diff options
Diffstat (limited to 'bin/dtch.c')
| -rw-r--r-- | bin/dtch.c | 271 |
1 files changed, 271 insertions, 0 deletions
diff --git a/bin/dtch.c b/bin/dtch.c new file mode 100644 index 00000000..2aea53ae --- /dev/null +++ b/bin/dtch.c @@ -0,0 +1,271 @@ +/* Copyright (C) 2017-2019 C. McEnroe <june@causal.agency> + * + * 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 <http://www.gnu.org/licenses/>. + */ + +#include <err.h> +#include <errno.h> +#include <fcntl.h> +#include <poll.h> +#include <signal.h> +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/ioctl.h> +#include <sys/socket.h> +#include <sys/stat.h> +#include <sys/un.h> +#include <sys/wait.h> +#include <sysexits.h> +#include <termios.h> +#include <unistd.h> + +#if defined __FreeBSD__ +#include <libutil.h> +#elif defined __linux__ +#include <pty.h> +#else +#include <util.h> +#endif + +static char _; +static struct iovec iov = { .iov_base = &_, .iov_len = 1 }; + +static ssize_t sendfd(int sock, int fd) { + size_t len = CMSG_SPACE(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 = CMSG_LEN(sizeof(int)); + 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_SPACE(sizeof(int)); + char buf[len]; + struct msghdr msg = { + .msg_iov = &iov, + .msg_iovlen = 1, + .msg_control = buf, + .msg_controllen = len, + }; + if (0 > recvmsg(sock, &msg, 0)) return -1; + + struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); + if (!cmsg || cmsg->cmsg_type != SCM_RIGHTS) { + errno = ENOMSG; + return -1; + } + return *(int *)CMSG_DATA(cmsg); +} + +static struct sockaddr_un addr = { .sun_family = AF_UNIX }; + +static void handler(int sig) { + unlink(addr.sun_path); + _exit(-sig); +} + +static void detach(int server, bool sink, char *argv[]) { + int pty; + pid_t pid = forkpty(&pty, NULL, NULL, NULL); + if (pid < 0) err(EX_OSERR, "forkpty"); + + if (!pid) { + execvp(argv[0], argv); + err(EX_NOINPUT, "%s", argv[0]); + } + + signal(SIGINT, handler); + signal(SIGTERM, handler); + + int error = listen(server, 0); + if (error) err(EX_OSERR, "listen"); + + struct pollfd fds[] = { + { .events = POLLIN, .fd = server }, + { .events = POLLIN, .fd = pty }, + }; + while (0 < poll(fds, (sink ? 2 : 1), -1)) { + if (fds[0].revents) { + int client = accept(server, NULL, NULL); + if (client < 0) err(EX_IOERR, "accept"); + + ssize_t len = sendfd(client, pty); + if (len < 0) warn("sendfd"); + + len = recv(client, &_, sizeof(_), 0); + if (len < 0) warn("recv"); + + close(client); + } + + if (fds[1].revents) { + char buf[4096]; + ssize_t len = read(pty, buf, sizeof(buf)); + if (len < 0) err(EX_IOERR, "read"); + } + + int status; + pid_t dead = waitpid(pid, &status, WNOHANG); + if (dead < 0) err(EX_OSERR, "waitpid"); + if (dead) { + unlink(addr.sun_path); + exit(WIFEXITED(status) ? WEXITSTATUS(status) : -WTERMSIG(status)); + } + } + err(EX_IOERR, "poll"); +} + +static struct termios saveTerm; +static void restoreTerm(void) { + tcsetattr(STDIN_FILENO, TCSADRAIN, &saveTerm); + fprintf(stderr, "\33c"); // RIS + warnx("detached"); +} + +static void nop(int sig) { + (void)sig; +} + +static void attach(int client) { + int error; + + int pty = recvfd(client); + if (pty < 0) err(EX_IOERR, "recvfd"); + warnx("attached"); + + struct winsize window; + error = ioctl(STDIN_FILENO, TIOCGWINSZ, &window); + if (error) err(EX_IOERR, "ioctl"); + + struct winsize redraw = { .ws_row = 1, .ws_col = 1 }; + error = ioctl(pty, TIOCSWINSZ, &redraw); + if (error) err(EX_IOERR, "ioctl"); + + error = ioctl(pty, TIOCSWINSZ, &window); + if (error) err(EX_IOERR, "ioctl"); + + error = tcgetattr(STDIN_FILENO, &saveTerm); + if (error) err(EX_IOERR, "tcgetattr"); + atexit(restoreTerm); + + struct termios raw = saveTerm; + cfmakeraw(&raw); + error = tcsetattr(STDIN_FILENO, TCSADRAIN, &raw); + if (error) err(EX_IOERR, "tcsetattr"); + + signal(SIGWINCH, nop); + + char buf[4096]; + struct pollfd fds[] = { + { .events = POLLIN, .fd = STDIN_FILENO }, + { .events = POLLIN, .fd = pty }, + }; + for (;;) { + int nfds = poll(fds, 2, -1); + if (nfds < 0) { + if (errno != EINTR) err(EX_IOERR, "poll"); + + error = ioctl(STDIN_FILENO, TIOCGWINSZ, &window); + if (error) err(EX_IOERR, "ioctl"); + + error = ioctl(pty, TIOCSWINSZ, &window); + if (error) err(EX_IOERR, "ioctl"); + + continue; + } + + if (fds[0].revents) { + ssize_t len = read(STDIN_FILENO, buf, sizeof(buf)); + if (len < 0) err(EX_IOERR, "read"); + if (!len) break; + + if (len == 1 && buf[0] == CTRL('Q')) break; + + len = write(pty, buf, len); + if (len < 0) err(EX_IOERR, "write"); + } + + if (fds[1].revents) { + ssize_t len = read(pty, buf, sizeof(buf)); + if (len < 0) err(EX_IOERR, "read"); + if (!len) break; + + len = write(STDOUT_FILENO, buf, len); + if (len < 0) err(EX_IOERR, "write"); + } + } +} + +int main(int argc, char *argv[]) { + int error; + + bool atch = false; + bool sink = false; + + int opt; + while (0 < (opt = getopt(argc, argv, "as"))) { + switch (opt) { + break; case 'a': atch = true; + break; case 's': sink = true; + break; default: return EX_USAGE; + } + } + if (optind == argc) errx(EX_USAGE, "no session name"); + const char *name = argv[optind++]; + + if (optind == argc) { + argv[--optind] = getenv("SHELL"); + if (!argv[optind]) errx(EX_CONFIG, "SHELL unset"); + } + + const char *home = getenv("HOME"); + if (!home) errx(EX_CONFIG, "HOME unset"); + + int fd = open(home, 0); + if (fd < 0) err(EX_CANTCREAT, "%s", home); + + error = mkdirat(fd, ".dtch", 0700); + if (error && errno != EEXIST) err(EX_CANTCREAT, "%s/.dtch", home); + + close(fd); + + int sock = socket(PF_UNIX, SOCK_STREAM, 0); + if (sock < 0) err(EX_OSERR, "socket"); + fcntl(sock, F_SETFD, FD_CLOEXEC); + + snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/.dtch/%s", home, name); + + if (atch) { + error = connect(sock, (struct sockaddr *)&addr, SUN_LEN(&addr)); + if (error) err(EX_NOINPUT, "%s", addr.sun_path); + attach(sock); + } else { + error = bind(sock, (struct sockaddr *)&addr, SUN_LEN(&addr)); + if (error) err(EX_CANTCREAT, "%s", addr.sun_path); + detach(sock, sink, &argv[optind]); + } +} |