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crypto: skcipher - Introduce crypto_sync_skcipher
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In preparation for removal of VLAs due to skcipher requests on the stack
via SKCIPHER_REQUEST_ON_STACK() usage, this introduces the infrastructure
for the "sync skcipher" tfm, which is for handling the on-stack cases of
skcipher, which are always non-ASYNC and have a known limited request
size.

The crypto API additions:

	struct crypto_sync_skcipher (wrapper for struct crypto_skcipher)
	crypto_alloc_sync_skcipher()
	crypto_free_sync_skcipher()
	crypto_sync_skcipher_setkey()
	crypto_sync_skcipher_get_flags()
	crypto_sync_skcipher_set_flags()
	crypto_sync_skcipher_clear_flags()
	crypto_sync_skcipher_blocksize()
	crypto_sync_skcipher_ivsize()
	crypto_sync_skcipher_reqtfm()
	skcipher_request_set_sync_tfm()
	SYNC_SKCIPHER_REQUEST_ON_STACK() (with tfm type check)

Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Ard Biesheuvel <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>
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@kees @herbertx
kees authored and herbertx committed Sep 28, 2018
1 parent 3944f13 commit b350bee
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24 changes: 24 additions & 0 deletions crypto/skcipher.c
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Original file line number Diff line number Diff line change
Expand Up @@ -949,6 +949,30 @@ struct crypto_skcipher *crypto_alloc_skcipher(const char *alg_name,
}
EXPORT_SYMBOL_GPL(crypto_alloc_skcipher);

struct crypto_sync_skcipher *crypto_alloc_sync_skcipher(
const char *alg_name, u32 type, u32 mask)
{
struct crypto_skcipher *tfm;

/* Only sync algorithms allowed. */
mask |= CRYPTO_ALG_ASYNC;

tfm = crypto_alloc_tfm(alg_name, &crypto_skcipher_type2, type, mask);

/*
* Make sure we do not allocate something that might get used with
* an on-stack request: check the request size.
*/
if (!IS_ERR(tfm) && WARN_ON(crypto_skcipher_reqsize(tfm) >
MAX_SYNC_SKCIPHER_REQSIZE)) {
crypto_free_skcipher(tfm);
return ERR_PTR(-EINVAL);
}

return (struct crypto_sync_skcipher *)tfm;
}
EXPORT_SYMBOL_GPL(crypto_alloc_sync_skcipher);

int crypto_has_skcipher2(const char *alg_name, u32 type, u32 mask)
{
return crypto_type_has_alg(alg_name, &crypto_skcipher_type2,
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75 changes: 75 additions & 0 deletions include/crypto/skcipher.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,10 @@ struct crypto_skcipher {
struct crypto_tfm base;
};

struct crypto_sync_skcipher {
struct crypto_skcipher base;
};

/**
* struct skcipher_alg - symmetric key cipher definition
* @min_keysize: Minimum key size supported by the transformation. This is the
Expand Down Expand Up @@ -139,6 +143,19 @@ struct skcipher_alg {
struct crypto_alg base;
};

#define MAX_SYNC_SKCIPHER_REQSIZE 384
/*
* This performs a type-check against the "tfm" argument to make sure
* all users have the correct skcipher tfm for doing on-stack requests.
*/
#define SYNC_SKCIPHER_REQUEST_ON_STACK(name, tfm) \
char __##name##_desc[sizeof(struct skcipher_request) + \
MAX_SYNC_SKCIPHER_REQSIZE + \
(!(sizeof((struct crypto_sync_skcipher *)1 == \
(typeof(tfm))1))) \
] CRYPTO_MINALIGN_ATTR; \
struct skcipher_request *name = (void *)__##name##_desc

