Implement preopened_dir using set_mapped_directory setting

ext/src/ruby_api/wasi_config.rs

@@ -3,14 +3,17 @@ use crate::error;
 use crate::helpers::OutputLimitedBuffer;
 use magnus::{
     class, function, gc::Marker, method, typed_data::Obj, value::Opaque, DataTypeFunctions, Error,
-    Module, Object, RArray, RHash, RString, Ruby, TryConvert, TypedData,
+    Module, Object, RArray, RHash, RString, Ruby, Symbol, TryConvert, TypedData,
 };
+use rb_sys::ruby_rarray_flags::RARRAY_EMBED_FLAG;
 use std::cell::RefCell;
 use std::fs;
+use std::path::Path;
 use std::{fs::File, path::PathBuf};
 use wasmtime_wasi::p2::pipe::MemoryInputPipe;
 use wasmtime_wasi::p2::{OutputFile, WasiCtx, WasiCtxBuilder};
 use wasmtime_wasi::preview1::WasiP1Ctx;
+use wasmtime_wasi::{DirPerms, FilePerms};
 
 enum ReadStream {
     Inherit,
@@ -51,6 +54,7 @@ struct WasiConfigInner {
     env: Option<Opaque<RHash>>,
     args: Option<Opaque<RArray>>,
     deterministic: bool,
+    mapped_directories: Option<Opaque<RArray>>,
 }
 
 impl WasiConfigInner {
@@ -70,6 +74,9 @@ impl WasiConfigInner {
         if let Some(v) = self.args.as_ref() {
             marker.mark(*v);
         }
+        if let Some(v) = self.mapped_directories.as_ref() {
+            marker.mark(*v);
+        }
     }
 }
 
@@ -233,6 +240,40 @@ impl WasiConfig {
         rb_self
     }
 
+    /// @yard
+    /// Set mapped directory for host path and guest path.
+    /// @param host_path [String]
+    /// @param guest_path [String]
+    /// @param dir_perms [Symbol] Directory permissions, one of :read, :mutate, or :all
+    /// @param file_perms [Symbol] File permissions, one of :read, :write, or :all
+    /// @def set_mapped_directory(host_path, guest_path, dir_perms, file_perms)
+    /// @return [WasiConfig] +self+
+    pub fn set_mapped_directory(
+        rb_self: RbSelf,
+        host_path: RString,
+        guest_path: RString,
+        dir_perms: Symbol,
+        file_perms: Symbol,
+    ) -> RbSelf {
+        let mapped_directory = RArray::new();
+        mapped_directory.push(host_path).unwrap();
+        mapped_directory.push(guest_path).unwrap();
+        mapped_directory.push(dir_perms).unwrap();
+        mapped_directory.push(file_perms).unwrap();
+
+        let init_directory = RArray::new();
+
+        let mut inner = rb_self.inner.borrow_mut();
+        if inner.mapped_directories.is_none() {
+            inner.mapped_directories = Some(init_directory.into());
+        }
+
+        let ruby = Ruby::get().unwrap();
+        let mapped_directories = ruby.get_inner(inner.mapped_directories.unwrap());
+        mapped_directories.push(mapped_directory).unwrap();
+        rb_self
+    }
+
     pub fn build_p1(&self, ruby: &Ruby) -> Result<WasiP1Ctx, Error> {
         let mut builder = self.build_impl(ruby)?;
         let ctx = builder.build_p1();
@@ -317,6 +358,63 @@ impl WasiConfig {
             deterministic_wasi_ctx::add_determinism_to_wasi_ctx_builder(&mut builder);
         }
 
+        if let Some(mapped_directories) = inner.mapped_directories.as_ref() {
+            for item in unsafe { ruby.get_inner(*mapped_directories).as_slice() } {
+                let mapped_directory = RArray::try_convert(*item)?;
+                if mapped_directory.len() == 4 {
+                    let host_path =
+                        RString::try_convert(mapped_directory.entry(0)?)?.to_string()?;
+                    let guest_path =
+                        RString::try_convert(mapped_directory.entry(1)?)?.to_string()?;
+                    let dir_perms = Symbol::from_value(mapped_directory.entry(2)?)
+                        .unwrap()
+                        .name()?;
+                    let file_perms = Symbol::from_value(mapped_directory.entry(3)?)
+                        .unwrap()
+                        .name()?;
+
+                    let host_path_dir = Path::new(&host_path);
+                    let guest_path_path = guest_path.as_str();
+
+                    // Convert to FilePerms and DirPerms enums
+                    let dir_perms_flags;
+                    match dir_perms {
+                        std::borrow::Cow::Borrowed("read") => dir_perms_flags = DirPerms::READ,
+                        std::borrow::Cow::Borrowed("mutate") => dir_perms_flags = DirPerms::MUTATE,
+                        std::borrow::Cow::Borrowed("all") => dir_perms_flags = DirPerms::all(),
+                        _ => {
+                            return Err(error!(
+                                "Invalid dir_perms: {}. Use one of :read, :mutate, or :all",
+                                dir_perms
+                            ))
+                        }
+                    }
+
+                    let file_perms_flags;
+                    match file_perms {
+                        std::borrow::Cow::Borrowed("read") => file_perms_flags = FilePerms::READ,
+                        std::borrow::Cow::Borrowed("write") => file_perms_flags = FilePerms::WRITE,
+                        std::borrow::Cow::Borrowed("all") => file_perms_flags = FilePerms::all(),
+                        _ => {
+                            return Err(error!(
+                                "Invalid file_perms: {}. Use one of :read, :write, or :all",
+                                file_perms
+                            ))
+                        }
+                    }
+
+                    builder
+                        .preopened_dir(
+                            host_path_dir,
+                            guest_path_path,
+                            dir_perms_flags,
+                            file_perms_flags,
+                        )
+                        .map_err(|e| error!("{}", e))?;
+                }
+            }
+        }
+
         Ok(builder)
     }
 }
@@ -355,5 +453,10 @@ pub fn init() -> Result<(), Error> {
 
