Merge branch 'tor-github/pr/702'

8 files changed, 717 insertions, 113 deletions

diff --git a/src/lib/crypt_ops/crypto_rand.c b/src/lib/crypt_ops/crypto_rand.c
index e377054219..0b1cb96c1b 100644
--- a/src/lib/crypt_ops/crypto_rand.c
+++ b/src/lib/crypt_ops/crypto_rand.c
@@ -11,7 +11,6 @@
  * number generators, and working with randomness.
  **/
 
-#ifndef CRYPTO_RAND_PRIVATE
 #define CRYPTO_RAND_PRIVATE
 
 #include "lib/crypt_ops/crypto_rand.h"
@@ -541,114 +540,6 @@ crypto_rand_u32(void)
 }
 
 /**
- * Return a pseudorandom integer, chosen uniformly from the values
- * between 0 and <b>max</b>-1 inclusive.  <b>max</b> must be between 1 and
- * INT_MAX+1, inclusive.
- */
-int
-crypto_rand_int(unsigned int max)
-{
-  unsigned int val;
-  unsigned int cutoff;
-  tor_assert(max <= ((unsigned int)INT_MAX)+1);
-  tor_assert(max > 0); /* don't div by 0 */
-
-  /* We ignore any values that are >= 'cutoff,' to avoid biasing the
-   * distribution with clipping at the upper end of unsigned int's
-   * range.
-   */
-  cutoff = UINT_MAX - (UINT_MAX%max);
-  while (1) {
-    crypto_rand((char*)&val, sizeof(val));
-    if (val < cutoff)
-      return val % max;
-  }
-}
-
-/**
- * Return a pseudorandom integer, chosen uniformly from the values i such
- * that min <= i < max.
- *
- * <b>min</b> MUST be in range [0, <b>max</b>).
- * <b>max</b> MUST be in range (min, INT_MAX].
- **/
-int
-crypto_rand_int_range(unsigned int min, unsigned int max)
-{
-  tor_assert(min < max);
-  tor_assert(max <= INT_MAX);
-
-  /* The overflow is avoided here because crypto_rand_int() returns a value
-   * between 0 and (max - min) inclusive. */
-  return min + crypto_rand_int(max - min);
-}
-
-/**
- * As crypto_rand_int_range, but supports uint64_t.
- **/
-uint64_t
-crypto_rand_uint64_range(uint64_t min, uint64_t max)
-{
-  tor_assert(min < max);
-  return min + crypto_rand_uint64(max - min);
-}
-
-/**
- * As crypto_rand_int_range, but supports time_t.
- **/
-time_t
-crypto_rand_time_range(time_t min, time_t max)
-{
-  tor_assert(min < max);
-  return min + (time_t)crypto_rand_uint64(max - min);
-}
-
-/**
- * Return a pseudorandom 64-bit integer, chosen uniformly from the values
- * between 0 and <b>max</b>-1 inclusive.
- **/
-uint64_t
-crypto_rand_uint64(uint64_t max)
-{
-  uint64_t val;
-  uint64_t cutoff;
-  tor_assert(max < UINT64_MAX);
-  tor_assert(max > 0); /* don't div by 0 */
-
-  /* We ignore any values that are >= 'cutoff,' to avoid biasing the
-   * distribution with clipping at the upper end of unsigned int's
-   * range.
-   */
-  cutoff = UINT64_MAX - (UINT64_MAX%max);
-  while (1) {
-    crypto_rand((char*)&val, sizeof(val));
-    if (val < cutoff)
-      return val % max;
-  }
-}
-
-/**
- * Return a pseudorandom double d, chosen uniformly from the range
- * 0.0 <= d < 1.0.
