chacha20+poly1305 authenticated encryption
Damien Miller
djm at mindrot.org
Thu Nov 14 13:56:31 EST 2013
Hi,
Here's a diff to implement ChaCha20+Poly1305 as an authenticated
encryption mode. It authenticates the packet length and payload, and
uses a separate ChaCh20 instance to encrypt the packet length to
preserve privacy of packet lengths* while avoiding any decryption
oracle for the main packet payload. More details are in the
PROTOCOL.chacha20poly1305 file in the diff.
It's largely inspired by Adam Langley's similar mode for TLS
(http://tools.ietf.org/html/draft-agl-tls-chacha20poly1305-03) but
differs in the padding used for the Poly1305 MAC and in the use of a
separate ChaCha20 instance to encrypt the packet lengths.
The current implementation uses unoptimised implementations of Poly1305
and ChaCha20, but some basic performance tests have it running at speeds
comparable to arcfour128.
Comments welcome.
-d
* the packet lengths will be encrypted, but still subject to measurement
by traffic analysis like most other ciphers.
Index: PROTOCOL
===================================================================
RCS file: /cvs/src/usr.bin/ssh/PROTOCOL,v
retrieving revision 1.21
diff -u -p -r1.21 PROTOCOL
--- PROTOCOL 17 Oct 2013 00:30:13 -0000 1.21
+++ PROTOCOL 14 Nov 2013 02:10:29 -0000
@@ -91,6 +91,11 @@ an MAC algorithm. Additionally, if AES-G
the exchanged MAC algorithms are ignored and there doesn't have to be
a matching MAC.
+1.7 transport: chacha20-poly1305 at openssh.com authenticated encryption
+
+OpenSSH supports authenticated encryption using ChaCha20 and Poly1305
+as described in PROTOCOL.chacha20poly1305.
+
2. Connection protocol changes
2.1. connection: Channel write close extension "eow at openssh.com"
Index: PROTOCOL.chacha20poly1305
===================================================================
RCS file: PROTOCOL.chacha20poly1305
diff -N PROTOCOL.chacha20poly1305
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ PROTOCOL.chacha20poly1305 14 Nov 2013 02:10:29 -0000
@@ -0,0 +1,99 @@
+This document describes the chacha20-poly1305 at openssh.com authenticated
+encryption cipher supported by OpenSSH.
+
+Background
+----------
+
+ChaCha20 is a stream cipher designed by Daniel Bernstein and described
+in [1]. It operates by permuting 128 fixed bits, 128 or 256 bits of key,
+a 64 bit nonce and a 64 bit counter into 64 bytes of stream output.
+
+Poly1305[2] also by Daniel Bernstien is a one-time Carter-Wegman MAC
+that computes a 128 bit integrity tag given a message and a 256 bit key.
+
+The chacha20-poly1305 at openssh.com combines these two primitives into an
+authenticated encryption mode. The construction used is based on that
+proposed for TLS by Adam Langley in [3], but differs in the layout of
+data passed to the MAC and in the addition of encyption of the packet
+lengths.
+
+Negotiation
+-----------
+
+The chacha20-poly1305 at openssh.com offers both encryption and
+authentication. As such, no separate MAC is required. If the
+chacha20-poly1305 at openssh.com cipher is selected in key exchange,
+the offered MAC algorithms are ignored and no MAC is required to be
+negotiated.
+
+Detailed Construction
+---------------------
+
+The chacha20-poly1305 at openssh.com cipher requires 512 bits of key
+material as output from the SSH key exchange. This forms two 256 bit
+keys (K_1 and K_2), used by two separate instances of chacha20.
+
+The instance keyed by K_1 is a pure stream cipher that is used only
+to encrypt the 4 byte packet length field. The second instance,
+keyed by K_2, is used in conjunction with poly1305 to build an AEAD
+(Authenticated Encryption with Associated Data) that is used to encrypt
+and authenticate the entire packet.
+
+Two separate cipher instances are used here so as to keep the packet
+lengths confidential but not create an oracle for the packet payload
+encryption by decrypting and using the packet length prior to checking
+the MAC. By using an independently-keyed cipher instance to encrypt the
+length, an active attacker seeking to exploit the packet input handling
+as a decryption oracle can learn nothing about the payload contents or
+its MAC (assuming key derivation is secure).
+
+The AEAD is constructed as follows: for each packet, generate a Poly1305
+key by taking the first 256 bits of ChaCha20 stream output generated
+using K_2, an IV consisting of the packet sequence number encoded as an
+uint64 under the SSH wire encoding rules and a ChaCha20 block counter of
+zero. The K_2 ChaCha20 block counter is then set to the little-endian
+encoding of 1 (i.e. {1, 0, 0, 0, 0, 0, 0, 0}) and this instance is used
+for encryption of the packet payload.
+
+Packet Handling
+---------------
+
+When receiving a packet, the length must be decrypted first. When 4
+bytes of ciphertext length have been received, they may be decrypted
+using K_1 to obtain the plaintext length.
+
+Once the entire packet has been received, the MAC MUST be checked
+before decryption. A per-packet Poly1305 key is generated as described
+above and the MAC tag calculated using Poly1305 with this key over the
+ciphertext of the packet length and the payload together. The calculated
+MAC is then compared with the one appended to the packet and the packet
+decrypted using ChaCha20 as described above (with K_2, the packet
+sequence number as nonce and a starting block counter of 1).
