stdlib/FreeBSD/grantpt.c

   1 /*
   2  * Copyright (c) 2002 The FreeBSD Project, Inc.
   3  * All rights reserved.
   4  *
   5  * This software includes code contributed to the FreeBSD Project
   6  * by Ryan Younce of North Carolina State University.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the name of the FreeBSD Project nor the names of its
  17  *    contributors may be used to endorse or promote products derived from
  18  *    this software without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE FREEBSD PROJECT AND CONTRIBUTORS ``AS IS''
  21  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE FREEBSD PROJECT OR ITS CONTRIBUTORS
  24  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  30  * POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #include <sys/cdefs.h>
  34 #ifndef lint
  35 __FBSDID("$FreeBSD: src/lib/libc/stdlib/grantpt.c,v 1.2 2003/01/04 08:10:55 tjr Exp $");
  36 #endif /* not lint */
  37
  38 #include "namespace.h"
  39 #include <sys/types.h>
  40 #include <sys/stat.h>
  41 #include <sys/wait.h>
  42 #include <sys/time.h>
  43 #include <sys/resource.h>
  44
  45 #include <errno.h>
  46 #include <fcntl.h>
  47 #include <grp.h>
  48 #include <paths.h>
  49 #include <signal.h>
  50 #include <stdio.h>
  51 #include <stdlib.h>
  52 #include <string.h>
  53 #include <sysexits.h>
  54 #include <unistd.h>
  55 #include "un-namespace.h"
  56
  57 #define PTM_MAJOR       6       /* pseudo tty master major */
  58 #define PTS_MAJOR       5       /* pseudo tty slave major */
  59 #define PTM_PREFIX      "pty"   /* pseudo tty master naming convention */
  60 #define PTS_PREFIX      "tty"   /* pseudo tty slave naming convention */
  61
  62 /*
  63  * The following are range values for pseudo TTY devices.  Pseudo TTYs have a
  64  * name of /dev/[pt]ty[p-sP-S][0-9a-v], yielding 256 combinations per major.
  65  */
  66 #define PT_MAX          256
  67 #define PT_DEV1         "pqrsPQRS"
  68 #define PT_DEV2         "0123456789abcdefghijklmnopqrstuv"
  69
  70 /*
  71  * grantpt(3) support utility.
  72  */
  73 #define _PATH_PTCHOWN   "/usr/libexec/pt_chown"
  74
  75 /*
  76  * ISPTM(x) returns 0 for struct stat x if x is not a pty master.
  77  * The bounds checking may be unnecessary but it does eliminate doubt.
  78  */
  79 #define ISPTM(x)        (S_ISCHR((x).st_mode) &&                        \
  80                          major((x).st_rdev) == PTM_MAJOR &&             \
  81                          minor((x).st_rdev) >= 0 &&                     \
  82                          minor((x).st_rdev) < PT_MAX)
  83
  84 /*
  85  * grantpt():  grant ownership of a slave pseudo-terminal device to the
  86  *             current user.
  87  */
  88
  89 int
  90 grantpt(int fildes)
  91 {
  92         int retval, serrno, status;
  93         pid_t pid, spid;
  94         gid_t gid;
  95         char *slave;
  96         sigset_t oblock, nblock;
  97         struct group *grp;
  98
  99         retval = -1;
 100         serrno = errno;
 101
 102         if ((slave = ptsname(fildes)) != NULL) {
 103                 /*
 104                  * Block SIGCHLD.
 105                  */
 106                 (void)sigemptyset(&nblock);
 107                 (void)sigaddset(&nblock, SIGCHLD);
 108                 (void)_sigprocmask(SIG_BLOCK, &nblock, &oblock);
 109
 110                 switch (pid = fork()) {
 111                 case -1:
 112                         break;
 113                 case 0:         /* child */
 114                         /*
 115                          * pt_chown expects the master pseudo TTY to be its
 116                          * standard input.
 117                          */
 118                         (void)_dup2(fildes, STDIN_FILENO);
 119                         (void)_sigprocmask(SIG_SETMASK, &oblock, NULL);
 120                         execl(_PATH_PTCHOWN, _PATH_PTCHOWN, (char *)NULL);
 121                         _exit(EX_UNAVAILABLE);
 122                         /* NOTREACHED */
 123                 default:        /* parent */
 124                         /*
 125                          * Just wait for the process.  Error checking is
 126                          * done below.
