File 1914-Publish-crypto-strong_rand_range-1.patch of Package erlang
From a2b40d28abdf19ff890a6cc5fdc61587bc89ca3d Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Thu, 6 Nov 2025 16:33:31 +0100
Subject: [PATCH 4/5] Publish `crypto:strong_rand_range/1`
---
lib/crypto/src/crypto.erl | 80 +++++++++++++++++++-------------
lib/crypto/test/crypto_SUITE.erl | 27 ++++++-----
2 files changed, 65 insertions(+), 42 deletions(-)
diff --git a/lib/crypto/src/crypto.erl b/lib/crypto/src/crypto.erl
index 46e385956b..1bdf623922 100644
--- a/lib/crypto/src/crypto.erl
+++ b/lib/crypto/src/crypto.erl
@@ -158,7 +158,7 @@ end
-export([sign/4, sign/5, verify/5, verify/6]).
-export([generate_key/2, generate_key/3, compute_key/4]).
-export([encapsulate_key/2, decapsulate_key/3]).
--export([exor/2, strong_rand_bytes/1, mod_pow/3]).
+-export([exor/2, strong_rand_bytes/1, strong_rand_range/1, mod_pow/3]).
-export([rand_seed/0, rand_seed_alg/1, rand_seed_alg/2]).
-export([rand_seed_s/0, rand_seed_alg_s/1, rand_seed_alg_s/2]).
-export([rand_plugin_next/1]).
@@ -331,13 +331,12 @@ end
-export([rand_plugin_aes_jump_2pow20/1]).
-deprecated(
- {rand_uniform, 2,
- "use rand_seed_s/0 with rand:uniform_s/2 instead"}).
+ {rand_uniform, 2, "use strong_rand_range/1 instead"}).
%% This should correspond to the similar macro in crypto.c
-define(MAX_BYTES_TO_NIF, 20000). %% Current value is: erlang:system_info(context_reductions) * 10
-%% Used by strong_rand_float/0
+%% Used by rand_plugin_uniform/1
-define(HALF_DBL_EPSILON, 1.1102230246251565e-16). % math:pow(2, -53)
@@ -2020,6 +2019,7 @@ strong_rand_bytes(Bytes) ->
false -> erlang:error(low_entropy);
Bin -> Bin
end.
+
strong_rand_bytes_nif(_Bytes) -> ?nif_stub.
@@ -2039,15 +2039,9 @@ pseudo-random number generator. `To` must be larger than `From`.
> cannot be fixed without making it raise `error:low_entropy`,
> which is not backwards compatible.
>
-> Instead, use for example:
->
-> ``` erlang
-> S0 = crypto:rand_seed_s(),
-> {Int, S1} = rand:uniform(To - From, S0),
-> From + Int - 1.
-> ```
+> Instead, use `strong_rand_range(To - From) + From`
>
-> Beware of the possible `error:low_entropy` exception.
+> Be aware of the possible `error:low_entropy` exception.
""".
-spec rand_uniform(crypto_integer(), crypto_integer()) ->
crypto_integer().
@@ -2098,6 +2092,45 @@ rand_seed(Seed) when is_binary(Seed) ->
rand_seed_nif(_Seed) -> ?nif_stub.
+-doc(#{group => <<"Random API">>,
+ since => <<"OTP @OTP-19841@">>}).
+-doc """
+Generate a random integer in a specified range.
+
+The returned random integer is in the interval is `0` =< `N` < `Range`.
+
+Uses the `crypto` library random number generator BN_rand_range.
+
+If the `Range` argument is a `pos_integer/0` the return value
+is a `non_neg_integer/0`. If the `Range` argument is a positive integer
+in a `binary/0`, the return value is a non-negative integer in a `binary/0`.
+
+May raise exception `error:low_entropy` in case the random generator failed due
+to lack of secure "randomness".
+""".
+-spec strong_rand_range(Range :: pos_integer()) -> N :: non_neg_integer();
+ (Range :: binary()) -> N :: binary().
