view sshpty.c @ 1629:258b57b208ae

Fix for issue successfull login of disabled user (#78) This commit introduces fix for scenario: 1. Root login disabled on dropbear 2. PAM authentication model enabled While login as root user, after prompt for password user is being notified about login failrue, but after second attempt of prompt for password within same session, login becames succesfull. Signed-off-by: Pawel Rapkiewicz <[email protected]>
author vincentto13 <33652988+vincentto13@users.noreply.github.com>
date Wed, 20 Mar 2019 15:03:40 +0100
parents 523be406edc4
children
line wrap: on
line source

/*
 * Dropbear - a SSH2 server
 *
 * Copied from OpenSSH-3.5p1 source, modified by Matt Johnston 2003
 * 
 * Author: Tatu Ylonen <[email protected]>
 * Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
 *                    All rights reserved
 * Allocating a pseudo-terminal, and making it the controlling tty.
 *
 * 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".
 */

/*RCSID("OpenBSD: sshpty.c,v 1.7 2002/06/24 17:57:20 deraadt Exp ");*/

#include "includes.h"
#include "dbutil.h"
#include "errno.h"
#include "sshpty.h"

/* Pty allocated with _getpty gets broken if we do I_PUSH:es to it. */
#if defined(HAVE__GETPTY) || defined(HAVE_OPENPTY)
#undef HAVE_DEV_PTMX
#endif

#ifdef HAVE_PTY_H
# include <pty.h>
#endif
#if defined(USE_DEV_PTMX) && defined(HAVE_STROPTS_H)
# include <stropts.h>
#endif

#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif

/*
 * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
 * nonzero if a pty was successfully allocated.  On success, open file
 * descriptors for the pty and tty sides and the name of the tty side are
 * returned (the buffer must be able to hold at least 64 characters).
 */

int
pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
{
#if defined(HAVE_OPENPTY)
	/* exists in recent (4.4) BSDs and OSF/1 */
	char *name;
	int i;

	i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
	if (i < 0) {
		dropbear_log(LOG_WARNING, 
				"pty_allocate: openpty: %.100s", strerror(errno));
		return 0;
	}
	name = ttyname(*ttyfd);
	if (!name) {
		dropbear_exit("ttyname fails for openpty device");
	}

	strlcpy(namebuf, name, namebuflen);	/* possible truncation */
	return 1;
#else /* HAVE_OPENPTY */
#ifdef HAVE__GETPTY
	/*
	 * _getpty(3) exists in SGI Irix 4.x, 5.x & 6.x -- it generates more
	 * pty's automagically when needed
	 */
	char *slave;

	slave = _getpty(ptyfd, O_RDWR, 0622, 0);
	if (slave == NULL) {
		dropbear_log(LOG_WARNING,
				"pty_allocate: _getpty: %.100s", strerror(errno));
		return 0;
	}
	strlcpy(namebuf, slave, namebuflen);
	/* Open the slave side. */
	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
	if (*ttyfd < 0) {
		dropbear_log(LOG_WARNING,
				"pty_allocate error: ttyftd open error");
		close(*ptyfd);
		return 0;
	}
	return 1;
#else /* HAVE__GETPTY */
#if defined(USE_DEV_PTMX)
	/*
	 * This code is used e.g. on Solaris 2.x.  (Note that Solaris 2.3
	 * also has bsd-style ptys, but they simply do not work.)
	 *
	 * Linux systems may have the /dev/ptmx device, but this code won't work.
	 */
	int ptm;
	char *pts;

	ptm = open("/dev/ptmx", O_RDWR | O_NOCTTY);
	if (ptm < 0) {
		dropbear_log(LOG_WARNING,
				"pty_allocate: /dev/ptmx: %.100s", strerror(errno));
		return 0;
	}
	if (grantpt(ptm) < 0) {
		dropbear_log(LOG_WARNING,
				"grantpt: %.100s", strerror(errno));
		return 0;
	}
	if (unlockpt(ptm) < 0) {
		dropbear_log(LOG_WARNING,
				"unlockpt: %.100s", strerror(errno));
		return 0;
	}
	pts = ptsname(ptm);
	if (pts == NULL) {
		dropbear_log(LOG_WARNING,
				"Slave pty side name could not be obtained.");
	}
	strlcpy(namebuf, pts, namebuflen);
	*ptyfd = ptm;

