/
lib.rs
413 lines (405 loc) · 20.2 KB
/
lib.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
//! Interface to the operating system's random number generator.
//!
//! # Supported targets
//!
//! | Target | Target Triple | Implementation
//! | ----------------- | ------------------ | --------------
//! | Linux, Android | `*‑linux‑*` | [`getrandom`][1] system call if available, otherwise [`/dev/urandom`][2] after successfully polling `/dev/random`
//! | Windows | `*‑windows‑*` | [`BCryptGenRandom`]
//! | macOS | `*‑apple‑darwin` | [`getentropy`][3]
//! | iOS, tvOS, watchOS | `*‑apple‑ios`, `*-apple-tvos`, `*-apple-watchos` | [`CCRandomGenerateBytes`]
//! | FreeBSD | `*‑freebsd` | [`getrandom`][5] if available, otherwise [`kern.arandom`][6]
//! | OpenBSD | `*‑openbsd` | [`getentropy`][7]
//! | NetBSD | `*‑netbsd` | [`getrandom`][16] if available, otherwise [`kern.arandom`][8]
//! | Dragonfly BSD | `*‑dragonfly` | [`getrandom`][9] if available, otherwise [`/dev/urandom`][10] (identical to `/dev/random`)
//! | Solaris, illumos | `*‑solaris`, `*‑illumos` | [`getrandom`][11] if available, otherwise [`/dev/random`][12]
//! | Fuchsia OS | `*‑fuchsia` | [`cprng_draw`]
//! | Redox | `*‑redox` | `/dev/urandom`
//! | Haiku | `*‑haiku` | `/dev/urandom` (identical to `/dev/random`)
//! | Hermit | `*-hermit` | [`sys_read_entropy`]
//! | Hurd | `*-hurd-*` | [`getrandom`][17]
//! | SGX | `x86_64‑*‑sgx` | [`RDRAND`]
//! | VxWorks | `*‑wrs‑vxworks‑*` | `randABytes` after checking entropy pool initialization with `randSecure`
//! | ESP-IDF | `*‑espidf` | [`esp_fill_random`]
//! | Emscripten | `*‑emscripten` | [`getentropy`][13]
//! | WASI | `wasm32‑wasi` | [`random_get`]
//! | Web Browser and Node.js | `wasm*‑*‑unknown` | [`Crypto.getRandomValues`] if available, then [`crypto.randomFillSync`] if on Node.js, see [WebAssembly support]
//! | SOLID | `*-kmc-solid_*` | `SOLID_RNG_SampleRandomBytes`
//! | Nintendo 3DS | `armv6k-nintendo-3ds` | [`getrandom`][1]
//! | PS Vita | `armv7-sony-vita-newlibeabihf` | [`getentropy`][13]
//! | QNX Neutrino | `*‑nto-qnx*` | [`/dev/urandom`][14] (identical to `/dev/random`)
//! | AIX | `*-ibm-aix` | [`/dev/urandom`][15]
//!
//! There is no blanket implementation on `unix` targets that reads from
//! `/dev/urandom`. This ensures all supported targets are using the recommended
//! interface and respect maximum buffer sizes.
//!
//! Pull Requests that add support for new targets to `getrandom` are always welcome.
//!
//! ## Unsupported targets
//!
//! By default, `getrandom` will not compile on unsupported targets, but certain
//! features allow a user to select a "fallback" implementation if no supported
//! implementation exists.
//!
//! All of the below mechanisms only affect unsupported
//! targets. Supported targets will _always_ use their supported implementations.
//! This prevents a crate from overriding a secure source of randomness
//! (either accidentally or intentionally).
//!
//! ## `/dev/urandom` fallback on Linux and Android
//!
//! On Linux targets the fallback is present only if either `target_env` is `musl`,
//! or `target_arch` is one of the following: `aarch64`, `arm`, `powerpc`, `powerpc64`,
//! `s390x`, `x86`, `x86_64`. Other supported targets [require][platform-support]
//! kernel versions which support `getrandom` system call, so fallback is not needed.
//!
