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[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@
This commit is contained in:
Damien Miller 2006-03-26 00:11:46 +11:00
parent a1b3d636ab
commit 2dbbf8e9fc
3 changed files with 15 additions and 30 deletions
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8
ChangeLog
View File

@ -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 $

33
deattack.c
View File

@ -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;

4
deattack.h
View File

@ -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