30 lines
1.6 KiB
Text
30 lines
1.6 KiB
Text
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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Index: lib/CodeGen/TargetPassConfig.cpp
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--- lib/CodeGen/TargetPassConfig.cpp.orig
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+++ lib/CodeGen/TargetPassConfig.cpp
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@@ -950,6 +950,8 @@ void TargetPassConfig::addISelPrepare() {
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if (requiresCodeGenSCCOrder())
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addPass(new DummyCGSCCPass);
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+ addPass(createReturnProtectorPass());
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+
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// Add both the safe stack and the stack protection passes: each of them will
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// only protect functions that have corresponding attributes.
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addPass(createSafeStackPass());
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