1832 lines
49 KiB
C
1832 lines
49 KiB
C
/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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* This program is the ssh daemon. It listens for connections from clients,
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* and performs authentication, executes use commands or shell, and forwards
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* information to/from the application to the user client over an encrypted
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* connection. This can also handle forwarding of X11, TCP/IP, and
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* authentication agent connections.
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*
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*
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* SSH2 implementation:
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* Privilege Separation:
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*
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* Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
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* Copyright (c) 2002 Niels Provos. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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RCSID("$OpenBSD: sshd.c,v 1.260 2002/09/27 10:42:09 mickey Exp $");
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RCSID("$FreeBSD$");
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#include <openssl/dh.h>
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#include <openssl/bn.h>
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#include <openssl/md5.h>
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#include <openssl/rand.h>
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#ifdef HAVE_SECUREWARE
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#include <sys/security.h>
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#include <prot.h>
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#endif
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#include "ssh.h"
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#include "ssh1.h"
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#include "ssh2.h"
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#include "xmalloc.h"
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#include "rsa.h"
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#include "sshpty.h"
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#include "packet.h"
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#include "mpaux.h"
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#include "log.h"
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#include "servconf.h"
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#include "uidswap.h"
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#include "compat.h"
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#include "buffer.h"
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#include "cipher.h"
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#include "kex.h"
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#include "key.h"
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#include "dh.h"
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#include "myproposal.h"
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#include "authfile.h"
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#include "pathnames.h"
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#include "atomicio.h"
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#include "canohost.h"
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#include "auth.h"
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#include "misc.h"
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#include "dispatch.h"
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#include "channels.h"
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#include "session.h"
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#include "monitor_mm.h"
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#include "monitor.h"
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#include "monitor_wrap.h"
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#include "monitor_fdpass.h"
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#ifdef LIBWRAP
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#include <tcpd.h>
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#include <syslog.h>
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int allow_severity = LOG_INFO;
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int deny_severity = LOG_WARNING;
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#endif /* LIBWRAP */
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#ifndef O_NOCTTY
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#define O_NOCTTY 0
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#endif
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#ifdef HAVE___PROGNAME
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extern char *__progname;
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#else
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char *__progname;
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#endif
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/* Server configuration options. */
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ServerOptions options;
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/* Name of the server configuration file. */
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char *config_file_name = _PATH_SERVER_CONFIG_FILE;
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/*
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* Flag indicating whether IPv4 or IPv6. This can be set on the command line.
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* Default value is AF_UNSPEC means both IPv4 and IPv6.
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*/
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#ifdef IPV4_DEFAULT
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int IPv4or6 = AF_INET;
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#else
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int IPv4or6 = AF_UNSPEC;
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#endif
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/*
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* Debug mode flag. This can be set on the command line. If debug
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* mode is enabled, extra debugging output will be sent to the system
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* log, the daemon will not go to background, and will exit after processing
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* the first connection.
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*/
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int debug_flag = 0;
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/* Flag indicating that the daemon should only test the configuration and keys. */
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int test_flag = 0;
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/* Flag indicating that the daemon is being started from inetd. */
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int inetd_flag = 0;
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/* Flag indicating that sshd should not detach and become a daemon. */
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int no_daemon_flag = 0;
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/* debug goes to stderr unless inetd_flag is set */
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int log_stderr = 0;
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/* Saved arguments to main(). */
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char **saved_argv;
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int saved_argc;
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/*
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* The sockets that the server is listening; this is used in the SIGHUP
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* signal handler.
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*/
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#define MAX_LISTEN_SOCKS 16
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int listen_socks[MAX_LISTEN_SOCKS];
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int num_listen_socks = 0;
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/*
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* the client's version string, passed by sshd2 in compat mode. if != NULL,
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* sshd will skip the version-number exchange
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*/
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char *client_version_string = NULL;
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char *server_version_string = NULL;
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/* for rekeying XXX fixme */
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Kex *xxx_kex;
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/*
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* Any really sensitive data in the application is contained in this
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* structure. The idea is that this structure could be locked into memory so
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* that the pages do not get written into swap. However, there are some
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* problems. The private key contains BIGNUMs, and we do not (in principle)
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* have access to the internals of them, and locking just the structure is
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* not very useful. Currently, memory locking is not implemented.
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*/
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struct {
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Key *server_key; /* ephemeral server key */
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Key *ssh1_host_key; /* ssh1 host key */
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Key **host_keys; /* all private host keys */
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int have_ssh1_key;
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int have_ssh2_key;
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u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
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} sensitive_data;
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/*
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* Flag indicating whether the RSA server key needs to be regenerated.
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* Is set in the SIGALRM handler and cleared when the key is regenerated.
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*/
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static volatile sig_atomic_t key_do_regen = 0;
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/* This is set to true when a signal is received. */
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static volatile sig_atomic_t received_sighup = 0;
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static volatile sig_atomic_t received_sigterm = 0;
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/* session identifier, used by RSA-auth */
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u_char session_id[16];
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/* same for ssh2 */
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u_char *session_id2 = NULL;
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int session_id2_len = 0;
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/* record remote hostname or ip */
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u_int utmp_len = MAXHOSTNAMELEN;
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/* options.max_startup sized array of fd ints */
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int *startup_pipes = NULL;
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int startup_pipe; /* in child */
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/* variables used for privilege separation */
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extern struct monitor *pmonitor;
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extern int use_privsep;
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/* Prototypes for various functions defined later in this file. */
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void destroy_sensitive_data(void);
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void demote_sensitive_data(void);
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static void do_ssh1_kex(void);
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static void do_ssh2_kex(void);
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/*
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* Close all listening sockets
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*/
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static void
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close_listen_socks(void)
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{
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int i;
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for (i = 0; i < num_listen_socks; i++)
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close(listen_socks[i]);
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num_listen_socks = -1;
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}
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static void
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close_startup_pipes(void)
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{
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int i;
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if (startup_pipes)
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for (i = 0; i < options.max_startups; i++)
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if (startup_pipes[i] != -1)
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close(startup_pipes[i]);
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}
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/*
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* Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
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* the effect is to reread the configuration file (and to regenerate
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* the server key).
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*/
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static void
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sighup_handler(int sig)
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{
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int save_errno = errno;
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received_sighup = 1;
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signal(SIGHUP, sighup_handler);
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errno = save_errno;
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}
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/*
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* Called from the main program after receiving SIGHUP.
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* Restarts the server.
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*/
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static void
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sighup_restart(void)
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{
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log("Received SIGHUP; restarting.");
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close_listen_socks();
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close_startup_pipes();
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execv(saved_argv[0], saved_argv);
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log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
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strerror(errno));
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exit(1);
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}
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/*
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* Generic signal handler for terminating signals in the master daemon.
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*/
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static void
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sigterm_handler(int sig)
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{
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received_sigterm = sig;
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}
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/*
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* SIGCHLD handler. This is called whenever a child dies. This will then
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* reap any zombies left by exited children.
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*/
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static void
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main_sigchld_handler(int sig)
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{
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int save_errno = errno;
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pid_t pid;
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int status;
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while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
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(pid < 0 && errno == EINTR))
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;
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signal(SIGCHLD, main_sigchld_handler);
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errno = save_errno;
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}
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/*
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* Signal handler for the alarm after the login grace period has expired.