- **/
-double
-crypto_rand_double(void)
-{
-  /* We just use an unsigned int here; we don't really care about getting
-   * more than 32 bits of resolution */
-  unsigned int u;
-  crypto_rand((char*)&u, sizeof(u));
-#if SIZEOF_INT == 4
-#define UINT_MAX_AS_DOUBLE 4294967296.0
-#elif SIZEOF_INT == 8
-#define UINT_MAX_AS_DOUBLE 1.8446744073709552e+19
-#else
-#error SIZEOF_INT is neither 4 nor 8
-#endif /* SIZEOF_INT == 4 || ... */
-  return ((double)u) / UINT_MAX_AS_DOUBLE;
-}
-
-/**
  * Generate and return a new random hostname starting with <b>prefix</b>,
  * ending with <b>suffix</b>, and containing no fewer than
  * <b>min_rand_len</b> and no more than <b>max_rand_len</b> random base32
@@ -738,5 +629,3 @@ crypto_force_rand_ssleay(void)
 #endif
   return 0;
 }
-
-#endif /* !defined(CRYPTO_RAND_PRIVATE) */
diff --git a/src/lib/crypt_ops/crypto_rand.h b/src/lib/crypt_ops/crypto_rand.h
index cc2762842a..8a81a4acdc 100644
--- a/src/lib/crypt_ops/crypto_rand.h
+++ b/src/lib/crypt_ops/crypto_rand.h
@@ -16,6 +16,7 @@
 #include "lib/cc/compat_compiler.h"
 #include "lib/cc/torint.h"
 #include "lib/testsupport/testsupport.h"
+#include "lib/malloc/malloc.h"
 
 /* random numbers */
 int crypto_seed_rng(void) ATTR_WUR;
@@ -24,6 +25,7 @@ void crypto_rand_unmocked(char *to, size_t n);
 void crypto_strongest_rand(uint8_t *out, size_t out_len);
 MOCK_DECL(void,crypto_strongest_rand_,(uint8_t *out, size_t out_len));
 int crypto_rand_int(unsigned int max);
+unsigned crypto_rand_uint(unsigned limit);
 int crypto_rand_int_range(unsigned int min, unsigned int max);
 uint64_t crypto_rand_uint64_range(uint64_t min, uint64_t max);
 time_t crypto_rand_time_range(time_t min, time_t max);
@@ -41,6 +43,36 @@ void *smartlist_choose(const struct smartlist_t *sl);
 void smartlist_shuffle(struct smartlist_t *sl);
 int crypto_force_rand_ssleay(void);
 
+/**
+ * A fast PRNG, for use when the PRNG provided by our crypto library isn't
+ * fast enough.  This one _should_ be cryptographically strong, but
+ * has seen less auditing than the PRNGs in OpenSSL and NSS.  Use with
+ * caution.
+ *
+ * Note that this object is NOT thread-safe.  If you need a thread-safe
+ * prng, use crypto_rand(), or wrap this in a mutex.
+ **/
+typedef struct crypto_fast_rng_t crypto_fast_rng_t;
+/**
+ * Number of bytes used to seed a crypto_rand_fast_t.
+ **/
+crypto_fast_rng_t *crypto_fast_rng_new(void);
+#define CRYPTO_FAST_RNG_SEED_LEN 48
+crypto_fast_rng_t *crypto_fast_rng_new_from_seed(const uint8_t *seed);
+void crypto_fast_rng_getbytes(crypto_fast_rng_t *rng, uint8_t *out, size_t n);
+void crypto_fast_rng_free_(crypto_fast_rng_t *);
+#define crypto_fast_rng_free(c)                                 \
+  FREE_AND_NULL(crypto_fast_rng_t, crypto_fast_rng_free_, (c))
+
+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);
+double crypto_fast_rng_get_double(crypto_fast_rng_t *rng);
+
+#if defined(TOR_UNIT_TESTS)
+/* Used for white-box testing */
+size_t crypto_fast_rng_get_bytes_used_per_stream(void);
+#endif
+
 #ifdef CRYPTO_RAND_PRIVATE
 
 STATIC int crypto_strongest_rand_raw(uint8_t *out, size_t out_len);
diff --git a/src/lib/crypt_ops/crypto_rand_fast.c b/src/lib/crypt_ops/crypto_rand_fast.c
new file mode 100644
index 0000000000..34e763bf51
--- /dev/null
+++ b/src/lib/crypt_ops/crypto_rand_fast.c
@@ -0,0 +1,263 @@
+/* Copyright (c) 2001, Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file crypto_rand_fast.c
+ *
+ * \brief A fast strong PRNG for use when our underlying cryptographic
+ *   library's PRNG isn't fast enough.
+ **/
+
+/* This library is currently implemented to use the same implementation
+ * technique as libottery, using AES-CTR-256 as our underlying stream cipher.
+ * It's backtracking-resistant immediately, and prediction-resistant after
+ * a while.
+ *
+ * Here's how it works:
+ *
+ * We generate pseudorandom bytes using AES-CTR-256.  We generate BUFLEN bytes
+ * at a time.  When we do this, we keep the first SEED_LEN bytes as the key
+ * and the IV for our next invocation of AES_CTR, and yield the remaining
+ * BUFLEN - SEED_LEN bytes to the user as they invoke the PRNG.  As we yield
+ * bytes to the user, we clear them from the buffer.