+
+To send a packet, first encode the 4 byte length and encrypt it using
+K_1. Encrypt the packet payload (using K_2) and append it to the
+encrypted length. Finally, calculate a MAC tag and append it.
+
+Rekeying
+--------
+
+ChaCha20 must never reuse a {key, nonce} for encryption nor may it be
+used to encrypt more than 2^70 bytes under the same {key, nonce}. The
+SSH Transport protocol (RFC4253) recommends rekeying every 1GB of data
+sent or received. If this recommendation is followed, then
+chacha20-poly1305 at openssh.com requires no special handling in this area.
+
+References
+----------
+
+[1] "ChaCha, a variant of Salsa20", Daniel Bernstein
+ http://cr.yp.to/chacha/chacha-20080128.pdf
+
+[2] "The Poly1305-AES message-authentication code", Daniel Bernstein
+ http://cr.yp.to/mac/poly1305-20050329.pdf
+
+[3] "ChaCha20 and Poly1305 based Cipher Suites for TLS", Adam Langley
+ http://tools.ietf.org/html/draft-agl-tls-chacha20poly1305-03
+
+$OpenBSD$
+
Index: authfile.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/authfile.c,v
retrieving revision 1.97
diff -u -p -r1.97 authfile.c
--- authfile.c 17 May 2013 00:13:13 -0000 1.97
+++ authfile.c 14 Nov 2013 02:10:29 -0000
@@ -144,7 +144,7 @@ key_private_rsa1_to_blob(Key *key, Buffe
cipher_set_key_string(&ciphercontext, cipher, passphrase,
CIPHER_ENCRYPT);
- cipher_crypt(&ciphercontext, cp,
+ cipher_crypt(&ciphercontext, 0, cp,
buffer_ptr(&buffer), buffer_len(&buffer), 0, 0);
cipher_cleanup(&ciphercontext);
memset(&ciphercontext, 0, sizeof(ciphercontext));
@@ -462,7 +462,7 @@ key_parse_private_rsa1(Buffer *blob, con
/* Rest of the buffer is encrypted. Decrypt it using the passphrase. */
cipher_set_key_string(&ciphercontext, cipher, passphrase,
CIPHER_DECRYPT);
- cipher_crypt(&ciphercontext, cp,
+ cipher_crypt(&ciphercontext, 0, cp,
buffer_ptr(©), buffer_len(©), 0, 0);
cipher_cleanup(&ciphercontext);
memset(&ciphercontext, 0, sizeof(ciphercontext));
Index: chacha.c
===================================================================
RCS file: chacha.c
diff -N chacha.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ chacha.c 14 Nov 2013 02:10:29 -0000
@@ -0,0 +1,217 @@
+/*
+chacha-merged.c version 20080118
+D. J. Bernstein
+Public domain.
+*/
+
+#include "chacha.h"
+
+/* $OpenBSD$ */
+
+typedef unsigned char u8;
+typedef unsigned int u32;
+
+typedef struct chacha_ctx chacha_ctx;
+
+#define U8C(v) (v##U)
+#define U32C(v) (v##U)
+
+#define U8V(v) ((u8)(v) & U8C(0xFF))
+#define U32V(v) ((u32)(v) & U32C(0xFFFFFFFF))
+
+#define ROTL32(v, n) \
+ (U32V((v) << (n)) | ((v) >> (32 - (n))))
+
+#define U8TO32_LITTLE(p) \
+ (((u32)((p)[0]) ) | \
+ ((u32)((p)[1]) << 8) | \
+ ((u32)((p)[2]) << 16) | \
+ ((u32)((p)[3]) << 24))
+
+#define U32TO8_LITTLE(p, v) \
+ do { \
+ (p)[0] = U8V((v) ); \
+ (p)[1] = U8V((v) >> 8); \
+ (p)[2] = U8V((v) >> 16); \
+ (p)[3] = U8V((v) >> 24); \
+ } while (0)
+
+#define ROTATE(v,c) (ROTL32(v,c))
+#define XOR(v,w) ((v) ^ (w))
+#define PLUS(v,w) (U32V((v) + (w)))
+#define PLUSONE(v) (PLUS((v),1))
+
+#define QUARTERROUND(a,b,c,d) \
+ a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
+ c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
+ a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
+ c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
+
+static const char sigma[16] = "expand 32-byte k";
+static const char tau[16] = "expand 16-byte k";
+
+void
+chacha_keysetup(chacha_ctx *x,const u8 *k,u32 kbits)
+{
+ const char *constants;
+
+ x->input[4] = U8TO32_LITTLE(k + 0);
+ x->input[5] = U8TO32_LITTLE(k + 4);
+ x->input[6] = U8TO32_LITTLE(k + 8);
+ x->input[7] = U8TO32_LITTLE(k + 12);
+ if (kbits == 256) { /* recommended */
+ k += 16;
+ constants = sigma;
+ } else { /* kbits == 128 */
+ constants = tau;
+ }
+ x->input[8] = U8TO32_LITTLE(k + 0);
+ x->input[9] = U8TO32_LITTLE(k + 4);