//! On Android targets the fallback is present only for the following `target_arch`es:
//! `aarch64`, `arm`, `x86`, `x86_64`. Other `target_arch`es (e.g. RISC-V) require
//! sufficiently high API levels.
//!
//! The fallback can be disabled by enabling the `linux_disable_fallback` crate feature.
//! Note that doing so will bump minimum supported Linux kernel version to 3.17 and
//! Android API level to 23 (Marshmallow).
//!
//! ### RDRAND on x86
//!
//! *If the `rdrand` Cargo feature is enabled*, `getrandom` will fallback to using
//! the [`RDRAND`] instruction to get randomness on `no_std` `x86`/`x86_64`
//! targets. This feature has no effect on other CPU architectures.
//!
//! ### WebAssembly support
//!
//! This crate fully supports the
//! [`wasm32-wasi`](https://github.com/CraneStation/wasi) and
//! [`wasm32-unknown-emscripten`](https://www.hellorust.com/setup/emscripten/)
//! targets. However, the `wasm32-unknown-unknown` target (i.e. the target used
//! by `wasm-pack`) is not automatically
//! supported since, from the target name alone, we cannot deduce which
//! JavaScript interface is in use (or if JavaScript is available at all).
//!
//! Instead, *if the `js` Cargo feature is enabled*, this crate will assume
//! that you are building for an environment containing JavaScript, and will
//! call the appropriate methods. Both web browser (main window and Web Workers)
//! and Node.js environments are supported, invoking the methods
//! [described above](#supported-targets) using the [`wasm-bindgen`] toolchain.
//!
//! To enable the `js` Cargo feature, add the following to the `dependencies`
//! section in your `Cargo.toml` file:
//! ```toml
//! [dependencies]
//! getrandom = { version = "0.2", features = ["js"] }
//! ```
//!
//! This can be done even if `getrandom` is not a direct dependency. Cargo
//! allows crates to enable features for indirect dependencies.
//!
//! This feature should only be enabled for binary, test, or benchmark crates.
//! Library crates should generally not enable this feature, leaving such a
//! decision to *users* of their library. Also, libraries should not introduce
//! their own `js` features *just* to enable `getrandom`'s `js` feature.
//!
//! This feature has no effect on targets other than `wasm32-unknown-unknown`.
//!
//! #### Node.js ES module support
//!
//! Node.js supports both [CommonJS modules] and [ES modules]. Due to
//! limitations in wasm-bindgen's [`module`] support, we cannot directly
//! support ES Modules running on Node.js. However, on Node v15 and later, the
//! module author can add a simple shim to support the Web Cryptography API:
//! ```js
//! import { webcrypto } from 'node:crypto'
//! globalThis.crypto = webcrypto
//! ```
//! This crate will then use the provided `webcrypto` implementation.
//!
//! ### Platform Support
//! This crate generally supports the same operating system and platform versions
//! that the Rust standard library does. Additional targets may be supported using
//! pluggable custom implementations.
//!
//! This means that as Rust drops support for old versions of operating systems
//! (such as old Linux kernel versions, Android API levels, etc) in stable releases,
//! `getrandom` may create new patch releases (`0.N.x`) that remove support for
//! outdated platform versions.
//!
//! ### Custom implementations
//!
//! The [`register_custom_getrandom!`] macro allows a user to mark their own
//! function as the backing implementation for [`getrandom`]. See the macro's
//! documentation for more information about writing and registering your own
//! custom implementations.
//!
//! Note that registering a custom implementation only has an effect on targets
//! that would otherwise not compile. Any supported targets (including those
//! using `rdrand` and `js` Cargo features) continue using their normal
//! implementations even if a function is registered.
//!
//! ## Early boot
//!
//! Sometimes, early in the boot process, the OS has not collected enough
//! entropy to securely seed its RNG. This is especially common on virtual
//! machines, where standard "random" events are hard to come by.
//!
//! Some operating system interfaces always block until the RNG is securely
//! seeded. This can take anywhere from a few seconds to more than a minute.
//! A few (Linux, NetBSD and Solaris) offer a choice between blocking and
//! getting an error; in these cases, we always choose to block.
//!
