crypto/openssh-4/sshpty.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   4  *                    All rights reserved
   5  * Allocating a pseudo-terminal, and making it the controlling tty.
   6  *
   7  * As far as I am concerned, the code I have written for this software
   8  * can be used freely for any purpose.  Any derived versions of this
   9  * software must be clearly marked as such, and if the derived work is
  10  * incompatible with the protocol description in the RFC file, it must be
  11  * called by a name other than "ssh" or "Secure Shell".
  12  */
  13
  14 #include "includes.h"
  15 RCSID("$OpenBSD: sshpty.c,v 1.12 2004/06/21 17:36:31 avsm Exp $");
  16
  17 #ifdef HAVE_UTIL_H
  18 # include <util.h>
  19 #endif /* HAVE_UTIL_H */
  20
  21 #include "sshpty.h"
  22 #include "log.h"
  23 #include "misc.h"
  24
  25 #ifdef HAVE_PTY_H
  26 # include <pty.h>
  27 #endif
  28
  29 #ifndef O_NOCTTY
  30 #define O_NOCTTY 0
  31 #endif
  32
  33 /*
  34  * Allocates and opens a pty.  Returns 0 if no pty could be allocated, or
  35  * nonzero if a pty was successfully allocated.  On success, open file
  36  * descriptors for the pty and tty sides and the name of the tty side are
  37  * returned (the buffer must be able to hold at least 64 characters).
  38  */
  39
  40 int
  41 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen)
  42 {
  43         /* openpty(3) exists in OSF/1 and some other os'es */
  44         char *name;
  45         int i;
  46
  47         i = openpty(ptyfd, ttyfd, NULL, NULL, NULL);
  48         if (i < 0) {
  49                 error("openpty: %.100s", strerror(errno));
  50                 return 0;
  51         }
  52         name = ttyname(*ttyfd);
  53         if (!name)
  54                 fatal("openpty returns device for which ttyname fails.");
  55
  56         strlcpy(namebuf, name, namebuflen);     /* possible truncation */
  57         return 1;
  58 }
  59
  60 /* Releases the tty.  Its ownership is returned to root, and permissions to 0666. */
  61
  62 void
  63 pty_release(const char *tty)
  64 {
  65         if (chown(tty, (uid_t) 0, (gid_t) 0) < 0)
  66                 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno));
  67         if (chmod(tty, (mode_t) 0666) < 0)
  68                 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno));
  69 }
  70
  71 /* Makes the tty the process's controlling tty and sets it to sane modes. */
  72
  73 void
  74 pty_make_controlling_tty(int *ttyfd, const char *tty)
  75 {
  76         int fd;
  77 #ifdef USE_VHANGUP
  78         void *old;
  79 #endif /* USE_VHANGUP */
  80
  81 #ifdef _UNICOS
  82         if (setsid() < 0)
  83                 error("setsid: %.100s", strerror(errno));
  84
  85         fd = open(tty, O_RDWR|O_NOCTTY);
  86         if (fd != -1) {
  87                 signal(SIGHUP, SIG_IGN);
  88                 ioctl(fd, TCVHUP, (char *)NULL);
  89                 signal(SIGHUP, SIG_DFL);
  90                 setpgid(0, 0);
  91                 close(fd);
  92         } else {
  93                 error("Failed to disconnect from controlling tty.");
  94         }
  95
  96         debug("Setting controlling tty using TCSETCTTY.");
  97         ioctl(*ttyfd, TCSETCTTY, NULL);
  98         fd = open("/dev/tty", O_RDWR);
  99         if (fd < 0)
 100                 error("%.100s: %.100s", tty, strerror(errno));
 101         close(*ttyfd);
 102         *ttyfd = fd;
 103 #else /* _UNICOS */
 104
 105         /* First disconnect from the old controlling tty. */
 106 #ifdef TIOCNOTTY
 107         fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
 108         if (fd >= 0) {
 109                 (void) ioctl(fd, TIOCNOTTY, NULL);
 110                 close(fd);
 111         }
 112 #endif /* TIOCNOTTY */
 113         if (setsid() < 0)
 114                 error("setsid: %.100s", strerror(errno));
 115
 116         /*
 117          * Verify that we are successfully disconnected from the controlling
 118          * tty.
