| //! Random data generation through `getentropy`. |
| //! |
| //! Since issue 8 (2024), the POSIX specification mandates the existence of the |
| //! `getentropy` function, which fills a slice of up to `GETENTROPY_MAX` bytes |
| //! (256 on all known platforms) with random data. Unfortunately, it's only |
| //! meant to be used to seed other CPRNGs, which we don't have, so we only use |
| //! it where `arc4random_buf` and friends aren't available or secure (currently |
| //! that's only the case on Emscripten). |
| |
| pub fn fill_bytes(bytes: &mut [u8]) { |
| // GETENTROPY_MAX isn't defined yet on most platforms, but it's mandated |
| // to be at least 256, so just use that as limit. |
| for chunk in bytes.chunks_mut(256) { |
| let r = unsafe { libc::getentropy(chunk.as_mut_ptr().cast(), chunk.len()) }; |
| assert_ne!(r, -1, "failed to generate random data"); |
| } |
| } |
