[PATCH v2 10/13] crypto: aes - Add CTR and XCTR support using library

[Eric Biggers <ebiggers@kernel.org>]

Implement the "ctr(aes)" and "xctr(aes)" crypto_skcipher algorithms
using the corresponding library functions.

Among other benefits, this allows the architecture-optimized AES-CTR and
AES-XCTR code to be migrated into the library while still leaving it
accessible via crypto_skcipher, eliminating lots of boilerplate code.

For now the cra_priority is set to just 110, since the
architecture-optimized implementations of these algorithms haven't yet
been migrated into the library.  It will be boosted once that happens.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 crypto/Kconfig |  1 +
 crypto/aes.c   | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/crypto/Kconfig b/crypto/Kconfig
index f413cfc9a3e2..5a198275e4fc 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -360,6 +360,7 @@ config CRYPTO_AES
 	select CRYPTO_LIB_AES
 	select CRYPTO_LIB_AES_CBC if CRYPTO_CBC != n || CRYPTO_CTS != n
 	select CRYPTO_LIB_AES_CBC_MACS if CRYPTO_CMAC != n || CRYPTO_XCBC != n || CRYPTO_CCM != n
+	select CRYPTO_LIB_AES_CTR if CRYPTO_CTR != n || CRYPTO_XCTR != n
 	select CRYPTO_LIB_AES_ECB if CRYPTO_ECB != n
 	select CRYPTO_HASH if CRYPTO_CMAC != n || CRYPTO_XCBC != n || CRYPTO_CCM != n
 	# CRYPTO_SKCIPHER should be selected only if a mode that needs it is
diff --git a/crypto/aes.c b/crypto/aes.c
index 2455abc29252..6b298e788630 100644
--- a/crypto/aes.c
+++ b/crypto/aes.c
@@ -7,6 +7,7 @@
 
 #include <crypto/aes-cbc-macs.h>
 #include <crypto/aes-cbc.h>
+#include <crypto/aes-ctr.h>
 #include <crypto/aes-ecb.h>
 #include <crypto/aes.h>
 #include <crypto/algapi.h>
@@ -456,6 +457,31 @@ crypto_aes_cbc_cts_decrypt(struct skcipher_request *req)
 	return crypto_aes_cbc_cts_crypt_nonlinear(req, /* enc= */ false);
 }
 
+/* AES-CTR */
+
+static __maybe_unused int crypto_aes_ctr_crypt(struct skcipher_request *req)
+{
+	const struct aes_enckey *key =
+		crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
+
+	AES_CRYPT_SG(aes_ctr, req->dst, req->src, req->cryptlen, 0, req->iv,
+		     key);
+	return 0;
+}
+
+/* AES-XCTR */
+
+static __maybe_unused int crypto_aes_xctr_crypt(struct skcipher_request *req)
+{
+	const struct aes_enckey *key =
+		crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
+	u64 ctr = 1;
+
+	AES_CRYPT_SG(aes_xctr, req->dst, req->src, req->cryptlen, 0, &ctr,
+		     req->iv, key);
+	return 0;
+}
+
 static struct skcipher_alg skcipher_algs[] = {
 #if IS_ENABLED(CONFIG_CRYPTO_ECB)
 	{
@@ -504,6 +530,40 @@ static struct skcipher_alg skcipher_algs[] = {
 		.decrypt = crypto_aes_cbc_cts_decrypt,
 	},
 #endif
+#if IS_ENABLED(CONFIG_CRYPTO_CTR)
+	{
+		.base.cra_name = "ctr(aes)",
+		.base.cra_driver_name = "ctr-aes-lib",
+		.base.cra_priority = 110,
+		.base.cra_blocksize = 1,
+		.base.cra_ctxsize = sizeof(struct aes_enckey),
+		.base.cra_module = THIS_MODULE,
+		.min_keysize = AES_MIN_KEY_SIZE,
+		.max_keysize = AES_MAX_KEY_SIZE,
+		.ivsize = AES_BLOCK_SIZE,
+		.chunksize = AES_BLOCK_SIZE,
+		.setkey = crypto_aes_skcipher_setenckey,
+		.encrypt = crypto_aes_ctr_crypt,
+		.decrypt = crypto_aes_ctr_crypt,
+	},
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_XCTR)
+	{
+		.base.cra_name = "xctr(aes)",
+		.base.cra_driver_name = "xctr-aes-lib",
+		.base.cra_priority = 110,
+		.base.cra_blocksize = 1,
+		.base.cra_ctxsize = sizeof(struct aes_enckey),
+		.base.cra_module = THIS_MODULE,
+		.min_keysize = AES_MIN_KEY_SIZE,
+		.max_keysize = AES_MAX_KEY_SIZE,
+		.ivsize = AES_BLOCK_SIZE,
+		.chunksize = AES_BLOCK_SIZE,
+		.setkey = crypto_aes_skcipher_setenckey,
+		.encrypt = crypto_aes_xctr_crypt,
+		.decrypt = crypto_aes_xctr_crypt,
+	},
+#endif
 };
 
 static int __init crypto_aes_mod_init(void)
@@ -576,3 +636,11 @@ MODULE_ALIAS_CRYPTO("cbc-aes-lib");
 MODULE_ALIAS_CRYPTO("cts(cbc(aes))");
 MODULE_ALIAS_CRYPTO("cts-cbc-aes-lib");
 #endif
+#if IS_ENABLED(CONFIG_CRYPTO_CTR)
+MODULE_ALIAS_CRYPTO("ctr(aes)");
+MODULE_ALIAS_CRYPTO("ctr-aes-lib");
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_XCTR)
+MODULE_ALIAS_CRYPTO("xctr(aes)");
+MODULE_ALIAS_CRYPTO("xctr-aes-lib");
+#endif
-- 
2.55.0