1/* $NetBSD: sshpty.c,v 1.8 2019/10/12 18:32:22 christos Exp $ */ 2/* $OpenBSD: sshpty.c,v 1.34 2019/07/04 16:20:10 deraadt Exp $ */ 3/* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * Allocating a pseudo-terminal, and making it the controlling tty. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 */ 15 16#include "includes.h" 17__RCSID("$NetBSD: sshpty.c,v 1.8 2019/10/12 18:32:22 christos Exp $"); 18#include <sys/types.h> 19#include <sys/ioctl.h> 20#include <sys/stat.h> 21 22#include <errno.h> 23#include <fcntl.h> 24#include <grp.h> 25#include <paths.h> 26#include <pwd.h> 27#include <stdarg.h> 28#include <string.h> 29#include <termios.h> 30#include <unistd.h> 31#include <util.h> 32 33#include "sshpty.h" 34#include "log.h" 35 36#ifndef O_NOCTTY 37#define O_NOCTTY 0 38#endif 39 40/* 41 * Allocates and opens a pty. Returns 0 if no pty could be allocated, or 42 * nonzero if a pty was successfully allocated. On success, open file 43 * descriptors for the pty and tty sides and the name of the tty side are 44 * returned (the buffer must be able to hold at least 64 characters). 45 */ 46 47int 48pty_allocate(int *ptyfd, int *ttyfd, char *namebuf, size_t namebuflen) 49{ 50 char buf[64]; 51 int i; 52 53 i = openpty(ptyfd, ttyfd, buf, NULL, NULL); 54 if (i == -1) { 55 error("openpty: %.100s", strerror(errno)); 56 return 0; 57 } 58 strlcpy(namebuf, buf, namebuflen); /* possible truncation */ 59 return 1; 60} 61 62/* Releases the tty. Its ownership is returned to root, and permissions to 0666. */ 63 64void 65pty_release(const char *tty) 66{ 67 if (chown(tty, (uid_t) 0, (gid_t) 0) == -1) 68 error("chown %.100s 0 0 failed: %.100s", tty, strerror(errno)); 69 if (chmod(tty, (mode_t) 0666) == -1) 70 error("chmod %.100s 0666 failed: %.100s", tty, strerror(errno)); 71} 72 73/* Makes the tty the process's controlling tty and sets it to sane modes. */ 74 75void 76pty_make_controlling_tty(int *ttyfd, const char *tty) 77{ 78 int fd; 79 80 /* First disconnect from the old controlling tty. */ 81#ifdef TIOCNOTTY 82 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 83 if (fd >= 0) { 84 (void) ioctl(fd, TIOCNOTTY, NULL); 85 close(fd); 86 } 87#endif /* TIOCNOTTY */ 88 if (setsid() == -1) 89 error("setsid: %.100s", strerror(errno)); 90 91 /* 92 * Verify that we are successfully disconnected from the controlling 93 * tty. 94 */ 95 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 96 if (fd >= 0) { 97 error("Failed to disconnect from controlling tty."); 98 close(fd); 99 } 100 /* Make it our controlling tty. */ 101#ifdef TIOCSCTTY 102 debug("Setting controlling tty using TIOCSCTTY."); 103 if (ioctl(*ttyfd, TIOCSCTTY, NULL) == -1) 104 error("ioctl(TIOCSCTTY): %.100s", strerror(errno)); 105#endif /* TIOCSCTTY */ 106 fd = open(tty, O_RDWR); 107 if (fd == -1) 108 error("%.100s: %.100s", tty, strerror(errno)); 109 else 110 close(fd); 111 112 /* Verify that we now have a controlling tty. */ 113 fd = open(_PATH_TTY, O_WRONLY); 114 if (fd == -1) 115 error("open /dev/tty failed - could not set controlling tty: %.100s", 116 strerror(errno)); 117 else 118 close(fd); 119} 120 121/* Changes the window size associated with the pty. */ 122 123void 124pty_change_window_size(int ptyfd, u_int row, u_int col, 125 u_int xpixel, u_int ypixel) 126{ 127 struct winsize w; 128 129 /* may truncate u_int -> u_short */ 130 w.ws_row = row; 131 w.ws_col = col; 132 w.ws_xpixel = xpixel; 133 w.ws_ypixel = ypixel; 134 (void) ioctl(ptyfd, TIOCSWINSZ, &w); 135} 136 137void 138pty_setowner(struct passwd *pw, const char *tty) 139{ 140 struct group *grp; 141 gid_t gid; 142 mode_t mode; 143 struct stat st; 144 145 /* Determine the group to make the owner of the tty. */ 146 grp = getgrnam("tty"); 147 if (grp == NULL) 148 fatal("no tty group"); 149 gid = (grp != NULL) ? grp->gr_gid : pw->pw_gid; 150 mode = (grp != NULL) ? 0620 : 0600; 151 152 /* 153 * Change owner and mode of the tty as required. 154 * Warn but continue if filesystem is read-only and the uids match/ 155 * tty is owned by root. 156 */ 157 if (stat(tty, &st) == -1) 158 fatal("stat(%.100s) failed: %.100s", tty, 159 strerror(errno)); 160 161 if (st.st_uid != pw->pw_uid || st.st_gid != gid) { 162 if (chown(tty, pw->pw_uid, gid) == -1) { 163 if (errno == EROFS && 164 (st.st_uid == pw->pw_uid || st.st_uid == 0)) 165 debug("chown(%.100s, %u, %u) failed: %.100s", 166 tty, (u_int)pw->pw_uid, (u_int)gid, 167 strerror(errno)); 168 else 169 fatal("chown(%.100s, %u, %u) failed: %.100s", 170 tty, (u_int)pw->pw_uid, (u_int)gid, 171 strerror(errno)); 172 } 173 } 174 175 if ((st.st_mode & (S_IRWXU|S_IRWXG|S_IRWXO)) != mode) { 176 if (chmod(tty, mode) == -1) { 177 if (errno == EROFS && 178 (st.st_mode & (S_IRGRP | S_IROTH)) == 0) 179 debug("chmod(%.100s, 0%o) failed: %.100s", 180 tty, (u_int)mode, strerror(errno)); 181 else 182 fatal("chmod(%.100s, 0%o) failed: %.100s", 183 tty, (u_int)mode, strerror(errno)); 184 } 185 } 186} 187 188/* Disconnect from the controlling tty. */ 189void 190disconnect_controlling_tty(void) 191{ 192 int fd; 193 194 if ((fd = open(_PATH_TTY, O_RDWR | O_NOCTTY)) >= 0) { 195 (void) ioctl(fd, TIOCNOTTY, NULL); 196 close(fd); 197 } 198} 199