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openssh/sshconnect.c
Darren Tucker edeb1f7449 - markus@cvs.openbsd.org 2003/06/29 12:44:38 
[sshconnect.c]
     memset 0, not \0; andrushock@korovino.net
2003-07-03 13:48:04 +10:00

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/*
* 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 1.147 2003/06/29 12:44:38 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 "readpass.h"
#ifdef DNS
#include "dns.h"
#endif
char *client_version_string = NULL;
char *server_version_string = NULL;
#ifdef DNS
int verified_host_key_dns = 0;
#endif
/* import */
extern Options options;
extern char *__progname;
extern uid_t original_real_uid;
extern uid_t original_effective_uid;
extern pid_t proxy_command_pid;
#ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */
#define INET6_ADDRSTRLEN 46
#endif
static int show_other_keys(const char *, Key *);
/*
* Connect to the given ssh server using a proxy command.
*/
static 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.
*
* Use "exec" to avoid "sh -c" processes on some platforms
* (e.g. Solaris)
*/
buffer_init(&command);
buffer_append(&command, "exec ", 5);
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];
/* Child. Permanently give up superuser privileges. */
seteuid(original_real_uid);
setuid(original_real_uid);
/* 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));
else
proxy_command_pid = pid; /* save pid to clean up later */
/* 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]);
/* Indicate OK return */
return 0;
}
/*
* Creates a (possibly privileged) socket for use as the ssh connection.
*/
static int
ssh_create_socket(int privileged, struct addrinfo *ai)
{
int sock, gaierr;
struct addrinfo hints, *res;
/*
* If we are running as root and want to connect to a privileged
* port, bind our own socket to a privileged port.
*/
if (privileged) {
int p = IPPORT_RESERVED - 1;
PRIV_START;
sock = rresvport_af(&p, ai->ai_family);
PRIV_END;
if (sock < 0)
error("rresvport: af=%d %.100s", ai->ai_family,
strerror(errno));
else
debug("Allocated local port %d.", p);
return sock;
}
sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
if (sock < 0)
error("socket: %.100s", strerror(errno));
/* Bind the socket to an alternative local IP address */
if (options.bind_address == NULL)
return sock;
memset(&hints, 0, sizeof(hints));
hints.ai_family = ai->ai_family;
hints.ai_socktype = ai->ai_socktype;
hints.ai_protocol = ai->ai_protocol;
hints.ai_flags = AI_PASSIVE;
gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
if (gaierr) {
error("getaddrinfo: %s: %s", options.bind_address,
gai_strerror(gaierr));
close(sock);
return -1;
}
if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
error("bind: %s: %s", options.bind_address, strerror(errno));
close(sock);
freeaddrinfo(res);
return -1;
}
freeaddrinfo(res);
return sock;
}
static int
timeout_connect(int sockfd, const struct sockaddr *serv_addr,
socklen_t addrlen, int timeout)
{
fd_set *fdset;
struct timeval tv;
socklen_t optlen;
int fdsetsz, optval, rc, result = -1;
if (timeout <= 0)
return (connect(sockfd, serv_addr, addrlen));
if (fcntl(sockfd, F_SETFL, O_NONBLOCK) < 0)
return (-1);
rc = connect(sockfd, serv_addr, addrlen);
if (rc == 0)
return (0);
if (errno != EINPROGRESS)
return (-1);
fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask);
fdset = (fd_set *)xmalloc(fdsetsz);
memset(fdset, 0, fdsetsz);
FD_SET(sockfd, fdset);
tv.tv_sec = timeout;
tv.tv_usec = 0;
for(;;) {
rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
if (rc != -1 || errno != EINTR)
break;
}
switch(rc) {
case 0:
/* Timed out */
errno = ETIMEDOUT;
break;
case -1:
/* Select error */
debug("select: %s", strerror(errno));
break;
case 1:
/* Completed or failed */
optval = 0;
optlen = sizeof(optval);
if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
&optlen) == -1)
debug("getsockopt: %s", strerror(errno));
break;
if (optval != 0) {
errno = optval;
break;
}
result = 0;
break;
default:
/* Should not occur */
fatal("Bogus return (%d) from select()", rc);
}
xfree(fdset);
return (result);
}
/*
* 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 needpriv is true,
* a privileged port will be allocated to make the connection.
