linux/include/crypto/algapi.h

286 lines
7.6 KiB
C
Raw Normal View History

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Cryptographic API for algorithms (i.e., low-level API).
*
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*/
#ifndef _CRYPTO_ALGAPI_H
#define _CRYPTO_ALGAPI_H
#include <linux/crypto.h>
#include <linux/list.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
/*
* Maximum values for blocksize and alignmask, used to allocate
* static buffers that are big enough for any combination of
* algs and architectures. Ciphers have a lower maximum size.
*/
#define MAX_ALGAPI_BLOCKSIZE 160
#define MAX_ALGAPI_ALIGNMASK 63
#define MAX_CIPHER_BLOCKSIZE 16
#define MAX_CIPHER_ALIGNMASK 15
struct crypto_aead;
struct crypto_instance;
struct module;
struct rtattr;
struct seq_file;
struct crypto_type {
unsigned int (*ctxsize)(struct crypto_alg *alg, u32 type, u32 mask);
unsigned int (*extsize)(struct crypto_alg *alg);
int (*init)(struct crypto_tfm *tfm, u32 type, u32 mask);
int (*init_tfm)(struct crypto_tfm *tfm);
void (*show)(struct seq_file *m, struct crypto_alg *alg);
int (*report)(struct sk_buff *skb, struct crypto_alg *alg);
void (*free)(struct crypto_instance *inst);
unsigned int type;
unsigned int maskclear;
unsigned int maskset;
unsigned int tfmsize;
};
struct crypto_instance {
struct crypto_alg alg;
struct crypto_template *tmpl;
union {
/* Node in list of instances after registration. */
struct hlist_node list;
/* List of attached spawns before registration. */
struct crypto_spawn *spawns;
};
void *__ctx[] CRYPTO_MINALIGN_ATTR;
};
struct crypto_template {
struct list_head list;
struct hlist_head instances;
struct module *module;
int (*create)(struct crypto_template *tmpl, struct rtattr **tb);
char name[CRYPTO_MAX_ALG_NAME];
};
struct crypto_spawn {
struct list_head list;
struct crypto_alg *alg;
union {
/* Back pointer to instance after registration.*/
struct crypto_instance *inst;
/* Spawn list pointer prior to registration. */
struct crypto_spawn *next;
};
const struct crypto_type *frontend;
u32 mask;
bool dead;
bool registered;
};
struct crypto_queue {
struct list_head list;
struct list_head *backlog;
unsigned int qlen;
unsigned int max_qlen;
};
struct scatter_walk {
struct scatterlist *sg;
unsigned int offset;
};
void crypto_mod_put(struct crypto_alg *alg);
int crypto_register_template(struct crypto_template *tmpl);
int crypto_register_templates(struct crypto_template *tmpls, int count);
void crypto_unregister_template(struct crypto_template *tmpl);
void crypto_unregister_templates(struct crypto_template *tmpls, int count);
struct crypto_template *crypto_lookup_template(const char *name);
int crypto_register_instance(struct crypto_template *tmpl,
struct crypto_instance *inst);
void crypto_unregister_instance(struct crypto_instance *inst);
int crypto_grab_spawn(struct crypto_spawn *spawn, struct crypto_instance *inst,
const char *name, u32 type, u32 mask);
void crypto_drop_spawn(struct crypto_spawn *spawn);
struct crypto_tfm *crypto_spawn_tfm(struct crypto_spawn *spawn, u32 type,
u32 mask);
void *crypto_spawn_tfm2(struct crypto_spawn *spawn);
struct crypto_attr_type *crypto_get_attr_type(struct rtattr **tb);
int crypto_check_attr_type(struct rtattr **tb, u32 type);
const char *crypto_attr_alg_name(struct rtattr *rta);
int crypto_attr_u32(struct rtattr *rta, u32 *num);
int crypto_inst_setname(struct crypto_instance *inst, const char *name,
struct crypto_alg *alg);
void crypto_init_queue(struct crypto_queue *queue, unsigned int max_qlen);
int crypto_enqueue_request(struct crypto_queue *queue,
struct crypto_async_request *request);
void crypto_enqueue_request_head(struct crypto_queue *queue,
struct crypto_async_request *request);
struct crypto_async_request *crypto_dequeue_request(struct crypto_queue *queue);
static inline unsigned int crypto_queue_len(struct crypto_queue *queue)
{
return queue->qlen;
}
void crypto_inc(u8 *a, unsigned int size);
void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int size);
static inline void crypto_xor(u8 *dst, const u8 *src, unsigned int size)
{
if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
__builtin_constant_p(size) &&
(size % sizeof(unsigned long)) == 0) {
unsigned long *d = (unsigned long *)dst;
unsigned long *s = (unsigned long *)src;
while (size > 0) {
*d++ ^= *s++;
size -= sizeof(unsigned long);
}
} else {
__crypto_xor(dst, dst, src, size);
}
}
static inline void crypto_xor_cpy(u8 *dst, const u8 *src1, const u8 *src2,
unsigned int size)
{
if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
__builtin_constant_p(size) &&
(size % sizeof(unsigned long)) == 0) {
unsigned long *d = (unsigned long *)dst;
unsigned long *s1 = (unsigned long *)src1;
unsigned long *s2 = (unsigned long *)src2;
while (size > 0) {
*d++ = *s1++ ^ *s2++;
size -= sizeof(unsigned long);
}
} else {
__crypto_xor(dst, src1, src2, size);
}
}
static inline void *crypto_tfm_ctx_aligned(struct crypto_tfm *tfm)
