From f77fae1335c562b720c4a6d4aa710f8627eaaff6 Mon Sep 17 00:00:00 2001 From: Curtis McEnroe Date: Wed, 6 Sep 2017 14:01:48 -0400 Subject: Move C code to bin, Makefile, AGPL --- bin/dtch.c | 262 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 262 insertions(+) create mode 100644 bin/dtch.c (limited to 'bin/dtch.c') diff --git a/bin/dtch.c b/bin/dtch.c new file mode 100644 index 00000000..9be88a12 --- /dev/null +++ b/bin/dtch.c @@ -0,0 +1,262 @@ +/* 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; +} -- cgit 1.4.1