Support generation of strong random numbers

4 files changed, 163 insertions, 6 deletions

diff --git a/lib/crypto/c_src/crypto.c b/lib/crypto/c_src/crypto.c
index b2f31870b9..0e17279e62 100644
--- a/lib/crypto/c_src/crypto.c
+++ b/lib/crypto/c_src/crypto.c
@@ -429,6 +429,7 @@ static ERL_NIF_TERM aes_ige_crypt_nif(ErlNifEnv* env, int argc, const ERL_NIF_TE
 static ERL_NIF_TERM aes_ctr_stream_init(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
 static ERL_NIF_TERM aes_ctr_stream_encrypt(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
 static ERL_NIF_TERM strong_rand_bytes_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
+static ERL_NIF_TERM strong_rand_uniform_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
 static ERL_NIF_TERM rand_uniform_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
 static ERL_NIF_TERM mod_exp_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
 static ERL_NIF_TERM dss_verify_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
@@ -501,6 +502,7 @@ static ErlNifFunc nif_funcs[] = {
     {"aes_ctr_stream_encrypt", 2, aes_ctr_stream_encrypt},
     {"aes_ctr_stream_decrypt", 2, aes_ctr_stream_encrypt},
     {"strong_rand_bytes_nif", 1, strong_rand_bytes_nif},
+    {"strong_rand_uniform_nif", 2, strong_rand_uniform_nif},
     {"rand_uniform_nif", 2, rand_uniform_nif},
     {"mod_exp_nif", 4, mod_exp_nif},
     {"dss_verify_nif", 4, dss_verify_nif},
@@ -2331,6 +2333,38 @@ static ERL_NIF_TERM bin_from_bn(ErlNifEnv* env, const BIGNUM *bn)
     return term;
 }
 
+static ERL_NIF_TERM strong_rand_uniform_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{/* (Lo,Hi) */
+    BIGNUM *bn_from = NULL, *bn_to, *bn_rand;
+    unsigned char* data;
+    unsigned dlen;
+    ERL_NIF_TERM ret;
+
+    if (!get_bn_from_mpint(env, argv[0], &bn_from)
+	|| !get_bn_from_mpint(env, argv[1], &bn_rand)) {
+	if (bn_from) BN_free(bn_from);
+	return enif_make_badarg(env);
+    }
+
+    bn_to = BN_new();
+    BN_sub(bn_to, bn_rand, bn_from);
+    if (BN_rand_range(bn_rand, bn_to) != 1) {
+        ret = atom_false;
+    }
+    else {
+        BN_add(bn_rand, bn_rand, bn_from);
+        dlen = BN_num_bytes(bn_rand);
+        data = enif_make_new_binary(env, dlen+4, &ret);
+        put_int32(data, dlen);
+        BN_bn2bin(bn_rand, data+4);
+        ERL_VALGRIND_MAKE_MEM_DEFINED(data+4, dlen);
+    }
+    BN_free(bn_rand);
+    BN_free(bn_from);
+    BN_free(bn_to);
+    return ret;
+}
+
 static ERL_NIF_TERM rand_uniform_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
 {/* (Lo,Hi) */
     BIGNUM *bn_from = NULL, *bn_to, *bn_rand;
diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml
index d0deaceaaf..0697f6a202 100644
--- a/lib/crypto/doc/src/crypto.xml
+++ b/lib/crypto/doc/src/crypto.xml
@@ -658,10 +658,13 @@
       </type>
       <desc>
         <p>Set the seed for PRNG to the given binary. This calls the
-	RAND_seed function from openssl. Only use this if the system
-	you are running on does not have enough "randomness" built in.
-	Normally this is when <seealso marker="#strong_rand_bytes/1">
-	strong_rand_bytes/1</seealso> returns <c>low_entropy</c></p>
+        RAND_seed function from openssl. Only use this if the system
+        you are running on does not have enough "randomness" built in.
+        Normally this is when either
+        <seealso marker="#strong_rand_bytes/1">strong_rand_bytes/1</seealso>,
+        <seealso marker="#strong_rand_uniform/0">strong_rand_uniform/0</seealso> or
+        <seealso marker="#strong_rand_uniform/1">strong_rand_uniform/1</seealso>
+        throws <c>low_entropy</c></p>
       </desc>
     </func>
 
