1 /* $NetBSD: sshpty.c,v 1.9 2026/04/08 18:58:41 christos Exp $ */ 2 /* $OpenBSD: sshpty.c,v 1.35 2026/02/11 17:05:32 dtucker Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo (at) 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 1.9 2026/04/08 18:58:41 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 <signal.h> 29 #include <stdarg.h> 30 #include <stdio.h> 31 #include <string.h> 32 #include <termios.h> 33 #include <unistd.h> 34 #include <util.h> 35 36 #include "sshpty.h" 37 #include "log.h" 38 39 #ifndef O_NOCTTY 40 #define O_NOCTTY 0 41 #endif 42 43 /* 44 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 45 * nonzero if a pty was successfully allocated. On success, open file 46 * descriptors for the pty and tty sides and the name of the tty side are 47 * returned (the buffer must be able to hold at least 64 characters). 48 */ 49 50 int 51 pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen) 52 { 53 char buf[64]; 54 int i; 55 56 i = openpty(ptyfd, ttyfd, buf, NULL, NULL); 57 if (i == -1) { 58 error("openpty: %.100s", strerror(errno)); 59 return 0; 60 } 61 strlcpy(namebuf, buf, namebuflen); /* possible truncation */ 62 return 1; 63 } 64 65 /* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 66 67 void 68 pty_release(const char *tty) 69 { 70 if (chown(tty, (uid_t) 0, (gid_t) 0) == -1) 71 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 72 if (chmod(tty, (mode_t) 0666) == -1) 73 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 74 } 75 76 /* Makes the tty the process's controlling tty and sets it to sane modes. */ 77 78 void 79 pty_make_controlling_tty(int *ttyfd, const char *tty) 80 { 81 int fd; 82 83 /* First disconnect from the old controlling tty. */ 84 #ifdef TIOCNOTTY 85 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 86 if (fd >= 0) { 87 (void) ioctl(fd, TIOCNOTTY, NULL); 88 close(fd); 89 } 90 #endif /* TIOCNOTTY */ 91 if (setsid() == -1) 92 error("setsid: %.100s", strerror(errno)); 93 94 /* 95 * Verify that we are successfully disconnected from the controlling 96 * tty. 97 */ 98 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 99 if (fd >= 0) { 100 error("Failed to disconnect from controlling tty."); 101 close(fd); 102 } 103 /* Make it our controlling tty. */ 104 #ifdef TIOCSCTTY 105 debug("Setting controlling tty using TIOCSCTTY."); 106 if (ioctl(*ttyfd, TIOCSCTTY, NULL) == -1) 107 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 108 #endif /* TIOCSCTTY */ 109 fd = open(tty, O_RDWR); 110 if (fd == -1) 111 error("%.100s: %.100s", tty, strerror(errno)); 112 else 113 close(fd); 114 115 /* Verify that we now have a controlling tty. */ 116 fd = open(_PATH_TTY, O_WRONLY); 117 if (fd == -1) 118 error("open /dev/tty failed - could not set controlling tty: %.100s", 119 strerror(errno)); 120 else 121 close(fd); 122 } 123 124 /* Changes the window size associated with the pty. */ 125 126 void 127 pty_change_window_size(int ptyfd, u_int row, u_int col, 128 u_int xpixel, u_int ypixel) 129 { 130 struct winsize w; 131 132 /* may truncate u_int -> u_short */ 133 w.ws_row = row; 134 w.ws_col = col; 135 w.ws_xpixel = xpixel; 136 w.ws_ypixel = ypixel; 137 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 138 } 139 140 void 141 pty_setowner(struct passwd *pw, const char *tty) 142 { 143 struct group *grp; 144 gid_t gid; 145 mode_t mode; 146 struct stat st; 147 148 /* Determine the group to make the owner of the tty. */ 149 grp = getgrnam("tty"); 150 if (grp == NULL) 151 fatal("no tty group"); 152 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 153 mode = (grp != NULL) ? 0620 : 0600; 154 155 /* 156 * Change owner and mode of the tty as required. 157 * Warn but continue if filesystem is read-only and the uids match/ 158 * tty is owned by root. 159 */ 160 if (stat(tty, &st) == -1) 161 fatal("stat(%.100s) failed: %.100s", tty, 162 strerror(errno)); 163 164 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 165 if (chown(tty, pw->pw_uid, gid) == -1) { 166 if (errno == EROFS && 167 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 168 debug("chown(%.100s, %u, %u) failed: %.100s", 169 tty, (u_int)pw->pw_uid, (u_int)gid, 170 strerror(errno)); 171 else 172 fatal("chown(%.100s, %u, %u) failed: %.100s", 173 tty, (u_int)pw->pw_uid, (u_int)gid, 174 strerror(errno)); 175 } 176 } 177 178 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 179 if (chmod(tty, mode) == -1) { 180 if (errno == EROFS && 181 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 182 debug("chmod(%.100s, 0%o) failed: %.100s", 183 tty, (u_int)mode, strerror(errno)); 184 else 185 fatal("chmod(%.100s, 0%o) failed: %.100s", 186 tty, (u_int)mode, strerror(errno)); 187 } 188 } 189 } 190 191 /* Disconnect from the controlling tty. */ 192 void 193 disconnect_controlling_tty(void) 194 { 195 int fd; 196 197 if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) { 198 (void) ioctl(fd, TIOCNOTTY, NULL); 199 close(fd); 200 } 201 } 202
Indexes created Sun Jun 21 00:25:28 UTC 2026