crypto: skcipher - Add separate walker for AEAD decryption

The AEAD decrypt interface includes the authentication tag in
req->cryptlen.  Therefore we need to exlucde that when doing
a walk over it.

This patch adds separate walker functions for AEAD encryption
and decryption.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

2 files changed, 34 insertions, 3 deletions

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 5367f817b40e..aca07c643d41 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -500,8 +500,8 @@ int skcipher_walk_async(struct skcipher_walk *walk,
 }
 EXPORT_SYMBOL_GPL(skcipher_walk_async);
 
-int skcipher_walk_aead(struct skcipher_walk *walk, struct aead_request *req,
-                       bool atomic)
+static int skcipher_walk_aead_common(struct skcipher_walk *walk,
+                                     struct aead_request *req, bool atomic)
 {
         struct crypto_aead *tfm = crypto_aead_reqtfm(req);
         int err;
@@ -514,7 +514,6 @@ int skcipher_walk_aead(struct skcipher_walk *walk, struct aead_request *req,
         scatterwalk_copychunks(NULL, &walk->in, req->assoclen, 2);
         scatterwalk_copychunks(NULL, &walk->out, req->assoclen, 2);
 
-        walk->total = req->cryptlen;
         walk->iv = req->iv;
         walk->oiv = req->iv;
 
@@ -535,8 +534,36 @@ int skcipher_walk_aead(struct skcipher_walk *walk, struct aead_request *req,
 
         return err;
 }
+
+int skcipher_walk_aead(struct skcipher_walk *walk, struct aead_request *req,
+                       bool atomic)
+{
+        walk->total = req->cryptlen;
+
+        return skcipher_walk_aead_common(walk, req, atomic);
+}
 EXPORT_SYMBOL_GPL(skcipher_walk_aead);
 
+int skcipher_walk_aead_encrypt(struct skcipher_walk *walk,
+                               struct aead_request *req, bool atomic)
+{
+        walk->total = req->cryptlen;
+
+        return skcipher_walk_aead_common(walk, req, atomic);
+}
+EXPORT_SYMBOL_GPL(skcipher_walk_aead_encrypt);
+
+int skcipher_walk_aead_decrypt(struct skcipher_walk *walk,
+                               struct aead_request *req, bool atomic)
+{
+        struct crypto_aead *tfm = crypto_aead_reqtfm(req);
+
+        walk->total = req->cryptlen - crypto_aead_authsize(tfm);
+
+        return skcipher_walk_aead_common(walk, req, atomic);
+}
+EXPORT_SYMBOL_GPL(skcipher_walk_aead_decrypt);
+
 static unsigned int crypto_skcipher_extsize(struct crypto_alg *alg)
 {
         if (alg->cra_type == &crypto_blkcipher_type)
diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
index d55041f45899..8735979ed341 100644
--- a/include/crypto/internal/skcipher.h
+++ b/include/crypto/internal/skcipher.h
@@ -149,6 +149,10 @@ int skcipher_walk_async(struct skcipher_walk *walk,
                         struct skcipher_request *req);
 int skcipher_walk_aead(struct skcipher_walk *walk, struct aead_request *req,
                        bool atomic);
+int skcipher_walk_aead_encrypt(struct skcipher_walk *walk,
+                               struct aead_request *req, bool atomic);
+int skcipher_walk_aead_decrypt(struct skcipher_walk *walk,
+                               struct aead_request *req, bool atomic);
 void skcipher_walk_complete(struct skcipher_walk *walk, int err);
 
 static inline void ablkcipher_request_complete(struct ablkcipher_request *req,