Import Monocypher 3.1.3 + monocypher-rng module

This is for somewhat later. I'd always planned to use it - it existed
already in earlier private repos, in fact. I just didn't bother to
import it here in case it wouldn't actually be needed, but with the way
current plans are going, it's definitely going to be needed, so here it
is.

1 files changed, 97 insertions, 0 deletions

diff --git a/src/3p/monocypher/monocypher-rng.c b/src/3p/monocypher/monocypher-rng.c
new file mode 100644
index 0000000..d59fc76
--- /dev/null
+++ b/src/3p/monocypher/monocypher-rng.c
@@ -0,0 +1,97 @@
+// This file is dual-licensed.  Choose whichever licence you want from
+// the two licences listed below.
+//
+// The first licence is a regular 2-clause BSD licence.  The second licence
+// is the CC-0 from Creative Commons. It is intended to release Monocypher
+// to the public domain.  The BSD licence serves as a fallback option.
+//
+// SPDX-License-Identifier: BSD-2-Clause OR CC0-1.0
+//
+// ------------------------------------------------------------------------
+//
+// Copyright (c) 2019-2021, Loup Vaillant
+// All rights reserved.
+//
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+// 1. Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in the
+//    documentation and/or other materials provided with the
+//    distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// ------------------------------------------------------------------------
+//
+// Written in 2019-2021 by Loup Vaillant
+//
+// To the extent possible under law, the author(s) have dedicated all copyright
+// and related neighboring rights to this software to the public domain
+// worldwide.  This software is distributed without any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication along
+// with this software.  If not, see
+// <https://creativecommons.org/publicdomain/zero/1.0/>
+
+#include "monocypher-rng.h"
+#include "monocypher.h"
+
+// avoid memcpy dependency (the compiler will likely use memcpy anyway)
+static void copy(uint8_t *out, uint8_t *in, size_t size)
+{
+    for (size_t i = 0; i < size; i++) {
+        out[i] = in[i];
+    }
+}
+
+// mike: HACK: for single translation unit crypto.c, there's already zero[128]
+// in monocypher.c, so leave this out!
+//static const uint8_t zero[8] = {0};
+
+void crypto_rng_init(crypto_rng_ctx *ctx, uint8_t random_seed[32])
+{
+    copy(ctx->pool, random_seed, 32);
+    ctx->idx = 512;
+    crypto_wipe(random_seed, 32);
+}
+
+void crypto_rng_read(crypto_rng_ctx *ctx, uint8_t *buf, size_t size)
+{
+    size_t pool_size = 512 - ctx->idx;
+    while (size > pool_size) {
+        copy(buf, ctx->pool + ctx->idx, pool_size);
+        crypto_chacha20(ctx->pool, 0, 512, ctx->pool, zero);
+        size     -= pool_size;
+        buf      += pool_size;
+        ctx->idx  = 32;
+        pool_size = 512 - 32;
+    }
+    copy(buf, ctx->pool + ctx->idx, size);
+    ctx->idx += size;
+
+    // Wipe used bytes ASAP (even if they'll be erased later)
+    crypto_wipe(ctx->pool + 32, ctx->idx - 32);
+}
+
+void crypto_rng_fork(crypto_rng_ctx *ctx, crypto_rng_ctx *child_ctx)
+{
+    uint8_t child_seed[32]; // wiped by crypto_rng_init;
+    crypto_rng_read(ctx, child_seed, 32);
+    crypto_rng_init(child_ctx, child_seed);
+}