feat: For otp 25+ use public_key:cacerts_get for the default certificate list. (#114)

closes #113
Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

---------

Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>

Author: yordis

src/ldclient_config.erl

@@ -281,7 +281,27 @@ get_event_schema() ->
 %% @end
 -spec tls_basic_options() -> [ssl:tls_client_option()].
 tls_basic_options() ->
-    tls_basic_options(filelib:is_regular(?HTTP_DEFAULT_LINUX_CASTORE)).
+    case erlang:list_to_integer(erlang:system_info(otp_release)) >= 25 of
+        true -> tls_basic_erlef_options();
+        false -> tls_basic_options(filelib:is_regular(?HTTP_DEFAULT_LINUX_CASTORE))
+    end.
+
+%% The public_key:cacerts_get function does not exist prior to OTP 25, so we
+%% need to ignore the warning when building code that will not be using it.
+-dialyzer({no_missing_calls, tls_basic_erlef_options/0}).
+
+%% @doc Provide basic options for using TLS with the default OTP 25+.
+%% Follows the recommendations from the Erlang Security Working Group.
+%% https://erlef.github.io/security-wg/secure_coding_and_deployment_hardening/ssl
+%%
+%% @end
+-spec tls_basic_erlef_options() -> [ssl:tls_client_option()].
+tls_basic_erlef_options() ->
+    CaCerts = public_key:cacerts_get(),
+    [
+        {cacerts, CaCerts}
+        | tls_base_options()
+    ].
 
 %% @doc Provide basic options for using TLS with the default linux store.
 %% This will try to use the a certificate store located at

test/ldclient_config_SUITE.erl

@@ -133,24 +133,36 @@ get_http_options_multiple_options(_) ->
     } = maps:get(http_options, Settings, undefined).
 
 tls_basic_options(_) ->
-    BasicOptions = ldclient_config:tls_basic_options(),
-    case os:type() of
-        {unix, linux} ->
-            [
-                {cacertfile, "/etc/ssl/certs/ca-certificates.crt"},
-                {verify, verify_peer},
-                {ciphers, Ciphers},
-                {depth, 3},
-                {customize_hostname_check, _}] = BasicOptions,
-            true = (length(Ciphers) =/= 0);
-        {_, _} ->
-            [
-                {cacerts, _},
-                {verify, verify_peer},
-                {ciphers, Ciphers},
-                {depth, 3},
-                {customize_hostname_check, _}] = BasicOptions,
-            true = (length(Ciphers) =/= 0)
+    case erlang:list_to_integer(erlang:system_info(otp_release)) >= 25 of
+    true -> 
+        BasicOptions = ldclient_config:tls_basic_options(),
+        CaCerts = public_key:cacerts_get(),
+        [{cacerts, CaCerts},
+        {verify, verify_peer},
+        {ciphers, Ciphers},
+        {depth, 3},
+        {customize_hostname_check, _}] = BasicOptions,
+        true = (length(Ciphers) =/= 0);
+    false -> 
+        BasicOptions = ldclient_config:tls_basic_options(),
+        case os:type() of
+            {unix, linux} ->
+                [
+                    {cacertfile, "/etc/ssl/certs/ca-certificates.crt"},
+                    {verify, verify_peer},
+                    {ciphers, Ciphers},
+                    {depth, 3},
+                    {customize_hostname_check, _}] = BasicOptions,
+                true = (length(Ciphers) =/= 0);
+            {_, _} ->
+                [
+                    {cacerts, _},
+                    {verify, verify_peer},
+                    {ciphers, Ciphers},
+                    {depth, 3},
+                    {customize_hostname_check, _}] = BasicOptions,
+                true = (length(Ciphers) =/= 0)
+        end
     end.
 
 tls_with_ca_certfile_options(_) ->