Added seeder API. Also overhauled compile-time detection of features.

src/rand/sysrng.c

@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2017 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.
+ */
+
+#define BR_ENABLE_INTRINSICS   1
+#include "inner.h"
+
+#if BR_USE_URANDOM
+#include <sys/types.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#endif
+
+#if BR_USE_WIN32_RAND
+#include <windows.h>
+#include <wincrypt.h>
+#pragma comment(lib, "advapi32")
+#endif
+
+#if BR_RDRAND
+BR_TARGETS_X86_UP
+BR_TARGET("rdrnd")
+static int
+seeder_rdrand(const br_prng_class **ctx)
+{
+	unsigned char tmp[32];
+	size_t u;
+
+	for (u = 0; u < sizeof tmp; u += sizeof(uint32_t)) {
+		int j;
+		uint32_t x;
+
+		/*
+		 * We use the 32-bit intrinsic so that code is compatible
+		 * with both 32-bit and 64-bit architectures.
+		 *
+		 * Intel recommends trying at least 10 times in case of
+		 * failure.
+		 */
+		for (j = 0; j < 10; j ++) {
+			if (_rdrand32_step(&x)) {
+				goto next_word;
+			}
+		}
+		return 0;
+	next_word:
+		br_enc32le(tmp + u, x);
+	}
+	(*ctx)->update(ctx, tmp, sizeof tmp);
+	return 1;
+}
+BR_TARGETS_X86_DOWN
+
+static int
+rdrand_supported(void)
+{
+	/*
+	 * The RDRND support is bit 30 of ECX, as returned by CPUID.
+	 */
+	return br_cpuid(0, 0, 0x40000000, 0);
+}
+
+#endif
+
+#if BR_USE_URANDOM
+static int
+seeder_urandom(const br_prng_class **ctx)
+{
+	int f;
+
+	f = open("/dev/urandom", O_RDONLY);
+	if (f >= 0) {
+		unsigned char tmp[32];
+		size_t u;
+
+		for (u = 0; u < sizeof tmp;) {
+			ssize_t len;
+
+			len = read(f, tmp + u, (sizeof tmp) - u);
+			if (len < 0) {
+				if (errno == EINTR) {
+					continue;
+				}
+				break;
+			}
+			u += (size_t)len;
+		}
+		close(f);
+		if (u == sizeof tmp) {
+			(*ctx)->update(ctx, tmp, sizeof tmp);
+			return 1;
+		}
+	}
+	return 0;
+}
+#endif
+
+#if BR_USE_WIN32_RAND
+static int
+seeder_win32(const br_prng_class **ctx)
+{
+	HCRYPTPROV hp;
+
+	if (CryptAcquireContext(&hp, 0, 0, PROV_RSA_FULL,
+		CRYPT_VERIFYCONTEXT | CRYPT_SILENT))
+	{
+		BYTE buf[32];
+		BOOL r;
+
+		r = CryptGenRandom(hp, sizeof buf, buf);
+		CryptReleaseContext(hp, 0);
+		if (r) {
+			(*ctx)->update(ctx, buf, sizeof buf);
+			return 1;
+		}
+	}
+	return 0;
+}
+#endif
+
+/* see bearssl_rand.h.h */
+br_prng_seeder
+br_prng_seeder_system(const char **name)
+{
+#if BR_RDRAND
+	if (rdrand_supported()) {
+		if (name != NULL) {
+			*name = "rdrand";
+		}
+		return &seeder_rdrand;
+	}
+#endif
+#if BR_USE_URANDOM
+	if (name != NULL) {
+		*name = "urandom";
+	}
+	return &seeder_urandom;
+#elif BR_USE_WIN32_RAND
+	if (name != NULL) {
+		*name = "win32";
+	}
+	return &seeder_win32;
+#endif
+	if (name != NULL) {
+		*name = "none";
+	}
+	return 0;
+}