	/* Open the slave side. */
	*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
	if (*ttyfd < 0) {
		dropbear_log(LOG_ERR,
			"error opening pts %.100s: %.100s", namebuf, strerror(errno));
		close(*ptyfd);
		return 0;
	}
#if !defined(HAVE_CYGWIN) && defined(I_PUSH)
	/*
	 * Push the appropriate streams modules, as described in Solaris pts(7).
	 * HP-UX pts(7) doesn't have ttcompat module.
	 */
	if (ioctl(*ttyfd, I_PUSH, "ptem") < 0) {
		dropbear_log(LOG_WARNING,
				"ioctl I_PUSH ptem: %.100s", strerror(errno));
	}
	if (ioctl(*ttyfd, I_PUSH, "ldterm") < 0) {
		dropbear_log(LOG_WARNING,
			"ioctl I_PUSH ldterm: %.100s", strerror(errno));
	}
#ifndef __hpux
	if (ioctl(*ttyfd, I_PUSH, "ttcompat") < 0) {
		dropbear_log(LOG_WARNING,
			"ioctl I_PUSH ttcompat: %.100s", strerror(errno));
	}
#endif
#endif
	return 1;
#else /* USE_DEV_PTMX */
#ifdef HAVE_DEV_PTS_AND_PTC
	/* AIX-style pty code. */
	const char *name;

	*ptyfd = open("/dev/ptc", O_RDWR | O_NOCTTY);
	if (*ptyfd < 0) {
		dropbear_log(LOG_ERR,
			"Could not open /dev/ptc: %.100s", strerror(errno));
		return 0;
	}
	name = ttyname(*ptyfd);
	if (!name) {
		dropbear_exit("ttyname fails for /dev/ptc device");
	}
	strlcpy(namebuf, name, namebuflen);
	*ttyfd = open(name, O_RDWR | O_NOCTTY);
	if (*ttyfd < 0) {
		dropbear_log(LOG_ERR,
			"Could not open pty slave side %.100s: %.100s",
		    name, strerror(errno));
		close(*ptyfd);
		return 0;
	}
	return 1;
#else /* HAVE_DEV_PTS_AND_PTC */

	/* BSD-style pty code. */
	char buf[64];
	int i;
	const char *ptymajors = "pqrstuvwxyzabcdefghijklmnoABCDEFGHIJKLMNOPQRSTUVWXYZ";
	const char *ptyminors = "0123456789abcdef";
	int num_minors = strlen(ptyminors);
	int num_ptys = strlen(ptymajors) * num_minors;
	struct termios tio;

	for (i = 0; i < num_ptys; i++) {
		snprintf(buf, sizeof buf, "/dev/pty%c%c", ptymajors[i / num_minors],
			 ptyminors[i % num_minors]);
		snprintf(namebuf, namebuflen, "/dev/tty%c%c",
		    ptymajors[i / num_minors], ptyminors[i % num_minors]);

		*ptyfd = open(buf, O_RDWR | O_NOCTTY);
		if (*ptyfd < 0) {
			/* Try SCO style naming */
			snprintf(buf, sizeof buf, "/dev/ptyp%d", i);
			snprintf(namebuf, namebuflen, "/dev/ttyp%d", i);
			*ptyfd = open(buf, O_RDWR | O_NOCTTY);
			if (*ptyfd < 0) {
				continue;
			}
		}

		/* Open the slave side. */
		*ttyfd = open(namebuf, O_RDWR | O_NOCTTY);
		if (*ttyfd < 0) {
			dropbear_log(LOG_ERR,
				"pty_allocate: %.100s: %.100s", namebuf, strerror(errno));
			close(*ptyfd);
			return 0;
		}
		/* set tty modes to a sane state for broken clients */
		if (tcgetattr(*ptyfd, &tio) < 0) {
			dropbear_log(LOG_WARNING,
				"ptyallocate: tty modes failed: %.100s", strerror(errno));
		} else {
			tio.c_lflag |= (ECHO | ISIG | ICANON);
			tio.c_oflag |= (OPOST | ONLCR);
			tio.c_iflag |= ICRNL;

			/* Set the new modes for the terminal. */
			if (tcsetattr(*ptyfd, TCSANOW, &tio) < 0) {
				dropbear_log(LOG_WARNING,
					"Setting tty modes for pty failed: %.100s",
					strerror(errno));
			}
		}

		return 1;
	}
	dropbear_log(LOG_WARNING, "Failed to open any /dev/pty?? devices");
	return 0;
#endif /* HAVE_DEV_PTS_AND_PTC */
#endif /* USE_DEV_PTMX */
#endif /* HAVE__GETPTY */
#endif /* HAVE_OPENPTY */
}

/* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */

void
pty_release(const char *tty_name)
{
	if (chown(tty_name, (uid_t) 0, (gid_t) 0) < 0
			&& (errno != ENOENT)) {
		dropbear_log(LOG_ERR,
				"chown %.100s 0 0 failed: %.100s", tty_name, strerror(errno));
	}
	if (chmod(tty_name, (mode_t) 0666) < 0
			&& (errno != ENOENT)) {
		dropbear_log(LOG_ERR,
			"chmod %.100s 0666 failed: %.100s", tty_name, strerror(errno));
	}
}

