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freebsd-dev/crypto/openssh/sshconnect.c
Mark Murray fe5fd0173b 1) Add kerberos5 functionality. 
by Daniel Kouril <kouril@informatics.muni.cz>
2) Add full LOGIN_CAP capability
   by Andrey Chernov
2000-02-28 19:03:50 +00:00

1912 lines
53 KiB
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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
* Created: Sat Mar 18 22:15:47 1995 ylo
* Code to connect to a remote host, and to perform the client side of the
* login (authentication) dialog.
*
* $FreeBSD$
*/
#include "includes.h"
RCSID("$OpenBSD: sshconnect.c,v 1.56 2000/02/18 08:50:33 markus Exp $");
#include <openssl/bn.h>
#include "xmalloc.h"
#include "rsa.h"
#include "ssh.h"
#include "packet.h"
#include "authfd.h"
#include "cipher.h"
#include "mpaux.h"
#include "uidswap.h"
#include "compat.h"
#include "readconf.h"
#include "fingerprint.h"
#include <openssl/md5.h>
/* Session id for the current session. */
unsigned char session_id[16];
/* authentications supported by server */
unsigned int supported_authentications;
extern Options options;
extern char *__progname;
/*
* Connect to the given ssh server using a proxy command.
*/
int
ssh_proxy_connect(const char *host, u_short port, uid_t original_real_uid,
const char *proxy_command)
{
Buffer command;
const char *cp;
char *command_string;
int pin[2], pout[2];
int 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];
/* Child. Permanently give up superuser privileges. */
permanently_set_uid(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] = "/bin/sh";
argv[1] = "-c";
argv[2] = command_string;
argv[3] = NULL;
/* Execute the proxy command. Note that we gave up any
extra privileges above. */
execv("/bin/sh", argv);
perror("/bin/sh");
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(uid_t original_real_uid, int privileged, int family)
{
int sock;
/*
* 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;
sock = rresvport_af(&p, family);
if (sock < 0)
error("rresvport: af=%d %.100s", family, strerror(errno));
else
debug("Allocated local port %d.", p);
} else {
/*
* Just create an ordinary socket on arbitrary port. We use
* the user's uid to create the socket.
*/
temporarily_use_uid(original_real_uid);
sock = socket(family, SOCK_STREAM, 0);
if (sock < 0)
error("socket: %.100s", strerror(errno));
restore_uid();
}
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, uid_t original_real_uid,
const char *proxy_command)
{
int sock = -1, attempt;
struct servent *sp;
struct addrinfo hints, *ai, *aitop;
char ntop[NI_MAXHOST], strport[NI_MAXSERV];
int gaierr;
struct linger linger;
debug("ssh_connect: getuid %d geteuid %d anon %d",
(int) getuid(), (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, original_real_uid, 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);
/* Create a socket for connecting. */
sock = ssh_create_socket(original_real_uid,
!anonymous && geteuid() == 0 && port < IPPORT_RESERVED,
ai->ai_family);
if (sock < 0)
continue;
/* Connect to the host. We use the user's uid in the
* hope that it will help with tcp_wrappers showing
* the remote uid as root.
*/
temporarily_use_uid(original_real_uid);
if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) {
/* Successful connection. */
memcpy(hostaddr, ai->ai_addr, sizeof(*hostaddr));
restore_uid();
break;
} else {
debug("connect: %.100s", strerror(errno));
restore_uid();
/*
* 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 the connection. */
packet_set_connection(sock, sock);
return 1;
}
/*
* Checks if the user has an authentication agent, and if so, tries to
* authenticate using the agent.
*/
int
try_agent_authentication()
{
int status, type;
char *comment;
AuthenticationConnection *auth;
unsigned char response[16];
unsigned int i;
BIGNUM *e, *n, *challenge;
/* Get connection to the agent. */
auth = ssh_get_authentication_connection();
if (!auth)
return 0;
e = BN_new();
n = BN_new();
challenge = BN_new();
/* Loop through identities served by the agent. */
for (status = ssh_get_first_identity(auth, e, n, &comment);
status;
status = ssh_get_next_identity(auth, e, n, &comment)) {
int plen, clen;
/* Try this identity. */
debug("Trying RSA authentication via agent with '%.100s'", comment);
xfree(comment);
/* Tell the server that we are willing to authenticate using this key. */
packet_start(SSH_CMSG_AUTH_RSA);
packet_put_bignum(n);
packet_send();
packet_write_wait();
/* Wait for server's response. */
type = packet_read(&plen);
/* The server sends failure if it doesn\'t like our key or
does not support RSA authentication. */
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our key.");
continue;
}
/* Otherwise it should have sent a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
packet_disconnect("Protocol error during RSA authentication: %d",
type);
packet_get_bignum(challenge, &clen);
packet_integrity_check(plen, clen, type);
debug("Received RSA challenge from server.");
/* Ask the agent to decrypt the challenge. */
if (!ssh_decrypt_challenge(auth, e, n, challenge,
session_id, 1, response)) {
/* The agent failed to authenticate this identifier although it
advertised it supports this. Just return a wrong value. */
log("Authentication agent failed to decrypt challenge.");
memset(response, 0, sizeof(response));
}
debug("Sending response to RSA challenge.");
/* Send the decrypted challenge back to the server. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(response[i]);
packet_send();
packet_write_wait();
/* Wait for response from the server. */
type = packet_read(&plen);
/* The server returns success if it accepted the authentication. */
if (type == SSH_SMSG_SUCCESS) {
debug("RSA authentication accepted by server.");
BN_clear_free(e);
BN_clear_free(n);
BN_clear_free(challenge);
return 1;
}
/* Otherwise it should return failure. */
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error waiting RSA auth response: %d",
type);
}
BN_clear_free(e);
BN_clear_free(n);
BN_clear_free(challenge);
debug("RSA authentication using agent refused.");
return 0;
}
/*
* Computes the proper response to a RSA challenge, and sends the response to
* the server.
