diff --git a/rustdesk-session-permission-pocs/session-downgrade/Cargo.toml b/rustdesk-session-permission-pocs/session-downgrade/Cargo.toml
new file mode 100644
index 0000000..f73eebe
--- /dev/null
+++ b/rustdesk-session-permission-pocs/session-downgrade/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "rustdesk_session_downgrade_poc"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1.0"
+bytes = "1.10"
+hex = "0.4"
+protobuf = { version = "3.7", features = ["with-bytes"] }
+sha2 = "0.10"
+
+[build-dependencies]
+protobuf-codegen = "3.7"
diff --git a/rustdesk-session-permission-pocs/session-downgrade/build.rs b/rustdesk-session-permission-pocs/session-downgrade/build.rs
new file mode 100644
index 0000000..de7e2af
--- /dev/null
+++ b/rustdesk-session-permission-pocs/session-downgrade/build.rs
@@ -0,0 +1,40 @@
+use std::path::PathBuf;
+
+fn main() {
+    let manifest = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR").unwrap());
+    let repo_root = std::env::var("RUSTDESK_REPO_ROOT")
+        .map(PathBuf::from)
+        .ok()
+        .or_else(|| {
+            manifest.ancestors().find_map(|ancestor| {
+                for candidate in [
+                    ancestor.join("rustdesk"),
+                    ancestor.join("work").join("rustdesk"),
+                    ancestor.parent().unwrap_or(ancestor).join("work").join("rustdesk"),
+                ] {
+                    if candidate.join("libs/hbb_common/protos/message.proto").exists() {
+                        return Some(candidate);
+                    }
+                }
+                None
+            })
+        })
+        .expect("set RUSTDESK_REPO_ROOT or place this PoC near a rustdesk checkout")
+        .join("libs")
+        .join("hbb_common")
+        .join("protos");
+    let out_dir = PathBuf::from(std::env::var("OUT_DIR").unwrap()).join("protos");
+    std::fs::create_dir_all(&out_dir).unwrap();
+
+    protobuf_codegen::Codegen::new()
+        .pure()
+        .out_dir(&out_dir)
+        .inputs([
+            repo_root.join("rendezvous.proto"),
+            repo_root.join("message.proto"),
+        ])
+        .include(&repo_root)
+        .customize(protobuf_codegen::Customize::default().tokio_bytes(true))
+        .run()
+        .expect("protobuf codegen failed");
+}