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openssh-portable
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- (djm) OpenBSD CVS Sync: 

- markus@cvs.openbsd.org  2001/01/29 12:47:32
     [rsa.c rsa.h ssh-agent.c sshconnect1.c sshd.c]
     handle rsa_private_decrypt failures; helps against the Bleichenbacher
     pkcs#1 attack
This commit is contained in:
Damien Miller 2001-01-30 09:27:26 +11:00
parent d83ff35d66
commit 7650bc6842
6 changed files with 63 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
ChangeLog
View File

@ -6,6 +6,10 @@
- markus@cvs.openbsd.org 2001/01/29 12:42:35
[canohost.c canohost.h channels.c clientloop.c]
add get_peer_ipaddr(socket), x11-fwd in ssh2 requires ipaddr, not DNS
- markus@cvs.openbsd.org 2001/01/29 12:47:32
[rsa.c rsa.h ssh-agent.c sshconnect1.c sshd.c]
handle rsa_private_decrypt failures; helps against the Bleichenbacher
pkcs#1 attack
20000129
- (stevesk) sftp-server.c: use %lld vs. %qd

15
rsa.c
View File

@ -60,7 +60,7 @@
*/
#include "includes.h"
RCSID("$OpenBSD: rsa.c,v 1.19 2001/01/21 19:05:54 markus Exp $");
RCSID("$OpenBSD: rsa.c,v 1.20 2001/01/29 19:47:30 markus Exp $");
#include "rsa.h"
#include "log.h"
@ -94,7 +94,7 @@ rsa_public_encrypt(BIGNUM *out, BIGNUM *in, RSA *key)
xfree(inbuf);
}
void
int
rsa_private_decrypt(BIGNUM *out, BIGNUM *in, RSA *key)
{
u_char *inbuf, *outbuf;
@ -108,13 +108,14 @@ rsa_private_decrypt(BIGNUM *out, BIGNUM *in, RSA *key)
BN_bn2bin(in, inbuf);
if ((len = RSA_private_decrypt(ilen, inbuf, outbuf, key,
RSA_PKCS1_PADDING)) <= 0)
fatal("rsa_private_decrypt() failed");
BN_bin2bn(outbuf, len, out);
RSA_PKCS1_PADDING)) <= 0) {
error("rsa_private_decrypt() failed");
} else {
BN_bin2bn(outbuf, len, out);
}
memset(outbuf, 0, olen);
memset(inbuf, 0, ilen);
xfree(outbuf);
xfree(inbuf);
return len;
}

4
rsa.h
View File

@ -11,7 +11,7 @@
* called by a name other than "ssh" or "Secure Shell".
*/
/* RCSID("$OpenBSD: rsa.h,v 1.9 2000/11/12 19:50:38 markus Exp $"); */
/* RCSID("$OpenBSD: rsa.h,v 1.10 2001/01/29 19:47:30 markus Exp $"); */
#ifndef RSA_H
#define RSA_H
@ -20,6 +20,6 @@
#include <openssl/rsa.h>
void rsa_public_encrypt __P((BIGNUM * out, BIGNUM * in, RSA * prv));
void rsa_private_decrypt __P((BIGNUM * out, BIGNUM * in, RSA * prv));
int rsa_private_decrypt __P((BIGNUM * out, BIGNUM * in, RSA * prv));
#endif /* RSA_H */

7
ssh-agent.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: ssh-agent.c,v 1.48 2001/01/25 08:06:33 deraadt Exp $ */
/* $OpenBSD: ssh-agent.c,v 1.49 2001/01/29 19:47:31 markus Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@ -37,7 +37,7 @@
*/
#include "includes.h"
RCSID("$OpenBSD: ssh-agent.c,v 1.48 2001/01/25 08:06:33 deraadt Exp $");
RCSID("$OpenBSD: ssh-agent.c,v 1.49 2001/01/29 19:47:31 markus Exp $");
#include <openssl/evp.h>
#include <openssl/md5.h>
@ -198,7 +198,8 @@ process_authentication_challenge1(SocketEntry *e)
private = lookup_private_key(key, NULL, 1);
if (private != NULL) {
/* Decrypt the challenge using the private key. */
rsa_private_decrypt(challenge, challenge, private->rsa);
if (rsa_private_decrypt(challenge, challenge, private->rsa) <= 0)
goto failure;
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);