#define SKCIPHER_REQUEST_ON_STACK(name, tfm) \
char __##name##_desc[sizeof(struct skcipher_request) + \
crypto_skcipher_reqsize(tfm)] CRYPTO_MINALIGN_ATTR; \
Expand Down Expand Up @@ -197,6 +214,9 @@ static inline struct crypto_skcipher *__crypto_skcipher_cast(
struct crypto_skcipher *crypto_alloc_skcipher(const char *alg_name,
u32 type, u32 mask);

struct crypto_sync_skcipher *crypto_alloc_sync_skcipher(const char *alg_name,
u32 type, u32 mask);

static inline struct crypto_tfm *crypto_skcipher_tfm(
struct crypto_skcipher *tfm)
{
Expand All @@ -212,6 +232,11 @@ static inline void crypto_free_skcipher(struct crypto_skcipher *tfm)
crypto_destroy_tfm(tfm, crypto_skcipher_tfm(tfm));
}

static inline void crypto_free_sync_skcipher(struct crypto_sync_skcipher *tfm)
{
crypto_free_skcipher(&tfm->base);
}

/**
* crypto_has_skcipher() - Search for the availability of an skcipher.
* @alg_name: is the cra_name / name or cra_driver_name / driver name of the
Expand Down Expand Up @@ -280,6 +305,12 @@ static inline unsigned int crypto_skcipher_ivsize(struct crypto_skcipher *tfm)
return tfm->ivsize;
}

static inline unsigned int crypto_sync_skcipher_ivsize(
struct crypto_sync_skcipher *tfm)
{
return crypto_skcipher_ivsize(&tfm->base);
}

static inline unsigned int crypto_skcipher_alg_chunksize(
struct skcipher_alg *alg)
{
Expand Down Expand Up @@ -356,6 +387,12 @@ static inline unsigned int crypto_skcipher_blocksize(
return crypto_tfm_alg_blocksize(crypto_skcipher_tfm(tfm));
}

static inline unsigned int crypto_sync_skcipher_blocksize(
struct crypto_sync_skcipher *tfm)
{
return crypto_skcipher_blocksize(&tfm->base);
}

static inline unsigned int crypto_skcipher_alignmask(
struct crypto_skcipher *tfm)
{
Expand All @@ -379,6 +416,24 @@ static inline void crypto_skcipher_clear_flags(struct crypto_skcipher *tfm,
crypto_tfm_clear_flags(crypto_skcipher_tfm(tfm), flags);
}

static inline u32 crypto_sync_skcipher_get_flags(
struct crypto_sync_skcipher *tfm)
{
return crypto_skcipher_get_flags(&tfm->base);
}

static inline void crypto_sync_skcipher_set_flags(
struct crypto_sync_skcipher *tfm, u32 flags)
{
crypto_skcipher_set_flags(&tfm->base, flags);
}

static inline void crypto_sync_skcipher_clear_flags(
struct crypto_sync_skcipher *tfm, u32 flags)
{
crypto_skcipher_clear_flags(&tfm->base, flags);
}

/**
* crypto_skcipher_setkey() - set key for cipher
* @tfm: cipher handle
Expand All @@ -401,6 +456,12 @@ static inline int crypto_skcipher_setkey(struct crypto_skcipher *tfm,
return tfm->setkey(tfm, key, keylen);
}

static inline int crypto_sync_skcipher_setkey(struct crypto_sync_skcipher *tfm,
const u8 *key, unsigned int keylen)
{
return crypto_skcipher_setkey(&tfm->base, key, keylen);
}

static inline unsigned int crypto_skcipher_default_keysize(
struct crypto_skcipher *tfm)
{
Expand All @@ -422,6 +483,14 @@ static inline struct crypto_skcipher *crypto_skcipher_reqtfm(
return __crypto_skcipher_cast(req->base.tfm);
}

static inline struct crypto_sync_skcipher *crypto_sync_skcipher_reqtfm(
struct skcipher_request *req)
{
struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);

return container_of(tfm, struct crypto_sync_skcipher, base);
}

/**
* crypto_skcipher_encrypt() - encrypt plaintext
* @req: reference to the skcipher_request handle that holds all information
Expand Down Expand Up @@ -500,6 +569,12 @@ static inline void skcipher_request_set_tfm(struct skcipher_request *req,
req->base.tfm = crypto_skcipher_tfm(tfm);
}

static inline void skcipher_request_set_sync_tfm(struct skcipher_request *req,
struct crypto_sync_skcipher *tfm)
{
skcipher_request_set_tfm(req, &tfm->base);
}

static inline struct skcipher_request *skcipher_request_cast(
struct crypto_async_request *req)
{
Expand Down

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