@@ -728,6 +731,41 @@
 	failed due to lack of secure "randomness".</p>
       </desc>
     </func>
+
+    <func>
+      <name>strong_rand_uniform() -> X</name>
+      <fsummary>Generate a random floating point number between 0.0 and 1.0</fsummary>
+      <type>
+        <v>X = float()</v>
+      </type>
+      <desc>
+        <p>Generates a random floating pointer number uniformly distributed
+        in the value range <c><![CDATA[X, 0.0 < X < 1.0.]]></c>
+        Uses a cryptographically secure prng seeded and periodically mixed with operating system
+        provided entropy. By default this is the <c>BN_rand_range</c> method from OpenSSL.</p>
+        <p>May throw exception <c>low_entropy</c> in case the random generator
+        failed due to lack of secure "randomness".</p>
+        <note><p>The generated values shall present no more than 51 bits of effective entropy.</p></note>
+      </desc>
+    </func>
+
+    <func>
+      <name>strong_rand_uniform(N) -> X</name>
+      <fsummary>Generate a random positive integer between 1 and N</fsummary>
+      <type>
+        <v>N = pos_integer()</v>
+        <v>X = 1..N</v>
+      </type>
+      <desc>
+        <p>Generates a a random positive integer uniformly distributed
+        in the value range <c><![CDATA[X, 1 =< X =< N.]]></c>
+        Uses a cryptographically secure prng seeded and periodically mixed with operating system
+        provided entropy. By default this is the <c>BN_rand_range</c> method from OpenSSL.</p>
+        <p>May throw exception <c>low_entropy</c> in case the random generator
+        failed due to lack of secure "randomness".</p>
+      </desc>
+    </func>
+
     <func>
       <name>stream_init(Type, Key) -> State</name>
       <fsummary></fsummary>
diff --git a/lib/crypto/src/crypto.erl b/lib/crypto/src/crypto.erl
index 631af62615..4b386924cb 100644
--- a/lib/crypto/src/crypto.erl
+++ b/lib/crypto/src/crypto.erl
@@ -30,6 +30,8 @@
 -export([hmac/3, hmac/4, hmac_init/2, hmac_update/2, hmac_final/1, hmac_final_n/2]).
 -export([cmac/3, cmac/4]).
 -export([exor/2, strong_rand_bytes/1, mod_pow/3]).
+-export([strong_rand_uniform/0]).
+-export([strong_rand_uniform/1]).
 -export([rand_uniform/2]).
 -export([block_encrypt/3, block_decrypt/3, block_encrypt/4, block_decrypt/4]).
 -export([next_iv/2, next_iv/3]).
@@ -283,9 +285,11 @@ stream_decrypt(State, Data0) ->
     stream_crypt(fun do_stream_decrypt/2, State, Data, erlang:byte_size(Data), MaxByts, []).
 
 %%
-%% RAND - pseudo random numbers using RN_ functions in crypto lib
+%% RAND - pseudo random numbers using RN_ and BN_ functions in crypto lib
 %%
 -spec strong_rand_bytes(non_neg_integer()) -> binary().
+-spec strong_rand_uniform() -> float().
+-spec strong_rand_uniform(pos_integer()) -> pos_integer().
 -spec rand_uniform(crypto_integer(), crypto_integer()) ->
 			  crypto_integer().
 
@@ -297,6 +301,38 @@ strong_rand_bytes(Bytes) ->
 strong_rand_bytes_nif(_Bytes) -> ?nif_stub.
 
