unix_grantpt.c 4.7 KB

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  1. /* Copyright (C) 1998 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.
  4. The GNU C Library is free software; you can redistribute it and/or
  5. modify it under the terms of the GNU Library General Public License as
  6. published by the Free Software Foundation; either version 2 of the
  7. License, or (at your option) any later version.
  8. The GNU C Library is distributed in the hope that it will be useful,
  9. but WITHOUT ANY WARRANTY; without even the implied warranty of
  10. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11. Library General Public License for more details.
  12. You should have received a copy of the GNU Library General Public
  13. License along with the GNU C Library; see the file COPYING.LIB. If not,
  14. write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  15. Boston, MA 02111-1307, USA. */
  16. #include <assert.h>
  17. #include <errno.h>
  18. #include <grp.h>
  19. #include <limits.h>
  20. #include <stdlib.h>
  21. #include <string.h>
  22. #include <sys/resource.h>
  23. #include <sys/stat.h>
  24. #include <sys/types.h>
  25. #include <sys/wait.h>
  26. #include <unistd.h>
  27. #include "pty-private.h"
  28. /* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
  29. #include <sys/syscall.h>
  30. #if ! defined __NR_vfork && defined __UCLIBC_HAS_MMU__
  31. #define vfork fork
  32. #endif
  33. extern int ptsname_r (int fd, char *buf, size_t buflen);
  34. /* Return the result of ptsname_r in the buffer pointed to by PTS,
  35. which should be of length BUF_LEN. If it is too long to fit in
  36. this buffer, a sufficiently long buffer is allocated using malloc,
  37. and returned in PTS. 0 is returned upon success, -1 otherwise. */
  38. static int
  39. pts_name (int fd, char **pts, size_t buf_len)
  40. {
  41. int rv;
  42. char *buf = *pts;
  43. for (;;)
  44. {
  45. char *new_buf;
  46. if (buf_len)
  47. {
  48. rv = ptsname_r (fd, buf, buf_len);
  49. if (rv != 0 || memchr (buf, '\0', buf_len))
  50. /* We either got an error, or we succeeded and the
  51. returned name fit in the buffer. */
  52. break;
  53. /* Try again with a longer buffer. */
  54. buf_len += buf_len; /* Double it */
  55. }
  56. else
  57. /* No initial buffer; start out by mallocing one. */
  58. buf_len = 128; /* First time guess. */
  59. if (buf != *pts)
  60. /* We've already malloced another buffer at least once. */
  61. new_buf = realloc (buf, buf_len);
  62. else
  63. new_buf = malloc (buf_len);
  64. if (! new_buf)
  65. {
  66. rv = -1;
  67. errno = ENOMEM;
  68. break;
  69. }
  70. buf = new_buf;
  71. }
  72. if (rv == 0)
  73. *pts = buf; /* Return buffer to the user. */
  74. else if (buf != *pts)
  75. free (buf); /* Free what we malloced when returning an error. */
  76. return rv;
  77. }
  78. /* Change the ownership and access permission of the slave pseudo
  79. terminal associated with the master pseudo terminal specified
  80. by FD. */
  81. int
  82. grantpt (int fd)
  83. {
  84. int retval = -1;
  85. #ifdef PATH_MAX
  86. char _buf[PATH_MAX];
  87. #else
  88. char _buf[512];
  89. #endif
  90. char *buf = _buf;
  91. struct stat st;
  92. uid_t uid;
  93. gid_t gid;
  94. pid_t pid;
  95. if (pts_name (fd, &buf, sizeof (_buf)))
  96. return -1;
  97. if (__xstat (_STAT_VER, buf, &st) < 0)
  98. goto cleanup;
  99. /* Make sure that we own the device. */
  100. uid = getuid ();
  101. if (st.st_uid != uid)
  102. {
  103. if (chown (buf, uid, st.st_gid) < 0)
  104. goto helper;
  105. }
  106. gid = getgid ();
  107. /* Make sure the group of the device is that special group. */
  108. if (st.st_gid != gid)
  109. {
  110. if (chown (buf, uid, gid) < 0)
  111. goto helper;
  112. }
  113. /* Make sure the permission mode is set to readable and writable by
  114. the owner, and writable by the group. */
  115. if ((st.st_mode & ACCESSPERMS) != (S_IRUSR|S_IWUSR|S_IWGRP))
  116. {
  117. if (chmod (buf, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
  118. goto helper;
  119. }
  120. retval = 0;
  121. goto cleanup;
  122. /* We have to use the helper program. */
  123. helper:
  124. pid = vfork ();
  125. if (pid == -1)
  126. goto cleanup;
  127. else if (pid == 0)
  128. {
  129. /* Disable core dumps. */
  130. struct rlimit rl = { 0, 0 };
  131. setrlimit (RLIMIT_CORE, &rl);
  132. /* We pase the master pseudo terminal as file descriptor PTY_FILENO. */
  133. if (fd != PTY_FILENO)
  134. if (dup2 (fd, PTY_FILENO) < 0)
  135. _exit (FAIL_EBADF);
  136. execle (_PATH_PT_CHOWN, _PATH_PT_CHOWN, NULL, NULL);
  137. _exit (FAIL_EXEC);
  138. }
  139. else
  140. {
  141. int w;
  142. if (waitpid (pid, &w, 0) == -1)
  143. goto cleanup;
  144. if (!WIFEXITED (w))
  145. errno = ENOEXEC;
  146. else
  147. switch (WEXITSTATUS(w))
  148. {
  149. case 0:
  150. retval = 0;
  151. break;
  152. case FAIL_EBADF:
  153. errno = EBADF;
  154. break;
  155. case FAIL_EINVAL:
  156. errno = EINVAL;
  157. break;
  158. case FAIL_EACCES:
  159. errno = EACCES;
  160. break;
  161. case FAIL_EXEC:
  162. errno = ENOEXEC;
  163. break;
  164. default:
  165. assert(! "getpt: internal error: invalid exit code from pt_chown");
  166. }
  167. }
  168. cleanup:
  169. if (buf != _buf)
  170. free (buf);
  171. return retval;
  172. }