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Split OS RNG into rand_os #643

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merged 22 commits into from
Dec 29, 2018
Merged

Split OS RNG into rand_os #643

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5857a0a
split OS RNG into rand_os
newpavlov Nov 14, 2018
1c2f41d
fix solaris
newpavlov Nov 21, 2018
f8ed1d6
Merge branch 'master' into rand_os
newpavlov Nov 21, 2018
dfbeeb3
fix typo
newpavlov Nov 21, 2018
b15d39b
fix dependencies
newpavlov Nov 21, 2018
47c4ae7
fix windows again
newpavlov Nov 21, 2018
690e47d
fix wasm32
newpavlov Nov 21, 2018
9fcc652
return winapi to rand
newpavlov Nov 21, 2018
f9798cc
remove featureless wasm32-unknown-unknown build
newpavlov Nov 21, 2018
876bba5
explicitly test rand_os
newpavlov Nov 21, 2018
5887dde
use macro to make code prettier
newpavlov Nov 21, 2018
c5db7b7
sort entries
newpavlov Nov 21, 2018
1590796
fix doc links
newpavlov Nov 23, 2018
0cf29cc
move most of the docs to crate level, add usage example
newpavlov Nov 23, 2018
abecc1d
fix doc links, take 2
newpavlov Nov 23, 2018
38f7be6
Merge branch 'master' into rand_os
newpavlov Dec 27, 2018
eac492e
replace unreachable! with panic!
newpavlov Dec 29, 2018
2096c58
attempt to fix wasm CI
newpavlov Dec 29, 2018
abf5626
cargo web test only for rand_os
newpavlov Dec 29, 2018
a57925a
return unreachable
newpavlov Dec 29, 2018
808cd54
rand_os: doc and cargo improvements
dhardy Dec 29, 2018
bddd20d
Merge pull request #1 from dhardy/rand_os
newpavlov Dec 29, 2018
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203 changes: 106 additions & 97 deletions rand_os/src/lib.rs
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Expand Up @@ -9,7 +9,112 @@