 127                          */
 128                         while ((spid = _waitpid(pid, &status, 0)) == -1 &&
 129                                (errno == EINTR))
 130                                 ;
 131                         if (spid != -1 && WIFEXITED(status) &&
 132                             WEXITSTATUS(status) == EX_OK)
 133                                 retval = 0;
 134                         else
 135                                 errno = EACCES;
 136                         break;
 137                 }
 138
 139                 /*
 140                  * Restore process's signal mask.
 141                  */
 142                 (void)_sigprocmask(SIG_SETMASK, &oblock, NULL);
 143
 144                 if (retval) {
 145                         /*
 146                          * pt_chown failed.  Try to manually change the
 147                          * permissions for the slave.
 148                          */
 149                         gid = (grp = getgrnam("tty")) ? grp->gr_gid : -1;
 150                         if (chown(slave, getuid(), gid) == -1 ||
 151                             chmod(slave, S_IRUSR | S_IWUSR | S_IWGRP) == -1)
 152                                 errno = EACCES;
 153                         else
 154                                 retval = 0;
 155                 }
 156         }
 157
 158         if (!retval)
 159                 errno = serrno;
 160
 161         return (retval);
 162 }
 163
 164 /*
 165  * posix_openpt():  open the first available master pseudo-terminal device
 166  *                  and return descriptor.
 167  */
 168 int
 169 posix_openpt(int oflag)
 170 {
 171         char *mc1, *mc2, master[] = _PATH_DEV PTM_PREFIX "XY";
 172         const char *pc1, *pc2;
 173         int fildes, bflag, serrno;
 174
 175         fildes = -1;
 176         bflag = 0;
 177         serrno = errno;
 178
 179         /*
 180          * Check flag validity.  POSIX doesn't require it,
 181          * but we still do so.
 182          */
 183         if (oflag & ~(O_RDWR | O_NOCTTY))
 184                 errno = EINVAL;
 185         else {
 186                 mc1 = master + strlen(_PATH_DEV PTM_PREFIX);
 187                 mc2 = mc1 + 1;
 188
 189                 /* Cycle through all possible master PTY devices. */
 190                 for (pc1 = PT_DEV1; !bflag && (*mc1 = *pc1); ++pc1)
 191                         for (pc2 = PT_DEV2; (*mc2 = *pc2) != '\0'; ++pc2) {
 192                                 /*
 193                                  * Break out if we successfully open a PTY,
 194                                  * or if open() fails due to limits.
 195                                  */
 196                                 if ((fildes = _open(master, oflag)) != -1 ||
 197                                     (errno == EMFILE || errno == ENFILE)) {
 198                                         ++bflag;
 199                                         break;
 200                                 }
 201                         }
 202
 203                 if (fildes != -1)
 204                         errno = serrno;
 205                 else if (!bflag)
 206                         errno = EAGAIN;
 207         }
 208
 209         return (fildes);
 210 }
 211
 212 /*
 213  * ptsname():  return the pathname of the slave pseudo-terminal device
 214  *             associated with the specified master.
 215  */
 216 char *
 217 ptsname(int fildes)
 218 {
 219         static char slave[] = _PATH_DEV PTS_PREFIX "XY";
 220         char *retval;
 221         struct stat sbuf;
 222
 223         retval = NULL;
 224
 225         if (_fstat(fildes, &sbuf) == 0) {
 226                 if (!ISPTM(sbuf))
 227                         errno = EINVAL;
 228                 else {
 229                         (void)sprintf(slave, _PATH_DEV PTS_PREFIX "%c%c",
 230                                       PT_DEV1[minor(sbuf.st_rdev) / 32],
 231                                       PT_DEV2[minor(sbuf.st_rdev) % 32]);
 232                         retval = slave;
 233                 }
 234         }
 235
 236         return (retval);
 237 }
 238
 239 /*
 240  * unlockpt():  unlock a pseudo-terminal device pair.
 241  */
 242 int
 243 unlockpt(int fildes)
 244 {
 245         int retval;
 246         struct stat sbuf;
 247
 248         /*
 249          * Unlocking a master/slave pseudo-terminal pair has no meaning in a
 250          * non-streams PTY environment.  However, we do ensure fildes is a
 251          * valid master pseudo-terminal device.
 252          */
 253         if ((retval = _fstat(fildes, &sbuf)) == 0 && !ISPTM(sbuf)) {
 254                 errno = EINVAL;
 255                 retval = -1;
 256         }
 257
 258         return (retval);
 259 }