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%% Copyright (c) 2013-2017, Loïc Hoguin <[email protected]>
%% Copyright (c) 2011, Magnus Klaar <[email protected]>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-module(cowboy_static).
-export([init/2]).
-export([malformed_request/2]).
-export([forbidden/2]).
-export([content_types_provided/2]).
-export([resource_exists/2]).
-export([last_modified/2]).
-export([generate_etag/2]).
-export([get_file/2]).
-type extra_etag() :: {etag, module(), function()} | {etag, false}.
-type extra_mimetypes() :: {mimetypes, module(), function()}
| {mimetypes, binary() | {binary(), binary(), [{binary(), binary()}]}}.
-type extra() :: [extra_etag() | extra_mimetypes()].
-type opts() :: {file | dir, string() | binary()}
| {file | dir, string() | binary(), extra()}
| {priv_file | priv_dir, atom(), string() | binary()}
| {priv_file | priv_dir, atom(), string() | binary(), extra()}.
-export_type([opts/0]).
-include_lib("kernel/include/file.hrl").
-type state() :: {binary(), {ok, #file_info{}} | {error, atom()}, extra()}.
%% Resolve the file that will be sent and get its file information.
%% If the handler is configured to manage a directory, check that the
%% requested file is inside the configured directory.
-spec init(Req, opts()) -> {cowboy_rest, Req, error | state()} when Req::cowboy_req:req().
init(Req, {Name, Path}) ->
init_opts(Req, {Name, Path, []});
init(Req, {Name, App, Path})
when Name =:= priv_file; Name =:= priv_dir ->
init_opts(Req, {Name, App, Path, []});
init(Req, Opts) ->
init_opts(Req, Opts).
init_opts(Req, {priv_file, App, Path, Extra}) ->
init_info(Req, absname(priv_path(App, Path)), Extra);
init_opts(Req, {file, Path, Extra}) ->
init_info(Req, absname(Path), Extra);
init_opts(Req, {priv_dir, App, Path, Extra}) ->
init_dir(Req, priv_path(App, Path), Extra);
init_opts(Req, {dir, Path, Extra}) ->
init_dir(Req, Path, Extra).
priv_path(App, Path) ->
case code:priv_dir(App) of
{error, bad_name} ->
error({badarg, "Can't resolve the priv_dir of application "
++ atom_to_list(App)});
PrivDir when is_list(Path) ->
PrivDir ++ "/" ++ Path;
PrivDir when is_binary(Path) ->
<< (list_to_binary(PrivDir))/binary, $/, Path/binary >>
end.
absname(Path) when is_list(Path) ->
filename:absname(list_to_binary(Path));
absname(Path) when is_binary(Path) ->
filename:absname(Path).
init_dir(Req, Path, Extra) when is_list(Path) ->
init_dir(Req, list_to_binary(Path), Extra);
init_dir(Req, Path, Extra) ->
Dir = fullpath(filename:absname(Path)),
PathInfo = cowboy_req:path_info(Req),
Filepath = filename:join([Dir|[escape_reserved(P, <<>>) || P <- PathInfo]]),
Len = byte_size(Dir),
case fullpath(Filepath) of
<< Dir:Len/binary, $/, _/binary >> ->
init_info(Req, Filepath, Extra);
<< Dir:Len/binary >> ->
init_info(Req, Filepath, Extra);
_ ->
{cowboy_rest, Req, error}
end.
%% We escape the slash found in path segments because
%% a segment corresponds to a directory entry, and
%% therefore those slashes are expected to be part of
%% the directory name.
%%
%% Note that on most systems the slash is prohibited
%% and cannot appear in filenames, which means the
%% requested file will end up being not found.
escape_reserved(<<>>, Acc) ->
Acc;
escape_reserved(<< $/, Rest/bits >>, Acc) ->
escape_reserved(Rest, << Acc/binary, $\\, $/ >>);
escape_reserved(<< C, Rest/bits >>, Acc) ->
escape_reserved(Rest, << Acc/binary, C >>).
fullpath(Path) ->
fullpath(filename:split(Path), []).
fullpath([], Acc) ->
filename:join(lists:reverse(Acc));
fullpath([<<".">>|Tail], Acc) ->
fullpath(Tail, Acc);
fullpath([<<"..">>|Tail], Acc=[_]) ->
fullpath(Tail, Acc);
fullpath([<<"..">>|Tail], [_|Acc]) ->
fullpath(Tail, Acc);
fullpath([Segment|Tail], Acc) ->
fullpath(Tail, [Segment|Acc]).
init_info(Req, Path, Extra) ->
Info = file:read_file_info(Path, [{time, universal}]),
{cowboy_rest, Req, {Path, Info, Extra}}.