//! On Linux (when the `getrandom` system call is not available), reading from
//! `/dev/urandom` never blocks, even when the OS hasn't collected enough
//! entropy yet. To avoid returning low-entropy bytes, we first poll
//! `/dev/random` and only switch to `/dev/urandom` once this has succeeded.
//!
//! On OpenBSD, this kind of entropy accounting isn't available, and on
//! NetBSD, blocking on it is discouraged. On these platforms, nonblocking
//! interfaces are used, even when reliable entropy may not be available.
//! On the platforms where it is used, the reliability of entropy accounting
//! itself isn't free from controversy. This library provides randomness
//! sourced according to the platform's best practices, but each platform has
//! its own limits on the grade of randomness it can promise in environments
//! with few sources of entropy.
//!
//! ## Error handling
//!
//! We always choose failure over returning known insecure "random" bytes. In
//! general, on supported platforms, failure is highly unlikely, though not
//! impossible. If an error does occur, then it is likely that it will occur
//! on every call to `getrandom`, hence after the first successful call one
//! can be reasonably confident that no errors will occur.
//!
//! [1]: https://manned.org/getrandom.2
//! [2]: https://manned.org/urandom.4
//! [3]: https://www.unix.com/man-page/mojave/2/getentropy/
//! [4]: https://www.unix.com/man-page/mojave/4/urandom/
//! [5]: https://www.freebsd.org/cgi/man.cgi?query=getrandom&manpath=FreeBSD+12.0-stable
//! [6]: https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
//! [7]: https://man.openbsd.org/getentropy.2
//! [8]: https://man.netbsd.org/sysctl.7
//! [9]: https://leaf.dragonflybsd.org/cgi/web-man?command=getrandom
//! [10]: https://leaf.dragonflybsd.org/cgi/web-man?command=random§ion=4
//! [11]: https://docs.oracle.com/cd/E88353_01/html/E37841/getrandom-2.html
//! [12]: https://docs.oracle.com/cd/E86824_01/html/E54777/random-7d.html
//! [13]: https://github.com/emscripten-core/emscripten/pull/12240
//! [14]: https://www.qnx.com/developers/docs/7.1/index.html#com.qnx.doc.neutrino.utilities/topic/r/random.html
//! [15]: https://www.ibm.com/docs/en/aix/7.3?topic=files-random-urandom-devices
//! [16]: https://man.netbsd.org/getrandom.2
//! [17]: https://www.gnu.org/software/libc/manual/html_mono/libc.html#index-getrandom
//!
//! [`BCryptGenRandom`]: https://docs.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom
//! [`Crypto.getRandomValues`]: https://www.w3.org/TR/WebCryptoAPI/#Crypto-method-getRandomValues
//! [`RDRAND`]: https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide
//! [`CCRandomGenerateBytes`]: https://opensource.apple.com/source/CommonCrypto/CommonCrypto-60074/include/CommonRandom.h.auto.html
//! [`cprng_draw`]: https://fuchsia.dev/fuchsia-src/zircon/syscalls/cprng_draw
//! [`crypto.randomFillSync`]: https://nodejs.org/api/crypto.html#cryptorandomfillsyncbuffer-offset-size
//! [`esp_fill_random`]: https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/random.html#_CPPv415esp_fill_randomPv6size_t
//! [`random_get`]: https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#-random_getbuf-pointeru8-buf_len-size---errno
//! [WebAssembly support]: #webassembly-support
//! [`wasm-bindgen`]: https://github.com/rustwasm/wasm-bindgen
//! [`module`]: https://rustwasm.github.io/wasm-bindgen/reference/attributes/on-js-imports/module.html
//! [CommonJS modules]: https://nodejs.org/api/modules.html
//! [ES modules]: https://nodejs.org/api/esm.html
//! [`sys_read_entropy`]: https://github.com/hermit-os/kernel/blob/315f58ff5efc81d9bf0618af85a59963ff55f8b1/src/syscalls/entropy.rs#L47-L55
//! [platform-support]: https://doc.rust-lang.org/stable/rustc/platform-support.html
#![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/getrandom/0.2.14"
)]
#![no_std]
#![warn(rust_2018_idioms, unused_lifetimes, missing_docs)]
#![cfg_attr(docsrs, feature(doc_auto_cfg))]
#[macro_use]
extern crate cfg_if;
use crate::util::{slice_as_uninit_mut, slice_assume_init_mut};
use core::mem::MaybeUninit;
mod error;
mod util;
// To prevent a breaking change when targets are added, we always export the
// register_custom_getrandom macro, so old Custom RNG crates continue to build.
