The Tor Browser: security/sandbox/win/src/sidestep/preamble_patcher_with

security/sandbox/win/src/sidestep/preamble_patcher_with_stub.cpp@6474c204b198 (annotated)

security/sandbox/win/src/sidestep/preamble_patcher_with_stub.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 // Implementation of PreamblePatcher
 #include "sandbox/win/src/sidestep/preamble_patcher.h"
 #include "sandbox/win/src/sandbox_nt_util.h"
 #include "sandbox/win/src/sidestep/mini_disassembler.h"
 // Definitions of assembly statements we need
 #define ASM_JMP32REL 0xE9
 #define ASM_INT3 0xCC
 namespace {
 // Very basic memcpy. We are copying 4 to 12 bytes most of the time, so there
 // is no attempt to optimize this code or have a general purpose function.
 // We don't want to call the crt from this code.
 inline void* RawMemcpy(void* destination, const void* source, size_t bytes) {
   const char* from = reinterpret_cast<const char*>(source);
   char* to = reinterpret_cast<char*>(destination);
   for (size_t i = 0; i < bytes ; i++)
     to[i] = from[i];
   return destination;
 }
 // Very basic memset. We are filling 1 to 7 bytes most of the time, so there
 // is no attempt to optimize this code or have a general purpose function.
 // We don't want to call the crt from this code.
 inline void* RawMemset(void* destination, int value, size_t bytes) {
   char* to = reinterpret_cast<char*>(destination);
   for (size_t i = 0; i < bytes ; i++)
     to[i] = static_cast<char>(value);
   return destination;
 }
 }  // namespace
 #define ASSERT(a, b) DCHECK_NT(a)
 namespace sidestep {
 SideStepError PreamblePatcher::RawPatchWithStub(
     void* target_function,
     void* replacement_function,
     unsigned char* preamble_stub,
     size_t stub_size,
     size_t* bytes_needed) {
   if ((NULL == target_function) ||
       (NULL == replacement_function) ||
       (NULL == preamble_stub)) {
     ASSERT(false, (L"Invalid parameters - either pTargetFunction or "
                    L"pReplacementFunction or pPreambleStub were NULL."));
     return SIDESTEP_INVALID_PARAMETER;
   }
   // TODO(V7:joi) Siggi and I just had a discussion and decided that both
   // patching and unpatching are actually unsafe.  We also discussed a
   // method of making it safe, which is to freeze all other threads in the
   // process, check their thread context to see if their eip is currently
   // inside the block of instructions we need to copy to the stub, and if so
   // wait a bit and try again, then unfreeze all threads once we've patched.
   // Not implementing this for now since we're only using SideStep for unit
   // testing, but if we ever use it for production code this is what we
   // should do.
   //
   // NOTE: Stoyan suggests we can write 8 or even 10 bytes atomically using
   // FPU instructions, and on newer processors we could use cmpxchg8b or
   // cmpxchg16b. So it might be possible to do the patching/unpatching
   // atomically and avoid having to freeze other threads.  Note though, that
   // doing it atomically does not help if one of the other threads happens
   // to have its eip in the middle of the bytes you change while you change
   // them.
   unsigned char* target = reinterpret_cast<unsigned char*>(target_function);
   // Let's disassemble the preamble of the target function to see if we can
   // patch, and to see how much of the preamble we need to take.  We need 5
   // bytes for our jmp instruction, so let's find the minimum number of
   // instructions to get 5 bytes.
   MiniDisassembler disassembler;
   unsigned int preamble_bytes = 0;
   while (preamble_bytes < 5) {
     InstructionType instruction_type =
       disassembler.Disassemble(target + preamble_bytes, &preamble_bytes);
     if (IT_JUMP == instruction_type) {
       ASSERT(false, (L"Unable to patch because there is a jump instruction "
                      L"in the first 5 bytes."));
       return SIDESTEP_JUMP_INSTRUCTION;