+ x->input[10] = U8TO32_LITTLE(k + 8);
+ x->input[11] = U8TO32_LITTLE(k + 12);
+ x->input[0] = U8TO32_LITTLE(constants + 0);
+ x->input[1] = U8TO32_LITTLE(constants + 4);
+ x->input[2] = U8TO32_LITTLE(constants + 8);
+ x->input[3] = U8TO32_LITTLE(constants + 12);
+}
+
+void
+chacha_ivsetup(chacha_ctx *x, const u8 *iv, const u8 *counter)
+{
+ x->input[12] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
+ x->input[13] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
+ x->input[14] = U8TO32_LITTLE(iv + 0);
+ x->input[15] = U8TO32_LITTLE(iv + 4);
+}
+
+void
+chacha_encrypt_bytes(chacha_ctx *x,const u8 *m,u8 *c,u32 bytes)
+{
+ u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
+ u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
+ u8 *ctarget = NULL;
+ u8 tmp[64];
+ u_int i;
+
+ if (!bytes) return;
+
+ j0 = x->input[0];
+ j1 = x->input[1];
+ j2 = x->input[2];
+ j3 = x->input[3];
+ j4 = x->input[4];
+ j5 = x->input[5];
+ j6 = x->input[6];
+ j7 = x->input[7];
+ j8 = x->input[8];
+ j9 = x->input[9];
+ j10 = x->input[10];
+ j11 = x->input[11];
+ j12 = x->input[12];
+ j13 = x->input[13];
+ j14 = x->input[14];
+ j15 = x->input[15];
+
+ for (;;) {
+ if (bytes < 64) {
+ for (i = 0;i < bytes;++i) tmp[i] = m[i];
+ m = tmp;
+ ctarget = c;
+ c = tmp;
+ }
+ x0 = j0;
+ x1 = j1;
+ x2 = j2;
+ x3 = j3;
+ x4 = j4;
+ x5 = j5;
+ x6 = j6;
+ x7 = j7;
+ x8 = j8;
+ x9 = j9;
+ x10 = j10;
+ x11 = j11;
+ x12 = j12;
+ x13 = j13;
+ x14 = j14;
+ x15 = j15;
+ for (i = 20;i > 0;i -= 2) {
+ QUARTERROUND( x0, x4, x8,x12)
+ QUARTERROUND( x1, x5, x9,x13)
+ QUARTERROUND( x2, x6,x10,x14)
+ QUARTERROUND( x3, x7,x11,x15)
+ QUARTERROUND( x0, x5,x10,x15)
+ QUARTERROUND( x1, x6,x11,x12)
+ QUARTERROUND( x2, x7, x8,x13)
+ QUARTERROUND( x3, x4, x9,x14)
+ }
+ x0 = PLUS(x0,j0);
+ x1 = PLUS(x1,j1);
+ x2 = PLUS(x2,j2);
+ x3 = PLUS(x3,j3);
+ x4 = PLUS(x4,j4);
+ x5 = PLUS(x5,j5);
+ x6 = PLUS(x6,j6);
+ x7 = PLUS(x7,j7);
+ x8 = PLUS(x8,j8);
+ x9 = PLUS(x9,j9);
+ x10 = PLUS(x10,j10);
+ x11 = PLUS(x11,j11);
+ x12 = PLUS(x12,j12);
+ x13 = PLUS(x13,j13);
+ x14 = PLUS(x14,j14);
+ x15 = PLUS(x15,j15);
+
+ x0 = XOR(x0,U8TO32_LITTLE(m + 0));
+ x1 = XOR(x1,U8TO32_LITTLE(m + 4));
+ x2 = XOR(x2,U8TO32_LITTLE(m + 8));
+ x3 = XOR(x3,U8TO32_LITTLE(m + 12));
+ x4 = XOR(x4,U8TO32_LITTLE(m + 16));
+ x5 = XOR(x5,U8TO32_LITTLE(m + 20));
+ x6 = XOR(x6,U8TO32_LITTLE(m + 24));
+ x7 = XOR(x7,U8TO32_LITTLE(m + 28));
+ x8 = XOR(x8,U8TO32_LITTLE(m + 32));
+ x9 = XOR(x9,U8TO32_LITTLE(m + 36));
+ x10 = XOR(x10,U8TO32_LITTLE(m + 40));
+ x11 = XOR(x11,U8TO32_LITTLE(m + 44));
+ x12 = XOR(x12,U8TO32_LITTLE(m + 48));
+ x13 = XOR(x13,U8TO32_LITTLE(m + 52));
+ x14 = XOR(x14,U8TO32_LITTLE(m + 56));
+ x15 = XOR(x15,U8TO32_LITTLE(m + 60));
+
+ j12 = PLUSONE(j12);
+ if (!j12) {
+ j13 = PLUSONE(j13);
+ /* stopping at 2^70 bytes per nonce is user's responsibility */
+ }
+
+ U32TO8_LITTLE(c + 0,x0);
+ U32TO8_LITTLE(c + 4,x1);
+ U32TO8_LITTLE(c + 8,x2);
+ U32TO8_LITTLE(c + 12,x3);
+ U32TO8_LITTLE(c + 16,x4);
+ U32TO8_LITTLE(c + 20,x5);
+ U32TO8_LITTLE(c + 24,x6);
+ U32TO8_LITTLE(c + 28,x7);
+ U32TO8_LITTLE(c + 32,x8);
+ U32TO8_LITTLE(c + 36,x9);
+ U32TO8_LITTLE(c + 40,x10);
+ U32TO8_LITTLE(c + 44,x11);
+ U32TO8_LITTLE(c + 48,x12);
+ U32TO8_LITTLE(c + 52,x13);
+ U32TO8_LITTLE(c + 56,x14);
+ U32TO8_LITTLE(c + 60,x15);
+
+ if (bytes <= 64) {
+ if (bytes < 64) {
+ for (i = 0;i < bytes;++i) ctarget[i] = c[i];
+ }
+ x->input[12] = j12;
+ x->input[13] = j13;
+ return;
+ }
+ bytes -= 64;
+ c += 64;
+ m += 64;
+ }
+}
Index: chacha.h
===================================================================
RCS file: chacha.h
diff -N chacha.h
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ chacha.h 14 Nov 2013 02:10:29 -0000
@@ -0,0 +1,35 @@
+/* $OpenBSD$ */
+
+/*
+chacha-merged.c version 20080118
+D. J. Bernstein
+Public domain.
