/* Session attach and detach. * * Copyright (c) 2017, Curtis McEnroe * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU Affero General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Affero General Public License for more details. * * You should have received a copy of the GNU Affero General Public License * along with this program. If not, see . */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if defined __FreeBSD__ #include #elif defined __linux__ #include #else #include #endif static struct passwd *getUser(void) { uid_t uid = getuid(); struct passwd *user = getpwuid(uid); if (!user) err(EX_OSFILE, "/etc/passwd"); return user; } static struct sockaddr_un sockAddr(const char *home, const char *name) { struct sockaddr_un addr = { .sun_family = AF_LOCAL }; snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/.dtch/%s", home, name); return addr; } static ssize_t writeAll(int fd, const char *buf, size_t len) { ssize_t writeLen; while (0 < (writeLen = write(fd, buf, len))) { buf += writeLen; len -= writeLen; } return writeLen; } char z; struct iovec iov = { .iov_base = &z, .iov_len = 1 }; static ssize_t sendFd(int sock, int fd) { size_t len = CMSG_LEN(sizeof(int)); char buf[len]; struct msghdr msg = { .msg_iov = &iov, .msg_iovlen = 1, .msg_control = buf, .msg_controllen = len, }; struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); cmsg->cmsg_len = len; cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_RIGHTS; *(int *)CMSG_DATA(cmsg) = fd; return sendmsg(sock, &msg, 0); } static int recvFd(int sock) { size_t len = CMSG_LEN(sizeof(int)); char buf[len]; struct msghdr msg = { .msg_iov = &iov, .msg_iovlen = 1, .msg_control = buf, .msg_controllen = len, }; ssize_t n = recvmsg(sock, &msg, 0); if (n < 0) return -1; struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); if (!cmsg) { errno = ENOMSG; return -1; } if (cmsg->cmsg_type != SCM_RIGHTS) { errno = EBADMSG; return -1; } return *(int *)CMSG_DATA(cmsg); } static struct sockaddr_un addr; static void unlinkAddr(void) { unlink(addr.sun_path); } static int dtch(int argc, char *argv[]) { int error; struct passwd *user = getUser(); char *name = user->pw_name; char *cmd = user->pw_shell; if (argc > 2) { name = argv[1]; cmd = argv[2]; argv += 2; } else if (argc > 1) { name = argv[1]; argv++; } int home = open(user->pw_dir, 0); if (home < 0) err(EX_IOERR, "%s", user->pw_dir); error = mkdirat(home, ".dtch", S_IRWXU); if (error && errno != EEXIST) err(EX_IOERR, "%s/.dtch", user->pw_dir); error = close(home); if (error) err(EX_IOERR, "%s", user->pw_dir); int server = socket(PF_LOCAL, SOCK_STREAM, 0); if (server < 0) err(EX_OSERR, "socket"); addr = sockAddr(user->pw_dir, name); error = bind(server, (struct sockaddr *)&addr, sizeof(addr)); if (error) err(EX_IOERR, "%s", addr.sun_path); atexit(unlinkAddr); error = chmod(addr.sun_path, 0600); if (error) err(EX_IOERR, "%s", addr.sun_path); int master; pid_t pid = forkpty(&master, NULL, NULL, NULL); if (pid < 0) err(EX_OSERR, "forkpty"); if (!pid) { error = close(server); if (error) warn("close(%d)", server); execvp(cmd, argv); err(EX_OSERR, "%s", cmd); } error = listen(server, 0); if (error) err(EX_OSERR, "listen"); for (;;) { int client = accept(server, NULL, NULL); if (client < 0) err(EX_IOERR, "accept(%d)", server); ssize_t len = sendFd(client, master); if (len < 0) warn("sendmsg(%d)", client); len = recv(client, &z, sizeof(z), 0); if (len < 0) warn("recv(%d)", client); error = close(client); if (error) warn("close(%d)", client); pid_t dead = waitpid(pid, NULL, WNOHANG); if (dead < 0) warn("waitpid(%d)", pid); if (dead) exit(EX_OK); } } static struct termios saveTerm; static void restoreTerm(void) { tcsetattr(STDERR_FILENO, TCSADRAIN, &saveTerm); printf( "\x1b[?1049l" // rmcup "\x1b\x63\x1b[!p\x1b[?3;4l\x1b[4l\x1b>" // reset ); } static int atch(int argc, char *argv[]) { int error; struct passwd *user = getUser(); char *name = (argc > 1) ? argv[1] : user->pw_name; int client = socket(PF_LOCAL, SOCK_STREAM, 0); if (client < 0) err(EX_OSERR, "socket"); struct sockaddr_un addr = sockAddr(user->pw_dir, name); error = connect(client, (struct sockaddr *)&addr, sizeof(addr)); if (error) err(EX_IOERR, "%s", addr.sun_path); int master = recvFd(client); if (master < 0) err(EX_IOERR, "recvmsg(%d)", client); struct winsize window; error = ioctl(STDERR_FILENO, TIOCGWINSZ, &window); if (error) err(EX_IOERR, "ioctl(%d, TIOCGWINSZ)", STDERR_FILENO); error = ioctl(master, TIOCSWINSZ, &window); if (error) err(EX_IOERR, "ioctl(%d, TIOCSWINSZ)", master); error = tcgetattr(STDERR_FILENO, &saveTerm); if (error) err(EX_IOERR, "tcgetattr(%d)", STDERR_FILENO); atexit(restoreTerm); struct termios raw; cfmakeraw(&raw); error = tcsetattr(STDERR_FILENO, TCSADRAIN, &raw); if (error) err(EX_IOERR, "tcsetattr(%d)", STDERR_FILENO); char ctrlL = CTRL('L'); ssize_t len = write(master, &ctrlL, 1); if (len < 0) err(EX_IOERR, "write(%d)", master); struct pollfd fds[2] = { { .fd = STDIN_FILENO, .events = POLLIN }, { .fd = master, .events = POLLIN }, }; while (0 < poll(fds, 2, -1)) { char buf[4096]; ssize_t len; if (fds[0].revents) { len = read(STDIN_FILENO, buf, sizeof(buf)); if (len < 0) err(EX_IOERR, "read(%d)", STDIN_FILENO); if (len && buf[0] == CTRL('Q')) exit(EX_OK); len = writeAll(master, buf, len); if (len < 0) err(EX_IOERR, "write(%d)", master); } if (fds[1].revents) { len = read(master, buf, sizeof(buf)); if (len < 0) err(EX_IOERR, "read(%d)", master); len = writeAll(STDOUT_FILENO, buf, len); if (len < 0) err(EX_IOERR, "write(%d)", STDOUT_FILENO); } } err(EX_IOERR, "poll([%d,%d])", STDIN_FILENO, master); } int main(int argc, char *argv[]) { switch (argv[0][0]) { case 'd': return dtch(argc, argv); case 'a': return atch(argc, argv); } return EX_USAGE; }