openssh/dist/auth1.c

/* $OpenBSD: auth1.c,v 1.80 2014/02/02 03:44:31 djm Exp $ */
/*
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 *
 * 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"

#include <sys/types.h>

#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <pwd.h>

#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "rsa.h"
#include "ssh1.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "servconf.h"
#include "compat.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "channels.h"
#include "session.h"
#include "uidswap.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "buffer.h"

/* import */
extern ServerOptions options;
extern Buffer loginmsg;

static int auth1_process_password(Authctxt *);
static int auth1_process_rsa(Authctxt *);
static int auth1_process_rhosts_rsa(Authctxt *);
static int auth1_process_tis_challenge(Authctxt *);
static int auth1_process_tis_response(Authctxt *);

static char *client_user = NULL;    /* Used to fill in remote user for PAM */

struct AuthMethod1 {
        int type;
        char *name;
        int *enabled;
        int (*method)(Authctxt *);
};

const struct AuthMethod1 auth1_methods[] = {
        {
                SSH_CMSG_AUTH_PASSWORD, "password",
                &options.password_authentication, auth1_process_password
        },
        {
                SSH_CMSG_AUTH_RSA, "rsa",
                &options.rsa_authentication, auth1_process_rsa
        },
        {
                SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
                &options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
        },
        {
                SSH_CMSG_AUTH_TIS, "challenge-response",
                &options.challenge_response_authentication,
                auth1_process_tis_challenge
        },
        {
                SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
                &options.challenge_response_authentication,
                auth1_process_tis_response
        },
        { -1, NULL, NULL, NULL}
};

static const struct AuthMethod1
*lookup_authmethod1(int type)
{
        int i;

        for (i = 0; auth1_methods[i].name != NULL; i++)
                if (auth1_methods[i].type == type)
                        return (&(auth1_methods[i]));

        return (NULL);
}

static char *
get_authname(int type)
{
        const struct AuthMethod1 *a;
        static char buf[64];

        if ((a = lookup_authmethod1(type)) != NULL)
                return (a->name);
        snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
        return (buf);
}

/*ARGSUSED*/
static int
auth1_process_password(Authctxt *authctxt)
{
        int authenticated = 0;
        char *password;
        u_int dlen;

        /*
         * Read user password.  It is in plain text, but was
         * transmitted over the encrypted channel so it is
         * not visible to an outside observer.
         */
        password = packet_get_string(&dlen);
        packet_check_eom();

        /* Try authentication with the password. */
        authenticated = PRIVSEP(auth_password(authctxt, password));

        explicit_bzero(password, dlen);
        free(password);

        return (authenticated);
}

/*ARGSUSED*/
static int
auth1_process_rsa(Authctxt *authctxt)
{
        int authenticated = 0;
        BIGNUM *n;

        /* RSA authentication requested. */
        if ((n = BN_new()) == NULL)
                fatal("do_authloop: BN_new failed");
        packet_get_bignum(n);
        packet_check_eom();
        authenticated = auth_rsa(authctxt, n);
        BN_clear_free(n);

        return (authenticated);
}

/*ARGSUSED*/
static int
auth1_process_rhosts_rsa(Authctxt *authctxt)
{
        int keybits, authenticated = 0;
        u_int bits;
        Key *client_host_key;
        u_int ulen;

        /*
         * Get client user name.  Note that we just have to
         * trust the client; root on the client machine can
         * claim to be any user.
         */
        client_user = packet_get_cstring(&ulen);