*/
void
respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
{
unsigned char buf[32], response[16];
MD5_CTX md;
int i, len;
/* Decrypt the challenge using the private key. */
rsa_private_decrypt(challenge, challenge, prv);
/* Compute the response. */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > sizeof(buf))
packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
len);
memset(buf, 0, sizeof(buf));
BN_bn2bin(challenge, buf + sizeof(buf) - len);
MD5_Init(&md);
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(response, &md);
debug("Sending response to host key RSA challenge.");
/* Send the response back to the server. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(response[i]);
packet_send();
packet_write_wait();
memset(buf, 0, sizeof(buf));
memset(response, 0, sizeof(response));
memset(&md, 0, sizeof(md));
}
/*
* Checks if the user has authentication file, and if so, tries to authenticate
* the user using it.
*/
int
try_rsa_authentication(const char *authfile)
{
BIGNUM *challenge;
RSA *private_key;
RSA *public_key;
char *passphrase, *comment;
int type, i;
int plen, clen;
/* Try to load identification for the authentication key. */
public_key = RSA_new();
if (!load_public_key(authfile, public_key, &comment)) {
RSA_free(public_key);
/* Could not load it. Fail. */
return 0;
}
debug("Trying RSA authentication with key '%.100s'", comment);
/* Tell the server that we are willing to authenticate using this key. */
packet_start(SSH_CMSG_AUTH_RSA);
packet_put_bignum(public_key->n);
packet_send();
packet_write_wait();
/* We no longer need the public key. */
RSA_free(public_key);
/* Wait for server's response. */
type = packet_read(&plen);
/*
* The server responds with failure if it doesn\'t like our key or
* doesn\'t support RSA authentication.
*/
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our key.");
xfree(comment);
return 0;
}
/* Otherwise, the server should respond with a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
packet_disconnect("Protocol error during RSA authentication: %d", type);
/* Get the challenge from the packet. */
challenge = BN_new();
packet_get_bignum(challenge, &clen);
packet_integrity_check(plen, clen, type);
debug("Received RSA challenge from server.");
private_key = RSA_new();
/*
* Load the private key. Try first with empty passphrase; if it
* fails, ask for a passphrase.
*/
if (!load_private_key(authfile, "", private_key, NULL)) {
char buf[300];
snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ",
comment);
if (!options.batch_mode)
passphrase = read_passphrase(buf, 0);
else {
debug("Will not query passphrase for %.100s in batch mode.",
comment);
passphrase = xstrdup("");
}
/* Load the authentication file using the pasphrase. */
if (!load_private_key(authfile, passphrase, private_key, NULL)) {
memset(passphrase, 0, strlen(passphrase));
xfree(passphrase);
error("Bad passphrase.");
/* Send a dummy response packet to avoid protocol error. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(0);
packet_send();
packet_write_wait();
/* Expect the server to reject it... */
packet_read_expect(&plen, SSH_SMSG_FAILURE);
xfree(comment);
return 0;
}
/* Destroy the passphrase. */
memset(passphrase, 0, strlen(passphrase));
xfree(passphrase);
}
/* We no longer need the comment. */
xfree(comment);
/* Compute and send a response to the challenge. */
respond_to_rsa_challenge(challenge, private_key);
/* Destroy the private key. */
RSA_free(private_key);
/* We no longer need the challenge. */
BN_clear_free(challenge);
/* Wait for response from the server. */
type = packet_read(&plen);
if (type == SSH_SMSG_SUCCESS) {
debug("RSA authentication accepted by server.");
return 1;
}
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error waiting RSA auth response: %d", type);
debug("RSA authentication refused.");
return 0;
}
/*
* Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
* authentication and RSA host authentication.