//! Interface to the random number generator of the operating system.
//!
//! See `OsRng` documentation for more details.
//! `OsRng` is the preferred external source of entropy for most applications.
//! Commonly it is used to initialize a user-space RNG, which can then be used
//! to generate random values with much less overhead than `OsRng`.
//!
//! You may prefer to use [`EntropyRng`] instead of `OsRng`. It is unlikely, but
//! not entirely theoretical, for `OsRng` to fail. In such cases [`EntropyRng`]
//! falls back on a good alternative entropy source.
//!
//! `OsRng::new()` is guaranteed to be very cheap (after the first successful
//! call), and will never consume more than one file handle per process.
//!
//! # Usage example
//! ```
//! use rand_os::OsRng;
//! use rand_os::rand_core::RngCore;
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//!
//! let mut os_rng = OsRng::new().unwrap();
//! let mut key = [0u8; 16];
//! os_rng.fill_bytes(&mut key);
//! let random_u64 = os_rng.next_u64();
//! ```
//!
//! # Platform sources
//!
//! | OS | interface
//! |------------------|---------------------------------------------------------
//! | Linux, Android | [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after reading from `/dev/random` once
//! | Windows | [`RtlGenRandom`][3]
//! | macOS, iOS | [`SecRandomCopyBytes`][4]
//! | FreeBSD | [`kern.arandom`][5]
//! | OpenBSD, Bitrig | [`getentropy`][6]
//! | NetBSD | [`/dev/urandom`][7] after reading from `/dev/random` once
//! | Dragonfly BSD | [`/dev/random`][8]
//! | Solaris, illumos | [`getrandom`][9] system call if available, otherwise [`/dev/random`][10]
//! | Fuchsia OS | [`cprng_draw`][11]
//! | Redox | [`rand:`][12]
//! | CloudABI | [`random_get`][13]
//! | Haiku | `/dev/random` (identical to `/dev/urandom`)
//! | Web browsers | [`Crypto.getRandomValues`][14] (see [Support for WebAssembly and ams.js][14])
//! | Node.js | [`crypto.randomBytes`][15] (see [Support for WebAssembly and ams.js][16])
//!
//! Rand doesn't have a blanket implementation for all Unix-like operating
//! systems that reads from `/dev/urandom`. This ensures all supported operating
//! systems are using the recommended interface and respect maximum buffer
//! sizes.
//!
//! ## Support for WebAssembly and ams.js
//!
//! The three Emscripten targets `asmjs-unknown-emscripten`,
//! `wasm32-unknown-emscripten` and `wasm32-experimental-emscripten` use
//! Emscripten's emulation of `/dev/random` on web browsers and Node.js.
//!
//! The bare Wasm target `wasm32-unknown-unknown` tries to call the javascript
//! methods directly, using either `stdweb` or `wasm-bindgen` depending on what
//! features are activated for this crate. Note that if both features are
//! enabled `wasm-bindgen` will be used.
//!
//! ## Early boot
//!
//! It is possible that early in the boot process the OS hasn't had enough time
//! yet to collect entropy to securely seed its RNG, especially on virtual
//! machines.
//!
//! Some operating systems always block the thread until the RNG is securely
//! seeded. This can take anywhere from a few seconds to more than a minute.
//! Others make a best effort to use a seed from before the shutdown and don't
//! document much.
//!
//! A few, Linux, NetBSD and Solaris, offer a choice between blocking, and
//! getting an error. With `try_fill_bytes` we choose to get the error
//! ([`ErrorKind::NotReady`]), while the other methods use a blocking interface.
//!
//! On Linux (when the `genrandom` system call is not available) and on NetBSD
//! reading from `/dev/urandom` never blocks, even when the OS hasn't collected
//! enough entropy yet. As a countermeasure we try to do a single read from
//! `/dev/random` until we know the OS RNG is initialized (and store this in a
//! global static).
//!
//! # Panics
//!
//! `OsRng` is extremely unlikely to fail if `OsRng::new()`, and one read from
//! it, where succesfull. But in case it does fail, only [`try_fill_bytes`] is
//! able to report the cause. Depending on the error the other [`RngCore`]
//! methods will retry several times, and panic in case the error remains.
//!
//! [`EntropyRng`]: ../../rand/rngs/struct.EntropyRng.html
//! [`RngCore`]: ../../rand_core/trait.RngCore.html
//! [`try_fill_bytes`]: ../../rand_core/trait.RngCore.html#method.tymethod.try_fill_bytes
//! [`ErrorKind::NotReady`]: ../../rand_core/enum.ErrorKind.html#variant.NotReady
//!
//! [1]: http://man7.org/linux/man-pages/man2/getrandom.2.html
//! [2]: http://man7.org/linux/man-pages/man4/urandom.4.html
//! [3]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
//! [4]: https://developer.apple.com/documentation/security/1399291-secrandomcopybytes?language=objc
//! [5]: https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
//! [6]: https://man.openbsd.org/getentropy.2
//! [7]: http://netbsd.gw.com/cgi-bin/man-cgi?random+4+NetBSD-current
//! [8]: https://leaf.dragonflybsd.org/cgi/web-man?command=random&section=4
//! [9]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
//! [10]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
//! [11]: https://fuchsia.googlesource.com/zircon/+/HEAD/docs/syscalls/cprng_draw.md
//! [12]: https://github.com/redox-os/randd/blob/master/src/main.rs
//! [13]: https://github.com/NuxiNL/cloudabi/blob/v0.20/cloudabi.txt#L1826
//! [14]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
//! [15]: https://nodejs.org/api/crypto.html#crypto_crypto_randombytes_size_callback
//! [16]: #support-for-webassembly-and-amsjs
#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
html_favicon_url = "https://www.rust-lang.org/favicon.ico",
html_root_url = "https://docs.rs/rand_os/0.1.0")]
Expand Down Expand Up @@ -42,102 +147,6 @@ use rand_core::{CryptoRng, RngCore, Error, impls};

