1 /* $NetBSD: sshpty.c,v 1.7 2017/04/18 18:41:46 christos Exp $ */ 2 /* $OpenBSD: sshpty.c,v 1.31 2016/11/29 03:54:50 dtucker Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo@cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * Allocating a pseudo-terminal, and making it the controlling tty. 9 * 10 * As far as I am concerned, the code I have written for this software 11 * can be used freely for any purpose. Any derived versions of this 12 * software must be clearly marked as such, and if the derived work is 13 * incompatible with the protocol description in the RFC file, it must be 14 * called by a name other than "ssh" or "Secure Shell". 15 */ 16 17 #include "includes.h" 18 __RCSID("$NetBSD: sshpty.c,v 1.7 2017/04/18 18:41:46 christos Exp $"); 19 #include <sys/types.h> 20 #include <sys/ioctl.h> 21 #include <sys/stat.h> 22 23 #include <errno.h> 24 #include <fcntl.h> 25 #include <grp.h> 26 #include <paths.h> 27 #include <pwd.h> 28 #include <stdarg.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 37 #ifndef O_NOCTTY 38 #define O_NOCTTY 0 39 #endif 40 41 /* 42 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 43 * nonzero if a pty was successfully allocated. On success, open file 44 * descriptors for the pty and tty sides and the name of the tty side are 45 * returned (the buffer must be able to hold at least 64 characters). 46 */ 47 48 int 49 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen) 50 { 51 char buf[64]; 52 int i; 53 54 i = openpty(ptyfd, ttyfd, buf, NULL, NULL); 55 if (i < 0) { 56 error("openpty: %.100s", strerror(errno)); 57 return 0; 58 } 59 strlcpy(namebuf, buf, namebuflen); /* possible truncation */ 60 return 1; 61 } 62 63 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 64 65 void 66 pty_release(const char *tty) 67 { 68 if (chown(tty, (uid_t) 0, (gid_t) 0) < 0) 69 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 70 if (chmod(tty, (mode_t) 0666) < 0) 71 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 72 } 73 74 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 75 76 void 77 pty_make_controlling_tty(int *ttyfd, const char *tty) 78 { 79 int fd; 80 81 /* First disconnect from the old controlling tty. */ 82 #ifdef TIOCNOTTY 83 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 84 if (fd >= 0) { 85 (void) ioctl(fd, TIOCNOTTY, NULL); 86 close(fd); 87 } 88 #endif /* TIOCNOTTY */ 89 if (setsid() < 0) 90 error("setsid: %.100s", strerror(errno)); 91 92 /* 93 * Verify that we are successfully disconnected from the controlling 94 * tty. 95 */ 96 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 97 if (fd >= 0) { 98 error("Failed to disconnect from controlling tty."); 99 close(fd); 100 } 101 /* Make it our controlling tty. */ 102 #ifdef TIOCSCTTY 103 debug("Setting controlling tty using TIOCSCTTY."); 104 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 105 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 106 #endif /* TIOCSCTTY */ 107 fd = open(tty, O_RDWR); 108 if (fd < 0) 109 error("%.100s: %.100s", tty, strerror(errno)); 110 else 111 close(fd); 112 113 /* Verify that we now have a controlling tty. */ 114 fd = open(_PATH_TTY, O_WRONLY); 115 if (fd < 0) 116 error("open /dev/tty failed - could not set controlling tty: %.100s", 117 strerror(errno)); 118 else 119 close(fd); 120 } 121 122 /* Changes the window size associated with the pty. */ 123 124 void 125 pty_change_window_size(int ptyfd, u_int row, u_int col, 126 u_int xpixel, u_int ypixel) 127 { 128 struct winsize w; 129 130 /* may truncate u_int -> u_short */ 131 w.ws_row = row; 132 w.ws_col = col; 133 w.ws_xpixel = xpixel; 134 w.ws_ypixel = ypixel; 135 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 136 } 137 138 void 139 pty_setowner(struct passwd *pw, const char *tty) 140 { 141 struct group *grp; 142 gid_t gid; 143 mode_t mode; 144 struct stat st; 145 146 /* Determine the group to make the owner of the tty. */ 147 grp = getgrnam("tty"); 148 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 149 mode = (grp != NULL) ? 0620 : 0600; 150 151 /* 152 * Change owner and mode of the tty as required. 153 * Warn but continue if filesystem is read-only and the uids match/ 154 * tty is owned by root. 155 */ 156 if (stat(tty, &st)) 157 fatal("stat(%.100s) failed: %.100s", tty, 158 strerror(errno)); 159 160 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 161 if (chown(tty, pw->pw_uid, gid) < 0) { 162 if (errno == EROFS && 163 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 164 debug("chown(%.100s, %u, %u) failed: %.100s", 165 tty, (u_int)pw->pw_uid, (u_int)gid, 166 strerror(errno)); 167 else 168 fatal("chown(%.100s, %u, %u) failed: %.100s", 169 tty, (u_int)pw->pw_uid, (u_int)gid, 170 strerror(errno)); 171 } 172 } 173 174 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 175 if (chmod(tty, mode) < 0) { 176 if (errno == EROFS && 177 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 178 debug("chmod(%.100s, 0%o) failed: %.100s", 179 tty, (u_int)mode, strerror(errno)); 180 else 181 fatal("chmod(%.100s, 0%o) failed: %.100s", 182 tty, (u_int)mode, strerror(errno)); 183 } 184 } 185 } 186 187 /* Disconnect from the controlling tty. */ 188 void 189 disconnect_controlling_tty(void) 190 { 191 int fd; 192 193 if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) { 194 (void) ioctl(fd, TIOCNOTTY, NULL); 195 close(fd); 196 } 197 } 198