1//! Implementation for Linux / Android with `/dev/urandom` fallback
2use crate::{
3 lazy::LazyBool,
4 util_libc::{getrandom_syscall, last_os_error, sys_fill_exact},
5 {use_file, Error},
6};
7use core::mem::MaybeUninit;
8
9pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
10 // getrandom(2) was introduced in Linux 3.17
11 static HAS_GETRANDOM: LazyBool = LazyBool::new();
12 if HAS_GETRANDOM.unsync_init(is_getrandom_available) {
13 sys_fill_exact(buf:dest, sys_fill:getrandom_syscall)
14 } else {
15 use_file::getrandom_inner(dest)
16 }
17}
18
19fn is_getrandom_available() -> bool {
20 if getrandom_syscall(&mut []) < 0 {
21 match last_os_error().raw_os_error() {
22 Some(libc::ENOSYS) => false, // No kernel support
23 // The fallback on EPERM is intentionally not done on Android since this workaround
24 // seems to be needed only for specific Linux-based products that aren't based
25 // on Android. See https://github.com/rust-random/getrandom/issues/229.
26 #[cfg(target_os = "linux")]
27 Some(libc::EPERM) => false, // Blocked by seccomp
28 _ => true,
29 }
30 } else {
31 true
32 }
33}
34