* This requires super-user privileges if needpriv is true.
* 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.
* Return values:
* 0 for OK
* ECONNREFUSED if we got a "Connection Refused" by the peer on any address
* ECONNABORTED if we failed without a "Connection refused"
* Suitable error messages for the connection failure will already have been
* printed.
*/
int
ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
u_short port, int family, int connection_attempts,
int needpriv, 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 servent *sp;
/*
* Did we get only other errors than "Connection refused" (which
* should block fallback to rsh and similar), or did we get at least
* one "Connection refused"?
*/
int full_failure = 1;
debug2("ssh_connect: needpriv %d", needpriv);
/* 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 = family;
hints.ai_socktype = SOCK_STREAM;
snprintf(strport, sizeof strport, "%u", 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; ;) {
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);
/* Create a socket for connecting. */
sock = ssh_create_socket(needpriv, ai);
if (sock < 0)
/* Any error is already output */
continue;
if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
options.connection_timeout) >= 0) {
/* Successful connection. */
memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
break;
} else {
if (errno == ECONNREFUSED)
full_failure = 0;
debug("connect to address %s port %s: %s",
ntop, strport, strerror(errno));
/*
* Close the failed socket; there appear to
* be some problems when reusing a socket for
* which connect() has already returned an
* error.
*/
close(sock);
}
}
if (ai)
break; /* Successful connection. */
attempt++;
if (attempt >= connection_attempts)
break;
/* Sleep a moment before retrying. */
sleep(1);
}
freeaddrinfo(aitop);
/* Return failure if we didn't get a successful connection. */
if (attempt >= connection_attempts) {
logit("ssh: connect to host %s port %s: %s",
host, strport, strerror(errno));
return full_failure ? ECONNABORTED : ECONNREFUSED;
}
debug("Connection established.");
/* 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 0;
}
/*
* Waits for the server identification string, and sends our own
* identification string.
*/
static 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) {
logit("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);
/* 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(vwrite, 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' */
static int
confirm(const char *prompt)
{
const char *msg, *again = "Please type 'yes' or 'no': ";
char *p;
int ret = -1;
if (options.batch_mode)
return 0;
for (msg = prompt;;msg = again) {
p = read_passphrase(msg, RP_ECHO);
if (p == NULL ||
(p[0] == '\0') || (p[0] == '\n') ||
strncasecmp(p, "no", 2) == 0)
ret = 0;
if (p && strncasecmp(p, "yes", 3) == 0)
ret = 1;
if (p)
xfree(p);
if (ret != -1)
return ret;
}
}
/*
* check whether the supplied host key is valid, return -1 if the key
* is not valid. the user_hostfile will not be updated if 'readonly' is true.
*/
static int
check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
int readonly, const char *user_hostfile, const char *system_hostfile)
{
Key *file_key;
char *type = key_type(host_key);
char *ip = NULL;
char hostline[1000], *hostp, *fp;
HostStatus host_status;
HostStatus ip_status;
int local = 0, host_ip_differ = 0;
int salen;
char ntop[NI_MAXHOST];
char msg[1024];
int len, host_line, ip_line;
const char *host_file = NULL, *ip_file = NULL;
/*
* Force accepting of the host key for loopback/localhost. The
* problem is that if the home directory is NFS-mounted to multiple
* machines, localhost will refer to a different machine in each of
* them, and the user will get bogus HOST_CHANGED warnings. This
* essentially disables host authentication for localhost; however,
* this is probably not a real problem.
