Return to monitor_wrap.c CVS log

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refactor channels.c

Move static state to a "struct ssh_channels" that is allocated at
runtime and tracked as a member of struct ssh.

Explicitly pass "struct ssh" to all channels functions.

Replace use of the legacy packet APIs in channels.c.

Rework sshd_config PermitOpen handling: previously the configuration
parser would call directly into the channels layer. After the refactor
this is not possible, as the channels structures are allocated at
connection time and aren't available when the configuration is parsed.
The server config parser now tracks PermitOpen itself and explicitly
configures the channels code later.

ok markus@

/* $OpenBSD: monitor_wrap.c,v 1.93 2017/09/12 06:32:07 djm Exp $ */
/*
 * Copyright 2002 Niels Provos <provos@citi.umich.edu>
 * Copyright 2002 Markus Friedl <markus@openbsd.org>
 * 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 <sys/types.h>
#include <sys/uio.h>
#include <sys/queue.h>

#include <errno.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#ifdef WITH_OPENSSL
#include <openssl/bn.h>
#include <openssl/dh.h>
#endif

#include "xmalloc.h"
#include "ssh.h"
#ifdef WITH_OPENSSL
#include "dh.h"
#endif
#include "buffer.h"
#include "key.h"
#include "cipher.h"
#include "kex.h"
#include "hostfile.h"
#include "auth.h"
#include "auth-options.h"
#include "packet.h"
#include "mac.h"
#include "log.h"
#include <zlib.h>
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "atomicio.h"
#include "monitor_fdpass.h"
#include "misc.h"
#include "uuencode.h"

#include "channels.h"
#include "session.h"
#include "servconf.h"

#include "ssherr.h"

/* Imports */
extern z_stream incoming_stream;
extern z_stream outgoing_stream;
extern struct monitor *pmonitor;
extern Buffer loginmsg;
extern ServerOptions options;

void
mm_log_handler(LogLevel level, const char *msg, void *ctx)
{
	Buffer log_msg;
	struct monitor *mon = (struct monitor *)ctx;

	if (mon->m_log_sendfd == -1)
		fatal("%s: no log channel", __func__);

	buffer_init(&log_msg);
	/*
	 * Placeholder for packet length. Will be filled in with the actual
	 * packet length once the packet has been constucted. This saves
	 * fragile math.
	 */
	buffer_put_int(&log_msg, 0);

	buffer_put_int(&log_msg, level);
	buffer_put_cstring(&log_msg, msg);
	put_u32(buffer_ptr(&log_msg), buffer_len(&log_msg) - 4);
	if (atomicio(vwrite, mon->m_log_sendfd, buffer_ptr(&log_msg),
	    buffer_len(&log_msg)) != buffer_len(&log_msg))
		fatal("%s: write: %s", __func__, strerror(errno));
	buffer_free(&log_msg);
}

int
mm_is_monitor(void)
{
	/*
	 * m_pid is only set in the privileged part, and
	 * points to the unprivileged child.
	 */
	return (pmonitor && pmonitor->m_pid > 0);
}

void
mm_request_send(int sock, enum monitor_reqtype type, Buffer *m)
{
	u_int mlen = buffer_len(m);
	u_char buf[5];

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

	put_u32(buf, mlen + 1);
	buf[4] = (u_char) type;		/* 1st byte of payload is mesg-type */
	if (atomicio(vwrite, sock, buf, sizeof(buf)) != sizeof(buf))
		fatal("%s: write: %s", __func__, strerror(errno));
	if (atomicio(vwrite, sock, buffer_ptr(m), mlen) != mlen)
		fatal("%s: write: %s", __func__, strerror(errno));
}

void
mm_request_receive(int sock, Buffer *m)
{
	u_char buf[4];
	u_int msg_len;

	debug3("%s entering", __func__);

	if (atomicio(read, sock, buf, sizeof(buf)) != sizeof(buf)) {
		if (errno == EPIPE)
			cleanup_exit(255);
		fatal("%s: read: %s", __func__, strerror(errno));
	}
	msg_len = get_u32(buf);
	if (msg_len > 256 * 1024)
		fatal("%s: read: bad msg_len %d", __func__, msg_len);
	buffer_clear(m);
	buffer_append_space(m, msg_len);
	if (atomicio(read, sock, buffer_ptr(m), msg_len) != msg_len)
		fatal("%s: read: %s", __func__, strerror(errno));
}

void
mm_request_receive_expect(int sock, enum monitor_reqtype type, Buffer *m)
{
	u_char rtype;

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

	mm_request_receive(sock, m);
	rtype = buffer_get_char(m);
	if (rtype != type)
		fatal("%s: read: rtype %d != type %d", __func__,
		    rtype, type);
}

