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Add TLS transport option to pin the TLS version #3

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Merged
codeadict merged 1 commit into from
Sep 25, 2026
Merged

Add TLS transport option to pin the TLS version #3

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31 changes: 26 additions & 5 deletions src/gen_http_ssl.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ Options:
- `socket_opts` - Additional SSL options
- `verify` (default `verify_peer`) - Certificate verification mode
- `cacerts` - CA certificates for verification
- `tls` - Pin the TLS version: `"1.2"` or `"1.3"`. Absent: OTP default.
""").
-spec connect(address(), inet:port_number(), proplists:proplist()) ->
{ok, socket()} | {error, term()}.
Expand Down Expand Up @@ -71,9 +72,8 @@ connect(Address, Port, Opts) ->
{packet, raw},
{active, false},
{alpn_advertised_protocols, AlpnProtocols},
{reuseaddr, true},
{reuse_sessions, true}
| SniOpts ++ [{K, V} || {K, V} <- Opts, K =:= sndbuf orelse K =:= recbuf]
{reuseaddr, true}
| session_opts(Opts) ++ SniOpts ++ [{K, V} || {K, V} <- Opts, K =:= sndbuf orelse K =:= recbuf]
],

%% Add verification options (verify_peer by default)
Expand All @@ -95,7 +95,8 @@ connect(Address, Port, Opts) ->
end,

%% Combine all options
SocketOpts = BaseOpts ++ VerifyOpts ++ proplists:get_value(socket_opts, Opts, []),
SocketOpts = BaseOpts ++ VerifyOpts ++ tls_version_opts(Opts)
++ proplists:get_value(socket_opts, Opts, []),

case ssl:connect(NormalizedAddress, Port, SocketOpts, Timeout) of
{ok, Socket} ->
Expand Down Expand Up @@ -129,7 +130,7 @@ upgrade(Socket, _OriginalScheme, Hostname, _Port, Opts) ->
{active, false},
{alpn_advertised_protocols, AlpnProtocols},
{server_name_indication, binary_to_list(Hostname)}
| proplists:get_value(socket_opts, Opts, [])
| tls_version_opts(Opts) ++ proplists:get_value(socket_opts, Opts, [])
],

ssl:connect(Socket, SSLOpts, Timeout).
Expand Down Expand Up @@ -260,3 +261,23 @@ get_cacerts_opts(Opts) ->
CACerts ->
[{cacerts, CACerts}]
end.

%% `{tls, "1.2"}' / `{tls, "1.3"}' pins the negotiated TLS version.
%% Anything else is a configuration error, raised before connecting.
-spec tls_version_opts(proplists:proplist()) -> [{versions, [ssl:tls_version()]}].
tls_version_opts(Opts) ->
case proplists:get_value(tls, Opts) of
undefined -> [];
"1.2" -> [{versions, ['tlsv1.2']}];
"1.3" -> [{versions, ['tlsv1.3']}];
Other -> error({invalid_tls_version, Other})
end.

%% `reuse_sessions' is a TLS =< 1.2 option: OTP rejects it alongside a
%% TLS-1.3-only `versions' list, so drop it when 1.3 is pinned.
-spec session_opts(proplists:proplist()) -> [{reuse_sessions, true}].
session_opts(Opts) ->
case proplists:get_value(tls, Opts) of
"1.3" -> [];
_ -> [{reuse_sessions, true}]
end.