monitor.c

OpenSSH 是 SSH （Secure SHell） 协议的免费开源实现。它用安全、加密的网络连接工具代替了 telnet、ftp、 rlogin、rsh 和 rcp 工具。OpenSSH 支持

/*
 * Copyright 2002 Niels Provos <[e-mail]>
 * Copyright 2002 Markus Friedl <[e-mail]>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: monitor.c,v 1.62 2005/01/30 11:18:08 dtucker Exp $");

#include <openssl/dh.h>

#ifdef SKEY
#include <skey.h>
#endif

#include "ssh.h"
#include "auth.h"
#include "kex.h"
#include "dh.h"
#ifdef TARGET_OS_MAC	/* XXX Broken krb5 headers on Mac */
#undef TARGET_OS_MAC
#include "zlib.h"
#define TARGET_OS_MAC 1
#else
#include "zlib.h"
#endif
#include "packet.h"
#include "auth-options.h"
#include "sshpty.h"
#include "channels.h"
#include "session.h"
#include "sshlogin.h"
#include "canohost.h"
#include "log.h"
#include "servconf.h"
#include "monitor.h"
#include "monitor_mm.h"
#include "monitor_wrap.h"
#include "monitor_fdpass.h"
#include "xmalloc.h"
#include "misc.h"
#include "buffer.h"
#include "bufaux.h"
#include "compat.h"
#include "ssh2.h"

#ifdef GSSAPI
#include "ssh-gss.h"
static Gssctxt *gsscontext = NULL;
#endif

/* Imports */
extern ServerOptions options;
extern u_int utmp_len;
extern Newkeys *current_keys[];
extern z_stream incoming_stream;
extern z_stream outgoing_stream;
extern u_char session_id[];
extern Buffer input, output;
extern Buffer auth_debug;
extern int auth_debug_init;
extern Buffer loginmsg;

/* State exported from the child */

struct {
	z_stream incoming;
	z_stream outgoing;
	u_char *keyin;
	u_int keyinlen;
	u_char *keyout;
	u_int keyoutlen;
	u_char *ivin;
	u_int ivinlen;
	u_char *ivout;
	u_int ivoutlen;
	u_char *ssh1key;
	u_int ssh1keylen;
	int ssh1cipher;
	int ssh1protoflags;
	u_char *input;
	u_int ilen;
	u_char *output;
	u_int olen;
} child_state;

/* Functions on the monitor that answer unprivileged requests */

int mm_answer_moduli(int, Buffer *);
int mm_answer_sign(int, Buffer *);
int mm_answer_pwnamallow(int, Buffer *);
int mm_answer_auth2_read_banner(int, Buffer *);
int mm_answer_authserv(int, Buffer *);
int mm_answer_authpassword(int, Buffer *);
int mm_answer_bsdauthquery(int, Buffer *);
int mm_answer_bsdauthrespond(int, Buffer *);
int mm_answer_skeyquery(int, Buffer *);
int mm_answer_skeyrespond(int, Buffer *);
int mm_answer_keyallowed(int, Buffer *);
int mm_answer_keyverify(int, Buffer *);
int mm_answer_pty(int, Buffer *);
int mm_answer_pty_cleanup(int, Buffer *);
int mm_answer_term(int, Buffer *);
int mm_answer_rsa_keyallowed(int, Buffer *);
int mm_answer_rsa_challenge(int, Buffer *);
int mm_answer_rsa_response(int, Buffer *);
int mm_answer_sesskey(int, Buffer *);
int mm_answer_sessid(int, Buffer *);

#ifdef USE_PAM
int mm_answer_pam_start(int, Buffer *);
int mm_answer_pam_account(int, Buffer *);
int mm_answer_pam_init_ctx(int, Buffer *);
int mm_answer_pam_query(int, Buffer *);
int mm_answer_pam_respond(int, Buffer *);
int mm_answer_pam_free_ctx(int, Buffer *);
#endif

#ifdef GSSAPI
int mm_answer_gss_setup_ctx(int, Buffer *);
int mm_answer_gss_accept_ctx(int, Buffer *);
int mm_answer_gss_userok(int, Buffer *);
int mm_answer_gss_checkmic(int, Buffer *);
#endif

#ifdef SSH_AUDIT_EVENTS
int mm_answer_audit_event(int, Buffer *);
int mm_answer_audit_command(int, Buffer *);
#endif

static Authctxt *authctxt;
static BIGNUM *ssh1_challenge = NULL;	/* used for ssh1 rsa auth */