/// A random number generator that retrieves randomness straight from the
/// operating system.
///
/// This is the preferred external source of entropy for most applications.
/// Commonly it is used to initialize a user-space RNG, which can then be used
/// to generate random values with much less overhead than `OsRng`.
///
/// You may prefer to use [`EntropyRng`] instead of `OsRng`. It is unlikely, but
/// not entirely theoretical, for `OsRng` to fail. In such cases [`EntropyRng`]
/// falls back on a good alternative entropy source.
///
/// `OsRng::new()` is guaranteed to be very cheap (after the first successful
/// call), and will never consume more than one file handle per process.
///
/// # Platform sources
///
/// | OS | interface
/// |------------------|---------------------------------------------------------
/// | Linux, Android | [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after reading from `/dev/random` once
/// | Windows | [`RtlGenRandom`][3]
/// | macOS, iOS | [`SecRandomCopyBytes`][4]
/// | FreeBSD | [`kern.arandom`][5]
/// | OpenBSD, Bitrig | [`getentropy`][6]
/// | NetBSD | [`/dev/urandom`][7] after reading from `/dev/random` once
/// | Dragonfly BSD | [`/dev/random`][8]
/// | Solaris, illumos | [`getrandom`][9] system call if available, otherwise [`/dev/random`][10]
/// | Fuchsia OS | [`cprng_draw`][11]
/// | Redox | [`rand:`][12]
/// | CloudABI | [`random_get`][13]
/// | Haiku | `/dev/random` (identical to `/dev/urandom`)
/// | Web browsers | [`Crypto.getRandomValues`][14] (see [Support for WebAssembly and ams.js][14])
/// | Node.js | [`crypto.randomBytes`][15] (see [Support for WebAssembly and ams.js][16])
///
/// Rand doesn't have a blanket implementation for all Unix-like operating
/// systems that reads from `/dev/urandom`. This ensures all supported operating
/// systems are using the recommended interface and respect maximum buffer
/// sizes.
///
/// ## Support for WebAssembly and ams.js
///
/// The three Emscripten targets `asmjs-unknown-emscripten`,
/// `wasm32-unknown-emscripten` and `wasm32-experimental-emscripten` use
/// Emscripten's emulation of `/dev/random` on web browsers and Node.js.
///
/// The bare Wasm target `wasm32-unknown-unknown` tries to call the javascript
/// methods directly, using either `stdweb` or `wasm-bindgen` depending on what
/// features are activated for this crate. Note that if both features are
/// enabled `wasm-bindgen` will be used.
///
/// ## Early boot
///
/// It is possible that early in the boot process the OS hasn't had enough time
/// yet to collect entropy to securely seed its RNG, especially on virtual
/// machines.
///
/// Some operating systems always block the thread until the RNG is securely
/// seeded. This can take anywhere from a few seconds to more than a minute.
/// Others make a best effort to use a seed from before the shutdown and don't
/// document much.
///
/// A few, Linux, NetBSD and Solaris, offer a choice between blocking, and
/// getting an error. With `try_fill_bytes` we choose to get the error
/// ([`ErrorKind::NotReady`]), while the other methods use a blocking interface.
///
/// On Linux (when the `genrandom` system call is not available) and on NetBSD
/// reading from `/dev/urandom` never blocks, even when the OS hasn't collected
/// enough entropy yet. As a countermeasure we try to do a single read from
/// `/dev/random` until we know the OS RNG is initialized (and store this in a
/// global static).
///
/// # Panics
///
/// `OsRng` is extremely unlikely to fail if `OsRng::new()`, and one read from
/// it, where succesfull. But in case it does fail, only [`try_fill_bytes`] is
/// able to report the cause. Depending on the error the other [`RngCore`]
/// methods will retry several times, and panic in case the error remains.
///
/// [`EntropyRng`]: ../rand/rngs/struct.EntropyRng.html
/// [`RngCore`]: ../rand_core/trait.RngCore.html
/// [`try_fill_bytes`]: ../rand_core/trait.RngCore.html#method.tymethod.try_fill_bytes
/// [`ErrorKind::NotReady`]: ../rand_core/enum.ErrorKind.html#variant.NotReady
///
/// [1]: http://man7.org/linux/man-pages/man2/getrandom.2.html
/// [2]: http://man7.org/linux/man-pages/man4/urandom.4.html
/// [3]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
/// [4]: https://developer.apple.com/documentation/security/1399291-secrandomcopybytes?language=objc
/// [5]: https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
/// [6]: https://man.openbsd.org/getentropy.2
/// [7]: http://netbsd.gw.com/cgi-bin/man-cgi?random+4+NetBSD-current
/// [8]: https://leaf.dragonflybsd.org/cgi/web-man?command=random&section=4
/// [9]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
/// [10]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
/// [11]: https://fuchsia.googlesource.com/zircon/+/HEAD/docs/syscalls/cprng_draw.md
/// [12]: https://github.com/redox-os/randd/blob/master/src/main.rs
/// [13]: https://github.com/NuxiNL/cloudabi/blob/v0.20/cloudabi.txt#L1826
/// [14]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
/// [15]: https://nodejs.org/api/crypto.html#crypto_crypto_randombytes_size_callback
/// [16]: #support-for-webassembly-and-amsjs
#[derive(Clone)]
pub struct OsRng(imp::OsRng);

Expand Down