feat(hb_http_signature): wip started imple with signature_params_line…

…, derive_component, and api #13

src/hb_http_signature.erl

@@ -0,0 +1,271 @@
+-module(hb_http_signature).
+
+-export([authority/3, sign/2, sign/3, signature_params_line/2]).
+
+% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2.7-14
+-define(EMPTY_QUERY_PARAMS, $?).
+
+%%%
+%%% Ideal API
+%%% authority(ComponentIdentifiers, Params) -> Authority
+%%%
+%%% sign(Authority, Req, Res) -> {ok, {SigName, SigInput, Sig}
+%%% verify(Authority, SigName, Msg) -> {ok}
+%%%
+
+authority(ComponentIdentifiers, SigParams, Key) ->
+	#{
+		component_identifiers => ComponentIdentifiers,
+		sig_params => SigParams,
+		key => Key
+	}.
+
+sign(Authority, Req) ->
+	sign(Authority, Req, #{}).
+sign(Authority, Req, Res) ->
+	ComponentIdentifiers = maps:get(component_identifiers, Authority),
+	SignatureComponentsLine = signature_components_line(ComponentIdentifiers, Req, Res),
+	SignatureParamsLine = signature_params_line(ComponentIdentifiers, maps:get(sig_params, Authority)),
+	SignatureBase =
+		<<SignatureComponentsLine/binary, <<"\n">>, <<"\"@signature-params\": ">>, SignatureParamsLine/binary>>,
+	Name = random_an_binary(5),
+	SignatureInput = SignatureParamsLine,
+	% Create signature using SignatureBase and authority#key
+	Signature = create_signature(Authority, SignatureBase),
+	{ok, {Name, SignatureInput, Signature}}.
+
+create_signature(Authority, SignatureBase) ->
+	Key = maps:get(key, Authority),
+	% TODO: implement
+	Signature = <<"SIGNED", SignatureBase/binary>>,
+	Signature.
+
+%%%
+%%% TODO: Ensure error cases are covered
+%%% - dup CI: https://datatracker.ietf.org/doc/html/rfc9421#section-2.5-7.2.2.5.2.1
+%%%
+signature_components_line(ComponentIdentifiers, Req, Res) ->
+	ComponentsLine = lists:foldl(
+		fun(Line, Identifier) ->
+			% TODO: handle errors?
+			{ok, {I, V}} = identifier_to_component(Identifier, Req, Res),
+			% https://datatracker.ietf.org/doc/html/rfc9421#section-2.5-7.2.1
+			<<Line, I/binary, <<": ">>, V/binary, <<"\n">>>>
+		end,
+		<<>>,
+		ComponentIdentifiers
+	),
+	bin(ComponentsLine).
+
+%%%
+%%% @doc construct the signature-params line part of the signature base.
+%%%
+%%% ComponentIdentifiers: a list of "component identifiers" to be included
+%%% in the signature.
+%%%
+%%% SigParams: a map or list of pairs that contain the metadata parameters
+%%% for the signature
+%%%
+%%% See https://datatracker.ietf.org/doc/html/rfc9421#section-2.5-7.3.2.4
+%%%
+signature_params_line(ComponentIdentifiers, SigParams) when is_map(SigParams) ->
+	signature_params_line(ComponentIdentifiers, maps:to_list(SigParams));
+signature_params_line(ComponentIdentifiers, SigParams) when is_list(SigParams) ->
+	SfList = [
+		{
+			list,
+			lists:map(fun sf_item/1, ComponentIdentifiers),
+			lists:map(
+				fun
+					({K, V}) when is_integer(V) -> {bin(K), V};
+					({K, V}) -> {bin(K), {string, bin(V)}}
+				end,
+				SigParams
+			)
+		}
+	],
+	Res = hb_http_structured_fields:list(SfList),
+	bin(Res).
+
+identifier_to_component(Identifier = <<"@", _R/bits>>, Req, Res) -> derive_component(Identifier, Req, Res);
+identifier_to_component(Identifier, Req, Res) -> extract_header(Identifier, Req, Res).
+
+extract_header(Identifier, Req, Res = #{}) ->
+	extract_header(Identifier, Req, Res, req);
+extract_header(Identifier, Req, Res) ->
+	extract_header(Identifier, Req, Res, res).
