add function to join paths together safely and provide them to lua

1 files changed, 32 insertions, 1 deletions

diff --git a/src/main.rs b/src/main.rs
index 6d89a0d..f3ba157 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,11 @@
 #![allow(dead_code)]
 
-use std::process::ExitCode;
+use std::{
+    ffi::OsString,
+    os::unix::ffi::OsStringExt,
+    path::{Component, Path, PathBuf},
+    process::ExitCode,
+};
 
 use mlua::{Function, Lua, Table};
 
@@ -57,6 +62,9 @@ enum InitLuaError {
     #[error("failed to create variable: {0}")]
     CreateTable(mlua::Error),
 
+    #[error("failed to create helper function: {0}")]
+    Function(mlua::Error),
+
     #[error("failed to set variable {1}: {0}")]
     SetVar(mlua::Error, String),
 
@@ -119,6 +127,17 @@ async fn response(handlers: Table, stream: TcpStream) -> Result<(), ResponseErro
     Ok(())
 }
 
+fn join_path(root: &Path, rest: &Path) -> Result<PathBuf, std::io::Error> {
+    root.components()
+        .chain(
+            rest.components()
+                .filter(|p| !matches!(p, Component::RootDir)),
+        )
+        .filter(|p| !matches!(p, Component::CurDir | Component::ParentDir))
+        .collect::<PathBuf>()
+        .canonicalize()
+}
+
 fn init_lua(lua: Lua) -> Result<(), InitLuaError> {
     let http = lua.create_table().map_err(InitLuaError::CreateTable)?;
 
@@ -126,6 +145,18 @@ fn init_lua(lua: Lua) -> Result<(), InitLuaError> {
         .set("http", http.clone())
         .map_err(|e| InitLuaError::SetVar(e, "http".to_string()))?;
 
+    http.set(
+        "join_paths",
+        lua.create_function(|_, (root, rest): (mlua::String, mlua::String)| {
+            let a = PathBuf::from(OsString::from_vec(root.as_bytes().to_vec()));
+            let b = PathBuf::from(OsString::from_vec(rest.as_bytes().to_vec()));
+
+            join_path(&a, &b).map_err(|e| mlua::Error::runtime(format!("failed to join path: {e}")))
+        })
+        .map_err(InitLuaError::Function)?,
+    )
+    .map_err(|e| InitLuaError::SetVar(e, "http.join_paths".to_string()))?;
+
     let chunk = lua.load(std::fs::read_to_string("config.lua").map_err(InitLuaError::LoadConfig)?);
 
     chunk.eval::<()>().map_err(InitLuaError::EvalConfig)?;