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850: Add builder API for WasiState r=MarkMcCaskey a=MarkMcCaskey Nicer to use and it checks for errors! # Review - [x] Add a short description of the the change to the CHANGELOG.md file Co-authored-by: Mark McCaskey <[email protected]> Co-authored-by: Mark McCaskey <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,289 @@ | ||
| //! Builder code for [`WasiState`] | ||
| use crate::state::{WasiFs, WasiState}; | ||
| use std::path::{Path, PathBuf}; | ||
|
|
||
| /// Creates an empty [`WasiStateBuilder`]. | ||
| pub(crate) fn create_wasi_state(program_name: &str) -> WasiStateBuilder { | ||
| WasiStateBuilder { | ||
| args: vec![program_name.bytes().collect()], | ||
| ..WasiStateBuilder::default() | ||
| } | ||
| } | ||
|
|
||
| /// Type for building an instance of [`WasiState`] | ||
| #[derive(Debug, Default, Clone, PartialEq)] | ||
| pub struct WasiStateBuilder { | ||
| args: Vec<Vec<u8>>, | ||
| envs: Vec<Vec<u8>>, | ||
| preopened_files: Vec<PathBuf>, | ||
| mapped_dirs: Vec<(String, PathBuf)>, | ||
| } | ||
|
|
||
| /// Error type returned when bad data is given to [`WasiStateBuilder`]. | ||
| #[derive(Debug, PartialEq, Eq)] | ||
| pub enum WasiStateCreationError { | ||
| EnvironmentVariableFormatError(String), | ||
| ArgumentContainsNulByte(String), | ||
| PreopenedDirectoryNotFound(PathBuf), | ||
| MappedDirAliasFormattingError(String), | ||
| WasiFsCreationError(String), | ||
| } | ||
|
|
||
| fn validate_mapped_dir_alias(alias: &str) -> Result<(), WasiStateCreationError> { | ||
| for byte in alias.bytes() { | ||
| match byte { | ||
| b'/' => { | ||
| return Err(WasiStateCreationError::MappedDirAliasFormattingError( | ||
| format!("Alias \"{}\" contains the character '/'", alias), | ||
| )); | ||
| } | ||
| b'\0' => { | ||
| return Err(WasiStateCreationError::MappedDirAliasFormattingError( | ||
| format!("Alias \"{}\" contains a nul byte", alias), | ||
| )); | ||
| } | ||
| _ => (), | ||
| } | ||
| } | ||
|
|
||
| Ok(()) | ||
| } | ||
|
|
||
| // TODO add other WasiFS APIs here like swapping out stdout, for example (though we need to | ||
| // return stdout somehow, it's unclear what that API should look like) | ||
| impl WasiStateBuilder { | ||
| /// Add an environment variable pair. | ||
| /// Environment variable keys and values must not contain the byte `=` (0x3d) | ||
| /// or nul (0x0). | ||
| pub fn env<Key, Value>(&mut self, key: Key, value: Value) -> &mut Self | ||
| where | ||
| Key: AsRef<[u8]>, | ||
| Value: AsRef<[u8]>, | ||
| { | ||
| let key_b = key.as_ref(); | ||
| let val_b = value.as_ref(); | ||
|
|
||
| let length = key_b.len() + val_b.len() + 1; | ||
| let mut byte_vec = Vec::with_capacity(length); | ||
|
|
||
| byte_vec.extend_from_slice(&key_b); | ||
| byte_vec.push(b'='); | ||
| byte_vec.extend_from_slice(&val_b); | ||
|
|
||
| self.envs.push(byte_vec); | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Add an argument. | ||
| /// Arguments must not contain the nul (0x0) byte | ||
| pub fn arg<Arg>(&mut self, arg: Arg) -> &mut Self | ||
| where | ||
| Arg: AsRef<[u8]>, | ||
| { | ||
| let arg_b = arg.as_ref(); | ||
| let mut byte_vec = Vec::with_capacity(arg_b.len()); | ||
| byte_vec.extend_from_slice(&arg_b); | ||
| self.args.push(byte_vec); | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Add multiple environment variable pairs. | ||
| /// Keys and values must not contain the `=` (0x3d) or nul (0x0) byte. | ||
| pub fn envs<I, Key, Value>(&mut self, env_pairs: I) -> &mut Self | ||
| where | ||
| I: IntoIterator<Item = (Key, Value)>, | ||
| Key: AsRef<[u8]>, | ||
| Value: AsRef<[u8]>, | ||
| { | ||
| for (key, value) in env_pairs { | ||
| let key_b = key.as_ref(); | ||
| let val_b = value.as_ref(); | ||
|
|
||
| let length = key_b.len() + val_b.len() + 1; | ||
| let mut byte_vec = Vec::with_capacity(length); | ||
|
|
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| byte_vec.extend_from_slice(&key_b); | ||
| byte_vec.push(b'='); | ||
| byte_vec.extend_from_slice(&val_b); | ||
|
|
||
| self.envs.push(byte_vec); | ||
| } | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Add multiple arguments. | ||
| /// Arguments must not contain the nul (0x0) byte | ||
| pub fn args<I, Arg>(&mut self, args: I) -> &mut Self | ||
| where | ||
| I: IntoIterator<Item = Arg>, | ||
| Arg: AsRef<[u8]>, | ||
| { | ||
| for arg in args { | ||
| let arg_b = arg.as_ref(); | ||
| let mut byte_vec = Vec::with_capacity(arg_b.len()); | ||
| byte_vec.extend_from_slice(&arg_b); | ||
| self.args.push(byte_vec); | ||
| } | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Preopen a directory | ||
| /// This opens the given directory at the virtual root, `/`, and allows | ||