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*/
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static void
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grace_alarm_handler(int sig)
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{
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/* XXX no idea how fix this signal handler */
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/* Log error and exit. */
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fatal("Timeout before authentication for %s", get_remote_ipaddr());
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}
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/*
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* Signal handler for the key regeneration alarm. Note that this
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* alarm only occurs in the daemon waiting for connections, and it does not
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* do anything with the private key or random state before forking.
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* Thus there should be no concurrency control/asynchronous execution
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* problems.
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*/
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static void
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generate_ephemeral_server_key(void)
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{
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u_int32_t rnd = 0;
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int i;
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verbose("Generating %s%d bit RSA key.",
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sensitive_data.server_key ? "new " : "", options.server_key_bits);
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if (sensitive_data.server_key != NULL)
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key_free(sensitive_data.server_key);
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sensitive_data.server_key = key_generate(KEY_RSA1,
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options.server_key_bits);
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verbose("RSA key generation complete.");
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for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
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if (i % 4 == 0)
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rnd = arc4random();
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sensitive_data.ssh1_cookie[i] = rnd & 0xff;
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rnd >>= 8;
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}
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arc4random_stir();
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}
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static void
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key_regeneration_alarm(int sig)
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{
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int save_errno = errno;
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signal(SIGALRM, SIG_DFL);
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errno = save_errno;
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key_do_regen = 1;
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}
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static void
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sshd_exchange_identification(int sock_in, int sock_out)
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{
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int i, mismatch;
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int remote_major, remote_minor;
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int major, minor;
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char *s;
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char buf[256]; /* Must not be larger than remote_version. */
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char remote_version[256]; /* Must be at least as big as buf. */
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if ((options.protocol & SSH_PROTO_1) &&
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(options.protocol & SSH_PROTO_2)) {
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major = PROTOCOL_MAJOR_1;
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minor = 99;
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} else if (options.protocol & SSH_PROTO_2) {
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major = PROTOCOL_MAJOR_2;
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minor = PROTOCOL_MINOR_2;
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} else {
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major = PROTOCOL_MAJOR_1;
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minor = PROTOCOL_MINOR_1;
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}
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snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
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server_version_string = xstrdup(buf);
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if (client_version_string == NULL) {
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/* Send our protocol version identification. */
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if (atomicio(write, sock_out, server_version_string,
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strlen(server_version_string))
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!= strlen(server_version_string)) {
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log("Could not write ident string to %s", get_remote_ipaddr());
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fatal_cleanup();
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}
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/* Read other sides version identification. */
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memset(buf, 0, sizeof(buf));
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for (i = 0; i < sizeof(buf) - 1; i++) {
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if (atomicio(read, sock_in, &buf[i], 1) != 1) {
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log("Did not receive identification string from %s",
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get_remote_ipaddr());
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fatal_cleanup();
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}
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if (buf[i] == '\r') {
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buf[i] = 0;
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/* Kludge for F-Secure Macintosh < 1.0.2 */
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if (i == 12 &&
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strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
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break;
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continue;
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}
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if (buf[i] == '\n') {
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buf[i] = 0;
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break;
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}
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}
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buf[sizeof(buf) - 1] = 0;
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client_version_string = xstrdup(buf);
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}
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/*
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* Check that the versions match. In future this might accept
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* several versions and set appropriate flags to handle them.
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*/
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if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
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&remote_major, &remote_minor, remote_version) != 3) {
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s = "Protocol mismatch.\n";
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(void) atomicio(write, sock_out, s, strlen(s));
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close(sock_in);
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close(sock_out);
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log("Bad protocol version identification '%.100s' from %s",
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client_version_string, get_remote_ipaddr());
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fatal_cleanup();
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}
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debug("Client protocol version %d.%d; client software version %.100s",
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remote_major, remote_minor, remote_version);
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compat_datafellows(remote_version);
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if (datafellows & SSH_BUG_PROBE) {
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log("probed from %s with %s. Don't panic.",
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get_remote_ipaddr(), client_version_string);
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fatal_cleanup();
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}
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if (datafellows & SSH_BUG_SCANNER) {
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log("scanned from %s with %s. Don't panic.",
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get_remote_ipaddr(), client_version_string);
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fatal_cleanup();
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}
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mismatch = 0;
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switch (remote_major) {
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case 1:
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if (remote_minor == 99) {
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if (options.protocol & SSH_PROTO_2)
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enable_compat20();
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else
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mismatch = 1;
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break;
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}
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if (!(options.protocol & SSH_PROTO_1)) {
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mismatch = 1;
