1 files changed, 60 insertions, 0 deletions
diff --git a/libotr/libotr-4.1.1/toolkit/ctrmode.c b/libotr/libotr-4.1.1/toolkit/ctrmode.c
new file mode 100644
index 0000000..987f29c
--- /dev/null
+++ b/libotr/libotr-4.1.1/toolkit/ctrmode.c
@@ -0,0 +1,60 @@
+/*
+ *  Off-the-Record Messaging Toolkit
+ *  Copyright (C) 2004-2012  Ian Goldberg, Chris Alexander, Nikita Borisov
+ *                           <otr@cypherpunks.ca>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of version 2 of the GNU General Public License as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/* system headers */
+#include <stdlib.h>
+#include <string.h>
+
+/* toolkit headers */
+#include "aes.h"
+
+/* Encrypt or decrypt data in AES-CTR mode.  (The operations are the
+ * same.)  We roll our own here just to double-check that the calls
+ * libotr makes to libgcrypt are doing the right thing. */
+void aes_ctr_crypt(unsigned char *out, const unsigned char *in, size_t len,
+	unsigned char key[16], unsigned char ctrtop[8])
+{
+    unsigned char ctr[16], encctr[16];
+    aes_context aesc;
+
+    aes_set_key(&aesc, key, 128);
+
+    memmove(ctr, ctrtop, 8);
+    memset(ctr+8, 0, 8);
+
+    while(len > 0) {
+	/* How much to do at a time? */
+	size_t i;
+	size_t amt = len;
+	if (amt > 16) amt = 16;
+	aes_encrypt(&aesc, ctr, encctr);
+	for(i=0;i<amt;++i) {
+	    out[i] = in[i] ^ encctr[i];
+	}
+
+	/* Increment the counter */
+	for (i=16;i>0;--i) {
+	    if (++ctr[i-1] != 0) break;
+	}
+
+	out += amt;
+	in += amt;
+	len -= amt;
+    }
+}