upstream commit

remove the (in)famous SSHv1 CRC compensation attack
detector.

Despite your cameo in The Matrix movies, you will not be missed.

ok markus

Upstream-ID: 44261fce51a56d93cdb2af7b6e184be629f667e0

5 files changed, 3 insertions, 232 deletions

diff --git a/LICENCE b/LICENCE
index f5238713..15248212 100644
--- a/LICENCE
+++ b/LICENCE
@@ -75,27 +75,6 @@ OpenSSH contains no GPL code.
     PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGES.
 
-2)
-    The 32-bit CRC compensation attack detector in deattack.c was
-    contributed by CORE SDI S.A. under a BSD-style license.
-
-     * Cryptographic attack detector for ssh - source code
-     *
-     * Copyright (c) 1998 CORE SDI S.A., Buenos Aires, Argentina.
-     *
-     * All rights reserved. Redistribution and use in source and binary
-     * forms, with or without modification, are permitted provided that
-     * this copyright notice is retained.
-     *
-     * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
-     * WARRANTIES ARE DISCLAIMED. IN NO EVENT SHALL CORE SDI S.A. BE
-     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY OR
-     * CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OR MISUSE OF THIS
-     * SOFTWARE.
-     *
-     * Ariel Futoransky <futo@core-sdi.com>
-     * <http://www.core-sdi.com>
-
 3)
     ssh-keyscan was contributed by David Mazieres under a BSD-style
     license.
@@ -337,4 +316,4 @@ OpenSSH contains no GPL code.
 
