[PATCH v8 17/18] crypto: Add aes-helpers file to support some AES modes

[Harald Freudenberger <freude@linux.ibm.com>]

Add a new file crypto/aes-helpers.c with simple functions
to support some AES modes:
- AES cbc: AES_cbc_encrypt() AES_cbc_decrypt()
- AES ctr: AES_ctr_encrypt()
- AES xts: AES_xts_encrypt() AES_xts_decrypt()
and some AES related helpers:
- AES_xor()
- AES_xts_prep_next_tweak()

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Finn Callies <fcallies@linux.ibm.com>
---
 crypto/aes-helpers.c | 106 +++++++++++++++++++++++++++++++++++++++++++
 crypto/meson.build   |   1 +
 include/crypto/aes.h |  14 ++++++
 3 files changed, 121 insertions(+)
 create mode 100644 crypto/aes-helpers.c

diff --git a/crypto/aes-helpers.c b/crypto/aes-helpers.c
new file mode 100644
index 0000000000..065a7afabf
--- /dev/null
+++ b/crypto/aes-helpers.c
@@ -0,0 +1,106 @@
+/*
+ * AES helper functions and mode implementations
+ *
+ *  Authors:
+ *   Harald Freudenberger <freude@linux.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include "crypto/aes.h"
+
+void AES_xor(const unsigned char *src1, const unsigned char *src2,
+             unsigned char *dst)
+{
+    int i;
+
+    for (i = 0; i < AES_BLOCK_SIZE; i++) {
+        dst[i] = src1[i] ^ src2[i];
+    }
+}
+
+void AES_cbc_encrypt(const unsigned char *in, unsigned char *out,
+                     unsigned char *iv, const AES_KEY *key)
+{
+    unsigned char buf[AES_BLOCK_SIZE];
+
+    /* in xor iv => buf */
+    AES_xor(in, iv, buf);
+    /* encrypt buf => out */
+    AES_encrypt(buf, out, key);
+    /* prep iv for next round */
+    memcpy(iv, out, AES_BLOCK_SIZE);
+}
+
+void AES_cbc_decrypt(const unsigned char *in, unsigned char *out,
+                     unsigned char *iv, const AES_KEY *key)
+{
+    unsigned char buf[AES_BLOCK_SIZE];
+
+    /* decrypt in => buf */
+    AES_decrypt(in, buf, key);
+    /* buf xor iv => out */
+    AES_xor(buf, iv, out);
+    /* prep iv for next round */
+    memcpy(iv, in, AES_BLOCK_SIZE);
+}
+
+void AES_ctr_encrypt(const unsigned char *in, unsigned char *out,
+                     const unsigned char *ctr, const AES_KEY *key)
+{
+    unsigned char buf[AES_BLOCK_SIZE];
+
+    /* encrypt ctr => buf */
+    AES_encrypt(ctr, buf, key);
+    /* exor input data with encrypted ctr => out */
+    AES_xor(in, buf, out);
+}
+
+/* Tweak calculation for AES XTS.
+ * Multiply tweak by α (x) in GF(2^128) per IEEE 1619-2007. The tweak
+ * is a 128-bit little-endian integer (tweak[0]=LSB, tweak[15]=MSB).
+ * This implementation has been verified on litte and big endian.
+ */
+void AES_xts_prep_next_tweak(unsigned char *tweak)
+{
+    unsigned char carry;
+    int i;
+
+    carry = tweak[AES_BLOCK_SIZE - 1] >> 7;
+
+    for (i = AES_BLOCK_SIZE - 1; i > 0; i--) {
+        tweak[i] = (unsigned char)((tweak[i] << 1) | (tweak[i - 1] >> 7));
+    }
+
+    tweak[i] = (unsigned char)(tweak[i] << 1);
+    tweak[i] ^= (unsigned char)(0x87 & (unsigned char)(-(unsigned char)carry));
+}
+
+void AES_xts_encrypt(const unsigned char *in, unsigned char *out,
+                     const unsigned char *tweak, const AES_KEY *key)
+{
+    unsigned char buf1[AES_BLOCK_SIZE], buf2[AES_BLOCK_SIZE];
+
+    /* in xor tweak => buf1 */
+    AES_xor(in, tweak, buf1);
+    /* encrypt buf1 => buf2 */
+    AES_encrypt(buf1, buf2, key);
+    /* buf2 xor tweak => out */
+    AES_xor(buf2, tweak, out);
+}
+
+void AES_xts_decrypt(const unsigned char *in, unsigned char *out,
+                     const unsigned char *tweak, const AES_KEY *key)
+{
+    unsigned char buf1[AES_BLOCK_SIZE], buf2[AES_BLOCK_SIZE];
+
+    /* in xor tweak => buf1 */
+    AES_xor(in, tweak, buf1);
+    /* encrypt buf1 => buf2 */
+    AES_decrypt(buf1, buf2, key);
+    /* buf2 xor tweak => out */
+    AES_xor(buf2, tweak, out);
+}
diff --git a/crypto/meson.build b/crypto/meson.build
index b51597a879..675f27311c 100644
--- a/crypto/meson.build
+++ b/crypto/meson.build
@@ -55,6 +55,7 @@ system_ss.add(when: gnutls, if_true: files('tls-cipher-suites.c'))
 
 util_ss.add(files(
   'aes.c',
+  'aes-helpers.c',
   'clmul.c',
   'init.c',
   'sm4.c',
diff --git a/include/crypto/aes.h b/include/crypto/aes.h
index 381f24c902..df6239cb9c 100644
--- a/include/crypto/aes.h
+++ b/include/crypto/aes.h
@@ -37,4 +37,18 @@ AES_Td0[x] = Si[x].[0e, 09, 0d, 0b];
 
 extern const uint32_t AES_Te0[256], AES_Td0[256];
 
+void AES_xor(const unsigned char *src1, const unsigned char *src2,
+             unsigned char *dst);
+void AES_cbc_encrypt(const unsigned char *in, unsigned char *out,
+                     unsigned char *iv, const AES_KEY *key);
+void AES_cbc_decrypt(const unsigned char *in, unsigned char *out,
+                     unsigned char *iv, const AES_KEY *key);
+void  AES_ctr_encrypt(const unsigned char *in, unsigned char *out,
+                      const unsigned char *ctr, const AES_KEY *key);
+void AES_xts_prep_next_tweak(unsigned char *tweak);
+void AES_xts_encrypt(const unsigned char *in, unsigned char *out,
+                     const unsigned char *tweak, const AES_KEY *key);
+void AES_xts_decrypt(const unsigned char *in, unsigned char *out,
+                     const unsigned char *tweak, const AES_KEY *key);
+
 #endif
-- 
2.43.0