+*/
+
+#ifndef CHACHA_H
+#define CHACHA_H
+
+#include <sys/types.h>
+
+struct chacha_ctx {
+ u_int input[16];
+};
+
+#define CHACHA_MINKEYLEN 16
+#define CHACHA_NONCELEN 8
+#define CHACHA_CTRLEN 8
+#define CHACHA_STATELEN (CHACHA_NONCELEN+CHACHA_CTRLEN)
+#define CHACHA_BLOCKLEN 64
+
+void chacha_keysetup(struct chacha_ctx *x, const u_char *k, u_int kbits)
+ __attribute__((__bounded__(__minbytes__, 2, CHACHA_MINKEYLEN)));
+void chacha_ivsetup(struct chacha_ctx *x, const u_char *iv, const u_char *ctr)
+ __attribute__((__bounded__(__minbytes__, 2, CHACHA_NONCELEN)))
+ __attribute__((__bounded__(__minbytes__, 3, CHACHA_CTRLEN)));
+void chacha_encrypt_bytes(struct chacha_ctx *x, const u_char *m,
+ u_char *c, u_int bytes)
+ __attribute__((__bounded__(__buffer__, 2, 4)))
+ __attribute__((__bounded__(__buffer__, 3, 4)));
+
+#endif /* CHACHA_H */
+
Index: chacha20poly1305aead.c
===================================================================
RCS file: chacha20poly1305aead.c
diff -N chacha20poly1305aead.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ chacha20poly1305aead.c 14 Nov 2013 02:10:30 -0000
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2013 Damien Miller <djm at 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.
+ */
+
+#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 "chacha20poly1305aead.h"
+
+void cp_aead_init(struct chacha_poly_aead_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);
+}
+
+/*
+ * cp_aead_crypt() operates as following:
+ * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
+ * Theses bytes are treated as additional authenticated data.
+ * 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.
+ * Both 'aadlen' and 'authlen' can be set to 0.
+ */
+int
+cp_aead_crypt(struct chacha_poly_aead_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];
+ 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))
+ 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;
+}
+
+int
+cp_aead_get_length(struct chacha_poly_aead_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;
+}
+
Index: chacha20poly1305aead.h
===================================================================
RCS file: chacha20poly1305aead.h
diff -N chacha20poly1305aead.h
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ chacha20poly1305aead.h 14 Nov 2013 02:10:30 -0000
@@ -0,0 +1,41 @@
+/* $OpenBSD$ */
+
+/*
+ * Copyright (c) Damien Miller 2013 <djm at 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.
+ */
+#ifndef CHACHA_POLY_AEAD_H
+#define CHACHA_POLY_AEAD_H
+
+#include <sys/types.h>
+#include "chacha.h"
+#include "poly1305-donna-unrolled.h"
+
+#define CHACHA_KEYLEN 32 /* Only 256 bit keys used here */
+
+struct chacha_poly_aead_ctx {
+ struct chacha_ctx main_ctx, header_ctx;
+};
+
+void cp_aead_init(struct chacha_poly_aead_ctx *cpctx,
+ const u_char *key, u_int keylen)
+ __attribute__((__bounded__(__buffer__, 2, 3)));
+int cp_aead_crypt(struct chacha_poly_aead_ctx *cpctx, u_int seqnr,
+ u_char *dest, const u_char *src, u_int len, u_int aadlen, u_int authlen,
+ int do_encrypt);
+int cp_aead_get_length(struct chacha_poly_aead_ctx *cpctx,
+ u_int *plenp, u_int seqnr, const u_char *cp, u_int len)
+ __attribute__((__bounded__(__buffer__, 4, 5)));
+
+#endif /* CHACHA_POLY_AEAD_H */
Index: cipher.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/cipher.c,v
retrieving revision 1.90
diff -u -p -r1.90 cipher.c
--- cipher.c 7 Nov 2013 11:58:27 -0000 1.90
+++ cipher.c 14 Nov 2013 02:10:30 -0000
@@ -41,9 +41,11 @@
#include <string.h>
#include <stdarg.h>
+#include <stdio.h>
#include "xmalloc.h"
#include "log.h"
+#include "misc.h"
#include "cipher.h"
extern const EVP_CIPHER *evp_ssh1_bf(void);
@@ -58,7 +60,9 @@ struct Cipher {
u_int iv_len; /* defaults to block_size */
u_int auth_len;
u_int discard_len;
- u_int cbc_mode;
+ u_int flags;
+#define CFLAG_CBC (1<<0)
+#define CFLAG_CP_AEAD (1<<1)
const EVP_CIPHER *(*evptype)(void);
};
@@ -88,6 +92,8 @@ static const struct Cipher ciphers[] = {
SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm },
{ "aes256-gcm at openssh.com",
SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm },
+ { "chacha20-poly1305 at openssh.com",
+ SSH_CIPHER_SSH2, 8, 64, 0, 8, 0, CFLAG_CP_AEAD, NULL },
{ NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL }
};
@@ -136,7 +142,12 @@ cipher_authlen(const Cipher *c)
u_int
cipher_ivlen(const Cipher *c)
{
- return (c->iv_len ? c->iv_len : c->block_size);
+ /*
+ * Default is cipher block size, except for chacha20+poly1305 that
+ * needs no IV. XXX make iv_len == -1 default?
