1 files changed, 268 insertions, 0 deletions

diff --git a/bin/dtch.c b/bin/dtch.c
new file mode 100644
index 00000000..059d1a48
--- /dev/null
+++ b/bin/dtch.c
@@ -0,0 +1,268 @@
+/* Copyright (C) 2017, 2018  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 <stdio.h>
+#include <stdlib.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
+
+typedef unsigned char byte;
+
+static struct sockaddr_un sockAddr(const char *home, const char *name) {
+	struct sockaddr_un addr = { .sun_family = AF_UNIX };
+	snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/.dtch/%s", home, name);
+	return addr;
+}
+
+static byte z;
+static struct iovec iov = { .iov_base = &z, .iov_len = 1 };
+
+static ssize_t sendFD(int sock, int fd) {
+	size_t size = CMSG_SPACE(sizeof(int));
+	byte buf[size];
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = buf,
+		.msg_controllen = size,
+	};
+
+	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 size = CMSG_SPACE(sizeof(int));
+	char buf[size];
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = buf,
+		.msg_controllen = size,
+	};
+
+	ssize_t n =  recvmsg(sock, &msg, 0);
+	if (n < 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;
+
+static void sigExit(int sig) {
+	unlink(addr.sun_path);
+	_exit(128 + sig);
+}
+
+static int dtch(int argc, char *argv[]) {
+	int error;
+
+	const char *name = "dtch";
+	if (argc > 1) {
+		name = argv[1];
+		argv++;
+		argc--;
+	}
+	if (argc > 1) {
+		argv++;
+	} else {
+		argv[0] = getenv("SHELL");
+		if (!argv[0]) argv[0] = "/bin/sh";
+	}
+
+	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 server = socket(PF_UNIX, SOCK_STREAM, 0);
+	if (server < 0) err(EX_OSERR, "socket");
+
+	addr = sockAddr(home, name);
+	error = bind(server, (struct sockaddr *)&addr, sizeof(addr));
+	if (error) err(EX_CANTCREAT, "%s", addr.sun_path);
+	fcntl(server, F_SETFD, FD_CLOEXEC);
+
+	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, sigExit);
+	signal(SIGTERM, sigExit);
+
+	error = listen(server, 0);
+	if (error) err(EX_OSERR, "listen");
+
+	for (;;) {
+		int client = accept(server, NULL, NULL);
+		if (client < 0) err(EX_IOERR, "accept");
+
+		ssize_t size = sendFD(client, pty);
+		if (size < 0) warn("sendmsg");
+
+		size = recv(client, &z, sizeof(z), 0);
+		if (size < 0) warn("recv");
+
+		close(client);
+
+		int status;
+		pid_t dead = waitpid(pid, &status, WNOHANG);
+		if (dead < 0) err(EX_OSERR, "waitpid");
+		if (dead) {
+			unlink(addr.sun_path);
+			if (WIFEXITED(status)) return WEXITSTATUS(status);
+			else return 128 + WTERMSIG(status);
+		}
+	}
+}
+
+static struct termios saveTerm;
+static void restoreTerm(void) {
+	tcsetattr(STDIN_FILENO, TCSADRAIN, &saveTerm);
+	printf("\x1B\x63"); // rs1
+}
+
+static void sigNop(int sig) {
+	(void)sig;
+}
+
+static int atch(int argc, char *argv[]) {
+	int error;
+
+	const char *home = getenv("HOME");
+	if (!home) errx(EX_CONFIG, "HOME unset");
+
+	const char *name = (argc > 1) ? argv[1] : "dtch";
+
+	int client = socket(PF_UNIX, SOCK_STREAM, 0);
+	if (client < 0) err(EX_OSERR, "socket");
+
+	struct sockaddr_un addr = sockAddr(home, name);
+	error = connect(client, (struct sockaddr *)&addr, sizeof(addr));
+	if (error) err(EX_NOINPUT, "%s", addr.sun_path);
+
+	int pty = recvFD(client);
+	if (pty < 0) err(EX_IOERR, "recvmsg");
+
+	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, sigNop);
+
+	byte buf[4096];
+	struct pollfd fds[2] = {
+		{ .events = POLLIN, .fd = STDIN_FILENO },
+		{ .events = POLLIN, .fd = pty },
+	};
+	for (;;) {
+		int n = poll(fds, 2, -1);
+		if (n < 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 size = read(STDIN_FILENO, buf, sizeof(buf));
+			if (size < 0) err(EX_IOERR, "read(%d)", STDIN_FILENO);
+
+			if (size == 1 && buf[0] == CTRL('Q')) return EX_OK;
+
+			size = write(pty, buf, size);
+			if (size < 0) err(EX_IOERR, "write(%d)", pty);
+		}
+
+		if (fds[1].revents) {
+			ssize_t size = read(pty, buf, sizeof(buf));
+			if (size < 0) err(EX_IOERR, "read(%d)", pty);
+
+			size = write(STDOUT_FILENO, buf, size);
+			if (size < 0) err(EX_IOERR, "write(%d)", STDOUT_FILENO);
+		}
+	}
+}
+
+int main(int argc, char *argv[]) {
+	switch (argv[0][0]) {
+		case 'd': return dtch(argc, argv);
+		case 'a': return atch(argc, argv);
+		default:  return EX_USAGE;
+	}
+}