 
 ------
-$OpenBSD: LICENCE,v 1.19 2004/08/30 09:18:08 markus Exp $
+$OpenBSD: LICENCE,v 1.20 2017/04/30 23:26:16 djm Exp $
diff --git a/Makefile.in b/Makefile.in
index a7a6239c..d7f17df8 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -79,7 +79,7 @@ LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
 	authfd.o authfile.o bufaux.o bufbn.o bufec.o buffer.o \
 	canohost.o channels.o cipher.o cipher-aes.o cipher-aesctr.o \
 	cipher-ctr.o cleanup.o \
-	compat.o crc32.o deattack.o fatal.o hostfile.o \
+	compat.o crc32.o fatal.o hostfile.o \
 	log.o match.o moduli.o nchan.o packet.o opacket.o \
 	readpass.o rsa.o ttymodes.o xmalloc.o addrmatch.o \
 	atomicio.o key.o dispatch.o mac.o uidswap.o uuencode.o misc.o utf8.o \
diff --git a/deattack.c b/deattack.c
deleted file mode 100644
index e76481a6..00000000
--- a/deattack.c
+++ /dev/null
@@ -1,165 +0,0 @@
-/* $OpenBSD: deattack.c,v 1.32 2015/01/20 23:14:00 deraadt Exp $ */
-/*
- * Cryptographic attack detector for ssh - source code
- *
- * Copyright (c) 1998 CORE SDI S.A., Buenos Aires, Argentina.
- *
- * All rights reserved. Redistribution and use in source and binary
- * forms, with or without modification, are permitted provided that
- * this copyright notice is retained.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
- * WARRANTIES ARE DISCLAIMED. IN NO EVENT SHALL CORE SDI S.A. BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY OR
- * CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OR MISUSE OF THIS
- * SOFTWARE.
- *
- * Ariel Futoransky <futo@core-sdi.com>
- * <http://www.core-sdi.com>
- */
-
-#include "includes.h"
-
-#include <string.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-#include "deattack.h"
-#include "crc32.h"
-#include "sshbuf.h"
-#include "misc.h"
-
-/*
- * CRC attack detection has a worst-case behaviour that is O(N^3) over
- * the number of identical blocks in a packet. This behaviour can be 
- * exploited to create a limited denial of service attack. 
- * 
- * However, because we are dealing with encrypted data, identical
- * blocks should only occur every 2^35 maximally-sized packets or so. 
- * Consequently, we can detect this DoS by looking for identical blocks
- * in a packet.
- *
- * The parameter below determines how many identical blocks we will
- * accept in a single packet, trading off between attack detection and
- * likelihood of terminating a legitimate connection. A value of 32 
- * corresponds to an average of 2^40 messages before an attack is
- * misdetected
- */
-#define MAX_IDENTICAL	32
-
-/* SSH Constants */
-#define SSH_MAXBLOCKS	(32 * 1024)
-#define SSH_BLOCKSIZE	(8)
-
-/* Hashing constants */
-#define HASH_MINSIZE	(8 * 1024)
-#define HASH_ENTRYSIZE	(2)
-#define HASH_FACTOR(x)	((x)*3/2)
-#define HASH_UNUSEDCHAR	(0xff)
-#define HASH_UNUSED	(0xffff)
-#define HASH_IV		(0xfffe)
-
-#define HASH_MINBLOCKS	(7*SSH_BLOCKSIZE)
-
-
-/* Hash function (Input keys are cipher results) */
-#define HASH(x)		PEEK_U32(x)
-
-#define CMP(a, b)	(memcmp(a, b, SSH_BLOCKSIZE))
-
-static void
-crc_update(u_int32_t *a, u_int32_t b)
-{
-	b ^= *a;
-	*a = ssh_crc32((u_char *)&b, sizeof(b));
-}
-
-/* detect if a block is used in a particular pattern */
-static int
-check_crc(const u_char *S, const u_char *buf, u_int32_t len)
-{
-	u_int32_t crc;
-	const u_char *c;
-
-	crc = 0;
-	for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) {
-		if (!CMP(S, c)) {
-			crc_update(&crc, 1);
-			crc_update(&crc, 0);
-		} else {
-			crc_update(&crc, 0);
-			crc_update(&crc, 0);
-		}
-	}
-	return crc == 0;
-}
-
-void
-deattack_init(struct deattack_ctx *dctx)
-{
-	bzero(dctx, sizeof(*dctx));
-	dctx->n = HASH_MINSIZE / HASH_ENTRYSIZE;
-}
-
-/* Detect a crc32 compensation attack on a packet */
-int
-detect_attack(struct deattack_ctx *dctx, const u_char *buf, u_int32_t len)
-{
-	u_int32_t i, j, l, same;
-	u_int16_t *tmp;
-	const u_char *c, *d;
-
-	if (len > (SSH_MAXBLOCKS * SSH_BLOCKSIZE) ||
-	    len % SSH_BLOCKSIZE != 0)
-		return DEATTACK_ERROR;
-	for (l = dctx->n; l < HASH_FACTOR(len / SSH_BLOCKSIZE); l = l << 2)
-		;
-
-	if (dctx->h == NULL) {
-		if ((dctx->h = calloc(l, HASH_ENTRYSIZE)) == NULL)
-			return DEATTACK_ERROR;
-		dctx->n = l;
-	} else {
-		if (l > dctx->n) {
-			if ((tmp = reallocarray(dctx->h, l, HASH_ENTRYSIZE))
-			    == NULL) {
-				free(dctx->h);
-				dctx->h = NULL;
-				return DEATTACK_ERROR;
-			}
-			dctx->h = tmp;
-			dctx->n = l;
-		}
-	}
-
-	if (len <= HASH_MINBLOCKS) {
-		for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) {
-			for (d = buf; d < c; d += SSH_BLOCKSIZE) {
-				if (!CMP(c, d)) {
-					if ((check_crc(c, buf, len)))
-						return DEATTACK_DETECTED;
-					else
-						break;
-				}
-			}
-		}
-		return DEATTACK_OK;
-	}
-	memset(dctx->h, HASH_UNUSEDCHAR, dctx->n * HASH_ENTRYSIZE);
-
-	for (c = buf, same = j = 0; c < (buf + len); c += SSH_BLOCKSIZE, j++) {
-		for (i = HASH(c) & (dctx->n - 1); dctx->h[i] != HASH_UNUSED;
-		    i = (i + 1) & (dctx->n - 1)) {
-			if (!CMP(c, buf + dctx->h[i] * SSH_BLOCKSIZE)) {
-				if (++same > MAX_IDENTICAL)
-					return DEATTACK_DOS_DETECTED;
-				if (check_crc(c, buf, len))
-					return DEATTACK_DETECTED;
-				else
-					break;
-			}
-		}
-		dctx->h[i] = j;
-	}
-	return DEATTACK_OK;
-}
diff --git a/deattack.h b/deattack.h
deleted file mode 100644
index ce67a30f..00000000
--- a/deattack.h
+++ /dev/null
@@ -1,38 +0,0 @@
-/* $OpenBSD: deattack.h,v 1.11 2015/01/19 19:52:16 markus Exp $ */
-
-/*
- * Cryptographic attack detector for ssh - Header file
- *
- * Copyright (c) 1998 CORE SDI S.A., Buenos Aires, Argentina.
- *
- * All rights reserved. Redistribution and use in source and binary
- * forms, with or without modification, are permitted provided that
- * this copyright notice is retained.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
- * WARRANTIES ARE DISCLAIMED. IN NO EVENT SHALL CORE SDI S.A. BE
- * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY OR
- * CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OR MISUSE OF THIS
- * SOFTWARE.
- *
- * Ariel Futoransky <futo@core-sdi.com>
- * <http://www.core-sdi.com>
- */
-
-#ifndef _DEATTACK_H
-#define _DEATTACK_H
-
-/* Return codes */
-#define DEATTACK_OK		0
-#define DEATTACK_DETECTED	1
-#define DEATTACK_DOS_DETECTED	2
-#define DEATTACK_ERROR		3
-
-struct deattack_ctx {
-	u_int16_t *h;
-	u_int32_t n;
-};
-
-void	 deattack_init(struct deattack_ctx *);
-int	 detect_attack(struct deattack_ctx *, const u_char *, u_int32_t);
-#endif
diff --git a/packet.c b/packet.c
index 6cec9337..0e312c51 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.250 2017/04/30 23:23:54 djm Exp $ */
+/* $OpenBSD: packet.c,v 1.251 2017/04/30 23:26:16 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -68,7 +68,6 @@
 
 #include "xmalloc.h"
 #include "crc32.h"
-#include "deattack.h"
 #include "compat.h"
 #include "ssh1.h"
 #include "ssh2.h"
@@ -216,9 +215,6 @@ struct session_state {
 	/* One-off warning about weak ciphers */
 	int cipher_warning_done;
 
-	/* SSH1 CRC compensation attack detector */
-	struct deattack_ctx deattack;
-
 	/* Hook for fuzzing inbound packets */
 	ssh_packet_hook_fn *hook_in;
 	void *hook_in_ctx;
@@ -315,7 +311,6 @@ ssh_packet_set_connection(struct ssh *ssh, int fd_in, int fd_out)
 		return NULL;
 	}
 	state->newkeys[MODE_IN] = state->newkeys[MODE_OUT] = NULL;
-	deattack_init(&state->deattack);
 	/*
 	 * Cache the IP address of the remote connection for use in error
 	 * messages that might be generated after the connection has closed.