11
sshconnect1.c
View File

@ -13,7 +13,7 @@
*/
#include "includes.h"
RCSID("$OpenBSD: sshconnect1.c,v 1.20 2001/01/22 23:06:40 markus Exp $");
RCSID("$OpenBSD: sshconnect1.c,v 1.21 2001/01/29 19:47:31 markus Exp $");
#include <openssl/bn.h>
#include <openssl/evp.h>
@ -163,14 +163,17 @@ respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
int i, len;
/* Decrypt the challenge using the private key. */
rsa_private_decrypt(challenge, challenge, prv);
/* XXX think about Bleichenbacher, too */
if (rsa_private_decrypt(challenge, challenge, prv) <= 0)
packet_disconnect(
"respond_to_rsa_challenge: rsa_private_decrypt failed");
/* Compute the response. */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > sizeof(buf))
packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
len);
packet_disconnect(
"respond_to_rsa_challenge: bad challenge length %d", len);
memset(buf, 0, sizeof(buf));
BN_bn2bin(challenge, buf + sizeof(buf) - len);

57
sshd.c
View File

@ -40,7 +40,7 @@
*/
#include "includes.h"
RCSID("$OpenBSD: sshd.c,v 1.158 2001/01/28 10:37:26 markus Exp $");
RCSID("$OpenBSD: sshd.c,v 1.159 2001/01/29 19:47:31 markus Exp $");
#include <openssl/dh.h>
#include <openssl/bn.h>
@ -1186,6 +1186,7 @@ do_ssh1_kex(void)
{
int i, len;
int plen, slen;
int rsafail = 0;
BIGNUM *session_key_int;
u_char session_key[SSH_SESSION_KEY_LENGTH];
u_char cookie[8];
@ -1296,7 +1297,7 @@ do_ssh1_kex(void)
* with larger modulus first).
*/
if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
/* Private key has bigger modulus. */
/* Server key has bigger modulus. */
if (BN_num_bits(sensitive_data.server_key->rsa->n) <
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
@ -1305,10 +1306,12 @@ do_ssh1_kex(void)
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa);
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa);
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa) <= 0)
rsafail++;
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa) <= 0)
rsafail++;
} else {
/* Host key has bigger modulus (or they are equal). */
if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
@ -1319,10 +1322,12 @@ do_ssh1_kex(void)
BN_num_bits(sensitive_data.server_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa);
rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa);
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.ssh1_host_key->rsa) < 0)
rsafail++;
if (rsa_private_decrypt(session_key_int, session_key_int,
sensitive_data.server_key->rsa) < 0)
rsafail++;
}
compute_session_id(session_id, cookie,
@ -1337,15 +1342,29 @@ do_ssh1_kex(void)
* least significant 256 bits of the integer; the first byte of the
* key is in the highest bits.
*/
BN_mask_bits(session_key_int, sizeof(session_key) * 8);
len = BN_num_bytes(session_key_int);
if (len < 0 || len > sizeof(session_key))
fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
get_remote_ipaddr(),
len, sizeof(session_key));
memset(session_key, 0, sizeof(session_key));
BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
if (!rsafail) {
BN_mask_bits(session_key_int, sizeof(session_key) * 8);
len = BN_num_bytes(session_key_int);
if (len < 0 || len > sizeof(session_key)) {
error("do_connection: bad session key len from %s: "
"session_key_int %d > sizeof(session_key) %d",
get_remote_ipaddr(), len, sizeof(session_key));
rsafail++;
} else {
memset(session_key, 0, sizeof(session_key));
BN_bn2bin(session_key_int,
session_key + sizeof(session_key) - len);
}
}
if (rsafail) {
log("do_connection: generating a fake encryption key");
for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
if (i % 4 == 0)
rand = arc4random();
session_key[i] = rand & 0xff;
rand >>= 8;
}
}
/* Destroy the decrypted integer. It is no longer needed. */
BN_clear_free(session_key_int);