1 /* $OpenBSD: sshpty.c,v 1.28 2007/09/11 23:49:09 stevesk Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo (at) 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 #ifdef ANDROID 76 /* Android does not have a working ttyname() */ 77 name = "/dev/ptmx"; 78 #else 79 name = ttyname(*ttyfd); 80 if (!name) 81 fatal("openpty returns device for which ttyname fails."); 82 #endif 83 84 strlcpy(namebuf, name, namebuflen); /* possible truncation */ 85 return 1; 86 } 87 88 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 89 90 void 91 pty_release(const char *tty) 92 { 93 #ifndef __APPLE_PRIVPTY__ 94 if (chown(tty, (uid_t) 0, (gid_t) 0) < 0) 95 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 96 if (chmod(tty, (mode_t) 0666) < 0) 97 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 98 #endif /* __APPLE_PRIVPTY__ */ 99 } 100 101 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 102 103 void 104 pty_make_controlling_tty(int *ttyfd, const char *tty) 105 { 106 int fd; 107 #ifdef USE_VHANGUP 108 void *old; 109 #endif /* USE_VHANGUP */ 110 111 #ifdef _UNICOS 112 if (setsid() < 0) 113 error("setsid: %.100s", strerror(errno)); 114 115 fd = open(tty, O_RDWR|O_NOCTTY); 116 if (fd != -1) { 117 signal(SIGHUP, SIG_IGN); 118 ioctl(fd, TCVHUP, (char *)NULL); 119 signal(SIGHUP, SIG_DFL); 120 setpgid(0, 0); 121 close(fd); 122 } else { 123 error("Failed to disconnect from controlling tty."); 124 } 125 126 debug("Setting controlling tty using TCSETCTTY."); 127 ioctl(*ttyfd, TCSETCTTY, NULL); 128 fd = open("/dev/tty", O_RDWR); 129 if (fd < 0) 130 error("%.100s: %.100s", tty, strerror(errno)); 131 close(*ttyfd); 132 *ttyfd = fd; 133 #else /* _UNICOS */ 134 135 /* First disconnect from the old controlling tty. */ 136 #ifdef TIOCNOTTY 137 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 138 if (fd >= 0) { 139 (void) ioctl(fd, TIOCNOTTY, NULL); 140 close(fd); 141 } 142 #endif /* TIOCNOTTY */ 143 if (setsid() < 0) 144 error("setsid: %.100s", strerror(errno)); 145 146 /* 147 * Verify that we are successfully disconnected from the controlling 148 * tty. 149 */ 150 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 151 if (fd >= 0) { 152 error("Failed to disconnect from controlling tty."); 153 close(fd); 154 } 155 /* Make it our controlling tty. */ 156 #ifdef TIOCSCTTY 157 debug("Setting controlling tty using TIOCSCTTY."); 158 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 159 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 160 #endif /* TIOCSCTTY */ 161 #ifdef NEED_SETPGRP 162 if (setpgrp(0,0) < 0) 163 error("SETPGRP %s",strerror(errno)); 164 #endif /* NEED_SETPGRP */ 165 #ifdef USE_VHANGUP 166 old = signal(SIGHUP, SIG_IGN); 167 vhangup(); 168 signal(SIGHUP, old); 169 #endif /* USE_VHANGUP */ 170 fd = open(tty, O_RDWR); 171 if (fd < 0) { 172 error("%.100s: %.100s", tty, strerror(errno)); 173 } else { 174 #ifdef USE_VHANGUP 175 close(*ttyfd); 176 *ttyfd = fd; 177 #else /* USE_VHANGUP */ 178 close(fd); 179 #endif /* USE_VHANGUP */ 180 } 181 /* Verify that we now have a controlling tty. */ 182 fd = open(_PATH_TTY, O_WRONLY); 183 if (fd < 0) 184 error("open /dev/tty failed - could not set controlling tty: %.100s", 185 strerror(errno)); 186 else 187 close(fd); 188 #endif /* _UNICOS */ 189 } 190 191 /* Changes the window size associated with the pty. */ 192 193 void 194 pty_change_window_size(int ptyfd, u_int row, u_int col, 195 u_int xpixel, u_int ypixel) 196 { 197 struct winsize w; 198 199 /* may truncate u_int -> u_short */ 200 w.ws_row = row; 201 w.ws_col = col; 202 w.ws_xpixel = xpixel; 203 w.ws_ypixel = ypixel; 204 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 205 } 206 207 void 208 pty_setowner(struct passwd *pw, const char *tty) 209 { 210 struct group *grp; 211 gid_t gid; 212 mode_t mode; 213 struct stat st; 214 215 /* Determine the group to make the owner of the tty. */ 216 grp = getgrnam("tty"); 217 if (grp) { 218 gid = grp->gr_gid; 219 mode = S_IRUSR | S_IWUSR | S_IWGRP; 220 } else { 221 gid = pw->pw_gid; 222 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH; 223 } 224 225 /* 226 * Change owner and mode of the tty as required. 227 * Warn but continue if filesystem is read-only and the uids match/ 228 * tty is owned by root. 229 */ 230 if (stat(tty, &st)) 231 fatal("stat(%.100s) failed: %.100s", tty, 232 strerror(errno)); 233 234 #ifdef WITH_SELINUX 235 ssh_selinux_setup_pty(pw->pw_name, tty); 236 #endif 237 238 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 239 if (chown(tty, pw->pw_uid, gid) < 0) { 240 if (errno == EROFS && 241 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 242 debug("chown(%.100s, %u, %u) failed: %.100s", 243 tty, (u_int)pw->pw_uid, (u_int)gid, 244 strerror(errno)); 245 else 246 fatal("chown(%.100s, %u, %u) failed: %.100s", 247 tty, (u_int)pw->pw_uid, (u_int)gid, 248 strerror(errno)); 249 } 250 } 251 252 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 253 if (chmod(tty, mode) < 0) { 254 if (errno == EROFS && 255 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 256 debug("chmod(%.100s, 0%o) failed: %.100s", 257 tty, (u_int)mode, strerror(errno)); 258 else 259 fatal("chmod(%.100s, 0%o) failed: %.100s", 260 tty, (u_int)mode, strerror(errno)); 261 } 262 } 263 } 264
