From 748b7e4aa121a7210fed0d0a29f8e53e91d3fbf9 Mon Sep 17 00:00:00 2001
From: Sebastian Moser <sebastian@c2vi.dev>
Date: Fri, 16 Aug 2024 15:49:38 +0200
Subject: [PATCH] final (hopefully) fixes

---
 scripts/yt-block/main.py         |  6 +++++-
 scripts/yt-block/read-helper.nix |  2 ++
 scripts/yt-block/unkillable.c    | 31 +++++++++++++++++++++----------
 3 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/scripts/yt-block/main.py b/scripts/yt-block/main.py
index 0b36742..92c92b5 100644
--- a/scripts/yt-block/main.py
+++ b/scripts/yt-block/main.py
@@ -275,7 +275,11 @@ def cmd_starter():
     pid = os.getpid()
     print("starter process running with pid", pid)
 
-    os.system(f"$READ_HELPER {pid}")
+    #os.system(f"$READ_HELPER {}", pid)
+    # for some strange reason this does not work
+    with open("/dev/unkillable", "w") as file:
+        file.write(str(pid))
+        #pass
 
     while True:
         print("file:", __file__)
diff --git a/scripts/yt-block/read-helper.nix b/scripts/yt-block/read-helper.nix
index c71bbbf..a380c7a 100644
--- a/scripts/yt-block/read-helper.nix
+++ b/scripts/yt-block/read-helper.nix
@@ -7,6 +7,8 @@ in stdenv.mkDerivation {
   src = ./.;
 
   # Use $CC as it allows for stdenv to reference the correct C compiler
+  # i cant get this to not trigger buffer oferflow protection on the read() call with the pid
+  # so let mod the kernel module, to be able to 'echo $pid > /dev/unkillable'
   buildPhase = ''
     gcc -fno-stack-protector -D_FORTIFY_SOURCE=0 read-helper.c -o read-helper
   '';
diff --git a/scripts/yt-block/unkillable.c b/scripts/yt-block/unkillable.c
index 7a61b64..fd4eee5 100644
--- a/scripts/yt-block/unkillable.c
+++ b/scripts/yt-block/unkillable.c
@@ -25,6 +25,25 @@ struct file_operations unkillable_fops = {
 
 int unkillable_major = 117;
 
+void make_unkillable(int pid) {
+
+  struct pid *pid_struct;
+  struct task_struct *p;
+
+  pr_info("ok ... pid in fn: %d \n", pid);
+
+  /* get the pid struct */
+  pid_struct = find_get_pid((int) pid);
+
+  /* get the task_struct from the pid */
+  p = pid_task(pid_struct, PIDTYPE_PID);
+
+  /* add the flag */
+  p->signal->flags = p->signal->flags | SIGNAL_UNKILLABLE;
+  printk("Unkillable: pid %d marked as unkillable\n", (int) pid);
+}
+
+
 int unkillable_init(void) 
 {
   if (register_chrdev(unkillable_major, "unkillable", &unkillable_fops) < 0 ) {
@@ -54,21 +73,12 @@ int unkillable_release(struct inode *inode, struct file *filp)
 
 ssize_t unkillable_read(struct file *filp, char *buf, size_t count, loff_t *f_pos) 
 { 
-  struct pid *pid_struct;
-  struct task_struct *p;
   
   /* interpret count to read as target pid */
   printk("Unkillable: Got pid %d", (int) count);
 
-  /* get the pid struct */
-  pid_struct = find_get_pid((int) count);
+  make_unkillable(count);
 
-  /* get the task_struct from the pid */
-  p = pid_task(pid_struct, PIDTYPE_PID);
-
-  /* add the flag */
-  p->signal->flags = p->signal->flags | SIGNAL_UNKILLABLE;
-  printk("Unkillable: pid %d marked as unkillable\n", (int) count);
   
   if (*f_pos == 0) { 
     *f_pos+=1; 
@@ -91,6 +101,7 @@ ssize_t unkillable_write(struct file *filp, const char *buf, size_t count, loff_
       return ret;
   } else {
       pr_info("ok ... pid: %llu\n", res);
+      make_unkillable( (int) res);
       return count;
   }
 }