ref: 17b6a133ca281986b0dfb9a1ced306e4fc99eb92
dir: /lib/crypto/rand.myr/
use std
use thread
use "entropy"
use "sha256"
use "chacha20"
pkg crypto =
/* designed to mirror std.rand() */
const randbytes : (buf : byte[:] -> void)
generic rand : (lo : @a::(integral,numeric), hi : @a::(integral,numeric) -> @a::(numeric,integral))
generic randnum : (-> @a::(numeric,integral))
;;
const Stirinterval = 16*std.MiB
var buf : byte[4096] /* let's not encrypt too often */
var rem : std.size /* size remaining in buffer */
var cnt : std.size /* count we've read since last stirring of entropy */
var ctx : chacha20ctx /* the generator */
var pid : std.pid /* for rekeying on fork and exec */
var mtx : thread.mutex /* there can be only one */
generic rand = {lo, hi
var span, lim, val, max
span = std.abs(hi - lo)
max = ~0
/* if ~0 is negative, we have a signed value with a different max */
if max < 0
max = (1 << (8*sizeof(@a)-1)) - 1
;;
lim = (max/span)*span
val = (randnum() & max)
while val > lim
val = (randnum() & max)
;;
-> val % span + lo
}
generic randnum = {
var buf : byte[8]
randbytes(buf[:])
-> std.getle64(buf[:])
}
const randbytes = {dst
var n, off, rdlen
thread.mtxlock(&mtx)
/* costly? */
if pid != std.getpid()
stir()
pid = std.getpid()
;;
n = 0
while n < dst.len
if cnt + buf.len >= Stirinterval
stir()
;;
off = buf.len - rem
rdlen = std.min(dst.len - n, rem)
std.slcp(dst[n:n+rdlen], buf[off:off+rdlen])
std.slfill(buf[off:off+rdlen], 0)
cnt += rdlen
rem -= rdlen
n += rdlen
if rem == 0
rekey([][:])
;;
;;
thread.mtxunlock(&mtx)
}
const stir = {
var entropy : byte[40]
getentropy(entropy[:])
rekey(entropy[:])
std.slfill(entropy[:], 0)
std.slfill(buf[:], 0)
rem = 0
cnt = 0
}
const rekey = {entropy
var len
chacha20encrypt(&ctx, buf[:], buf[:])
len = std.min(buf.len, entropy.len)
for var i = 0; i < len; i++
buf[i] ^= entropy[i]
;;
init(buf[:])
std.slfill(buf[:40], 0)
rem = buf.len - 40
}
const init = {buf
chacha20keysetup(&ctx, buf[:32])
chacha20ivsetup(&ctx, buf[32:40])
}