[PATCH] crypto: af_alg: Allow cbc(paes)

[Richard Weinberger]

Commit 7524070f26d8 ("crypto: af_alg - Drop support for off-CPU cryptography")
breaks a special use case.  The cbc-paes-caam driver implements the
algorithm cbc(paes), it offers a way to use AES in CBC mode with key
material unknown to userspace.  Instead of an AES key a CAAM BLOB is
passed to the kernel.  So, this crypto operation cannot be
implemented in a userspace library and needs always help from the
kernel.

Explicitly allow this use case.

Cc: Demi Marie Obenour <demiobenour@xxxxxxxxx>
Suggested-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Fixes: 7524070f26d8 ("crypto: af_alg - Drop support for off-CPU cryptography")
Signed-off-by: Richard Weinberger <richard@xxxxxx>
---
 crypto/algif_skcipher.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index df20bdfe1f1f..035fed7db81f 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -32,6 +32,7 @@
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/net.h>
+#include <linux/string.h>
 #include <net/sock.h>
 
 static int skcipher_sendmsg(struct socket *sock, struct msghdr *msg,
@@ -309,7 +310,12 @@ static struct proto_ops algif_skcipher_ops_nokey = {
 
 static void *skcipher_bind(const char *name)
 {
-	return crypto_alloc_skcipher(name, 0, AF_ALG_CRYPTOAPI_MASK);
+	u32 mask = AF_ALG_CRYPTOAPI_MASK;
+
+	if (strcmp(name, "cbc(paes)") == 0)
+		mask = 0;
+
+	return crypto_alloc_skcipher(name, 0, mask);
 }
 
 static void skcipher_release(void *private)
-- 
2.51.0