42 lines
2.1 KiB
Plaintext
42 lines
2.1 KiB
Plaintext
- Add RETGUARD to clang for amd64. This security mechanism uses per-function
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random cookies to protect access to function return instructions, with the
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effect that the integrity of the return address is protected, and function
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return instructions are harder to use in ROP gadgets.
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On function entry the return address is combined with a per-function random
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cookie and stored in the stack frame. The integrity of this value is verified
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before function return, and if this check fails, the program aborts. In this way
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RETGUARD is an improved stack protector, since the cookies are per-function. The
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verification routine is constructed such that the binary space immediately
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before each ret instruction is padded with int03 instructions, which makes these
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return instructions difficult to use in ROP gadgets. In the kernel, this has the
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effect of removing approximately 50% of total ROP gadgets, and 15% of unique
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ROP gadgets compared to the 6.3 release kernel. Function epilogues are
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essentially gadget free, leaving only the polymorphic gadgets that result from
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jumping into the instruction stream partway through other instructions. Work to
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remove these gadgets will continue through other mechanisms.
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- Refactor retguard to make adding additional arches easier.
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Index: include/llvm/CodeGen/TargetFrameLowering.h
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--- include/llvm/CodeGen/TargetFrameLowering.h.orig
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+++ include/llvm/CodeGen/TargetFrameLowering.h
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@@ -14,6 +14,7 @@
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#define LLVM_CODEGEN_TARGETFRAMELOWERING_H
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#include "llvm/CodeGen/MachineBasicBlock.h"
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+#include "llvm/CodeGen/ReturnProtectorLowering.h"
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#include "llvm/Support/TypeSize.h"
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#include <vector>
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@@ -209,6 +210,10 @@ class TargetFrameLowering { (public)
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MachineBasicBlock &MBB) const = 0;
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virtual void emitEpilogue(MachineFunction &MF,
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MachineBasicBlock &MBB) const = 0;
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+
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+ virtual const ReturnProtectorLowering *getReturnProtector() const {
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+ return nullptr;
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+ }
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/// With basic block sections, emit callee saved frame moves for basic blocks
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/// that are in a different section.
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