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

[BearSSL] / src / rand / sysrng.c

diff --git a/src/rand/sysrng.c b/src/rand/sysrng.c
new file mode 100644 (file)
index 0000000..3a10db9
--- /dev/null
+++ b/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;
+}