1 /* $OpenBSD: sshpty.c,v 1.28 2007/09/11 23:49:09 stevesk 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 #ifdef __APPLE__ 50 # include <AvailabilityMacros.h> 51 # if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5) 52 # define __APPLE_PRIVPTY__ 53 # endif 54 #endif 55 56 /* 57 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 58 * nonzero if a pty was successfully allocated. On success, open file 59 * descriptors for the pty and tty sides and the name of the tty side are 60 * returned (the buffer must be able to hold at least 64 characters). 61 */ 62 63 int 64 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen) 65 { 66 /* openpty(3) exists in OSF/1 and some other os'es */ 67 char *name; 68 int i; 69 70 i = openpty(ptyfd, ttyfd, NULL, NULL, NULL); 71 if (i < 0) { 72 error("openpty: %.100s", strerror(errno)); 73 return 0; 74 } 75 name = ttyname(*ttyfd); 76 if (!name) 77 fatal("openpty returns device for which ttyname fails."); 78 79 strlcpy(namebuf, name, namebuflen); /* possible truncation */ 80 return 1; 81 } 82 83 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 84 85 void 86 pty_release(const char *tty) 87 { 88 #ifndef __APPLE_PRIVPTY__ 89 if (chown(tty, (uid_t) 0, (gid_t) 0) < 0) 90 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 91 if (chmod(tty, (mode_t) 0666) < 0) 92 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 93 #endif /* __APPLE_PRIVPTY__ */ 94 } 95 96 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 97 98 void 99 pty_make_controlling_tty(int *ttyfd, const char *tty) 100 { 101 int fd; 102 #ifdef USE_VHANGUP 103 void *old; 104 #endif /* USE_VHANGUP */ 105 106 #ifdef _UNICOS 107 if (setsid() < 0) 108 error("setsid: %.100s", strerror(errno)); 109 110 fd = open(tty, O_RDWR|O_NOCTTY); 111 if (fd != -1) { 112 signal(SIGHUP, SIG_IGN); 113 ioctl(fd, TCVHUP, (char *)NULL); 114 signal(SIGHUP, SIG_DFL); 115 setpgid(0, 0); 116 close(fd); 117 } else { 118 error("Failed to disconnect from controlling tty."); 119 } 120 121 debug("Setting controlling tty using TCSETCTTY."); 122 ioctl(*ttyfd, TCSETCTTY, NULL); 123 fd = open("/dev/tty", O_RDWR); 124 if (fd < 0) 125 error("%.100s: %.100s", tty, strerror(errno)); 126 close(*ttyfd); 127 *ttyfd = fd; 128 #else /* _UNICOS */ 129 130 /* First disconnect from the old controlling tty. */ 131 #ifdef TIOCNOTTY 132 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 133 if (fd >= 0) { 134 (void) ioctl(fd, TIOCNOTTY, NULL); 135 close(fd); 136 } 137 #endif /* TIOCNOTTY */ 138 if (setsid() < 0) 139 error("setsid: %.100s", strerror(errno)); 140 141 /* 142 * Verify that we are successfully disconnected from the controlling 143 * tty. 144 */ 145 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 146 if (fd >= 0) { 147 error("Failed to disconnect from controlling tty."); 148 close(fd); 149 } 150 /* Make it our controlling tty. */ 151 #ifdef TIOCSCTTY 152 debug("Setting controlling tty using TIOCSCTTY."); 153 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 154 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 155 #endif /* TIOCSCTTY */ 156 #ifdef NEED_SETPGRP 157 if (setpgrp(0,0) < 0) 158 error("SETPGRP %s",strerror(errno)); 159 #endif /* NEED_SETPGRP */ 160 #ifdef USE_VHANGUP 161 old = signal(SIGHUP, SIG_IGN); 162 vhangup(); 163 signal(SIGHUP, old); 164 #endif /* USE_VHANGUP */ 165 fd = open(tty, O_RDWR); 166 if (fd < 0) { 167 error("%.100s: %.100s", tty, strerror(errno)); 168 } else { 169 #ifdef USE_VHANGUP 170 close(*ttyfd); 171 *ttyfd = fd; 172 #else /* USE_VHANGUP */ 173 close(fd); 174 #endif /* USE_VHANGUP */ 175 } 176 /* Verify that we now have a controlling tty. */ 177 fd = open(_PATH_TTY, O_WRONLY); 178 if (fd < 0) 179 error("open /dev/tty failed - could not set controlling tty: %.100s", 180 strerror(errno)); 181 else 182 close(fd); 183 #endif /* _UNICOS */ 184 } 185 186 /* Changes the window size associated with the pty. */ 187 188 void 189 pty_change_window_size(int ptyfd, u_int row, u_int col, 190 u_int xpixel, u_int ypixel) 191 { 192 struct winsize w; 193 194 /* may truncate u_int -> u_short */ 195 w.ws_row = row; 196 w.ws_col = col; 197 w.ws_xpixel = xpixel; 198 w.ws_ypixel = ypixel; 199 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 200 } 201 202 void 203 pty_setowner(struct passwd *pw, const char *tty) 204 { 205 struct group *grp; 206 gid_t gid; 207 mode_t mode; 208 struct stat st; 209 210 /* Determine the group to make the owner of the tty. */ 211 grp = getgrnam("tty"); 212 if (grp) { 213 gid = grp->gr_gid; 214 mode = S_IRUSR | S_IWUSR | S_IWGRP; 215 } else { 216 gid = pw->pw_gid; 217 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH; 218 } 219 220 /* 221 * Change owner and mode of the tty as required. 222 * Warn but continue if filesystem is read-only and the uids match/ 223 * tty is owned by root. 224 */ 225 if (stat(tty, &st)) 226 fatal("stat(%.100s) failed: %.100s", tty, 227 strerror(errno)); 228 229 #ifdef WITH_SELINUX 230 ssh_selinux_setup_pty(pw->pw_name, tty); 231 #endif 232 233 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 234 if (chown(tty, pw->pw_uid, gid) < 0) { 235 if (errno == EROFS && 236 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 237 debug("chown(%.100s, %u, %u) failed: %.100s", 238 tty, (u_int)pw->pw_uid, (u_int)gid, 239 strerror(errno)); 240 else 241 fatal("chown(%.100s, %u, %u) failed: %.100s", 242 tty, (u_int)pw->pw_uid, (u_int)gid, 243 strerror(errno)); 244 } 245 } 246 247 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 248 if (chmod(tty, mode) < 0) { 249 if (errno == EROFS && 250 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 251 debug("chmod(%.100s, 0%o) failed: %.100s", 252 tty, (u_int)mode, strerror(errno)); 253 else 254 fatal("chmod(%.100s, 0%o) failed: %.100s", 255 tty, (u_int)mode, strerror(errno)); 256 } 257 } 258 } 259