upstream: move client/server SSH-* banners to buffers under

ssh->kex and factor out the banner exchange. This eliminates some common code
from the client and server.

Also be more strict about handling \r characters - these should only
be accepted immediately before \n (pointed out by Jann Horn).

Inspired by a patch from Markus Schmidt.
(lots of) feedback and ok markus@

OpenBSD-Commit-ID: 1cc7885487a6754f63641d7d3279b0941890275b

1 files changed, 23 insertions, 26 deletions

diff --git a/sshconnect2.c b/sshconnect2.c
index adb4e4cbd..19caebabc 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.290 2018/11/28 06:00:38 djm Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.291 2018/12/27 03:25:25 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -155,11 +155,10 @@ order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port)
 }
 
 void
-ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
+ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port)
 {
         char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
         char *s, *all_key;
-        struct kex *kex;
         int r;
 
         xxx_host = host;
@@ -199,36 +198,33 @@ ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port)
                     options.rekey_interval);
 
         /* start key exchange */
-        if ((r = kex_setup(active_state, myproposal)) != 0)
+        if ((r = kex_setup(ssh, myproposal)) != 0)
                 fatal("kex_setup: %s", ssh_err(r));
-        kex = active_state->kex;
 #ifdef WITH_OPENSSL
-        kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
-        kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
-        kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client;
-        kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client;
-        kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client;
-        kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
-        kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
+        ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
+        ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
+        ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client;
+        ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client;
+        ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client;
+        ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
+        ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
 # ifdef OPENSSL_HAS_ECC
-        kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
+        ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
 # endif
 #endif
-        kex->kex[KEX_C25519_SHA256] = kexc25519_client;
-        kex->client_version_string=client_version_string;
-        kex->server_version_string=server_version_string;
-        kex->verify_host_key=&verify_host_key_callback;
+        ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client;
+        ssh->kex->verify_host_key=&verify_host_key_callback;
 
-        ssh_dispatch_run_fatal(active_state, DISPATCH_BLOCK, &kex->done);
+        ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &ssh->kex->done);
 
         /* remove ext-info from the KEX proposals for rekeying */
         myproposal[PROPOSAL_KEX_ALGS] =
             compat_kex_proposal(options.kex_algorithms);
-        if ((r = kex_prop2buf(kex->my, myproposal)) != 0)
+        if ((r = kex_prop2buf(ssh->kex->my, myproposal)) != 0)
                 fatal("kex_prop2buf: %s", ssh_err(r));
 
-        session_id2 = kex->session_id;
-        session_id2_len = kex->session_id_len;
+        session_id2 = ssh->kex->session_id;
+        session_id2_len = ssh->kex->session_id_len;
 
 #ifdef DEBUG_KEXDH
         /* send 1st encrypted/maced/compressed message */
@@ -365,10 +361,9 @@ Authmethod authmethods[] = {
 };
 
 void
-ssh_userauth2(const char *local_user, const char *server_user, char *host,
-    Sensitive *sensitive)
+ssh_userauth2(struct ssh *ssh, const char *local_user,
+    const char *server_user, char *host, Sensitive *sensitive)
 {
-        struct ssh *ssh = active_state;
         Authctxt authctxt;
         int r;
 
@@ -392,8 +387,10 @@ ssh_userauth2(const char *local_user, const char *server_user, char *host,
         authctxt.info_req_seen = 0;
         authctxt.agent_fd = -1;
         pubkey_prepare(&authctxt);
-        if (authctxt.method == NULL)
-                fatal("ssh_userauth2: internal error: cannot send userauth none request");
+        if (authctxt.method == NULL) {
+                fatal("%s: internal error: cannot send userauth none request",
+                    __func__);
+        }
 
         if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_REQUEST)) != 0 ||
             (r = sshpkt_put_cstring(ssh, "ssh-userauth")) != 0 ||