path: root/other/ssharp/sshconnect.c

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Code to connect to a remote host, and to perform the client side of the
 * login (authentication) dialog.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: sshconnect.c,v 1.104 2001/04/12 19:15:25 markus Exp $");

#include <openssl/bn.h>

#include "ssh.h"
#include "xmalloc.h"
#include "rsa.h"
#include "buffer.h"
#include "packet.h"
#include "uidswap.h"
#include "compat.h"
#include "key.h"
#include "sshconnect.h"
#include "hostfile.h"
#include "log.h"
#include "readconf.h"
#include "atomicio.h"
#include "misc.h"
#include "ssharp.h"

char *client_version_string = NULL;
char *server_version_string = NULL;

extern Options options;
extern char *__progname;

/* AF_UNSPEC or AF_INET or AF_INET6 */
extern int IPv4or6;

/*
 * Connect to the given ssh server using a proxy command.
 */
int
ssh_proxy_connect(const char *host, u_short port,
		  const char *proxy_command)
{
	Buffer command;
	const char *cp;
	char *command_string;
	int pin[2], pout[2];
	pid_t pid;
	char strport[NI_MAXSERV];

	/* Convert the port number into a string. */
	snprintf(strport, sizeof strport, "%hu", port);

	/* Build the final command string in the buffer by making the
	   appropriate substitutions to the given proxy command. */
	buffer_init(&command);
	for (cp = proxy_command; *cp; cp++) {
		if (cp[0] == '%' && cp[1] == '%') {
			buffer_append(&command, "%", 1);
			cp++;
			continue;
		}
		if (cp[0] == '%' && cp[1] == 'h') {
			buffer_append(&command, host, strlen(host));
			cp++;
			continue;
		}
		if (cp[0] == '%' && cp[1] == 'p') {
			buffer_append(&command, strport, strlen(strport));
			cp++;
			continue;
		}
		buffer_append(&command, cp, 1);
	}
	buffer_append(&command, "\0", 1);

	/* Get the final command string. */
	command_string = buffer_ptr(&command);

	/* Create pipes for communicating with the proxy. */
	if (pipe(pin) < 0 || pipe(pout) < 0)
		fatal("Could not create pipes to communicate with the proxy: %.100s",
		      strerror(errno));

	debug("Executing proxy command: %.500s", command_string);

	/* Fork and execute the proxy command. */
	if ((pid = fork()) == 0) {
		char *argv[10];


		/* Redirect stdin and stdout. */
		close(pin[1]);
		if (pin[0] != 0) {
			if (dup2(pin[0], 0) < 0)
				perror("dup2 stdin");
			close(pin[0]);
		}
		close(pout[0]);
		if (dup2(pout[1], 1) < 0)
			perror("dup2 stdout");
		/* Cannot be 1 because pin allocated two descriptors. */
		close(pout[1]);

		/* Stderr is left as it is so that error messages get
		   printed on the user's terminal. */
		argv[0] = _PATH_BSHELL;
		argv[1] = "-c";
		argv[2] = command_string;
		argv[3] = NULL;

		/* Execute the proxy command.  Note that we gave up any
		   extra privileges above. */
		execv(argv[0], argv);
		perror(argv[0]);
		exit(1);
	}
	/* Parent. */
	if (pid < 0)
		fatal("fork failed: %.100s", strerror(errno));

	/* Close child side of the descriptors. */
	close(pin[0]);
	close(pout[1]);

	/* Free the command name. */
	buffer_free(&command);

	/* Set the connection file descriptors. */
	packet_set_connection(pout[0], pin[1]);

	return 1;
}


/*
 * Creates a (possibly privileged) socket for use as the ssh connection.
 */
int
ssh_create_socket(int family)
{
	int sock = socket(family, SOCK_STREAM, 0);
	return sock;
}

/*
 * Opens a TCP/IP connection to the remote server on the given host.
 * The address of the remote host will be returned in hostaddr.
 * If port is 0, the default port will be used.  If anonymous is zero,
 * a privileged port will be allocated to make the connection.
 * This requires super-user privileges if anonymous is false.
 * Connection_attempts specifies the maximum number of tries (one per
 * second).  If proxy_command is non-NULL, it specifies the command (with %h
 * and %p substituted for host and port, respectively) to use to contact
 * the daemon.
 */
int
ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
	    u_short port, int connection_attempts,
	    int anonymous,
	    const char *proxy_command)
{
	int gaierr;
	int on = 1;
	int sock = -1, attempt;
	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
	struct addrinfo hints, *ai, *aitop;
	struct linger linger;
	struct servent *sp;

	debug("ssh_connect: getuid %u geteuid %u anon %d",
	      (u_int) getuid(), (u_int) geteuid(), anonymous);

