1 files changed, 78 insertions, 0 deletions

diff --git a/cipher-aesctr.c b/cipher-aesctr.c
new file mode 100644
index 000000000..a4cf61e41
--- /dev/null
+++ b/cipher-aesctr.c
@@ -0,0 +1,78 @@
+/* $OpenBSD: cipher-aesctr.c,v 1.1 2014/04/29 15:39:33 markus Exp $ */
+/*
+ * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <string.h>
+
+#include "cipher-aesctr.h"
+
+/*
+ * increment counter 'ctr',
+ * the counter is of size 'len' bytes and stored in network-byte-order.
+ * (LSB at ctr[len-1], MSB at ctr[0])
+ */
+static __inline__ void
+aesctr_inc(u8 *ctr, u32 len)
+{
+        ssize_t i;
+
+#ifndef CONSTANT_TIME_INCREMENT
+        for (i = len - 1; i >= 0; i--)
+                if (++ctr[i])   /* continue on overflow */
+                        return;
+#else
+        u8 x, add = 1;
+
+        for (i = len - 1; i >= 0; i--) {
+                ctr[i] += add;
+                /* constant time for: x = ctr[i] ? 1 : 0 */
+                x = ctr[i];
+                x = (x | (x >> 4)) & 0xf;
+                x = (x | (x >> 2)) & 0x3;
+                x = (x | (x >> 1)) & 0x1;
+                add *= (x^1);
+        }
+#endif
+}
+
+void
+aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
+{
+        x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
+}
+
+void
+aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
+{
+        memcpy(x->ctr, iv, AES_BLOCK_SIZE);
+}
+
+void
+aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
+{
+        u32 n = 0;
+        u8 buf[AES_BLOCK_SIZE];
+
+        while ((bytes--) > 0) {
+                if (n == 0) {
+                        rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
+                        aesctr_inc(x->ctr, AES_BLOCK_SIZE);
+                }
+                *(c++) = *(m++) ^ buf[n];
+                n = (n + 1) % AES_BLOCK_SIZE;
+        }
+}