-ifdef(TEST).
fullpath_test_() ->
Tests = [
{<<"/home/cowboy">>, <<"/home/cowboy">>},
{<<"/home/cowboy">>, <<"/home/cowboy/">>},
{<<"/home/cowboy">>, <<"/home/cowboy/./">>},
{<<"/home/cowboy">>, <<"/home/cowboy/./././././.">>},
{<<"/home/cowboy">>, <<"/home/cowboy/abc/..">>},
{<<"/home/cowboy">>, <<"/home/cowboy/abc/../">>},
{<<"/home/cowboy">>, <<"/home/cowboy/abc/./../.">>},
{<<"/">>, <<"/home/cowboy/../../../../../..">>},
{<<"/etc/passwd">>, <<"/home/cowboy/../../etc/passwd">>}
],
[{P, fun() -> R = fullpath(P) end} || {R, P} <- Tests].
good_path_check_test_() ->
Tests = [
<<"/home/cowboy/file">>,
<<"/home/cowboy/file/">>,
<<"/home/cowboy/./file">>,
<<"/home/cowboy/././././././file">>,
<<"/home/cowboy/abc/../file">>,
<<"/home/cowboy/abc/../file">>,
<<"/home/cowboy/abc/./.././file">>
],
[{P, fun() ->
case fullpath(P) of
<< "/home/cowboy/", _/bits >> -> ok
end
end} || P <- Tests].
bad_path_check_test_() ->
Tests = [
<<"/home/cowboy/../../../../../../file">>,
<<"/home/cowboy/../../etc/passwd">>
],
[{P, fun() ->
error = case fullpath(P) of
<< "/home/cowboy/", _/bits >> -> ok;
_ -> error
end
end} || P <- Tests].
good_path_win32_check_test_() ->
Tests = case os:type() of
{unix, _} ->
[];
{win32, _} ->
[
<<"c:/home/cowboy/file">>,
<<"c:/home/cowboy/file/">>,
<<"c:/home/cowboy/./file">>,
<<"c:/home/cowboy/././././././file">>,
<<"c:/home/cowboy/abc/../file">>,
<<"c:/home/cowboy/abc/../file">>,
<<"c:/home/cowboy/abc/./.././file">>
]
end,
[{P, fun() ->
case fullpath(P) of
<< "c:/home/cowboy/", _/bits >> -> ok
end
end} || P <- Tests].
bad_path_win32_check_test_() ->
Tests = case os:type() of
{unix, _} ->
[];
{win32, _} ->
[
<<"c:/home/cowboy/../../secretfile.bat">>,
<<"c:/home/cowboy/c:/secretfile.bat">>,
<<"c:/home/cowboy/..\\..\\secretfile.bat">>,
<<"c:/home/cowboy/c:\\secretfile.bat">>
]
end,
[{P, fun() ->
error = case fullpath(P) of
<< "c:/home/cowboy/", _/bits >> -> ok;
_ -> error
end
end} || P <- Tests].
-endif.
%% Reject requests that tried to access a file outside
%% the target directory.
-spec malformed_request(Req, State)
-> {boolean(), Req, State}.
malformed_request(Req, State) ->
{State =:= error, Req, State}.
%% Directories, files that can't be accessed at all and
%% files with no read flag are forbidden.
-spec forbidden(Req, State)
-> {boolean(), Req, State}
when State::state().
forbidden(Req, State={_, {ok, #file_info{type=directory}}, _}) ->
{true, Req, State};
forbidden(Req, State={_, {error, eacces}, _}) ->
{true, Req, State};
forbidden(Req, State={_, {ok, #file_info{access=Access}}, _})
when Access =:= write; Access =:= none ->
{true, Req, State};
forbidden(Req, State) ->
{false, Req, State}.
%% Detect the mimetype of the file.
-spec content_types_provided(Req, State)
-> {[{binary(), get_file}], Req, State}
when State::state().
content_types_provided(Req, State={Path, _, Extra}) ->
case lists:keyfind(mimetypes, 1, Extra) of
false ->
{[{cow_mimetypes:web(Path), get_file}], Req, State};
{mimetypes, Module, Function} ->
{[{Module:Function(Path), get_file}], Req, State};
{mimetypes, Type} ->
{[{Type, get_file}], Req, State}
end.
%% Assume the resource doesn't exist if it's not a regular file.
-spec resource_exists(Req, State)
-> {boolean(), Req, State}
when State::state().
resource_exists(Req, State={_, {ok, #file_info{type=regular}}, _}) ->
{true, Req, State};
resource_exists(Req, State) ->
{false, Req, State}.
%% Generate an etag for the file.
-spec generate_etag(Req, State)
-> {{strong | weak, binary()}, Req, State}
when State::state().
generate_etag(Req, State={Path, {ok, #file_info{size=Size, mtime=Mtime}},
Extra}) ->
case lists:keyfind(etag, 1, Extra) of
false ->
{generate_default_etag(Size, Mtime), Req, State};
{etag, Module, Function} ->
{Module:Function(Path, Size, Mtime), Req, State};
{etag, false} ->
{undefined, Req, State}
end.
generate_default_etag(Size, Mtime) ->
{strong, integer_to_binary(erlang:phash2({Size, Mtime}, 16#ffffffff))}.
%% Return the time of last modification of the file.
-spec last_modified(Req, State)
-> {calendar:datetime(), Req, State}
when State::state().
last_modified(Req, State={_, {ok, #file_info{mtime=Modified}}, _}) ->
{Modified, Req, State}.
%% Stream the file.
-spec get_file(Req, State)
-> {{sendfile, 0, non_neg_integer(), binary()}, Req, State}
when State::state().
get_file(Req, State={Path, {ok, #file_info{size=Size}}, _}) ->
{{sendfile, 0, Size, Path}, Req, State}.
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