	/* Get default port if port has not been set. */
	if (port == 0) {
		sp = getservbyname(SSH_SERVICE_NAME, "tcp");
		if (sp)
			port = ntohs(sp->s_port);
		else
			port = SSH_DEFAULT_PORT;
	}
	/* If a proxy command is given, connect using it. */
	if (proxy_command != NULL)
		return ssh_proxy_connect(host, port, proxy_command);

	/* No proxy command. */

	memset(&hints, 0, sizeof(hints));
	hints.ai_family = IPv4or6;
	hints.ai_socktype = SOCK_STREAM;
	snprintf(strport, sizeof strport, "%d", port);
	if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
		fatal("%s: %.100s: %s", __progname, host,
		    gai_strerror(gaierr));

	/*
	 * Try to connect several times.  On some machines, the first time
	 * will sometimes fail.  In general socket code appears to behave
	 * quite magically on many machines.
	 */
	for (attempt = 0; attempt < connection_attempts; attempt++) {
		if (attempt > 0)
			debug("Trying again...");

		/* Loop through addresses for this host, and try each one in
		   sequence until the connection succeeds. */
		for (ai = aitop; ai; ai = ai->ai_next) {
			if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
				continue;
			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
			    ntop, sizeof(ntop), strport, sizeof(strport),
			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
				error("ssh_connect: getnameinfo failed");
				continue;
			}
			debug("Connecting to %.200s [%.100s] port %s.",
				host, ntop, strport);


			if ((sock = socket_connect_b(ai->ai_addr, ai->ai_addrlen, SSHARP_MINPORT)) >= 0) {
				/* Successful connection. */
				memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
				break;
			} else {
				debug("connect: %.100s", strerror(errno));
				/*
				 * Close the failed socket; there appear to
				 * be some problems when reusing a socket for
				 * which connect() has already returned an
				 * error.
				 */
				shutdown(sock, SHUT_RDWR);
				close(sock);
			}
		}
		if (ai)
			break;	/* Successful connection. */

		/* Sleep a moment before retrying. */
		sleep(1);
	}

	freeaddrinfo(aitop);

	/* Return failure if we didn't get a successful connection. */
	if (attempt >= connection_attempts)
		return 0;

	debug("Connection established.");

	/*
	 * Set socket options.  We would like the socket to disappear as soon
	 * as it has been closed for whatever reason.
	 */
	/* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
	linger.l_onoff = 1;
	linger.l_linger = 5;
	setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));

	/* Set keepalives if requested. */
	if (options.keepalives &&
	    setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
	    sizeof(on)) < 0)
		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));

	/* Set the connection. */
	packet_set_connection(sock, sock);

	return 1;
}

/*
 * Waits for the server identification string, and sends our own
 * identification string.
 */
void
ssh_exchange_identification(void)
{
	char buf[256], remote_version[256];	/* must be same size! */
	int remote_major, remote_minor, i, mismatch;
	int connection_in = packet_get_connection_in();
	int connection_out = packet_get_connection_out();
	int minor1 = PROTOCOL_MINOR_1;

	/* Read other side\'s version identification. */
	for (;;) {
		for (i = 0; i < sizeof(buf) - 1; i++) {
			int len = atomicio(read, connection_in, &buf[i], 1);
			if (len < 0)
				fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
			if (len != 1)
				fatal("ssh_exchange_identification: Connection closed by remote host");
			if (buf[i] == '\r') {
				buf[i] = '\n';
				buf[i + 1] = 0;
				continue;		/**XXX wait for \n */
			}
			if (buf[i] == '\n') {
				buf[i + 1] = 0;
				break;
			}
		}
		buf[sizeof(buf) - 1] = 0;
		if (strncmp(buf, "SSH-", 4) == 0)
			break;
		debug("ssh_exchange_identification: %s", buf);
	}
	server_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(server_version_string, "SSH-%d.%d-%[^\n]\n",
	    &remote_major, &remote_minor, remote_version) != 3)
		fatal("Bad remote protocol version identification: '%.100s'", buf);
	debug("Remote protocol version %d.%d, remote software version %.100s",
	      remote_major, remote_minor, remote_version);

	compat_datafellows(remote_version);
	mismatch = 0;

