From 0a843d9a0e805f14653a555f5c7a8ba99d62c12d Mon Sep 17 00:00:00 2001 From: "djm@openbsd.org" Date: Thu, 27 Dec 2018 03:25:24 +0000 Subject: 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 --- sshd.c | 118 +++-------------------------------------------------------------- 1 file changed, 4 insertions(+), 114 deletions(-) (limited to 'sshd.c') diff --git a/sshd.c b/sshd.c index fb9d9b60f..3461383a0 100644 --- a/sshd.c +++ b/sshd.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sshd.c,v 1.519 2018/11/19 04:12:32 djm Exp $ */ +/* $OpenBSD: sshd.c,v 1.520 2018/12/27 03:25:25 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -180,13 +180,6 @@ char **rexec_argv; int listen_socks[MAX_LISTEN_SOCKS]; int num_listen_socks = 0; -/* - * the client's version string, passed by sshd2 in compat mode. if != NULL, - * sshd will skip the version-number exchange - */ -char *client_version_string = NULL; -char *server_version_string = NULL; - /* Daemon's agent connection */ int auth_sock = -1; int have_agent = 0; @@ -363,108 +356,6 @@ grace_alarm_handler(int sig) ssh_remote_ipaddr(active_state), ssh_remote_port(active_state)); } -static void -sshd_exchange_identification(struct ssh *ssh, int sock_in, int sock_out) -{ - u_int i; - int remote_major, remote_minor; - char *s; - char buf[256]; /* Must not be larger than remote_version. */ - char remote_version[256]; /* Must be at least as big as buf. */ - - xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s\r\n", - PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION, - *options.version_addendum == '\0' ? "" : " ", - options.version_addendum); - - /* Send our protocol version identification. */ - if (atomicio(vwrite, sock_out, server_version_string, - strlen(server_version_string)) - != strlen(server_version_string)) { - logit("Could not write ident string to %s port %d", - ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); - cleanup_exit(255); - } - - /* Read other sides version identification. */ - memset(buf, 0, sizeof(buf)); - for (i = 0; i < sizeof(buf) - 1; i++) { - if (atomicio(read, sock_in, &buf[i], 1) != 1) { - logit("Did not receive identification string " - "from %s port %d", - ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); - cleanup_exit(255); - } - if (buf[i] == '\r') { - buf[i] = 0; - /* Kludge for F-Secure Macintosh < 1.0.2 */ - if (i == 12 && - strncmp(buf, "SSH-1.5-W1.0", 12) == 0) - break; - continue; - } - if (buf[i] == '\n') { - buf[i] = 0; - break; - } - } - buf[sizeof(buf) - 1] = 0; - client_version_string = xstrdup(buf); - - /* - * Check that the versions match. In future this might accept - * several versions and set appropriate flags to handle them. - */ - if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", - &remote_major, &remote_minor, remote_version) != 3) { - s = "Protocol mismatch.\n"; - (void) atomicio(vwrite, sock_out, s, strlen(s)); - logit("Bad protocol version identification '%.100s' " - "from %s port %d", client_version_string, - ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); - close(sock_in); - close(sock_out); - cleanup_exit(255); - } - debug("Client protocol version %d.%d; client software version %.100s", - remote_major, remote_minor, remote_version); - - ssh->compat = compat_datafellows(remote_version); - - if ((ssh->compat & SSH_BUG_PROBE) != 0) { - logit("probed from %s port %d with %s. Don't panic.", - ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), - client_version_string); - cleanup_exit(255); - } - if ((ssh->compat & SSH_BUG_SCANNER) != 0) { - logit("scanned from %s port %d with %s. Don't panic.", - ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), - client_version_string); - cleanup_exit(255); - } - if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) { - logit("Client version \"%.100s\" uses unsafe RSA signature " - "scheme; disabling use of RSA keys", remote_version); - } - - chop(server_version_string); - debug("Local version string %.200s", server_version_string); - - if (remote_major != 2 && - !(remote_major == 1 && remote_minor == 99)) { - s = "Protocol major versions differ.\n"; - (void) atomicio(vwrite, sock_out, s, strlen(s)); - close(sock_in); - close(sock_out); - logit("Protocol major versions differ for %s port %d: " - "%.200s vs. %.200s", - ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), - server_version_string, client_version_string); - cleanup_exit(255); - } -} - /* Destroy the host and server keys. They will no longer be needed. */ void destroy_sensitive_data(void) @@ -2115,7 +2006,9 @@ main(int ac, char **av) if (!debug_flag) alarm(options.login_grace_time); - sshd_exchange_identification(ssh, sock_in, sock_out); + if (kex_exchange_identification(ssh, -1, options.version_addendum) != 0) + cleanup_exit(255); /* error already logged */ + packet_set_nonblocking(); /* allocate authentication context */ @@ -2303,9 +2196,6 @@ do_ssh2_kex(void) # endif #endif kex->kex[KEX_C25519_SHA256] = kexc25519_server; - kex->server = 1; - kex->client_version_string=client_version_string; - kex->server_version_string=server_version_string; kex->load_host_public_key=&get_hostkey_public_by_type; kex->load_host_private_key=&get_hostkey_private_by_type; kex->host_key_index=&get_hostkey_index; -- cgit v1.2.3