1 files changed, 114 insertions, 0 deletions

diff --git a/cipher-chachapoly.c b/cipher-chachapoly.c
new file mode 100644
index 000000000..91b0830fd
--- /dev/null
+++ b/cipher-chachapoly.c
@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2013 Damien Miller <djm@mindrot.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.
+ */
+
+/* $OpenBSD: cipher-chachapoly.c,v 1.3 2013/12/15 21:42:35 djm Exp $ */
+
+#include "includes.h"
+
+#include <sys/types.h>
+#include <stdarg.h> /* needed for log.h */
+#include <string.h>
+#include <stdio.h>  /* needed for misc.h */
+
+#include "log.h"
+#include "misc.h"
+#include "cipher-chachapoly.h"
+
+void chachapoly_init(struct chachapoly_ctx *ctx,
+    const u_char *key, u_int keylen)
+{
+        if (keylen != (32 + 32)) /* 2 x 256 bit keys */
+                fatal("%s: invalid keylen %u", __func__, keylen);
+        chacha_keysetup(&ctx->main_ctx, key, 256);
+        chacha_keysetup(&ctx->header_ctx, key + 32, 256);
+}
+
+/*
+ * chachapoly_crypt() operates as following:
+ * En/decrypt with header key 'aadlen' bytes from 'src', storing result
+ * to 'dest'. The ciphertext here is treated as additional authenticated
+ * data for MAC calculation.
+ * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use
+ * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication
+ * tag. This tag is written on encryption and verified on decryption.
+ */
+int
+chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest,
+    const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt)
+{
+        u_char seqbuf[8];
+        const u_char one[8] = { 1, 0, 0, 0, 0, 0, 0, 0 }; /* NB little-endian */
+        u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];
+        int r = -1;
+
+        /*
+         * Run ChaCha20 once to generate the Poly1305 key. The IV is the
+         * packet sequence number.
+         */
+        bzero(poly_key, sizeof(poly_key));
+        put_u64(seqbuf, seqnr);
+        chacha_ivsetup(&ctx->main_ctx, seqbuf, NULL);
+        chacha_encrypt_bytes(&ctx->main_ctx,
+            poly_key, poly_key, sizeof(poly_key));
+        /* Set Chacha's block counter to 1 */
+        chacha_ivsetup(&ctx->main_ctx, seqbuf, one);
+
+        /* If decrypting, check tag before anything else */
+        if (!do_encrypt) {
+                const u_char *tag = src + aadlen + len;
+
+                poly1305_auth(expected_tag, src, aadlen + len, poly_key);
+                if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0)
+                        goto out;
+        }
+        /* Crypt additional data */
+        if (aadlen) {
+                chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
+                chacha_encrypt_bytes(&ctx->header_ctx, src, dest, aadlen);
+        }
+        chacha_encrypt_bytes(&ctx->main_ctx, src + aadlen,
+            dest + aadlen, len);
+
+        /* If encrypting, calculate and append tag */
+        if (do_encrypt) {
+                poly1305_auth(dest + aadlen + len, dest, aadlen + len,
+                    poly_key);
+        }
+        r = 0;
+
+ out:
+        bzero(expected_tag, sizeof(expected_tag));
+        bzero(seqbuf, sizeof(seqbuf));
+        bzero(poly_key, sizeof(poly_key));
+        return r;
+}
+
+/* Decrypt and extract the encrypted packet length */
+int
+chachapoly_get_length(struct chachapoly_ctx *ctx,
+    u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
+{
+        u_char buf[4], seqbuf[8];
+
+        if (len < 4)
+                return -1; /* Insufficient length */
+        put_u64(seqbuf, seqnr);
+        chacha_ivsetup(&ctx->header_ctx, seqbuf, NULL);
+        chacha_encrypt_bytes(&ctx->header_ctx, cp, buf, 4);
+        *plenp = get_u32(buf);
+        return 0;
+}
+