1 files changed, 52 insertions, 2 deletions

diff --git a/src/rust/rand/rng.rs b/src/rust/rand/rng.rs
index ea234492eb..cfd96c9617 100644
--- a/src/rust/rand/rng.rs
+++ b/src/rust/rand/rng.rs
@@ -2,7 +2,7 @@
 // Copyright (c) 2018, isis agora lovecruft
 // See LICENSE for licensing information
 
-//! Wrappers for Tor's random number generator to provide implementations of
+//! Wrappers for Tor's random number generators to provide implementations of
 //! `rand_core` traits.
 
 // This is the real implementation, in use in production, which calls into our C
@@ -18,6 +18,7 @@ mod internal {
     use rand_core::impls::next_u32_via_fill;
     use rand_core::impls::next_u64_via_fill;
 
+    use external::c_tor_crypto_rand;
     use external::c_tor_crypto_strongest_rand;
     use external::c_tor_crypto_seed_rng;
 
@@ -66,6 +67,53 @@ mod internal {
 
         // C_RUST_COUPLED: `crypto_strongest_rand()` /src/common/crypto_rand.c
         fn fill_bytes(&mut self, dest: &mut [u8]) {
+            c_tor_crypto_rand(dest);
+        }
+
+        // C_RUST_COUPLED: `crypto_strongest_rand()` /src/common/crypto_rand.c
+        fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+            Ok(self.fill_bytes(dest))
+        }
+    }
+
+    /// A CSPRNG which hashes together randomness from OpenSSL's RNG and entropy
+    /// obtained from the operating system.
+    pub struct TorStrongestRng {
+        // This private, zero-length field forces the struct to be treated the
+        // same as its opaque C couterpart.
+        _unused: [u8; 0],
+    }
+
+    /// Mark `TorRng` as being suitable for cryptographic purposes.
+    impl CryptoRng for TorStrongestRng {}
+
+    impl TorStrongestRng {
+        // C_RUST_COUPLED: `crypto_seed_rng()` /src/common/crypto_rand.c
+        #[allow(dead_code)]
+        fn new() -> Self {
+            if !c_tor_crypto_seed_rng() {
+                tor_log_msg!(LogSeverity::Warn, LogDomain::General,
+                             "TorStrongestRng::from_seed()",
+                             "The RNG could not be seeded!");
+            }
+            // XXX also log success at info level —isis
+            TorStrongestRng{ _unused: [0u8; 0] }
+        }
+    }
+
+    impl RngCore for TorStrongestRng {
+        // C_RUST_COUPLED: `crypto_strongest_rand()` /src/common/crypto_rand.c
+        fn next_u32(&mut self) -> u32 {
+            next_u32_via_fill(self)
+        }
+
+        // C_RUST_COUPLED: `crypto_strongest_rand()` /src/common/crypto_rand.c
+        fn next_u64(&mut self) -> u64 {
+            next_u64_via_fill(self)
+        }
+
+        // C_RUST_COUPLED: `crypto_strongest_rand()` /src/common/crypto_rand.c
+        fn fill_bytes(&mut self, dest: &mut [u8]) {
             debug_assert!(dest.len() <= MAX_STRONGEST_RAND_SIZE);
 
             c_tor_crypto_strongest_rand(dest);
@@ -81,7 +129,9 @@ mod internal {
 // For testing, we expose a pure-Rust implementation.
 #[cfg(test)]
 mod internal {
-    pub use rand::EntropyRng as TorRng;
+    // It doesn't matter if we pretend ChaCha is a CSPRNG in tests.
+    pub use rand::ChaChaRng as TorRng;
+    pub use rand::ChaChaRng as TorStrongestRng;
 }
 
 // Finally, expose the public functionality of whichever appropriate internal