Implement preopened_dir using set_mapped_directory setting (#498)

* Implement preopened_dir using set_mapped_directory setting

Add support for directory and file permissions

* Add tests for mapped directories

* Use rust struct instead of nested RArrays

* Model enums as SymbolEnums

* Lazily convert ruby MappedDirectory values to rust

---------

Co-authored-by: Ahmed Al Hafoudh <alhafoudh@freevision.sk>
Co-authored-by: william-stacken <william-stacken@users.noreply.github.com>

Author: william-stacken

ext/src/ruby_api/wasi_config.rs

@@ -1,16 +1,51 @@
 use super::root;
 use crate::error;
 use crate::helpers::OutputLimitedBuffer;
+use crate::ruby_api::convert::ToValType;
+use crate::{define_rb_intern, helpers::SymbolEnum};
+use lazy_static::lazy_static;
 use magnus::{
     class, function, gc::Marker, method, typed_data::Obj, value::Opaque, DataTypeFunctions, Error,
-    Module, Object, RArray, RHash, RString, Ruby, TryConvert, TypedData,
+    IntoValue, Module, Object, RArray, RHash, RString, Ruby, Symbol, TryConvert, TypedData, Value,
 };
+use rb_sys::ruby_rarray_flags::RARRAY_EMBED_FLAG;
 use std::cell::RefCell;
+use std::convert::TryFrom;
 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};
+
+define_rb_intern!(
+    READ => "read",
+    WRITE => "write",
+    MUTATE => "mutate",
+    ALL => "all",
+);
+
+lazy_static! {
+    static ref FILE_PERMS_MAPPING: SymbolEnum<'static, FilePerms> = {
+        let mapping = vec![
+            (*READ, FilePerms::READ),
+            (*WRITE, FilePerms::WRITE),
+            (*ALL, FilePerms::all()),
+        ];
+
+        SymbolEnum::new(":file_perms", mapping)
+    };
+    static ref DIR_PERMS_MAPPING: SymbolEnum<'static, DirPerms> = {
+        let mapping = vec![
+            (*READ, DirPerms::READ),
+            (*MUTATE, DirPerms::MUTATE),
+            (*ALL, DirPerms::all()),
+        ];
+
+        SymbolEnum::new(":dir_perms", mapping)
+    };
+}
 
 enum ReadStream {
     Inherit,
@@ -43,6 +78,24 @@ impl WriteStream {
     }
 }
 
+struct PermsSymbolEnum(Symbol);
+
+#[derive(Clone)]
+struct MappedDirectory {
+    host_path: Opaque<RString>,
+    guest_path: Opaque<RString>,
+    dir_perms: Opaque<Symbol>,
+    file_perms: Opaque<Symbol>,
+}
+impl MappedDirectory {
+    pub fn mark(&self, marker: &Marker) {
+        marker.mark(self.host_path);
+        marker.mark(self.guest_path);
+        marker.mark(self.dir_perms);
+        marker.mark(self.file_perms);
+    }
+}
+
 #[derive(Default)]
 struct WasiConfigInner {
     stdin: Option<ReadStream>,
@@ -51,6 +104,7 @@ struct WasiConfigInner {
     env: Option<Opaque<RHash>>,
     args: Option<Opaque<RArray>>,
     deterministic: bool,
+    mapped_directories: Vec<MappedDirectory>,
 }
 
 impl WasiConfigInner {
@@ -70,6 +124,23 @@ impl WasiConfigInner {
         if let Some(v) = self.args.as_ref() {
             marker.mark(*v);
         }
+        for v in &self.mapped_directories {
+            v.mark(marker);
+        }
+    }
+}
+
+impl TryFrom<PermsSymbolEnum> for DirPerms {
+    type Error = magnus::Error;
+    fn try_from(value: PermsSymbolEnum) -> Result<Self, Error> {
+        DIR_PERMS_MAPPING.get(value.0.into_value())
+    }
+}
+
+impl TryFrom<PermsSymbolEnum> for FilePerms {
+    type Error = magnus::Error;
+    fn try_from(value: PermsSymbolEnum) -> Result<Self, Error> {
+        FILE_PERMS_MAPPING.get(value.0.into_value())
     }
 }
 
@@ -233,6 +304,34 @@ 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_dir = MappedDirectory {
+            host_path: host_path.into(),
+            guest_path: guest_path.into(),
+            dir_perms: dir_perms.into(),
+            file_perms: file_perms.into(),
+        };
+
+        let mut inner = rb_self.inner.borrow_mut();
+        inner.mapped_directories.push(mapped_dir);
+
+        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 +416,22 @@ impl WasiConfig {
             deterministic_wasi_ctx::add_determinism_to_wasi_ctx_builder(&mut builder);
         }
 
+        for mapped_dir in &inner.mapped_directories {
+            let host_path = ruby.get_inner(mapped_dir.host_path).to_string()?;
+            let guest_path = ruby.get_inner(mapped_dir.guest_path).to_string()?;
+            let dir_perms = ruby.get_inner(mapped_dir.dir_perms);
+            let file_perms = ruby.get_inner(mapped_dir.file_perms);
+
+            builder
+                .preopened_dir(
+                    Path::new(&host_path),
+                    &guest_path,
+                    PermsSymbolEnum(dir_perms).try_into()?,
+                    PermsSymbolEnum(file_perms).try_into()?,
+                )
+                .map_err(|e| error!("{}", e))?;
+        }
+
         Ok(builder)
     }
 }
@@ -355,5 +470,10 @@ 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-p2.wasm

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

spec/fixtures/wasi-fs.wasm

@@ -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/.cargo/config.toml

@@ -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/Cargo.toml

@@ -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/fixtures/wasi-fs/README.md

@@ -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(ArgumentError)
+          expect(error.message).to match(/invalid :file_perms, expected one of \[:read, :write, :all\], got :invalid_permission/)
+        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