diff options
| -rw-r--r-- | crypto/Makefile | 5 | ||||
| -rw-r--r-- | crypto/memneq.c | 79 | ||||
| -rw-r--r-- | include/linux/compiler-gcc.h | 3 | ||||
| -rw-r--r-- | include/linux/compiler-intel.h | 7 | ||||
| -rw-r--r-- | include/linux/compiler.h | 4 |
5 files changed, 68 insertions, 30 deletions
diff --git a/crypto/Makefile b/crypto/Makefile index 989c510..b29402a 100644 --- a/crypto/Makefile +++ b/crypto/Makefile @@ -2,11 +2,6 @@ # Cryptographic API # -# memneq MUST be built with -Os or -O0 to prevent early-return optimizations -# that will defeat memneq's actual purpose to prevent timing attacks. -CFLAGS_REMOVE_memneq.o := -O1 -O2 -O3 -CFLAGS_memneq.o := -Os - obj-$(CONFIG_CRYPTO) += crypto.o crypto-y := api.o cipher.o compress.o memneq.o diff --git a/crypto/memneq.c b/crypto/memneq.c index cd01622..570f6f3 100644 --- a/crypto/memneq.c +++ b/crypto/memneq.c @@ -72,6 +72,7 @@ __crypto_memneq_generic(const void *a, const void *b, size_t size) #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) while (size >= sizeof(unsigned long)) { neq |= *(unsigned long *)a ^ *(unsigned long *)b; + OPTIMIZER_HIDE_VAR(neq); a += sizeof(unsigned long); b += sizeof(unsigned long); size -= sizeof(unsigned long); @@ -79,6 +80,7 @@ __crypto_memneq_generic(const void *a, const void *b, size_t size) #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */ while (size > 0) { neq |= *(unsigned char *)a ^ *(unsigned char *)b; + OPTIMIZER_HIDE_VAR(neq); a += 1; b += 1; size -= 1; @@ -89,33 +91,60 @@ __crypto_memneq_generic(const void *a, const void *b, size_t size) /* Loop-free fast-path for frequently used 16-byte size */ static inline unsigned long __crypto_memneq_16(const void *a, const void *b) { + unsigned long neq = 0; + #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS - if (sizeof(unsigned long) == 8) - return ((*(unsigned long *)(a) ^ *(unsigned long *)(b)) - | (*(unsigned long *)(a+8) ^ *(unsigned long *)(b+8))); - else if (sizeof(unsigned int) == 4) - return ((*(unsigned int *)(a) ^ *(unsigned int *)(b)) - | (*(unsigned int *)(a+4) ^ *(unsigned int *)(b+4)) - | (*(unsigned int *)(a+8) ^ *(unsigned int *)(b+8)) - | (*(unsigned int *)(a+12) ^ *(unsigned int *)(b+12))); - else + if (sizeof(unsigned long) == 8) { + neq |= *(unsigned long *)(a) ^ *(unsigned long *)(b); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned long *)(a+8) ^ *(unsigned long *)(b+8); + OPTIMIZER_HIDE_VAR(neq); + } else if (sizeof(unsigned int) == 4) { + neq |= *(unsigned int *)(a) ^ *(unsigned int *)(b); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned int *)(a+4) ^ *(unsigned int *)(b+4); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned int *)(a+8) ^ *(unsigned int *)(b+8); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12); + OPTIMIZER_HIDE_VAR(neq); + } else { #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */ - return ((*(unsigned char *)(a) ^ *(unsigned char *)(b)) - | (*(unsigned char *)(a+1) ^ *(unsigned char *)(b+1)) - | (*(unsigned char *)(a+2) ^ *(unsigned char *)(b+2)) - | (*(unsigned char *)(a+3) ^ *(unsigned char *)(b+3)) - | (*(unsigned char *)(a+4) ^ *(unsigned char *)(b+4)) - | (*(unsigned char *)(a+5) ^ *(unsigned char *)(b+5)) - | (*(unsigned char *)(a+6) ^ *(unsigned char *)(b+6)) - | (*(unsigned char *)(a+7) ^ *(unsigned char *)(b+7)) - | (*(unsigned char *)(a+8) ^ *(unsigned char *)(b+8)) - | (*(unsigned char *)(a+9) ^ *(unsigned char *)(b+9)) - | (*(unsigned char *)(a+10) ^ *(unsigned char *)(b+10)) - | (*(unsigned char *)(a+11) ^ *(unsigned char *)(b+11)) - | (*(unsigned char *)(a+12) ^ *(unsigned char *)(b+12)) - | (*(unsigned char *)(a+13) ^ *(unsigned char *)(b+13)) - | (*(unsigned char *)(a+14) ^ *(unsigned char *)(b+14)) - | (*(unsigned char *)(a+15) ^ *(unsigned char *)(b+15))); + neq |= *(unsigned char *)(a) ^ *(unsigned char *)(b); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+1) ^ *(unsigned char *)(b+1); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+2) ^ *(unsigned char *)(b+2); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+3) ^ *(unsigned char *)(b+3); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+4) ^ *(unsigned char *)(b+4); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+5) ^ *(unsigned char *)(b+5); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+6) ^ *(unsigned char *)(b+6); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+7) ^ *(unsigned char *)(b+7); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+8) ^ *(unsigned char *)(b+8); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+9) ^ *(unsigned char *)(b+9); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14); + OPTIMIZER_HIDE_VAR(neq); + neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15); + OPTIMIZER_HIDE_VAR(neq); + } + + return neq; } /* Compare two areas of memory without leaking timing information, diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 24545cd..02ae99e 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -37,6 +37,9 @@ __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ (typeof(ptr)) (__ptr + (off)); }) +/* Make the optimizer believe the variable can be manipulated arbitrarily. */ +#define OPTIMIZER_HIDE_VAR(var) __asm__ ("" : "=r" (var) : "0" (var)) + #ifdef __CHECKER__ #define __must_be_array(arr) 0 #else diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h index 973ce10..e784f57 100644 --- a/include/linux/compiler-intel.h +++ b/include/linux/compiler-intel.h @@ -15,6 +15,7 @@ */ #undef barrier #undef RELOC_HIDE +#undef OPTIMIZER_HIDE_VAR #define barrier() __memory_barrier() @@ -23,6 +24,12 @@ __ptr = (unsigned long) (ptr); \ (typeof(ptr)) (__ptr + (off)); }) +/* This should act as an optimization barrier on var. + * Given that this compiler does not have inline assembly, a compiler barrier + * is the best we can do. + */ +#define OPTIMIZER_HIDE_VAR(var) barrier() + /* Intel ECC compiler doesn't support __builtin_types_compatible_p() */ #define __must_be_array(a) 0 diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 92669cd..a2329c5 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -170,6 +170,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); (typeof(ptr)) (__ptr + (off)); }) #endif +#ifndef OPTIMIZER_HIDE_VAR +#define OPTIMIZER_HIDE_VAR(var) barrier() +#endif + /* Not-quite-unique ID. */ #ifndef __UNIQUE_ID # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) |
