ref: 74d91a0021de012908cfdb35fb61a1473a376130
dir: /lib/crypto/rand.myr/
use std use thread use "entropy" use "chacha20" pkg crypto = /* designed to mirror std.rand() */ const randbytes : (buf : byte[:] -> void) generic rand : (lo : @a, hi : @a -> @a) ::numeric,integral @a generic randnum : (-> @a) :: numeric,integral @a ;; 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]) }