Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751747AbdHXJNw (ORCPT ); Thu, 24 Aug 2017 05:13:52 -0400 Received: from mail-io0-f181.google.com ([209.85.223.181]:34141 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751356AbdHXJNu (ORCPT ); Thu, 24 Aug 2017 05:13:50 -0400 MIME-Version: 1.0 In-Reply-To: <20170824081811.19299-10-takahiro.akashi@linaro.org> References: <20170824081811.19299-1-takahiro.akashi@linaro.org> <20170824081811.19299-10-takahiro.akashi@linaro.org> From: Ard Biesheuvel Date: Thu, 24 Aug 2017 10:13:49 +0100 Message-ID: Subject: Re: [PATCH 09/14] arm64: kexec_file: add sha256 digest check in purgatory To: AKASHI Takahiro Cc: Catalin Marinas , Will Deacon , Thiago Jung Bauermann , David Howells , Vivek Goyal , Herbert Xu , "David S. Miller" , Andrew Morton , Michael Ellerman , Dave Young , Baoquan He , Arnd Bergmann , "kexec@lists.infradead.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9837 Lines: 309 On 24 August 2017 at 09:18, AKASHI Takahiro wrote: > Most of sha256 code is based on crypto/sha256-glue.c, particularly using > non-neon version. > > Please note that we won't be able to re-use lib/mem*.S for purgatory > because unaligned memory access is not allowed in purgatory where mmu > is turned off. > > Since purgatory is not linked with the other part of kernel, care must be > taken of selecting an appropriate set of compiler options in order to > prevent undefined symbol references from being generated. > > Signed-off-by: AKASHI Takahiro > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Ard Biesheuvel > --- > arch/arm64/crypto/sha256-core.S_shipped | 2 + > arch/arm64/purgatory/Makefile | 21 ++++++++- > arch/arm64/purgatory/entry.S | 13 ++++++ > arch/arm64/purgatory/purgatory.c | 20 +++++++++ > arch/arm64/purgatory/sha256-core.S | 1 + > arch/arm64/purgatory/sha256.c | 79 +++++++++++++++++++++++++++++++++ > arch/arm64/purgatory/sha256.h | 1 + > arch/arm64/purgatory/string.c | 32 +++++++++++++ > arch/arm64/purgatory/string.h | 5 +++ > 9 files changed, 173 insertions(+), 1 deletion(-) > create mode 100644 arch/arm64/purgatory/purgatory.c > create mode 100644 arch/arm64/purgatory/sha256-core.S > create mode 100644 arch/arm64/purgatory/sha256.c > create mode 100644 arch/arm64/purgatory/sha256.h > create mode 100644 arch/arm64/purgatory/string.c > create mode 100644 arch/arm64/purgatory/string.h > > diff --git a/arch/arm64/crypto/sha256-core.S_shipped b/arch/arm64/crypto/sha256-core.S_shipped > index 3ce82cc860bc..9ce7419c9152 100644 > --- a/arch/arm64/crypto/sha256-core.S_shipped > +++ b/arch/arm64/crypto/sha256-core.S_shipped > @@ -1210,6 +1210,7 @@ sha256_block_armv8: > ret > .size sha256_block_armv8,.-sha256_block_armv8 > #endif > +#ifndef __PURGATORY__ > #ifdef __KERNEL__ > .globl sha256_block_neon > #endif > @@ -2056,6 +2057,7 @@ sha256_block_neon: > add sp,sp,#16*4+16 > ret > .size sha256_block_neon,.