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Use zero_call_used_regs and noinline for backend memory utils and introduce crypt_backend_memcpy.

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This commit is contained in:
Milan Broz
2024-04-24 15:40:52 +02:00
parent aae5cba2b9
commit c5d4b845df
2 changed files with 26 additions and 0 deletions
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3
lib/crypto_backend/crypto_backend.h
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@@ -146,6 +146,9 @@ int crypt_bitlk_decrypt_key(const void *key, size_t key_length,
/* Memzero helper (memset on stack can be optimized out) */
void crypt_backend_memzero(void *s, size_t n);
/* Memcpy helper to avoid spilling sensitive data through additional registers */
void *crypt_backend_memcpy(void *dst, const void *src, size_t n);
/* Memcmp helper (memcmp in constant time) */
int crypt_backend_memeq(const void *m1, const void *m2, size_t n);

23
lib/crypto_backend/memutils.c
View File

@@ -20,7 +20,17 @@
#include "crypto_backend_internal.h"
#define ATTR_NOINLINE __attribute__ ((noinline))
#define ATTR_ZERO_REGS
#if defined __has_attribute
# if __has_attribute (zero_call_used_regs)
# undef ATTR_ZERO_REGS
# define ATTR_ZERO_REGS __attribute__ ((zero_call_used_regs("used")))
# endif
#endif
/* Memzero helper (memset on stack can be optimized out) */
ATTR_NOINLINE ATTR_ZERO_REGS
void crypt_backend_memzero(void *s, size_t n)
{
#ifdef HAVE_EXPLICIT_BZERO
@@ -31,7 +41,20 @@ void crypt_backend_memzero(void *s, size_t n)
#endif
}
/* Memcpy helper to avoid spilling sensitive data through additional registers */
ATTR_NOINLINE ATTR_ZERO_REGS
void *crypt_backend_memcpy(void *dst, const void *src, size_t n)
{
volatile uint8_t *d = (volatile uint8_t *)dst;
const volatile uint8_t *s = (const volatile uint8_t *)src;
while(n--) *d++ = *s++;
return dst;
}
/* Internal implementation for constant time memory comparison */
ATTR_NOINLINE ATTR_ZERO_REGS
int crypt_internal_memeq(const void *m1, const void *m2, size_t n)
{
const unsigned char *_m1 = (const unsigned char *) m1;