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Avoid unconditional getrandom syscall creating a WasiCtx (#5244)

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This commit updates the default random context inserted into a
`WasiCtxt` to be seeded from `thread_rng` rather than the system's
entropy. This avoids an unconditional syscall on the creation of all
`WasiCtx` structures shouldn't reduce the quality of the random numbers
produced.
This commit is contained in:
Alex Crichton
2022-11-10 13:58:11 -06:00
committed by GitHub
parent 92f6fe36cc
commit 1f09954fa4
1 changed files with 3 additions and 2 deletions
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5
crates/wasi-common/cap-std-sync/src/lib.rs
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@@ -47,7 +47,7 @@ pub use clocks::clocks_ctx;
pub use sched::sched_ctx; pub use sched::sched_ctx;
use crate::net::Socket; use crate::net::Socket;
use cap_rand::RngCore; use cap_rand::{Rng, RngCore, SeedableRng};
use std::path::Path; use std::path::Path;
use wasi_common::{file::FileCaps, table::Table, Error, WasiCtx, WasiFile}; use wasi_common::{file::FileCaps, table::Table, Error, WasiCtx, WasiFile};
@@ -141,5 +141,6 @@ impl WasiCtxBuilder {
} }
pub fn random_ctx() -> Box<dyn RngCore + Send + Sync> { pub fn random_ctx() -> Box<dyn RngCore + Send + Sync> {
Box::new(cap_rand::std_rng_from_entropy(cap_rand::ambient_authority())) let mut rng = cap_rand::thread_rng(cap_rand::ambient_authority());
Box::new(cap_rand::rngs::StdRng::from_seed(rng.gen()))
} }