-sha256_block_neon > +#endif > #ifndef __KERNEL__ > .comm OPENSSL_armcap_P,4,4 > #endif Could you please try to find another way to address this? sha256-core.S_shipped is generated code from the accompanying Perl script, and that script is kept in sync with upstream OpenSSL. Also, the performance delta between the generic code is not /that/ spectacular, so we may simply use that instead. > diff --git a/arch/arm64/purgatory/Makefile b/arch/arm64/purgatory/Makefile > index c2127a2cbd51..d9b38be31e0a 100644 > --- a/arch/arm64/purgatory/Makefile > +++ b/arch/arm64/purgatory/Makefile > @@ -1,14 +1,33 @@ > OBJECT_FILES_NON_STANDARD := y > > -purgatory-y := entry.o > +purgatory-y := entry.o purgatory.o sha256.o sha256-core.o string.o > > targets += $(purgatory-y) > PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y)) > > +# Purgatory is expected to be ET_REL, not an executable > LDFLAGS_purgatory.ro := -e purgatory_start -r --no-undefined \ > -nostdlib -z nodefaultlib > + > targets += purgatory.ro > > +GCOV_PROFILE := n > +KASAN_SANITIZE := n > +KCOV_INSTRUMENT := n > + > +# Some kernel configurations may generate additional code containing > +# undefined symbols, like _mcount for ftrace and __stack_chk_guard > +# for stack-protector. Those should be removed from purgatory. > + > +CFLAGS_REMOVE_purgatory.o = -pg > +CFLAGS_REMOVE_sha256.o = -pg > +CFLAGS_REMOVE_string.o = -pg > + > +NO_PROTECTOR := $(call cc-option, -fno-stack-protector) > +KBUILD_CFLAGS += $(NO_PROTECTOR) > + > +KBUILD_AFLAGS += -D__PURGATORY__ > + > $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE > $(call if_changed,ld) > > diff --git a/arch/arm64/purgatory/entry.S b/arch/arm64/purgatory/entry.S > index bc4e6b3bf8a1..74d028b838bd 100644 > --- a/arch/arm64/purgatory/entry.S > +++ b/arch/arm64/purgatory/entry.S > @@ -6,6 +6,11 @@ > .text > > ENTRY(purgatory_start) > + adr x19, .Lstack > + mov sp, x19 > + > + bl purgatory > + > /* Start new image. */ > ldr x17, arm64_kernel_entry > ldr x0, arm64_dtb_addr > @@ -15,6 +20,14 @@ ENTRY(purgatory_start) > br x17 > END(purgatory_start) > > +.ltorg > + > +.align 4 > + .rept 256 > + .quad 0 > + .endr > +.Lstack: > + > .data > > .align 3 > diff --git a/arch/arm64/purgatory/purgatory.c b/arch/arm64/purgatory/purgatory.c > new file mode 100644 > index 000000000000..7fcbefa786bc > --- /dev/null > +++ b/arch/arm64/purgatory/purgatory.c > @@ -0,0 +1,20 @@ > +/* > + * purgatory: Runs between two kernels > + * > + * Copyright (c) 2017 Linaro Limited > + * Author: AKASHI Takahiro > + */ > + > +#include "sha256.h" > + > +void purgatory(void) > +{ > + int ret; > + > + ret = verify_sha256_digest(); > + if (ret) { > + /* loop forever */ > + for (;;) > + ; > + } > +} > diff --git a/arch/arm64/purgatory/sha256-core.S b/arch/arm64/purgatory/sha256-core.S > new file mode 100644 > index 000000000000..24f5ce25b61e > --- /dev/null > +++ b/arch/arm64/purgatory/sha256-core.S > @@ -0,0 +1 @@ > +#include "../crypto/sha256-core.S_shipped" > diff --git a/arch/arm64/purgatory/sha256.c b/arch/arm64/purgatory/sha256.c > new file mode 100644 > index 000000000000..5d20d81767e3 > --- /dev/null > +++ b/arch/arm64/purgatory/sha256.c > @@ -0,0 +1,79 @@ > +#include > +#include > +#include > + > +/* > + * Under KASAN, those are defined as un-instrumented version, __memxxx() > + */ > +#undef memcmp > +#undef memcpy > +#undef memset > + > +#include "string.h" > +#include > +#include > +#include > + > +u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE] __section(.kexec-purgatory); > +struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX] > + __section(.kexec-purgatory); > + > +asmlinkage void sha256_block_data_order(u32 *digest, const void *data, > + unsigned int num_blks); > + > +static int sha256_init(struct shash_desc *desc) > +{ > + return sha256_base_init(desc); > +} > + > +static int sha256_update(struct shash_desc *desc, const u8 *data, > + unsigned int len) > +{ > + return sha256_base_do_update(desc, data, len, > + (sha256_block_fn *)sha256_block_data_order); > +} > + > +static int __sha256_base_finish(struct shash_desc *desc, u8 *out) > +{ > + /* we can't do crypto_shash_digestsize(desc->tfm) */ > + unsigned int digest_size = 32; > + struct sha256_state *sctx = shash_desc_ctx(desc); > + __be32 *digest = (__be32 *)out; > + int i; > + > + for (i = 0; digest_size > 0; i++, digest_size -= sizeof(__be32)) > + put_unaligned_be32(sctx->state[i], digest++); > + > + *sctx = (struct sha256_state){}; > + return 0; > +} > + > +static int sha256_final(struct shash_desc *desc, u8 *out) > +{ > + sha256_base_do_finalize(desc, > + (sha256_block_fn *)sha256_block_data_order); > + > + return __sha256_base_finish(desc, out); > +} > + > +int verify_sha256_digest(void) > +{ > + char __sha256_desc[sizeof(struct shash_desc) + > + sizeof(struct sha256_state)] CRYPTO_MINALIGN_ATTR; > + struct shash_desc *desc = (struct shash_desc *)__sha256_desc; > + struct kexec_sha_region *ptr, *end; > + u8 digest[SHA256_DIGEST_SIZE]; > + > + sha256_init(desc); > + > + end = purgatory_sha_regions + ARRAY_SIZE(purgatory_sha_regions); > + for (ptr = purgatory_sha_regions; ptr < end; ptr++) > + sha256_update(desc, (uint8_t *)(ptr->start), ptr->len); > + > + sha256_final(desc, digest); > + > + if (memcmp(digest, purgatory_sha256_digest, sizeof(digest))) > + return 1; > + > + return 0; > +} > diff --git a/arch/arm64/purgatory/sha256.h b/arch/arm64/purgatory/sha256.h > new file mode 100644 > index 000000000000..54dc3c33c469 > --- /dev/null > +++ b/arch/arm64/purgatory/sha256.h > @@ -0,0 +1 @@ > +extern int verify_sha256_digest(void); > diff --git a/arch/arm64/purgatory/string.c b/arch/arm64/purgatory/string.c > new file mode 100644 > index 000000000000..33233a210a65 > --- /dev/null > +++ b/arch/arm64/purgatory/string.c > @@ -0,0 +1,32 @@ > +#include > + > +void *memcpy(void *dst, const void *src, size_t len) > +{ > + int i; > + > + for (i = 0; i < len; i++) > + ((u8 *)dst)[i] = ((u8 *)src)[i]; > + > + return NULL; > +} > + > +void *memset(void *dst, int c, size_t len) > +{ > + int i; > + > + for (i = 0; i < len; i++) > + ((u8 *)dst)[i] = (u8)c; > + > + return NULL; > +} > + > +int memcmp(const void *src, const void *dst, size_t len) > +{ > + int i; > + > + for (i = 0; i < len; i++) > + if (*(char *)src != *(char *)dst) > + return 1; > + > + return 0; > +} > diff --git a/arch/arm64/purgatory/string.h b/arch/arm64/purgatory/string.h > new file mode 100644 > index 000000000000..cb5f68dd84ef > --- /dev/null > +++ b/arch/arm64/purgatory/string.h > @@ -0,0 +1,5 @@ > +#include > + > +int memcmp(const void *s1, const void *s2, size_t len); > +void *memcpy(void *dst, const void *src, size_t len); > +void *memset(void *dst, int c, size_t len); > -- > 2.14.1 >