sshpty.c revision 181110
1/* $OpenBSD: sshpty.c,v 1.26 2006/08/03 03:34:42 deraadt 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/* 50 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 51 * nonzero if a pty was successfully allocated. On success, open file 52 * descriptors for the pty and tty sides and the name of the tty side are 53 * returned (the buffer must be able to hold at least 64 characters). 54 */ 55 56int 57pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen) 58{ 59 /* openpty(3) exists in OSF/1 and some other os'es */ 60 char *name; 61 int i; 62 63 i = openpty(ptyfd, ttyfd, NULL, NULL, NULL); 64 if (i < 0) { 65 error("openpty: %.100s", strerror(errno)); 66 return 0; 67 } 68 name = ttyname(*ttyfd); 69 if (!name) 70 fatal("openpty returns device for which ttyname fails."); 71 72 strlcpy(namebuf, name, namebuflen); /* possible truncation */ 73 return 1; 74} 75 76/* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 77 78void 79pty_release(const char *tty) 80{ 81 if (chown(tty, (uid_t) 0, (gid_t) 0) < 0) 82 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 83 if (chmod(tty, (mode_t) 0666) < 0) 84 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 85} 86 87/* Makes the tty the process's controlling tty and sets it to sane modes. */ 88 89void 90pty_make_controlling_tty(int *ttyfd, const char *tty) 91{ 92 int fd; 93#ifdef USE_VHANGUP 94 void *old; 95#endif /* USE_VHANGUP */ 96 97#ifdef _UNICOS 98 if (setsid() < 0) 99 error("setsid: %.100s", strerror(errno)); 100 101 fd = open(tty, O_RDWR|O_NOCTTY); 102 if (fd != -1) { 103 signal(SIGHUP, SIG_IGN); 104 ioctl(fd, TCVHUP, (char *)NULL); 105 signal(SIGHUP, SIG_DFL); 106 setpgid(0, 0); 107 close(fd); 108 } else { 109 error("Failed to disconnect from controlling tty."); 110 } 111 112 debug("Setting controlling tty using TCSETCTTY."); 113 ioctl(*ttyfd, TCSETCTTY, NULL); 114 fd = open("/dev/tty", O_RDWR); 115 if (fd < 0) 116 error("%.100s: %.100s", tty, strerror(errno)); 117 close(*ttyfd); 118 *ttyfd = fd; 119#else /* _UNICOS */ 120 121 /* First disconnect from the old controlling tty. */ 122#ifdef TIOCNOTTY 123 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 124 if (fd >= 0) { 125 (void) ioctl(fd, TIOCNOTTY, NULL); 126 close(fd); 127 } 128#endif /* TIOCNOTTY */ 129 if (setsid() < 0) 130 error("setsid: %.100s", strerror(errno)); 131 132 /* 133 * Verify that we are successfully disconnected from the controlling 134 * tty. 135 */ 136 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 137 if (fd >= 0) { 138 error("Failed to disconnect from controlling tty."); 139 close(fd); 140 } 141 /* Make it our controlling tty. */ 142#ifdef TIOCSCTTY 143 debug("Setting controlling tty using TIOCSCTTY."); 144 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 145 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 146#endif /* TIOCSCTTY */ 147#ifdef NEED_SETPGRP 148 if (setpgrp(0,0) < 0) 149 error("SETPGRP %s",strerror(errno)); 150#endif /* NEED_SETPGRP */ 151#ifdef USE_VHANGUP 152 old = signal(SIGHUP, SIG_IGN); 153 vhangup(); 154 signal(SIGHUP, old); 155#endif /* USE_VHANGUP */ 156 fd = open(tty, O_RDWR); 157 if (fd < 0) { 158 error("%.100s: %.100s", tty, strerror(errno)); 159 } else { 160#ifdef USE_VHANGUP 161 close(*ttyfd); 162 *ttyfd = fd; 163#else /* USE_VHANGUP */ 164 close(fd); 165#endif /* USE_VHANGUP */ 166 } 167 /* Verify that we now have a controlling tty. */ 168 fd = open(_PATH_TTY, O_WRONLY); 169 if (fd < 0) 170 error("open /dev/tty failed - could not set controlling tty: %.100s", 171 strerror(errno)); 172 else 173 close(fd); 174#endif /* _UNICOS */ 175} 176 177/* Changes the window size associated with the pty. */ 178 179void 180pty_change_window_size(int ptyfd, u_int row, u_int col, 181 u_int xpixel, u_int ypixel) 182{ 183 struct winsize w; 184 185 /* may truncate u_int -> u_short */ 186 w.ws_row = row; 187 w.ws_col = col; 188 w.ws_xpixel = xpixel; 189 w.ws_ypixel = ypixel; 190 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 191} 192 193void 194pty_setowner(struct passwd *pw, const char *tty) 195{ 196 struct group *grp; 197 gid_t gid; 198 mode_t mode; 199 struct stat st; 200 201 /* Determine the group to make the owner of the tty. */ 202 grp = getgrnam("tty"); 203 if (grp) { 204 gid = grp->gr_gid; 205 mode = S_IRUSR | S_IWUSR | S_IWGRP; 206 } else { 207 gid = pw->pw_gid; 208 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH; 209 } 210 211 /* 212 * Change owner and mode of the tty as required. 213 * Warn but continue if filesystem is read-only and the uids match/ 214 * tty is owned by root. 215 */ 216 if (stat(tty, &st)) 217 fatal("stat(%.100s) failed: %.100s", tty, 218 strerror(errno)); 219 220#ifdef WITH_SELINUX 221 ssh_selinux_setup_pty(pw->pw_name, tty); 222#endif 223 224 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 225 if (chown(tty, pw->pw_uid, gid) < 0) { 226 if (errno == EROFS && 227 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 228 debug("chown(%.100s, %u, %u) failed: %.100s", 229 tty, (u_int)pw->pw_uid, (u_int)gid, 230 strerror(errno)); 231 else 232 fatal("chown(%.100s, %u, %u) failed: %.100s", 233 tty, (u_int)pw->pw_uid, (u_int)gid, 234 strerror(errno)); 235 } 236 } 237 238 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 239 if (chmod(tty, mode) < 0) { 240 if (errno == EROFS && 241 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 242 debug("chmod(%.100s, 0%o) failed: %.100s", 243 tty, (u_int)mode, strerror(errno)); 244 else 245 fatal("chmod(%.100s, 0%o) failed: %.100s", 246 tty, (u_int)mode, strerror(errno)); 247 } 248 } 249} 250