[openssh-commits] [openssh] 02/02: upstream: more strictly enforce KEX state-machine by banning packet
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djm pushed a commit to branch master
in repository openssh.
commit 3dd0c64e08f1bba21d71996d635c7256c8c139d1
Author: djm at openbsd.org <djm at openbsd.org>
Date: Sun Jan 31 22:55:29 2021 +0000
upstream: more strictly enforce KEX state-machine by banning packet
types once they are received. Fixes memleak caused by duplicate
SSH2_MSG_KEX_DH_GEX_REQUEST (spotted by portable OpenSSH kex_fuzz via
oss-fuzz #30078).
ok markus@
OpenBSD-Commit-ID: 87331c715c095b587d5c88724694cdeb701c9def
---
kex.c | 4 ++--
kex.h | 3 ++-
kexgen.c | 8 +++++++-
kexgexc.c | 12 ++++++++----
kexgexs.c | 7 ++++++-
5 files changed, 25 insertions(+), 9 deletions(-)
diff --git a/kex.c b/kex.c
index b73f14d3..30425ab8 100644
--- a/kex.c
+++ b/kex.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.c,v 1.166 2021/01/27 23:49:46 djm Exp $ */
+/* $OpenBSD: kex.c,v 1.167 2021/01/31 22:55:29 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
*
@@ -405,7 +405,7 @@ kex_prop_free(char **proposal)
}
/* ARGSUSED */
-static int
+int
kex_protocol_error(int type, u_int32_t seq, struct ssh *ssh)
{
int r;
diff --git a/kex.h b/kex.h
index 18bfa923..9605ed52 100644
--- a/kex.h
+++ b/kex.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: kex.h,v 1.113 2021/01/27 10:05:28 djm Exp $ */
+/* $OpenBSD: kex.h,v 1.114 2021/01/31 22:55:29 djm Exp $ */
/*
* Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
@@ -193,6 +193,7 @@ int kex_verify_host_key(struct ssh *, struct sshkey *);
int kex_send_kexinit(struct ssh *);
int kex_input_kexinit(int, u_int32_t, struct ssh *);
int kex_input_ext_info(int, u_int32_t, struct ssh *);
+int kex_protocol_error(int, u_int32_t, struct ssh *);
int kex_derive_keys(struct ssh *, u_char *, u_int, const struct sshbuf *);
int kex_send_newkeys(struct ssh *);
int kex_start_rekex(struct ssh *);
diff --git a/kexgen.c b/kexgen.c
index 39a848f2..35b83ccf 100644
--- a/kexgen.c
+++ b/kexgen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgen.c,v 1.5 2020/12/29 00:59:15 djm Exp $ */
+/* $OpenBSD: kexgen.c,v 1.6 2021/01/31 22:55:29 djm Exp $ */
/*
* Copyright (c) 2019 Markus Friedl. All rights reserved.
*
@@ -148,6 +148,9 @@ input_kex_gen_reply(int type, u_int32_t seq, struct ssh *ssh)
size_t slen, hashlen;
int r;
+ debug("SSH2_MSG_KEX_ECDH_REPLY received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_REPLY, &kex_protocol_error);
+
/* hostkey */
if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
goto out;
@@ -254,6 +257,9 @@ input_kex_gen_init(int type, u_int32_t seq, struct ssh *ssh)
size_t slen, hashlen;
int r;
+ debug("SSH2_MSG_KEX_ECDH_INIT received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_ECDH_INIT, &kex_protocol_error);
+
if ((r = kex_load_hostkey(ssh, &server_host_private,
&server_host_public)) != 0)
goto out;
diff --git a/kexgexc.c b/kexgexc.c
index c3702c92..4a2e741d 100644
--- a/kexgexc.c
+++ b/kexgexc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexc.c,v 1.36 2021/01/27 09:26:54 djm Exp $ */
+/* $OpenBSD: kexgexc.c,v 1.37 2021/01/31 22:55:29 djm Exp $ */
/*
* Copyright (c) 2000 Niels Provos. All rights reserved.
* Copyright (c) 2001 Markus Friedl. All rights reserved.
@@ -83,6 +83,7 @@ kexgex_client(struct ssh *ssh)
fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
kex->min, kex->nbits, kex->max);
#endif
+ debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP,
&input_kex_dh_gex_group);
r = 0;
@@ -98,7 +99,8 @@ input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh)
const BIGNUM *pub_key;
int r, bits;
- debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
+ debug("SSH2_MSG_KEX_DH_GEX_GROUP received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, &kex_protocol_error);
if ((r = sshpkt_get_bignum2(ssh, &p)) != 0 ||
(r = sshpkt_get_bignum2(ssh, &g)) != 0 ||
@@ -130,7 +132,7 @@ input_kex_dh_gex_group(int type, u_int32_t seq, struct ssh *ssh)
BN_print_fp(stderr, pub_key);
fprintf(stderr, "\n");
#endif
- ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
+ debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
r = 0;
out:
@@ -153,7 +155,9 @@ input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
size_t slen, hashlen;
int r;
- debug("got SSH2_MSG_KEX_DH_GEX_REPLY");
+ debug("SSH2_MSG_KEX_DH_GEX_REPLY received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &kex_protocol_error);
+
/* key, cert */
if ((r = sshpkt_getb_froms(ssh, &server_host_key_blob)) != 0)
goto out;
diff --git a/kexgexs.c b/kexgexs.c
index 8ee3aacc..f0fbcb91 100644
--- a/kexgexs.c
+++ b/kexgexs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexs.c,v 1.42 2019/01/23 00:30:41 djm Exp $ */
+/* $OpenBSD: kexgexs.c,v 1.43 2021/01/31 22:55:29 djm Exp $ */
/*
* Copyright (c) 2000 Niels Provos. All rights reserved.
* Copyright (c) 2001 Markus Friedl. All rights reserved.
@@ -77,6 +77,8 @@ input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
const BIGNUM *dh_p, *dh_g;
debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST, &kex_protocol_error);
+
if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
(r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
(r = sshpkt_get_u32(ssh, &max)) != 0 ||
@@ -136,6 +138,9 @@ input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
size_t slen, hashlen;
int r;
+ debug("SSH2_MSG_KEX_DH_GEX_INIT received");
+ ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &kex_protocol_error);
+
if ((r = kex_load_hostkey(ssh, &server_host_private,
&server_host_public)) != 0)
goto out;
--
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