*/
int
try_rhosts_rsa_authentication(const char *local_user, RSA * host_key)
{
int type;
BIGNUM *challenge;
int plen, clen;
debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
/* Tell the server that we are willing to authenticate using this key. */
packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
packet_put_string(local_user, strlen(local_user));
packet_put_int(BN_num_bits(host_key->n));
packet_put_bignum(host_key->e);
packet_put_bignum(host_key->n);
packet_send();
packet_write_wait();
/* Wait for server's response. */
type = packet_read(&plen);
/* The server responds with failure if it doesn't admit our
.rhosts authentication or doesn't know our host key. */
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our rhosts authentication or host key.");
return 0;
}
/* Otherwise, the server should respond with a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
packet_disconnect("Protocol error during RSA authentication: %d", type);
/* Get the challenge from the packet. */
challenge = BN_new();
packet_get_bignum(challenge, &clen);
packet_integrity_check(plen, clen, type);
debug("Received RSA challenge for host key from server.");
/* Compute a response to the challenge. */
respond_to_rsa_challenge(challenge, host_key);
/* We no longer need the challenge. */
BN_clear_free(challenge);
/* Wait for response from the server. */
type = packet_read(&plen);
if (type == SSH_SMSG_SUCCESS) {
debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
return 1;
}
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error waiting RSA auth response: %d", type);
debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
return 0;
}
#ifdef KRB4
int
try_krb4_authentication()
{
KTEXT_ST auth; /* Kerberos data */
char *reply;
char inst[INST_SZ];
char *realm;
CREDENTIALS cred;
int r, type, plen;
Key_schedule schedule;
u_long checksum, cksum;
MSG_DAT msg_data;
struct sockaddr_in local, foreign;
struct stat st;
/* Don't do anything if we don't have any tickets. */
if (stat(tkt_string(), &st) < 0)
return 0;
strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);
realm = (char *) krb_realmofhost(get_canonical_hostname());
if (!realm) {
debug("Kerberos V4: no realm for %s", get_canonical_hostname());
return 0;
}
/* This can really be anything. */
checksum = (u_long) getpid();
r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
if (r != KSUCCESS) {
debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
return 0;
}
/* Get session key to decrypt the server's reply with. */
r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
if (r != KSUCCESS) {
debug("get_cred failed: %s", krb_err_txt[r]);
return 0;
}
des_key_sched((des_cblock *) cred.session, schedule);
/* Send authentication info to server. */
packet_start(SSH_CMSG_AUTH_KRB4);
packet_put_string((char *) auth.dat, auth.length);
packet_send();
packet_write_wait();
/* Zero the buffer. */
(void) memset(auth.dat, 0, MAX_KTXT_LEN);
r = sizeof(local);
memset(&local, 0, sizeof(local));
if (getsockname(packet_get_connection_in(),
(struct sockaddr *) & local, &r) < 0)
debug("getsockname failed: %s", strerror(errno));
r = sizeof(foreign);
memset(&foreign, 0, sizeof(foreign));
if (getpeername(packet_get_connection_in(),
(struct sockaddr *) & foreign, &r) < 0) {
debug("getpeername failed: %s", strerror(errno));
fatal_cleanup();
}
/* Get server reply. */
type = packet_read(&plen);
switch (type) {
case SSH_SMSG_FAILURE:
/* Should really be SSH_SMSG_AUTH_KRB4_FAILURE */
debug("Kerberos V4 authentication failed.");
return 0;
break;
case SSH_SMSG_AUTH_KRB4_RESPONSE:
/* SSH_SMSG_AUTH_KRB4_SUCCESS */
debug("Kerberos V4 authentication accepted.");
/* Get server's response. */
reply = packet_get_string((unsigned int *) &auth.length);
memcpy(auth.dat, reply, auth.length);
xfree(reply);
packet_integrity_check(plen, 4 + auth.length, type);
/*
* If his response isn't properly encrypted with the session
* key, and the decrypted checksum fails to match, he's
* bogus. Bail out.
*/
r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
&foreign, &local, &msg_data);
if (r != KSUCCESS) {
debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
packet_disconnect("Kerberos V4 challenge failed!");
}
/* Fetch the (incremented) checksum that we supplied in the request. */
(void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
cksum = ntohl(cksum);
/* If it matches, we're golden. */
if (cksum == checksum + 1) {
debug("Kerberos V4 challenge successful.");
return 1;
} else
packet_disconnect("Kerberos V4 challenge failed!");
break;
default:
packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
}
return 0;
}
#endif /* KRB4 */
#ifdef AFS
int
send_krb4_tgt()
{
CREDENTIALS *creds;
char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
int r, type, plen;
unsigned char buffer[8192];
struct stat st;
/* Don't do anything if we don't have any tickets. */
if (stat(tkt_string(), &st) < 0)
return 0;
creds = xmalloc(sizeof(*creds));
if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
return 0;
}
if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
return 0;
}
if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
debug("Kerberos V4 ticket expired: %s", TKT_FILE);
return 0;
}
creds_to_radix(creds, buffer);