        /* Get the client host key. */
        client_host_key = key_new(KEY_RSA1);
        bits = packet_get_int();
        packet_get_bignum(client_host_key->rsa->e);
        packet_get_bignum(client_host_key->rsa->n);

        keybits = BN_num_bits(client_host_key->rsa->n);
        if (keybits < 0 || bits != (u_int)keybits) {
                verbose("Warning: keysize mismatch for client_host_key: "
                    "actual %d, announced %d",
                    BN_num_bits(client_host_key->rsa->n), bits);
        }
        packet_check_eom();

        authenticated = auth_rhosts_rsa(authctxt, client_user,
            client_host_key);
        key_free(client_host_key);

        auth_info(authctxt, "ruser %.100s", client_user);

        return (authenticated);
}

/*ARGSUSED*/
static int
auth1_process_tis_challenge(Authctxt *authctxt)
{
        char *challenge;

        if ((challenge = get_challenge(authctxt)) == NULL)
                return (0);

        debug("sending challenge '%s'", challenge);
        packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
        packet_put_cstring(challenge);
        free(challenge);
        packet_send();
        packet_write_wait();

        return (-1);
}

/*ARGSUSED*/
static int
auth1_process_tis_response(Authctxt *authctxt)
{
        int authenticated = 0;
        char *response;
        u_int dlen;

        response = packet_get_string(&dlen);
        packet_check_eom();
        authenticated = verify_response(authctxt, response);
        explicit_bzero(response, dlen);
        free(response);

        return (authenticated);
}

/*
 * read packets, try to authenticate the user and
 * return only if authentication is successful
 */
static void
do_authloop(Authctxt *authctxt)
{
        int authenticated = 0;
        int prev = 0, type = 0;
        const struct AuthMethod1 *meth;

        debug("Attempting authentication for %s%.100s.",
            authctxt->valid ? "" : "invalid user ", authctxt->user);

        /* If the user has no password, accept authentication immediately. */
        if (options.permit_empty_passwd && options.password_authentication &&
#ifdef KRB5
            (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
#endif
            PRIVSEP(auth_password(authctxt, ""))) {
#ifdef USE_PAM
                if (options.use_pam && (PRIVSEP(do_pam_account())))
#endif
                {
                        auth_log(authctxt, 1, 0, "without authentication",
                            NULL);
                        return;
                }
        }

        /* Indicate that authentication is needed. */
        packet_start(SSH_SMSG_FAILURE);
        packet_send();
        packet_write_wait();

        for (;;) {
                /* default to fail */
                authenticated = 0;


                /* Get a packet from the client. */
                prev = type;
                type = packet_read();

                /*
                 * If we started challenge-response authentication but the
                 * next packet is not a response to our challenge, release
                 * the resources allocated by get_challenge() (which would
                 * normally have been released by verify_response() had we
                 * received such a response)
                 */
                if (prev == SSH_CMSG_AUTH_TIS &&
                    type != SSH_CMSG_AUTH_TIS_RESPONSE)
                        abandon_challenge_response(authctxt);

                if (authctxt->failures >= options.max_authtries)
                        goto skip;
                if ((meth = lookup_authmethod1(type)) == NULL) {
                        logit("Unknown message during authentication: "
                            "type %d", type);
                        goto skip;
                }

                if (!*(meth->enabled)) {
                        verbose("%s authentication disabled.", meth->name);
                        goto skip;
                }

                authenticated = meth->method(authctxt);
                if (authenticated == -1)
                        continue; /* "postponed" */

#ifdef BSD_AUTH
                if (authctxt->as) {
                        auth_close(authctxt->as);
                        authctxt->as = NULL;
                }
#endif
                if (!authctxt->valid && authenticated)
                        fatal("INTERNAL ERROR: authenticated invalid user %s",
                            authctxt->user);

#ifdef _UNICOS
                if (authenticated && cray_access_denied(authctxt->user)) {
                        authenticated = 0;
                        fatal("Access denied for user %s.",authctxt->user);
                }
#endif /* _UNICOS */

#ifndef HAVE_CYGWIN
                /* Special handling for root */
                if (authenticated && authctxt->pw->pw_uid == 0 &&
                    !auth_root_allowed(meth->name)) {
                        authenticated = 0;
# ifdef SSH_AUDIT_EVENTS
                        PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
# endif
                }
#endif

#ifdef USE_PAM
                if (options.use_pam && authenticated &&
                    !PRIVSEP(do_pam_account())) {
                        char *msg;
                        size_t len;

