Add the CRC32 compensation attack detector that all other SSH

clients have had for ages and I forgot about. Of course I've got the
version with the buffer overflow fixed!

git-svn-id: svn://svn.tartarus.org/sgt/putty@1535 cda61777-01e9-0310-a592-d414129be87e

diff --git a/LICENCE b/LICENCE
index 28cccff..f1c9416 100644 (file)
--- a/LICENCE
+++ b/LICENCE
@@ -1,7 +1,8 @@
 PuTTY is copyright 1997-2001 Simon Tatham.
 
 Portions copyright Robert de Bath, Joris van Rantwijk, Delian
-Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry.
+Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry,
+and CORE SDI S.A.
 
 Permission is hereby granted, free of charge, to any person
 obtaining a copy of this software and associated documentation files

diff --git a/Makefile b/Makefile
index b69762a..6ae9268 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -115,9 +115,9 @@ MOBJ2 = tree234.$(OBJ)
 COBJS = console.$(OBJ)
 ##-- objects putty pscp psftp plink
 OBJS1 = sshcrc.$(OBJ) sshdes.$(OBJ) sshmd5.$(OBJ) sshrsa.$(OBJ) sshrand.$(OBJ)
-OBJS2 = sshsha.$(OBJ) sshblowf.$(OBJ) noise.$(OBJ) sshdh.$(OBJ) sshdss.$(OBJ)
-OBJS3 = sshbn.$(OBJ) sshpubk.$(OBJ) ssh.$(OBJ) pageantc.$(OBJ) sshzlib.$(OBJ)
-OBJS4 = x11fwd.$(OBJ) portfwd.$(OBJ) sshaes.$(OBJ) sshsh512.$(OBJ)
+OBJS2 = sshsha.$(OBJ) sshblowf.$(OBJ) noise.$(OBJ) sshdh.$(OBJ) sshcrcda.$(OBJ)
+OBJS3 = sshpubk.$(OBJ) ssh.$(OBJ) pageantc.$(OBJ) sshzlib.$(OBJ) sshdss.$(OBJ)
+OBJS4 = x11fwd.$(OBJ) portfwd.$(OBJ) sshaes.$(OBJ) sshsh512.$(OBJ) sshbn.$(OBJ)
 ##-- objects pageant
 PAGE1 = pageant.$(OBJ) sshrsa.$(OBJ) sshpubk.$(OBJ) sshdes.$(OBJ) sshbn.$(OBJ)
 PAGE2 = sshmd5.$(OBJ) version.$(OBJ) tree234.$(OBJ) misc.$(OBJ) sshaes.$(OBJ)

diff --git a/doc/licence.but b/doc/licence.but
index 28994f6..f47d5dc 100644 (file)
--- a/doc/licence.but
+++ b/doc/licence.but
@@ -1,11 +1,12 @@
-\versionid $Id: licence.but,v 1.1 2001/12/16 14:56:02 simon Exp $
+\versionid $Id: licence.but,v 1.2 2002/01/08 11:57:32 simon Exp $
 
 \A{licence} PuTTY Licence
 
 PuTTY is copyright 1997-2001 Simon Tatham.
 
 Portions copyright Robert de Bath, Joris van Rantwijk, Delian
-Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry.
+Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry,
+and CORE SDI S.A.
 
 Permission is hereby granted, free of charge, to any person
 obtaining a copy of this software and associated documentation files

diff --git a/pageant.rc b/pageant.rc
index 299995a..2847e20 100644 (file)
--- a/pageant.rc
+++ b/pageant.rc
@@ -66,7 +66,7 @@ BEGIN
 
     LTEXT "Portions copyright Robert de Bath, Joris van Rantwijk, Delian", 1001, 10, 26, 206, 8
     LTEXT "Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas", 1002, 10, 34, 206, 8
-    LTEXT "Barry.", 1003, 10, 42, 206, 8
+    LTEXT "Barry, and CORE SDI S.A.", 1003, 10, 42, 206, 8
 
