1 /* $OpenBSD: sshpty.c,v 1.35 2026/02/11 17:05:32 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 21 #include <errno.h> 22 #include <fcntl.h> 23 #include <grp.h> 24 #include <paths.h> 25 #include <pwd.h> 26 #include <signal.h> 27 #include <stdarg.h> 28 #include <stdio.h> 29 #include <string.h> 30 #include <termios.h> 31 #include <unistd.h> 32 #include <util.h> 33 34 #include "sshpty.h" 35 #include "log.h" 36 #include "misc.h" 37 38 #ifdef HAVE_PTY_H 39 # include <pty.h> 40 #endif 41 42 #ifndef O_NOCTTY 43 #define O_NOCTTY 0 44 #endif 45 46 #ifdef __APPLE__ 47 # include <AvailabilityMacros.h> 48 # if (MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_5) 49 # define __APPLE_PRIVPTY__ 50 # endif 51 #endif 52 53 /* 54 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 55 * nonzero if a pty was successfully allocated. On success, open file 56 * descriptors for the pty and tty sides and the name of the tty side are 57 * returned (the buffer must be able to hold at least 64 characters). 58 */ 59 60 int 61 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen) 62 { 63 /* openpty(3) exists in OSF/1 and some other os'es */ 64 char *name; 65 int i; 66 67 i = openpty(ptyfd, ttyfd, NULL, NULL, NULL); 68 if (i == -1) { 69 error("openpty: %.100s", strerror(errno)); 70 return 0; 71 } 72 name = ttyname(*ttyfd); 73 if (!name) 74 fatal("openpty returns device for which ttyname fails."); 75 76 strlcpy(namebuf, name, namebuflen); /* possible truncation */ 77 return 1; 78 } 79 80 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 81 82 void 83 pty_release(const char *tty) 84 { 85 #if !defined(__APPLE_PRIVPTY__) && !defined(HAVE_OPENPTY) 86 if (chown(tty, (uid_t) 0, (gid_t) 0) == -1) 87 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 88 if (chmod(tty, (mode_t) 0666) == -1) 89 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 90 #endif /* !__APPLE_PRIVPTY__ && !HAVE_OPENPTY */ 91 } 92 93 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 94 95 void 96 pty_make_controlling_tty(int *ttyfd, const char *tty) 97 { 98 int fd; 99 100 /* First disconnect from the old controlling tty. */ 101 #ifdef TIOCNOTTY 102 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 103 if (fd >= 0) { 104 (void) ioctl(fd, TIOCNOTTY, NULL); 105 close(fd); 106 } 107 #endif /* TIOCNOTTY */ 108 if (setsid() == -1) 109 error("setsid: %.100s", strerror(errno)); 110 111 /* 112 * Verify that we are successfully disconnected from the controlling 113 * tty. 114 */ 115 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 116 if (fd >= 0) { 117 error("Failed to disconnect from controlling tty."); 118 close(fd); 119 } 120 /* Make it our controlling tty. */ 121 #ifdef TIOCSCTTY 122 debug("Setting controlling tty using TIOCSCTTY."); 123 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 124 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 125 #endif /* TIOCSCTTY */ 126 #ifdef NEED_SETPGRP 127 if (setpgrp(0,0) < 0) 128 error("SETPGRP %s",strerror(errno)); 129 #endif /* NEED_SETPGRP */ 130 fd = open(tty, O_RDWR); 131 if (fd == -1) 132 error("%.100s: %.100s", tty, strerror(errno)); 133 else 134 close(fd); 135 136 /* Verify that we now have a controlling tty. */ 137 fd = open(_PATH_TTY, O_WRONLY); 138 if (fd == -1) 139 error("open /dev/tty failed - could not set controlling tty: %.100s", 140 strerror(errno)); 141 else 142 close(fd); 143 } 144 145 /* Changes the window size associated with the pty. */ 146 147 void 148 pty_change_window_size(int ptyfd, u_int row, u_int col, 149 u_int xpixel, u_int ypixel) 150 { 151 struct winsize w; 152 153 /* may truncate u_int -> u_short */ 154 w.ws_row = row; 155 w.ws_col = col; 156 w.ws_xpixel = xpixel; 157 w.ws_ypixel = ypixel; 158 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 159 } 160 161 void 162 pty_setowner(struct passwd *pw, const char *tty) 163 { 164 struct group *grp; 165 gid_t gid; 166 mode_t mode; 167 struct stat st; 168 169 /* Determine the group to make the owner of the tty. */ 170 grp = getgrnam("tty"); 171 if (grp == NULL) 172 debug_f("no tty group"); 173 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 174 mode = (grp != NULL) ? 0620 : 0600; 175 176 /* 177 * Change owner and mode of the tty as required. 178 * Warn but continue if filesystem is read-only and the uids match/ 179 * tty is owned by root. 180 */ 181 if (stat(tty, &st) == -1) 182 fatal("stat(%.100s) failed: %.100s", tty, 183 strerror(errno)); 184 185 #ifdef WITH_SELINUX 186 ssh_selinux_setup_pty(pw->pw_name, tty); 187 #endif 188 189 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 190 if (chown(tty, pw->pw_uid, gid) == -1) { 191 if (errno == EROFS && 192 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 193 debug("chown(%.100s, %u, %u) failed: %.100s", 194 tty, (u_int)pw->pw_uid, (u_int)gid, 195 strerror(errno)); 196 else 197 fatal("chown(%.100s, %u, %u) failed: %.100s", 198 tty, (u_int)pw->pw_uid, (u_int)gid, 199 strerror(errno)); 200 } 201 } 202 203 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 204 if (chmod(tty, mode) == -1) { 205 if (errno == EROFS && 206 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 207 debug("chmod(%.100s, 0%o) failed: %.100s", 208 tty, (u_int)mode, strerror(errno)); 209 else 210 fatal("chmod(%.100s, 0%o) failed: %.100s", 211 tty, (u_int)mode, strerror(errno)); 212 } 213 } 214 } 215 216 /* Disconnect from the controlling tty. */ 217 void 218 disconnect_controlling_tty(void) 219 { 220 #ifdef TIOCNOTTY 221 int fd; 222 223 if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) { 224 (void) ioctl(fd, TIOCNOTTY, NULL); 225 close(fd); 226 } 227 #endif /* TIOCNOTTY */ 228 } 229