| /// the WASI module to read and write to the given directory. | ||
| // TODO: design a simple API for passing in permissions here (i.e. read-only) | ||
| pub fn preopen_dir<FilePath>(&mut self, po_dir: FilePath) -> &mut Self | ||
| where | ||
| FilePath: AsRef<Path>, | ||
| { | ||
| let path = po_dir.as_ref(); | ||
| self.preopened_files.push(path.to_path_buf()); | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Preopen a directory | ||
| /// This opens the given directory at the virtual root, `/`, and allows | ||
| /// the WASI module to read and write to the given directory. | ||
| pub fn preopen_dirs<I, FilePath>(&mut self, po_dirs: I) -> &mut Self | ||
| where | ||
| I: IntoIterator<Item = FilePath>, | ||
| FilePath: AsRef<Path>, | ||
| { | ||
| for po_dir in po_dirs { | ||
| let path = po_dir.as_ref(); | ||
| self.preopened_files.push(path.to_path_buf()); | ||
| } | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Preopen a directory with a different name exposed to the WASI. | ||
| pub fn map_dir<FilePath>(&mut self, alias: &str, po_dir: FilePath) -> &mut Self | ||
| where | ||
| FilePath: AsRef<Path>, | ||
| { | ||
| let path = po_dir.as_ref(); | ||
| self.mapped_dirs | ||
| .push((alias.to_string(), path.to_path_buf())); | ||
|
|
||
| self | ||
| } | ||
|
|
||
| /// Consumes the [`WasiStateBuilder`] and produces a [`WasiState`] | ||
| /// | ||
| /// Returns the error from `WasiFs::new` if there's an error | ||
| pub fn build(&mut self) -> Result<WasiState, WasiStateCreationError> { | ||
| for (i, arg) in self.args.iter().enumerate() { | ||
| for b in arg.iter() { | ||
| if *b == 0 { | ||
| return Err(WasiStateCreationError::ArgumentContainsNulByte( | ||
| std::str::from_utf8(arg) | ||
| .unwrap_or(if i == 0 { | ||
| "Inner error: program name is invalid utf8!" | ||
| } else { | ||
| "Inner error: arg is invalid utf8!" | ||
| }) | ||
| .to_string(), | ||
| )); | ||
| } | ||
| } | ||
| } | ||
| for env in self.envs.iter() { | ||
| let mut eq_seen = false; | ||
| for b in env.iter() { | ||
| match *b { | ||
| b'=' => { | ||
| if eq_seen { | ||
| return Err(WasiStateCreationError::EnvironmentVariableFormatError( | ||
| format!( | ||
| "found '=' in env var string \"{}\" (key=value)", | ||
| std::str::from_utf8(env) | ||
| .unwrap_or("Inner error: env var is invalid_utf8!") | ||
| ), | ||
| )); | ||
| } | ||
| eq_seen = true; | ||
| } | ||
| 0 => { | ||
| return Err(WasiStateCreationError::EnvironmentVariableFormatError( | ||
| format!( | ||
| "found nul byte in env var string \"{}\" (key=value)", | ||
| std::str::from_utf8(env) | ||
| .unwrap_or("Inner error: env var is invalid_utf8!") | ||
| ), | ||
| )); | ||
| } | ||
| _ => (), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| for po_f in self.preopened_files.iter() { | ||
| if !po_f.exists() { | ||
| return Err(WasiStateCreationError::PreopenedDirectoryNotFound( | ||
| po_f.clone(), | ||
| )); | ||
| } | ||
| } | ||
|
|
||
| for (alias, po_f) in self.mapped_dirs.iter() { | ||
| if !po_f.exists() { | ||
| return Err(WasiStateCreationError::PreopenedDirectoryNotFound( | ||
| po_f.clone(), | ||
| )); | ||
| } | ||
| validate_mapped_dir_alias(&alias)?; | ||
| } | ||
| Ok(WasiState { | ||
| fs: WasiFs::new(&self.preopened_files, &self.mapped_dirs) | ||
| .map_err(WasiStateCreationError::WasiFsCreationError)?, | ||
| args: self.args.clone(), | ||
| envs: self.envs.clone(), | ||
| }) | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod test { | ||
| use super::*; | ||
|
|
||
| #[test] | ||
| fn env_var_errors() { | ||
| let output = create_wasi_state("test_prog") | ||
| .env("HOM=E", "/home/home") | ||
| .build(); | ||
| match output { | ||
| Err(WasiStateCreationError::EnvironmentVariableFormatError(_)) => assert!(true), | ||
| _ => assert!(false), | ||
| } | ||
|
|
||
| let output = create_wasi_state("test_prog") | ||
| .env("HOME\0", "/home/home") | ||
| .build(); | ||
| match output { | ||
| Err(WasiStateCreationError::EnvironmentVariableFormatError(_)) => assert!(true), | ||
| _ => assert!(false), | ||
| } | ||
| } | ||
|
|
||
| #[test] | ||
| fn nul_character_in_args() { | ||
| let output = create_wasi_state("test_prog").arg("--h\0elp").build(); | ||
| match output { | ||
| Err(WasiStateCreationError::ArgumentContainsNulByte(_)) => assert!(true), | ||
| _ => assert!(false), | ||
| } | ||
| let output = create_wasi_state("test_prog") | ||
| .args(&["--help", "--wat\0"]) | ||
| .build(); | ||
| match output { | ||
| Err(WasiStateCreationError::ArgumentContainsNulByte(_)) => assert!(true), | ||
| _ => assert!(false), | ||
| } | ||
| } | ||
| } |
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