                        error("Access denied for user %s by PAM account "
                            "configuration", authctxt->user);
                        len = buffer_len(&loginmsg);
                        buffer_append(&loginmsg, "\0", 1);
                        msg = buffer_ptr(&loginmsg);
                        /* strip trailing newlines */
                        if (len > 0)
                                while (len > 0 && msg[--len] == '\n')
                                        msg[len] = '\0';
                        else
                                msg = "Access denied.";
                        packet_disconnect("%s", msg);
                }
#endif

 skip:
                /* Log before sending the reply */
                auth_log(authctxt, authenticated, 0, get_authname(type), NULL);

                free(client_user);
                client_user = NULL;

                if (authenticated)
                        return;

                if (++authctxt->failures >= options.max_authtries) {
#ifdef SSH_AUDIT_EVENTS
                        PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
#endif
                        packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
                }

                packet_start(SSH_SMSG_FAILURE);
                packet_send();
                packet_write_wait();
        }
}

/*
 * Performs authentication of an incoming connection.  Session key has already
 * been exchanged and encryption is enabled.
 */
void
do_authentication(Authctxt *authctxt)
{
        u_int ulen;
        char *user, *style = NULL;

        /* Get the name of the user that we wish to log in as. */
        packet_read_expect(SSH_CMSG_USER);

        /* Get the user name. */
        user = packet_get_cstring(&ulen);
        packet_check_eom();

        if ((style = strchr(user, ':')) != NULL)
                *style++ = '\0';

        authctxt->user = user;
        authctxt->style = style;

        /* Verify that the user is a valid user. */
        if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
                authctxt->valid = 1;
        else {
                debug("do_authentication: invalid user %s", user);
                authctxt->pw = fakepw();
        }

        /* Configuration may have changed as a result of Match */
        if (options.num_auth_methods != 0)
                fatal("AuthenticationMethods is not supported with SSH "
                    "protocol 1");

        setproctitle("%s%s", authctxt->valid ? user : "unknown",
            use_privsep ? " [net]" : "");

#ifdef USE_PAM
        if (options.use_pam)
                PRIVSEP(start_pam(authctxt));
#endif

        /*
         * If we are not running as root, the user must have the same uid as
         * the server.
         */
#ifndef HAVE_CYGWIN
        if (!use_privsep && getuid() != 0 && authctxt->pw &&
            authctxt->pw->pw_uid != getuid())
                packet_disconnect("Cannot change user when server not running as root.");
#endif

        /*
         * Loop until the user has been authenticated or the connection is
         * closed, do_authloop() returns only if authentication is successful
         */
        do_authloop(authctxt);