/* local state for key verify */
static u_char *key_blob = NULL;
static u_int key_bloblen = 0;
static int key_blobtype = MM_NOKEY;
static char *hostbased_cuser = NULL;
static char *hostbased_chost = NULL;
static char *auth_method = "unknown";
static u_int session_id2_len = 0;
static u_char *session_id2 = NULL;
static pid_t monitor_child_pid;

struct mon_table {
	enum monitor_reqtype type;
	int flags;
	int (*f)(int, Buffer *);
};

#define MON_ISAUTH	0x0004	/* Required for Authentication */
#define MON_AUTHDECIDE	0x0008	/* Decides Authentication */
#define MON_ONCE	0x0010	/* Disable after calling */

#define MON_AUTH	(MON_ISAUTH|MON_AUTHDECIDE)

#define MON_PERMIT	0x1000	/* Request is permitted */

struct mon_table mon_dispatch_proto20[] = {
    {MONITOR_REQ_MODULI, MON_ONCE, mm_answer_moduli},
    {MONITOR_REQ_SIGN, MON_ONCE, mm_answer_sign},
    {MONITOR_REQ_PWNAM, MON_ONCE, mm_answer_pwnamallow},
    {MONITOR_REQ_AUTHSERV, MON_ONCE, mm_answer_authserv},
    {MONITOR_REQ_AUTH2_READ_BANNER, MON_ONCE, mm_answer_auth2_read_banner},
    {MONITOR_REQ_AUTHPASSWORD, MON_AUTH, mm_answer_authpassword},
#ifdef USE_PAM
    {MONITOR_REQ_PAM_START, MON_ONCE, mm_answer_pam_start},
    {MONITOR_REQ_PAM_ACCOUNT, 0, mm_answer_pam_account},
    {MONITOR_REQ_PAM_INIT_CTX, MON_ISAUTH, mm_answer_pam_init_ctx},
    {MONITOR_REQ_PAM_QUERY, MON_ISAUTH, mm_answer_pam_query},
    {MONITOR_REQ_PAM_RESPOND, MON_ISAUTH, mm_answer_pam_respond},
    {MONITOR_REQ_PAM_FREE_CTX, MON_ONCE|MON_AUTHDECIDE, mm_answer_pam_free_ctx},
#endif
#ifdef SSH_AUDIT_EVENTS
    {MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
#endif
#ifdef BSD_AUTH
    {MONITOR_REQ_BSDAUTHQUERY, MON_ISAUTH, mm_answer_bsdauthquery},
    {MONITOR_REQ_BSDAUTHRESPOND, MON_AUTH,mm_answer_bsdauthrespond},
#endif
#ifdef SKEY
    {MONITOR_REQ_SKEYQUERY, MON_ISAUTH, mm_answer_skeyquery},
    {MONITOR_REQ_SKEYRESPOND, MON_AUTH, mm_answer_skeyrespond},
#endif
    {MONITOR_REQ_KEYALLOWED, MON_ISAUTH, mm_answer_keyallowed},
    {MONITOR_REQ_KEYVERIFY, MON_AUTH, mm_answer_keyverify},
#ifdef GSSAPI
    {MONITOR_REQ_GSSSETUP, MON_ISAUTH, mm_answer_gss_setup_ctx},
    {MONITOR_REQ_GSSSTEP, MON_ISAUTH, mm_answer_gss_accept_ctx},
    {MONITOR_REQ_GSSUSEROK, MON_AUTH, mm_answer_gss_userok},
    {MONITOR_REQ_GSSCHECKMIC, MON_ISAUTH, mm_answer_gss_checkmic},
#endif
    {0, 0, NULL}
};

struct mon_table mon_dispatch_postauth20[] = {
    {MONITOR_REQ_MODULI, 0, mm_answer_moduli},
    {MONITOR_REQ_SIGN, 0, mm_answer_sign},
    {MONITOR_REQ_PTY, 0, mm_answer_pty},
    {MONITOR_REQ_PTYCLEANUP, 0, mm_answer_pty_cleanup},
    {MONITOR_REQ_TERM, 0, mm_answer_term},
#ifdef SSH_AUDIT_EVENTS
    {MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
    {MONITOR_REQ_AUDIT_COMMAND, MON_PERMIT, mm_answer_audit_command},
#endif
    {0, 0, NULL}
};