+ */
+ return (c->iv_len != 0 || (c->flags & CFLAG_CP_AEAD) != 0) ?
+ c->iv_len : c->block_size;
}
u_int
@@ -148,7 +159,7 @@ cipher_get_number(const Cipher *c)
u_int
cipher_is_cbc(const Cipher *c)
{
- return (c->cbc_mode);
+ return (c->flags & CFLAG_CBC) != 0;
}
u_int
@@ -264,8 +275,11 @@ cipher_init(CipherContext *cc, const Cip
ivlen, cipher->name);
cc->cipher = cipher;
+ if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0) {
+ cp_aead_init(&cc->cp_ctx, key, keylen);
+ return;
+ }
type = (*cipher->evptype)();
-
EVP_CIPHER_CTX_init(&cc->evp);
if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
(do_encrypt == CIPHER_ENCRYPT)) == 0)
@@ -310,9 +324,15 @@ cipher_init(CipherContext *cc, const Cip
* Both 'aadlen' and 'authlen' can be set to 0.
*/
void
-cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src,
+cipher_crypt(CipherContext *cc, u_int seqnr, u_char *dest, const u_char *src,
u_int len, u_int aadlen, u_int authlen)
{
+ if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0) {
+ if (cp_aead_crypt(&cc->cp_ctx, seqnr, dest, src, len, aadlen,
+ authlen, cc->encrypt) != 0)
+ fatal("Decryption integrity check failed");
+ return;
+ }
if (authlen) {
u_char lastiv[1];
@@ -354,10 +374,29 @@ cipher_crypt(CipherContext *cc, u_char *
}
}
+/*
+ * Extract the packet length for an AEAD cipher, including any decryption
+ * necessary beforehand.
+ */
+int
+cipher_aead_get_length(CipherContext *cc, u_int *plenp, u_int seqnr,
+ const u_char *cp, u_int len)
+{
+ if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0)
+ return cp_aead_get_length(&cc->cp_ctx, plenp, seqnr,
+ cp, len);
+ if (len < 4)
+ return -1;
+ *plenp = get_u32(cp);
+ return 0;
+}
+
void
cipher_cleanup(CipherContext *cc)
{
- if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
+ if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0)
+ bzero(&cc->cp_ctx, sizeof(&cc->cp_ctx));
+ else if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
}
@@ -397,6 +436,8 @@ cipher_get_keyiv_len(const CipherContext
if (c->number == SSH_CIPHER_3DES)
ivlen = 24;
+ else if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0)
+ ivlen = 0;
else
ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
return (ivlen);
@@ -408,6 +449,12 @@ cipher_get_keyiv(CipherContext *cc, u_ch
const Cipher *c = cc->cipher;
int evplen;
+ if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0) {
+ if (len != 0)
+ fatal("%s: wrong iv length %d != %d", __func__, len, 0);
+ return;
+ }
+
switch (c->number) {
case SSH_CIPHER_SSH2:
case SSH_CIPHER_DES:
@@ -438,6 +485,9 @@ cipher_set_keyiv(CipherContext *cc, u_ch
{
const Cipher *c = cc->cipher;
int evplen = 0;
+
+ if ((cc->cipher->flags & CFLAG_CP_AEAD) != 0)
+ return;
switch (c->number) {
case SSH_CIPHER_SSH2:
Index: cipher.h
===================================================================
RCS file: /cvs/src/usr.bin/ssh/cipher.h,v
retrieving revision 1.41
diff -u -p -r1.41 cipher.h
--- cipher.h 7 Nov 2013 11:58:27 -0000 1.41
+++ cipher.h 14 Nov 2013 02:10:30 -0000
@@ -38,6 +38,8 @@
#define CIPHER_H
#include <openssl/evp.h>
+#include "chacha20poly1305aead.h"
+
/*
* Cipher types for SSH-1. New types can be added, but old types should not
* be removed for compatibility. The maximum allowed value is 31.