        /* The user has been authenticated and accepted. */
        packet_start(SSH_SMSG_SUCCESS);
        packet_send();
        packet_write_wait();
}
Revision:	6863
Committed:	Sat Oct 11 16:33:18 2014 UTC (9 years, 6 months ago) by laffer1
Content type:	text/plain
File size:	10323 byte(s)
Log Message:	openssh 6.6p1
#	Content
1	/* $OpenBSD: auth1.c,v 1.80 2014/02/02 03:44:31 djm Exp $ */
2	/*
3	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4	* All rights reserved
5	*
6	* As far as I am concerned, the code I have written for this software
7	* can be used freely for any purpose. Any derived versions of this
8	* software must be clearly marked as such, and if the derived work is
9	* incompatible with the protocol description in the RFC file, it must be
10	* called by a name other than "ssh" or "Secure Shell".
11	*/
12
13	#include "includes.h"
14
15	#include <sys/types.h>
16
17	#include <stdarg.h>
18	#include <stdio.h>
19	#include <string.h>
20	#include <unistd.h>
21	#include <pwd.h>
22
23	#include "openbsd-compat/sys-queue.h"
24	#include "xmalloc.h"
25	#include "rsa.h"
26	#include "ssh1.h"
27	#include "packet.h"
28	#include "buffer.h"
29	#include "log.h"
30	#include "servconf.h"
31	#include "compat.h"
32	#include "key.h"
33	#include "hostfile.h"
34	#include "auth.h"
35	#include "channels.h"
36	#include "session.h"
37	#include "uidswap.h"
38	#ifdef GSSAPI
39	#include "ssh-gss.h"
40	#endif
41	#include "monitor_wrap.h"
42	#include "buffer.h"
43
44	/* import */
45	extern ServerOptions options;
46	extern Buffer loginmsg;
47
48	static int auth1_process_password(Authctxt *);
49	static int auth1_process_rsa(Authctxt *);
50	static int auth1_process_rhosts_rsa(Authctxt *);
51	static int auth1_process_tis_challenge(Authctxt *);
52	static int auth1_process_tis_response(Authctxt *);
53
54	static char client_user = NULL; / Used to fill in remote user for PAM */
55
56	struct AuthMethod1 {
57	int type;
58	char *name;
59	int *enabled;
60	int (method)(Authctxt );
61	};
62
63	const struct AuthMethod1 auth1_methods[] = {
64	{
65	SSH_CMSG_AUTH_PASSWORD, "password",
66	&options.password_authentication, auth1_process_password
67	},
68	{
69	SSH_CMSG_AUTH_RSA, "rsa",
70	&options.rsa_authentication, auth1_process_rsa
71	},
72	{
73	SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
74	&options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
75	},
76	{
77	SSH_CMSG_AUTH_TIS, "challenge-response",
78	&options.challenge_response_authentication,
79	auth1_process_tis_challenge
80	},
81	{
82	SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
83	&options.challenge_response_authentication,
84	auth1_process_tis_response
85	},
86	{ -1, NULL, NULL, NULL}
87	};
88
89	static const struct AuthMethod1
90	*lookup_authmethod1(int type)
91	{
92	int i;
93
94	for (i = 0; auth1_methods[i].name != NULL; i++)
95	if (auth1_methods[i].type == type)
96	return (&(auth1_methods[i]));
97
98	return (NULL);
99	}
100
101	static char *
102	get_authname(int type)
103	{
104	const struct AuthMethod1 *a;
105	static char buf[64];
106
107	if ((a = lookup_authmethod1(type)) != NULL)
108	return (a->name);
109	snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
110	return (buf);
111	}
112
113	/ARGSUSED/
114	static int
115	auth1_process_password(Authctxt *authctxt)
116	{
117	int authenticated = 0;
118	char *password;
119	u_int dlen;
120
121	/*
122	* Read user password. It is in plain text, but was
123	* transmitted over the encrypted channel so it is
124	* not visible to an outside observer.
125	*/
126	password = packet_get_string(&dlen);
127	packet_check_eom();
128
129	/* Try authentication with the password. */
130	authenticated = PRIVSEP(auth_password(authctxt, password));
131
132	explicit_bzero(password, dlen);
133	free(password);
134
135	return (authenticated);
136	}
137
138	/ARGSUSED/
139	static int
140	auth1_process_rsa(Authctxt *authctxt)
141	{
142	int authenticated = 0;