xfree(creds);
packet_start(SSH_CMSG_HAVE_KRB4_TGT);
packet_put_string((char *) buffer, strlen(buffer));
packet_send();
packet_write_wait();
type = packet_read(&plen);
if (type == SSH_SMSG_FAILURE)
debug("Kerberos TGT for realm %s rejected.", prealm);
else if (type != SSH_SMSG_SUCCESS)
packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
return 1;
}
void
send_afs_tokens(void)
{
CREDENTIALS creds;
struct ViceIoctl parms;
struct ClearToken ct;
int i, type, len, plen;
char buf[2048], *p, *server_cell;
unsigned char buffer[8192];
/* Move over ktc_GetToken, here's something leaner. */
for (i = 0; i < 100; i++) { /* just in case */
parms.in = (char *) &i;
parms.in_size = sizeof(i);
parms.out = buf;
parms.out_size = sizeof(buf);
if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
break;
p = buf;
/* Get secret token. */
memcpy(&creds.ticket_st.length, p, sizeof(unsigned int));
if (creds.ticket_st.length > MAX_KTXT_LEN)
break;
p += sizeof(unsigned int);
memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
p += creds.ticket_st.length;
/* Get clear token. */
memcpy(&len, p, sizeof(len));
if (len != sizeof(struct ClearToken))
break;
p += sizeof(len);
memcpy(&ct, p, len);
p += len;
p += sizeof(len); /* primary flag */
server_cell = p;
/* Flesh out our credentials. */
strlcpy(creds.service, "afs", sizeof creds.service);
creds.instance[0] = '\0';
strlcpy(creds.realm, server_cell, REALM_SZ);
memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
creds.issue_date = ct.BeginTimestamp;
creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
creds.kvno = ct.AuthHandle;
snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
creds.pinst[0] = '\0';
/* Encode token, ship it off. */
if (!creds_to_radix(&creds, buffer))
break;
packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
packet_put_string((char *) buffer, strlen(buffer));
packet_send();
packet_write_wait();
/* Roger, Roger. Clearance, Clarence. What's your vector,
Victor? */
type = packet_read(&plen);
if (type == SSH_SMSG_FAILURE)
debug("AFS token for cell %s rejected.", server_cell);
else if (type != SSH_SMSG_SUCCESS)
packet_disconnect("Protocol error on AFS token response: %d", type);
}
}
#endif /* AFS */
#ifdef KRB5
int
try_krb5_authentication(krb5_context *context, krb5_auth_context *auth_context)
{
krb5_error_code problem;
const char *tkfile;
struct stat buf;
krb5_ccache ccache = NULL;
krb5_creds req_creds;
krb5_creds *new_creds = NULL;
const char *remotehost;
krb5_data ap;
int type, payload_len;
krb5_ap_rep_enc_part *reply = NULL;
int ret;
memset(&ap, 0, sizeof(ap));
problem = krb5_init_context(context);
if (problem) {
ret = 0;
goto out;
}
tkfile = krb5_cc_default_name(*context);
if (strncmp(tkfile, "FILE:", 5) == 0)
tkfile += 5;
if (stat(tkfile, &buf) == 0 && getuid() != buf.st_uid) {
debug("Kerberos V5: could not get default ccache (permission denied).");
ret = 0;
goto out;
}
problem = krb5_cc_default(*context, &ccache);
if (problem) {
ret = 0;
goto out;
}
memset(&req_creds, 0, sizeof(req_creds));
remotehost = get_canonical_hostname();
problem = krb5_sname_to_principal(*context, remotehost,
"host", KRB5_NT_SRV_HST,
&req_creds.server);
if (problem) {
ret = 0;
goto out;
}
problem = krb5_cc_get_principal(*context, ccache, &req_creds.client);
if (problem) {
ret = 0;
goto out;
}
/* creds.session.keytype=ETYPE_DES_CBC_CRC; */
problem = krb5_get_credentials(*context, 0, ccache, &req_creds, &new_creds);
if (problem) {
ret = 0;
goto out;
}
problem = krb5_auth_con_init(*context, auth_context);
if (problem) {
ret = 0;
goto out;
}
/* krb5_auth_con_setflags(ssh_context, auth_context,
KRB5_AUTH_CONTEXT_RET_TIME);
*/
problem = krb5_mk_req_extended(*context, auth_context,
AP_OPTS_MUTUAL_REQUIRED /*| AP_OPTS_USE_SUBKEY*/ ,
NULL, new_creds, &ap);
if (problem) {
ret = 0;
goto out;
}
packet_start(SSH_CMSG_AUTH_KRB5);
packet_put_string((char *) ap.data, ap.length);
packet_send();
packet_write_wait();
xfree(ap.data);
ap.length = 0;
type = packet_read(&payload_len);
switch (type) {
case SSH_SMSG_FAILURE:
/* Should really be SSH_SMSG_AUTH_KRB5_FAILURE */
debug("Kerberos V5 authentication failed.");
ret = 0;
break;
case SSH_SMSG_AUTH_KRB5_RESPONSE:
/* SSH_SMSG_AUTH_KRB5_SUCCESS */
debug("Kerberos V5 authentication accepted.");
/* Get server's response. */
ap.data = packet_get_string((unsigned int *) &ap.length);
packet_integrity_check(payload_len, 4 + ap.length, type);
/* XXX je to dobre? */
problem = krb5_rd_rep(*context, *auth_context, &ap, &reply);
if (problem) {
ret = 0;
}
ret = 1;
break;
default:
packet_disconnect("Protocol error on Kerberos V5 response: %d", type);
ret = 0;
break;
}
out:
if (req_creds.server != NULL)
krb5_free_principal(*context, req_creds.server);
if (req_creds.client != NULL)
krb5_free_principal(*context, req_creds.client);
if (new_creds != NULL)
krb5_free_creds(*context, new_creds);
if (ccache != NULL)
krb5_cc_close(*context, ccache);
if (reply != NULL)
krb5_free_ap_rep_enc_part(*context, reply);
if (ap.length > 0)
krb5_data_free(&ap);
return ret;
}
void
send_krb5_tgt(krb5_context context, krb5_auth_context auth_context)
{
int fd;
int type, payload_len;
krb5_error_code problem;
krb5_data outbuf;
krb5_ccache ccache = NULL;