@@ -65,7 +67,9 @@ struct Cipher;
struct CipherContext {
int plaintext;
int encrypt;
+ int is_cp_aead;
EVP_CIPHER_CTX evp;
+ struct chacha_poly_aead_ctx cp_ctx; /* XXX union with evp? */
const Cipher *cipher;
};
@@ -78,8 +82,10 @@ int ciphers_valid(const char *);
char *cipher_alg_list(char);
void cipher_init(CipherContext *, const Cipher *, const u_char *, u_int,
const u_char *, u_int, int);
-void cipher_crypt(CipherContext *, u_char *, const u_char *,
+void cipher_crypt(CipherContext *, u_int, u_char *, const u_char *,
u_int, u_int, u_int);
+int cipher_aead_get_length(CipherContext *, u_int *, u_int,
+ const u_char *, u_int);
void cipher_cleanup(CipherContext *);
void cipher_set_key_string(CipherContext *, const Cipher *, const char *, int);
u_int cipher_blocksize(const Cipher *);
Index: myproposal.h
===================================================================
RCS file: /cvs/src/usr.bin/ssh/myproposal.h,v
retrieving revision 1.33
diff -u -p -r1.33 myproposal.h
--- myproposal.h 2 Nov 2013 21:59:15 -0000 1.33
+++ myproposal.h 14 Nov 2013 02:10:30 -0000
@@ -52,6 +52,7 @@
"aes128-ctr,aes192-ctr,aes256-ctr," \
"arcfour256,arcfour128," \
"aes128-gcm at openssh.com,aes256-gcm at openssh.com," \
+ "chacha20-poly1305 at openssh.com," \
"aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc," \
"aes192-cbc,aes256-cbc,arcfour,rijndael-cbc at lysator.liu.se"
#define KEX_DEFAULT_MAC \
Index: packet.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/packet.c,v
retrieving revision 1.189
diff -u -p -r1.189 packet.c
--- packet.c 8 Nov 2013 00:39:15 -0000 1.189
+++ packet.c 14 Nov 2013 02:10:30 -0000
@@ -702,7 +702,7 @@ packet_send1(void)
buffer_append(&active_state->output, buf, 4);
cp = buffer_append_space(&active_state->output,
buffer_len(&active_state->outgoing_packet));
- cipher_crypt(&active_state->send_context, cp,
+ cipher_crypt(&active_state->send_context, 0, cp,
buffer_ptr(&active_state->outgoing_packet),
buffer_len(&active_state->outgoing_packet), 0, 0);
@@ -935,8 +935,8 @@ packet_send2_wrapped(void)
}
/* encrypt packet and append to output buffer. */
cp = buffer_append_space(&active_state->output, len + authlen);
- cipher_crypt(&active_state->send_context, cp,
- buffer_ptr(&active_state->outgoing_packet),
+ cipher_crypt(&active_state->send_context, active_state->p_send.seqnr,
+ cp, buffer_ptr(&active_state->outgoing_packet),
len - aadlen, aadlen, authlen);
/* append unencrypted MAC */
if (mac && mac->enabled) {
@@ -1196,7 +1196,7 @@ packet_read_poll1(void)
/* Decrypt data to incoming_packet. */
buffer_clear(&active_state->incoming_packet);
cp = buffer_append_space(&active_state->incoming_packet, padded_len);
- cipher_crypt(&active_state->receive_context, cp,
+ cipher_crypt(&active_state->receive_context, 0, cp,
buffer_ptr(&active_state->input), padded_len, 0, 0);
buffer_consume(&active_state->input, padded_len);
@@ -1267,10 +1267,12 @@ packet_read_poll2(u_int32_t *seqnr_p)
aadlen = (mac && mac->enabled && mac->etm) || authlen ? 4 : 0;
if (aadlen && active_state->packlen == 0) {
- if (buffer_len(&active_state->input) < 4)
+ if (cipher_aead_get_length(&active_state->receive_context,
+ &active_state->packlen,
+ active_state->p_read.seqnr,
+ buffer_ptr(&active_state->input),
+ buffer_len(&active_state->input)) != 0)
return SSH_MSG_NONE;
- cp = buffer_ptr(&active_state->input);
- active_state->packlen = get_u32(cp);
if (active_state->packlen < 1 + 4 ||
active_state->packlen > PACKET_MAX_SIZE) {
#ifdef PACKET_DEBUG
@@ -1290,7 +1292,8 @@ packet_read_poll2(u_int32_t *seqnr_p)
buffer_clear(&active_state->incoming_packet);
cp = buffer_append_space(&active_state->incoming_packet,
block_size);
- cipher_crypt(&active_state->receive_context, cp,
+ cipher_crypt(&active_state->receive_context,
+ active_state->p_read.seqnr, cp,
buffer_ptr(&active_state->input), block_size, 0, 0);
cp = buffer_ptr(&active_state->incoming_packet);
active_state->packlen = get_u32(cp);
@@ -1345,7 +1348,8 @@ packet_read_poll2(u_int32_t *seqnr_p)
macbuf = mac_compute(mac, active_state->p_read.seqnr,
buffer_ptr(&active_state->input), aadlen + need);
cp = buffer_append_space(&active_state->incoming_packet, aadlen + need);
- cipher_crypt(&active_state->receive_context, cp,
+ cipher_crypt(&active_state->receive_context,
+ active_state->p_read.seqnr, cp,
buffer_ptr(&active_state->input), need, aadlen, authlen);
buffer_consume(&active_state->input, aadlen + need + authlen);
/*
Index: poly1305-donna-unrolled.c
===================================================================
RCS file: poly1305-donna-unrolled.c
diff -N poly1305-donna-unrolled.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ poly1305-donna-unrolled.c 14 Nov 2013 02:10:30 -0000
@@ -0,0 +1,154 @@
+/*
+ * Public Domain poly1305-donna from Andrew M.