143	BIGNUM *n;
144
145	/* RSA authentication requested. */
146	if ((n = BN_new()) == NULL)
147	fatal("do_authloop: BN_new failed");
148	packet_get_bignum(n);
149	packet_check_eom();
150	authenticated = auth_rsa(authctxt, n);
151	BN_clear_free(n);
152
153	return (authenticated);
154	}
155
156	/ARGSUSED/
157	static int
158	auth1_process_rhosts_rsa(Authctxt *authctxt)
159	{
160	int keybits, authenticated = 0;
161	u_int bits;
162	Key *client_host_key;
163	u_int ulen;
164
165	/*
166	* Get client user name. Note that we just have to
167	* trust the client; root on the client machine can
168	* claim to be any user.
169	*/
170	client_user = packet_get_cstring(&ulen);
171
172	/* Get the client host key. */
173	client_host_key = key_new(KEY_RSA1);
174	bits = packet_get_int();
175	packet_get_bignum(client_host_key->rsa->e);
176	packet_get_bignum(client_host_key->rsa->n);
177
178	keybits = BN_num_bits(client_host_key->rsa->n);
179	if (keybits < 0 \|\| bits != (u_int)keybits) {
180	verbose("Warning: keysize mismatch for client_host_key: "
181	"actual %d, announced %d",
182	BN_num_bits(client_host_key->rsa->n), bits);
183	}
184	packet_check_eom();
185
186	authenticated = auth_rhosts_rsa(authctxt, client_user,
187	client_host_key);
188	key_free(client_host_key);
189
190	auth_info(authctxt, "ruser %.100s", client_user);
191
192	return (authenticated);
193	}
194
195	/ARGSUSED/
196	static int
197	auth1_process_tis_challenge(Authctxt *authctxt)
198	{
199	char *challenge;
200
201	if ((challenge = get_challenge(authctxt)) == NULL)
202	return (0);
203
204	debug("sending challenge '%s'", challenge);
205	packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
206	packet_put_cstring(challenge);
207	free(challenge);
208	packet_send();
209	packet_write_wait();
210
211	return (-1);
212	}
213
214	/ARGSUSED/
215	static int
216	auth1_process_tis_response(Authctxt *authctxt)
217	{
218	int authenticated = 0;
219	char *response;
220	u_int dlen;
221
222	response = packet_get_string(&dlen);
223	packet_check_eom();
224	authenticated = verify_response(authctxt, response);
225	explicit_bzero(response, dlen);
226	free(response);
227
228	return (authenticated);
229	}
230
231	/*
232	* read packets, try to authenticate the user and
233	* return only if authentication is successful
234	*/
235	static void
236	do_authloop(Authctxt *authctxt)
237	{
238	int authenticated = 0;
239	int prev = 0, type = 0;
240	const struct AuthMethod1 *meth;
241
242	debug("Attempting authentication for %s%.100s.",
243	authctxt->valid ? "" : "invalid user ", authctxt->user);
244
245	/* If the user has no password, accept authentication immediately. */
246	if (options.permit_empty_passwd && options.password_authentication &&
247	#ifdef KRB5
248	(!options.kerberos_authentication \|\| options.kerberos_or_local_passwd) &&
249	#endif
250	PRIVSEP(auth_password(authctxt, ""))) {
251	#ifdef USE_PAM
252	if (options.use_pam && (PRIVSEP(do_pam_account())))
253	#endif
254	{
255	auth_log(authctxt, 1, 0, "without authentication",
256	NULL);
257	return;
258	}
259	}
260
261	/* Indicate that authentication is needed. */
262	packet_start(SSH_SMSG_FAILURE);
263	packet_send();
264	packet_write_wait();
265
266	for (;;) {
267	/* default to fail */
268	authenticated = 0;
269
270
271	/* Get a packet from the client. */
272	prev = type;
273	type = packet_read();
274
275	/*
276	* If we started challenge-response authentication but the
277	* next packet is not a response to our challenge, release
278	* the resources allocated by get_challenge() (which would
279	* normally have been released by verify_response() had we
280	* received such a response)
281	*/
282	if (prev == SSH_CMSG_AUTH_TIS &&
283	type != SSH_CMSG_AUTH_TIS_RESPONSE)
284	abandon_challenge_response(authctxt);
285
286	if (authctxt->failures >= options.max_authtries)
287	goto skip;
288	if ((meth = lookup_authmethod1(type)) == NULL) {
289	logit("Unknown message during authentication: "
