crypto/openssh/sshpty.c

   1 /* $OpenBSD: sshpty.c,v 1.30 2015/07/30 23:09:15 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Allocating a pseudo-terminal, and making it the controlling tty.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  */
  14
  15 #include "includes.h"
  16
  17 #include <sys/types.h>
  18 #include <sys/ioctl.h>
  19 #include <sys/stat.h>
  20 #include <signal.h>
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <grp.h>
  25 #ifdef HAVE_PATHS_H
  26 # include <paths.h>
  27 #endif
  28 #include <pwd.h>
  29 #include <stdarg.h>
  30 #include <string.h>
  31 #include <termios.h>
  32 #ifdef HAVE_UTIL_H
  33 # include <util.h>
  34 #endif
  35 #include <unistd.h>
  36
  37 #include "sshpty.h"
  38 #include "log.h"
  39 #include "misc.h"
  40
  41 #ifdef HAVE_PTY_H
  42 # include <pty.h>
  43 #endif
  44
  45 #ifndef O_NOCTTY
  46 #define O_NOCTTY 0
  47 #endif
  48
  49 #ifdef __APPLE__
  50 # include <AvailabilityMacros.h>
  51 # if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5)
  52 #  define __APPLE_PRIVPTY__
  53 # endif
  54 #endif
  55
  56 /*
  57  * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
  58  * nonzero if a pty was successfully allocated.  On success, open file
  59  * descriptors for the pty and tty sides and the name of the tty side are
  60  * returned (the buffer must be able to hold at least 64 characters).
  61  */
  62
  63 int
  64 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen)
  65 {
  66         /* openpty(3) exists in OSF/1 and some other os'es */
  67         char *name;
  68         int i;
  69
  70         i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
  71         if (i < 0) {
  72                 error("openpty: %.100s", strerror(errno));
  73                 return 0;
  74         }
  75         name = ttyname(*ttyfd);
  76         if (!name)
  77                 fatal("openpty returns device for which ttyname fails.");
  78
  79         strlcpy(namebuf, name, namebuflen);     /* possible truncation */
  80         return 1;
  81 }
  82
  83 /* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */
  84
  85 void
  86 pty_release(const char *tty)
  87 {
  88 #if !defined(__APPLE_PRIVPTY__) && !defined(HAVE_OPENPTY)
  89         if (chown(tty, (uid_t) 0, (gid_t) 0) < 0)
  90                 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno));
  91         if (chmod(tty, (mode_t) 0666) < 0)
  92                 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno));
  93 #endif /* !__APPLE_PRIVPTY__ && !HAVE_OPENPTY */
  94 }
  95
  96 /* Makes the tty the process's controlling tty and sets it to sane modes. */
  97
  98 void
  99 pty_make_controlling_tty(int *ttyfd, const char *tty)
 100 {
 101         int fd;
 102
 103 #ifdef _UNICOS
 104         if (setsid() < 0)
 105                 error("setsid: %.100s", strerror(errno));
 106
 107         fd = open(tty, O_RDWR|O_NOCTTY);
 108         if (fd != -1) {
 109                 signal(SIGHUP, SIG_IGN);
 110                 ioctl(fd, TCVHUP, (char *)NULL);
 111                 signal(SIGHUP, SIG_DFL);
 112                 setpgid(0, 0);
 113                 close(fd);
 114         } else {
 115                 error("Failed to disconnect from controlling tty.");
 116         }
 117
 118         debug("Setting controlling tty using TCSETCTTY.");
 119         ioctl(*ttyfd, TCSETCTTY, NULL);
 120         fd = open("/dev/tty", O_RDWR);
 121         if (fd < 0)
 122                 error("%.100s: %.100s", tty, strerror(errno));
 123         close(*ttyfd);
 124         *ttyfd = fd;
 125 #else /* _UNICOS */
 126
 127         /* First disconnect from the old controlling tty. */
 128 #ifdef TIOCNOTTY
 129         fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
 130         if (fd >= 0) {
 131                 (void) ioctl(fd, TIOCNOTTY, NULL);
 132                 close(fd);
 133         }
 134 #endif /* TIOCNOTTY */
 135         if (setsid() < 0)
 136                 error("setsid: %.100s", strerror(errno));
 137
 138         /*
 139          * Verify that we are successfully disconnected from the controlling
 140          * tty.
