circpad/prob_distr: Use crypto_fast_rng() instead of the old RNG.

changes/bug28636

@@ -0,0 +1,8 @@
+  o Minor bugfixes (circuit padding):
+    - The circuit padding subsystem does not schedule padding if dormant mode
+      is enabled. Fixes bug 28636; bugfix on 0.4.0.1-alpha.
+
+  o Minor feature (circuit padding):
+    - We now use a fast RNG when scheduling circuit padding. Part of ticket
+      28636.
+

src/core/or/circuitpadding.c

@@ -449,7 +449,8 @@ circpad_machine_sample_delay(circpad_machine_state_t *mi)
     histogram_total_tokens = state->histogram_total_tokens;
   }
 
-  bin_choice = crypto_rand_uint64(histogram_total_tokens);
+  bin_choice = crypto_fast_rng_get_uint64(get_thread_fast_rng(),
+                                          histogram_total_tokens);
 
   /* Skip all the initial zero bins */
   while (!histogram[curr_bin]) {
@@ -498,12 +499,12 @@ circpad_machine_sample_delay(circpad_machine_state_t *mi)
   bin_end = circpad_histogram_bin_to_usec(mi, curr_bin+1);
 
   /* Bin edges are monotonically increasing so this is a bug. Handle it. */
-  if (BUG(bin_start > bin_end)) {
+  if (BUG(bin_start >= bin_end)) {
     return bin_start;
   }
 
-  /* Sample randomly from within the bin width */
-  return (circpad_delay_t)crypto_rand_uint64_range(bin_start, bin_end);
+  return (circpad_delay_t)crypto_fast_rng_uint64_range(get_thread_fast_rng(),
+                                                       bin_start, bin_end);
 }
 
 /**

src/lib/crypt_ops/crypto_rand.h

@@ -66,6 +66,9 @@ void crypto_fast_rng_free_(crypto_fast_rng_t *);
 
 unsigned crypto_fast_rng_get_uint(crypto_fast_rng_t *rng, unsigned limit);
 uint64_t crypto_fast_rng_get_uint64(crypto_fast_rng_t *rng, uint64_t limit);
+uint32_t crypto_fast_rng_get_u32(crypto_fast_rng_t *rng);
+uint64_t crypto_fast_rng_uint64_range(crypto_fast_rng_t *rng,
+                                      uint64_t min, uint64_t max);
 double crypto_fast_rng_get_double(crypto_fast_rng_t *rng);
 
 /**

src/lib/crypt_ops/crypto_rand_numeric.c

@@ -155,7 +155,34 @@ crypto_fast_rng_get_uint64(crypto_fast_rng_t *rng, uint64_t limit)
 }
 
 /**
- * As crypto_rand_, but extract the result from a crypto_fast_rng_t.
+ * As crypto_rand_u32, but extract the result from a crypto_fast_rng_t.
+ */
+uint32_t
+crypto_fast_rng_get_u32(crypto_fast_rng_t *rng)
+{
+  uint32_t val;
+  crypto_fast_rng_getbytes(rng, (void*)&val, sizeof(val));
+  return val;
+}
+
+/**
+ * As crypto_rand_uint64_range(), but extract the result from a
+ * crypto_fast_rng_t.
+ */
+uint64_t
+crypto_fast_rng_uint64_range(crypto_fast_rng_t *rng,
+                             uint64_t min, uint64_t max)
+{
+  /* Handle corrupted input */
+  if (BUG(min >= max)) {
+    return min;
+  }
+
+  return min + crypto_fast_rng_get_uint64(rng, max - min);
+}
+
+/**
+ * As crypto_rand_get_double() but extract the result from a crypto_fast_rng_t.
  */
 double
 crypto_fast_rng_get_double(crypto_fast_rng_t *rng)
@@ -164,3 +191,4 @@ crypto_fast_rng_get_double(crypto_fast_rng_t *rng)
   crypto_fast_rng_getbytes(rng, (void*)&u, sizeof(u));
   return ((double)u) / UINT_MAX_AS_DOUBLE;
 }
+

src/lib/math/prob_distr.c

@@ -459,7 +459,7 @@ random_uniform_01(void)
    * system is broken.
    */
   z = 0;
-  while ((x = crypto_rand_u32()) == 0) {
+  while ((x = crypto_fast_rng_get_u32(get_thread_fast_rng())) == 0) {
     if (z >= 1088)
       /* Your bit sampler is broken.  Go home.  */
       return 0;
@@ -473,8 +473,8 @@ random_uniform_01(void)
    * occur only with measure zero in the uniform distribution on
    * [0, 1].
    */
-  hi = crypto_rand_u32() | UINT32_C(0x80000000);
-  lo = crypto_rand_u32() | UINT32_C(0x00000001);
+  hi = crypto_fast_rng_get_u32(get_thread_fast_rng()) | UINT32_C(0x80000000);
+  lo = crypto_fast_rng_get_u32(get_thread_fast_rng()) | UINT32_C(0x00000001);
 
   /* Round to nearest scaled significand in [2^63, 2^64].  */
   s = hi*(double)4294967296 + lo;
@@ -1437,7 +1437,7 @@ static double
 logistic_sample(const struct dist *dist)
 {
   const struct logistic *L = dist_to_const_logistic(dist);
-  uint32_t s = crypto_rand_u32();
+  uint32_t s = crypto_fast_rng_get_u32(get_thread_fast_rng());
   double t = random_uniform_01();
   double p0 = random_uniform_01();
 
@@ -1487,7 +1487,7 @@ static double
 log_logistic_sample(const struct dist *dist)
 {
   const struct log_logistic *LL = dist_to_const_log_logistic(dist);
-  uint32_t s = crypto_rand_u32();
+  uint32_t s = crypto_fast_rng_get_u32(get_thread_fast_rng());
   double p0 = random_uniform_01();
 
   return sample_log_logistic_scaleshape(s, p0, LL->alpha, LL->beta);
@@ -1536,7 +1536,7 @@ static double
 weibull_sample(const struct dist *dist)
 {
   const struct weibull *W = dist_to_const_weibull(dist);
-  uint32_t s = crypto_rand_u32();
+  uint32_t s = crypto_fast_rng_get_u32(get_thread_fast_rng());
   double p0 = random_uniform_01();
 
   return sample_weibull(s, p0, W->lambda, W->k);
@@ -1585,7 +1585,7 @@ static double
 genpareto_sample(const struct dist *dist)
 {
   const struct genpareto *GP = dist_to_const_genpareto(dist);
-  uint32_t s = crypto_rand_u32();
+  uint32_t s = crypto_fast_rng_get_u32(get_thread_fast_rng());
   double p0 = random_uniform_01();
 
   return sample_genpareto_locscale(s, p0, GP->mu, GP->sigma, GP->xi);
@@ -1634,7 +1634,7 @@ static double
 geometric_sample(const struct dist *dist)
 {
   const struct geometric *G = dist_to_const_geometric(dist);
-  uint32_t s = crypto_rand_u32();
+  uint32_t s = crypto_fast_rng_get_u32(get_thread_fast_rng());
   double p0 = random_uniform_01();
 
   return sample_geometric(s, p0, G->p);