Separate RNG library (#470)

* seperates the RNG library

* fixes crypto tests

* adds rng256 workflow

* fixes formatting

libraries/crypto/Cargo.toml

@@ -11,17 +11,17 @@ edition = "2018"
 
 [dependencies]
 libtock_drivers = { path = "../../third_party/libtock-drivers" }
+rng256 = { path = "../rng256" }
 arrayref = "0.3.6"
 subtle = { version = "2.2.3", default-features = false, features = ["nightly"] }
 byteorder = { version = "1", default-features = false }
 hex = { version = "0.3.2", default-features = false, optional = true }
 ring = { version = "0.16.11", optional = true }
 untrusted = { version = "0.7.0", optional = true }
-rand = { version = "0.6.5", optional = true }
 serde = { version = "1.0", optional = true, features = ["derive"] }
 serde_json = { version = "=1.0.69", optional = true }
 regex = { version = "1", optional = true }
 
 [features]
-std = ["hex", "rand", "ring", "untrusted", "serde", "serde_json", "regex"]
+std = ["hex", "ring", "rng256/std", "untrusted", "serde", "serde_json", "regex"]
 with_ctap1 = []

libraries/crypto/src/ec/exponent256.rs

@@ -12,9 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use super::super::rng256::Rng256;
 use super::int256::{Digit, Int256};
 use core::ops::Mul;
+use rng256::Rng256;
 use subtle::{self, Choice, ConditionallySelectable, CtOption};
 
 // An exponent on the elliptic curve, that is an element modulo the curve order N.

libraries/crypto/src/ec/int256.rs

@@ -12,12 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use super::super::rng256::Rng256;
 use alloc::vec;
 use alloc::vec::Vec;
 use arrayref::{array_mut_ref, array_ref};
 use byteorder::{BigEndian, ByteOrder};
 use core::ops::{Add, AddAssign, Sub, SubAssign};
+use rng256::Rng256;
 use subtle::{self, Choice, ConditionallySelectable, ConstantTimeEq};
 
 const BITS_PER_DIGIT: usize = 32;

libraries/crypto/src/ecdh.rs

@@ -16,7 +16,7 @@ use super::ec::exponent256::NonZeroExponentP256;
 use super::ec::int256;
 use super::ec::int256::Int256;
 use super::ec::point::PointP256;
-use super::rng256::Rng256;
+use rng256::Rng256;
 
 pub const NBYTES: usize = int256::NBYTES;
 
@@ -98,8 +98,8 @@ impl PubKey {
 
 #[cfg(test)]
 mod test {
-    use super::super::rng256::ThreadRng256;
     use super::*;
+    use rng256::ThreadRng256;
 
     // Run more test iterations in release mode, as the code should be faster.
     #[cfg(not(debug_assertions))]

libraries/crypto/src/ecdsa.rs

@@ -17,7 +17,6 @@ use super::ec::int256;
 use super::ec::int256::Int256;
 use super::ec::point::PointP256;
 use super::hmac::hmac_256;
-use super::rng256::Rng256;
 use super::Hash256;
 use alloc::vec;
 use alloc::vec::Vec;
@@ -25,6 +24,7 @@ use alloc::vec::Vec;
 use arrayref::array_mut_ref;
 use arrayref::{array_ref, mut_array_refs};
 use core::marker::PhantomData;
+use rng256::Rng256;
 
 pub const NBYTES: usize = int256::NBYTES;
 
@@ -347,9 +347,9 @@ where
 
 #[cfg(test)]
 mod test {
-    use super::super::rng256::ThreadRng256;
     use super::super::sha256::Sha256;
     use super::*;
+    use rng256::ThreadRng256;
 
     // Run more test iterations in release mode, as the code should be faster.
     #[cfg(not(debug_assertions))]

libraries/crypto/src/lib.rs

@@ -24,7 +24,6 @@ pub mod ecdh;
 pub mod ecdsa;
 pub mod hkdf;
 pub mod hmac;
-pub mod rng256;
 pub mod sha256;
 pub mod util;
 

libraries/rng256/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "rng256"
+version = "0.1.0"
+authors = [
+  "Fabian Kaczmarczyck <kaczmarczyck@google.com>",
+  "Guillaume Endignoux <guillaumee@google.com>",
+  "Jean-Michel Picod <jmichel@google.com>",
+]
+license = "Apache-2.0"
+edition = "2018"
+
+[dependencies]
+libtock_drivers = { path = "../../third_party/libtock-drivers" }
+arrayref = "0.3.6"
+rand = { version = "0.6.5", optional = true }
+
+[features]
+std = ["rand"]

libraries/rng256/src/lib.rs

@@ -1,4 +1,4 @@
-// Copyright 2019 Google LLC
+// Copyright 2019-2022 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -12,8 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#![cfg_attr(not(feature = "std"), no_std)]
+
 use arrayref::array_ref;
 use libtock_drivers::rng;
+#[cfg(feature = "std")]
+use rand::Rng;
 
 // Lightweight RNG trait to generate uniformly distributed 256 bits.
 pub trait Rng256 {
@@ -55,8 +59,6 @@ pub struct ThreadRng256 {}
 #[cfg(feature = "std")]
 impl Rng256 for ThreadRng256 {
     fn gen_uniform_u8x32(&mut self) -> [u8; 32] {
-        use rand::Rng;
-
         let mut rng = rand::thread_rng();
         let mut result = [Default::default(); 32];
         rng.fill(&mut result);