1 /* $OpenBSD: sshpty.c,v 1.31 2016/11/29 03:54:50 dtucker 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 #if !defined(__APPLE_PRIVPTY__) && !defined(HAVE_OPENPTY) 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__ && !HAVE_OPENPTY */ 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; 102 103 #ifdef _UNICOS 104 if (setsid() < 0) 105 error("setsid: %.100s", strerror(errno)); 106 107 fd = open(tty, O_RDWR|O_NOCTTY); 108 if (fd != -1) { 109 signal(SIGHUP, SIG_IGN); 110 ioctl(fd, TCVHUP, (char *)NULL); 111 signal(SIGHUP, SIG_DFL); 112 setpgid(0, 0); 113 close(fd); 114 } else { 115 error("Failed to disconnect from controlling tty."); 116 } 117 118 debug("Setting controlling tty using TCSETCTTY."); 119 ioctl(*ttyfd, TCSETCTTY, NULL); 120 fd = open("/dev/tty", O_RDWR); 121 if (fd < 0) 122 error("%.100s: %.100s", tty, strerror(errno)); 123 close(*ttyfd); 124 *ttyfd = fd; 125 #else /* _UNICOS */ 126 127 /* First disconnect from the old controlling tty. */ 128 #ifdef TIOCNOTTY 129 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 130 if (fd >= 0) { 131 (void) ioctl(fd, TIOCNOTTY, NULL); 132 close(fd); 133 } 134 #endif /* TIOCNOTTY */ 135 if (setsid() < 0) 136 error("setsid: %.100s", strerror(errno)); 137 138 /* 139 * Verify that we are successfully disconnected from the controlling 140 * tty. 141 */ 142 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 143 if (fd >= 0) { 144 error("Failed to disconnect from controlling tty."); 145 close(fd); 146 } 147 /* Make it our controlling tty. */ 148 #ifdef TIOCSCTTY 149 debug("Setting controlling tty using TIOCSCTTY."); 150 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 151 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 152 #endif /* TIOCSCTTY */ 153 #ifdef NEED_SETPGRP 154 if (setpgrp(0,0) < 0) 155 error("SETPGRP %s",strerror(errno)); 156 #endif /* NEED_SETPGRP */ 157 fd = open(tty, O_RDWR); 158 if (fd < 0) 159 error("%.100s: %.100s", tty, strerror(errno)); 160 else 161 close(fd); 162 163 /* Verify that we now have a controlling tty. */ 164 fd = open(_PATH_TTY, O_WRONLY); 165 if (fd < 0) 166 error("open /dev/tty failed - could not set controlling tty: %.100s", 167 strerror(errno)); 168 else 169 close(fd); 170 #endif /* _UNICOS */ 171 } 172 173 /* Changes the window size associated with the pty. */ 174 175 void 176 pty_change_window_size(int ptyfd, u_int row, u_int col, 177 u_int xpixel, u_int ypixel) 178 { 179 struct winsize w; 180 181 /* may truncate u_int -> u_short */ 182 w.ws_row = row; 183 w.ws_col = col; 184 w.ws_xpixel = xpixel; 185 w.ws_ypixel = ypixel; 186 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 187 } 188 189 void 190 pty_setowner(struct passwd *pw, const char *tty) 191 { 192 struct group *grp; 193 gid_t gid; 194 mode_t mode; 195 struct stat st; 196 197 /* Determine the group to make the owner of the tty. */ 198 grp = getgrnam("tty"); 199 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 200 mode = (grp != NULL) ? 0620 : 0600; 201 202 /* 203 * Change owner and mode of the tty as required. 204 * Warn but continue if filesystem is read-only and the uids match/ 205 * tty is owned by root. 206 */ 207 if (stat(tty, &st)) 208 fatal("stat(%.100s) failed: %.100s", tty, 209 strerror(errno)); 210 211 #ifdef WITH_SELINUX 212 ssh_selinux_setup_pty(pw->pw_name, tty); 213 #endif 214 215 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 216 if (chown(tty, pw->pw_uid, gid) < 0) { 217 if (errno == EROFS && 218 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 219 debug("chown(%.100s, %u, %u) failed: %.100s", 220 tty, (u_int)pw->pw_uid, (u_int)gid, 221 strerror(errno)); 222 else 223 fatal("chown(%.100s, %u, %u) failed: %.100s", 224 tty, (u_int)pw->pw_uid, (u_int)gid, 225 strerror(errno)); 226 } 227 } 228 229 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 230 if (chmod(tty, mode) < 0) { 231 if (errno == EROFS && 232 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 233 debug("chmod(%.100s, 0%o) failed: %.100s", 234 tty, (u_int)mode, strerror(errno)); 235 else 236 fatal("chmod(%.100s, 0%o) failed: %.100s", 237 tty, (u_int)mode, strerror(errno)); 238 } 239 } 240 } 241 242 /* Disconnect from the controlling tty. */ 243 void 244 disconnect_controlling_tty(void) 245 { 246 #ifdef TIOCNOTTY 247 int fd; 248 249 if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) { 250 (void) ioctl(fd, TIOCNOTTY, NULL); 251 close(fd); 252 } 253 #endif /* TIOCNOTTY */ 254 } 255