+ *
+ * After we have refilled the buffer RESEED_AFTER times, we mix in an
+ * additional SEED_LEN bytes from our strong PRNG into the seed.
+ *
+ * If the user ever asks for a huge number of bytes at once, we pull SEED_LEN
+ * bytes from the PRNG and use them with our stream cipher to fill the user's
+ * request.
+ */
+
+#define CRYPTO_RAND_FAST_PRIVATE
+
+#include "lib/crypt_ops/crypto_rand.h"
+#include "lib/crypt_ops/crypto_cipher.h"
+#include "lib/crypt_ops/crypto_digest.h"
+#include "lib/crypt_ops/crypto_util.h"
+#include "lib/intmath/cmp.h"
+#include "lib/cc/ctassert.h"
+#include "lib/malloc/map_anon.h"
+
+#include "lib/log/util_bug.h"
+
+#include <string.h>
+
+/* Alias for CRYPTO_FAST_RNG_SEED_LEN to make our code shorter.
+ */
+#define SEED_LEN (CRYPTO_FAST_RNG_SEED_LEN)
+
+/* The amount of space that we mmap for a crypto_fast_rng_t.
+ */
+#define MAPLEN 4096
+
+/* The number of random bytes that we can yield to the user after each
+ * time we fill a crypto_fast_rng_t's buffer.
+ */
+#define BUFLEN (MAPLEN - 2*sizeof(uint16_t) - SEED_LEN)
+
+/* The number of buffer refills after which we should fetch more
+ * entropy from crypto_strongest_rand().
+ */
+#define RESEED_AFTER 16
+
+/* The length of the stream cipher key we will use for the PRNG, in bytes.
+ */
+#define KEY_LEN (CRYPTO_FAST_RNG_SEED_LEN - CIPHER_IV_LEN)
+/* The length of the stream cipher key we will use for the PRNG, in bits.
+ */
+#define KEY_BITS (KEY_LEN * 8)
+
+/* Make sure that we have a key length we can actually use with AES. */
+CTASSERT(KEY_BITS == 128 || KEY_BITS == 192 || KEY_BITS == 256);
+
+struct crypto_fast_rng_t {
+  /** How many more fills does this buffer have before we should mix
+   * in the output of crypto_rand()? */
+  uint16_t n_till_reseed;
+  /** How many bytes are remaining in cbuf.bytes? */
+  uint16_t bytes_left;
+  struct cbuf {
+    /** The seed (key and IV) that we will use the next time that we refill
+     * cbuf. */
+    uint8_t seed[SEED_LEN];
+    /**
+     * Bytes that we are yielding to the user.  The next byte to be
+     * yielded is at bytes[BUFLEN-bytes_left]; all other bytes in this
+     * array are set to zero.
+     */
+    uint8_t bytes[BUFLEN];
+  } buf;
+};
+
+/* alignof(uint8_t) should be 1, so there shouldn't be any padding in cbuf.
+ */
+CTASSERT(sizeof(struct cbuf) == BUFLEN+SEED_LEN);
+/* We're trying to fit all of the RNG state into a nice mmapable chunk.
+ */
+CTASSERT(sizeof(crypto_fast_rng_t) <= MAPLEN);
+
+/**
+ * Initialize and return a new fast PRNG, using a strong random seed.
+ *
+ * Note that this object is NOT thread-safe.  If you need a thread-safe
+ * prng, use crypto_rand(), or wrap this in a mutex.
+ **/
+crypto_fast_rng_t *
+crypto_fast_rng_new(void)
+{
+  uint8_t seed[SEED_LEN];
+  crypto_strongest_rand(seed, sizeof(seed));
+  crypto_fast_rng_t *result = crypto_fast_rng_new_from_seed(seed);
+  memwipe(seed, 0, sizeof(seed));
+  return result;
+}
+
+/**
+ * Initialize and return a new fast PRNG, using a seed value specified
+ * in <b>seed</b>.  This value must be CRYPTO_FAST_RNG_SEED_LEN bytes
+ * long.
+ *
+ * Note that this object is NOT thread-safe.  If you need a thread-safe
+ * prng, use crypto_rand(), or wrap this in a mutex.
+ **/
+crypto_fast_rng_t *
+crypto_fast_rng_new_from_seed(const uint8_t *seed)
+{
+  /* We try to allocate this object as securely as we can, to avoid
+   * having it get dumped, swapped, or shared after fork.
