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