+ * https://github.com/floodyberry/poly1305-donna
+ */
+
+#include <sys/types.h>
+#include <stdint.h>
+
+#include "poly1305-donna-unrolled.h"
+
+#define mul32x32_64(a,b) ((uint64_t)(a) * (b))
+
+#define U8TO32_LE(p) \
+ (((uint32_t)((p)[0])) | \
+ ((uint32_t)((p)[1]) << 8) | \
+ ((uint32_t)((p)[2]) << 16) | \
+ ((uint32_t)((p)[3]) << 24))
+
+#define U32TO8_LE(p, v) \
+ do { \
+ (p)[0] = (uint8_t)((v)); \
+ (p)[1] = (uint8_t)((v) >> 8); \
+ (p)[2] = (uint8_t)((v) >> 16); \
+ (p)[3] = (uint8_t)((v) >> 24); \
+ } while (0)
+
+void
+poly1305_auth(unsigned char out[POLY1305_TAGLEN], const unsigned char *m, size_t inlen, const unsigned char key[POLY1305_KEYLEN]) {
+ uint32_t t0,t1,t2,t3;
+ uint32_t h0,h1,h2,h3,h4;
+ uint32_t r0,r1,r2,r3,r4;
+ uint32_t s1,s2,s3,s4;
+ uint32_t b, nb;
+ size_t j;
+ uint64_t t[5];
+ uint64_t f0,f1,f2,f3;
+ uint32_t g0,g1,g2,g3,g4;
+ uint64_t c;
+ unsigned char mp[16];
+
+ /* clamp key */
+ t0 = U8TO32_LE(key+0);
+ t1 = U8TO32_LE(key+4);
+ t2 = U8TO32_LE(key+8);
+ t3 = U8TO32_LE(key+12);
+
+ /* precompute multipliers */
+ r0 = t0 & 0x3ffffff; t0 >>= 26; t0 |= t1 << 6;
+ r1 = t0 & 0x3ffff03; t1 >>= 20; t1 |= t2 << 12;
+ r2 = t1 & 0x3ffc0ff; t2 >>= 14; t2 |= t3 << 18;
+ r3 = t2 & 0x3f03fff; t3 >>= 8;
+ r4 = t3 & 0x00fffff;
+
+ s1 = r1 * 5;
+ s2 = r2 * 5;
+ s3 = r3 * 5;
+ s4 = r4 * 5;
+
+ /* init state */
+ h0 = 0;
+ h1 = 0;
+ h2 = 0;
+ h3 = 0;
+ h4 = 0;
+
+ /* full blocks */
+ if (inlen < 16) goto poly1305_donna_atmost15bytes;
+poly1305_donna_16bytes:
+ m += 16;
+ inlen -= 16;
+
+ t0 = U8TO32_LE(m-16);
+ t1 = U8TO32_LE(m-12);
+ t2 = U8TO32_LE(m-8);
+ t3 = U8TO32_LE(m-4);
+
+ h0 += t0 & 0x3ffffff;
+ h1 += ((((uint64_t)t1 << 32) | t0) >> 26) & 0x3ffffff;
+ h2 += ((((uint64_t)t2 << 32) | t1) >> 20) & 0x3ffffff;
+ h3 += ((((uint64_t)t3 << 32) | t2) >> 14) & 0x3ffffff;
+ h4 += (t3 >> 8) | (1 << 24);
+
+
+poly1305_donna_mul:
+ t[0] = mul32x32_64(h0,r0) + mul32x32_64(h1,s4) + mul32x32_64(h2,s3) + mul32x32_64(h3,s2) + mul32x32_64(h4,s1);
+ t[1] = mul32x32_64(h0,r1) + mul32x32_64(h1,r0) + mul32x32_64(h2,s4) + mul32x32_64(h3,s3) + mul32x32_64(h4,s2);
+ t[2] = mul32x32_64(h0,r2) + mul32x32_64(h1,r1) + mul32x32_64(h2,r0) + mul32x32_64(h3,s4) + mul32x32_64(h4,s3);
+ t[3] = mul32x32_64(h0,r3) + mul32x32_64(h1,r2) + mul32x32_64(h2,r1) + mul32x32_64(h3,r0) + mul32x32_64(h4,s4);
+ t[4] = mul32x32_64(h0,r4) + mul32x32_64(h1,r3) + mul32x32_64(h2,r2) + mul32x32_64(h3,r1) + mul32x32_64(h4,r0);
+
+ h0 = (uint32_t)t[0] & 0x3ffffff; c = (t[0] >> 26);
+ t[1] += c; h1 = (uint32_t)t[1] & 0x3ffffff; b = (uint32_t)(t[1] >> 26);
+ t[2] += b; h2 = (uint32_t)t[2] & 0x3ffffff; b = (uint32_t)(t[2] >> 26);
+ t[3] += b; h3 = (uint32_t)t[3] & 0x3ffffff; b = (uint32_t)(t[3] >> 26);
+ t[4] += b; h4 = (uint32_t)t[4] & 0x3ffffff; b = (uint32_t)(t[4] >> 26);
+ h0 += b * 5;
+
+ if (inlen >= 16) goto poly1305_donna_16bytes;
+
+ /* final bytes */
+poly1305_donna_atmost15bytes:
+ if (!inlen) goto poly1305_donna_finish;
+
+ for (j = 0; j < inlen; j++) mp[j] = m[j];
+ mp[j++] = 1;
+ for (; j < 16; j++) mp[j] = 0;
+ inlen = 0;
+
+ t0 = U8TO32_LE(mp+0);
+ t1 = U8TO32_LE(mp+4);