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break;
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}
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if (remote_minor < 3) {
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packet_disconnect("Your ssh version is too old and "
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"is no longer supported. Please install a newer version.");
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} else if (remote_minor == 3) {
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/* note that this disables agent-forwarding */
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enable_compat13();
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}
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break;
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case 2:
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if (options.protocol & SSH_PROTO_2) {
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enable_compat20();
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break;
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}
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/* FALLTHROUGH */
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default:
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mismatch = 1;
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break;
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}
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chop(server_version_string);
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debug("Local version string %.200s", server_version_string);
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if (mismatch) {
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s = "Protocol major versions differ.\n";
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(void) atomicio(write, sock_out, s, strlen(s));
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close(sock_in);
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close(sock_out);
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log("Protocol major versions differ for %s: %.200s vs. %.200s",
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get_remote_ipaddr(),
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server_version_string, client_version_string);
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fatal_cleanup();
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}
|
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}
|
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|
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/* Destroy the host and server keys. They will no longer be needed. */
|
|
void
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destroy_sensitive_data(void)
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{
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int i;
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if (sensitive_data.server_key) {
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key_free(sensitive_data.server_key);
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sensitive_data.server_key = NULL;
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}
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for (i = 0; i < options.num_host_key_files; i++) {
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if (sensitive_data.host_keys[i]) {
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key_free(sensitive_data.host_keys[i]);
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sensitive_data.host_keys[i] = NULL;
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}
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}
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sensitive_data.ssh1_host_key = NULL;
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memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
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}
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|
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/* Demote private to public keys for network child */
|
|
void
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demote_sensitive_data(void)
|
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{
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Key *tmp;
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int i;
|
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|
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if (sensitive_data.server_key) {
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tmp = key_demote(sensitive_data.server_key);
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key_free(sensitive_data.server_key);
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sensitive_data.server_key = tmp;
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}
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for (i = 0; i < options.num_host_key_files; i++) {
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if (sensitive_data.host_keys[i]) {
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tmp = key_demote(sensitive_data.host_keys[i]);
|
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key_free(sensitive_data.host_keys[i]);
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sensitive_data.host_keys[i] = tmp;
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if (tmp->type == KEY_RSA1)
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sensitive_data.ssh1_host_key = tmp;
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}
|
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}
|
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|
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/* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
|
|
}
|
|
|
|
static void
|
|
privsep_preauth_child(void)
|
|
{
|
|
u_int32_t rnd[256];
|
|
gid_t gidset[1];
|
|
struct passwd *pw;
|
|
int i;
|
|
|
|
/* Enable challenge-response authentication for privilege separation */
|
|
privsep_challenge_enable();
|
|
|
|
for (i = 0; i < 256; i++)
|
|
rnd[i] = arc4random();
|
|
RAND_seed(rnd, sizeof(rnd));
|
|
|
|
/* Demote the private keys to public keys. */
|
|
demote_sensitive_data();
|
|
|
|
if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
|
|
fatal("Privilege separation user %s does not exist",
|
|
SSH_PRIVSEP_USER);
|
|
memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
|
|
endpwent();
|
|
|
|
/* Change our root directory */
|
|
if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
|
|
fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
|
|
strerror(errno));
|
|
if (chdir("/") == -1)
|
|
fatal("chdir(\"/\"): %s", strerror(errno));
|
|
|
|
/* Drop our privileges */
|
|
debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
|
|
(u_int)pw->pw_gid);
|
|
#if 0
|
|
/* XXX not ready, to heavy after chroot */
|
|
do_setusercontext(pw);
|
|
#else
|
|
gidset[0] = pw->pw_gid;
|
|
if (setgid(pw->pw_gid) < 0)
|
|
fatal("setgid failed for %u", pw->pw_gid );
|
|
if (setgroups(1, gidset) < 0)
|
|
fatal("setgroups: %.100s", strerror(errno));
|
|
permanently_set_uid(pw);
|
|
#endif
|
|
}
|
|
|
|
static Authctxt *
|
|
privsep_preauth(void)
|
|
{
|
|
Authctxt *authctxt = NULL;
|
|
int status;
|
|
pid_t pid;
|
|
|
|
/* Set up unprivileged child process to deal with network data */
|
|
pmonitor = monitor_init();
|
|
/* Store a pointer to the kex for later rekeying */
|
|
pmonitor->m_pkex = &xxx_kex;
|
|
|
|
pid = fork();
|
|
if (pid == -1) {
|
|
fatal("fork of unprivileged child failed");
|
|
} else if (pid != 0) {
|
|
fatal_remove_cleanup((void (*) (void *)) packet_close, NULL);
|
|
|
|
debug2("Network child is on pid %ld", (long)pid);
|
|
|
|
close(pmonitor->m_recvfd);
|
|
authctxt = monitor_child_preauth(pmonitor);
|
|
close(pmonitor->m_sendfd);
|
|
|
|
/* Sync memory */
|
|
monitor_sync(pmonitor);
|
|
|
|
/* Wait for the child's exit status */
|
|
while (waitpid(pid, &status, 0) < 0)
|
|
if (errno != EINTR)
|
|
break;
|
|
|
|
/* Reinstall, since the child has finished */
|
|
fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
|
|
|
|
return (authctxt);
|
|
} else {
|
|
/* child */
|
|
|
|
close(pmonitor->m_sendfd);
|
|
|
|
/* Demote the child */
|
|
if (getuid() == 0 || geteuid() == 0)
|
|
privsep_preauth_child();
|
|
setproctitle("%s", "[net]");
|
|
}
|
|
return (NULL);
|
|
}
|
|
|
|
static void
|
|
privsep_postauth(Authctxt *authctxt)
|
|
{
|
|
extern Authctxt *x_authctxt;
|
|
|
|
/* XXX - Remote port forwarding */
|
|
x_authctxt = authctxt;
|
|
|
|
#ifdef DISABLE_FD_PASSING
|
|
if (1) {
|
|
#else
|
|
if (authctxt->pw->pw_uid == 0 || options.use_login) {
|
|
#endif
|
|
/* File descriptor passing is broken or root login */
|
|
monitor_apply_keystate(pmonitor);
|
|
use_privsep = 0;
|
|
return;
|
|
}
|
|
|
|
/* Authentication complete */
|
|
alarm(0);
|
|
if (startup_pipe != -1) {
|
|
close(startup_pipe);
|
|
startup_pipe = -1;
|
|
}
|
|
|
|
/* New socket pair */
|
|
monitor_reinit(pmonitor);
|
|
|
|
pmonitor->m_pid = fork();
|
|
if (pmonitor->m_pid == -1)
|
|
fatal("fork of unprivileged child failed");
|
|
else if (pmonitor->m_pid != 0) {
|
|
fatal_remove_cleanup((void (*) (void *)) packet_close, NULL);
|
|
|
|
debug2("User child is on pid %ld", (long)pmonitor->m_pid);
|
|
close(pmonitor->m_recvfd);
|
|
monitor_child_postauth(pmonitor);
|
|
|
|
/* NEVERREACHED */
|
|
exit(0);
|
|
}
|
|
|
|
close(pmonitor->m_sendfd);
|
|
|
|
/* Demote the private keys to public keys. */
|
|
demote_sensitive_data();
|
|
|
|
/* Drop privileges */
|
|
do_setusercontext(authctxt->pw);
|
|
|
|
/* It is safe now to apply the key state */
|
|
monitor_apply_keystate(pmonitor);
|
|
}
|
|
|
|
static char *
|
|
list_hostkey_types(void)
|
|
{
|
|
Buffer b;
|
|
char *p;
|
|
int i;
|
|
|
|
buffer_init(&b);
|
|
for (i = 0; i < options.num_host_key_files; i++) {
|
|
Key *key = sensitive_data.host_keys[i];
|
|
if (key == NULL)
|
|
continue;
|
|
switch (key->type) {
|
|
case KEY_RSA:
|
|
case KEY_DSA:
|
|
if (buffer_len(&b) > 0)
|
|
buffer_append(&b, ",", 1);
|
|
p = key_ssh_name(key);
|
|
buffer_append(&b, p, strlen(p));
|
|
break;
|
|
}
|
|
}
|
|
buffer_append(&b, "\0", 1);
|
|
p = xstrdup(buffer_ptr(&b));
|
|
buffer_free(&b);
|
|
debug("list_hostkey_types: %s", p);
|
|
return p;
|
|
}
|
|
|
|
Key *
|
|
get_hostkey_by_type(int type)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < options.num_host_key_files; i++) {
|
|
Key *key = sensitive_data.host_keys[i];
|
|
if (key != NULL && key->type == type)
|
|
return key;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
Key *
|
|
get_hostkey_by_index(int ind)
|
|
{
|
|
if (ind < 0 || ind >= options.num_host_key_files)
|
|
return (NULL);
|
|
return (sensitive_data.host_keys[ind]);
|
|
}
|
|
|
|
int
|
|
get_hostkey_index(Key *key)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < options.num_host_key_files; i++) {
|
|
if (key == sensitive_data.host_keys[i])
|
|
return (i);
|
|
}
|
|
return (-1);
|
|
}
|
|
|
|
/*
|
|
* returns 1 if connection should be dropped, 0 otherwise.