	switch(remote_major) {
	case 1:
		if (remote_minor == 99 &&
		    (options.protocol & SSH_PROTO_2) &&
		    !(options.protocol & SSH_PROTO_1_PREFERRED)) {
			enable_compat20();
			break;
		}
		if (!(options.protocol & SSH_PROTO_1)) {
			mismatch = 1;
			break;
		}
		if (remote_minor < 3) {
			fatal("Remote machine has too old SSH software version.");
		} else if (remote_minor == 3 || remote_minor == 4) {
			/* We speak 1.3, too. */
			enable_compat13();
			minor1 = 3;
			if (options.forward_agent) {
				log("Agent forwarding disabled for protocol 1.3");
				options.forward_agent = 0;
			}
		}
		break;
	case 2:
		if (options.protocol & SSH_PROTO_2) {
			enable_compat20();
			break;
		}
		/* FALLTHROUGH */
	default:
		mismatch = 1;
		break;
	}
	if (mismatch)
		fatal("Protocol major versions differ: %d vs. %d",
		    (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
		    remote_major);
	if (compat20)
		packet_set_ssh2_format();
	/* Send our own protocol version identification. */
	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
	    compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
	    compat20 ? PROTOCOL_MINOR_2 : minor1,
	    SSH_VERSION);
	if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
		fatal("write: %.100s", strerror(errno));
	client_version_string = xstrdup(buf);
	chop(client_version_string);
	chop(server_version_string);
	debug("Local version string %.100s", client_version_string);
}

/* defaults to 'no' */
int
read_yes_or_no(const char *prompt, int defval)
{
	char buf[1024];
	FILE *f;
	int retval = -1;

	if (options.batch_mode)
		return 0;

	if (isatty(STDIN_FILENO))
		f = stdin;
	else
		f = fopen(_PATH_TTY, "rw");

	if (f == NULL)
		return 0;

	fflush(stdout);

	while (1) {
		fprintf(stderr, "%s", prompt);
		if (fgets(buf, sizeof(buf), f) == NULL) {
			/* Print a newline (the prompt probably didn\'t have one). */
			fprintf(stderr, "\n");
			strlcpy(buf, "no", sizeof buf);
		}
		/* Remove newline from response. */
		if (strchr(buf, '\n'))
			*strchr(buf, '\n') = 0;

		if (buf[0] == 0)
			retval = defval;
		if (strcmp(buf, "yes") == 0)
			retval = 1;
		else if (strcmp(buf, "no") == 0)
			retval = 0;
		else
			fprintf(stderr, "Please type 'yes' or 'no'.\n");

		if (retval != -1) {
			if (f != stdin)
				fclose(f);
			return retval;
		}
	}
}

/*
 * check whether the supplied host key is valid, return only if ok.
 */

void
check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
	const char *user_hostfile, const char *system_hostfile)
{
	/* SSHARP: dummy */
}

/*
 * Starts a dialog with the server, and authenticates the current user on the
 * server.  This does not need any extra privileges.  The basic connection
 * to the server must already have been established before this is called.
 * If login fails, this function prints an error and never returns.
 * This function does not require super-user privileges.
 */
void
ssh_login(Key **keys, int nkeys, const char *orighost,
    struct sockaddr *hostaddr, char *login, char *pass)
{
	char *host, *cp;

	/* Convert the user-supplied hostname into all lowercase. */
	host = xstrdup(orighost);
	for (cp = host; *cp; cp++)
		if (isupper(*cp))
			*cp = tolower(*cp);

	/* Exchange protocol version identification strings with the server. */
	ssh_exchange_identification();

	/* Put the connection into non-blocking mode. */
	packet_set_nonblocking();

	/* key exchange */
	/* authenticate user */
	if (compat20) {
		ssh_kex2(host, hostaddr);
		ssh_userauth2(login, pass, host, keys, nkeys);
	} else {
		ssh_kex(host, hostaddr);
		ssh_userauth1(login, pass, host, keys, nkeys);
	}
}

void
ssh_put_password(char *password)
{
	int size;
	char *padded;

	if (datafellows & SSH_BUG_PASSWORDPAD) {
		packet_put_string(password, strlen(password));
		return;
	}
	size = roundup(strlen(password) + 1, 32);
	padded = xmalloc(size);
	memset(padded, 0, size);
	strlcpy(padded, password, size);
	packet_put_string(padded, size);
	memset(padded, 0, size);
	xfree(padded);
}