[RFC 00/12] Introduce struct layout randomization feature

[Connor Kuehl via cfe-commits]

This patch set introduces structure field layout randomization into the Clang
compiler. The Randstruct feature is a compile-time hardening technique that 
randomizes the field layout for designated structures of a code base. 
Admittedly, this is mostly useful for closed-source releases of code (since 
the randomization seed would be available for public and open source application
s). However, this patch set also enhances Clang’s feature parity with that 
of GCC which already has the Randstruct feature.

This patch set is a from-scratch reimplementation of the Randstruct feature 
that was originally ported to GCC. The patches for this implementation in GCC 
can be found here: 

    https://www.openwall.com/lists/kernel-hardening/2017/04/06/14.

This feature identifies structures for randomization in two ways. The first 
method targets structures that are manually marked with the new 
“randomize_layout” attribute. The second is an optional feature that will 
automatically select and randomize structures that are found to consist entirely
of function pointers. This automatic selection feature can be extended to 
include other vulnerable structure types that are safe to randomize as they are
identified. You can also opt a specific structure out of this feature with the 
“no_randomize_layout” attribute. Automatic structure selection is enabled with 
the “-randstruct-auto” compiler flag. By default, Randstruct seeds on the empty
string, but a seed can be supplied with the “-randstruct-seed=” command line 
argument.

This entire patch set is the sum total of an undergraduate computer science 
capstone team’s effort.

Portland State University Clang Randstruct Capstone Team (Fall 2018-Winter 2019):

Co-authored-by: Cole Nixon <nixontcole at gmail.com>
Co-authored-by: Connor Kuehl <cipkuehl at gmail.com>
Co-authored-by: James Foster <jafosterja at gmail.com>
Co-authored-by: Jeff Takahashi <jeffrey.takahashi at gmail.com>
Co-authored-by: Jordan Cantrell <jordan.cantrell at mail.com>
Co-authored-by: Nikk Forbus <nicholas.forbus at gmail.com>
Co-authored-by: Tim Pugh <nwtpugh at gmail.com>

Connor Kuehl (12):
  Add documentation for randstruct attributes
  Add randomize_layout attribute and handler
  Add no_randomize_layout attribute and handler
  Add randomize_layout warning for unions
  Add warning for mutually exclusive attributes
  Add globals to store command line arguments in
  Add randstruct-seed compiler argument
  Add automatic structure selection compiler switch
  Implement record field randomization algorithms
  Fix: Set tail pointer to null in field list
  Forward declare RecordFieldReorganizer
  Wire up Randstruct; intercept and randomize

 clang/include/clang/AST/Decl.h                |   1 +
 clang/include/clang/AST/DeclBase.h            |   2 +
 clang/include/clang/AST/RandstructSeed.h      |   8 +
 .../clang/AST/RecordFieldReorganizer.h        |  59 ++++
 clang/include/clang/Basic/Attr.td             |  14 +
 clang/include/clang/Basic/AttrDocs.td         |  45 +++
 .../include/clang/Basic/DiagnosticASTKinds.td |   5 +
 clang/include/clang/Driver/CC1Options.td      |   2 +
 clang/include/clang/Driver/Options.td         |   4 +
 clang/lib/AST/CMakeLists.txt                  |   1 +
 clang/lib/AST/DeclBase.cpp                    |   3 +
 clang/lib/AST/RecordFieldReorganizer.cpp      | 257 ++++++++++++++++++
 clang/lib/AST/RecordLayoutBuilder.cpp         |  20 ++
 clang/lib/Driver/ToolChains/Clang.cpp         |  10 +
 clang/lib/Frontend/CompilerInvocation.cpp     |   8 +
 clang/lib/Sema/SemaDeclAttr.cpp               |   6 +
 ...a-attribute-supported-attributes-list.test |   2 +
 17 files changed, 447 insertions(+)
 create mode 100644 clang/include/clang/AST/RandstructSeed.h
 create mode 100644 clang/include/clang/AST/RecordFieldReorganizer.h
 create mode 100644 clang/lib/AST/RecordFieldReorganizer.cpp

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2.17.1