krb5_creds creds;
krb5_kdc_flags flags;
const char* remotehost = get_canonical_hostname();
memset(&creds, 0, sizeof(creds));
memset(&outbuf, 0, sizeof(outbuf));
fd = packet_get_connection_in();
problem = krb5_auth_con_setaddrs_from_fd(context, auth_context, &fd);
if (problem) {
goto out;
}
#if 0
tkfile = krb5_cc_default_name(context);
if (strncmp(tkfile, "FILE:", 5) == 0)
tkfile += 5;
if (stat(tkfile, &buf) == 0 && getuid() != buf.st_uid) {
debug("Kerberos V5: could not get default ccache (permission denied).");
goto out;
}
#endif
problem = krb5_cc_default(context, &ccache);
if (problem) {
goto out;
}
problem = krb5_cc_get_principal(context, ccache, &creds.client);
if (problem) {
goto out;
}
problem = krb5_build_principal(context, &creds.server,
strlen(creds.client->realm),
creds.client->realm,
"krbtgt",
creds.client->realm,
NULL);
if (problem) {
goto out;
}
creds.times.endtime = 0;
flags.i = 0;
flags.b.forwarded = 1;
flags.b.forwardable = krb5_config_get_bool(context, NULL,
"libdefaults", "forwardable", NULL);
problem = krb5_get_forwarded_creds (context,
auth_context,
ccache,
flags.i,
remotehost,
&creds,
&outbuf);
if (problem) {
goto out;
}
packet_start(SSH_CMSG_HAVE_KRB5_TGT);
packet_put_string((char *)outbuf.data, outbuf.length);
packet_send();
packet_write_wait();
type = packet_read(&payload_len);
switch (type) {
case SSH_SMSG_SUCCESS:
break;
case SSH_SMSG_FAILURE:
break;
default:
break;
}
out:
if (creds.client)
krb5_free_principal(context, creds.client);
if (creds.server)
krb5_free_principal(context, creds.server);
if (ccache)
krb5_cc_close(context, ccache);
if (outbuf.data)
xfree(outbuf.data);
return;
}
#endif /* KRB5 */
/*
* Tries to authenticate with any string-based challenge/response system.
* Note that the client code is not tied to s/key or TIS.
*/
int
try_skey_authentication()
{
int type, i, payload_len;
char *challenge, *response;
debug("Doing skey authentication.");
/* request a challenge */
packet_start(SSH_CMSG_AUTH_TIS);
packet_send();
packet_write_wait();
type = packet_read(&payload_len);
if (type != SSH_SMSG_FAILURE &&
type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
packet_disconnect("Protocol error: got %d in response "
"to skey-auth", type);
}
if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
debug("No challenge for skey authentication.");
return 0;
}
challenge = packet_get_string(&payload_len);
if (options.cipher == SSH_CIPHER_NONE)
log("WARNING: Encryption is disabled! "
"Reponse will be transmitted in clear text.");
fprintf(stderr, "%s\n", challenge);
xfree(challenge);
fflush(stderr);
for (i = 0; i < options.number_of_password_prompts; i++) {
if (i != 0)
error("Permission denied, please try again.");
response = read_passphrase("Response: ", 0);
packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
packet_put_string(response, strlen(response));
memset(response, 0, strlen(response));
xfree(response);
packet_send();
packet_write_wait();
type = packet_read(&payload_len);
if (type == SSH_SMSG_SUCCESS)
return 1;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response "
"to skey-auth-reponse", type);
}
/* failure */
return 0;
}
/*
* Tries to authenticate with plain passwd authentication.
*/
int
try_password_authentication(char *prompt)
{
int type, i, payload_len;
char *password;
debug("Doing password authentication.");
if (options.cipher == SSH_CIPHER_NONE)
log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
for (i = 0; i < options.number_of_password_prompts; i++) {
if (i != 0)
error("Permission denied, please try again.");
password = read_passphrase(prompt, 0);
packet_start(SSH_CMSG_AUTH_PASSWORD);
packet_put_string(password, strlen(password));
memset(password, 0, strlen(password));
xfree(password);
packet_send();
packet_write_wait();
type = packet_read(&payload_len);
if (type == SSH_SMSG_SUCCESS)
return 1;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to passwd auth", type);
}
/* failure */
return 0;
}
/*
* Waits for the server identification string, and sends our own
* identification string.
*/
void
ssh_exchange_identification()
{
char buf[256], remote_version[256]; /* must be same size! */
int remote_major, remote_minor, i;
int connection_in = packet_get_connection_in();
int connection_out = packet_get_connection_out();
/* Read other side\'s version identification. */
for (i = 0; i < sizeof(buf) - 1; i++) {
int len = 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;
break;
}
if (buf[i] == '\n') {
buf[i + 1] = 0;
break;
}
}
buf[sizeof(buf) - 1] = 0;
/*
* Check that the versions match. In future this might accept
* several versions and set appropriate flags to handle them.
*/
if (sscanf(buf, "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);
/* Check if the remote protocol version is too old. */
if (remote_major == 1 && remote_minor < 3)
fatal("Remote machine has too old SSH software version.");
/* We speak 1.3, too. */
if (remote_major == 1 && remote_minor == 3) {
enable_compat13();
if (options.forward_agent) {
log("Agent forwarding disabled for protocol 1.3");
options.forward_agent = 0;
}
}
#if 0
/*
* Removed for now, to permit compatibility with latter versions. The
* server will reject our version and disconnect if it doesn't
* support it.
