Initial import.

src/rand/hmac_drbg.c

@@ -0,0 +1,157 @@
+/*
+ * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl.h */
+void
+br_hmac_drbg_init(br_hmac_drbg_context *ctx,
+	const br_hash_class *digest_class, const void *seed, size_t len)
+{
+	size_t hlen;
+
+	ctx->vtable = &br_hmac_drbg_vtable;
+	hlen = br_digest_size(digest_class);
+	memset(ctx->K, 0x00, hlen);
+	memset(ctx->V, 0x01, hlen);
+	ctx->digest_class = digest_class;
+	br_hmac_drbg_update(ctx, seed, len);
+}
+
+/* see bearssl.h */
+void
+br_hmac_drbg_generate(br_hmac_drbg_context *ctx, void *out, size_t len)
+{
+	const br_hash_class *dig;
+	br_hmac_key_context kc;
+	br_hmac_context hc;
+	size_t hlen;
+	unsigned char *buf;
+	unsigned char x;
+
+	dig = ctx->digest_class;
+	hlen = br_digest_size(dig);
+	br_hmac_key_init(&kc, dig, ctx->K, hlen);
+	buf = out;
+	while (len > 0) {
+		size_t clen;
+
+		br_hmac_init(&hc, &kc, 0);
+		br_hmac_update(&hc, ctx->V, hlen);
+		br_hmac_out(&hc, ctx->V);
+		clen = hlen;
+		if (clen > len) {
+			clen = len;
+		}
+		memcpy(buf, ctx->V, clen);
+		buf += clen;
+		len -= clen;
+	}
+
+	/*
+	 * To prepare the state for the next request, we should call
+	 * br_hmac_drbg_update() with an empty additional seed. However,
+	 * we already have an initialized HMAC context with the right
+	 * initial key, and we don't want to push another one on the
+	 * stack, so we inline that update() call here.
+	 */
+	br_hmac_init(&hc, &kc, 0);
+	br_hmac_update(&hc, ctx->V, hlen);
+	x = 0x00;
+	br_hmac_update(&hc, &x, 1);
+	br_hmac_out(&hc, ctx->K);
+	br_hmac_key_init(&kc, dig, ctx->K, hlen);
+	br_hmac_init(&hc, &kc, 0);
+	br_hmac_update(&hc, ctx->V, hlen);
+	br_hmac_out(&hc, ctx->V);
+}
+
+/* see bearssl.h */
+void
+br_hmac_drbg_update(br_hmac_drbg_context *ctx, const void *seed, size_t len)
+{
+	const br_hash_class *dig;
+	br_hmac_key_context kc;
+	br_hmac_context hc;
+	size_t hlen;
+	unsigned char x;
+
+	dig = ctx->digest_class;
+	hlen = br_digest_size(dig);
+
+	/*
+	 * 1. K = HMAC(K, V || 0x00 || seed)
+	 */
+	br_hmac_key_init(&kc, dig, ctx->K, hlen);
+	br_hmac_init(&hc, &kc, 0);
+	br_hmac_update(&hc, ctx->V, hlen);
+	x = 0x00;
+	br_hmac_update(&hc, &x, 1);
+	br_hmac_update(&hc, seed, len);
+	br_hmac_out(&hc, ctx->K);
+	br_hmac_key_init(&kc, dig, ctx->K, hlen);
+
+	/*
+	 * 2. V = HMAC(K, V)
+	 */
+	br_hmac_init(&hc, &kc, 0);
+	br_hmac_update(&hc, ctx->V, hlen);
+	br_hmac_out(&hc, ctx->V);
+
+	/*
+	 * 3. If the additional seed is empty, then stop here.
+	 */
+	if (len == 0) {
+		return;
+	}
+
+	/*
+	 * 4. K = HMAC(K, V || 0x01 || seed)
+	 */
+	br_hmac_init(&hc, &kc, 0);
+	br_hmac_update(&hc, ctx->V, hlen);
+	x = 0x01;
+	br_hmac_update(&hc, &x, 1);
+	br_hmac_update(&hc, seed, len);
+	br_hmac_out(&hc, ctx->K);
+	br_hmac_key_init(&kc, dig, ctx->K, hlen);
+
+	/*
+	 * 5. V = HMAC(K, V)
+	 */
+	br_hmac_init(&hc, &kc, 0);
+	br_hmac_update(&hc, ctx->V, hlen);
+	br_hmac_out(&hc, ctx->V);
+}
+
+/* see bearssl.h */
+const br_prng_class br_hmac_drbg_vtable = {
+	sizeof(br_hmac_drbg_context),
+	(void (*)(const br_prng_class **, const void *, const void *, size_t))
+		&br_hmac_drbg_init,
+	(void (*)(const br_prng_class **, void *, size_t))
+		&br_hmac_drbg_generate,
+	(void (*)(const br_prng_class **, const void *, size_t))
+		&br_hmac_drbg_update
+};