#[cfg(feature = "custom")]
mod custom;
#[cfg(feature = "std")]
mod error_impls;
pub use crate::error::Error;
// System-specific implementations.
//
// These should all provide getrandom_inner with the signature
// `fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error>`.
// The function MUST fully initialize `dest` when `Ok(())` is returned.
// The function MUST NOT ever write uninitialized bytes into `dest`,
// regardless of what value it returns.
cfg_if! {
if #[cfg(any(target_os = "haiku", target_os = "redox", target_os = "nto", target_os = "aix"))] {
mod util_libc;
#[path = "use_file.rs"] mod imp;
} else if #[cfg(all(
not(feature = "linux_disable_fallback"),
any(
// Rust supports Android API level 19 (KitKat) [0] and the next upgrade targets
// level 21 (Lollipop) [1], while `getrandom(2)` was added only in
// level 23 (Marshmallow). Note that it applies only to the "old" `target_arch`es,
// RISC-V Android targets sufficiently new API level, same will apply for potential
// new Android `target_arch`es.
// [0]: https://blog.rust-lang.org/2023/01/09/android-ndk-update-r25.html
// [1]: https://github.com/rust-lang/rust/pull/120593
all(
target_os = "android",
any(
target_arch = "aarch64",
target_arch = "arm",
target_arch = "x86",
target_arch = "x86_64",
),
),
// Only on these `target_arch`es Rust supports Linux kernel versions (3.2+)
// that precede the version (3.17) in which `getrandom(2)` was added:
// https://doc.rust-lang.org/stable/rustc/platform-support.html
all(
target_os = "linux",
any(
target_arch = "aarch64",
target_arch = "arm",
target_arch = "powerpc",
target_arch = "powerpc64",
target_arch = "s390x",
target_arch = "x86",
target_arch = "x86_64",
// Minimum supported Linux kernel version for MUSL targets
// is not specified explicitly (as of Rust 1.77) and they
// are used in practice to target pre-3.17 kernels.
target_env = "musl",
),
)
),
))] {
mod util_libc;
mod use_file;
mod lazy;
#[path = "linux_android_with_fallback.rs"] mod imp;
} else if #[cfg(any(target_os = "android", target_os = "linux"))] {
mod util_libc;
#[path = "linux_android.rs"] mod imp;
} else if #[cfg(any(target_os = "illumos", target_os = "solaris"))] {
mod util_libc;
mod use_file;
#[path = "solaris_illumos.rs"] mod imp;
} else if #[cfg(any(target_os = "freebsd", target_os = "netbsd"))] {
mod util_libc;
#[path = "bsd_arandom.rs"] mod imp;
} else if #[cfg(target_os = "dragonfly")] {
mod util_libc;
mod use_file;
#[path = "dragonfly.rs"] mod imp;
} else if #[cfg(target_os = "fuchsia")] {
#[path = "fuchsia.rs"] mod imp;
} else if #[cfg(any(target_os = "ios", target_os = "watchos", target_os = "tvos"))] {
#[path = "apple-other.rs"] mod imp;
} else if #[cfg(target_os = "macos")] {
mod util_libc;
#[path = "macos.rs"] mod imp;
} else if #[cfg(target_os = "openbsd")] {
mod util_libc;
#[path = "openbsd.rs"] mod imp;
} else if #[cfg(all(target_arch = "wasm32", target_os = "wasi"))] {
#[path = "wasi.rs"] mod imp;
} else if #[cfg(target_os = "hermit")] {
#[path = "hermit.rs"] mod imp;
} else if #[cfg(target_os = "vxworks")] {
mod util_libc;
#[path = "vxworks.rs"] mod imp;
} else if #[cfg(target_os = "solid_asp3")] {
#[path = "solid.rs"] mod imp;
} else if #[cfg(target_os = "espidf")] {
#[path = "espidf.rs"] mod imp;
} else if #[cfg(windows)] {
#[path = "windows.rs"] mod imp;
} else if #[cfg(all(target_os = "horizon", target_arch = "arm"))] {
// We check for target_arch = "arm" because the Nintendo Switch also
// uses Horizon OS (it is aarch64).