*/
/** hostaddr == 0! */
switch (hostaddr->sa_family) {
case AF_INET:
local = (ntohl(((struct sockaddr_in *)hostaddr)->
sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
salen = sizeof(struct sockaddr_in);
break;
case AF_INET6:
local = IN6_IS_ADDR_LOOPBACK(
&(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
salen = sizeof(struct sockaddr_in6);
break;
default:
local = 0;
salen = sizeof(struct sockaddr_storage);
break;
}
if (options.no_host_authentication_for_localhost == 1 && local &&
options.host_key_alias == NULL) {
debug("Forcing accepting of host key for "
"loopback/localhost.");
return 0;
}
/*
* We don't have the remote ip-address for connections
* using a proxy command
*/
if (options.proxy_command == NULL) {
if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
NULL, 0, NI_NUMERICHOST) != 0)
fatal("check_host_key: getnameinfo failed");
ip = xstrdup(ntop);
} else {
ip = xstrdup("<no hostip for proxy command>");
}
/*
* Turn off check_host_ip if the connection is to localhost, via proxy
* command or if we don't have a hostname to compare with
*/
if (options.check_host_ip &&
(local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
options.check_host_ip = 0;
/*
* Allow the user to record the key under a different name. This is
* useful for ssh tunneling over forwarded connections or if you run
* multiple sshd's on different ports on the same machine.
*/
if (options.host_key_alias != NULL) {
host = options.host_key_alias;
debug("using hostkeyalias: %s", host);
}
/*
* Store the host key from the known host file in here so that we can
* compare it with the key for the IP address.
*/
file_key = key_new(host_key->type);
/*
* Check if the host key is present in the user\'s list of known
* hosts or in the systemwide list.
*/
host_file = user_hostfile;
host_status = check_host_in_hostfile(host_file, host, host_key,
file_key, &host_line);
if (host_status == HOST_NEW) {
host_file = system_hostfile;
host_status = check_host_in_hostfile(host_file, host, host_key,
file_key, &host_line);
}
/*
* Also perform check for the ip address, skip the check if we are
* localhost or the hostname was an ip address to begin with
*/
if (options.check_host_ip) {
Key *ip_key = key_new(host_key->type);
ip_file = user_hostfile;
ip_status = check_host_in_hostfile(ip_file, ip, host_key,
ip_key, &ip_line);
if (ip_status == HOST_NEW) {
ip_file = system_hostfile;
ip_status = check_host_in_hostfile(ip_file, ip,
host_key, ip_key, &ip_line);
}
if (host_status == HOST_CHANGED &&
(ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
host_ip_differ = 1;
key_free(ip_key);
} else
ip_status = host_status;
key_free(file_key);
switch (host_status) {
case HOST_OK:
/* The host is known and the key matches. */
debug("Host '%.200s' is known and matches the %s host key.",
host, type);
debug("Found key in %s:%d", host_file, host_line);
if (options.check_host_ip && ip_status == HOST_NEW) {
if (readonly)
logit("%s host key for IP address "
"'%.128s' not in list of known hosts.",
type, ip);
else if (!add_host_to_hostfile(user_hostfile, ip,
host_key))
logit("Failed to add the %s host key for IP "
"address '%.128s' to the list of known "
"hosts (%.30s).", type, ip, user_hostfile);
else
logit("Warning: Permanently added the %s host "
"key for IP address '%.128s' to the list "
"of known hosts.", type, ip);
}
break;
case HOST_NEW:
if (readonly)
goto fail;
/* The host is new. */
if (options.strict_host_key_checking == 1) {
/*
* User has requested strict host key checking. We
* will not add the host key automatically. The only
* alternative left is to abort.
