vtmitm

commit 6e966daedecfa8fd07f6362d842917225031856f
Author: Louis Burda <quent.burda@gmail.com>
Date:   Mon, 20 Feb 2023 01:25:29 +0100

Initial version

Diffstat:
A
.gitignore
 | 
1
+
A
Makefile
 | 
17
+++++++++++++++++
A
README
 | 
4
++++
A
vtmitm.c
 | 
233
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

4 files changed, 255 insertions(+), 0 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1 @@
+vtmitm
diff --git a/Makefile b/Makefile
@@ -0,0 +1,17 @@
+PREFIX ?= /usr/local
+BINDIR ?= /bin
+
+all: vtmitm
+
+clean:
+	rm -f vtmitm
+
+vtmitm: vtmitm.c
+
+install:
+	install -m755 vtmitm -t "$(DESTDIR)$(PREFIX)$(BINDIR)"
+
+uninstall:
+	rm -f "$(DESTDIR)$(PREFIX)$(BINDIR)/vtmitm"
+
+.PHONY: all clean install uninstall
diff --git a/README b/README
@@ -0,0 +1,4 @@
+vtmitm
+======
+
+Stream terminal output by duplicating it as a vtty man-in-the-middle
diff --git a/vtmitm.c b/vtmitm.c
@@ -0,0 +1,233 @@
+#define _XOPEN_SOURCE 600
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/select.h>
+#include <sys/wait.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <termios.h>
+#include <signal.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+struct termios oldterm;
+int master, slave;
+int pipeout;
+pid_t child;
+
+bool encode_resize;
+
+void
+usage(void)
+{
+	fprintf(stderr, "Usage: vtmitm [--encode-resize] -- CMD [ARG]..\n");
+	exit(1);
+}
+
+void
+err(const char *fmtstr, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmtstr);
+	vfprintf(stderr, fmtstr, ap);
+	fprintf(stderr, ": %s\r\n", strerror(errno));
+	va_end(ap);
+
+	exit(1);
+}
+
+int
+writeall(int fd, char *buffer, size_t size)
+{
+	ssize_t nbytes;
+
+	while (size) {
+		nbytes = write(fd, buffer, size);
+		if (nbytes <= 0) return 1;
+		buffer += nbytes;
+		size -= nbytes;
+	}
+
+	return 0;
+}
+
+int
+fwd(int in, int out, int out2)
+{
+	static char buffer[8194];
+	ssize_t got, i, last;
+
+	do {
+		got = read(in, buffer, sizeof(buffer));
+		if (got < 0) return 1;
+
+		if (writeall(out, buffer, got))
+			return 1;
+
+		if (out2 >= 0) {
+			if (writeall(out2, buffer, got))
+				return 1;
+		}
+	} while (got == sizeof(buffer));
+
+	return 0;
+}
+
+void
+mitm(int pts, int pipe)
+{
+	fd_set fds;
+
+	while (1) {
+		FD_ZERO(&fds);
+		FD_SET(0, &fds);
+		FD_SET(pts, &fds);
+
+		if (select(pts + 1, &fds, 0, 0, 0) == -1) {
+			if (errno == EINTR) continue;
+			return;
+		}
+
+		if (FD_ISSET(0, &fds)) { /* stdin -> ptty */
+			if (fwd(0, pts, -1)) return;
+		}
+
+		if (FD_ISSET(pts, &fds)) { /* ptty -> stdout + pipe */
+			if (fwd(pts, 1, pipe)) return;
+		}
+	}
+}
+
+void
+rawterm(struct termios *term)
+{
+	term->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP);
+	term->c_iflag &= ~(INLCR | IGNCR | ICRNL | IXON);
+	term->c_oflag &= ~OPOST;
+	term->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
+	term->c_cflag &= ~(CSIZE | PARENB);
+	term->c_cflag |= CS8;
+}
+
+void
+sigwinch(int sig)
+{
+	char buf[64];
+	struct winsize wsize;
+
+	if (ioctl(0, TIOCGWINSZ, &wsize) != -1)
+		ioctl(slave, TIOCSWINSZ, &wsize);
+	kill(child, SIGWINCH);
+	signal(SIGWINCH, sigwinch);
+
+	/* transmit new size info in form of xterm resize escape sequence */
+	snprintf(buf, sizeof(buf), "\x1b[8;%u;%ut", wsize.ws_row, wsize.ws_col);
+	write(pipeout, buf, sizeof(buf));
+}
+
+void
+sigchld(int sig)
+{
+	int exitcode;
+
+	wait(&exitcode);
+	exit(exitcode);
+}
+
+void
+cleanup(void)
+{
+	tcsetattr(0, TCSANOW, &oldterm);
+}
+
+int
+main(int argc, char *const *argv)
+{
+	struct termios newterm;
+	struct winsize wsize;
+	char *const *arg, *const *cmd;
+	int exitcode;
+
+	cmd = NULL;
+	encode_resize = false;
+	for (arg = argv + 1; *arg; arg++) {
+		if (!strcmp(*arg, "--encode-resize")) {
+			encode_resize = true;
+		} else if (!strcmp(*arg, "--")) {
+			cmd = arg + 1;
+			break;
+		} else {
+			usage();
+		}
+	}
+
+	if (!cmd) usage();
+
+	pipeout = dup(1);
+	if (!freopen("/dev/tty", "w", stdout))
+		err("main: open /dev/tty");
+	dup2(fileno(stdout), 1);
+
+	master = posix_openpt(O_RDWR);
+	if (master == -1) err("main: posix_openpt");
+	if (grantpt(master)) err("main: grantpt");
+	if (unlockpt(master)) err("main: unlockpt");
+
+	slave = open(ptsname(master), O_RDWR);
+	if (slave == -1) err("main: open pts");
+
+	signal(SIGCHLD, sigchld);
+
+	child = fork();
+	if (child < 0) err("main: fork");
+
+	if (child == 0) {
+		close(master);
+
+		signal(SIGCHLD, SIG_DFL);
+
+		if (setsid() == -1)
+			err("slave: setsid");
+
+		if (ioctl(slave, TIOCSCTTY, 0) == -1)
+			err("slave: ioctl TIOCSCTTY");
+
+		if (dup2(slave, 0) == -1)
+			err("slave: dup2 stdin");
+		if (dup2(slave, 1) == -1)
+			err("slave: dup2 stdout");
+		if (dup2(slave, 2) == -1)
+			err("slave: dup2 stderr");
+		close(slave);
+
+		execv(*cmd, cmd + 1);
+		err("slave: execv");
+	} else {
+		if (encode_resize) {
+			signal(SIGWINCH, sigwinch);
+			raise(SIGWINCH);
+		}
+
+		if (tcgetattr(0, &oldterm))
+			err("master: tcgetattr");
+		newterm = oldterm;
+		rawterm(&newterm);
+		if (tcsetattr(0, TCSANOW, &newterm))
+			err("master: tcsetattr");
+		atexit(cleanup);
+
+		mitm(master, pipeout);
+
+		waitpid(child, &exitcode, 0);
+		close(master);
+	}
+
+	return exitcode;
+}