On Wed, 19 Sep 2018 at 04:11, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> 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 <keescook@xxxxxxxxxxxx>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> crypto/skcipher.c | 24 +++++++++++++
> include/crypto/skcipher.h | 75 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 99 insertions(+)
>
> diff --git a/crypto/skcipher.c b/crypto/skcipher.c
> index 0bd8c6caa498..4caab81d2d02 100644
> --- a/crypto/skcipher.c
> +++ b/crypto/skcipher.c
> @@ -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,
> diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
> index 2f327f090c3e..d00ce90dc7da 100644
> --- a/include/crypto/skcipher.h
> +++ b/include/crypto/skcipher.h
> @@ -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
> @@ -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; \
> @@ -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)
> {
> @@ -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
> @@ -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)
> {
> @@ -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)
> {
> @@ -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
> @@ -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)
> {
> @@ -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
> @@ -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)
> {
> --
> 2.17.1
>