{
return PTR_ALIGN(crypto_tfm_ctx(tfm),
crypto_tfm_alg_alignmask(tfm) + 1);
}
static inline struct crypto_instance *crypto_tfm_alg_instance(
struct crypto_tfm *tfm)
{
return container_of(tfm->__crt_alg, struct crypto_instance, alg);
}
static inline void *crypto_instance_ctx(struct crypto_instance *inst)
{
return inst->__ctx;
}
struct crypto_cipher_spawn {
struct crypto_spawn base;
};
static inline int crypto_grab_cipher(struct crypto_cipher_spawn *spawn,
struct crypto_instance *inst,
const char *name, u32 type, u32 mask)
{
type &= ~CRYPTO_ALG_TYPE_MASK;
type |= CRYPTO_ALG_TYPE_CIPHER;
mask |= CRYPTO_ALG_TYPE_MASK;
return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
}
static inline void crypto_drop_cipher(struct crypto_cipher_spawn *spawn)
{
crypto_drop_spawn(&spawn->base);
}
static inline struct crypto_alg *crypto_spawn_cipher_alg(
struct crypto_cipher_spawn *spawn)
{
return spawn->base.alg;
}
static inline struct crypto_cipher *crypto_spawn_cipher(
struct crypto_cipher_spawn *spawn)
{
u32 type = CRYPTO_ALG_TYPE_CIPHER;
u32 mask = CRYPTO_ALG_TYPE_MASK;
return __crypto_cipher_cast(crypto_spawn_tfm(&spawn->base, type, mask));
}
static inline struct cipher_alg *crypto_cipher_alg(struct crypto_cipher *tfm)
{
return &crypto_cipher_tfm(tfm)->__crt_alg->cra_cipher;
}
static inline struct crypto_async_request *crypto_get_backlog(
struct crypto_queue *queue)
{
return queue->backlog == &queue->list ? NULL :
container_of(queue->backlog, struct crypto_async_request, list);
}
static inline int crypto_requires_off(u32 type, u32 mask, u32 off)
{
return (type ^ off) & mask & off;
}
/*
* Returns CRYPTO_ALG_ASYNC if type/mask requires the use of sync algorithms.
* Otherwise returns zero.
*/
static inline int crypto_requires_sync(u32 type, u32 mask)
{
return crypto_requires_off(type, mask, CRYPTO_ALG_ASYNC);
}
crypto: crypto_memneq - add equality testing of memory regions w/o timing leaks When comparing MAC hashes, AEAD authentication tags, or other hash values in the context of authentication or integrity checking, it is important not to leak timing information to a potential attacker, i.e. when communication happens over a network. Bytewise memory comparisons (such as memcmp) are usually optimized so that they return a nonzero value as soon as a mismatch is found. E.g, on x86_64/i5 for 512 bytes this can be ~50 cyc for a full mismatch and up to ~850 cyc for a full match (cold). This early-return behavior can leak timing information as a side channel, allowing an attacker to iteratively guess the correct result. This patch adds a new method crypto_memneq ("memory not equal to each other") to the crypto API that compares memory areas of the same length in roughly "constant time" (cache misses could change the timing, but since they don't reveal information about the content of the strings being compared, they are effectively benign). Iow, best and worst case behaviour take the same amount of time to complete (in contrast to memcmp). Note that crypto_memneq (unlike memcmp) can only be used to test for equality or inequality, NOT for lexicographical order. This, however, is not an issue for its use-cases within the crypto API. We tried to locate all of the places in the crypto API where memcmp was being used for authentication or integrity checking, and convert them over to crypto_memneq. crypto_memneq is declared noinline, placed in its own source file, and compiled with optimizations that might increase code size disabled ("Os") because a smart compiler (or LTO) might notice that the return value is always compared against zero/nonzero, and might then reintroduce the same early-return optimization that we are trying to avoid. Using #pragma or __attribute__ optimization annotations of the code for disabling optimization was avoided as it seems to be considered broken or unmaintained for long time in GCC [1]. Therefore, we work around that by specifying the compile flag for memneq.o directly in the Makefile. We found that this seems to be most appropriate. As we use ("Os"), this patch also provides a loop-free "fast-path" for frequently used 16 byte digests. Similarly to kernel library string functions, leave an option for future even further optimized architecture specific assembler implementations. This was a joint work of James Yonan and Daniel Borkmann. Also thanks for feedback from Florian Weimer on this and earlier proposals [2]. [1] http://gcc.gnu.org/ml/gcc/2012-07/msg00211.html [2] https://lkml.org/lkml/2013/2/10/131 Signed-off-by: James Yonan <james@openvpn.net> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Cc: Florian Weimer <fw@deneb.enyo.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2013-09-26 16:20:39 +08:00
noinline unsigned long __crypto_memneq(const void *a, const void *b, size_t size);
/**
* crypto_memneq - Compare two areas of memory without leaking
* timing information.
