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-rw-r--r--ChangeLog11
-rw-r--r--sshd.c63
2 files changed, 53 insertions, 21 deletions
diff --git a/ChangeLog b/ChangeLog
index d49ba05f..333decb4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -37,6 +37,15 @@
- markus@cvs.openbsd.org 2001/02/23 15:34:53
[serverloop.c]
debug2->3
+ - markus@cvs.openbsd.org 2001/02/23 18:15:13
+ [sshd.c]
+ the random session key depends now on the session_key_int
+ sent by the 'attacker'
+ dig1 = md5(cookie|session_key_int);
+ dig2 = md5(dig1|cookie|session_key_int);
+ fake_session_key = dig1|dig2;
+ this change is caused by a mail from anakin@pobox.com
+ patch based on discussions with my german advisor niels@openbsd.org
20010304
- (bal) Remove make-ssh-known-hosts.1 since it's no longer valid.
@@ -4229,4 +4238,4 @@
- Wrote replacements for strlcpy and mkdtemp
- Released 1.0pre1
-$Id: ChangeLog,v 1.863 2001/03/05 05:58:23 mouring Exp $
+$Id: ChangeLog,v 1.864 2001/03/05 06:00:29 mouring Exp $
diff --git a/sshd.c b/sshd.c
index bd90d0e5..2669a935 100644
--- a/sshd.c
+++ b/sshd.c
@@ -40,7 +40,7 @@
*/
#include "includes.h"
-RCSID("$OpenBSD: sshd.c,v 1.168 2001/02/19 23:09:05 deraadt Exp $");
+RCSID("$OpenBSD: sshd.c,v 1.169 2001/02/23 18:15:13 markus Exp $");
#include <openssl/dh.h>
#include <openssl/bn.h>
@@ -154,6 +154,7 @@ struct {
Key **host_keys; /* all private host keys */
int have_ssh1_key;
int have_ssh2_key;
+ u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
} sensitive_data;
/*
@@ -274,13 +275,23 @@ grace_alarm_handler(int sig)
void
generate_empheral_server_key(void)
{
+ u_int32_t rand = 0;
+ int i;
+
log("Generating %s%d bit RSA key.", sensitive_data.server_key ? "new " : "",
options.server_key_bits);
if (sensitive_data.server_key != NULL)
key_free(sensitive_data.server_key);
sensitive_data.server_key = key_generate(KEY_RSA1, options.server_key_bits);
- arc4random_stir();
log("RSA key generation complete.");
+
+ for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
+ if (i % 4 == 0)
+ rand = arc4random();
+ sensitive_data.ssh1_cookie[i] = rand & 0xff;
+ rand >>= 8;
+ }
+ arc4random_stir();
}
void
@@ -438,6 +449,7 @@ destroy_sensitive_data(void)
}
}
sensitive_data.ssh1_host_key = NULL;
+ memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
}
Key *
load_private_key_autodetect(const char *filename)
@@ -1338,14 +1350,6 @@ do_ssh1_kex(void)
sensitive_data.server_key->rsa) < 0)
rsafail++;
}
-
- compute_session_id(session_id, cookie,
- sensitive_data.ssh1_host_key->rsa->n,
- sensitive_data.server_key->rsa->n);
-
- /* Destroy the private and public keys. They will no longer be needed. */
- destroy_sensitive_data();
-
/*
* Extract session key from the decrypted integer. The key is in the
* least significant 256 bits of the integer; the first byte of the
@@ -1363,24 +1367,43 @@ do_ssh1_kex(void)
memset(session_key, 0, sizeof(session_key));
BN_bn2bin(session_key_int,
session_key + sizeof(session_key) - len);
+
+ compute_session_id(session_id, cookie,
+ sensitive_data.ssh1_host_key->rsa->n,
+ sensitive_data.server_key->rsa->n);
+ /*
+ * Xor the first 16 bytes of the session key with the
+ * session id.
+ */
+ for (i = 0; i < 16; i++)
+ session_key[i] ^= session_id[i];
}
}
if (rsafail) {
+ int bytes = BN_num_bytes(session_key_int);
+ char *buf = xmalloc(bytes);
+ MD5_CTX md;
+
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;
- }
+ BN_bn2bin(session_key_int, buf);
+ MD5_Init(&md);
+ MD5_Update(&md, buf, bytes);
+ MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
+ MD5_Final(session_key, &md);
+ MD5_Init(&md);
+ MD5_Update(&md, session_key, 16);
+ MD5_Update(&md, buf, bytes);
+ MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
+ MD5_Final(session_key + 16, &md);
+ memset(buf, 0, bytes);
+ xfree(buf);
}
+ /* Destroy the private and public keys. They will no longer be needed. */
+ destroy_sensitive_data();
+
/* Destroy the decrypted integer. It is no longer needed. */
BN_clear_free(session_key_int);
- /* Xor the first 16 bytes of the session key with the session id. */
- for (i = 0; i < 16; i++)
- session_key[i] ^= session_id[i];
-
/* Set the session key. From this on all communications will be encrypted. */
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);