+   */
+  crypto_fast_rng_t *result = tor_mmap_anonymous(sizeof(*result),
+                                ANONMAP_PRIVATE | ANONMAP_NOINHERIT);
+
+  memcpy(result->buf.seed, seed, SEED_LEN);
+  /* Causes an immediate refill once the user asks for data. */
+  result->bytes_left = 0;
+  result->n_till_reseed = RESEED_AFTER;
+  return result;
+}
+
+/**
+ * Helper: create a crypto_cipher_t object from SEED_LEN bytes of
+ * input.  The first KEY_LEN bytes are used as the stream cipher's key,
+ * and the remaining CIPHER_IV_LEN bytes are used as its IV.
+ **/
+static inline crypto_cipher_t *
+cipher_from_seed(const uint8_t *seed)
+{
+  return crypto_cipher_new_with_iv_and_bits(seed, seed+KEY_LEN, KEY_BITS);
+}
+
+/**
+ * Helper: refill the seed bytes and output buffer of <b>rng</b>, using
+ * the input seed bytes as input (key and IV) for the stream cipher.
+ *
+ * If the n_till_reseed counter has reached zero, mix more random bytes into
+ * the seed before refilling the buffer.
+ **/
+static void
+crypto_fast_rng_refill(crypto_fast_rng_t *rng)
+{
+  if (rng->n_till_reseed-- == 0) {
+    /* It's time to reseed the RNG.  We'll do this by using our XOF to mix the
+     * old value for the seed with some additional bytes from
+     * crypto_strongest_rand(). */
+    crypto_xof_t *xof = crypto_xof_new();
+    crypto_xof_add_bytes(xof, rng->buf.seed, SEED_LEN);
+    {
+      uint8_t seedbuf[SEED_LEN];
+      crypto_strongest_rand(seedbuf, SEED_LEN);
+      crypto_xof_add_bytes(xof, seedbuf, SEED_LEN);
+      memwipe(seedbuf, 0, SEED_LEN);
+    }
+    crypto_xof_squeeze_bytes(xof, rng->buf.seed, SEED_LEN);
+    crypto_xof_free(xof);
+
+    rng->n_till_reseed = RESEED_AFTER;
+  }
+  /* Now fill rng->buf with output from our stream cipher, initialized from
+   * that seed value. */
+  crypto_cipher_t *c = cipher_from_seed(rng->buf.seed);
+  memset(&rng->buf, 0, sizeof(rng->buf));
+  crypto_cipher_crypt_inplace(c, (char*)&rng->buf, sizeof(rng->buf));
+  crypto_cipher_free(c);
+
+  rng->bytes_left = sizeof(rng->buf.bytes);
+}
+
+/**
+ * Release all storage held by <b>rng</b>.
+ **/
+void
+crypto_fast_rng_free_(crypto_fast_rng_t *rng)
+{
+  if (!rng)
+    return;
+  memwipe(rng, 0, sizeof(*rng));
+  tor_munmap_anonymous(rng, sizeof(*rng));
+}
+
+/**
+ * Helper: extract bytes from the PRNG, refilling it as necessary. Does not
+ * optimize the case when the user has asked for a huge output.
+ **/
+static void
+crypto_fast_rng_getbytes_impl(crypto_fast_rng_t *rng, uint8_t *out,
+                              const size_t n)
+{
+  size_t bytes_to_yield = n;
+
+  while (bytes_to_yield) {
+    if (rng->bytes_left == 0)
+      crypto_fast_rng_refill(rng);
+
+    const size_t to_copy = MIN(rng->bytes_left, bytes_to_yield);
+
+    tor_assert(sizeof(rng->buf.bytes) >= rng->bytes_left);
+    uint8_t *copy_from = rng->buf.bytes +
+      (sizeof(rng->buf.bytes) - rng->bytes_left);
+    memcpy(out, copy_from, to_copy);
+    memset(copy_from, 0, to_copy);
+
+    out += to_copy;
+    bytes_to_yield -= to_copy;
+    rng->bytes_left -= to_copy;
+  }
+}
+
+/**
+ * Extract <b>n</b> bytes from <b>rng</b> into the buffer at <b>out</b>.
+ **/
+void
+crypto_fast_rng_getbytes(crypto_fast_rng_t *rng, uint8_t *out, size_t n)
+{
+  if (PREDICT_UNLIKELY(n > BUFLEN)) {
+    /* The user has asked for a lot of output; generate it from a stream
+     * cipher seeded by the PRNG rather than by pulling it out of the PRNG
+     * directly.
