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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id t7-20020a62ea07000000b0050dc76281f1sm6709358pfh.203.2022.05.03.13.55.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 May 2022 13:55:10 -0700 (PDT) From: Kees Cook To: Bill Wendling Cc: Kees Cook , linux-hardening@vger.kernel.org, Masahiro Yamada , Nick Desaulniers , David Howells , Jeff Layton , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH 5/6] randstruct: Move seed generation into scripts/basic/ Date: Tue, 3 May 2022 13:55:02 -0700 Message-Id: <20220503205503.3054173-6-keescook@chromium.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220503205503.3054173-1-keescook@chromium.org> References: <20220503205503.3054173-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6991; h=from:subject; bh=POSwG5vGM5ePjK+NnCJy7zXZuBYgVkMBrdQajWqSdos=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBicZamheMTQbFPcgMuGPTOLLAi+SSC63O6IOd2ZB8G s01qn/WJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYnGWpgAKCRCJcvTf3G3AJmrYD/ 9/S4SyNCCc6JysEizCShXfywKRGd/VypdZzFIpfGVbMWoWwduoZHcTO2KvS/88sMU72c4E6tNHVTRW JNSdq6HqbNyLDa2c3Dr07Ke9TEO3YZJ/bWwUeEOvEiKdyRNOMFU5picScsWYclKC8xdqB/Nq3wXBbd Syaf1Pdc6CFYgTnv6Ve4xYPoQAl0Pl4SxmPZV7QhdnJlRh0sGZzcRQJHdIn2MKAzEJLjCdPSTPJeqV OympuT/CPrl65t1f3iQN/m62UbI2nL8alWR7RHtr3qQ4HhZYIh+b2JufhOxFBEW/4BGFvEPSA3UsOG Q0SZwl70gwV44QEX/3jgTI86Lyld20sO8Px5z9cwUb0L004gQA+AR9sPwkEfe7QOEqEwDXJfyqtfMP cjy+VOCP7JFHS07booUAPGlUozGNlpzI2aT4rC4QiBQa0lcOEwXEzy8D9RrGj1zD0V/dz0e65UeQrg 2+Ibt4ziS+cHW6V+xUWPVZiQEKR+KyFb4aoHY+KCo3WR4LxiNbBNYWL6rUOXurCrSohkdU5mhkXyMH BmD60mww0e9EASzMySkYpkNIdlzimz0ekp8TAxceKDEb206dnxQOucbY9ntdg07Ffyf3pC5dywOqgy quouzBQoX6hoUJwnW2nDegfzTxW0QgU8tYhLnXP0sZvayjjDxnZhkl0UpOig== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org To enable Clang randstruct support, move the structure layout randomization seed generation out of scripts/gcc-plugins/ into scripts/basic/ so it happens early enough that it can be used by either compiler implementation. The gcc-plugin still builds its own header file, but now does so from the common "randstruct.seed" file. Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook --- Documentation/dontdiff | 1 + Documentation/kbuild/reproducible-builds.rst | 5 +++-- include/linux/vermagic.h | 2 +- scripts/basic/.gitignore | 1 + scripts/basic/Makefile | 11 +++++++++++ scripts/gcc-plugins/Makefile | 15 ++++++++++----- scripts/gcc-plugins/gen-random-seed.sh | 9 --------- scripts/gen-randstruct-seed.sh | 7 +++++++ security/Kconfig.hardening | 9 +++++---- 9 files changed, 39 insertions(+), 21 deletions(-) delete mode 100755 scripts/gcc-plugins/gen-random-seed.sh create mode 100755 scripts/gen-randstruct-seed.sh diff --git a/Documentation/dontdiff b/Documentation/dontdiff index 910b30a2a7d9..352ff53a2306 100644 --- a/Documentation/dontdiff +++ b/Documentation/dontdiff @@ -211,6 +211,7 @@ r200_reg_safe.h r300_reg_safe.h r420_reg_safe.h r600_reg_safe.h +randstruct.seed randomize_layout_hash.h randomize_layout_seed.h recordmcount diff --git a/Documentation/kbuild/reproducible-builds.rst b/Documentation/kbuild/reproducible-builds.rst index 81ff30505d35..071f0151a7a4 100644 --- a/Documentation/kbuild/reproducible-builds.rst +++ b/Documentation/kbuild/reproducible-builds.rst @@ -100,8 +100,9 @@ Structure randomisation ----------------------- If you enable ``CONFIG_RANDSTRUCT``, you will need to pre-generate -the random seed in ``scripts/gcc-plugins/randomize_layout_seed.h`` -so the same value is used in rebuilds. +the random seed in ``scripts/basic/randstruct.seed`` so the same +value is used by each build. See ``scripts/gen-randstruct-seed.sh`` +for details. Debug info conflicts -------------------- diff --git a/include/linux/vermagic.h b/include/linux/vermagic.h index efb51a2da599..a54046bf37e5 100644 --- a/include/linux/vermagic.h +++ b/include/linux/vermagic.h @@ -33,7 +33,7 @@ #define MODULE_VERMAGIC_MODVERSIONS "" #endif #ifdef RANDSTRUCT -#include +#include #define MODULE_RANDSTRUCT "RANDSTRUCT_" RANDSTRUCT_HASHED_SEED #else #define MODULE_RANDSTRUCT diff --git