+ t2 = U8TO32_LE(mp+8);
+ t3 = U8TO32_LE(mp+12);
+
+ h0 += t0 & 0x3ffffff;
+ h1 += ((((uint64_t)t1 << 32) | t0) >> 26) & 0x3ffffff;
+ h2 += ((((uint64_t)t2 << 32) | t1) >> 20) & 0x3ffffff;
+ h3 += ((((uint64_t)t3 << 32) | t2) >> 14) & 0x3ffffff;
+ h4 += (t3 >> 8);
+
+ goto poly1305_donna_mul;
+
+poly1305_donna_finish:
+ b = h0 >> 26; h0 = h0 & 0x3ffffff;
+ h1 += b; b = h1 >> 26; h1 = h1 & 0x3ffffff;
+ h2 += b; b = h2 >> 26; h2 = h2 & 0x3ffffff;
+ h3 += b; b = h3 >> 26; h3 = h3 & 0x3ffffff;
+ h4 += b; b = h4 >> 26; h4 = h4 & 0x3ffffff;
+ h0 += b * 5; b = h0 >> 26; h0 = h0 & 0x3ffffff;
+ h1 += b;
+
+ g0 = h0 + 5; b = g0 >> 26; g0 &= 0x3ffffff;
+ g1 = h1 + b; b = g1 >> 26; g1 &= 0x3ffffff;
+ g2 = h2 + b; b = g2 >> 26; g2 &= 0x3ffffff;
+ g3 = h3 + b; b = g3 >> 26; g3 &= 0x3ffffff;
+ g4 = h4 + b - (1 << 26);
+
+ b = (g4 >> 31) - 1;
+ nb = ~b;
+ h0 = (h0 & nb) | (g0 & b);
+ h1 = (h1 & nb) | (g1 & b);
+ h2 = (h2 & nb) | (g2 & b);
+ h3 = (h3 & nb) | (g3 & b);
+ h4 = (h4 & nb) | (g4 & b);
+
+ f0 = ((h0 ) | (h1 << 26)) + (uint64_t)U8TO32_LE(&key[16]);
+ f1 = ((h1 >> 6) | (h2 << 20)) + (uint64_t)U8TO32_LE(&key[20]);
+ f2 = ((h2 >> 12) | (h3 << 14)) + (uint64_t)U8TO32_LE(&key[24]);
+ f3 = ((h3 >> 18) | (h4 << 8)) + (uint64_t)U8TO32_LE(&key[28]);
+
+ U32TO8_LE(&out[ 0], f0); f1 += (f0 >> 32);
+ U32TO8_LE(&out[ 4], f1); f2 += (f1 >> 32);
+ U32TO8_LE(&out[ 8], f2); f3 += (f2 >> 32);
+ U32TO8_LE(&out[12], f3);
+}
Index: poly1305-donna-unrolled.h
===================================================================
RCS file: poly1305-donna-unrolled.h
diff -N poly1305-donna-unrolled.h
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ poly1305-donna-unrolled.h 14 Nov 2013 02:10:30 -0000
@@ -0,0 +1,22 @@
+/* $OpenBSD$ */
+
+/*
+ * Public Domain poly1305-donna from Andrew M.
+ * https://github.com/floodyberry/poly1305-donna
+ */
+
+#ifndef POLY1305_H
+#define POLY1305_H
+
+#include <sys/types.h>
+
+#define POLY1305_KEYLEN 32
+#define POLY1305_TAGLEN 16
+
+void poly1305_auth(u_char out[POLY1305_TAGLEN], const u_char *m, size_t inlen,
+ const u_char key[POLY1305_KEYLEN])
+ __attribute__((__bounded__(__minbytes__, 1, POLY1305_TAGLEN)))
+ __attribute__((__bounded__(__buffer__, 2, 3)))
+ __attribute__((__bounded__(__minbytes__, 4, POLY1305_KEYLEN)));
+
+#endif /* POLY1305_H */
Index: lib/Makefile
===================================================================
RCS file: /cvs/src/usr.bin/ssh/lib/Makefile,v
retrieving revision 1.68
diff -u -p -r1.68 Makefile
--- lib/Makefile 2 Nov 2013 21:59:15 -0000 1.68
+++ lib/Makefile 14 Nov 2013 02:10:30 -0000
@@ -13,7 +13,8 @@ SRCS= authfd.c authfile.c bufaux.c bufec
ssh-dss.c ssh-rsa.c ssh-ecdsa.c dh.c kexdh.c kexgex.c kexecdh.c \
kexdhc.c kexgexc.c kexecdhc.c msg.c progressmeter.c dns.c \
monitor_fdpass.c umac.c addrmatch.c schnorr.c jpake.c ssh-pkcs11.c \
- krl.c smult_curve25519_ref.c kexc25519.c kexc25519c.c
+ krl.c smult_curve25519_ref.c kexc25519.c kexc25519c.c \
+ chacha.c poly1305-donna-unrolled.c chacha20poly1305aead.c
SRCS+= umac128.c
CLEANFILES+= umac128.c
More information about the openssh-unix-dev
mailing list