1 files changed, 155 insertions, 0 deletions
diff --git a/ptee.c b/ptee.c
new file mode 100644
index 0000000..0c93ab0
--- /dev/null
+++ b/ptee.c
@@ -0,0 +1,155 @@
+/* Copyright (C) 2018  Causal Agent June <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 <poll.h>
+#include <pwd.h>
+#include <stdlib.h>
+#include <sys/ioctl.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
+
+extern int winch(void);
+
+static struct {
+    int pty;
+    int winch;
+    int input;
+    int local;
+    int remote;
+} fd = { -1, -1, STDIN_FILENO, STDERR_FILENO, STDOUT_FILENO };
+
+static struct termios saveTerm;
+static void restoreTerm(void) {
+    tcsetattr(fd.local, TCSADRAIN, &saveTerm);
+}
+
+int main(int argc, char *argv[]) {
+    int error;
+
+    if (isatty(fd.remote)) {
+        errx(EX_USAGE, "stdout is not redirected");
+    }
+
+    if (argc > 1) {
+        argv++;
+    } else {
+        uid_t uid = getuid();
+        struct passwd *user = getpwuid(uid);
+        if (!user) err(EX_OSFILE, "/etc/passwd");
+        argv[0] = user->pw_shell;
+    }
+
+    error = tcgetattr(fd.local, &saveTerm);
+    if (error) err(EX_IOERR, "tcgetattr");
+    atexit(restoreTerm);
+
+    struct termios raw;
+    cfmakeraw(&raw);
+    error = tcsetattr(fd.local, TCSADRAIN, &raw);
+    if (error) err(EX_IOERR, "tcsetattr");
+
+    struct winsize window;
+    error = ioctl(fd.local, TIOCGWINSZ, &window);
+    if (error) err(EX_IOERR, "TIOCGWINSZ");
+    fd.winch = winch();
+
+    pid_t pid = forkpty(&fd.pty, NULL, NULL, &window);
+    if (pid < 0) err(EX_OSERR, "forkpty");
+
+    if (!pid) {
+        execvp(*argv, argv);
+        err(EX_NOINPUT, "%s", *argv);
+    }
+
+    char buf[4096];
+    ssize_t totalSize = 0;
+    struct pollfd fds[3] = {
+        { .fd = fd.input, .events = POLLIN },
+        { .fd = fd.pty, .events = POLLIN },
+        { .fd = fd.winch, .events = POLLIN },
+    };
+    for (;;) {
+        int nfds = poll(fds, 3, -1);
+        if (nfds < 0) {
+            if (errno == EINTR) continue;
+            err(EX_IOERR, "poll");
+        }
+
+        if (fds[0].revents == POLLIN) {
+            ssize_t readSize = read(fd.input, buf, sizeof(buf));
+            if (readSize < 0) err(EX_IOERR, "read(%d)", fd.input);
+
+            ssize_t writeSize = write(fd.pty, buf, readSize);
+            if (writeSize < 0) err(EX_IOERR, "write(%d)", fd.pty);
+            if (writeSize < readSize) errx(EX_IOERR, "short write(%d)", fd.pty);
+        }
+
+        if (fds[1].revents == POLLIN) {
+            ssize_t readSize = read(fd.pty, buf, sizeof(buf));
+            if (readSize < 0) err(EX_IOERR, "read(%d)", fd.pty);
+
+            ssize_t writeSize = write(fd.local, buf, readSize);
+            if (writeSize < 0) err(EX_IOERR, "write(%d)", fd.local);
+            if (writeSize < readSize) err(EX_IOERR, "short write(%d)", fd.local);
+
+            writeSize = write(fd.remote, buf, readSize);
+            if (writeSize < 0) err(EX_IOERR, "write(%d)", fd.remote);
+            if (writeSize < readSize) err(EX_IOERR, "short write(%d)", fd.remote);
+
+            if ((totalSize += readSize) >= 1024 * 1024) {
+                struct winsize original = window;
+                window.ws_row = 1;
+                window.ws_col = 1;
+
+                int error = ioctl(fd.pty, TIOCSWINSZ, &window);
+                if (error) err(EX_IOERR, "TIOCSWINSZ");
+
+                window = original;
+                error = ioctl(fd.pty, TIOCSWINSZ, &window);
+                if (error) err(EX_IOERR, "TIOCWINSZ");
+
+                totalSize = 0;
+            }
+        }
+
+        if (fds[2].revents == POLLIN) {
+            ssize_t readSize = read(fd.winch, &window, sizeof(window));
+            if (readSize < 0) err(EX_IOERR, "read(%d)", fd.winch);
+            if ((size_t)readSize < sizeof(window)) {
+                errx(EX_IOERR, "short read(%d)", fd.winch);
+            }
+
+            int error = ioctl(fd.pty, TIOCSWINSZ, &window);
+            if (error) err(EX_IOERR, "TIOCSWINSZ");
+        }
+
+        int status;
+        pid_t dead = waitpid(pid, &status, WNOHANG);
+        if (dead < 0) err(EX_OSERR, "waitpid(%d)", pid);
+        if (dead) return WIFEXITED(status) ? WEXITSTATUS(status) : EX_SOFTWARE;
+    }
+}