|
|
* dropping starts at connection #max_startups_begin with a probability
|
|
* of (max_startups_rate/100). the probability increases linearly until
|
|
* all connections are dropped for startups > max_startups
|
|
*/
|
|
static int
|
|
drop_connection(int startups)
|
|
{
|
|
double p, r;
|
|
|
|
if (startups < options.max_startups_begin)
|
|
return 0;
|
|
if (startups >= options.max_startups)
|
|
return 1;
|
|
if (options.max_startups_rate == 100)
|
|
return 1;
|
|
|
|
p = 100 - options.max_startups_rate;
|
|
p *= startups - options.max_startups_begin;
|
|
p /= (double) (options.max_startups - options.max_startups_begin);
|
|
p += options.max_startups_rate;
|
|
p /= 100.0;
|
|
r = arc4random() / (double) UINT_MAX;
|
|
|
|
debug("drop_connection: p %g, r %g", p, r);
|
|
return (r < p) ? 1 : 0;
|
|
}
|
|
|
|
static void
|
|
usage(void)
|
|
{
|
|
fprintf(stderr, "sshd version %s\n", SSH_VERSION);
|
|
fprintf(stderr, "Usage: %s [options]\n", __progname);
|
|
fprintf(stderr, "Options:\n");
|
|
fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
|
|
fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
|
|
fprintf(stderr, " -i Started from inetd\n");
|
|
fprintf(stderr, " -D Do not fork into daemon mode\n");
|
|
fprintf(stderr, " -t Only test configuration file and keys\n");
|
|
fprintf(stderr, " -q Quiet (no logging)\n");
|
|
fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
|
|
fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
|
|
fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
|
|
fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
|
|
fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
|
|
_PATH_HOST_KEY_FILE);
|
|
fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
|
|
fprintf(stderr, " -4 Use IPv4 only\n");
|
|
fprintf(stderr, " -6 Use IPv6 only\n");
|
|
fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n");
|
|
exit(1);
|
|
}
|
|
|
|
/*
|
|
* Main program for the daemon.
|
|
*/
|
|
int
|
|
main(int ac, char **av)
|
|
{
|
|
extern char *optarg;
|
|
extern int optind;
|
|
int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
|
|
pid_t pid;
|
|
socklen_t fromlen;
|
|
fd_set *fdset;
|
|
struct sockaddr_storage from;
|
|
const char *remote_ip;
|
|
int remote_port;
|
|
FILE *f;
|
|
struct addrinfo *ai;
|
|
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
|
|
int listen_sock, maxfd;
|
|
int startup_p[2];
|
|
int startups = 0;
|
|
Authctxt *authctxt;
|
|
Key *key;
|
|
int ret, key_used = 0;
|
|
|
|
#ifdef HAVE_SECUREWARE
|
|
(void)set_auth_parameters(ac, av);
|
|
#endif
|
|
__progname = get_progname(av[0]);
|
|
init_rng();
|
|
|
|
/* Save argv. */
|
|
saved_argc = ac;
|
|
saved_argv = av;
|
|
|
|
/* Initialize configuration options to their default values. */
|
|
initialize_server_options(&options);
|
|
|
|
/* Parse command-line arguments. */
|
|
while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) {
|
|
switch (opt) {
|
|
case '4':
|
|
IPv4or6 = AF_INET;
|
|
break;
|
|
case '6':
|
|
IPv4or6 = AF_INET6;
|
|
break;
|
|
case 'f':
|
|
config_file_name = optarg;
|
|
break;
|
|
case 'd':
|
|
if (0 == debug_flag) {
|
|
debug_flag = 1;
|
|
options.log_level = SYSLOG_LEVEL_DEBUG1;
|
|
} else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
|
|
options.log_level++;
|
|
} else {
|
|
fprintf(stderr, "Too high debugging level.\n");
|
|
exit(1);
|
|
}
|
|
break;
|
|
case 'D':
|
|
no_daemon_flag = 1;
|
|
break;
|
|
case 'e':
|
|
log_stderr = 1;
|
|
break;
|
|
case 'i':
|
|
inetd_flag = 1;
|
|
break;
|
|
case 'Q':
|
|
/* ignored */
|
|
break;
|
|
case 'q':
|
|
options.log_level = SYSLOG_LEVEL_QUIET;
|
|
break;
|
|
case 'b':
|
|
options.server_key_bits = atoi(optarg);
|
|
break;
|
|
case 'p':
|
|
options.ports_from_cmdline = 1;
|
|
if (options.num_ports >= MAX_PORTS) {
|
|
fprintf(stderr, "too many ports.\n");
|
|
exit(1);
|
|
}
|
|
options.ports[options.num_ports++] = a2port(optarg);
|
|
if (options.ports[options.num_ports-1] == 0) {
|
|
fprintf(stderr, "Bad port number.\n");
|
|
exit(1);
|
|
}
|
|
break;
|
|
case 'g':
|
|
if ((options.login_grace_time = convtime(optarg)) == -1) {
|
|
fprintf(stderr, "Invalid login grace time.\n");
|
|
exit(1);
|
|
}
|
|
break;
|
|
case 'k':
|
|
if ((options.key_regeneration_time = convtime(optarg)) == -1) {
|
|
fprintf(stderr, "Invalid key regeneration interval.\n");
|
|
exit(1);
|
|
}
|
|
break;
|
|
case 'h':
|
|
if (options.num_host_key_files >= MAX_HOSTKEYS) {
|
|
fprintf(stderr, "too many host keys.\n");
|
|
exit(1);
|
|
}
|
|
options.host_key_files[options.num_host_key_files++] = optarg;
|
|
break;
|
|
case 'V':
|
|
client_version_string = optarg;
|
|
/* only makes sense with inetd_flag, i.e. no listen() */
|
|
inetd_flag = 1;
|
|
break;
|
|
case 't':
|
|
test_flag = 1;
|
|
break;
|
|
case 'u':
|
|
utmp_len = atoi(optarg);
|
|
if (utmp_len > MAXHOSTNAMELEN) {
|
|
fprintf(stderr, "Invalid utmp length.\n");
|
|
exit(1);
|
|
}
|
|
break;
|
|
case 'o':
|
|
if (process_server_config_line(&options, optarg,
|
|
"command-line", 0) != 0)
|
|
exit(1);
|
|
break;
|
|
case '?':
|
|
default:
|
|
usage();
|
|
break;
|
|
}
|
|
}
|
|
SSLeay_add_all_algorithms();
|
|
channel_set_af(IPv4or6);
|
|
|
|
/*
|
|
* Force logging to stderr until we have loaded the private host
|
|
* key (unless started from inetd)
|
|
*/
|
|
log_init(__progname,
|
|
options.log_level == SYSLOG_LEVEL_NOT_SET ?
|
|
SYSLOG_LEVEL_INFO : options.log_level,
|
|
options.log_facility == SYSLOG_FACILITY_NOT_SET ?
|
|
SYSLOG_FACILITY_AUTH : options.log_facility,
|
|
!inetd_flag);
|
|
|
|
#ifdef _UNICOS
|
|
/* Cray can define user privs drop all prives now!
|
|
* Not needed on PRIV_SU systems!