*
* @a: One area of memory
* @b: Another area of memory
* @size: The size of the area.
*
* Returns 0 when data is equal, 1 otherwise.
*/
static inline int crypto_memneq(const void *a, const void *b, size_t size)
{
return __crypto_memneq(a, b, size) != 0UL ? 1 : 0;
}
static inline void crypto_yield(u32 flags)
{
if (flags & CRYPTO_TFM_REQ_MAY_SLEEP)
cond_resched();
}
int crypto_register_notifier(struct notifier_block *nb);
int crypto_unregister_notifier(struct notifier_block *nb);
/* Crypto notification events. */
enum {
CRYPTO_MSG_ALG_REQUEST,
CRYPTO_MSG_ALG_REGISTER,
CRYPTO_MSG_ALG_LOADED,
};
crypto: crypto_memneq - add equality testing of memory regions w/o timing leaks When comparing MAC hashes, AEAD authentication tags, or other hash values in the context of authentication or integrity checking, it is important not to leak timing information to a potential attacker, i.e. when communication happens over a network. Bytewise memory comparisons (such as memcmp) are usually optimized so that they return a nonzero value as soon as a mismatch is found. E.g, on x86_64/i5 for 512 bytes this can be ~50 cyc for a full mismatch and up to ~850 cyc for a full match (cold). This early-return behavior can leak timing information as a side channel, allowing an attacker to iteratively guess the correct result. This patch adds a new method crypto_memneq ("memory not equal to each other") to the crypto API that compares memory areas of the same length in roughly "constant time" (cache misses could change the timing, but since they don't reveal information about the content of the strings being compared, they are effectively benign). Iow, best and worst case behaviour take the same amount of time to complete (in contrast to memcmp). Note that crypto_memneq (unlike memcmp) can only be used to test for equality or inequality, NOT for lexicographical order. This, however, is not an issue for its use-cases within the crypto API. We tried to locate all of the places in the crypto API where memcmp was being used for authentication or integrity checking, and convert them over to crypto_memneq. crypto_memneq is declared noinline, placed in its own source file, and compiled with optimizations that might increase code size disabled ("Os") because a smart compiler (or LTO) might notice that the return value is always compared against zero/nonzero, and might then reintroduce the same early-return optimization that we are trying to avoid. Using #pragma or __attribute__ optimization annotations of the code for disabling optimization was avoided as it seems to be considered broken or unmaintained for long time in GCC [1]. Therefore, we work around that by specifying the compile flag for memneq.o directly in the Makefile. We found that this seems to be most appropriate. As we use ("Os"), this patch also provides a loop-free "fast-path" for frequently used 16 byte digests. Similarly to kernel library string functions, leave an option for future even further optimized architecture specific assembler implementations. This was a joint work of James Yonan and Daniel Borkmann. Also thanks for feedback from Florian Weimer on this and earlier proposals [2]. [1] http://gcc.gnu.org/ml/gcc/2012-07/msg00211.html [2] https://lkml.org/lkml/2013/2/10/131 Signed-off-by: James Yonan <james@openvpn.net> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Cc: Florian Weimer <fw@deneb.enyo.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2013-09-26 16:20:39 +08:00
#endif /* _CRYPTO_ALGAPI_H */