2020-05-02 05:34:25

by Eric Biggers

[permalink] [raw]
Subject: [PATCH 01/20] crypto: hash - introduce crypto_shash_tfm_digest()

From: Eric Biggers <[email protected]>

Currently the simplest use of the shash API is to use
crypto_shash_digest() to digest a whole buffer. However, this still
requires allocating a hash descriptor (struct shash_desc). Many users
don't really want to preallocate one and instead just use a one-off
descriptor on the stack like the following:

{
SHASH_DESC_ON_STACK(desc, tfm);
int err;

desc->tfm = tfm;

err = crypto_shash_digest(desc, data, len, out);

shash_desc_zero(desc);
}

Wrap this in a new helper function crypto_shash_tfm_digest() that can be
used instead of the above.

Signed-off-by: Eric Biggers <[email protected]>
---
crypto/shash.c | 16 ++++++++++++++++
include/crypto/hash.h | 19 +++++++++++++++++++
2 files changed, 35 insertions(+)

diff --git a/crypto/shash.c b/crypto/shash.c
index c075b26c2a1d9f..e6a4b5f39b8c64 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -206,6 +206,22 @@ int crypto_shash_digest(struct shash_desc *desc, const u8 *data,
}
EXPORT_SYMBOL_GPL(crypto_shash_digest);

+int crypto_shash_tfm_digest(struct crypto_shash *tfm, const u8 *data,
+ unsigned int len, u8 *out)
+{
+ SHASH_DESC_ON_STACK(desc, tfm);
+ int err;
+
+ desc->tfm = tfm;
+
+ err = crypto_shash_digest(desc, data, len, out);
+
+ shash_desc_zero(desc);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(crypto_shash_tfm_digest);
+
static int shash_default_export(struct shash_desc *desc, void *out)
{
memcpy(out, shash_desc_ctx(desc), crypto_shash_descsize(desc->tfm));
diff --git a/include/crypto/hash.h b/include/crypto/hash.h
index cee446c59497c6..4829d2367eda87 100644
--- a/include/crypto/hash.h
+++ b/include/crypto/hash.h
@@ -855,6 +855,25 @@ int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
int crypto_shash_digest(struct shash_desc *desc, const u8 *data,
unsigned int len, u8 *out);

+/**
+ * crypto_shash_tfm_digest() - calculate message digest for buffer
+ * @tfm: hash transformation object
+ * @data: see crypto_shash_update()
+ * @len: see crypto_shash_update()
+ * @out: see crypto_shash_final()
+ *
+ * This is a simplified version of crypto_shash_digest() for users who don't
+ * want to allocate their own hash descriptor (shash_desc). Instead,
+ * crypto_shash_tfm_digest() takes a hash transformation object (crypto_shash)
+ * directly, and it allocates a hash descriptor on the stack internally.
+ * Note that this stack allocation may be fairly large.
+ *
+ * Context: Any context.
+ * Return: 0 on success; < 0 if an error occurred.
+ */
+int crypto_shash_tfm_digest(struct crypto_shash *tfm, const u8 *data,
+ unsigned int len, u8 *out);
+
/**
* crypto_shash_export() - extract operational state for message digest
* @desc: reference to the operational state handle whose state is exported
--
2.26.2