#ifdef WITH_OPENSSL
DH *
mm_choose_dh(int min, int nbits, int max)
{
	BIGNUM *p, *g;
	int success = 0;
	Buffer m;

	buffer_init(&m);
	buffer_put_int(&m, min);
	buffer_put_int(&m, nbits);
	buffer_put_int(&m, max);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_MODULI, &m);

	debug3("%s: waiting for MONITOR_ANS_MODULI", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_MODULI, &m);

	success = buffer_get_char(&m);
	if (success == 0)
		fatal("%s: MONITOR_ANS_MODULI failed", __func__);

	if ((p = BN_new()) == NULL)
		fatal("%s: BN_new failed", __func__);
	if ((g = BN_new()) == NULL)
		fatal("%s: BN_new failed", __func__);
	buffer_get_bignum2(&m, p);
	buffer_get_bignum2(&m, g);

	debug3("%s: remaining %d", __func__, buffer_len(&m));
	buffer_free(&m);

	return (dh_new_group(g, p));
}
#endif

int
mm_key_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
    const u_char *data, u_int datalen, const char *hostkey_alg)
{
	struct kex *kex = *pmonitor->m_pkex;
	Buffer m;

	debug3("%s entering", __func__);

	buffer_init(&m);
	buffer_put_int(&m, kex->host_key_index(key, 0, active_state));
	buffer_put_string(&m, data, datalen);
	buffer_put_cstring(&m, hostkey_alg);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_SIGN, &m);

	debug3("%s: waiting for MONITOR_ANS_SIGN", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_SIGN, &m);
	*sigp  = buffer_get_string(&m, lenp);
	buffer_free(&m);

	return (0);
}

struct passwd *
mm_getpwnamallow(const char *username)
{
	struct ssh *ssh = active_state;		/* XXX */
	Buffer m;
	struct passwd *pw;
	u_int len, i;
	ServerOptions *newopts;

	debug3("%s entering", __func__);

	buffer_init(&m);
	buffer_put_cstring(&m, username);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PWNAM, &m);

	debug3("%s: waiting for MONITOR_ANS_PWNAM", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PWNAM, &m);

	if (buffer_get_char(&m) == 0) {
		pw = NULL;
		goto out;
	}
	pw = buffer_get_string(&m, &len);
	if (len != sizeof(struct passwd))
		fatal("%s: struct passwd size mismatch", __func__);
	pw->pw_name = buffer_get_string(&m, NULL);
	pw->pw_passwd = buffer_get_string(&m, NULL);
	pw->pw_gecos = buffer_get_string(&m, NULL);
	pw->pw_class = buffer_get_string(&m, NULL);
	pw->pw_dir = buffer_get_string(&m, NULL);
	pw->pw_shell = buffer_get_string(&m, NULL);

out:
	/* copy options block as a Match directive may have changed some */
	newopts = buffer_get_string(&m, &len);
	if (len != sizeof(*newopts))
		fatal("%s: option block size mismatch", __func__);

#define M_CP_STROPT(x) do { \
		if (newopts->x != NULL) \
			newopts->x = buffer_get_string(&m, NULL); \
	} while (0)
#define M_CP_STRARRAYOPT(x, nx) do { \
		for (i = 0; i < newopts->nx; i++) \
			newopts->x[i] = buffer_get_string(&m, NULL); \
	} while (0)
	/* See comment in servconf.h */
	COPY_MATCH_STRING_OPTS();
#undef M_CP_STROPT
#undef M_CP_STRARRAYOPT

	copy_set_server_options(&options, newopts, 1);
	log_change_level(options.log_level);
	process_permitopen(ssh, &options);
	free(newopts);

	buffer_free(&m);

	return (pw);
}

char *
mm_auth2_read_banner(void)
{
	Buffer m;
	char *banner;

	debug3("%s entering", __func__);

	buffer_init(&m);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTH2_READ_BANNER, &m);
	buffer_clear(&m);

	mm_request_receive_expect(pmonitor->m_recvfd,
	    MONITOR_ANS_AUTH2_READ_BANNER, &m);
	banner = buffer_get_string(&m, NULL);
	buffer_free(&m);

	/* treat empty banner as missing banner */
	if (strlen(banner) == 0) {
		free(banner);
		banner = NULL;
	}
	return (banner);
}

/* Inform the privileged process about service and style */

void
mm_inform_authserv(char *service, char *style)
{
	Buffer m;

	debug3("%s entering", __func__);

	buffer_init(&m);
	buffer_put_cstring(&m, service);
	buffer_put_cstring(&m, style ? style : "");