+extract_header(Identifier, Req, Res, _Subject) ->
+	% The Identifier may have params and so we need to parse it
+	% See https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-6
+	{item, {string, IParsed}, IParams} = sf_item(Identifier),
+	IsStrictFormat = get_sf_item_param(<<"sf">>, IParams, false) andalso true,
+	IsByteSequenceEncoded = get_sf_item_param(<<"bs">>, IParams, false) andalso true,
+	DictKey = get_sf_item_param(<<"key">>, IParams, false),
+	case (IsStrictFormat orelse DictKey) andalso IsByteSequenceEncoded of
+		true ->
+			% https://datatracker.ietf.org/doc/html/rfc9421#section-2.5-7.2.2.5.2.2
+			{conflicting_params_error, <<"Component Identifier MUST not contain both 'sf' and 'bs' parameters">>};
+		_ ->
+			Lowered = lower_bin(IParsed),
+			IsRequestIdentifier = get_sf_item_param(<<"req">>, IParams, false),
+			Msg = IsRequestIdentifier andalso Req orelse Res,
+			% Fields are case-insensitive, so we perform a search across the Msg fields
+			MaybeField = lists:keyfind(Lowered, 1, [
+				{lower_bin(Key), Value}
+			 || {Key, Value} <- maps:to_list(maps:get(fields, Msg, #{}))
+			]),
+			case MaybeField of
+				false ->
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.5-7.2.2.5.2.6
+					{field_not_found_error, <<"Component Identifier for a field MUST be present on the message">>};
+				_ ->
+					% The Field was found, but we still need to potentially parse it
+					% (it could be a Structured Field) and potentially extract
+					% subsequent values ie. specific dictionary key and its parameters
+					% TODO: implement
+					ok
+			end,
+			ok
+	end.
+
+derive_component(Identifier, Req, Res = #{}) ->
+	derive_component(Identifier, Req, Res, req);
+derive_component(Identifier, Req, Res) ->
+	derive_component(Identifier, Req, Res, res).
+derive_component(Identifier, Req, Res, Subject) when is_list(Identifier) ->
+	derive_component(list_to_binary(Identifier), Req, Res, Subject);
+derive_component(Identifier, Req, Res, Subject) when is_atom(Identifier) ->
+	derive_component(atom_to_binary(Identifier), Req, Res, Subject);
+derive_component(Identifier, Req, Res, Subject) when is_binary(Identifier) ->
+	% The Identifier may have params and so we need to parse it
+	% See https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-6
+	{item, {string, IParsed}, IParams} = sf_item(Identifier),
+	case get_sf_item_param(<<"req">>, IParams, false) andalso Subject =:= req of
+		% https://datatracker.ietf.org/doc/html/rfc9421#section-2.5-7.2.2.5.2.3
+		true ->
+			{req_identifier_error,
+				<<"A Component Identifier may not contain a req parameter if the target is a response message">>};
+		_ ->
+			Lowered = lower_bin(IParsed),
+			NormalizedItem = hb_http_structured_fields:item({item, {string, Lowered}, IParams}),
+			Derived =
+				case Lowered of
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.2.1
+					<<"@method">> ->
+						{ok, {NormalizedItem, upper_bin(maps:get(method, Req))}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.4.1
+					<<"@target-uri">> ->
+						{ok, {NormalizedItem, bin(maps:get(url, Req))}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.6.1
+					<<"@authority">> ->
+						URI = uri_string:parse(maps:get(url, Req)),
+						Authority = maps:get(host, URI),
+						{ok, {NormalizedItem, lower_bin(Authority)}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.8.1
+					<<"@scheme">> ->
+						URI = uri_string:parse(maps:get(url, Req)),
+						Scheme = maps:get(schema, URI),
+						{ok, {NormalizedItem, lower_bin(Scheme)}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.10.1
+					<<"@request-target">> ->
+						URI = uri_string:parse(maps:get(url, Req)),
+						% If message contains the absolute form value, then
+						% the value must be the absolut url
+						%
+						% TODO: maybe better way to distinguish besides a flag
+						% on the request?