mod util_libc;
#[path = "3ds.rs"] mod imp;
} else if #[cfg(target_os = "vita")] {
mod util_libc;
#[path = "vita.rs"] mod imp;
} else if #[cfg(target_os = "emscripten")] {
mod util_libc;
#[path = "emscripten.rs"] mod imp;
} else if #[cfg(all(target_arch = "x86_64", target_env = "sgx"))] {
mod lazy;
#[path = "rdrand.rs"] mod imp;
} else if #[cfg(all(feature = "rdrand",
any(target_arch = "x86_64", target_arch = "x86")))] {
mod lazy;
#[path = "rdrand.rs"] mod imp;
} else if #[cfg(all(feature = "js",
any(target_arch = "wasm32", target_arch = "wasm64"),
target_os = "unknown"))] {
#[path = "js.rs"] mod imp;
} else if #[cfg(target_os = "hurd")] {
mod util_libc;
#[path = "hurd.rs"] mod imp;
} else if #[cfg(feature = "custom")] {
use custom as imp;
} else if #[cfg(all(any(target_arch = "wasm32", target_arch = "wasm64"),
target_os = "unknown"))] {
compile_error!("the wasm*-unknown-unknown targets are not supported by \
default, you may need to enable the \"js\" feature. \
For more information see: \
https://docs.rs/getrandom/#webassembly-support");
} else {
compile_error!("target is not supported, for more information see: \
https://docs.rs/getrandom/#unsupported-targets");
}
}
/// Fill `dest` with random bytes from the system's preferred random number
/// source.
///
/// This function returns an error on any failure, including partial reads. We
/// make no guarantees regarding the contents of `dest` on error. If `dest` is
/// empty, `getrandom` immediately returns success, making no calls to the
/// underlying operating system.
///
/// Blocking is possible, at least during early boot; see module documentation.
///
/// In general, `getrandom` will be fast enough for interactive usage, though
/// significantly slower than a user-space CSPRNG; for the latter consider
/// [`rand::thread_rng`](https://docs.rs/rand/*/rand/fn.thread_rng.html).
#[inline]
pub fn getrandom(dest: &mut [u8]) -> Result<(), Error> {
// SAFETY: The `&mut MaybeUninit<_>` reference doesn't escape, and
// `getrandom_uninit` guarantees it will never de-initialize any part of
// `dest`.
getrandom_uninit(unsafe { slice_as_uninit_mut(dest) })?;
Ok(())
}
/// Version of the `getrandom` function which fills `dest` with random bytes
/// returns a mutable reference to those bytes.
///
/// On successful completion this function is guaranteed to return a slice
/// which points to the same memory as `dest` and has the same length.
/// In other words, it's safe to assume that `dest` is initialized after
/// this function has returned `Ok`.
///
/// No part of `dest` will ever be de-initialized at any point, regardless
/// of what is returned.
///
/// # Examples
///
/// ```ignore
/// # // We ignore this test since `uninit_array` is unstable.
/// #![feature(maybe_uninit_uninit_array)]
/// # fn main() -> Result<(), getrandom::Error> {
/// let mut buf = core::mem::MaybeUninit::uninit_array::<1024>();
/// let buf: &mut [u8] = getrandom::getrandom_uninit(&mut buf)?;
/// # Ok(()) }
/// ```
#[inline]
pub fn getrandom_uninit(dest: &mut [MaybeUninit<u8>]) -> Result<&mut [u8], Error> {
if !dest.is_empty() {
imp::getrandom_inner(dest)?;
}
// SAFETY: `dest` has been fully initialized by `imp::getrandom_inner`
// since it returned `Ok`.
Ok(unsafe { slice_assume_init_mut(dest) })
}