a/scripts/basic/.gitignore b/scripts/basic/.gitignore index 961c91c8a884..07c195f605a1 100644 --- a/scripts/basic/.gitignore +++ b/scripts/basic/.gitignore @@ -1,2 +1,3 @@ # SPDX-License-Identifier: GPL-2.0-only /fixdep +/randstruct.seed diff --git a/scripts/basic/Makefile b/scripts/basic/Makefile index eeb6a38c5551..dd289a6725ac 100644 --- a/scripts/basic/Makefile +++ b/scripts/basic/Makefile @@ -3,3 +3,14 @@ # fixdep: used to generate dependency information during build process hostprogs-always-y += fixdep + +# randstruct: the seed is needed before building the gcc-plugin or +# before running a Clang kernel build. +gen-randstruct-seed := $(srctree)/scripts/gen-randstruct-seed.sh +quiet_cmd_create_randstruct_seed = GENSEED $@ +cmd_create_randstruct_seed = \ + $(CONFIG_SHELL) $(gen-randstruct-seed) \ + $@ $(objtree)/include/generated/randstruct_hash.h +$(obj)/randstruct.seed: $(gen-randstruct-seed) FORCE + $(call if_changed,create_randstruct_seed) +always-$(CONFIG_RANDSTRUCT) += randstruct.seed diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile index 1952d3bb80c6..148f4639cf09 100644 --- a/scripts/gcc-plugins/Makefile +++ b/scripts/gcc-plugins/Makefile @@ -1,12 +1,17 @@ # SPDX-License-Identifier: GPL-2.0 -$(obj)/randomize_layout_plugin.so: $(objtree)/$(obj)/randomize_layout_seed.h -quiet_cmd_create_randomize_layout_seed = GENSEED $@ +$(obj)/randomize_layout_plugin.so: $(obj)/randomize_layout_seed.h +quiet_cmd_create_randomize_layout_seed = SEEDHDR $@ cmd_create_randomize_layout_seed = \ - $(CONFIG_SHELL) $(srctree)/$(src)/gen-random-seed.sh $@ $(objtree)/include/generated/randomize_layout_hash.h -$(objtree)/$(obj)/randomize_layout_seed.h: FORCE + SEED=$$(cat $(filter-out FORCE,$^) $@; \ + echo ' * This file is automatically generated. Keep it private.' >> $@; \ + echo ' * Exposing this value will expose the layout of randomized structures.' >> $@; \ + echo ' */' >> $@; \ + echo "const char *randstruct_seed = \"$$SEED\";" >> $@ +$(obj)/randomize_layout_seed.h: $(objtree)/scripts/basic/randstruct.seed FORCE $(call if_changed,create_randomize_layout_seed) -targets += randomize_layout_seed.h randomize_layout_hash.h +targets += randomize_layout_seed.h # Build rules for plugins # diff --git a/scripts/gcc-plugins/gen-random-seed.sh b/scripts/gcc-plugins/gen-random-seed.sh deleted file mode 100755 index 68af5cc20a64..000000000000 --- a/scripts/gcc-plugins/gen-random-seed.sh +++ /dev/null @@ -1,9 +0,0 @@ -#!/bin/sh -# SPDX-License-Identifier: GPL-2.0 - -if [ ! -f "$1" ]; then - SEED=`od -A n -t x8 -N 32 /dev/urandom | tr -d ' \n'` - echo "const char *randstruct_seed = \"$SEED\";" > "$1" - HASH=`echo -n "$SEED" | sha256sum | cut -d" " -f1 | tr -d ' \n'` - echo "#define RANDSTRUCT_HASHED_SEED \"$HASH\"" > "$2" -fi diff --git a/scripts/gen-randstruct-seed.sh b/scripts/gen-randstruct-seed.sh new file mode 100755 index 000000000000..61017b36c464 --- /dev/null +++ b/scripts/gen-randstruct-seed.sh @@ -0,0 +1,7 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 + +SEED=$(od -A n -t x8 -N 32 /dev/urandom | tr -d ' \n') +echo "$SEED" > "$1" +HASH=$(echo -n "$SEED" | sha256sum | cut -d" " -f1) +echo "#define RANDSTRUCT_HASHED_SEED \"$HASH\"" > "$2" diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 364e3f8c6eea..0277ba578779 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -284,10 +284,11 @@ choice tools like Volatility against the system (unless the kernel source tree isn't cleaned after kernel installation). - The seed used for compilation is located at - scripts/randomize_layout_seed.h. It remains after a "make clean" - to allow for external modules to be compiled with the existing - seed and will be removed by a "make mrproper" or "make distclean". + The seed used for compilation is in scripts/basic/randomize.seed. + It remains after a "make clean" to allow for external modules to + be compiled with the existing seed and will be removed by a + "make mrproper" or "make distclean". This file should not be made + public, or the structure layout can be determined. config RANDSTRUCT_NONE bool "Disable structure layout randomization"