/* * The Qubes OS Project, http://www.qubes-os.org * * Copyright (C) 2010 Rafal Wojtczuk <rafal@invisiblethingslab.com> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2 * 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. * */ #include <sys/socket.h> #include <sys/un.h> #include <stdio.h> #include <getopt.h> #include <stdlib.h> #include <unistd.h> #include <sys/wait.h> #include <errno.h> #include "qrexec.h" #include "libqrexec-utils.h" int connect_unix_socket(const char *domname) { int s, len; struct sockaddr_un remote; if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) { perror("socket"); return -1; } remote.sun_family = AF_UNIX; snprintf(remote.sun_path, sizeof remote.sun_path, QREXEC_DAEMON_SOCKET_DIR "/qrexec.%s", domname); len = strlen(remote.sun_path) + sizeof(remote.sun_family); if (connect(s, (struct sockaddr *) &remote, len) == -1) { perror("connect"); exit(1); } return s; } void do_exec(const char *prog) { execl("/bin/bash", "bash", "-c", prog, NULL); } static int local_stdin_fd, local_stdout_fd; void do_exit(int code) { int status; // sever communication lines; wait for child, if any // so that qrexec-daemon can count (recursively) spawned processes correctly close(local_stdin_fd); close(local_stdout_fd); waitpid(-1, &status, 0); exit(code); } void prepare_local_fds(const char *cmdline) { int pid; if (!cmdline) { local_stdin_fd = 1; local_stdout_fd = 0; return; } do_fork_exec(cmdline, &pid, &local_stdin_fd, &local_stdout_fd, NULL); } void send_cmdline(int s, int type, const char *cmdline) { struct client_header hdr; hdr.type = type; hdr.len = strlen(cmdline) + 1; if (!write_all(s, &hdr, sizeof(hdr)) || !write_all(s, cmdline, hdr.len)) { perror("write daemon"); do_exit(1); } } void handle_input(int s) { char buf[MAX_DATA_CHUNK]; int ret; ret = read(local_stdout_fd, buf, sizeof(buf)); if (ret < 0) { perror("read"); do_exit(1); } if (ret == 0) { close(local_stdout_fd); local_stdout_fd = -1; shutdown(s, SHUT_WR); if (local_stdin_fd == -1) { // if pipe in opposite direction already closed, no need to stay alive do_exit(0); } } if (!write_all(s, buf, ret)) { if (errno == EPIPE) { // daemon disconnected its end of socket, so no future data will be // send there; there is no sense to read from child stdout // // since AF_UNIX socket is buffered it doesn't mean all data was // received from the agent close(local_stdout_fd); local_stdout_fd = -1; if (local_stdin_fd == -1) { // since child does no longer accept data on its stdin, doesn't // make sense to process the data from the daemon // // we don't know real exit VM process code (exiting here, before // MSG_SERVER_TO_CLIENT_EXIT_CODE message) do_exit(1); } } else perror("write daemon"); } } void handle_daemon_data(int s) { int status; struct client_header hdr; char buf[MAX_DATA_CHUNK]; if (!read_all(s, &hdr, sizeof hdr)) { perror("read daemon"); do_exit(1); } if (hdr.len > MAX_DATA_CHUNK) { fprintf(stderr, "client_header.len=%d\n", hdr.len); do_exit(1); } if (!read_all(s, buf, hdr.len)) { perror("read daemon"); do_exit(1); } switch (hdr.type) { case MSG_SERVER_TO_CLIENT_STDOUT: if (local_stdin_fd == -1) break; if (hdr.len == 0) { close(local_stdin_fd); local_stdin_fd = -1; } else if (!write_all(local_stdin_fd, buf, hdr.len)) { if (errno == EPIPE) { // remote side have closed its stdin, handle data in oposite // direction (if any) before exit local_stdin_fd = -1; } else { perror("write local stdout"); do_exit(1); } } break; case MSG_SERVER_TO_CLIENT_STDERR: write_all(2, buf, hdr.len); break; case MSG_SERVER_TO_CLIENT_EXIT_CODE: status = *(unsigned int *) buf; if (WIFEXITED(status)) do_exit(WEXITSTATUS(status)); else do_exit(255); break; default: fprintf(stderr, "unknown msg %d\n", hdr.type); do_exit(1); } } // perhaps we could save a syscall if we include both sides in both // rdset and wrset; to be investigated void handle_daemon_only_until_writable(int s) { fd_set rdset, wrset; do { FD_ZERO(&rdset); FD_ZERO(&wrset); FD_SET(s, &rdset); FD_SET(s, &wrset); if (select(s + 1, &rdset, &wrset, NULL, NULL) < 0) { perror("select"); do_exit(1); } if (FD_ISSET(s, &rdset)) handle_daemon_data(s); } while (!FD_ISSET(s, &wrset)); } void select_loop(int s) { fd_set select_set; int max; for (;;) { handle_daemon_only_until_writable(s); FD_ZERO(&select_set); FD_SET(s, &select_set); max = s; if (local_stdout_fd != -1) { FD_SET(local_stdout_fd, &select_set); if (s < local_stdout_fd) max = local_stdout_fd; } if (select(max + 1, &select_set, NULL, NULL, NULL) < 0) { perror("select"); do_exit(1); } if (FD_ISSET(s, &select_set)) handle_daemon_data(s); if (local_stdout_fd != -1 && FD_ISSET(local_stdout_fd, &select_set)) handle_input(s); } } void usage(const char *name) { fprintf(stderr, "usage: %s -d domain_num [-l local_prog] -e -c remote_cmdline\n" "-e means exit after sending cmd, -c: connect to existing process\n", name); exit(1); } int main(int argc, char **argv) { int opt; char *domname = NULL; int s; int just_exec = 0; int connect_existing = 0; char *local_cmdline = NULL; while ((opt = getopt(argc, argv, "d:l:ec")) != -1) { switch (opt) { case 'd': domname = strdup(optarg); break; case 'l': local_cmdline = strdup(optarg); break; case 'e': just_exec = 1; break; case 'c': connect_existing = 1; break; default: usage(argv[0]); } } if (optind >= argc || !domname) usage(argv[0]); s = connect_unix_socket(domname); setenv("QREXEC_REMOTE_DOMAIN", domname, 1); prepare_local_fds(local_cmdline); if (just_exec) send_cmdline(s, MSG_CLIENT_TO_SERVER_JUST_EXEC, argv[optind]); else { int cmd; if (connect_existing) cmd = MSG_CLIENT_TO_SERVER_CONNECT_EXISTING; else cmd = MSG_CLIENT_TO_SERVER_EXEC_CMDLINE; send_cmdline(s, cmd, argv[optind]); select_loop(s); } return 0; }