crypto: algif_hash - User-space interface for hash operations

This patch adds the af_alg plugin for hash, corresponding to
the ahash kernel operation type.

Keys can optionally be set through the setsockopt interface.

Each sendmsg call will finalise the hash unless sent with a MSG_MORE
flag.

Partial hash states can be cloned using accept(2).

The interface is completely synchronous, all operations will
complete prior to the system call returning.

Both sendmsg(2) and splice(2) support reading the user-space
data directly without copying (except that the Crypto API itself
may copy the data if alignment is off).

For now only the splice(2) interface supports performing digest
instead of init/update/final.  In future the sendmsg(2) interface
will also be modified to use digest/finup where possible so that
hardware that cannot return a partial hash state can still benefit
from this interface.

Thakns to Miloslav Trmac for reviewing this and contributing
fixes and improvements.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Martin Willi <martin@strongswan.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 357e3caf4cbe..6db27d7ff8b3 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -844,6 +844,14 @@ config CRYPTO_ANSI_CPRNG
 config CRYPTO_USER_API
         tristate
 
+config CRYPTO_USER_API_HASH
+        tristate "User-space interface for hash algorithms"
+        select CRYPTO_HASH
+        select CRYPTO_USER_API
+        help
+          This option enables the user-spaces interface for hash
+          algorithms.
+
 source "drivers/crypto/Kconfig"
 
 endif   # if CRYPTO