use cap_rand instead of getrandom

Cargo.lock

@@ -241,6 +241,15 @@ dependencies = [
  "winx 0.21.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "cap-rand"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8289d98c0c748a22f1815bc68159255ca059cb4170371c8ab16b11b26886698c"
+dependencies = [
+ "rand",
+]
+
 [[package]]
 name = "cap-std"
 version = "0.7.0"
@@ -2437,11 +2446,11 @@ version = "0.21.0"
 dependencies = [
  "anyhow",
  "cap-fs-ext",
+ "cap-rand",
  "cap-std 0.8.0",
  "cap-time-ext",
  "cfg-if 1.0.0",
  "fs-set-times",
- "getrandom 0.2.0",
  "libc",
  "system-interface",
  "thiserror",

crates/wasi-c2/Cargo.toml

@@ -22,13 +22,13 @@ links = "wasi-c2-19"
 anyhow = "1.0"
 thiserror = "1.0"
 libc = "0.2"
-getrandom = { version = "0.2.0", features = ["std"] }
 wiggle = { path = "../wiggle", default-features = false, version = "0.21.0" }
 tracing = "0.1.19"
 system-interface = "0.2"
 cap-std = "0.8"
 cap-fs-ext = "0.8"
 cap-time-ext = "0.8"
+cap-rand = "0.8"
 fs-set-times = "0.2.1"
 cfg-if = "1"
 

crates/wasi-c2/src/ctx.rs

@@ -1,10 +1,10 @@
 use crate::clocks::{WasiMonotonicClock, WasiSystemClock};
 use crate::dir::{DirCaps, DirEntry, WasiDir};
 use crate::file::{FileCaps, FileEntry, WasiFile};
-use crate::random::WasiRandom;
 use crate::string_array::{StringArray, StringArrayError};
 use crate::table::Table;
 use crate::Error;
+use cap_rand::RngCore;
 use std::cell::{RefCell, RefMut};
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
@@ -12,7 +12,7 @@ use std::rc::Rc;
 pub struct WasiCtx {
     pub(crate) args: StringArray,
     pub(crate) env: StringArray,
-    pub(crate) random: Box<dyn WasiRandom>,
+    pub(crate) random: RefCell<Box<dyn RngCore>>,
     pub(crate) clocks: WasiCtxClocks,
     table: Rc<RefCell<Table>>,
 }
@@ -26,7 +26,7 @@ impl WasiCtx {
         WasiCtx {
             args: StringArray::new(),
             env: StringArray::new(),
-            random: Box::new(crate::random::GetRandom),
+            random: RefCell::new(Box::new(unsafe { cap_rand::rngs::OsRng::default() })),
             clocks: WasiCtxClocks::default(),
             table: Rc::new(RefCell::new(Table::new())),
         }
@@ -117,8 +117,8 @@ impl WasiCtxBuilder {
         Ok(self)
     }
 
-    pub fn random(&mut self, random: Box<dyn WasiRandom>) -> &mut Self {
-        self.0.random = random;
+    pub fn random(&mut self, random: Box<dyn RngCore>) -> &mut Self {
+        self.0.random.replace(random);
         self
     }
 }

crates/wasi-c2/src/error.rs

@@ -13,8 +13,8 @@ pub enum Error {
     TryFromInt(#[from] std::num::TryFromIntError),
     #[error("Utf8Error: {0}")]
     Utf8(#[from] std::str::Utf8Error),
-    #[error("GetRandom: {0}")]
-    GetRandom(#[from] getrandom::Error),
+    #[error("cap_rand Error: {0}")]
+    CapRand(#[from] cap_rand::Error),
 
     /// Errno::Notcapable: Extension: Capabilities insufficient
     #[error("File not capable: desired {desired:?}, has {has:?}")]

crates/wasi-c2/src/random.rs

@@ -1,40 +1,32 @@
-use crate::Error;
-use std::cell::RefCell;
-
-pub trait WasiRandom {
-    fn get(&self, buf: &mut [u8]) -> Result<(), Error>;
-}
-
-/// Implement `WasiRandom` using the `getrandom` crate, which selects your system's best entropy
-/// source.
-pub struct GetRandom;
-
-impl WasiRandom for GetRandom {
-    fn get(&self, buf: &mut [u8]) -> Result<(), Error> {
-        getrandom::getrandom(buf)?;
-        Ok(())
-    }
-}
+use cap_rand::RngCore;
 
 /// Implement `WasiRandom` using a deterministic cycle of bytes.
 pub struct Deterministic {
-    sequence: RefCell<std::iter::Cycle<std::vec::IntoIter<u8>>>,
+    cycle: std::iter::Cycle<std::vec::IntoIter<u8>>,
 }
 
 impl Deterministic {
     pub fn new(bytes: Vec<u8>) -> Self {
         Deterministic {
-            sequence: RefCell::new(bytes.into_iter().cycle()),
+            cycle: bytes.into_iter().cycle(),
         }
     }
 }
 
-impl WasiRandom for Deterministic {
-    fn get(&self, buf: &mut [u8]) -> Result<(), Error> {
-        let mut s = self.sequence.borrow_mut();
+impl RngCore for Deterministic {
+    fn next_u32(&mut self) -> u32 {
+        todo!()
+    }
+    fn next_u64(&mut self) -> u64 {
+        todo!()
+    }
+    fn fill_bytes(&mut self, buf: &mut [u8]) {
         for b in buf.iter_mut() {
-            *b = s.next().expect("infinite sequence");
+            *b = self.cycle.next().expect("infinite sequence");
         }
+    }
+    fn try_fill_bytes(&mut self, buf: &mut [u8]) -> Result<(), cap_rand::Error> {
+        self.fill_bytes(buf);
         Ok(())
     }
 }
@@ -44,9 +36,9 @@ mod test {
     use super::*;
     #[test]
     fn deterministic() {
-        let det = Deterministic::new(vec![1, 2, 3, 4]);
+        let mut det = Deterministic::new(vec![1, 2, 3, 4]);
         let mut buf = vec![0; 1024];
-        det.get(&mut buf).expect("get randomness");
+        det.try_fill_bytes(&mut buf).expect("get randomness");
         for (ix, b) in buf.iter().enumerate() {
             assert_eq!(*b, (ix % 4) as u8 + 1)
         }

crates/wasi-c2/src/snapshots/preview_1.rs

@@ -65,7 +65,7 @@ impl From<Error> for types::Errno {
                 | ErrorKind::UnexpectedEof
                 | _ => Errno::Io,
             },
-            Error::GetRandom(_) => Errno::Io,
+            Error::CapRand(_) => Errno::Io,
             Error::TooBig => Errno::TooBig,
             Error::Acces => Errno::Acces,
             Error::Badf => Errno::Badf,
@@ -824,7 +824,7 @@ impl<'a> wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
 
     fn random_get(&self, buf: &GuestPtr<u8>, buf_len: types::Size) -> Result<(), Error> {
         let mut buf = buf.as_array(buf_len).as_slice_mut()?;
-        self.random.get(buf.deref_mut())?;
+        self.random.borrow_mut().try_fill_bytes(buf.deref_mut())?;
         Ok(())
     }