|
|
*/
|
|
drop_cray_privs();
|
|
#endif
|
|
|
|
seed_rng();
|
|
|
|
/* Read server configuration options from the configuration file. */
|
|
read_server_config(&options, config_file_name);
|
|
|
|
/* Fill in default values for those options not explicitly set. */
|
|
fill_default_server_options(&options);
|
|
|
|
/* Check that there are no remaining arguments. */
|
|
if (optind < ac) {
|
|
fprintf(stderr, "Extra argument %s.\n", av[optind]);
|
|
exit(1);
|
|
}
|
|
|
|
debug("sshd version %.100s", SSH_VERSION);
|
|
|
|
/* load private host keys */
|
|
sensitive_data.host_keys = xmalloc(options.num_host_key_files *
|
|
sizeof(Key *));
|
|
for (i = 0; i < options.num_host_key_files; i++)
|
|
sensitive_data.host_keys[i] = NULL;
|
|
sensitive_data.server_key = NULL;
|
|
sensitive_data.ssh1_host_key = NULL;
|
|
sensitive_data.have_ssh1_key = 0;
|
|
sensitive_data.have_ssh2_key = 0;
|
|
|
|
for (i = 0; i < options.num_host_key_files; i++) {
|
|
key = key_load_private(options.host_key_files[i], "", NULL);
|
|
sensitive_data.host_keys[i] = key;
|
|
if (key == NULL) {
|
|
error("Could not load host key: %s",
|
|
options.host_key_files[i]);
|
|
sensitive_data.host_keys[i] = NULL;
|
|
continue;
|
|
}
|
|
switch (key->type) {
|
|
case KEY_RSA1:
|
|
sensitive_data.ssh1_host_key = key;
|
|
sensitive_data.have_ssh1_key = 1;
|
|
break;
|
|
case KEY_RSA:
|
|
case KEY_DSA:
|
|
sensitive_data.have_ssh2_key = 1;
|
|
break;
|
|
}
|
|
debug("private host key: #%d type %d %s", i, key->type,
|
|
key_type(key));
|
|
}
|
|
if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
|
|
log("Disabling protocol version 1. Could not load host key");
|
|
options.protocol &= ~SSH_PROTO_1;
|
|
}
|
|
if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
|
|
log("Disabling protocol version 2. Could not load host key");
|
|
options.protocol &= ~SSH_PROTO_2;
|
|
}
|
|
if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
|
|
log("sshd: no hostkeys available -- exiting.");
|
|
exit(1);
|
|
}
|
|
|
|
/* Check certain values for sanity. */
|
|
if (options.protocol & SSH_PROTO_1) {
|
|
if (options.server_key_bits < 512 ||
|
|
options.server_key_bits > 32768) {
|
|
fprintf(stderr, "Bad server key size.\n");
|
|
exit(1);
|
|
}
|
|
/*
|
|
* Check that server and host key lengths differ sufficiently. This
|
|
* is necessary to make double encryption work with rsaref. Oh, I
|
|
* hate software patents. I dont know if this can go? Niels
|
|
*/
|
|
if (options.server_key_bits >
|
|
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
|
|
SSH_KEY_BITS_RESERVED && options.server_key_bits <
|
|
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
|
|
SSH_KEY_BITS_RESERVED) {
|
|
options.server_key_bits =
|
|
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
|
|
SSH_KEY_BITS_RESERVED;
|
|
debug("Forcing server key to %d bits to make it differ from host key.",
|
|
options.server_key_bits);
|
|
}
|
|
}
|
|
|
|
if (use_privsep) {
|
|
struct passwd *pw;
|
|
struct stat st;
|
|
|
|
if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
|
|
fatal("Privilege separation user %s does not exist",
|
|
SSH_PRIVSEP_USER);
|
|
if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
|
|
(S_ISDIR(st.st_mode) == 0))
|
|
fatal("Missing privilege separation directory: %s",
|
|
_PATH_PRIVSEP_CHROOT_DIR);
|
|
|
|
#ifdef HAVE_CYGWIN
|
|
if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
|
|
(st.st_uid != getuid () ||
|
|
(st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
|
|
#else
|
|
if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
|
|
#endif
|
|
fatal("Bad owner or mode for %s",
|
|
_PATH_PRIVSEP_CHROOT_DIR);
|
|
}
|
|
|
|
/* Configuration looks good, so exit if in test mode. */
|
|
if (test_flag)
|
|
exit(0);
|
|
|
|
/*
|
|
* Clear out any supplemental groups we may have inherited. This
|
|
* prevents inadvertent creation of files with bad modes (in the
|
|
* portable version at least, it's certainly possible for PAM
|
|
* to create a file, and we can't control the code in every
|
|
* module which might be used).
|
|
*/
|
|
if (setgroups(0, NULL) < 0)
|
|
debug("setgroups() failed: %.200s", strerror(errno));
|
|
|
|
/* Initialize the log (it is reinitialized below in case we forked). */
|
|
if (debug_flag && !inetd_flag)
|
|
log_stderr = 1;
|
|
log_init(__progname, options.log_level, options.log_facility, log_stderr);
|
|
|
|
/*
|
|
* If not in debugging mode, and not started from inetd, disconnect
|
|
* from the controlling terminal, and fork. The original process
|
|
* exits.
|
|
*/
|
|
if (!(debug_flag || inetd_flag || no_daemon_flag)) {
|
|
#ifdef TIOCNOTTY
|
|
int fd;
|
|
#endif /* TIOCNOTTY */
|
|
if (daemon(0, 0) < 0)
|
|
fatal("daemon() failed: %.200s", strerror(errno));
|
|
|
|
/* Disconnect from the controlling tty. */
|
|
#ifdef TIOCNOTTY
|
|
fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
|
|
if (fd >= 0) {
|
|
(void) ioctl(fd, TIOCNOTTY, NULL);
|
|
close(fd);
|
|
}
|
|
#endif /* TIOCNOTTY */
|
|
}
|
|
/* Reinitialize the log (because of the fork above). */
|
|
log_init(__progname, options.log_level, options.log_facility, log_stderr);
|
|
|
|
/* Initialize the random number generator. */
|
|
arc4random_stir();
|
|
|
|
/* Chdir to the root directory so that the current disk can be
|
|
unmounted if desired. */
|
|
chdir("/");
|
|
|
|
/* ignore SIGPIPE */
|
|
signal(SIGPIPE, SIG_IGN);
|
|
|
|
/* Start listening for a socket, unless started from inetd. */
|
|
if (inetd_flag) {
|
|
int s1;
|
|
s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
|
|
dup(s1);
|
|
sock_in = dup(0);
|
|
sock_out = dup(1);
|
|
startup_pipe = -1;
|
|
/*
|
|
* We intentionally do not close the descriptors 0, 1, and 2
|
|
* as our code for setting the descriptors won\'t work if
|
|
* ttyfd happens to be one of those.
|
|
*/
|
|
debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
|
|
if (options.protocol & SSH_PROTO_1)
|
|
generate_ephemeral_server_key();
|
|
} else {
|
|
for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
|
|
if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
|
|
continue;
|
|
if (num_listen_socks >= MAX_LISTEN_SOCKS)
|
|
fatal("Too many listen sockets. "
|
|
"Enlarge MAX_LISTEN_SOCKS");
|
|
if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
|
|
ntop, sizeof(ntop), strport, sizeof(strport),
|
|
NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
|
|
error("getnameinfo failed");
|
|
continue;
|
|
}
|
|
/* Create socket for listening. */
|
|
listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
|
|
if (listen_sock < 0) {
|
|
/* kernel may not support ipv6 */
|
|
verbose("socket: %.100s", strerror(errno));
|
|
continue;
|
|
}
|
|
if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
|
|
error("listen_sock O_NONBLOCK: %s", strerror(errno));
|
|
close(listen_sock);
|
|
continue;
|
|
}
|
|
/*
|
|
* Set socket options.
|
|
* Allow local port reuse in TIME_WAIT.