290	"type %d", type);
291	goto skip;
292	}
293
294	if (!*(meth->enabled)) {
295	verbose("%s authentication disabled.", meth->name);
296	goto skip;
297	}
298
299	authenticated = meth->method(authctxt);
300	if (authenticated == -1)
301	continue; /* "postponed" */
302
303	#ifdef BSD_AUTH
304	if (authctxt->as) {
305	auth_close(authctxt->as);
306	authctxt->as = NULL;
307	}
308	#endif
309	if (!authctxt->valid && authenticated)
310	fatal("INTERNAL ERROR: authenticated invalid user %s",
311	authctxt->user);
312
313	#ifdef _UNICOS
314	if (authenticated && cray_access_denied(authctxt->user)) {
315	authenticated = 0;
316	fatal("Access denied for user %s.",authctxt->user);
317	}
318	#endif /* _UNICOS */
319
320	#ifndef HAVE_CYGWIN
321	/* Special handling for root */
322	if (authenticated && authctxt->pw->pw_uid == 0 &&
323	!auth_root_allowed(meth->name)) {
324	authenticated = 0;
325	# ifdef SSH_AUDIT_EVENTS
326	PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
327	# endif
328	}
329	#endif
330
331	#ifdef USE_PAM
332	if (options.use_pam && authenticated &&
333	!PRIVSEP(do_pam_account())) {
334	char *msg;
335	size_t len;
336
337	error("Access denied for user %s by PAM account "
338	"configuration", authctxt->user);
339	len = buffer_len(&loginmsg);
340	buffer_append(&loginmsg, "\0", 1);
341	msg = buffer_ptr(&loginmsg);
342	/* strip trailing newlines */
343	if (len > 0)
344	while (len > 0 && msg[--len] == '\n')
345	msg[len] = '\0';
346	else
347	msg = "Access denied.";
348	packet_disconnect("%s", msg);
349	}
350	#endif
351
352	skip:
353	/* Log before sending the reply */
354	auth_log(authctxt, authenticated, 0, get_authname(type), NULL);
355
356	free(client_user);
357	client_user = NULL;
358
359	if (authenticated)
360	return;
361
362	if (++authctxt->failures >= options.max_authtries) {
363	#ifdef SSH_AUDIT_EVENTS
364	PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
365	#endif
366	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
367	}
368
369	packet_start(SSH_SMSG_FAILURE);
370	packet_send();
371	packet_write_wait();
372	}
373	}
374
375	/*
376	* Performs authentication of an incoming connection. Session key has already
377	* been exchanged and encryption is enabled.
378	*/
379	void
380	do_authentication(Authctxt *authctxt)
381	{
382	u_int ulen;
383	char user, style = NULL;
384
385	/* Get the name of the user that we wish to log in as. */
386	packet_read_expect(SSH_CMSG_USER);
387
388	/* Get the user name. */
389	user = packet_get_cstring(&ulen);
390	packet_check_eom();
391
392	if ((style = strchr(user, ':')) != NULL)
393	*style++ = '\0';
394
395	authctxt->user = user;
396	authctxt->style = style;
397
398	/* Verify that the user is a valid user. */
399	if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
400	authctxt->valid = 1;
401	else {
402	debug("do_authentication: invalid user %s", user);
403	authctxt->pw = fakepw();
404	}
405
406	/* Configuration may have changed as a result of Match */
407	if (options.num_auth_methods != 0)
408	fatal("AuthenticationMethods is not supported with SSH "
409	"protocol 1");
410
411	setproctitle("%s%s", authctxt->valid ? user : "unknown",
412	use_privsep ? " [net]" : "");
413
414	#ifdef USE_PAM
415	if (options.use_pam)
416	PRIVSEP(start_pam(authctxt));
417	#endif
418
419	/*
420	* If we are not running as root, the user must have the same uid as
421	* the server.
422	*/
423	#ifndef HAVE_CYGWIN
424	if (!use_privsep && getuid() != 0 && authctxt->pw &&
425	authctxt->pw->pw_uid != getuid())
426	packet_disconnect("Cannot change user when server not running as root.");
427	#endif
428
429	/*
430	* Loop until the user has been authenticated or the connection is
431	* closed, do_authloop() returns only if authentication is successful
432	*/
433	do_authloop(authctxt);
434
435	/* The user has been authenticated and accepted. */
436	packet_start(SSH_SMSG_SUCCESS);
437	packet_send();
438	packet_write_wait();
439	}