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTHSERV, &m);

	buffer_free(&m);
}

/* Do the password authentication */
int
mm_auth_password(Authctxt *authctxt, char *password)
{
	Buffer m;
	int authenticated = 0;

	debug3("%s entering", __func__);

	buffer_init(&m);
	buffer_put_cstring(&m, password);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_AUTHPASSWORD, &m);

	debug3("%s: waiting for MONITOR_ANS_AUTHPASSWORD", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_AUTHPASSWORD, &m);

	authenticated = buffer_get_int(&m);

	buffer_free(&m);

	debug3("%s: user %sauthenticated",
	    __func__, authenticated ? "" : "not ");
	return (authenticated);
}

int
mm_user_key_allowed(struct passwd *pw, struct sshkey *key,
    int pubkey_auth_attempt)
{
	return (mm_key_allowed(MM_USERKEY, NULL, NULL, key,
	    pubkey_auth_attempt));
}

int
mm_hostbased_key_allowed(struct passwd *pw, const char *user, const char *host,
    struct sshkey *key)
{
	return (mm_key_allowed(MM_HOSTKEY, user, host, key, 0));
}

int
mm_key_allowed(enum mm_keytype type, const char *user, const char *host,
    struct sshkey *key, int pubkey_auth_attempt)
{
	Buffer m;
	u_char *blob;
	u_int len;
	int allowed = 0, have_forced = 0;

	debug3("%s entering", __func__);

	/* Convert the key to a blob and the pass it over */
	if (!key_to_blob(key, &blob, &len))
		return (0);

	buffer_init(&m);
	buffer_put_int(&m, type);
	buffer_put_cstring(&m, user ? user : "");
	buffer_put_cstring(&m, host ? host : "");
	buffer_put_string(&m, blob, len);
	buffer_put_int(&m, pubkey_auth_attempt);
	free(blob);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYALLOWED, &m);

	debug3("%s: waiting for MONITOR_ANS_KEYALLOWED", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_KEYALLOWED, &m);

	allowed = buffer_get_int(&m);

	/* fake forced command */
	auth_clear_options();
	have_forced = buffer_get_int(&m);
	forced_command = have_forced ? xstrdup("true") : NULL;

	buffer_free(&m);

	return (allowed);
}

/*
 * This key verify needs to send the key type along, because the
 * privileged parent makes the decision if the key is allowed
 * for authentication.
 */

int
mm_sshkey_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
    const u_char *data, size_t datalen, u_int compat)
{
	Buffer m;
	u_char *blob;
	u_int len;
	u_int encoded_ret = 0;

	debug3("%s entering", __func__);

	/* Convert the key to a blob and the pass it over */
	if (!key_to_blob(key, &blob, &len))
		return (0);

	buffer_init(&m);
	buffer_put_string(&m, blob, len);
	buffer_put_string(&m, sig, siglen);
	buffer_put_string(&m, data, datalen);
	free(blob);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYVERIFY, &m);

	debug3("%s: waiting for MONITOR_ANS_KEYVERIFY", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_KEYVERIFY, &m);

	encoded_ret = buffer_get_int(&m);

	buffer_free(&m);

	if (encoded_ret != 0)
		return SSH_ERR_SIGNATURE_INVALID;
	return 0;
}

void
mm_send_keystate(struct monitor *monitor)
{
	struct ssh *ssh = active_state;		/* XXX */
	struct sshbuf *m;
	int r;

	if ((m = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = ssh_packet_get_state(ssh, m)) != 0)
		fatal("%s: get_state failed: %s",
		    __func__, ssh_err(r));
	mm_request_send(monitor->m_recvfd, MONITOR_REQ_KEYEXPORT, m);
	debug3("%s: Finished sending state", __func__);
	sshbuf_free(m);
}

int
mm_pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
{
	Buffer m;
	char *p, *msg;
	int success = 0, tmp1 = -1, tmp2 = -1;

	/* Kludge: ensure there are fds free to receive the pty/tty */
	if ((tmp1 = dup(pmonitor->m_recvfd)) == -1 ||
	    (tmp2 = dup(pmonitor->m_recvfd)) == -1) {
		error("%s: cannot allocate fds for pty", __func__);
		if (tmp1 > 0)
			close(tmp1);
		if (tmp2 > 0)
			close(tmp2);
		return 0;
	}
	close(tmp1);
	close(tmp2);

	buffer_init(&m);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PTY, &m);

	debug3("%s: waiting for MONITOR_ANS_PTY", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PTY, &m);

	success = buffer_get_int(&m);
	if (success == 0) {
		debug3("%s: pty alloc failed", __func__);
		buffer_free(&m);
		return (0);
	}
	p = buffer_get_string(&m, NULL);
	msg = buffer_get_string(&m, NULL);
	buffer_free(&m);

	strlcpy(namebuf, p, namebuflen); /* Possible truncation */
	free(p);

	buffer_append(&loginmsg, msg, strlen(msg));
	free(msg);

	if ((*ptyfd = mm_receive_fd(pmonitor->m_recvfd)) == -1 ||
	    (*ttyfd = mm_receive_fd(pmonitor->m_recvfd)) == -1)
		fatal("%s: receive fds failed", __func__);

