sshpty.c

   1 /* $OpenBSD: sshpty.c,v 1.28 2007/09/11 23:49:09 stevesk 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 #ifndef __APPLE_PRIVPTY__
  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__ */
  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 #ifdef USE_VHANGUP
 103         void *old;
 104 #endif /* USE_VHANGUP */
 105
 106 #ifdef _UNICOS
 107         if (setsid() < 0)
 108                 error("setsid: %.100s", strerror(errno));
 109
 110         fd = open(tty, O_RDWR|O_NOCTTY);
 111         if (fd != -1) {
 112                 signal(SIGHUP, SIG_IGN);
 113                 ioctl(fd, TCVHUP, (char *)NULL);
 114                 signal(SIGHUP, SIG_DFL);
 115                 setpgid(0, 0);
 116                 close(fd);
 117         } else {
 118                 error("Failed to disconnect from controlling tty.");
 119         }
 120
 121         debug("Setting controlling tty using TCSETCTTY.");
 122         ioctl(*ttyfd, TCSETCTTY, NULL);
 123         fd = open("/dev/tty", O_RDWR);
 124         if (fd < 0)
 125                 error("%.100s: %.100s", tty, strerror(errno));
 126         close(*ttyfd);
 127         *ttyfd = fd;
 128 #else /* _UNICOS */
 129
 130         /* First disconnect from the old controlling tty. */
 131 #ifdef TIOCNOTTY
 132         fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
 133         if (fd >= 0) {
 134                 (void) ioctl(fd, TIOCNOTTY, NULL);
 135                 close(fd);
 136         }
 137 #endif /* TIOCNOTTY */
 138         if (setsid() < 0)
 139                 error("setsid: %.100s", strerror(errno));
 140
 141         /*
 142          * Verify that we are successfully disconnected from the controlling
 143          * tty.
 144          */
 145         fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
 146         if (fd >= 0) {
 147                 error("Failed to disconnect from controlling tty.");
 148                 close(fd);
 149         }
 150         /* Make it our controlling tty. */
 151 #ifdef TIOCSCTTY
 152         debug("Setting controlling tty using TIOCSCTTY.");
 153         if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
 154                 error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
 155 #endif /* TIOCSCTTY */
 156 #ifdef NEED_SETPGRP
 157         if (setpgrp(0,0) < 0)
 158                 error("SETPGRP %s",strerror(errno));
 159 #endif /* NEED_SETPGRP */
 160 #ifdef USE_VHANGUP
 161         old = signal(SIGHUP, SIG_IGN);
 162         vhangup();
 163         signal(SIGHUP, old);
 164 #endif /* USE_VHANGUP */
 165         fd = open(tty, O_RDWR);
 166         if (fd < 0) {
 167                 error("%.100s: %.100s", tty, strerror(errno));
 168         } else {
 169 #ifdef USE_VHANGUP
 170                 close(*ttyfd);
 171                 *ttyfd = fd;
 172 #else /* USE_VHANGUP */
 173                 close(fd);
 174 #endif /* USE_VHANGUP */
 175         }
 176         /* Verify that we now have a controlling tty. */
 177         fd = open(_PATH_TTY, O_WRONLY);
 178         if (fd < 0)
 179                 error("open /dev/tty failed - could not set controlling tty: %.100s",
 180                     strerror(errno));
 181         else
 182                 close(fd);
 183 #endif /* _UNICOS */
 184 }
 185
 186 /* Changes the window size associated with the pty. */
 187
 188 void
 189 pty_change_window_size(int ptyfd, u_int row, u_int col,
 190         u_int xpixel, u_int ypixel)
 191 {
 192         struct winsize w;
 193
 194         /* may truncate u_int -> u_short */
 195         w.ws_row = row;
 196         w.ws_col = col;
 197         w.ws_xpixel = xpixel;
 198         w.ws_ypixel = ypixel;
 199         (void) ioctl(ptyfd, TIOCSWINSZ, &w);
 200 }
 201
 202 void
 203 pty_setowner(struct passwd *pw, const char *tty)
 204 {
 205         struct group *grp;
 206         gid_t gid;
 207         mode_t mode;
 208         struct stat st;
 209
 210         /* Determine the group to make the owner of the tty. */
 211         grp = getgrnam("tty");
 212         if (grp) {
 213                 gid = grp->gr_gid;
 214                 mode = S_IRUSR | S_IWUSR | S_IWGRP;
 215         } else {
 216                 gid = pw->pw_gid;
 217                 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
 218         }
 219
 220         /*
 221          * Change owner and mode of the tty as required.
 222          * Warn but continue if filesystem is read-only and the uids match/
 223          * tty is owned by root.
 224          */
 225         if (stat(tty, &st))
 226                 fatal("stat(%.100s) failed: %.100s", tty,
 227                     strerror(errno));
 228
 229 #ifdef WITH_SELINUX
 230         ssh_selinux_setup_pty(pw->pw_name, tty);
 231 #endif
 232
 233         if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
 234                 if (chown(tty, pw->pw_uid, gid) < 0) {
 235                         if (errno == EROFS &&
 236                             (st.st_uid == pw->pw_uid || st.st_uid == 0))
 237                                 debug("chown(%.100s, %u, %u) failed: %.100s",
 238                                     tty, (u_int)pw->pw_uid, (u_int)gid,
 239                                     strerror(errno));
 240                         else
 241                                 fatal("chown(%.100s, %u, %u) failed: %.100s",
 242                                     tty, (u_int)pw->pw_uid, (u_int)gid,
 243                                     strerror(errno));
 244                 }
 245         }
 246
 247         if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
 248                 if (chmod(tty, mode) < 0) {
 249                         if (errno == EROFS &&
 250                             (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
 251                                 debug("chmod(%.100s, 0%o) failed: %.100s",
 252                                     tty, (u_int)mode, strerror(errno));
 253                         else
 254                                 fatal("chmod(%.100s, 0%o) failed: %.100s",
 255                                     tty, (u_int)mode, strerror(errno));
 256                 }
 257         }
 258 }