     class.define_method("set_argv", method!(WasiConfig::set_argv, 1))?;
 
+    class.define_method(
+        "set_mapped_directory",
+        method!(WasiConfig::set_mapped_directory, 4),
+    )?;
+
     Ok(())
 }

spec/fixtures/wasi-fs/.cargo/config.toml

@@ -0,0 +1,2 @@
+[build]
+target = "wasm32-wasip1"

spec/fixtures/wasi-fs/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "wasi-fs"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[workspace]
+
+[dependencies]

spec/fixtures/wasi-fs/README.md

@@ -0,0 +1,14 @@
+Example WASI program used to test WASI preopened directories
+
+To update:
+
+```shell
+cargo build --release && \
+    wasm-opt -O \
+    --enable-bulk-memory \
+    target/wasm32-wasip1/release/wasi-fs.wasm \
+    -o ../wasi-fs.wasm && \
+cargo build --target=wasm32-wasip2 --release && \
+    cp target/wasm32-wasip2/release/wasi-fs.wasm \
+    ../wasi-fs-p2.wasm
+```

spec/fixtures/wasi-fs/src/main.rs

@@ -0,0 +1,18 @@
+use std::io::{Write, Read};
+use std::fs::File;
+
+fn main() {
+    let args: Vec<String> = std::env::args().collect();
+
+    let counter_file = File::open(&args[1]).expect("failed to open counter file");
+
+    let mut counter_str = String::new();
+    counter_file.take(100).read_to_string(&mut counter_str)
+        .expect("failed to read counter file");
+    let mut counter: u32 = counter_str.trim().parse().expect("failed to parse counter");
+
+    counter += 1;
+
+    let mut counter_file = File::create(&args[1]).expect("failed to create counter file");
+    write!(counter_file, "{}", counter).expect("failed to write counter file");
+}

spec/unit/wasi_spec.rb

@@ -12,9 +12,11 @@ module Wasmtime
       # Compile module only once for speed
       @compiled_wasi_module = @engine.precompile_module(IO.binread("spec/fixtures/wasi-debug.wasm"))
       @compiled_wasi_deterministic_module = @engine.precompile_module(IO.binread("spec/fixtures/wasi-deterministic.wasm"))
+      @compiled_wasi_fs_module = @engine.precompile_module(IO.binread("spec/fixtures/wasi-fs.wasm"))
 
       @compiled_wasi_component = @engine.precompile_component(IO.binread("spec/fixtures/wasi-debug-p2.wasm"))
       @compiled_wasi_deterministic_component = @engine.precompile_component(IO.binread("spec/fixtures/wasi-deterministic-p2.wasm"))
+      @compiled_wasi_fs_component = @engine.precompile_component(IO.binread("spec/fixtures/wasi-fs-p2.wasm"))
     end
 