/* Makes the tty the processes controlling tty and sets it to sane modes. */

void
pty_make_controlling_tty(int *ttyfd, const char *tty_name)
{
	int fd;
#ifdef USE_VHANGUP
	void *old;
#endif /* USE_VHANGUP */

	/* Solaris has a problem with TIOCNOTTY for a bg process, so
	 * we disable the signal which would STOP the process - matt */
	signal(SIGTTOU, SIG_IGN);

	/* First disconnect from the old controlling tty. */
#ifdef TIOCNOTTY
	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
	if (fd >= 0) {
		(void) ioctl(fd, TIOCNOTTY, NULL);
		close(fd);
	}
#endif /* TIOCNOTTY */
	if (setsid() < 0) {
		dropbear_log(LOG_ERR,
			"setsid: %.100s", strerror(errno));
	}

	/*
	 * Verify that we are successfully disconnected from the controlling
	 * tty.
	 */
	fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
	if (fd >= 0) {
		dropbear_log(LOG_ERR,
				"Failed to disconnect from controlling tty.\n");
		close(fd);
	}
	/* Make it our controlling tty. */
#ifdef TIOCSCTTY
	if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) {
		dropbear_log(LOG_ERR,
			"ioctl(TIOCSCTTY): %.100s", strerror(errno));
	}
#endif /* TIOCSCTTY */
#ifdef HAVE_NEWS4
	if (setpgrp(0,0) < 0) {
		dropbear_log(LOG_ERR,
			error("SETPGRP %s",strerror(errno)));
	}
#endif /* HAVE_NEWS4 */
#ifdef USE_VHANGUP
	old = mysignal(SIGHUP, SIG_IGN);
	vhangup();
	mysignal(SIGHUP, old);
#endif /* USE_VHANGUP */
	fd = open(tty_name, O_RDWR);
	if (fd < 0) {
		dropbear_log(LOG_ERR,
			"%.100s: %.100s", tty_name, strerror(errno));
	} else {
#ifdef USE_VHANGUP
		close(*ttyfd);
		*ttyfd = fd;
#else /* USE_VHANGUP */
		close(fd);
#endif /* USE_VHANGUP */
	}
	/* Verify that we now have a controlling tty. */
	fd = open(_PATH_TTY, O_WRONLY);
	if (fd < 0) {
		dropbear_log(LOG_ERR,
			"open /dev/tty failed - could not set controlling tty: %.100s",
		    strerror(errno));
	} else {
		close(fd);
	}
}

/* Changes the window size associated with the pty. */

void
pty_change_window_size(int ptyfd, int row, int col,
	int xpixel, int ypixel)
{
	struct winsize w;

	w.ws_row = row;
	w.ws_col = col;
	w.ws_xpixel = xpixel;
	w.ws_ypixel = ypixel;
	(void) ioctl(ptyfd, TIOCSWINSZ, &w);
}

void
pty_setowner(struct passwd *pw, const char *tty_name)
{
	struct group *grp;
	gid_t gid;
	mode_t mode;
	struct stat st;

	/* Determine the group to make the owner of the tty. */
	grp = getgrnam("tty");
	if (grp) {
		gid = grp->gr_gid;
		mode = S_IRUSR | S_IWUSR | S_IWGRP;
	} else {
		gid = pw->pw_gid;
		mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
	}

	/*
	 * Change owner and mode of the tty as required.
	 * Warn but continue if filesystem is read-only and the uids match/
	 * tty is owned by root.
	 */
	if (stat(tty_name, &st)) {
		dropbear_exit("pty_setowner: stat(%.101s) failed: %.100s",
				tty_name, strerror(errno));
	}

	if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
		if (chown(tty_name, pw->pw_uid, gid) < 0) {
			if (errno == EROFS &&
			    (st.st_uid == pw->pw_uid || st.st_uid == 0)) {
				dropbear_log(LOG_ERR,
					"chown(%.100s, %u, %u) failed: %.100s",
						tty_name, (unsigned int)pw->pw_uid, (unsigned int)gid,
						strerror(errno));
			} else {
				dropbear_exit("chown(%.100s, %u, %u) failed: %.100s",
				    tty_name, (unsigned int)pw->pw_uid, (unsigned int)gid,
				    strerror(errno));
			}
		}
	}

	if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
		if (chmod(tty_name, mode) < 0) {
			if (errno == EROFS &&
			    (st.st_mode & (S_IRGRP | S_IROTH)) == 0) {
				dropbear_log(LOG_ERR,
					"chmod(%.100s, 0%o) failed: %.100s",
					tty_name, mode, strerror(errno));
			} else {
				dropbear_exit("chmod(%.100s, 0%o) failed: %.100s",
				    tty_name, mode, strerror(errno));
			}
		}
	}
}