/*
- * $OpenBSD: deattack.c,v 1.7 2000/06/20 01:39:41 markus Exp $
* Cryptographic attack detector for ssh - source code
*
* Copyright (c) 1998 CORE SDI S.A., Buenos Aires, Argentina.
*/
#include "includes.h"
+
#include "deattack.h"
-#include "ssh.h"
+#include "log.h"
#include "crc32.h"
#include "getput.h"
#include "xmalloc.h"
#define HASH_FACTOR(x) ((x)*3/2)
#define HASH_UNUSEDCHAR (0xff)
#define HASH_UNUSED (0xffff)
-#define HASH_IV (0xfffe)
+#define HASH_IV (0xfffe)
#define HASH_MINBLOCKS (7*SSH_BLOCKSIZE)
/* Hash function (Input keys are cipher results) */
#define HASH(x) GET_32BIT(x)
-#define CMP(a,b) (memcmp(a, b, SSH_BLOCKSIZE))
-
+#define CMP(a, b) (memcmp(a, b, SSH_BLOCKSIZE))
-void
+static void
crc_update(u_int32_t *a, u_int32_t b)
{
b ^= *a;
- *a = crc32((unsigned char *) &b, sizeof(b));
+ *a = ssh_crc32((u_char *)&b, sizeof(b));
}
/* detect if a block is used in a particular pattern */
-int
-check_crc(unsigned char *S, unsigned char *buf, u_int32_t len,
- unsigned char *IV)
+static int
+check_crc(u_char *S, u_char *buf, u_int32_t len)
{
u_int32_t crc;
- unsigned char *c;
+ 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);
/* Detect a crc32 compensation attack on a packet */
int
-detect_attack(unsigned char *buf, u_int32_t len, unsigned char *IV)
+detect_attack(u_char *buf, u_int32_t len)
{
static u_int16_t *h = (u_int16_t *) NULL;
- static u_int16_t n = HASH_MINSIZE / HASH_ENTRYSIZE;
- register u_int32_t i, j;
+ static u_int32_t n = HASH_MINSIZE / HASH_ENTRYSIZE;
+ u_int32_t i, j;
u_int32_t l;
- register unsigned char *c;
- unsigned char *d;
+ u_char *c;
+ u_char *d;
if (len > (SSH_MAXBLOCKS * SSH_BLOCKSIZE) ||
len % SSH_BLOCKSIZE != 0) {
if (h == NULL) {
debug("Installing crc compensation attack detector.");
+ h = (u_int16_t *) xmalloc(l * HASH_ENTRYSIZE);
n = l;
- h = (u_int16_t *) xmalloc(n * HASH_ENTRYSIZE);
} else {
if (l > n) {
+ h = (u_int16_t *) xrealloc(h, l * HASH_ENTRYSIZE);
n = l;
- h = (u_int16_t *) xrealloc(h, n * HASH_ENTRYSIZE);
}
}
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;
}
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))
+ i = (i + 1) & (n - 1)) {
+ if (!CMP(c, buf + h[i] * SSH_BLOCKSIZE)) {
+ if (check_crc(c, buf, len))
return (DEATTACK_DETECTED);
else
break;