|
|
*/
|
|
if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
|
|
&on, sizeof(on)) == -1)
|
|
error("setsockopt SO_REUSEADDR: %s", strerror(errno));
|
|
|
|
debug("Bind to port %s on %s.", strport, ntop);
|
|
|
|
/* Bind the socket to the desired port. */
|
|
if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
|
|
if (!ai->ai_next)
|
|
error("Bind to port %s on %s failed: %.200s.",
|
|
strport, ntop, strerror(errno));
|
|
close(listen_sock);
|
|
continue;
|
|
}
|
|
listen_socks[num_listen_socks] = listen_sock;
|
|
num_listen_socks++;
|
|
|
|
/* Start listening on the port. */
|
|
log("Server listening on %s port %s.", ntop, strport);
|
|
if (listen(listen_sock, 5) < 0)
|
|
fatal("listen: %.100s", strerror(errno));
|
|
|
|
}
|
|
freeaddrinfo(options.listen_addrs);
|
|
|
|
if (!num_listen_socks)
|
|
fatal("Cannot bind any address.");
|
|
|
|
if (options.protocol & SSH_PROTO_1)
|
|
generate_ephemeral_server_key();
|
|
|
|
/*
|
|
* Arrange to restart on SIGHUP. The handler needs
|
|
* listen_sock.
|
|
*/
|
|
signal(SIGHUP, sighup_handler);
|
|
|
|
signal(SIGTERM, sigterm_handler);
|
|
signal(SIGQUIT, sigterm_handler);
|
|
|
|
/* Arrange SIGCHLD to be caught. */
|
|
signal(SIGCHLD, main_sigchld_handler);
|
|
|
|
/* Write out the pid file after the sigterm handler is setup */
|
|
if (!debug_flag) {
|
|
/*
|
|
* Record our pid in /var/run/sshd.pid to make it
|
|
* easier to kill the correct sshd. We don't want to
|
|
* do this before the bind above because the bind will
|
|
* fail if there already is a daemon, and this will
|
|
* overwrite any old pid in the file.
|
|
*/
|
|
f = fopen(options.pid_file, "wb");
|
|
if (f) {
|
|
fprintf(f, "%ld\n", (long) getpid());
|
|
fclose(f);
|
|
}
|
|
}
|
|
|
|
/* setup fd set for listen */
|
|
fdset = NULL;
|
|
maxfd = 0;
|
|
for (i = 0; i < num_listen_socks; i++)
|
|
if (listen_socks[i] > maxfd)
|
|
maxfd = listen_socks[i];
|
|
/* pipes connected to unauthenticated childs */
|
|
startup_pipes = xmalloc(options.max_startups * sizeof(int));
|
|
for (i = 0; i < options.max_startups; i++)
|
|
startup_pipes[i] = -1;
|
|
|
|
/*
|
|
* Stay listening for connections until the system crashes or
|
|
* the daemon is killed with a signal.
|
|
*/
|
|
for (;;) {
|
|
if (received_sighup)
|
|
sighup_restart();
|
|
if (fdset != NULL)
|
|
xfree(fdset);
|
|
fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
|
|
fdset = (fd_set *)xmalloc(fdsetsz);
|
|
memset(fdset, 0, fdsetsz);
|
|
|
|
for (i = 0; i < num_listen_socks; i++)
|
|
FD_SET(listen_socks[i], fdset);
|
|
for (i = 0; i < options.max_startups; i++)
|
|
if (startup_pipes[i] != -1)
|
|
FD_SET(startup_pipes[i], fdset);
|
|
|
|
/* Wait in select until there is a connection. */
|
|
ret = select(maxfd+1, fdset, NULL, NULL, NULL);
|
|
if (ret < 0 && errno != EINTR)
|
|
error("select: %.100s", strerror(errno));
|
|
if (received_sigterm) {
|
|
log("Received signal %d; terminating.",
|
|
(int) received_sigterm);
|
|
close_listen_socks();
|
|
unlink(options.pid_file);
|
|
exit(255);
|
|
}
|
|
if (key_used && key_do_regen) {
|
|
generate_ephemeral_server_key();
|
|
key_used = 0;
|
|
key_do_regen = 0;
|
|
}
|
|
if (ret < 0)
|
|
continue;
|
|
|
|
for (i = 0; i < options.max_startups; i++)
|
|
if (startup_pipes[i] != -1 &&
|
|
FD_ISSET(startup_pipes[i], fdset)) {
|
|
/*
|
|
* the read end of the pipe is ready
|
|
* if the child has closed the pipe
|
|
* after successful authentication
|
|
* or if the child has died
|
|
*/
|
|
close(startup_pipes[i]);
|
|
startup_pipes[i] = -1;
|
|
startups--;
|
|
}
|
|
for (i = 0; i < num_listen_socks; i++) {
|
|
if (!FD_ISSET(listen_socks[i], fdset))
|
|
continue;
|
|
fromlen = sizeof(from);
|
|
newsock = accept(listen_socks[i], (struct sockaddr *)&from,
|
|
&fromlen);
|
|
if (newsock < 0) {
|
|
if (errno != EINTR && errno != EWOULDBLOCK)
|
|
error("accept: %.100s", strerror(errno));
|
|
continue;
|
|
}
|
|
if (fcntl(newsock, F_SETFL, 0) < 0) {
|
|
error("newsock del O_NONBLOCK: %s", strerror(errno));
|
|
close(newsock);
|
|
continue;
|
|
}
|
|
if (drop_connection(startups) == 1) {
|
|
debug("drop connection #%d", startups);
|
|
close(newsock);
|
|
continue;
|
|
}
|
|
if (pipe(startup_p) == -1) {
|
|
close(newsock);
|
|
continue;
|
|
}
|
|
|
|
for (j = 0; j < options.max_startups; j++)
|
|
if (startup_pipes[j] == -1) {
|
|
startup_pipes[j] = startup_p[0];
|
|
if (maxfd < startup_p[0])
|
|
maxfd = startup_p[0];
|
|
startups++;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Got connection. Fork a child to handle it, unless
|
|
* we are in debugging mode.
|
|
*/
|
|
if (debug_flag) {
|
|
/*
|
|
* In debugging mode. Close the listening
|
|
* socket, and start processing the
|
|
* connection without forking.
|
|
*/
|
|
debug("Server will not fork when running in debugging mode.");
|
|
close_listen_socks();
|
|
sock_in = newsock;
|
|
sock_out = newsock;
|
|
startup_pipe = -1;
|
|
pid = getpid();
|
|
break;
|
|
} else {
|
|
/*
|
|
* Normal production daemon. Fork, and have
|
|
* the child process the connection. The
|
|
* parent continues listening.
|
|
*/
|
|
if ((pid = fork()) == 0) {
|
|
/*
|
|
* Child. Close the listening and max_startup
|
|
* sockets. Start using the accepted socket.
|
|
* Reinitialize logging (since our pid has
|
|
* changed). We break out of the loop to handle
|
|
* the connection.
|
|
*/
|
|
startup_pipe = startup_p[1];
|
|
close_startup_pipes();
|
|
close_listen_socks();
|
|
sock_in = newsock;
|
|
sock_out = newsock;
|
|
log_init(__progname, options.log_level, options.log_facility, log_stderr);
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* Parent. Stay in the loop. */
|
|
if (pid < 0)
|
|
error("fork: %.100s", strerror(errno));
|
|
else
|
|
debug("Forked child %ld.", (long)pid);
|
|
|
|
close(startup_p[1]);
|
|
|
|
/* Mark that the key has been used (it was "given" to the child). */
|
|
if ((options.protocol & SSH_PROTO_1) &&
|
|
key_used == 0) {
|
|
/* Schedule server key regeneration alarm. */
|
|
signal(SIGALRM, key_regeneration_alarm);
|
|
alarm(options.key_regeneration_time);
|
|
key_used = 1;
|
|
}
|
|
|
|
arc4random_stir();
|
|
|
|
/* Close the new socket (the child is now taking care of it). */
|
|
close(newsock);
|
|
}
|
|
/* child process check (or debug mode) */
|
|
if (num_listen_socks < 0)
|
|
break;
|
|
}
|
|
}
|
|
|
|
/* This is the child processing a new connection. */
|
|
|
|
/*
|
|
* Create a new session and process group since the 4.4BSD
|
|
* setlogin() affects the entire process group. We don't
|
|
* want the child to be able to affect the parent.
