unix_grantpt.c 5.0 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. libc_hidden_proto(memchr)
  29. libc_hidden_proto(getgid)
  30. libc_hidden_proto(getuid)
  31. libc_hidden_proto(setrlimit)
  32. libc_hidden_proto(waitpid)
  33. libc_hidden_proto(dup2)
  34. libc_hidden_proto(chmod)
  35. libc_hidden_proto(chown)
  36. libc_hidden_proto(vfork)
  37. libc_hidden_proto(fork)
  38. libc_hidden_proto(stat)
  39. libc_hidden_proto(ptsname_r)
  40. libc_hidden_proto(execle)
  41. libc_hidden_proto(_exit)
  42. /* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
  43. #include <sys/syscall.h>
  44. #if ! defined __NR_vfork
  45. #define vfork fork
  46. #endif
  47. /* Return the result of ptsname_r in the buffer pointed to by PTS,
  48. which should be of length BUF_LEN. If it is too long to fit in
  49. this buffer, a sufficiently long buffer is allocated using malloc,
  50. and returned in PTS. 0 is returned upon success, -1 otherwise. */
  51. static int
  52. pts_name (int fd, char **pts, size_t buf_len)
  53. {
  54. int rv;
  55. char *buf = *pts;
  56. for (;;)
  57. {
  58. char *new_buf;
  59. if (buf_len)
  60. {
  61. rv = ptsname_r (fd, buf, buf_len);
  62. if (rv != 0 || memchr (buf, '\0', buf_len))
  63. /* We either got an error, or we succeeded and the
  64. returned name fit in the buffer. */
  65. break;
  66. /* Try again with a longer buffer. */
  67. buf_len += buf_len; /* Double it */
  68. }
  69. else
  70. /* No initial buffer; start out by mallocing one. */
  71. buf_len = 128; /* First time guess. */
  72. if (buf != *pts)
  73. /* We've already malloced another buffer at least once. */
  74. new_buf = realloc (buf, buf_len);
  75. else
  76. new_buf = malloc (buf_len);
  77. if (! new_buf)
  78. {
  79. rv = -1;
  80. errno = ENOMEM;
  81. break;
  82. }
  83. buf = new_buf;
  84. }
  85. if (rv == 0)
  86. *pts = buf; /* Return buffer to the user. */
  87. else if (buf != *pts)
  88. free (buf); /* Free what we malloced when returning an error. */
  89. return rv;
  90. }
  91. /* Change the ownership and access permission of the slave pseudo
  92. terminal associated with the master pseudo terminal specified
  93. by FD. */
  94. int
  95. grantpt (int fd)
  96. {
  97. int retval = -1;
  98. #ifdef PATH_MAX
  99. char _buf[PATH_MAX];
  100. #else
  101. char _buf[512];
  102. #endif
  103. char *buf = _buf;
  104. struct stat st;
  105. uid_t uid;
  106. gid_t gid;
  107. pid_t pid;
  108. if (pts_name (fd, &buf, sizeof (_buf)))
  109. return -1;
  110. if (stat(buf, &st) < 0)
  111. goto cleanup;
  112. /* Make sure that we own the device. */
  113. uid = getuid ();
  114. if (st.st_uid != uid)
  115. {
  116. if (chown (buf, uid, st.st_gid) < 0)
  117. goto helper;
  118. }
  119. gid = getgid ();
  120. /* Make sure the group of the device is that special group. */
  121. if (st.st_gid != gid)
  122. {
  123. if (chown (buf, uid, gid) < 0)
  124. goto helper;
  125. }
  126. /* Make sure the permission mode is set to readable and writable by
  127. the owner, and writable by the group. */
  128. if ((st.st_mode & ACCESSPERMS) != (S_IRUSR|S_IWUSR|S_IWGRP))
  129. {
  130. if (chmod (buf, S_IRUSR|S_IWUSR|S_IWGRP) < 0)
  131. goto helper;
  132. }
  133. retval = 0;
  134. goto cleanup;
  135. /* We have to use the helper program. */
  136. helper:
  137. pid = vfork ();
  138. if (pid == -1)
  139. goto cleanup;
  140. else if (pid == 0)
  141. {
  142. /* Disable core dumps. */
  143. struct rlimit rl = { 0, 0 };
  144. setrlimit (RLIMIT_CORE, &rl);
  145. /* We pase the master pseudo terminal as file descriptor PTY_FILENO. */
  146. if (fd != PTY_FILENO)
  147. if (dup2 (fd, PTY_FILENO) < 0)
  148. _exit (FAIL_EBADF);
  149. execle (_PATH_PT_CHOWN, _PATH_PT_CHOWN, NULL, NULL);
  150. _exit (FAIL_EXEC);
  151. }
  152. else
  153. {
  154. int w;
  155. if (waitpid (pid, &w, 0) == -1)
  156. goto cleanup;
  157. if (!WIFEXITED (w))
  158. errno = ENOEXEC;
  159. else
  160. switch (WEXITSTATUS(w))
  161. {
  162. case 0:
  163. retval = 0;
  164. break;
  165. case FAIL_EBADF:
  166. errno = EBADF;
  167. break;
  168. case FAIL_EINVAL:
  169. errno = EINVAL;
  170. break;
  171. case FAIL_EACCES:
  172. errno = EACCES;
  173. break;
  174. case FAIL_EXEC:
  175. errno = ENOEXEC;
  176. break;
  177. default:
  178. assert(! "getpt: internal error: invalid exit code from pt_chown");
  179. }
  180. }
  181. cleanup:
  182. if (buf != _buf)
  183. free (buf);
  184. return retval;
  185. }