1 /* $OpenBSD: sshpty.c,v 1.29 2014/09/03 18:55:07 djm 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; 107 108 #ifdef _UNICOS 109 if (setsid() < 0) 110 error("setsid: %.100s", strerror(errno)); 111 112 fd = open(tty, O_RDWR|O_NOCTTY); 113 if (fd != -1) { 114 signal(SIGHUP, SIG_IGN); 115 ioctl(fd, TCVHUP, (char *)NULL); 116 signal(SIGHUP, SIG_DFL); 117 setpgid(0, 0); 118 close(fd); 119 } else { 120 error("Failed to disconnect from controlling tty."); 121 } 122 123 debug("Setting controlling tty using TCSETCTTY."); 124 ioctl(*ttyfd, TCSETCTTY, NULL); 125 fd = open("/dev/tty", O_RDWR); 126 if (fd < 0) 127 error("%.100s: %.100s", tty, strerror(errno)); 128 close(*ttyfd); 129 *ttyfd = fd; 130 #else /* _UNICOS */ 131 132 /* First disconnect from the old controlling tty. */ 133 #ifdef TIOCNOTTY 134 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 135 if (fd >= 0) { 136 (void) ioctl(fd, TIOCNOTTY, NULL); 137 close(fd); 138 } 139 #endif /* TIOCNOTTY */ 140 if (setsid() < 0) 141 error("setsid: %.100s", strerror(errno)); 142 143 /* 144 * Verify that we are successfully disconnected from the controlling 145 * tty. 146 */ 147 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 148 if (fd >= 0) { 149 error("Failed to disconnect from controlling tty."); 150 close(fd); 151 } 152 /* Make it our controlling tty. */ 153 #ifdef TIOCSCTTY 154 debug("Setting controlling tty using TIOCSCTTY."); 155 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 156 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 157 #endif /* TIOCSCTTY */ 158 #ifdef NEED_SETPGRP 159 if (setpgrp(0,0) < 0) 160 error("SETPGRP %s",strerror(errno)); 161 #endif /* NEED_SETPGRP */ 162 fd = open(tty, O_RDWR); 163 if (fd < 0) { 164 error("%.100s: %.100s", tty, strerror(errno)); 165 } else { 166 close(fd); 167 } 168 /* Verify that we now have a controlling tty. */ 169 fd = open(_PATH_TTY, O_WRONLY); 170 if (fd < 0) 171 error("open /dev/tty failed - could not set controlling tty: %.100s", 172 strerror(errno)); 173 else 174 close(fd); 175 #endif /* _UNICOS */ 176 } 177 178 /* Changes the window size associated with the pty. */ 179 180 void 181 pty_change_window_size(int ptyfd, u_int row, u_int col, 182 u_int xpixel, u_int ypixel) 183 { 184 struct winsize w; 185 186 /* may truncate u_int -> u_short */ 187 w.ws_row = row; 188 w.ws_col = col; 189 w.ws_xpixel = xpixel; 190 w.ws_ypixel = ypixel; 191 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 192 } 193 194 void 195 pty_setowner(struct passwd *pw, const char *tty) 196 { 197 struct group *grp; 198 gid_t gid; 199 mode_t mode; 200 struct stat st; 201 202 /* Determine the group to make the owner of the tty. */ 203 grp = getgrnam("tty"); 204 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 205 mode = (grp != NULL) ? 0622 : 0600; 206 207 /* 208 * Change owner and mode of the tty as required. 209 * Warn but continue if filesystem is read-only and the uids match/ 210 * tty is owned by root. 211 */ 212 if (stat(tty, &st)) 213 fatal("stat(%.100s) failed: %.100s", tty, 214 strerror(errno)); 215 216 #ifdef WITH_SELINUX 217 ssh_selinux_setup_pty(pw->pw_name, tty); 218 #endif 219 220 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 221 if (chown(tty, pw->pw_uid, gid) < 0) { 222 if (errno == EROFS && 223 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 224 debug("chown(%.100s, %u, %u) failed: %.100s", 225 tty, (u_int)pw->pw_uid, (u_int)gid, 226 strerror(errno)); 227 else 228 fatal("chown(%.100s, %u, %u) failed: %.100s", 229 tty, (u_int)pw->pw_uid, (u_int)gid, 230 strerror(errno)); 231 } 232 } 233 234 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 235 if (chmod(tty, mode) < 0) { 236 if (errno == EROFS && 237 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 238 debug("chmod(%.100s, 0%o) failed: %.100s", 239 tty, (u_int)mode, strerror(errno)); 240 else 241 fatal("chmod(%.100s, 0%o) failed: %.100s", 242 tty, (u_int)mode, strerror(errno)); 243 } 244 } 245 } 246