|
|
*/
|
|
#if 0
|
|
/* XXX: this breaks Solaris */
|
|
if (!debug_flag && !inetd_flag && setsid() < 0)
|
|
error("setsid: %.100s", strerror(errno));
|
|
#endif
|
|
|
|
/*
|
|
* Disable the key regeneration alarm. We will not regenerate the
|
|
* key since we are no longer in a position to give it to anyone. We
|
|
* will not restart on SIGHUP since it no longer makes sense.
|
|
*/
|
|
alarm(0);
|
|
signal(SIGALRM, SIG_DFL);
|
|
signal(SIGHUP, SIG_DFL);
|
|
signal(SIGTERM, SIG_DFL);
|
|
signal(SIGQUIT, SIG_DFL);
|
|
signal(SIGCHLD, SIG_DFL);
|
|
signal(SIGINT, SIG_DFL);
|
|
|
|
/* Set keepalives if requested. */
|
|
if (options.keepalives &&
|
|
setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
|
|
sizeof(on)) < 0)
|
|
error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
|
|
|
|
/*
|
|
* Register our connection. This turns encryption off because we do
|
|
* not have a key.
|
|
*/
|
|
packet_set_connection(sock_in, sock_out);
|
|
|
|
remote_port = get_remote_port();
|
|
remote_ip = get_remote_ipaddr();
|
|
|
|
#ifdef LIBWRAP
|
|
/* Check whether logins are denied from this host. */
|
|
{
|
|
struct request_info req;
|
|
|
|
request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
|
|
fromhost(&req);
|
|
|
|
if (!hosts_access(&req)) {
|
|
debug("Connection refused by tcp wrapper");
|
|
refuse(&req);
|
|
/* NOTREACHED */
|
|
fatal("libwrap refuse returns");
|
|
}
|
|
}
|
|
#endif /* LIBWRAP */
|
|
|
|
/* Log the connection. */
|
|
verbose("Connection from %.500s port %d", remote_ip, remote_port);
|
|
|
|
/*
|
|
* We don\'t want to listen forever unless the other side
|
|
* successfully authenticates itself. So we set up an alarm which is
|
|
* cleared after successful authentication. A limit of zero
|
|
* indicates no limit. Note that we don\'t set the alarm in debugging
|
|
* mode; it is just annoying to have the server exit just when you
|
|
* are about to discover the bug.
|
|
*/
|
|
signal(SIGALRM, grace_alarm_handler);
|
|
if (!debug_flag)
|
|
alarm(options.login_grace_time);
|
|
|
|
sshd_exchange_identification(sock_in, sock_out);
|
|
/*
|
|
* Check that the connection comes from a privileged port.
|
|
* Rhosts-Authentication only makes sense from privileged
|
|
* programs. Of course, if the intruder has root access on his local
|
|
* machine, he can connect from any port. So do not use these
|
|
* authentication methods from machines that you do not trust.
|
|
*/
|
|
if (options.rhosts_authentication &&
|
|
(remote_port >= IPPORT_RESERVED ||
|
|
remote_port < IPPORT_RESERVED / 2)) {
|
|
debug("Rhosts Authentication disabled, "
|
|
"originating port %d not trusted.", remote_port);
|
|
options.rhosts_authentication = 0;
|
|
}
|
|
#if defined(KRB4) && !defined(KRB5)
|
|
if (!packet_connection_is_ipv4() &&
|
|
options.kerberos_authentication) {
|
|
debug("Kerberos Authentication disabled, only available for IPv4.");
|
|
options.kerberos_authentication = 0;
|
|
}
|
|
#endif /* KRB4 && !KRB5 */
|
|
#ifdef AFS
|
|
/* If machine has AFS, set process authentication group. */
|
|
if (k_hasafs()) {
|
|
k_setpag();
|
|
k_unlog();
|
|
}
|
|
#endif /* AFS */
|
|
|
|
packet_set_nonblocking();
|
|
|
|
if (use_privsep)
|
|
if ((authctxt = privsep_preauth()) != NULL)
|
|
goto authenticated;
|
|
|
|
/* perform the key exchange */
|
|
/* authenticate user and start session */
|
|
if (compat20) {
|
|
do_ssh2_kex();
|
|
authctxt = do_authentication2();
|
|
} else {
|
|
do_ssh1_kex();
|
|
authctxt = do_authentication();
|
|
}
|
|
/*
|
|
* If we use privilege separation, the unprivileged child transfers
|
|
* the current keystate and exits
|
|
*/
|
|
if (use_privsep) {
|
|
mm_send_keystate(pmonitor);
|
|
exit(0);
|
|
}
|
|
|
|
authenticated:
|
|
/*
|
|
* In privilege separation, we fork another child and prepare
|
|
* file descriptor passing.
|
|
*/
|
|
if (use_privsep) {
|
|
privsep_postauth(authctxt);
|
|
/* the monitor process [priv] will not return */
|
|
if (!compat20)
|
|
destroy_sensitive_data();
|
|
}
|
|
|
|
/* Perform session preparation. */
|
|
do_authenticated(authctxt);
|
|
|
|
/* The connection has been terminated. */
|
|
verbose("Closing connection to %.100s", remote_ip);
|
|
|
|
#ifdef USE_PAM
|
|
finish_pam();
|
|
#endif /* USE_PAM */
|
|
|
|
packet_close();
|
|
|
|
if (use_privsep)
|
|
mm_terminate();
|
|
|
|
exit(0);
|
|
}
|
|
|
|
/*
|
|
* Decrypt session_key_int using our private server key and private host key
|
|
* (key with larger modulus first).
|
|
*/
|
|
int
|
|
ssh1_session_key(BIGNUM *session_key_int)
|
|
{
|
|
int rsafail = 0;
|
|
|
|
if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
|
|
/* 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",
|
|
get_remote_ipaddr(),
|
|
BN_num_bits(sensitive_data.server_key->rsa->n),
|
|
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
|
|
SSH_KEY_BITS_RESERVED);
|
|
}
|
|
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) <
|
|
BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
|
|
fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
|
|
get_remote_ipaddr(),
|
|
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
|
|
BN_num_bits(sensitive_data.server_key->rsa->n),
|
|
SSH_KEY_BITS_RESERVED);
|
|
}
|
|
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++;
|
|
}
|
|
return (rsafail);
|
|
}
|
|
/*
|
|
* SSH1 key exchange
|
|
*/
|
|
static void
|
|
do_ssh1_kex(void)
|
|
{
|
|
int i, len;
|
|
int rsafail = 0;
|
|
BIGNUM *session_key_int;
|
|
u_char session_key[SSH_SESSION_KEY_LENGTH];
|
|
u_char cookie[8];
|
|
u_int cipher_type, auth_mask, protocol_flags;
|
|
u_int32_t rnd = 0;
|
|
|
|
/*
|
|
* Generate check bytes that the client must send back in the user
|
|
* packet in order for it to be accepted; this is used to defy ip
|
|
* spoofing attacks. Note that this only works against somebody
|
|
* doing IP spoofing from a remote machine; any machine on the local
|
|
* network can still see outgoing packets and catch the random
|
|
* cookie. This only affects rhosts authentication, and this is one
|
|
* of the reasons why it is inherently insecure.