+     */
+    uint8_t seed[SEED_LEN];
+    crypto_fast_rng_getbytes_impl(rng, seed, SEED_LEN);
+    crypto_cipher_t *c = cipher_from_seed(seed);
+    memset(out, 0, n);
+    crypto_cipher_crypt_inplace(c, (char*)out, n);
+    crypto_cipher_free(c);
+    memwipe(seed, 0, sizeof(seed));
+    return;
+  }
+
+  crypto_fast_rng_getbytes_impl(rng, out, n);
+}
+
+#if defined(TOR_UNIT_TESTS)
+/** for white-box testing: return the number of bytes that are returned from
+ * the user for each invocation of the stream cipher in this RNG. */
+size_t
+crypto_fast_rng_get_bytes_used_per_stream(void)
+{
+  return BUFLEN;
+}
+#endif
diff --git a/src/lib/crypt_ops/crypto_rand_numeric.c b/src/lib/crypt_ops/crypto_rand_numeric.c
new file mode 100644
index 0000000000..d02c5cdcfa
--- /dev/null
+++ b/src/lib/crypt_ops/crypto_rand_numeric.c
@@ -0,0 +1,166 @@
+/**
+ * \file crypto_rand_numeric.c
+ *
+ * \brief Functions for retrieving uniformly distributed numbers
+ *   from our PRNGs.
+ **/
+
+#include "lib/crypt_ops/crypto_rand.h"
+#include "lib/log/util_bug.h"
+
+/**
+ * Implementation macro: yields code that returns a uniform unbiased
+ * random number between 0 and limit.  "type" is the type of the number to
+ * return; "maxval" is the largest possible value of "type"; and "fill_stmt"
+ * is a code snippet that fills an object named "val" with random bits.
+ **/
+#define IMPLEMENT_RAND_UNSIGNED(type, maxval, limit, fill_stmt)         \
+  do {                                                                  \
+    type val;                                                           \
+    type cutoff;                                                        \
+    tor_assert((limit) > 0);                                            \
+                                                                        \
+    /* We ignore any values that are >= 'cutoff,' to avoid biasing */   \
+    /* the distribution with clipping at the upper end of the type's */ \
+    /* range. */                                                        \
+    cutoff = (maxval) - ((maxval)%(limit));                             \
+    while (1) {                                                         \
+      fill_stmt;                                                        \
+      if (val < cutoff)                                                 \
+        return val % (limit);                                           \
+    }                                                                   \
+  } while (0)
+
+/**
+ * Return a pseudorandom integer chosen uniformly from the values between 0
+ * and <b>limit</b>-1 inclusive. limit must be strictly between 0 and
+ * UINT_MAX. */
+unsigned
+crypto_rand_uint(unsigned limit)
+{
+  tor_assert(limit < UINT_MAX);
+  IMPLEMENT_RAND_UNSIGNED(unsigned, UINT_MAX, limit,
+                          crypto_rand((char*)&val, sizeof(val)));
+}
+
+/**
+ * Return a pseudorandom integer, chosen uniformly from the values
+ * between 0 and <b>max</b>-1 inclusive.  <b>max</b> must be between 1 and
+ * INT_MAX+1, inclusive.
+ */
+int
+crypto_rand_int(unsigned int max)
+{
+  /* We can't use IMPLEMENT_RAND_UNSIGNED directly, since we're trying
+   * to return a signed type. Instead we make sure that the range is
+   * reasonable for a nonnegative int, use crypto_rand_uint(), and cast.
+   */
+  tor_assert(max <= ((unsigned int)INT_MAX)+1);
+
+  return (int)crypto_rand_uint(max);
+}
+
+/**
+ * Return a pseudorandom integer, chosen uniformly from the values i such
+ * that min <= i < max.
+ *
+ * <b>min</b> MUST be in range [0, <b>max</b>).
+ * <b>max</b> MUST be in range (min, INT_MAX].
+ **/
+int
+crypto_rand_int_range(unsigned int min, unsigned int max)
+{
+  tor_assert(min < max);
+  tor_assert(max <= INT_MAX);
+
+  /* The overflow is avoided here because crypto_rand_int() returns a value
+   * between 0 and (max - min) inclusive. */
+  return min + crypto_rand_int(max - min);
+}
+
+/**
+ * As crypto_rand_int_range, but supports uint64_t.
+ **/
+uint64_t
+crypto_rand_uint64_range(uint64_t min, uint64_t max)
+{
+  tor_assert(min < max);
+  return min + crypto_rand_uint64(max - min);
+}
+
+/**
+ * As crypto_rand_int_range, but supports time_t.