     LTEXT "Permission is hereby granted, free of charge, to any person", 1004, 10, 58, 206, 8
     LTEXT "obtaining a copy of this software and associated documentation", 1005, 10, 66, 206, 8

diff --git a/puttygen.rc b/puttygen.rc
index b7711c3..7d1ff22 100644 (file)
--- a/puttygen.rc
+++ b/puttygen.rc
@@ -59,7 +59,7 @@ BEGIN
 
     LTEXT "Portions copyright Robert de Bath, Joris van Rantwijk, Delian", 1001, 10, 26, 206, 8
     LTEXT "Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas", 1002, 10, 34, 206, 8
-    LTEXT "Barry.", 1003, 10, 42, 206, 8
+    LTEXT "Barry, and CORE SDI S.A.", 1003, 10, 42, 206, 8
 
     LTEXT "Permission is hereby granted, free of charge, to any person", 1004, 10, 58, 206, 8
     LTEXT "obtaining a copy of this software and associated documentation", 1005, 10, 66, 206, 8

diff --git a/ssh.c b/ssh.c
index 115c0ce..b8abc5b 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -724,6 +724,11 @@ static int ssh1_rdpkt(unsigned char **data, int *datalen)
        st->to_read -= st->chunk;
     }
 
+    if (cipher && detect_attack(pktin.data, st->biglen, NULL)) {
+        bombout(("Network attack (CRC compensation) detected!"));
+        crReturn(0);
+    }
+
     if (cipher)
        cipher->decrypt(pktin.data, st->biglen);
 

diff --git a/ssh.h b/ssh.h
index 3981066..7857f15 100644 (file)
--- a/ssh.h
+++ b/ssh.h
@@ -72,6 +72,10 @@ typedef unsigned int word32;
 typedef unsigned int uint32;
 
 unsigned long crc32(const void *s, size_t len);
+unsigned long crc32_update(unsigned long crc_input, const void *s, size_t len);
+
+/* SSH CRC compensation attack detector */
+int detect_attack(unsigned char *buf, uint32 len, unsigned char *IV);
 
 typedef struct {
     uint32 h[4];

diff --git a/sshcrc.c b/sshcrc.c
index fb0db0c..691f7b4 100644 (file)
--- a/sshcrc.c
+++ b/sshcrc.c
@@ -211,9 +211,8 @@ int main(void)
 }
 #endif
 
-unsigned long crc32(const void *buf, size_t len)
+unsigned long crc32_update(unsigned long crcword, const void *buf, size_t len)
 {
-    unsigned long crcword = 0L;
     const unsigned char *p = (const unsigned char *) buf;
     while (len--) {
        unsigned long newbyte = *p++;
@@ -222,3 +221,8 @@ unsigned long crc32(const void *buf, size_t len)
     }
     return crcword;
 }
+
+unsigned long crc32(const void *buf, size_t len)
+{
+    return crc32_update(0L, buf, len);
+}