 141          */
 142         fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
 143         if (fd >= 0) {
 144                 error("Failed to disconnect from controlling tty.");
 145                 close(fd);
 146         }
 147         /* Make it our controlling tty. */
 148 #ifdef TIOCSCTTY
 149         debug("Setting controlling tty using TIOCSCTTY.");
 150         if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
 151                 error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
 152 #endif /* TIOCSCTTY */
 153 #ifdef NEED_SETPGRP
 154         if (setpgrp(0,0) < 0)
 155                 error("SETPGRP %s",strerror(errno));
 156 #endif /* NEED_SETPGRP */
 157         fd = open(tty, O_RDWR);
 158         if (fd < 0) {
 159                 error("%.100s: %.100s", tty, strerror(errno));
 160         } else {
 161                 close(fd);
 162         }
 163         /* Verify that we now have a controlling tty. */
 164         fd = open(_PATH_TTY, O_WRONLY);
 165         if (fd < 0)
 166                 error("open /dev/tty failed - could not set controlling tty: %.100s",
 167                     strerror(errno));
 168         else
 169                 close(fd);
 170 #endif /* _UNICOS */
 171 }
 172
 173 /* Changes the window size associated with the pty. */
 174
 175 void
 176 pty_change_window_size(int ptyfd, u_int row, u_int col,
 177         u_int xpixel, u_int ypixel)
 178 {
 179         struct winsize w;
 180
 181         /* may truncate u_int -> u_short */
 182         w.ws_row = row;
 183         w.ws_col = col;
 184         w.ws_xpixel = xpixel;
 185         w.ws_ypixel = ypixel;
 186         (void) ioctl(ptyfd, TIOCSWINSZ, &w);
 187 }
 188
 189 void
 190 pty_setowner(struct passwd *pw, const char *tty)
 191 {
 192         struct group *grp;
 193         gid_t gid;
 194         mode_t mode;
 195         struct stat st;
 196
 197         /* Determine the group to make the owner of the tty. */
 198         grp = getgrnam("tty");
 199         gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid;
 200         mode = (grp != NULL) ? 0620 : 0600;
 201
 202         /*
 203          * Change owner and mode of the tty as required.
 204          * Warn but continue if filesystem is read-only and the uids match/
 205          * tty is owned by root.
 206          */
 207         if (stat(tty, &st))
 208                 fatal("stat(%.100s) failed: %.100s", tty,
 209                     strerror(errno));
 210
 211 #ifdef WITH_SELINUX
 212         ssh_selinux_setup_pty(pw->pw_name, tty);
 213 #endif
 214
 215         if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
 216                 if (chown(tty, pw->pw_uid, gid) < 0) {
 217                         if (errno == EROFS &&
 218                             (st.st_uid == pw->pw_uid || st.st_uid == 0))
 219                                 debug("chown(%.100s, %u, %u) failed: %.100s",
 220                                     tty, (u_int)pw->pw_uid, (u_int)gid,
 221                                     strerror(errno));
 222                         else
 223                                 fatal("chown(%.100s, %u, %u) failed: %.100s",
 224                                     tty, (u_int)pw->pw_uid, (u_int)gid,
 225                                     strerror(errno));
 226                 }
 227         }
 228
 229         if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
 230                 if (chmod(tty, mode) < 0) {
 231                         if (errno == EROFS &&
 232                             (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
 233                                 debug("chmod(%.100s, 0%o) failed: %.100s",
 234                                     tty, (u_int)mode, strerror(errno));
 235                         else
 236                                 fatal("chmod(%.100s, 0%o) failed: %.100s",
 237                                     tty, (u_int)mode, strerror(errno));
 238                 }
 239         }
 240 }