     } else if (IT_RETURN == instruction_type) {
       ASSERT(false, (L"Unable to patch because function is too short"));
       return SIDESTEP_FUNCTION_TOO_SMALL;
     } else if (IT_GENERIC != instruction_type) {
       ASSERT(false, (L"Disassembler encountered unsupported instruction "
                      L"(either unused or unknown"));
       return SIDESTEP_UNSUPPORTED_INSTRUCTION;
     }
   }
   if (NULL != bytes_needed)
     *bytes_needed = preamble_bytes + 5;
   // Inv: preamble_bytes is the number of bytes (at least 5) that we need to
   // take from the preamble to have whole instructions that are 5 bytes or more
   // in size total. The size of the stub required is cbPreamble + size of
   // jmp (5)
   if (preamble_bytes + 5 > stub_size) {
     NOTREACHED_NT();
     return SIDESTEP_INSUFFICIENT_BUFFER;
   }
   // First, copy the preamble that we will overwrite.
   RawMemcpy(reinterpret_cast<void*>(preamble_stub),
             reinterpret_cast<void*>(target), preamble_bytes);
   // Now, make a jmp instruction to the rest of the target function (minus the
   // preamble bytes we moved into the stub) and copy it into our preamble-stub.
   // find address to jump to, relative to next address after jmp instruction
 #pragma warning(push)
 #pragma warning(disable:4244)
   // This assignment generates a warning because it is 32 bit specific.
   int relative_offset_to_target_rest
     = ((reinterpret_cast<unsigned char*>(target) + preamble_bytes) -
         (preamble_stub + preamble_bytes + 5));
 #pragma warning(pop)
   // jmp (Jump near, relative, displacement relative to next instruction)
   preamble_stub[preamble_bytes] = ASM_JMP32REL;
   // copy the address
   RawMemcpy(reinterpret_cast<void*>(preamble_stub + preamble_bytes + 1),
             reinterpret_cast<void*>(&relative_offset_to_target_rest), 4);
   // Inv: preamble_stub points to assembly code that will execute the
   // original function by first executing the first cbPreamble bytes of the
   // preamble, then jumping to the rest of the function.
   // Overwrite the first 5 bytes of the target function with a jump to our
   // replacement function.
   // (Jump near, relative, displacement relative to next instruction)
   target[0] = ASM_JMP32REL;
   // Find offset from instruction after jmp, to the replacement function.
 #pragma warning(push)
 #pragma warning(disable:4244)
   int offset_to_replacement_function =
     reinterpret_cast<unsigned char*>(replacement_function) -
     reinterpret_cast<unsigned char*>(target) - 5;
 #pragma warning(pop)
   // complete the jmp instruction
   RawMemcpy(reinterpret_cast<void*>(target + 1),
             reinterpret_cast<void*>(&offset_to_replacement_function), 4);
   // Set any remaining bytes that were moved to the preamble-stub to INT3 so
   // as not to cause confusion (otherwise you might see some strange
   // instructions if you look at the disassembly, or even invalid
   // instructions). Also, by doing this, we will break into the debugger if
   // some code calls into this portion of the code.  If this happens, it
   // means that this function cannot be patched using this patcher without
   // further thought.
   if (preamble_bytes > 5) {
     RawMemset(reinterpret_cast<void*>(target + 5), ASM_INT3,
               preamble_bytes - 5);
   }
   // Inv: The memory pointed to by target_function now points to a relative
   // jump instruction that jumps over to the preamble_stub.  The preamble
   // stub contains the first stub_size bytes of the original target
   // function's preamble code, followed by a relative jump back to the next
   // instruction after the first cbPreamble bytes.
   return SIDESTEP_SUCCESS;
 }
 };  // namespace sidestep
 #undef ASSERT

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security/sandbox/win/src/sidestep/preamble_patcher_with_stub.cpp@6474c204b198 (annotated)

security/sandbox/win/src/sidestep/preamble_patcher_with_stub.cpp