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Subject[PATCH crypto-next 01/23] crypto: skcipher - Introduce crypto_sync_skcipher
Date
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@chromium.org>
---
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
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