Provide RNG_STRONG quality in rdrand by forcing PRNG reseed after every sample

diff --git a/src/libstrongswan/plugins/rdrand/rdrand_plugin.c b/src/libstrongswan/plugins/rdrand/rdrand_plugin.c
index fc9c6202d52d5ba962a4114b57d2030823fbab35..4462c5e0e79b4e49d230212186faeb7dd2c5c36b 100644 (file)
--- a/src/libstrongswan/plugins/rdrand/rdrand_plugin.c
+++ b/src/libstrongswan/plugins/rdrand/rdrand_plugin.c
@@ -97,6 +97,7 @@ METHOD(plugin_t, get_features, int,
        static plugin_feature_t f[] = {
                PLUGIN_REGISTER(RNG, rdrand_rng_create),
                        PLUGIN_PROVIDE(RNG, RNG_WEAK),
+                       PLUGIN_PROVIDE(RNG, RNG_STRONG),
        };
        *features = f;
        return countof(f);

diff --git a/src/libstrongswan/plugins/rdrand/rdrand_rng.c b/src/libstrongswan/plugins/rdrand/rdrand_rng.c
index 64ce1250953c677b362ac993ec5445ab164a1c0b..6ad0da29c4dfd328ce03b830b232e760ec1e8428 100644 (file)
--- a/src/libstrongswan/plugins/rdrand/rdrand_rng.c
+++ b/src/libstrongswan/plugins/rdrand/rdrand_rng.c
@@ -38,6 +38,12 @@ struct private_rdrand_rng_t {
  */
 #define MAX_TRIES 16
 
+/**
+ * After how many bytes should we reseed for RNG_STRONG
+ * (must be a power of two >= 8)
+ */
+#define FORCE_RESEED 16
+
 /**
  * Get a two byte word using RDRAND
  */
@@ -121,6 +127,37 @@ static bool rdrand8(u_int8_t *out)
        return TRUE;
 }
 
+/**
+ * Enforce a DRNG reseed by reading 511 128-bit samples
+ */
+static bool reseed()
+{
+       int i;
+
+#ifdef __x86_64__
+       u_int64_t tmp;
+
+       for (i = 0; i < 511 * 16 / sizeof(u_int64_t); i++)
+       {
+               if (!rdrand64(&tmp))
+               {
+                       return FALSE;
+               }
+       }
+#else /* __i386__ */
+       u_int32_t tmp;
+
+       for (i = 0; i < 511 * 16 / sizeof(u_int32_t); i++)
+       {
+               if (!rdrand32(&tmp))
+               {
+                       return FALSE;
+               }
+       }
+#endif /* __x86_64__ / __i386__ */
+       return TRUE;
+}
+
 METHOD(rng_t, get_bytes, bool,
        private_rdrand_rng_t *this, size_t bytes, u_int8_t *buffer)
 {
@@ -128,6 +165,14 @@ METHOD(rng_t, get_bytes, bool,
 
        chunk = chunk_create(buffer, bytes);
 
+       if (this->quality == RNG_STRONG)
+       {
+               if (!reseed())
+               {
+                       return FALSE;
+               }
+       }
+
        /* align to 2 byte */
        if (chunk.len >= sizeof(u_int8_t))
        {
@@ -172,6 +217,13 @@ METHOD(rng_t, get_bytes, bool,
        /* fill with 8 byte words */
        while (chunk.len >= sizeof(u_int64_t))
        {
+               if (this->quality == RNG_STRONG && chunk.len % FORCE_RESEED)
+               {
+                       if (!reseed())
+                       {
+                               return FALSE;
+                       }
+               }
                if (!rdrand64((u_int64_t*)chunk.ptr))
                {
                        return FALSE;
@@ -194,6 +246,13 @@ METHOD(rng_t, get_bytes, bool,
        /* fill with 4 byte words */
        while (chunk.len >= sizeof(u_int32_t))
        {
+               if (this->quality == RNG_STRONG && chunk.len % FORCE_RESEED)
+               {
+                       if (!reseed())
+                       {
+                               return FALSE;
+                       }
+               }
                if (!rdrand32((u_int32_t*)chunk.ptr))
                {
                        return FALSE;
@@ -203,6 +262,14 @@ METHOD(rng_t, get_bytes, bool,
 
 #endif /* __x86_64__ / __i386__ */
 
+       if (this->quality == RNG_STRONG)
+       {
+               if (!reseed())
+               {
+                       return FALSE;
+               }
+       }
+
        /* append 2 byte word */
        if (chunk.len >= sizeof(u_int16_t))
        {
@@ -254,8 +321,8 @@ rdrand_rng_t *rdrand_rng_create(rng_quality_t quality)
        switch (quality)
        {
                case RNG_WEAK:
-                       break;
                case RNG_STRONG:
+                       break;
                case RNG_TRUE:
                default:
                        /* not yet */