rand_os backward compatibility

rand_os/Cargo.toml

@@ -21,9 +21,8 @@ log = { version = "0.4", optional = true }
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
 
-# TODO: check if all features are required
 [target.'cfg(windows)'.dependencies]
-winapi = { version = "0.3", features = ["minwindef", "ntsecapi", "profileapi", "winnt"] }
+winapi = { version = "0.3", features = ["minwindef", "ntsecapi", "winnt"] }
 
 [target.'cfg(target_os = "cloudabi")'.dependencies]
 cloudabi = "0.0.3"

rand_os/src/impls/mod.rs

@@ -0,0 +1,188 @@
+use std::fmt;
+use rand_core::{CryptoRng, RngCore, Error, impls};
+
+#[cfg(not(feature = "log"))]
+#[macro_use]
+mod dummy_log;
+
+/// A random number generator that retrieves randomness straight from the
+/// operating system.
+#[derive(Clone)]
+pub struct OsRng(imp::OsRng);
+
+impl fmt::Debug for OsRng {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl OsRng {
+    /// Create a new `OsRng`.
+    pub fn new() -> Result<OsRng, Error> {
+        imp::OsRng::new().map(OsRng)
+    }
+}
+
+impl CryptoRng for OsRng {}
+
+impl RngCore for OsRng {
+    fn next_u32(&mut self) -> u32 {
+        impls::next_u32_via_fill(self)
+    }
+
+    fn next_u64(&mut self) -> u64 {
+        impls::next_u64_via_fill(self)
+    }
+
+    fn fill_bytes(&mut self, dest: &mut [u8]) {
+        use std::{time, thread};
+
+        // We cannot return Err(..), so we try to handle before panicking.
+        const MAX_RETRY_PERIOD: u32 = 10; // max 10s
+        const WAIT_DUR_MS: u32 = 100; // retry every 100ms
+        let wait_dur = time::Duration::from_millis(WAIT_DUR_MS as u64);
+        const RETRY_LIMIT: u32 = (MAX_RETRY_PERIOD * 1000) / WAIT_DUR_MS;
+        const TRANSIENT_RETRIES: u32 = 8;
+        let mut err_count = 0;
+        let mut error_logged = false;
+
+        // Maybe block until the OS RNG is initialized
+        let mut read = 0;
+        if let Ok(n) = self.0.test_initialized(dest, true) { read = n };
+        let dest = &mut dest[read..];
+
+        loop {
+            if let Err(e) = self.try_fill_bytes(dest) {
+                if err_count >= RETRY_LIMIT {
+                    error!("OsRng failed too many times; last error: {}", e);
+                    panic!("OsRng failed too many times; last error: {}", e);
+                }
+
+                if e.kind.should_wait() {
+                    if !error_logged {
+                        warn!("OsRng failed; waiting up to {}s and retrying. Error: {}",
+                                MAX_RETRY_PERIOD, e);
+                        error_logged = true;
+                    }
+                    err_count += 1;
+                    thread::sleep(wait_dur);
+                    continue;
+                } else if e.kind.should_retry() {
+                    if !error_logged {
+                        warn!("OsRng failed; retrying up to {} times. Error: {}",
+                                TRANSIENT_RETRIES, e);
+                        error_logged = true;
+                    }
+                    err_count += (RETRY_LIMIT + TRANSIENT_RETRIES - 1)
+                            / TRANSIENT_RETRIES;    // round up
+                    continue;
+                } else {
+                    error!("OsRng failed: {}", e);
+                    panic!("OsRng fatal error: {}", e);
+                }
+            }
+
+            break;
+        }
+    }
+
+    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
+        // Some systems do not support reading 0 random bytes.
+        // (And why waste a system call?)
+        if dest.len() == 0 { return Ok(()); }
+
+        let read = self.0.test_initialized(dest, false)?;
+        let dest = &mut dest[read..];
+
+        let max = self.0.max_chunk_size();
+        if dest.len() <= max {
+            trace!("OsRng: reading {} bytes via {}",
+                   dest.len(), self.0.method_str());
+        } else {
+            trace!("OsRng: reading {} bytes via {} in {} chunks of {} bytes",
+                   dest.len(), self.0.method_str(), (dest.len() + max) / max, max);
+        }
+        for slice in dest.chunks_mut(max) {
+            self.0.fill_chunk(slice)?;
+        }
+        Ok(())
+    }
+}
+
+trait OsRngImpl where Self: Sized {
+    // Create a new `OsRng` platform interface.
+    fn new() -> Result<Self, Error>;
+
+    // Fill a chunk with random bytes.
+    fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error>;
+
+    // Test whether the OS RNG is initialized. This method may not be possible
+    // to support cheaply (or at all) on all operating systems.
+    //
+    // If `blocking` is set, this will cause the OS the block execution until
+    // its RNG is initialized.
+    //
+    // Random values that are read while this are stored in `dest`, the amount
+    // of read bytes is returned.
+    fn test_initialized(&mut self, _dest: &mut [u8], _blocking: bool)
+        -> Result<usize, Error> { Ok(0) }
+
+    // Maximum chunk size supported.
+    fn max_chunk_size(&self) -> usize { ::std::usize::MAX }
+
+    // Name of the OS interface (used for logging).
+    fn method_str(&self) -> &'static str;
+}
+
+#[cfg(any(target_os = "linux", target_os = "android",
+          target_os = "netbsd", target_os = "dragonfly",
+          target_os = "solaris", target_os = "redox",
+          target_os = "haiku", target_os = "emscripten"))]
+mod random_device;
+
+macro_rules! mod_use {
+    ($cond:meta, $module:ident) => {
+        #[$cond]
+        mod $module;
+        #[$cond]
+        use self::$module as imp;
+    }
+}
+
+mod_use!(cfg(target_os = "android"), linux_android);
+mod_use!(cfg(target_os = "bitrig"), openbsd_bitrig);
+mod_use!(cfg(target_os = "cloudabi"), cloudabi);
+mod_use!(cfg(target_os = "dragonfly"), dragonfly_haiku_emscripten);
+mod_use!(cfg(target_os = "emscripten"), dragonfly_haiku_emscripten);
+mod_use!(cfg(target_os = "freebsd"), freebsd);
+mod_use!(cfg(target_os = "fuchsia"), fuchsia);
+mod_use!(cfg(target_os = "haiku"), dragonfly_haiku_emscripten);
+mod_use!(cfg(target_os = "ios"), macos);
+mod_use!(cfg(target_os = "linux"), linux_android);
+mod_use!(cfg(target_os = "macos"), macos);
+mod_use!(cfg(target_os = "netbsd"), netbsd);
+mod_use!(cfg(target_os = "openbsd"), openbsd_bitrig);
+mod_use!(cfg(target_os = "redox"), redox);
+mod_use!(cfg(target_os = "solaris"), solaris);
+mod_use!(cfg(windows), windows);
+
+mod_use!(
+    cfg(all(
+        target_arch = "wasm32",
+        not(target_os = "emscripten"),
+        not(feature = "stdweb"),
+        feature = "wasm-bindgen"
+    )),
+    wasm32_bindgen
+);
+
+mod_use!(
+    cfg(all(
+        target_arch = "wasm32",
+        not(target_os = "emscripten"),
+        not(feature = "wasm-bindgen"),
+        feature = "stdweb",
+    )),
+    wasm32_stdweb
+);
+