- markus@cvs.openbsd.org 2003/05/17 04:27:52

     [cipher.c cipher-ctr.c myproposal.h]
     experimental support for aes-ctr modes from
     http://www.ietf.org/internet-drafts/draft-ietf-secsh-newmodes-00.txt
     ok djm@

1 files changed, 149 insertions, 0 deletions

diff --git a/cipher-ctr.c b/cipher-ctr.c
new file mode 100644
index 00000000..8d548c70
--- /dev/null
+++ b/cipher-ctr.c
@@ -0,0 +1,149 @@
+/*
+ * Copyright (c) 2003 Markus Friedl.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "includes.h"
+RCSID("$OpenBSD: cipher-ctr.c,v 1.1 2003/05/17 04:27:52 markus Exp $");
+
+#include <openssl/evp.h>
+
+#include "log.h"
+#include "xmalloc.h"
+
+#if OPENSSL_VERSION_NUMBER < 0x00907000L
+#include "rijndael.h"
+#define AES_KEY rijndael_ctx
+#define AES_BLOCK_SIZE 16
+#define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b)
+#define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1)
+#else
+#include <openssl/aes.h>
+#endif
+
+const EVP_CIPHER *evp_aes_128_ctr(void);
+void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
+
+struct ssh_aes_ctr_ctx
+{
+	AES_KEY		aes_ctx;
+	u_char		aes_counter[AES_BLOCK_SIZE];
+};
+
+/*
+ * 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 void
+ssh_ctr_inc(u_char *ctr, u_int len)
+{
+	int i;
+
+	for (i = len - 1; i >= 0; i--)
+		if (++ctr[i])	/* continue on overflow */
+			return;
+}
+
+static int
+ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
+    u_int len)
+{
+	struct ssh_aes_ctr_ctx *c;
+	u_int n = 0;
+	u_char buf[AES_BLOCK_SIZE];
+
+	if (len == 0)
+		return (1);
+	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
+		return (0);
+
+	while ((len--) > 0) {
+		if (n == 0) {
+			AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
+			ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
+		}
+		*(dest++) = *(src++) ^ buf[n];
+		n = (n + 1) % AES_BLOCK_SIZE;
+	}
+	return (1);
+}
+
+static int
+ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
+    int enc)
+{
+	struct ssh_aes_ctr_ctx *c;
+
+	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
+		c = xmalloc(sizeof(*c));
+		EVP_CIPHER_CTX_set_app_data(ctx, c);
+	}
+	if (key != NULL)
+                AES_set_encrypt_key(key, ctx->key_len * 8, &c->aes_ctx);
+	if (iv != NULL)
+		memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
+	return (1);
+}
+
+static int
+ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
+{
+	struct ssh_aes_ctr_ctx *c;
+
+	if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
+		memset(c, 0, sizeof(*c));
+		xfree(c);
+		EVP_CIPHER_CTX_set_app_data(ctx, NULL);
+	}
+	return (1);
+}
+
+void
+ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
+{
+	struct ssh_aes_ctr_ctx *c;
+
+	if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
+		fatal("ssh_aes_ctr_iv: no context");
+	if (doset)
+		memcpy(c->aes_counter, iv, len);
+	else
+		memcpy(iv, c->aes_counter, len);
+}
+
+const EVP_CIPHER *
+evp_aes_128_ctr(void)
+{
+	static EVP_CIPHER aes_ctr;
+
+	memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
+	aes_ctr.nid = NID_undef;
+	aes_ctr.block_size = AES_BLOCK_SIZE;
+	aes_ctr.iv_len = AES_BLOCK_SIZE;
+	aes_ctr.key_len = 16;
+	aes_ctr.init = ssh_aes_ctr_init;
+	aes_ctr.cleanup = ssh_aes_ctr_cleanup;
+	aes_ctr.do_cipher = ssh_aes_ctr;
+	aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
+	    EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
+	return (&aes_ctr);
+}