From 5bb432113402889e931ea3e883111e9132d910f5 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 25 Nov 2023 12:18:25 +0100
Subject: [PATCH] libc: Add login_tty() and forkpty()

---
 libc/CMakeLists.txt |  1 +
 libc/include/pty.h  |  3 +++
 libc/include/utmp.h | 18 ++++++++++++++++++
 libc/src/pty.cpp    | 24 ++++++++++++++++++++++++
 libc/src/utmp.cpp   | 22 ++++++++++++++++++++++
 5 files changed, 68 insertions(+)
 create mode 100644 libc/include/utmp.h
 create mode 100644 libc/src/utmp.cpp

diff --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 47d8c8d6..4788422d 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -26,6 +26,7 @@ set(SOURCES
     src/strtod.cpp
     src/math.cpp
     src/pty.cpp
+    src/utmp.cpp
     src/sys/stat.cpp
     src/sys/mman.cpp
     src/sys/wait.cpp
diff --git a/libc/include/pty.h b/libc/include/pty.h
index 22afbb97..1a30d329 100644
--- a/libc/include/pty.h
+++ b/libc/include/pty.h
@@ -14,6 +14,9 @@ extern "C"
     /* Find an available pseudoterminal pair and initialize it, returning file descriptors for both sides. */
     int openpty(int* master, int* slave, char* name, const struct termios* term, const struct winsize* win);
 
+    /* Create a new process operating in a pseudoterminal. */
+    pid_t forkpty(int* master, char* name, const struct termios* term, const struct winsize* win);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libc/include/utmp.h b/libc/include/utmp.h
new file mode 100644
index 00000000..31532265
--- /dev/null
+++ b/libc/include/utmp.h
@@ -0,0 +1,18 @@
+/* utmp.h: Write entries to utmp files. */
+
+#ifndef _UTMP_H
+#define _UTMP_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+    /* Prepare a new terminal session on a tty. */
+    int login_tty(int fd);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/libc/src/pty.cpp b/libc/src/pty.cpp
index 879a772b..c017e8df 100644
--- a/libc/src/pty.cpp
+++ b/libc/src/pty.cpp
@@ -5,6 +5,7 @@
 #include <string.h>
 #include <termios.h>
 #include <unistd.h>
+#include <utmp.h>
 
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 
@@ -44,4 +45,27 @@ extern "C"
 
         return 0;
     }
+
+    pid_t forkpty(int* master, char* name, const struct termios* term, const struct winsize* win)
+    {
+        int slave;
+        if (openpty(master, &slave, name, term, win) < 0) return -1;
+
+        pid_t child = fork();
+        if (child < 0)
+        {
+            close(*master);
+            close(slave);
+            return -1;
+        }
+        if (!child)
+        {
+            close(*master);
+            login_tty(slave);
+        }
+        else
+            close(slave);
+
+        return child;
+    }
 }
diff --git a/libc/src/utmp.cpp b/libc/src/utmp.cpp
new file mode 100644
index 00000000..08b7c6a2
--- /dev/null
+++ b/libc/src/utmp.cpp
@@ -0,0 +1,22 @@
+#include <sys/ioctl.h>
+#include <termios.h>
+#include <unistd.h>
+#include <utmp.h>
+
+extern "C"
+{
+    int login_tty(int fd)
+    {
+        setsid();
+
+        if (ioctl(fd, TIOCSCTTY) < 0) return -1;
+
+        dup2(fd, STDIN_FILENO);
+        dup2(fd, STDOUT_FILENO);
+        dup2(fd, STDERR_FILENO);
+
+        close(fd);
+
+        return 0;
+    }
+}