+%% BN_rand_range
+strong_rand_range(Range) when is_integer(Range), Range > 0 ->
+ bin_to_int(strong_rand_range(int_to_bin(Range)));
+strong_rand_range(BinRange) when is_binary(BinRange) ->
+ case strong_rand_range_nif(BinRange) of
+ false ->
+ V = bin_to_int(BinRange),
+ if
+ 0 < V ->
+ erlang:error(low_entropy);
+ true ->
+ error(badarg, [BinRange])
+ end;
+ <<BinResult/binary>> ->
+ BinResult
+ end;
+strong_rand_range(Range) ->
+ error(badarg, [Range]).
+
+strong_rand_range_nif(_BinRange) -> ?nif_stub.
+
%%%================================================================
%%%
%%% RAND - Plug-In Generators for the `rand` module
@@ -2388,15 +2421,16 @@ rand_cache_size() ->
-doc false.
rand_plugin_next(Seed) ->
- {bytes_to_integer(strong_rand_range(1 bsl 64)), Seed}.
+ {strong_rand_range(1 bsl 64), Seed}.
-doc false.
rand_plugin_uniform(State) ->
- {strong_rand_float(), State}.
+ Value = ?HALF_DBL_EPSILON * strong_rand_range(1 bsl 53),
+ {Value, State}.
-doc false.
rand_plugin_uniform(Max, State) ->
- {bytes_to_integer(strong_rand_range(Max)) + 1, State}.
+ {strong_rand_range(Max) + 1, State}.
-doc false.
@@ -2511,22 +2545,6 @@ aes_cache(
[V|aes_cache(Encrypted, Cache)].
-strong_rand_range(Range) when is_integer(Range), Range > 0 ->
- BinRange = int_to_bin(Range),
- strong_rand_range(BinRange);
-strong_rand_range(BinRange) when is_binary(BinRange) ->
- case strong_rand_range_nif(BinRange) of
- false ->
- erlang:error(low_entropy);
- <<BinResult/binary>> ->
- BinResult
- end.
-strong_rand_range_nif(_BinRange) -> ?nif_stub.
-
-strong_rand_float() ->
- WholeRange = strong_rand_range(1 bsl 53),
- ?HALF_DBL_EPSILON * bytes_to_integer(WholeRange).
-
%%%================================================================
%%%
%%% Sign/verify
diff --git a/lib/crypto/test/crypto_SUITE.erl b/lib/crypto/test/crypto_SUITE.erl
index 6f780d467f..29f2066753 100644
--- a/lib/crypto/test/crypto_SUITE.erl
+++ b/lib/crypto/test/crypto_SUITE.erl
@@ -2155,19 +2155,24 @@ rand_uniform_aux_test(0) ->
rand_uniform_aux_test(N) ->
L = N*1000,
H = N*100000+1,
- crypto_rand_uniform(L, H),
- crypto_rand_uniform(-L, L),
- crypto_rand_uniform(-H, -L),
- crypto_rand_uniform(-H, L),
+ crypto_rand_range(L, H),
+ crypto_rand_range(-L, L),
+ crypto_rand_range(-H, -L),
+ crypto_rand_range(-H, L),
rand_uniform_aux_test(N-1).
-crypto_rand_uniform(L,H) ->
- R1 = (L-1) + rand:uniform(H-L),
- case (R1 >= L) and (R1 < H) of
- true ->
- ok;
- false ->
- ct:fail({"Not in interval", R1, L, H})
+crypto_rand_range(L,H) ->
+ Range = H-L,
+ R1 = crypto:strong_rand_range(Range),
+ case crypto:strong_rand_range(<<Range:32>>) of
+ Bin when is_binary(Bin) ->
+ <<R2:(bit_size(Bin))/integer>> = Bin,
+ if
+ is_integer(R1), 0 =< R1, R1 < Range, 0 =< R2, R2 < Range ->
+ ok;
+ true ->
+ ct:fail({"Not in range", R1, R2, Range})
+ end
end.
foldallmap(_Fun, AccN, []) ->
--
2.51.0
