Move C code to bin, Makefile, AGPL

1 files changed, 262 insertions, 0 deletions

diff --git a/bin/dtch.c b/bin/dtch.c
new file mode 100644
index 00000000..74719fba
--- /dev/null
+++ b/bin/dtch.c
@@ -0,0 +1,262 @@
+/* Session attach and detach.
+ *
+ * Copyright (c) 2017, June McEnroe <programble@gmail.com>
+ *
+ * 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 <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.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 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;
+}