*/
if (remote_major != PROTOCOL_MAJOR)
fatal("Protocol major versions differ: %d vs. %d",
PROTOCOL_MAJOR, remote_major);
#endif
/* Send our own protocol version identification. */
snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
fatal("write: %.100s", strerror(errno));
}
int ssh_cipher_default = SSH_CIPHER_3DES;
int
read_yes_or_no(const char *prompt, int defval)
{
char buf[1024];
FILE *f;
int retval = -1;
if (isatty(0))
f = stdin;
else
f = fopen("/dev/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;
if (strcmp(buf, "no") == 0)
retval = 0;
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, RSA *host_key)
{
RSA *file_key;
char *ip = NULL;
char hostline[1000], *hostp;
HostStatus host_status;
HostStatus ip_status;
int local = 0, host_ip_differ = 0;
char ntop[NI_MAXHOST];
/*
* 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.
*/
switch (hostaddr->sa_family) {
case AF_INET:
local = (ntohl(((struct sockaddr_in *)hostaddr)->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
break;
case AF_INET6:
local = IN6_IS_ADDR_LOOPBACK(&(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
break;
default:
local = 0;
break;
}
if (local) {
debug("Forcing accepting of host key for loopback/localhost.");
return;
}
/*
* Turn off check_host_ip for proxy connects, since
* we don't have the remote ip-address
*/
if (options.proxy_command != NULL && options.check_host_ip)
options.check_host_ip = 0;
if (options.check_host_ip) {
if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
NULL, 0, NI_NUMERICHOST) != 0)
fatal("check_host_key: getnameinfo failed");
ip = xstrdup(ntop);
}
/*
* 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 = RSA_new();
file_key->n = BN_new();
file_key->e = BN_new();
/*
* Check if the host key is present in the user\'s list of known
* hosts or in the systemwide list.
*/
host_status = check_host_in_hostfile(options.user_hostfile, host,
host_key->e, host_key->n,
file_key->e, file_key->n);
if (host_status == HOST_NEW)
host_status = check_host_in_hostfile(options.system_hostfile, host,
host_key->e, host_key->n,
file_key->e, file_key->n);
/*
* 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 && !local && strcmp(host, ip)) {
RSA *ip_key = RSA_new();
ip_key->n = BN_new();
ip_key->e = BN_new();
ip_status = check_host_in_hostfile(options.user_hostfile, ip,
host_key->e, host_key->n,
ip_key->e, ip_key->n);
if (ip_status == HOST_NEW)
ip_status = check_host_in_hostfile(options.system_hostfile, ip,
host_key->e, host_key->n,
ip_key->e, ip_key->n);
if (host_status == HOST_CHANGED &&
(ip_status != HOST_CHANGED ||
(BN_cmp(ip_key->e, file_key->e) || BN_cmp(ip_key->n, file_key->n))))
host_ip_differ = 1;
RSA_free(ip_key);
} else
ip_status = host_status;
RSA_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 host key.", host);
if (options.check_host_ip) {
if (ip_status == HOST_NEW) {
if (!add_host_to_hostfile(options.user_hostfile, ip,
host_key->e, host_key->n))
log("Failed to add the host key for IP address '%.30s' to the list of known hosts (%.30s).",
ip, options.user_hostfile);
else
log("Warning: Permanently added host key for IP address '%.30s' to the list of known hosts.",
ip);
} else if (ip_status != HOST_OK)
log("Warning: the host key for '%.200s' differs from the key for the IP address '%.30s'",
host, ip);
}
break;
case HOST_NEW:
/* 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. */
fatal("No host key is known for %.200s and you have requested strict checking.", host);
} else if (options.strict_host_key_checking == 2) {
/* The default */
char prompt[1024];
char *fp = fingerprint(host_key->e, host_key->n);
snprintf(prompt, sizeof(prompt),
"The authenticity of host '%.200s' can't be established.\n"
"Key fingerprint is %d %s.\n"
"Are you sure you want to continue connecting (yes/no)? ",
host, BN_num_bits(host_key->n), fp);
if (!read_yes_or_no(prompt, -1))
fatal("Aborted by user!\n");
}
if (options.check_host_ip && ip_status == HOST_NEW && strcmp(host, ip)) {
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(options.user_hostfile, hostp,
host_key->e, host_key->n))
log("Failed to add the host to the list of known hosts (%.500s).",
options.user_hostfile);
else
log("Warning: Permanently added '%.200s' to the list of known hosts.",
hostp);
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 host key for %s has changed,", 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");
}
/* The host key has changed. */
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 host key has just been changed.");
error("Please contact your system administrator.");
error("Add correct host key in %.100s to get rid of this message.",
options.user_hostfile);
/*
* 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)
fatal("Host key for %.200s has changed and you have requested strict checking.", host);
/*
* If strict host key checking has not been requested, allow
* the connection but without password authentication or
* agent forwarding.