     describe "Linker.new" do
@@ -233,13 +235,103 @@ module Wasmtime
           end
         end
       end
+
+      it "writes to mapped directory" do
+        Dir.mkdir(tempfile_path("tmp"))
+        File.write(tempfile_path(File.join("tmp", "counter")), "0")
+
+        wasi_config = WasiConfig.new
+          .set_argv(["wasi-fs", "/tmp/counter"])
+          .set_mapped_directory(tempfile_path("tmp"), "/tmp", :all, :all)
+
+        expect { run_fs.call(wasi_config) }.not_to raise_error
+
+        expect(File.read(tempfile_path(File.join("tmp", "counter")))).to eq("1")
+      end
+
+      it "fails to write to mapped directory if not permitted" do
+        Dir.mkdir(tempfile_path("tmp"))
+        File.write(tempfile_path(File.join("tmp", "counter")), "0")
+
+        stderr_str = ""
+        wasi_config = WasiConfig.new
+          .set_argv(["wasi-fs", "/tmp/counter"])
+          .set_stderr_buffer(stderr_str, 40000)
+          .set_mapped_directory(tempfile_path("tmp"), "/tmp", :read, :read)
+
+        expect { run_fs.call(wasi_config) }.to raise_error do |error|
+          expect(error).to be_a(Wasmtime::Error)
+        end
+
+        expect(stderr_str).to match(/failed to create counter file/)
+
+        expect(File.read(tempfile_path(File.join("tmp", "counter")))).to eq("0")
+      end
+
+      it "fails to read from mapped directory if not permitted" do
+        Dir.mkdir(tempfile_path("tmp"))
+        File.write(tempfile_path(File.join("tmp", "counter")), "0")
+
+        stderr_str = ""
+        wasi_config = WasiConfig.new
+          .set_argv(["wasi-fs", "/tmp/counter"])
+          .set_stderr_buffer(stderr_str, 40000)
+          .set_mapped_directory(tempfile_path("tmp"), "/tmp", :mutate, :write)
+
+        expect { run_fs.call(wasi_config) }.to raise_error do |error|
+          expect(error).to be_a(Wasmtime::Error)
+        end
+
+        expect(stderr_str).to match(/failed to open counter file/)
+
+        expect(File.read(tempfile_path(File.join("tmp", "counter")))).to eq("0")
+      end
+
+      it "fails to access non-mapped directories" do
+        Dir.mkdir(tempfile_path("tmp"))
+        File.write(tempfile_path(File.join("tmp", "counter")), "0")
+
+        stderr_str = ""
+        wasi_config = WasiConfig.new
+          .set_argv(["wasi-fs", File.join(tempfile_path("tmp"), "counter")])
+          .set_stderr_buffer(stderr_str, 40000)
+
+        expect { run_fs.call(wasi_config) }.to raise_error do |error|
+          expect(error).to be_a(Wasmtime::Error)
+        end
+
+        expect(stderr_str).to match(/failed to find a pre-opened file descriptor/)
+
+        expect(File.read(tempfile_path(File.join("tmp", "counter")))).to eq("0")
+      end
+
+      it "does not accept an invalid host path" do
+        wasi_config = WasiConfig.new
+          .set_mapped_directory(tempfile_path("tmp"), "/tmp", :all, :all)
+
+        expect { run_fs.call(wasi_config) }.to raise_error do |error|
+          expect(error).to be_a(Wasmtime::Error)
+          # error message is os-specific
+        end
+      end
+
+      it "does not accept invalid permissions" do
+        wasi_config = WasiConfig.new
+          .set_mapped_directory(tempfile_path("tmp"), "/tmp", :mutate, :invalid_permission)
+
+        expect { run_fs.call(wasi_config) }.to raise_error do |error|
+          expect(error).to be_a(Wasmtime::Error)
+          expect(error.message).to match(/Invalid file_perms: invalid_permission. Use one of :read, :write, or :all/)
+        end
+      end
     end
 
     describe "WasiConfig preview 1" do
       it_behaves_like WasiConfig do
         let(:run) { method(:run_wasi_module) }
         let(:wasi_env) { method(:wasi_module_env) }
         let(:run_deterministic) { method(:run_wasi_module_deterministic) }
+        let(:run_fs) { method(:run_wasi_module_fs) }
       end
     end
 
@@ -248,6 +340,7 @@ module Wasmtime
         let(:run) { method(:run_wasi_component) }
         let(:wasi_env) { method(:wasi_component_env) }
         let(:run_deterministic) { method(:run_wasi_component_deterministic) }
+        let(:run_fs) { method(:run_wasi_component_fs) }
       end
     end
 
@@ -272,6 +365,13 @@ def run_wasi_module_deterministic(wasi_config)
         .invoke("_start")
     end
 
+    def run_wasi_module_fs(wasi_config)
+      linker = Linker.new(@engine)
+      WASI::P1.add_to_linker_sync(linker)
+      store = Store.new(@engine, wasi_p1_config: wasi_config)
+      linker.instantiate(store, Module.deserialize(@engine, @compiled_wasi_fs_module)).invoke("_start")
+    end
+
     def wasi_module_env
       stdout_file = tempfile_path("stdout")
 
@@ -318,6 +418,17 @@ def run_wasi_component_deterministic(wasi_config)
       ).call_run(store)
     end
 
+    def run_wasi_component_fs(wasi_config)
+      linker = Component::Linker.new(@engine)
+      WASI::P2.add_to_linker_sync(linker)
+      store = Store.new(@engine, wasi_config: wasi_config)
+      Component::WasiCommand.new(
+        store,
+        Component::Component.deserialize(@engine, @compiled_wasi_fs_component),
+        linker
+      ).call_run(store)
+    end
+
     def tempfile_path(name)
       File.join(tmpdir, name)
     end