*/
error("No %s host key is known for %.200s and you "
"have requested strict checking.", type, host);
goto fail;
} else if (options.strict_host_key_checking == 2) {
char msg1[1024], msg2[1024];
if (show_other_keys(host, host_key))
snprintf(msg1, sizeof(msg1),
"\nbut keys of different type are already"
" known for this host.");
else
snprintf(msg1, sizeof(msg1), ".");
/* The default */
fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
msg2[0] = '\0';
#ifdef DNS
if (options.verify_host_key_dns) {
if (verified_host_key_dns)
snprintf(msg2, sizeof(msg2),
"Matching host key fingerprint"
" found in DNS.\n");
else
snprintf(msg2, sizeof(msg2),
"No matching host key fingerprint"
" found in DNS.\n");
}
#endif
snprintf(msg, sizeof(msg),
"The authenticity of host '%.200s (%s)' can't be "
"established%s\n"
"%s key fingerprint is %s.\n%s"
"Are you sure you want to continue connecting "
"(yes/no)? ",
host, ip, msg1, type, fp, msg2);
xfree(fp);
if (!confirm(msg))
goto fail;
}
if (options.check_host_ip && ip_status == HOST_NEW) {
snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
hostp = hostline;
} else
hostp = host;
/*
* If not in strict mode, add the key automatically to the
* local known_hosts file.
*/
if (!add_host_to_hostfile(user_hostfile, hostp, host_key))
logit("Failed to add the host to the list of known "
"hosts (%.500s).", user_hostfile);
else
logit("Warning: Permanently added '%.200s' (%s) to the "
"list of known hosts.", hostp, type);
break;
case HOST_CHANGED:
if (options.check_host_ip && host_ip_differ) {
char *msg;
if (ip_status == HOST_NEW)
msg = "is unknown";
else if (ip_status == HOST_OK)
msg = "is unchanged";
else
msg = "has a different value";
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("The %s host key for %s has changed,", type, host);
error("and the key for the according IP address %s", ip);
error("%s. This could either mean that", msg);
error("DNS SPOOFING is happening or the IP address for the host");
error("and its host key have changed at the same time.");
if (ip_status != HOST_NEW)
error("Offending key for IP in %s:%d", ip_file, ip_line);
}
/* The host key has changed. */
fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
error("It is also possible that the %s host key has just been changed.", type);
error("The fingerprint for the %s key sent by the remote host is\n%s.",
type, fp);
error("Please contact your system administrator.");
error("Add correct host key in %.100s to get rid of this message.",
user_hostfile);
error("Offending key in %s:%d", host_file, host_line);
xfree(fp);
/*
* If strict host key checking is in use, the user will have
* to edit the key manually and we can only abort.
*/
if (options.strict_host_key_checking) {
error("%s host key for %.200s has changed and you have "
"requested strict checking.", type, host);
goto fail;
}
/*
* If strict host key checking has not been requested, allow
* the connection but without MITM-able authentication or
* agent forwarding.
*/
if (options.password_authentication) {
error("Password authentication is disabled to avoid "
"man-in-the-middle attacks.");
options.password_authentication = 0;
}
if (options.kbd_interactive_authentication) {
error("Keyboard-interactive authentication is disabled"
" to avoid man-in-the-middle attacks.");
options.kbd_interactive_authentication = 0;
options.challenge_response_authentication = 0;
}
if (options.challenge_response_authentication) {
error("Challenge/response authentication is disabled"
" to avoid man-in-the-middle attacks.");
options.challenge_response_authentication = 0;
}
if (options.forward_agent) {
error("Agent forwarding is disabled to avoid "
"man-in-the-middle attacks.");
options.forward_agent = 0;
}
if (options.forward_x11) {
error("X11 forwarding is disabled to avoid "
"man-in-the-middle attacks.");
options.forward_x11 = 0;
}
if (options.num_local_forwards > 0 ||
options.num_remote_forwards > 0) {
error("Port forwarding is disabled to avoid "
"man-in-the-middle attacks.");
options.num_local_forwards =
options.num_remote_forwards = 0;
}
/*
* XXX Should permit the user to change to use the new id.
* This could be done by converting the host key to an
* identifying sentence, tell that the host identifies itself
* by that sentence, and ask the user if he/she whishes to
* accept the authentication.