 
+strong_rand_uniform() ->
+    Sign = 0, % positive
+    Exponent = 1023, % on the interval [1.0, 2.0[
+    Fraction = strong_rand_uniform(1, 1 bsl 52), % the whole interval above (except 1.0)
+    <<Value:64/big-float>> = <<Sign:1, Exponent:11, Fraction:52>>,
+    Value - 1.0.
+
+strong_rand_uniform(N) when is_integer(N), N >= 1 ->
+    1 + strong_rand_uniform(0, N).
+
+strong_rand_uniform(From, To) when is_binary(From), is_binary(To) ->
+    case strong_rand_uniform_nif(From,To) of
+        false ->
+            erlang:error(low_entropy);
+        <<Len:32/integer, MSB, Rest/binary>> when MSB > 127 ->
+            <<(Len + 1):32/integer, 0, MSB, Rest/binary>>;
+        Whatever ->
+            Whatever
+    end;
+strong_rand_uniform(From, To) when is_integer(From), is_integer(To), From < To ->
+    BinFrom = mpint(From),
+    BinTo = mpint(To),
+    case strong_rand_uniform(BinFrom, BinTo) of
+        Result when is_binary(Result) ->
+            erlint(Result);
+        Other ->
+            Other
+    end.
+
+strong_rand_uniform_nif(_From, _To) -> ?nif_stub.
+
+
 rand_uniform(From,To) when is_binary(From), is_binary(To) ->
     case rand_uniform_nif(From,To) of
 	<<Len:32/integer, MSB, Rest/binary>> when MSB > 127 ->
@@ -325,6 +361,7 @@ rand_uniform_pos(_,_) ->
 
 rand_uniform_nif(_From,_To) -> ?nif_stub.
 
+
 -spec rand_seed(binary()) -> ok.
 rand_seed(Seed) ->
     rand_seed_nif(Seed).
diff --git a/lib/crypto/test/crypto_SUITE.erl b/lib/crypto/test/crypto_SUITE.erl
index 1d7037d003..6e3a3879c4 100644
--- a/lib/crypto/test/crypto_SUITE.erl
+++ b/lib/crypto/test/crypto_SUITE.erl
@@ -36,7 +36,9 @@ all() ->
      {group, non_fips},
      mod_pow,
      exor,
-     rand_uniform
+     rand_uniform,
+     strong_rand_uniform_float,
+     strong_rand_uniform_integer
     ].
 
 groups() ->
@@ -486,6 +488,44 @@ rand_uniform(Config) when is_list(Config) ->
     10 = byte_size(crypto:strong_rand_bytes(10)).
 
 %%--------------------------------------------------------------------
+strong_rand_uniform_float() ->
+    [{doc, "strong_rand_uniform float testing"}].
+strong_rand_uniform_float(Config) when is_list(Config) ->
+    Samples = [crypto:strong_rand_uniform() || _ <- lists:seq(1, 10000)],
+    allmap(
+       fun (V) ->
+               (V >= 0.0 andalso V < 1.0)
+               orelse {false, ct:fail({"Not in interval", V, 0.0, 1.0})}
+        end,
+       Samples).
+
+strong_rand_uniform_integer() ->
+    [{doc, "strong_rand_uniform integer testing"}].
+strong_rand_uniform_integer(Config) when is_list(Config) ->
+    MaxCeiling = 1 bsl 32,
+    Ceilings = [1 | % edge case where the ceiling equals the floor
+                [crypto:strong_rand_uniform(MaxCeiling)
+                 || _ <- lists:seq(1, 99)]],
+
+    allmap(
+      fun (Ceiling) ->
+              case Ceiling >= 1 andalso Ceiling =< MaxCeiling of
+                  false ->
+                      {false, ct:fail({"Ceiling not in interval", Ceiling, 1, MaxCeiling})};
+                  true ->
+                      Samples = [crypto:strong_rand_uniform(Ceiling)
+                                 || _ <- lists:seq(1, 100)],
+                      allmap(
+                        fun (V) ->
+                                (V >= 1 andalso V =< Ceiling)
+                                orelse {false, ct:fail({"Sample not in interval", V, 1, Ceiling})}
+                        end,
+                        Samples)
+              end
+      end,
+      Ceilings).
+
+%%--------------------------------------------------------------------
 %% Internal functions ------------------------------------------------
 %%--------------------------------------------------------------------
 hash(_, [], []) ->
@@ -951,6 +991,14 @@ crypto_rand_uniform(L,H) ->
 	    ct:fail({"Not in interval", R1, L, H})
     end.
 
+allmap(_Fun, []) ->
+    true;
+allmap(Fun, [H|T]) ->
+    case Fun(H) of
+        true -> allmap(Fun, T);
+        {false, Result} -> Result
+    end.
+
 %%--------------------------------------------------------------------
 %% Test data ------------------------------------------------
 %%--------------------------------------------------------------------