diff --git a/sshcrcda.c b/sshcrcda.c
new file mode 100644 (file)
index 0000000..7b683be
--- /dev/null
+++ b/sshcrcda.c
@@ -0,0 +1,157 @@
+/*     $OpenBSD: deattack.c,v 1.14 2001/06/23 15:12:18 itojun 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>
+ * 
+ * Modified for use in PuTTY by Simon Tatham
+ */
+
+#include <assert.h>
+#include "misc.h"
+#include "ssh.h"
+
+typedef unsigned char uchar;
+typedef unsigned short uint16;
+
+/* SSH Constants */
+#define SSH_MAXBLOCKS  (32 * 1024)
+#define SSH_BLOCKSIZE  (8)
+
+/* Hashing constants */
+#define HASH_MINSIZE   (8 * 1024)
+#define HASH_ENTRYSIZE (sizeof(uint16))
+#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)
+
+#define GET_32BIT_MSB_FIRST(cp) \
+  (((unsigned long)(unsigned char)(cp)[0] << 24) | \
+  ((unsigned long)(unsigned char)(cp)[1] << 16) | \
+  ((unsigned long)(unsigned char)(cp)[2] << 8) | \
+  ((unsigned long)(unsigned char)(cp)[3]))
+
+/* Hash function (Input keys are cipher results) */
+#define HASH(x)                GET_32BIT_MSB_FIRST(x)
+
+#define CMP(a, b)      (memcmp(a, b, SSH_BLOCKSIZE))
+
+uchar ONE[4] = { 1, 0, 0, 0 };
+uchar ZERO[4] = { 0, 0, 0, 0 };
+
+static void crc_update(uint32 *a, void *b)
+{
+    *a = crc32_update(*a, b, 4);
+}
+
+/* detect if a block is used in a particular pattern */
+static int check_crc(uchar *S, uchar *buf, uint32 len, uchar *IV)
+{
+    uint32 crc;
+    uchar *c;
+
+    crc = 0;
+    if (IV && !CMP(S, IV)) {
+        crc_update(&crc, ONE);
+        crc_update(&crc, ZERO);
+    }
+    for (c = buf; c < buf + len; c += SSH_BLOCKSIZE) {
+        if (!CMP(S, c)) {
+            crc_update(&crc, ONE);
+            crc_update(&crc, ZERO);
+        } else {
+            crc_update(&crc, ZERO);
+            crc_update(&crc, ZERO);
+        }
+    }
+    return (crc == 0);
+}
+
+/* Detect a crc32 compensation attack on a packet */
+int detect_attack(uchar *buf, uint32 len, uchar *IV)
+{
+    static uint16 *h = (uint16 *) NULL;
+    static uint32 n = HASH_MINSIZE / HASH_ENTRYSIZE;
+    register uint32 i, j;
+    uint32 l;
+    register uchar *c;
+    uchar *d;
+
+    assert(!(len > (SSH_MAXBLOCKS * SSH_BLOCKSIZE) ||
+             len % SSH_BLOCKSIZE != 0));
+    for (l = n; l < HASH_FACTOR(len / SSH_BLOCKSIZE); l = l << 2)
+        ;
+
+    if (h == NULL) {
+        logevent("Installing CRC compensation attack detector");
+        n = l;
+        h = (uint16 *) smalloc(n * HASH_ENTRYSIZE);
+    } else {
+        if (l > n) {
+            n = l;
+            h = (uint16 *) srealloc(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 1;          /* attack detected */
+                else
+                    break;
+            }
+            for (d = buf; d < c; d += SSH_BLOCKSIZE) {
+                if (!CMP(c, d)) {
+                    if ((check_crc(c, buf, len, IV)))
+                        return 1;      /* attack detected */
+                    else
+                        break;
+                }
+            }
+        }
+        return 0;                      /* ok */
+    }
+    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 1;      /* attack detected */
+                    else
+                        break;
+                }
+            } else if (!CMP(c, buf + h[i] * SSH_BLOCKSIZE)) {
+                if (check_crc(c, buf, len, IV))
+                    return 1;          /* attack detected */
+                else
+                    break;
+            }
+        }
+        h[i] = j;
+    }
+    return 0;                          /* ok */
+}

diff --git a/win_res.rc b/win_res.rc
index d2d81d1..c35bc8e 100644 (file)
--- a/win_res.rc
+++ b/win_res.rc
@@ -87,7 +87,7 @@ BEGIN
 
     LTEXT "Portions copyright Robert de Bath, Joris van Rantwijk, Delian", 1001, 10, 26, 206, 8
     LTEXT "Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas", 1002, 10, 34, 206, 8
-    LTEXT "Barry.", 1003, 10, 42, 206, 8
+    LTEXT "Barry, and CORE SDI S.A.", 1003, 10, 42, 206, 8
 
     LTEXT "Permission is hereby granted, free of charge, to any person", 1004, 10, 58, 206, 8
     LTEXT "obtaining a copy of this software and associated documentation", 1005, 10, 66, 206, 8