*/
if (options.password_authentication) {
error("Password authentication is disabled to avoid trojan horses.");
options.password_authentication = 0;
}
if (options.forward_agent) {
error("Agent forwarding is disabled to avoid trojan horses.");
options.forward_agent = 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;
}
if (options.check_host_ip)
xfree(ip);
}
/*
* SSH1 key exchange
*/
void
ssh_kex(char *host, struct sockaddr *hostaddr)
{
int i;
BIGNUM *key;
RSA *host_key;
RSA *public_key;
int bits, rbits;
unsigned char session_key[SSH_SESSION_KEY_LENGTH];
unsigned char cookie[8];
unsigned int supported_ciphers;
unsigned int server_flags, client_flags;
int payload_len, clen, sum_len = 0;
u_int32_t rand = 0;
debug("Waiting for server public key.");
/* Wait for a public key packet from the server. */
packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
/* Get cookie from the packet. */
for (i = 0; i < 8; i++)
cookie[i] = packet_get_char();
/* Get the public key. */
public_key = RSA_new();
bits = packet_get_int();/* bits */
public_key->e = BN_new();
packet_get_bignum(public_key->e, &clen);
sum_len += clen;
public_key->n = BN_new();
packet_get_bignum(public_key->n, &clen);
sum_len += clen;
rbits = BN_num_bits(public_key->n);
if (bits != rbits) {
log("Warning: Server lies about size of server public key: "
"actual size is %d bits vs. announced %d.", rbits, bits);
log("Warning: This may be due to an old implementation of ssh.");
}
/* Get the host key. */
host_key = RSA_new();
bits = packet_get_int();/* bits */
host_key->e = BN_new();
packet_get_bignum(host_key->e, &clen);
sum_len += clen;
host_key->n = BN_new();
packet_get_bignum(host_key->n, &clen);
sum_len += clen;
rbits = BN_num_bits(host_key->n);
if (bits != rbits) {
log("Warning: Server lies about size of server host key: "
"actual size is %d bits vs. announced %d.", rbits, bits);
log("Warning: This may be due to an old implementation of ssh.");
}
/* Get protocol flags. */
server_flags = packet_get_int();
packet_set_protocol_flags(server_flags);
supported_ciphers = packet_get_int();
supported_authentications = packet_get_int();
debug("Received server public key (%d bits) and host key (%d bits).",
BN_num_bits(public_key->n), BN_num_bits(host_key->n));
packet_integrity_check(payload_len,
8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
SSH_SMSG_PUBLIC_KEY);
check_host_key(host, hostaddr, host_key);
client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
compute_session_id(session_id, cookie, host_key->n, public_key->n);
/* Generate a session key. */
arc4random_stir();
/*
* Generate an encryption key for the session. The key is a 256 bit
* random number, interpreted as a 32-byte key, with the least
* significant 8 bits being the first byte of the key.
*/
for (i = 0; i < 32; i++) {
if (i % 4 == 0)
rand = arc4random();
session_key[i] = rand & 0xff;
rand >>= 8;
}
/*
* According to the protocol spec, the first byte of the session key
* is the highest byte of the integer. The session key is xored with
* the first 16 bytes of the session id.
*/
key = BN_new();
BN_set_word(key, 0);
for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
BN_lshift(key, key, 8);
if (i < 16)
BN_add_word(key, session_key[i] ^ session_id[i]);
else
BN_add_word(key, session_key[i]);
}
/*
* Encrypt the integer using the public key and host key of the
* server (key with smaller modulus first).
*/
if (BN_cmp(public_key->n, host_key->n) < 0) {
/* Public key has smaller modulus. */
if (BN_num_bits(host_key->n) <
BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
"SSH_KEY_BITS_RESERVED %d",
BN_num_bits(host_key->n),
BN_num_bits(public_key->n),
SSH_KEY_BITS_RESERVED);
}
rsa_public_encrypt(key, key, public_key);
rsa_public_encrypt(key, key, host_key);
} else {
/* Host key has smaller modulus (or they are equal). */
if (BN_num_bits(public_key->n) <
BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
"SSH_KEY_BITS_RESERVED %d",
BN_num_bits(public_key->n),
BN_num_bits(host_key->n),
SSH_KEY_BITS_RESERVED);
}
rsa_public_encrypt(key, key, host_key);
rsa_public_encrypt(key, key, public_key);
}
/* Destroy the public keys since we no longer need them. */
RSA_free(public_key);
RSA_free(host_key);
if (options.cipher == SSH_CIPHER_NOT_SET) {
if (cipher_mask() & supported_ciphers & (1 << ssh_cipher_default))
options.cipher = ssh_cipher_default;
else {
debug("Cipher %s not supported, using %.100s instead.",
cipher_name(ssh_cipher_default),
cipher_name(SSH_FALLBACK_CIPHER));
options.cipher = SSH_FALLBACK_CIPHER;
}
}
/* Check that the selected cipher is supported. */
if (!(supported_ciphers & (1 << options.cipher)))
fatal("Selected cipher type %.100s not supported by server.",
cipher_name(options.cipher));
debug("Encryption type: %.100s", cipher_name(options.cipher));
/* Send the encrypted session key to the server. */
packet_start(SSH_CMSG_SESSION_KEY);
packet_put_char(options.cipher);
/* Send the cookie back to the server. */
for (i = 0; i < 8; i++)
packet_put_char(cookie[i]);
/* Send and destroy the encrypted encryption key integer. */
packet_put_bignum(key);
BN_clear_free(key);
/* Send protocol flags. */
packet_put_int(client_flags);
/* Send the packet now. */
packet_send();
packet_write_wait();
debug("Sent encrypted session key.");
/* Set the encryption key. */
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
/* We will no longer need the session key here. Destroy any extra copies. */
memset(session_key, 0, sizeof(session_key));
/*
* Expect a success message from the server. Note that this message
* will be received in encrypted form.