*/
break;
case HOST_FOUND:
fatal("internal error");
break;
}
if (options.check_host_ip && host_status != HOST_CHANGED &&
ip_status == HOST_CHANGED) {
snprintf(msg, sizeof(msg),
"Warning: the %s host key for '%.200s' "
"differs from the key for the IP address '%.128s'"
"\nOffending key for IP in %s:%d",
type, host, ip, ip_file, ip_line);
if (host_status == HOST_OK) {
len = strlen(msg);
snprintf(msg + len, sizeof(msg) - len,
"\nMatching host key in %s:%d",
host_file, host_line);
}
if (options.strict_host_key_checking == 1) {
logit("%s", msg);
error("Exiting, you have requested strict checking.");
goto fail;
} else if (options.strict_host_key_checking == 2) {
strlcat(msg, "\nAre you sure you want "
"to continue connecting (yes/no)? ", sizeof(msg));
if (!confirm(msg))
goto fail;
} else {
logit("%s", msg);
}
}
xfree(ip);
return 0;
fail:
xfree(ip);
return -1;
}
/* returns 0 if key verifies or -1 if key does NOT verify */
int
verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
{
struct stat st;
#ifdef DNS
if (options.verify_host_key_dns) {
switch(verify_host_key_dns(host, hostaddr, host_key)) {
case DNS_VERIFY_OK:
#ifdef DNSSEC
return 0;
#else
verified_host_key_dns = 1;
break;
#endif
case DNS_VERIFY_FAILED:
return -1;
case DNS_VERIFY_ERROR:
break;
default:
debug3("bad return value from verify_host_key_dns");
break;
}
}
#endif /* DNS */
/* return ok if the key can be found in an old keyfile */
if (stat(options.system_hostfile2, &st) == 0 ||
stat(options.user_hostfile2, &st) == 0) {
if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
options.user_hostfile2, options.system_hostfile2) == 0)
return 0;
}
return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
options.user_hostfile, options.system_hostfile);
}
/*
* 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(Sensitive *sensitive, const char *orighost,
struct sockaddr *hostaddr, struct passwd *pw)
{
char *host, *cp;
char *server_user, *local_user;
local_user = xstrdup(pw->pw_name);
server_user = options.user ? options.user : local_user;
/* 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(local_user, server_user, host, sensitive);
} else {
ssh_kex(host, hostaddr);
ssh_userauth1(local_user, server_user, host, sensitive);
}
}
void
ssh_put_password(char *password)
{
int size;
char *padded;
if (datafellows & SSH_BUG_PASSWORDPAD) {
packet_put_cstring(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);
}
static int
show_key_from_file(const char *file, const char *host, int keytype)
{
Key *found;
char *fp;
int line, ret;
found = key_new(keytype);
if ((ret = lookup_key_in_hostfile_by_type(file, host,
keytype, found, &line))) {
fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
logit("WARNING: %s key found for host %s\n"
"in %s:%d\n"
"%s key fingerprint %s.",
key_type(found), host, file, line,
key_type(found), fp);
xfree(fp);
}
key_free(found);
return (ret);
}
/* print all known host keys for a given host, but skip keys of given type */
static int
show_other_keys(const char *host, Key *key)
{
int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
int i, found = 0;
for (i = 0; type[i] != -1; i++) {
if (type[i] == key->type)
continue;
if (type[i] != KEY_RSA1 &&
show_key_from_file(options.user_hostfile2, host, type[i])) {
found = 1;
continue;
}
if (type[i] != KEY_RSA1 &&
show_key_from_file(options.system_hostfile2, host, type[i])) {
found = 1;
continue;
}
if (show_key_from_file(options.user_hostfile, host, type[i])) {
found = 1;
continue;
}
if (show_key_from_file(options.system_hostfile, host, type[i])) {
found = 1;
continue;
}
debug2("no key of type %d for host %s", type[i], host);
}
return (found);
}
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