struct mon_table mon_dispatch_proto15[] = {
    {MONITOR_REQ_PWNAM, MON_ONCE, mm_answer_pwnamallow},
    {MONITOR_REQ_SESSKEY, MON_ONCE, mm_answer_sesskey},
    {MONITOR_REQ_SESSID, MON_ONCE, mm_answer_sessid},
    {MONITOR_REQ_AUTHPASSWORD, MON_AUTH, mm_answer_authpassword},
    {MONITOR_REQ_RSAKEYALLOWED, MON_ISAUTH, mm_answer_rsa_keyallowed},
    {MONITOR_REQ_KEYALLOWED, MON_ISAUTH, mm_answer_keyallowed},
    {MONITOR_REQ_RSACHALLENGE, MON_ONCE, mm_answer_rsa_challenge},
    {MONITOR_REQ_RSARESPONSE, MON_ONCE|MON_AUTHDECIDE, mm_answer_rsa_response},
#ifdef BSD_AUTH
    {MONITOR_REQ_BSDAUTHQUERY, MON_ISAUTH, mm_answer_bsdauthquery},
    {MONITOR_REQ_BSDAUTHRESPOND, MON_AUTH,mm_answer_bsdauthrespond},
#endif
#ifdef SKEY
    {MONITOR_REQ_SKEYQUERY, MON_ISAUTH, mm_answer_skeyquery},
    {MONITOR_REQ_SKEYRESPOND, MON_AUTH, mm_answer_skeyrespond},
#endif
#ifdef USE_PAM
    {MONITOR_REQ_PAM_START, MON_ONCE, mm_answer_pam_start},
    {MONITOR_REQ_PAM_ACCOUNT, 0, mm_answer_pam_account},
    {MONITOR_REQ_PAM_INIT_CTX, MON_ISAUTH, mm_answer_pam_init_ctx},
    {MONITOR_REQ_PAM_QUERY, MON_ISAUTH, mm_answer_pam_query},
    {MONITOR_REQ_PAM_RESPOND, MON_ISAUTH, mm_answer_pam_respond},
    {MONITOR_REQ_PAM_FREE_CTX, MON_ONCE|MON_AUTHDECIDE, mm_answer_pam_free_ctx},
#endif
#ifdef SSH_AUDIT_EVENTS
    {MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
#endif
    {0, 0, NULL}
};

struct mon_table mon_dispatch_postauth15[] = {
    {MONITOR_REQ_PTY, MON_ONCE, mm_answer_pty},
    {MONITOR_REQ_PTYCLEANUP, MON_ONCE, mm_answer_pty_cleanup},
    {MONITOR_REQ_TERM, 0, mm_answer_term},
#ifdef SSH_AUDIT_EVENTS
    {MONITOR_REQ_AUDIT_EVENT, MON_PERMIT, mm_answer_audit_event},
    {MONITOR_REQ_AUDIT_COMMAND, MON_ONCE, mm_answer_audit_command},
#endif
    {0, 0, NULL}
};

struct mon_table *mon_dispatch;

/* Specifies if a certain message is allowed at the moment */

static void
monitor_permit(struct mon_table *ent, enum monitor_reqtype type, int permit)
{
	while (ent->f != NULL) {
		if (ent->type == type) {
			ent->flags &= ~MON_PERMIT;
			ent->flags |= permit ? MON_PERMIT : 0;
			return;
		}
		ent++;
	}
}

static void
monitor_permit_authentications(int permit)
{
	struct mon_table *ent = mon_dispatch;

	while (ent->f != NULL) {
		if (ent->flags & MON_AUTH) {
			ent->flags &= ~MON_PERMIT;
			ent->flags |= permit ? MON_PERMIT : 0;
		}
		ent++;
	}
}

void
monitor_child_preauth(Authctxt *_authctxt, struct monitor *pmonitor)
{
	struct mon_table *ent;
	int authenticated = 0;

	debug3("preauth child monitor started");

	authctxt = _authctxt;
	memset(authctxt, 0, sizeof(*authctxt));

	if (compat20) {
		mon_dispatch = mon_dispatch_proto20;

