On Mon, May 25, 2020 at 05:27:37PM +0200, Christian Weisgerber wrote:
> Sebastien Marie:
>
> > > For large reads from /dev/random, use the arc4random_ctx_*() functions
> > > instead of hand-rolling the same code to set up a temporary ChaCha
> > > instance.
> >
> > Eventually, I would get ride of myctx, initialize lctx to NULL, and use
> > (lctx == NULL) to replace (myctx == 0).
>
> Right. Here we go:
Thanks. ok semarie@
> Index: rnd.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/rnd.c,v
> retrieving revision 1.213
> diff -u -p -r1.213 rnd.c
> --- rnd.c 18 May 2020 15:00:16 -0000 1.213
> +++ rnd.c 25 May 2020 14:58:43 -0000
> @@ -589,6 +589,9 @@ arc4random_ctx_free(struct arc4random_ct
> void
> arc4random_ctx_buf(struct arc4random_ctx *ctx, void *buf, size_t n)
> {
> +#ifndef KEYSTREAM_ONLY
> + memset(buf, 0, n);
> +#endif
> chacha_encrypt_bytes((chacha_ctx *)ctx, buf, buf, n);
> }
>
> @@ -701,40 +704,31 @@ randomclose(dev_t dev, int flag, int mod
> int
> randomread(dev_t dev, struct uio *uio, int ioflag)
> {
> - u_char lbuf[KEYSZ+IVSZ];
> - chacha_ctx lctx;
> + struct arc4random_ctx *lctx = NULL;
> size_t total = uio->uio_resid;
> u_char *buf;
> - int myctx = 0, ret = 0;
> + int ret = 0;
>
> if (uio->uio_resid == 0)
> return 0;
>
> buf = malloc(POOLBYTES, M_TEMP, M_WAITOK);
> - if (total > RND_MAIN_MAX_BYTES) {
> - arc4random_buf(lbuf, sizeof(lbuf));
> - chacha_keysetup(&lctx, lbuf, KEYSZ * 8);
> - chacha_ivsetup(&lctx, lbuf + KEYSZ, NULL);
> - explicit_bzero(lbuf, sizeof(lbuf));
> - myctx = 1;
> - }
> + if (total > RND_MAIN_MAX_BYTES)
> + lctx = arc4random_ctx_new();
>
> while (ret == 0 && uio->uio_resid > 0) {
> size_t n = ulmin(POOLBYTES, uio->uio_resid);
>
> - if (myctx) {
> -#ifndef KEYSTREAM_ONLY
> - memset(buf, 0, n);
> -#endif
> - chacha_encrypt_bytes(&lctx, buf, buf, n);
> - } else
> + if (lctx != NULL)
> + arc4random_ctx_buf(lctx, buf, n);
> + else
> arc4random_buf(buf, n);
> ret = uiomove(buf, n, uio);
> if (ret == 0 && uio->uio_resid > 0)
> yield();
> }
> - if (myctx)
> - explicit_bzero(&lctx, sizeof(lctx));
> + if (lctx != NULL)
> + arc4random_ctx_free(lctx);
> explicit_bzero(buf, POOLBYTES);
> free(buf, M_TEMP, POOLBYTES);
> return ret;
> --
> Christian "naddy" Weisgerber [email protected]
--
Sebastien Marie