+ **/
+time_t
+crypto_rand_time_range(time_t min, time_t max)
+{
+  tor_assert(min < max);
+  return min + (time_t)crypto_rand_uint64(max - min);
+}
+
+/**
+ * Return a pseudorandom 64-bit integer, chosen uniformly from the values
+ * between 0 and <b>max</b>-1 inclusive.
+ **/
+uint64_t
+crypto_rand_uint64(uint64_t max)
+{
+  tor_assert(max < UINT64_MAX);
+  IMPLEMENT_RAND_UNSIGNED(uint64_t, UINT64_MAX, max,
+                          crypto_rand((char*)&val, sizeof(val)));
+}
+
+#if SIZEOF_INT == 4
+#define UINT_MAX_AS_DOUBLE 4294967296.0
+#elif SIZEOF_INT == 8
+#define UINT_MAX_AS_DOUBLE 1.8446744073709552e+19
+#else
+#error SIZEOF_INT is neither 4 nor 8
+#endif /* SIZEOF_INT == 4 || ... */
+
+/**
+ * Return a pseudorandom double d, chosen uniformly from the range
+ * 0.0 <= d < 1.0.
+ **/
+double
+crypto_rand_double(void)
+{
+  /* We just use an unsigned int here; we don't really care about getting
+   * more than 32 bits of resolution */
+  unsigned int u;
+  crypto_rand((char*)&u, sizeof(u));
+  return ((double)u) / UINT_MAX_AS_DOUBLE;
+}
+
+/**
+ * As crypto_rand_uint, but extract the result from a crypto_fast_rng_t
+ */
+unsigned
+crypto_fast_rng_get_uint(crypto_fast_rng_t *rng, unsigned limit)
+{
+  tor_assert(limit < UINT_MAX);
+  IMPLEMENT_RAND_UNSIGNED(unsigned, UINT_MAX, limit,
+                  crypto_fast_rng_getbytes(rng, (void*)&val, sizeof(val)));
+}
+
+/**
+ * As crypto_rand_uint64, but extract the result from a crypto_fast_rng_t.
+ */
+uint64_t
+crypto_fast_rng_get_uint64(crypto_fast_rng_t *rng, uint64_t limit)
+{
+  tor_assert(limit < UINT64_MAX);
+  IMPLEMENT_RAND_UNSIGNED(uint64_t, UINT64_MAX, limit,
+                  crypto_fast_rng_getbytes(rng, (void*)&val, sizeof(val)));
+}
+
+/**
+ * As crypto_rand_, but extract the result from a crypto_fast_rng_t.
+ */
+double
+crypto_fast_rng_get_double(crypto_fast_rng_t *rng)
+{
+  unsigned int u;
+  crypto_fast_rng_getbytes(rng, (void*)&u, sizeof(u));
+  return ((double)u) / UINT_MAX_AS_DOUBLE;
+}
diff --git a/src/lib/crypt_ops/include.am b/src/lib/crypt_ops/include.am
index d0ccc13bff..4730440143 100644
--- a/src/lib/crypt_ops/include.am
+++ b/src/lib/crypt_ops/include.am
@@ -17,6 +17,8 @@ src_lib_libtor_crypt_ops_a_SOURCES =			\
 	src/lib/crypt_ops/crypto_ope.c          	\
 	src/lib/crypt_ops/crypto_pwbox.c		\
 	src/lib/crypt_ops/crypto_rand.c			\
+	src/lib/crypt_ops/crypto_rand_fast.c		\
+	src/lib/crypt_ops/crypto_rand_numeric.c		\
 	src/lib/crypt_ops/crypto_rsa.c			\
 	src/lib/crypt_ops/crypto_s2k.c			\
 	src/lib/crypt_ops/crypto_util.c                 \
diff --git a/src/lib/malloc/include.am b/src/lib/malloc/include.am
index 502cc1c6b7..95d96168e1 100644
--- a/src/lib/malloc/include.am
+++ b/src/lib/malloc/include.am
@@ -6,7 +6,8 @@ noinst_LIBRARIES += src/lib/libtor-malloc-testing.a
 endif
 
 src_lib_libtor_malloc_a_SOURCES =			\
-	src/lib/malloc/malloc.c
+	src/lib/malloc/malloc.c				\
+	src/lib/malloc/map_anon.c
 
 if USE_OPENBSD_MALLOC
 src_lib_libtor_malloc_a_SOURCES += src/ext/OpenBSD_malloc_Linux.c
@@ -18,4 +19,5 @@ src_lib_libtor_malloc_testing_a_CPPFLAGS = $(AM_CPPFLAGS) $(TEST_CPPFLAGS)
 src_lib_libtor_malloc_testing_a_CFLAGS = $(AM_CFLAGS) $(TEST_CFLAGS)
 
 noinst_HEADERS +=					\
-	src/lib/malloc/malloc.h
+	src/lib/malloc/malloc.h				\
+	src/lib/malloc/map_anon.h
diff --git a/src/lib/malloc/map_anon.c b/src/lib/malloc/map_anon.c
new file mode 100644
index 0000000000..2fc6e89ea2
--- /dev/null
+++ b/src/lib/malloc/map_anon.c
@@ -0,0 +1,213 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file map_anon.c
+ * \brief Manage anonymous mappings.