		/* Permit requests for moduli and signatures */
		monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
		monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
	} else {
		mon_dispatch = mon_dispatch_proto15;

		monitor_permit(mon_dispatch, MONITOR_REQ_SESSKEY, 1);
	}

	/* The first few requests do not require asynchronous access */
	while (!authenticated) {
		authenticated = monitor_read(pmonitor, mon_dispatch, &ent);
		if (authenticated) {
			if (!(ent->flags & MON_AUTHDECIDE))
				fatal("%s: unexpected authentication from %d",
				    __func__, ent->type);
			if (authctxt->pw->pw_uid == 0 &&
			    !auth_root_allowed(auth_method))
				authenticated = 0;
#ifdef USE_PAM
			/* PAM needs to perform account checks after auth */
			if (options.use_pam && authenticated) {
				Buffer m;

				buffer_init(&m);
				mm_request_receive_expect(pmonitor->m_sendfd,
				    MONITOR_REQ_PAM_ACCOUNT, &m);
				authenticated = mm_answer_pam_account(pmonitor->m_sendfd, &m);
				buffer_free(&m);
			}
#endif
		}

		if (ent->flags & MON_AUTHDECIDE) {
			auth_log(authctxt, authenticated, auth_method,
			    compat20 ? " ssh2" : "");
			if (!authenticated)
				authctxt->failures++;
		}
	}

	if (!authctxt->valid)
		fatal("%s: authenticated invalid user", __func__);

	debug("%s: %s has been authenticated by privileged process",
	    __func__, authctxt->user);

	mm_get_keystate(pmonitor);
}

static void
monitor_set_child_handler(pid_t pid)
{
	monitor_child_pid = pid;
}

static void
monitor_child_handler(int sig)
{
	kill(monitor_child_pid, sig);
}

void
monitor_child_postauth(struct monitor *pmonitor)
{
	monitor_set_child_handler(pmonitor->m_pid);
	signal(SIGHUP, &monitor_child_handler);
	signal(SIGTERM, &monitor_child_handler);

	if (compat20) {
		mon_dispatch = mon_dispatch_postauth20;

		/* Permit requests for moduli and signatures */
		monitor_permit(mon_dispatch, MONITOR_REQ_MODULI, 1);
		monitor_permit(mon_dispatch, MONITOR_REQ_SIGN, 1);
		monitor_permit(mon_dispatch, MONITOR_REQ_TERM, 1);
	} else {
		mon_dispatch = mon_dispatch_postauth15;
		monitor_permit(mon_dispatch, MONITOR_REQ_TERM, 1);
	}
	if (!no_pty_flag) {
		monitor_permit(mon_dispatch, MONITOR_REQ_PTY, 1);
		monitor_permit(mon_dispatch, MONITOR_REQ_PTYCLEANUP, 1);
	}

	for (;;)
		monitor_read(pmonitor, mon_dispatch, NULL);
}

void
monitor_sync(struct monitor *pmonitor)
{
	if (options.compression) {
		/* The member allocation is not visible, so sync it */
		mm_share_sync(&pmonitor->m_zlib, &pmonitor->m_zback);
	}
}

int
monitor_read(struct monitor *pmonitor, struct mon_table *ent,
    struct mon_table **pent)
{
	Buffer m;
	int ret;
	u_char type;

	buffer_init(&m);

	mm_request_receive(pmonitor->m_sendfd, &m);
	type = buffer_get_char(&m);

	debug3("%s: checking request %d", __func__, type);

	while (ent->f != NULL) {
		if (ent->type == type)
			break;
		ent++;
	}

	if (ent->f != NULL) {
		if (!(ent->flags & MON_PERMIT))
			fatal("%s: unpermitted request %d", __func__,
			    type);
		ret = (*ent->f)(pmonitor->m_sendfd, &m);
		buffer_free(&m);

		/* The child may use this request only once, disable it */
		if (ent->flags & MON_ONCE) {
			debug2("%s: %d used once, disabling now", __func__,
			    type);
			ent->flags &= ~MON_PERMIT;
		}

		if (pent != NULL)
			*pent = ent;

		return ret;
	}

	fatal("%s: unsupported request: %d", __func__, type);

	/* NOTREACHED */
	return (-1);
}

/* allowed key state */
static int
monitor_allowed_key(u_char *blob, u_int bloblen)
{
	/* make sure key is allowed */
	if (key_blob == NULL || key_bloblen != bloblen ||
	    memcmp(key_blob, blob, key_bloblen))
		return (0);
	return (1);
}

static void
monitor_reset_key_state(void)
{
	/* reset state */
	if (key_blob != NULL)
		xfree(key_blob);
	if (hostbased_cuser != NULL)
		xfree(hostbased_cuser);
	if (hostbased_chost != NULL)