From 2dbbf8e9fc058cab975a9bcda21465d34465c92e Mon Sep 17 00:00:00 2001
From: Damien Miller <djm@mindrot.org>
Date: Sun, 26 Mar 2006 00:11:46 +1100
Subject: [PATCH]      [deattack.c deattack.h]      remove IV support from the
 CRC attack detector, OpenSSH has never used      it - it only applied to
 IDEA-CFB, which we don't support.      prompted by NetBSD Coverity report via
 elad AT netbsd.org;      feedback markus@ "nuke it" deraadt@

---
 ChangeLog  |  8 +++++++-
 deattack.c | 33 ++++++---------------------------
 deattack.h |  4 ++--
 3 files changed, 15 insertions(+), 30 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index b3298fe0a..3bc8c4bd3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -56,6 +56,12 @@
    - jakob@cvs.openbsd.org 2006/03/22 21:16:24
      [ssh.1]
      simplify SSHFP example; ok jmc@
+   - djm@cvs.openbsd.org 2006/03/22 21:27:15
+     [deattack.c deattack.h]
+     remove IV support from the CRC attack detector, OpenSSH has never used
+     it - it only applied to IDEA-CFB, which we don't support.
+     prompted by NetBSD Coverity report via elad AT netbsd.org;
+     feedback markus@ "nuke it" deraadt@
 
 20060318
  - (djm) [auth-pam.c] Fix memleak in error path, from Coverity via
@@ -4248,4 +4254,4 @@
    - (djm) Trim deprecated options from INSTALL. Mention UsePAM
    - (djm) Fix quote handling in sftp; Patch from admorten AT umich.edu
 
-$Id: ChangeLog,v 1.4240 2006/03/25 13:07:02 djm Exp $
+$Id: ChangeLog,v 1.4241 2006/03/25 13:11:46 djm Exp $
diff --git a/deattack.c b/deattack.c
index 3d48afc89..bf4451b88 100644
--- a/deattack.c
+++ b/deattack.c
@@ -49,22 +49,17 @@ static void
 crc_update(u_int32_t *a, u_int32_t b)
 {
 	b ^= *a;
-	*a = ssh_crc32((u_char *) &b, sizeof(b));
+	*a = ssh_crc32((u_char *)&b, sizeof(b));
 }
 
 /* detect if a block is used in a particular pattern */
 static int
-check_crc(u_char *S, u_char *buf, u_int32_t len,
-	  u_char *IV)
+check_crc(u_char *S, u_char *buf, u_int32_t len)
 {
 	u_int32_t crc;
 	u_char *c;
 
 	crc = 0;
-	if (IV && !CMP(S, IV)) {
-		crc_update(&crc, 1);
-		crc_update(&crc, 0);
-	}
 	for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) {
 		if (!CMP(S, c)) {
 			crc_update(&crc, 1);
@@ -80,7 +75,7 @@ check_crc(u_char *S, u_char *buf, u_int32_t len,
 
 /* Detect a crc32 compensation attack on a packet */
 int
-detect_attack(u_char *buf, u_int32_t len, u_char *IV)
+detect_attack(u_char *buf, u_int32_t len)
 {
 	static u_int16_t *h = (u_int16_t *) NULL;
 	static u_int32_t n = HASH_MINSIZE / HASH_ENTRYSIZE;
@@ -109,15 +104,9 @@ detect_attack(u_char *buf, u_int32_t len, u_char *IV)
 
 	if (len <= HASH_MINBLOCKS) {
 		for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) {
-			if (IV && (!CMP(c, IV))) {
-				if ((check_crc(c, buf, len, IV)))
-					return (DEATTACK_DETECTED);
-				else
-					break;
-			}
 			for (d = buf; d < c; d += SSH_BLOCKSIZE) {
 				if (!CMP(c, d)) {
-					if ((check_crc(c, buf, len, IV)))
+					if ((check_crc(c, buf, len)))
 						return (DEATTACK_DETECTED);
 					else
 						break;
@@ -128,21 +117,11 @@ detect_attack(u_char *buf, u_int32_t len, u_char *IV)
 	}
 	memset(h, HASH_UNUSEDCHAR, n * HASH_ENTRYSIZE);
 
-	if (IV)
-		h[HASH(IV) & (n - 1)] = HASH_IV;
-
 	for (c = buf, j = 0; c < (buf + len); c += SSH_BLOCKSIZE, j++) {
 		for (i = HASH(c) & (n - 1); h[i] != HASH_UNUSED;
 		    i = (i + 1) & (n - 1)) {
-			if (h[i] == HASH_IV) {
-				if (!CMP(c, IV)) {
-					if (check_crc(c, buf, len, IV))
-						return (DEATTACK_DETECTED);
-					else
-						break;
-				}
-			} else if (!CMP(c, buf + h[i] * SSH_BLOCKSIZE)) {
-				if (check_crc(c, buf, len, IV))
+			if (!CMP(c, buf + h[i] * SSH_BLOCKSIZE)) {
+				if (check_crc(c, buf, len))
 					return (DEATTACK_DETECTED);
 				else
 					break;
diff --git a/deattack.h b/deattack.h
index ddccdea50..7bb6100d0 100644
--- a/deattack.h
+++ b/deattack.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: deattack.h,v 1.7 2001/06/26 17:27:23 markus Exp $	*/
+/*	$OpenBSD: deattack.h,v 1.8 2006/03/22 21:27:15 djm Exp $	*/
 
 /*
  * Cryptographic attack detector for ssh - Header file
@@ -26,5 +26,5 @@
 #define DEATTACK_OK		0
 #define DEATTACK_DETECTED	1
 
-int	 detect_attack(u_char *, u_int32_t, u_char[8]);
+int	 detect_attack(u_char *, u_int32_t);
 #endif