1 /* $OpenBSD: sshpty.c,v 1.31 2016/11/29 03:54:50 dtucker 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 if (ptsname_r(*ptyfd, namebuf, namebuflen)) { 77 fatal("openpty ptsname failed."); 78 close(*ptyfd); 79 *ptyfd = -1; 80 return -1; 81 } 82 return 1; 83 #else 84 name = ttyname(*ttyfd); 85 if (!name) 86 fatal("openpty returns device for which ttyname fails."); 87 88 strlcpy(namebuf, name, namebuflen); /* possible truncation */ 89 return 1; 90 #endif 91 } 92 93 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 94 95 void 96 pty_release(const char *tty) 97 { 98 #if !defined(__APPLE_PRIVPTY__) && !defined(HAVE_OPENPTY) 99 if (chown(tty, (uid_t) 0, (gid_t) 0) < 0) 100 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 101 if (chmod(tty, (mode_t) 0666) < 0) 102 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 103 #endif /* !__APPLE_PRIVPTY__ && !HAVE_OPENPTY */ 104 } 105 106 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 107 108 void 109 pty_make_controlling_tty(int *ttyfd, const char *tty) 110 { 111 int fd; 112 113 #ifdef _UNICOS 114 if (setsid() < 0) 115 error("setsid: %.100s", strerror(errno)); 116 117 fd = open(tty, O_RDWR|O_NOCTTY); 118 if (fd != -1) { 119 signal(SIGHUP, SIG_IGN); 120 ioctl(fd, TCVHUP, (char *)NULL); 121 signal(SIGHUP, SIG_DFL); 122 setpgid(0, 0); 123 close(fd); 124 } else { 125 error("Failed to disconnect from controlling tty."); 126 } 127 128 debug("Setting controlling tty using TCSETCTTY."); 129 ioctl(*ttyfd, TCSETCTTY, NULL); 130 fd = open("/dev/tty", O_RDWR); 131 if (fd < 0) 132 error("%.100s: %.100s", tty, strerror(errno)); 133 close(*ttyfd); 134 *ttyfd = fd; 135 #else /* _UNICOS */ 136 137 /* First disconnect from the old controlling tty. */ 138 #ifdef TIOCNOTTY 139 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 140 if (fd >= 0) { 141 (void) ioctl(fd, TIOCNOTTY, NULL); 142 close(fd); 143 } 144 #endif /* TIOCNOTTY */ 145 if (setsid() < 0) 146 error("setsid: %.100s", strerror(errno)); 147 148 /* 149 * Verify that we are successfully disconnected from the controlling 150 * tty. 151 */ 152 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 153 if (fd >= 0) { 154 error("Failed to disconnect from controlling tty."); 155 close(fd); 156 } 157 /* Make it our controlling tty. */ 158 #ifdef TIOCSCTTY 159 debug("Setting controlling tty using TIOCSCTTY."); 160 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 161 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 162 #endif /* TIOCSCTTY */ 163 #ifdef NEED_SETPGRP 164 if (setpgrp(0,0) < 0) 165 error("SETPGRP %s",strerror(errno)); 166 #endif /* NEED_SETPGRP */ 167 fd = open(tty, O_RDWR); 168 if (fd < 0) 169 error("%.100s: %.100s", tty, strerror(errno)); 170 else 171 close(fd); 172 173 /* Verify that we now have a controlling tty. */ 174 fd = open(_PATH_TTY, O_WRONLY); 175 if (fd < 0) 176 error("open /dev/tty failed - could not set controlling tty: %.100s", 177 strerror(errno)); 178 else 179 close(fd); 180 #endif /* _UNICOS */ 181 } 182 183 /* Changes the window size associated with the pty. */ 184 185 void 186 pty_change_window_size(int ptyfd, u_int row, u_int col, 187 u_int xpixel, u_int ypixel) 188 { 189 struct winsize w; 190 191 /* may truncate u_int -> u_short */ 192 w.ws_row = row; 193 w.ws_col = col; 194 w.ws_xpixel = xpixel; 195 w.ws_ypixel = ypixel; 196 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 197 } 198 199 void 200 pty_setowner(struct passwd *pw, const char *tty) 201 { 202 struct group *grp; 203 gid_t gid; 204 mode_t mode; 205 struct stat st; 206 207 /* Determine the group to make the owner of the tty. */ 208 grp = getgrnam("tty"); 209 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 210 mode = (grp != NULL) ? 0620 : 0600; 211 212 /* 213 * Change owner and mode of the tty as required. 214 * Warn but continue if filesystem is read-only and the uids match/ 215 * tty is owned by root. 216 */ 217 if (stat(tty, &st)) 218 fatal("stat(%.100s) failed: %.100s", tty, 219 strerror(errno)); 220 221 #ifdef WITH_SELINUX 222 ssh_selinux_setup_pty(pw->pw_name, tty); 223 #endif 224 225 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 226 if (chown(tty, pw->pw_uid, gid) < 0) { 227 if (errno == EROFS && 228 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 229 debug("chown(%.100s, %u, %u) failed: %.100s", 230 tty, (u_int)pw->pw_uid, (u_int)gid, 231 strerror(errno)); 232 else 233 fatal("chown(%.100s, %u, %u) failed: %.100s", 234 tty, (u_int)pw->pw_uid, (u_int)gid, 235 strerror(errno)); 236 } 237 } 238 239 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 240 if (chmod(tty, mode) < 0) { 241 if (errno == EROFS && 242 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 243 debug("chmod(%.100s, 0%o) failed: %.100s", 244 tty, (u_int)mode, strerror(errno)); 245 else 246 fatal("chmod(%.100s, 0%o) failed: %.100s", 247 tty, (u_int)mode, strerror(errno)); 248 } 249 } 250 } 251 252 /* Disconnect from the controlling tty. */ 253 void 254 disconnect_controlling_tty(void) 255 { 256 #ifdef TIOCNOTTY 257 int fd; 258 259 if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) { 260 (void) ioctl(fd, TIOCNOTTY, NULL); 261 close(fd); 262 } 263 #endif /* TIOCNOTTY */ 264 } 265
