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Unified Diff: syzygy/instrument/transforms/security_cookie_check_hook_transform.cc

Issue 2871863002: adds the security cookie check hook transform. (Closed)
Patch Set: removed the DCHECK_EQ Created 3 years, 7 months ago
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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

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