Index: syzygy/instrument/transforms/security_cookie_check_hook_transform.cc |
diff --git a/syzygy/instrument/transforms/security_cookie_check_hook_transform.cc b/syzygy/instrument/transforms/security_cookie_check_hook_transform.cc |
new file mode 100644 |
index 0000000000000000000000000000000000000000..d0e33448b79e0e853bd6d45d17bd74b9100fb974 |
--- /dev/null |
+++ b/syzygy/instrument/transforms/security_cookie_check_hook_transform.cc |
@@ -0,0 +1,109 @@ |
+// Copyright 2017 Google Inc. 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. |
+// |
+ |
+#include "syzygy/instrument/transforms/security_cookie_check_hook_transform.h" |
+ |
+#include "syzygy/pe/pe_utils.h" |
+ |
+namespace instrument { |
+namespace transforms { |
+ |
+using block_graph::Displacement; |
+using block_graph::Operand; |
+ |
+const char SecurityCookieCheckHookTransform::kTransformName[] = |
+ "SecurityCookieCheckHookTransform"; |
+ |
+const char SecurityCookieCheckHookTransform::kReportGsFailure[] = |
+ "__report_gsfailure"; |
+ |
+const char SecurityCookieCheckHookTransform::kSyzygyReportGsFailure[] = |
+ "__syzygy_report_gsfailure"; |
+ |
+const uint32_t SecurityCookieCheckHookTransform::kInvalidUserAddress = |
+ 0xdeadbeef; |
+ |
+bool SecurityCookieCheckHookTransform::TransformBlockGraph( |
+ const TransformPolicyInterface* policy, |
+ BlockGraph* block_graph, |
+ BlockGraph::Block* header_block) { |
+ BlockGraph::Block* report_gsfailure = nullptr; |
+ BlockGraph::BlockMap& blocks = block_graph->blocks_mutable(); |
+ for (auto& block : blocks) { |
+ std::string name(block.second.name()); |
+ if (name == kReportGsFailure) { |
+ report_gsfailure = &block.second; |
+ break; |
+ } |
+ } |
+ |
+ if (report_gsfailure == nullptr) { |
+ LOG(ERROR) << "Could not find " << kReportGsFailure << "."; |
+ return false; |
+ } |
+ |
+ if (report_gsfailure->referrers().size() != 1) { |
+ // We bail out if we don't have a single referrer as the only |
+ // expected referrer is supposed to be __security_cookie_check. |
+ // If there is more than one, we would rather bail out than take |
+ // a chance at modifying the behavior of the PE image. |
+ LOG(ERROR) << "Only a single referrer to " << kReportGsFailure |
+ << " is expected."; |
+ return false; |
+ } |
+ |
+ LOG(INFO) << "Found a " << kReportGsFailure |
+ << " implementation, hooking it now."; |
+ BlockGraph::Section* section_text = block_graph->FindOrAddSection( |
+ pe::kCodeSectionName, pe::kCodeCharacteristics); |
+ |
+ // All of the below is needed to build the instrumentation via the assembler. |
+ BasicBlockSubGraph bbsg; |
+ BasicBlockSubGraph::BlockDescription* block_desc = bbsg.AddBlockDescription( |
+ kSyzygyReportGsFailure, nullptr, BlockGraph::CODE_BLOCK, |
+ section_text->id(), 1, 0); |
+ |
+ BasicCodeBlock* bb = bbsg.AddBasicCodeBlock(kSyzygyReportGsFailure); |
+ block_desc->basic_block_order.push_back(bb); |
+ BasicBlockAssembler assm(bb->instructions().begin(), &bb->instructions()); |
+ assm.mov(Operand(Displacement(kInvalidUserAddress)), assm::eax); |
+ |
+ // Condense into a block. |
+ BlockBuilder block_builder(block_graph); |
+ if (!block_builder.Merge(&bbsg)) { |
+ LOG(ERROR) << "Failed to build " << kSyzygyReportGsFailure << " block."; |
+ return false; |
+ } |
+ |
+ DCHECK_EQ(1u, block_builder.new_blocks().size()); |
+ |
+ // Transfer the referrers to the new block, and delete the old one. |
+ BlockGraph::Block* syzygy_report_gsfailure = |
+ block_builder.new_blocks().front(); |
+ report_gsfailure->TransferReferrers( |
+ 0, syzygy_report_gsfailure, |
+ BlockGraph::Block::kTransferInternalReferences); |
+ |
+ report_gsfailure->RemoveAllReferences(); |
+ if (!block_graph->RemoveBlock(report_gsfailure)) { |
+ LOG(ERROR) << "Removing " << kReportGsFailure << " failed."; |
+ return false; |
+ } |
+ |
+ return true; |
+} |
+ |
+} // namespace transforms |
+} // namespace instrument |