+						%
+						% See https://datatracker.ietf.org/doc/html/rfc9421#section-2.2.5-10
+						RequestTarget =
+							case maps:get(is_absolute_form, Req) of
+								true -> URI;
+								_ -> lists:join($?, [maps:get(path, URI), maps:get(query, URI, ?EMPTY_QUERY_PARAMS)])
+							end,
+						{ok, {NormalizedItem, bin(RequestTarget)}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.12.1
+					<<"@path">> ->
+						URI = uri_string:parse(maps:get(url, Req)),
+						Path = maps:get(path, URI),
+						{ok, {NormalizedItem, bin(Path)}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.14.1
+					<<"@query">> ->
+						URI = uri_string:parse(maps:get(url, Req)),
+						Query = maps:get(query, URI, ?EMPTY_QUERY_PARAMS),
+						{ok, {NormalizedItem, bin(Query)}};
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.16.1
+					<<"@query-param">> ->
+						URI = uri_string:parse(maps:get(url, Req)),
+						case get_sf_item_param(<<"name">>, IParams, false) of
+							% The name parameter MUST be provided when specifiying a @query-param
+							% Derived Component. See https://datatracker.ietf.org/doc/html/rfc9421#section-2.2.8-1
+							false ->
+								{req_identifier_error, <<"@query_param Derived Component Identifier must specify a name parameter">>};
+							Name ->
+								QueryParams = uri_string:dissect_query(maps:get(query, URI, "")),
+								QueryParam =
+									case lists:keyfind(Name, 1, QueryParams) of
+										{_, QP} -> QP;
+										% An missing or empty query param value results in
+										% an empty string value in the signature base
+										% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2.8-4
+										_ -> ""
+									end,
+								{ok, {NormalizedItem, bin(QueryParam)}}
+						end;
+					% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2-4.18.1
+					<<"@status">> ->
+						case Subject =:= req of
+							% https://datatracker.ietf.org/doc/html/rfc9421#section-2.2.9-8
+							true ->
+								{res_identifier_error, <<"@status Derived Component must not be used if target is a request message">>};
+							_ ->
+								Status = maps:get(status, Res, <<"200">>),
+								{ok, {NormalizedItem, Status}}
+						end
+				end,
+			Derived
+	end.
+
+%%%
+%%% Data Utilities
+%%%
+
+sf_item(ComponentIdentifier = {item, _Item, _Params}) ->
+	ComponentIdentifier;
+% TODO: should we check whether the string is already quoted?
+sf_item(ComponentIdentifier) when is_list(ComponentIdentifier) ->
+	sf_item(<<$", (lower_bin(ComponentIdentifier))/binary, $">>);
+sf_item(ComponentIdentifier) when is_binary(ComponentIdentifier) ->
+	hb_http_structured_fields:parse_item(ComponentIdentifier).
+
+get_sf_item_param(Name, SfItemParams, Default) when is_list(Name) ->
+	get_sf_item_param(list_to_binary(Name), SfItemParams, Default);
+get_sf_item_param(Name, SfItemParams, Default) ->
+	% [{<<"name">>,{string,<<"baz">>}}]
+	case lists:keyfind(Name, 1, SfItemParams) of
+		{_, {_, Value}} -> Value;
+		_ -> Default
+	end.
+
+upper_bin(Item) when is_binary(Item) -> upper_bin(binary_to_list(Item));
+upper_bin(Item) when is_list(Item) -> bin(string:uppercase(Item)).
+
+lower_bin(Item) when is_binary(Item) -> lower_bin(binary_to_list(Item));
+lower_bin(Item) when is_list(Item) -> bin(string:lowercase(Item)).
+
+bin(Item) when is_atom(Item) -> atom_to_binary(Item, utf8);
+bin(Item) when is_integer(Item) ->
+	case Item of
+		% Treat integer as an ASCII code
+		N when N > 0 andalso N < 256 -> <<N>>;
+		N -> integer_to_binary(N)
+	end;
+bin(Item) ->
+	iolist_to_binary(Item).
+
+random_an_binary(Length) ->
+	Characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789",
+	ListLength = length(Characters),
+	RandomIndexes = [rand:uniform(ListLength) || _ <- lists:seq(1, Length)],
+	RandomChars = [lists:nth(Index, Characters) || Index <- RandomIndexes],
+	list_to_binary(RandomChars).