 119          */
 120         fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
 121         if (fd >= 0) {
 122                 error("Failed to disconnect from controlling tty.");
 123                 close(fd);
 124         }
 125         /* Make it our controlling tty. */
 126 #ifdef TIOCSCTTY
 127         debug("Setting controlling tty using TIOCSCTTY.");
 128         if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
 129                 error("ioctl(TIOCSCTTY): %.100s", strerror(errno));
 130 #endif /* TIOCSCTTY */
 131 #ifdef NEED_SETPGRP
 132         if (setpgrp(0,0) < 0)
 133                 error("SETPGRP %s",strerror(errno));
 134 #endif /* NEED_SETPGRP */
 135 #ifdef USE_VHANGUP
 136         old = signal(SIGHUP, SIG_IGN);
 137         vhangup();
 138         signal(SIGHUP, old);
 139 #endif /* USE_VHANGUP */
 140         fd = open(tty, O_RDWR);
 141         if (fd < 0) {
 142                 error("%.100s: %.100s", tty, strerror(errno));
 143         } else {
 144 #ifdef USE_VHANGUP
 145                 close(*ttyfd);
 146                 *ttyfd = fd;
 147 #else /* USE_VHANGUP */
 148                 close(fd);
 149 #endif /* USE_VHANGUP */
 150         }
 151         /* Verify that we now have a controlling tty. */
 152         fd = open(_PATH_TTY, O_WRONLY);
 153         if (fd < 0)
 154                 error("open /dev/tty failed - could not set controlling tty: %.100s",
 155                     strerror(errno));
 156         else
 157                 close(fd);
 158 #endif /* _UNICOS */
 159 }
 160
 161 /* Changes the window size associated with the pty. */
 162
 163 void
 164 pty_change_window_size(int ptyfd, int row, int col,
 165         int xpixel, int ypixel)
 166 {
 167         struct winsize w;
 168
 169         w.ws_row = row;
 170         w.ws_col = col;
 171         w.ws_xpixel = xpixel;
 172         w.ws_ypixel = ypixel;
 173         (void) ioctl(ptyfd, TIOCSWINSZ, &w);
 174 }
 175
 176 void
 177 pty_setowner(struct passwd *pw, const char *tty)
 178 {
 179         struct group *grp;
 180         gid_t gid;
 181         mode_t mode;
 182         struct stat st;
 183
 184         /* Determine the group to make the owner of the tty. */
 185         grp = getgrnam("tty");
 186         if (grp) {
 187                 gid = grp->gr_gid;
 188                 mode = S_IRUSR | S_IWUSR | S_IWGRP;
 189         } else {
 190                 gid = pw->pw_gid;
 191                 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH;
 192         }
 193
 194         /*
 195          * Change owner and mode of the tty as required.
 196          * Warn but continue if filesystem is read-only and the uids match/
 197          * tty is owned by root.
 198          */
 199         if (stat(tty, &st))
 200                 fatal("stat(%.100s) failed: %.100s", tty,
 201                     strerror(errno));
 202
 203         if (st.st_uid != pw->pw_uid || st.st_gid != gid) {
 204                 if (chown(tty, pw->pw_uid, gid) < 0) {
 205                         if (errno == EROFS &&
 206                             (st.st_uid == pw->pw_uid || st.st_uid == 0))
 207                                 debug("chown(%.100s, %u, %u) failed: %.100s",
 208                                     tty, (u_int)pw->pw_uid, (u_int)gid,
 209                                     strerror(errno));
 210                         else
 211                                 fatal("chown(%.100s, %u, %u) failed: %.100s",
 212                                     tty, (u_int)pw->pw_uid, (u_int)gid,
 213                                     strerror(errno));
 214                 }
 215         }
 216
 217         if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) {
 218                 if (chmod(tty, mode) < 0) {
 219                         if (errno == EROFS &&
 220                             (st.st_mode & (S_IRGRP | S_IROTH)) == 0)
 221                                 debug("chmod(%.100s, 0%o) failed: %.100s",
 222                                     tty, (u_int)mode, strerror(errno));
 223                         else
 224                                 fatal("chmod(%.100s, 0%o) failed: %.100s",
 225                                     tty, (u_int)mode, strerror(errno));
 226                 }
 227         }
 228 }