1 /* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * Allocating a pseudo-terminal, and making it the controlling tty. 6 * 7 * As far as I am concerned, the code I have written for this software 8 * can be used freely for any purpose. Any derived versions of this 9 * software must be clearly marked as such, and if the derived work is 10 * incompatible with the protocol description in the RFC file, it must be 11 * called by a name other than "ssh" or "Secure Shell". 12 */ 13 14 #include "includes.h" 15 RCSID("$OpenBSD: sshpty.c,v 1.11 2004/01/11 21:55:06 deraadt Exp $"); 16 17 #include <util.h> 18 #include "sshpty.h" 19 #include "log.h" 20 21 /* Pty allocated with _getpty gets broken if we do I_PUSH:es to it. */ 22 #if defined(HAVE__GETPTY) || defined(HAVE_OPENPTY) 23 #undef HAVE_DEV_PTMX 24 #endif 25 26 #ifndef O_NOCTTY 27 #define O_NOCTTY 0 28 #endif 29 30 /* 31 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 32 * nonzero if a pty was successfully allocated. On success, open file 33 * descriptors for the pty and tty sides and the name of the tty side are 34 * returned (the buffer must be able to hold at least 64 characters). 35 */ 36 37 int 38 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, int namebuflen) 39 { 40 char buf[64]; 41 int i; 42 43 i = openpty(ptyfd, ttyfd, buf, NULL, NULL); 44 if (i < 0) { 45 error("openpty: %.100s", strerror(errno)); 46 return 0; 47 } 48 strlcpy(namebuf, buf, namebuflen); /* possible truncation */ 49 return 1; 50 } 51 52 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 53 54 void 55 pty_release(const char *ttyname) 56 { 57 if (chown(ttyname, (uid_t) 0, (gid_t) 0) < 0) 58 error("chown %.100s 0 0 failed: %.100s", ttyname, strerror(errno)); 59 if (chmod(ttyname, (mode_t) 0666) < 0) 60 error("chmod %.100s 0666 failed: %.100s", ttyname, strerror(errno)); 61 } 62 63 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 64 65 void 66 pty_make_controlling_tty(int *ttyfd, const char *ttyname) 67 { 68 int fd; 69 70 /* First disconnect from the old controlling tty. */ 71 #ifdef TIOCNOTTY 72 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 73 if (fd >= 0) { 74 (void) ioctl(fd, TIOCNOTTY, NULL); 75 close(fd); 76 } 77 #endif /* TIOCNOTTY */ 78 if (setsid() < 0) 79 error("setsid: %.100s", strerror(errno)); 80 81 /* 82 * Verify that we are successfully disconnected from the controlling 83 * tty. 84 */ 85 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 86 if (fd >= 0) { 87 error("Failed to disconnect from controlling tty."); 88 close(fd); 89 } 90 /* Make it our controlling tty. */ 91 #ifdef TIOCSCTTY 92 debug("Setting controlling tty using TIOCSCTTY."); 93 if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0) 94 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 95 #endif /* TIOCSCTTY */ 96 fd = open(ttyname, O_RDWR); 97 if (fd < 0) 98 error("%.100s: %.100s", ttyname, strerror(errno)); 99 else 100 close(fd); 101 102 /* Verify that we now have a controlling tty. */ 103 fd = open(_PATH_TTY, O_WRONLY); 104 if (fd < 0) 105 error("open /dev/tty failed - could not set controlling tty: %.100s", 106 strerror(errno)); 107 else 108 close(fd); 109 } 110 111 /* Changes the window size associated with the pty. */ 112 113 void 114 pty_change_window_size(int ptyfd, int row, int col, 115 int xpixel, int ypixel) 116 { 117 struct winsize w; 118 119 w.ws_row = row; 120 w.ws_col = col; 121 w.ws_xpixel = xpixel; 122 w.ws_ypixel = ypixel; 123 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 124 } 125 126 void 127 pty_setowner(struct passwd *pw, const char *ttyname) 128 { 129 struct group *grp; 130 gid_t gid; 131 mode_t mode; 132 struct stat st; 133 134 /* Determine the group to make the owner of the tty. */ 135 grp = getgrnam("tty"); 136 if (grp) { 137 gid = grp->gr_gid; 138 mode = S_IRUSR | S_IWUSR | S_IWGRP; 139 } else { 140 gid = pw->pw_gid; 141 mode = S_IRUSR | S_IWUSR | S_IWGRP | S_IWOTH; 142 } 143 144 /* 145 * Change owner and mode of the tty as required. 146 * Warn but continue if filesystem is read-only and the uids match/ 147 * tty is owned by root. 148 */ 149 if (stat(ttyname, &st)) 150 fatal("stat(%.100s) failed: %.100s", ttyname, 151 strerror(errno)); 152 153 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 154 if (chown(ttyname, pw->pw_uid, gid) < 0) { 155 if (errno == EROFS && 156 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 157 debug("chown(%.100s, %u, %u) failed: %.100s", 158 ttyname, (u_int)pw->pw_uid, (u_int)gid, 159 strerror(errno)); 160 else 161 fatal("chown(%.100s, %u, %u) failed: %.100s", 162 ttyname, (u_int)pw->pw_uid, (u_int)gid, 163 strerror(errno)); 164 } 165 } 166 167 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 168 if (chmod(ttyname, mode) < 0) { 169 if (errno == EROFS && 170 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 171 debug("chmod(%.100s, 0%o) failed: %.100s", 172 ttyname, (u_int)mode, strerror(errno)); 173 else 174 fatal("chmod(%.100s, 0%o) failed: %.100s", 175 ttyname, (u_int)mode, strerror(errno)); 176 } 177 } 178 } 179