+ **/
+
+#include "orconfig.h"
+#include "lib/malloc/map_anon.h"
+#include "lib/malloc/malloc.h"
+#include "lib/err/torerr.h"
+
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+#ifdef HAVE_SYS_TYPES_H
+#include <sys/types.h>
+#endif
+#ifdef HAVE_MACH_VM_INHERIT_H
+#include <mach/vm_inherit.h>
+#endif
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+/**
+ * Macro to get the high bytes of a size_t, if there are high bytes.
+ * Windows needs this; other operating systems define a size_t that does
+ * what it should.
+ */
+#if SIZEOF_SIZE_T > 4
+#define HIGH_SIZE_T_BYTES(sz) ((sz) >> 32)
+#else
+#define HIGH_SIZE_T_BYTES(sz) (0)
+#endif
+
+/* Here we define a MINHERIT macro that is minherit() or madvise(), depending
+ * on what we actually want.
+ *
+ * If there's a flag that sets pages to zero after fork, we define FLAG_ZERO
+ * to be that flag.  If there's a flag unmaps pages after fork, we define
+ * FLAG_NOINHERIT to be that flag.
+ */
+#if defined(HAVE_MINHERIT)
+#define MINHERIT minherit
+
+#ifdef INHERIT_ZERO
+#define FLAG_ZERO INHERIT_ZERO
+#endif
+#ifdef INHERIT_NONE
+#define FLAG_NOINHERIT INHERIT_NONE
+#elif defined(VM_INHERIT_NONE)
+#define FLAG_NOINHERIT VM_INHERIT_NONE
+#endif
+
+#elif defined(HAVE_MADVISE)
+
+#define MINHERIT madvise
+
+#ifdef MADV_WIPEONFORK
+#define FLAG_ZERO MADV_WIPEONFORK
+#endif
+#ifdef MADV_DONTFORK
+#define FLAG_NOINHERIT MADV_DONTFORK
+#endif
+
+#endif
+
+/**
+ * Helper: try to prevent the <b>sz</b> bytes at <b>mem</b> from being swapped
+ * to disk.  Return 0 on success or if the facility is not available on this
+ * OS; return -1 on failure.
+ */
+static int
+lock_mem(void *mem, size_t sz)
+{
+#ifdef _WIN32
+  return VirtualLock(mem, sz) ? 0 : -1;
+#elif defined(HAVE_MLOCK)
+  return mlock(mem, sz);
+#else
+  (void) mem;
+  (void) sz;
+
+  return 0;
+#endif
+}
+
+/**
+ * Helper: try to prevent the <b>sz</b> bytes at <b>mem</b> from appearing in
+ * a core dump.  Return 0 on success or if the facility is not available on
+ * this OS; return -1 on failure.
+ */
+static int
+nodump_mem(void *mem, size_t sz)
+{
+#if defined(MADV_DONTDUMP)
+  return madvise(mem, sz, MADV_DONTDUMP);
+#else
+  (void) mem;
+  (void) sz;
+  return 0;
+#endif
+}
+
+/**
+ * Helper: try to prevent the <b>sz</b> bytes at <b>mem</b> from being
+ * accessible in child processes -- ideally by having them set to 0 after a
+ * fork, and if that doesn't work, by having them unmapped after a fork.
+ * Return 0 on success or if the facility is not available on this OS; return
+ * -1 on failure.