*/
packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
debug("Received encrypted confirmation.");
}
/*
* Authenticate user
*/
void
ssh_userauth(int host_key_valid, RSA *own_host_key,
uid_t original_real_uid, char *host)
{
int i, type;
int payload_len;
struct passwd *pw;
const char *server_user, *local_user;
/* Get local user name. Use it as server user if no user name was given. */
pw = getpwuid(original_real_uid);
if (!pw)
fatal("User id %d not found from user database.", original_real_uid);
local_user = xstrdup(pw->pw_name);
server_user = options.user ? options.user : local_user;
/* Send the name of the user to log in as on the server. */
packet_start(SSH_CMSG_USER);
packet_put_string(server_user, strlen(server_user));
packet_send();
packet_write_wait();
/*
* The server should respond with success if no authentication is
* needed (the user has no password). Otherwise the server responds
* with failure.
*/
type = packet_read(&payload_len);
/* check whether the connection was accepted without authentication. */
if (type == SSH_SMSG_SUCCESS)
return;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
type);
#ifdef AFS
/* Try Kerberos tgt passing if the server supports it. */
if ((supported_authentications & (1 << SSH_PASS_KRB4_TGT)) &&
options.krb4_tgt_passing) {
if (options.cipher == SSH_CIPHER_NONE)
log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
(void) send_krb4_tgt();
}
/* Try AFS token passing if the server supports it. */
if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
options.afs_token_passing && k_hasafs()) {
if (options.cipher == SSH_CIPHER_NONE)
log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
send_afs_tokens();
}
#endif /* AFS */
#ifdef KRB4
if ((supported_authentications & (1 << SSH_AUTH_KRB4)) &&
options.krb4_authentication) {
debug("Trying Kerberos authentication.");
if (try_krb4_authentication()) {
/* The server should respond with success or failure. */
type = packet_read(&payload_len);
if (type == SSH_SMSG_SUCCESS)
return;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
}
}
#endif /* KRB4 */
#ifdef KRB5
if ((supported_authentications & (1 << SSH_AUTH_KRB5)) &&
options.krb5_authentication){
krb5_context ssh_context = NULL;
krb5_auth_context auth_context = NULL;
debug("Trying Kerberos V5 authentication.");
if (try_krb5_authentication(&ssh_context, &auth_context)) {
type = packet_read(&payload_len);
if (type == SSH_SMSG_SUCCESS) {
if ((supported_authentications & (1 << SSH_PASS_KRB5_TGT)) &&
options.krb5_tgt_passing) {
if (options.cipher == SSH_CIPHER_NONE)
log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
send_krb5_tgt(ssh_context, auth_context);
}
krb5_auth_con_free(ssh_context, auth_context);
krb5_free_context(ssh_context);
return;
}
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to Kerberos5 auth", type);
}
}
#endif /* KRB5 */
/*
* Use rhosts authentication if running in privileged socket and we
* do not wish to remain anonymous.
*/
if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
options.rhosts_authentication) {
debug("Trying rhosts authentication.");
packet_start(SSH_CMSG_AUTH_RHOSTS);
packet_put_string(local_user, strlen(local_user));
packet_send();
packet_write_wait();
/* The server should respond with success or failure. */
type = packet_read(&payload_len);
if (type == SSH_SMSG_SUCCESS)
return;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to rhosts auth",
type);
}
/*
* Try .rhosts or /etc/hosts.equiv authentication with RSA host
* authentication.
*/
if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
options.rhosts_rsa_authentication && host_key_valid) {
if (try_rhosts_rsa_authentication(local_user, own_host_key))
return;
}
/* Try RSA authentication if the server supports it. */
if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
options.rsa_authentication) {
/*
* Try RSA authentication using the authentication agent. The
* agent is tried first because no passphrase is needed for
* it, whereas identity files may require passphrases.
*/
if (try_agent_authentication())
return;
/* Try RSA authentication for each identity. */
for (i = 0; i < options.num_identity_files; i++)
if (try_rsa_authentication(options.identity_files[i]))
return;
}
/* Try skey authentication if the server supports it. */
if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
options.skey_authentication && !options.batch_mode) {
if (try_skey_authentication())
return;
}
/* Try password authentication if the server supports it. */
if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
options.password_authentication && !options.batch_mode) {
char prompt[80];
snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
server_user, host);
if (try_password_authentication(prompt))
return;
}
/* All authentication methods have failed. Exit with an error message. */
fatal("Permission denied.");
/* NOTREACHED */
}
/*
* 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(int host_key_valid, RSA *own_host_key, const char *orighost,
struct sockaddr *hostaddr, uid_t original_real_uid)
{
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();
supported_authentications = 0;
/* key exchange */
ssh_kex(host, hostaddr);
if (supported_authentications == 0)
fatal("supported_authentications == 0.");
/* authenticate user */
ssh_userauth(host_key_valid, own_host_key, original_real_uid, host);
}
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