	/* Success */
	return (1);
}

void
mm_session_pty_cleanup2(Session *s)
{
	Buffer m;

	if (s->ttyfd == -1)
		return;
	buffer_init(&m);
	buffer_put_cstring(&m, s->tty);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PTYCLEANUP, &m);
	buffer_free(&m);

	/* closed dup'ed master */
	if (s->ptymaster != -1 && close(s->ptymaster) < 0)
		error("close(s->ptymaster/%d): %s",
		    s->ptymaster, strerror(errno));

	/* unlink pty from session */
	s->ttyfd = -1;
}

/* Request process termination */

void
mm_terminate(void)
{
	Buffer m;

	buffer_init(&m);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_TERM, &m);
	buffer_free(&m);
}

static void
mm_chall_setup(char **name, char **infotxt, u_int *numprompts,
    char ***prompts, u_int **echo_on)
{
	*name = xstrdup("");
	*infotxt = xstrdup("");
	*numprompts = 1;
	*prompts = xcalloc(*numprompts, sizeof(char *));
	*echo_on = xcalloc(*numprompts, sizeof(u_int));
	(*echo_on)[0] = 0;
}

int
mm_bsdauth_query(void *ctx, char **name, char **infotxt,
   u_int *numprompts, char ***prompts, u_int **echo_on)
{
	Buffer m;
	u_int success;
	char *challenge;

	debug3("%s: entering", __func__);

	buffer_init(&m);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_BSDAUTHQUERY, &m);

	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_BSDAUTHQUERY,
	    &m);
	success = buffer_get_int(&m);
	if (success == 0) {
		debug3("%s: no challenge", __func__);
		buffer_free(&m);
		return (-1);
	}

	/* Get the challenge, and format the response */
	challenge  = buffer_get_string(&m, NULL);
	buffer_free(&m);

	mm_chall_setup(name, infotxt, numprompts, prompts, echo_on);
	(*prompts)[0] = challenge;

	debug3("%s: received challenge: %s", __func__, challenge);

	return (0);
}

int
mm_bsdauth_respond(void *ctx, u_int numresponses, char **responses)
{
	Buffer m;
	int authok;

	debug3("%s: entering", __func__);
	if (numresponses != 1)
		return (-1);

	buffer_init(&m);
	buffer_put_cstring(&m, responses[0]);
	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_BSDAUTHRESPOND, &m);

	mm_request_receive_expect(pmonitor->m_recvfd,
	    MONITOR_ANS_BSDAUTHRESPOND, &m);

	authok = buffer_get_int(&m);
	buffer_free(&m);

	return ((authok == 0) ? -1 : 0);
}

#ifdef GSSAPI
OM_uint32
mm_ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID goid)
{
	Buffer m;
	OM_uint32 major;

	/* Client doesn't get to see the context */
	*ctx = NULL;

	buffer_init(&m);
	buffer_put_string(&m, goid->elements, goid->length);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSETUP, &m);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSETUP, &m);

	major = buffer_get_int(&m);

	buffer_free(&m);
	return (major);
}

OM_uint32
mm_ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *in,
    gss_buffer_desc *out, OM_uint32 *flags)
{
	Buffer m;
	OM_uint32 major;
	u_int len;

	buffer_init(&m);
	buffer_put_string(&m, in->value, in->length);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSSTEP, &m);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSSTEP, &m);

	major = buffer_get_int(&m);
	out->value = buffer_get_string(&m, &len);
	out->length = len;
	if (flags)
		*flags = buffer_get_int(&m);

	buffer_free(&m);

	return (major);
}

OM_uint32
mm_ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
{
	Buffer m;
	OM_uint32 major;

	buffer_init(&m);
	buffer_put_string(&m, gssbuf->value, gssbuf->length);
	buffer_put_string(&m, gssmic->value, gssmic->length);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSCHECKMIC, &m);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSCHECKMIC,
	    &m);

	major = buffer_get_int(&m);
	buffer_free(&m);
	return(major);
}

int
mm_ssh_gssapi_userok(char *user)
{
	Buffer m;
	int authenticated = 0;

	buffer_init(&m);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_GSSUSEROK, &m);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_GSSUSEROK,
				  &m);

	authenticated = buffer_get_int(&m);

	buffer_free(&m);
	debug3("%s: user %sauthenticated",__func__, authenticated ? "" : "not ");
	return (authenticated);
}
#endif /* GSSAPI */