+ */
+static int
+noinherit_mem(void *mem, size_t sz)
+{
+#ifdef FLAG_ZERO
+  int r = MINHERIT(mem, sz, FLAG_ZERO);
+  if (r == 0)
+    return 0;
+#endif
+#ifdef FLAG_NOINHERIT
+  return MINHERIT(mem, sz, FLAG_NOINHERIT);
+#else
+  (void)mem;
+  (void)sz;
+  return 0;
+#endif
+}
+
+/**
+ * Return a new anonymous memory mapping that holds <b>sz</b> bytes.
+ *
+ * Memory mappings are unlike the results from malloc() in that they are
+ * handled separately by the operating system, and as such can have different
+ * kernel-level flags set on them.
+ *
+ * The "flags" argument may be zero or more of ANONMAP_PRIVATE and
+ * ANONMAP_NOINHERIT.
+ *
+ * Memory returned from this function must be released with
+ * tor_munmap_anonymous().
+ *
+ * [Note: OS people use the word "anonymous" here to mean that the memory
+ * isn't associated with any file. This has *nothing* to do with the kind of
+ * anonymity that Tor is trying to provide.]
+ */
+void *
+tor_mmap_anonymous(size_t sz, unsigned flags)
+{
+  void *ptr;
+#if defined(_WIN32)
+  HANDLE mapping = CreateFileMapping(INVALID_HANDLE_VALUE,
+                                     NULL, /*attributes*/
+                                     PAGE_READWRITE,
+                                     HIGH_SIZE_T_BYTES(sz),
+                                     sz & 0xffffffff,
+                                     NULL /* name */);
+  raw_assert(mapping != NULL);
+  ptr = MapViewOfFile(mapping, FILE_MAP_WRITE,
+                      0, 0, /* Offset */
+                      0 /* Extend to end of mapping */);
+  raw_assert(ptr);
+  CloseHandle(mapping); /* mapped view holds a reference */
+#elif defined(HAVE_SYS_MMAN_H)
+  ptr = mmap(NULL, sz,
+             PROT_READ|PROT_WRITE,
+             MAP_ANON|MAP_PRIVATE,
+             -1, 0);
+  raw_assert(ptr != MAP_FAILED);
+  raw_assert(ptr != NULL);
+#else
+  ptr = tor_malloc_zero(sz);
+#endif
+
+  if (flags & ANONMAP_PRIVATE) {
+    int lock_result = lock_mem(ptr, sz);
+    raw_assert(lock_result == 0);
+    int nodump_result = nodump_mem(ptr, sz);
+    raw_assert(nodump_result == 0);
+  }
+
+  if (flags & ANONMAP_NOINHERIT) {
+    int noinherit_result = noinherit_mem(ptr, sz);
+    raw_assert(noinherit_result == 0);
+  }
+
+  return ptr;
+}
+
+/**
+ * Release <b>sz</b> bytes of memory that were previously mapped at
+ * <b>mapping</b> by tor_mmap_anonymous().
+ **/
+void
+tor_munmap_anonymous(void *mapping, size_t sz)
+{
+  if (!mapping)
+    return;
+
+#if defined(_WIN32)
+  (void)sz;
+  UnmapViewOfFile(mapping);
+#elif defined(HAVE_SYS_MMAN_H)
+  munmap(mapping, sz);
+#else
+  (void)sz;
+  tor_free(mapping);
+#endif
+}
diff --git a/src/lib/malloc/map_anon.h b/src/lib/malloc/map_anon.h
new file mode 100644
index 0000000000..cc5797e4ec
--- /dev/null
+++ b/src/lib/malloc/map_anon.h
@@ -0,0 +1,37 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2019, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file map_anon.h
+ * \brief Headers for map_anon.c
+ **/
+
+#ifndef TOR_MAP_ANON_H
+#define TOR_MAP_ANON_H
+
+#include "lib/malloc/malloc.h"
+#include <stddef.h>
+
+/**
+ * When this flag is specified, try to prevent the mapping from being
+ * swapped or dumped.
+ *
+ * In some operating systems, this flag is not implemented.
+ */
+#define ANONMAP_PRIVATE   (1u<<0)
+/**
+ * When this flag is specified, try to prevent the mapping from being
+ * inherited after a fork().  In some operating systems, trying to access it
+ * afterwards will cause its contents to be zero.  In others, trying to access
+ * it afterwards will cause a crash.
+ *
+ * In some operating systems, this flag is not implemented at all.
+ */
+#define ANONMAP_NOINHERIT (1u<<1)
+
+void *tor_mmap_anonymous(size_t sz, unsigned flags);
+void tor_munmap_anonymous(void *mapping, size_t sz);
+
+#endif /* !defined(TOR_MAP_ANON_H) */