mirror of
https://github.com/urbit/shrub.git
synced 2024-12-04 14:58:10 +03:00
39 lines
1.2 KiB
Markdown
39 lines
1.2 KiB
Markdown
|
## `libent`
|
||
|
|
|
||
|
|
`libent` is a cross-platform wrapper around `getentropy(2)`. It exports
|
||
|
|
one symbol, `ent_getentropy`. If getentropy is available, then it's just
|
||
|
|
a shim around that. Otherwise, it uses `getrandom(2)` (available since
|
||
|
|
kernel 3.17) on Linux, or `/dev/urandom` on other \*nix.
|
||
|
|
|
||
|
|
|
||
|
|
### Building and Testing
|
||
|
|
|
||
|
|
```bash
|
||
|
|
./configure
|
||
|
|
make
|
||
|
|
make test
|
||
|
|
PREFIX=/usr/local make install
|
||
|
|
```
|
||
|
|
|
||
|
|
### Why?
|
||
|
|
|
||
|
|
`getentropy` is the wave of the future. It's the correct API for
|
||
|
|
generating small amounts of entropy to create cryptographic keys or seed
|
||
|
|
PRNGs. It's good and reasonable and true, it's on Linux, \*BSD, and OS
|
||
|
|
X, and it only took us fifty years of UNIX to get here.
|
||
|
|
|
||
|
|
Sadly, it only just arrived, so nobody has it yet. It didn't land in
|
||
|
|
Linux until glibc 2.25, which seems to only have made it into Debian 10.
|
||
|
|
|
||
|
|
Once `getentropy` is everywhere you care about, you can just do a
|
||
|
|
s/ent\_//g on all the call sites and discard this shim.
|
||
|
|
|
||
|
|
This project began because [Urbit](https://github.com/urbit/urbit)'s
|
||
|
|
entropy-generation function was bothering me. Then it got out of hand.
|
||
|
|
|
||
|
|
|
||
|
|
### References
|
||
|
|
|
||
|
|
* [OpenBSD getentropy](https://man.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2)
|
||
|
|
* [djb on entropy gathering](https://blog.cr.yp.to/20140205-entropy.html)
|