MD_CONTEXT_AMD64:
      instruction_ptr = context->GetContextAMD64()->rip;
      break;
    default:
      // TODO(liuandrew): Add support ARM and arm64 architectures.
      BPLOG(INFO) << "Unsupported architecture.";
      return EXPLOITABILITY_ERR_PROCESSING;
  }

  if (!this->InstructionPointerInCode(instruction_ptr)) {
    return EXPLOITABILITY_HIGH;
  }

  return EXPLOITABILITY_NONE;
}

bool ExploitabilityLinux::InstructionPointerInCode(uint64_t instruction_ptr) {
  // Here we get memory mapping. Most minidumps will not contain a memory
  // mapping, so we will commonly resort to checking modules.
  MinidumpMemoryInfoList *mem_info_list = dump_->GetMemoryInfoList();
  const MinidumpMemoryInfo *mem_info =
      mem_info_list ?
      mem_info_list->GetMemoryInfoForAddress(instruction_ptr) : NULL;

  // Checking if the memory mapping at the instruction pointer is executable.
  // If there is no memory mapping, we will use the modules as reference.
  if (mem_info != NULL) {
    return mem_info->IsExecutable();
  }

  // If the memory mapping retrieval fails, we will check the modules
  // to see if the instruction pointer is inside a module.
  // TODO(liuandrew): Check if the instruction pointer lies in an executable
  // region within the module.
  MinidumpModuleList *minidump_module_list = dump_->GetModuleList();
  return !minidump_module_list ||
          minidump_module_list->GetModuleForAddress(instruction_ptr);
}

}  // namespace google_breakpad