|
|
*/
|
|
for (i = 0; i < 8; i++) {
|
|
if (i % 4 == 0)
|
|
rnd = arc4random();
|
|
cookie[i] = rnd & 0xff;
|
|
rnd >>= 8;
|
|
}
|
|
|
|
/*
|
|
* Send our public key. We include in the packet 64 bits of random
|
|
* data that must be matched in the reply in order to prevent IP
|
|
* spoofing.
|
|
*/
|
|
packet_start(SSH_SMSG_PUBLIC_KEY);
|
|
for (i = 0; i < 8; i++)
|
|
packet_put_char(cookie[i]);
|
|
|
|
/* Store our public server RSA key. */
|
|
packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
|
|
packet_put_bignum(sensitive_data.server_key->rsa->e);
|
|
packet_put_bignum(sensitive_data.server_key->rsa->n);
|
|
|
|
/* Store our public host RSA key. */
|
|
packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
|
|
packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
|
|
packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
|
|
|
|
/* Put protocol flags. */
|
|
packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
|
|
|
|
/* Declare which ciphers we support. */
|
|
packet_put_int(cipher_mask_ssh1(0));
|
|
|
|
/* Declare supported authentication types. */
|
|
auth_mask = 0;
|
|
if (options.rhosts_authentication)
|
|
auth_mask |= 1 << SSH_AUTH_RHOSTS;
|
|
if (options.rhosts_rsa_authentication)
|
|
auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
|
|
if (options.rsa_authentication)
|
|
auth_mask |= 1 << SSH_AUTH_RSA;
|
|
#if defined(KRB4) || defined(KRB5)
|
|
if (options.kerberos_authentication)
|
|
auth_mask |= 1 << SSH_AUTH_KERBEROS;
|
|
#endif
|
|
#if defined(AFS) || defined(KRB5)
|
|
if (options.kerberos_tgt_passing)
|
|
auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
|
|
#endif
|
|
#ifdef AFS
|
|
if (options.afs_token_passing)
|
|
auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
|
|
#endif
|
|
if (options.challenge_response_authentication == 1)
|
|
auth_mask |= 1 << SSH_AUTH_TIS;
|
|
if (options.password_authentication)
|
|
auth_mask |= 1 << SSH_AUTH_PASSWORD;
|
|
packet_put_int(auth_mask);
|
|
|
|
/* Send the packet and wait for it to be sent. */
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
debug("Sent %d bit server key and %d bit host key.",
|
|
BN_num_bits(sensitive_data.server_key->rsa->n),
|
|
BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
|
|
|
|
/* Read clients reply (cipher type and session key). */
|
|
packet_read_expect(SSH_CMSG_SESSION_KEY);
|
|
|
|
/* Get cipher type and check whether we accept this. */
|
|
cipher_type = packet_get_char();
|
|
|
|
if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
|
|
packet_disconnect("Warning: client selects unsupported cipher.");
|
|
|
|
/* Get check bytes from the packet. These must match those we
|
|
sent earlier with the public key packet. */
|
|
for (i = 0; i < 8; i++)
|
|
if (cookie[i] != packet_get_char())
|
|
packet_disconnect("IP Spoofing check bytes do not match.");
|
|
|
|
debug("Encryption type: %.200s", cipher_name(cipher_type));
|
|
|
|
/* Get the encrypted integer. */
|
|
if ((session_key_int = BN_new()) == NULL)
|
|
fatal("do_ssh1_kex: BN_new failed");
|
|
packet_get_bignum(session_key_int);
|
|
|
|
protocol_flags = packet_get_int();
|
|
packet_set_protocol_flags(protocol_flags);
|
|
packet_check_eom();
|
|
|
|
/* Decrypt session_key_int using host/server keys */
|
|
rsafail = PRIVSEP(ssh1_session_key(session_key_int));
|
|
|
|
/*
|
|
* Extract session key from the decrypted integer. The key is in the
|
|
* least significant 256 bits of the integer; the first byte of the
|
|
* key is in the highest bits.
|
|
*/
|
|
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) %lu",
|
|
get_remote_ipaddr(), len, (u_long)sizeof(session_key));
|
|
rsafail++;
|
|
} else {
|
|
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);
|
|
u_char *buf = xmalloc(bytes);
|
|
MD5_CTX md;
|
|
|
|
log("do_connection: generating a fake encryption key");
|
|
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);
|
|
for (i = 0; i < 16; i++)
|
|
session_id[i] = session_key[i] ^ session_key[i + 16];
|
|
}
|
|
/* Destroy the private and public keys. No longer. */
|
|
destroy_sensitive_data();
|
|
|
|
if (use_privsep)
|
|
mm_ssh1_session_id(session_id);
|
|
|
|
/* Destroy the decrypted integer. It is no longer needed. */
|
|
BN_clear_free(session_key_int);
|
|
|
|
/* Set the session key. From this on all communications will be encrypted. */
|
|
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
|
|
|
|
/* Destroy our copy of the session key. It is no longer needed. */
|
|
memset(session_key, 0, sizeof(session_key));
|
|
|
|
debug("Received session key; encryption turned on.");
|
|
|
|
/* Send an acknowledgment packet. Note that this packet is sent encrypted. */
|
|
packet_start(SSH_SMSG_SUCCESS);
|
|
packet_send();
|
|
packet_write_wait();
|
|
}
|
|
|
|
/*
|
|
* SSH2 key exchange: diffie-hellman-group1-sha1
|
|
*/
|
|
static void
|
|
do_ssh2_kex(void)
|
|
{
|
|
Kex *kex;
|
|
|
|
if (options.ciphers != NULL) {
|
|
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
|
|
myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
|
|
}
|
|
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
|
|
compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
|
|
myproposal[PROPOSAL_ENC_ALGS_STOC] =
|
|
compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
|
|
|
|
if (options.macs != NULL) {
|
|
myproposal[PROPOSAL_MAC_ALGS_CTOS] =
|
|
myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
|
|
}
|
|
if (!options.compression) {
|
|
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
|
|
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
|
|
}
|
|
myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
|
|
|
|
/* start key exchange */
|
|
kex = kex_setup(myproposal);
|
|
kex->server = 1;
|
|
kex->client_version_string=client_version_string;
|
|
kex->server_version_string=server_version_string;
|
|
kex->load_host_key=&get_hostkey_by_type;
|
|
kex->host_key_index=&get_hostkey_index;
|
|
|
|
xxx_kex = kex;
|
|
|
|
dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
|
|
|
|
session_id2 = kex->session_id;
|
|
session_id2_len = kex->session_id_len;
|
|
|
|
#ifdef DEBUG_KEXDH
|
|
/* send 1st encrypted/maced/compressed message */
|
|
packet_start(SSH2_MSG_IGNORE);
|
|
packet_put_cstring("markus");
|
|
packet_send();
|
|
packet_write_wait();
|
|
#endif
|
|
debug("KEX done");
|
|
}
|