aboutsummaryrefslogtreecommitdiffstats
path: root/src/cowboy_static.erl
blob: d6ef45c3f6ef425fb2ffbba083059965583218ba (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
%% 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([charsets_provided/2]).
-export([ranges_provided/2]).
-export([resource_exists/2]).
-export([last_modified/2]).
-export([generate_etag/2]).
-export([get_file/2]).

-type extra_charset() :: {charset, module(), function()} | {charset, binary()}.
-type extra_etag() :: {etag, module(), function()} | {etag, false}.
-type extra_mimetypes() :: {mimetypes, module(), function()}
	| {mimetypes, binary() | {binary(), binary(), [{binary(), binary()}]}}.
-type extra() :: [extra_charset() | 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(), {direct | archive, #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}) ->
	{PrivPath, HowToAccess} = priv_path(App, Path),
	init_info(Req, absname(PrivPath), HowToAccess, Extra);
init_opts(Req, {file, Path, Extra}) ->
	init_info(Req, absname(Path), direct, Extra);
init_opts(Req, {priv_dir, App, Path, Extra}) ->
	{PrivPath, HowToAccess} = priv_path(App, Path),
	init_dir(Req, PrivPath, HowToAccess, Extra);
init_opts(Req, {dir, Path, Extra}) ->
	init_dir(Req, Path, direct, 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,
				how_to_access_app_priv(PrivDir)
			};
		PrivDir when is_binary(Path) ->
			{
				<< (list_to_binary(PrivDir))/binary, $/, Path/binary >>,
				how_to_access_app_priv(PrivDir)
			}
	end.

how_to_access_app_priv(PrivDir) ->
	%% If the priv directory is not a directory, it must be
	%% inside an Erlang application .ez archive. We call
	%% how_to_access_app_priv1() to find the corresponding archive.
	case filelib:is_dir(PrivDir) of
		true  -> direct;
		false -> how_to_access_app_priv1(PrivDir)
	end.

how_to_access_app_priv1(Dir) ->
	%% We go "up" by one path component at a time and look for a
	%% regular file.
	Archive = filename:dirname(Dir),
	case Archive of
		Dir ->
			%% filename:dirname() returned its argument:
			%% we reach the root directory. We found no
			%% archive so we return 'direct': the given priv
			%% directory doesn't exist.
			direct;
		_ ->
			case filelib:is_regular(Archive) of
				true  -> {archive, Archive};
				false -> how_to_access_app_priv1(Archive)
			end
	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, HowToAccess, Extra) when is_list(Path) ->
	init_dir(Req, list_to_binary(Path), HowToAccess, Extra);
init_dir(Req, Path, HowToAccess, Extra) ->
	Dir = fullpath(filename:absname(Path)),
	PathInfo = cowboy_req:path_info(Req),
	Filepath = filename:join([Dir|escape_reserved(PathInfo)]),
	Len = byte_size(Dir),
	case fullpath(Filepath) of
		<< Dir:Len/binary, $/, _/binary >> ->
			init_info(Req, Filepath, HowToAccess, Extra);
		<< Dir:Len/binary >> ->
			init_info(Req, Filepath, HowToAccess, Extra);
		_ ->
			{cowboy_rest, Req, error}
	end.

escape_reserved([]) -> [];
escape_reserved([P|Tail]) -> [escape_reserved(P, <<>>)|escape_reserved(Tail)].

%% 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, HowToAccess, Extra) ->
	Info = read_file_info(Path, HowToAccess),
	{cowboy_rest, Req, {Path, Info, Extra}}.

read_file_info(Path, direct) ->
	case file:read_file_info(Path, [{time, universal}]) of
		{ok, Info} -> {direct, Info};
		Error      -> Error
	end;
read_file_info(Path, {archive, Archive}) ->
	case file:read_file_info(Archive, [{time, universal}]) of
		{ok, ArchiveInfo} ->
			%% The Erlang application archive is fine.
			%% Now check if the requested file is in that
			%% archive. We also need the file_info to merge
			%% them with the archive's one.
			PathS = binary_to_list(Path),
			case erl_prim_loader:read_file_info(PathS) of
				{ok, ContainedFileInfo} ->
					Info = fix_archived_file_info(
						ArchiveInfo,
						ContainedFileInfo),
					{archive, Info};
				error ->
					{error, enoent}
			end;
		Error ->
			Error
	end.

fix_archived_file_info(ArchiveInfo, ContainedFileInfo) ->
	%% We merge the archive and content #file_info because we are
	%% interested by the timestamps of the archive, but the type and
	%% size of the contained file/directory.
	%%
	%% We reset the access to 'read', because we won't rewrite the
	%% archive.
	ArchiveInfo#file_info{
		size = ContainedFileInfo#file_info.size,
		type = ContainedFileInfo#file_info.type,
		access = read
	}.

-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={_, {_, #file_info{type=directory}}, _}) ->
	{true, Req, State};
forbidden(Req, State={_, {error, eacces}, _}) ->
	{true, Req, State};
forbidden(Req, State={_, {_, #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}) when is_list(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.

%% Detect the charset of the file.

-spec charsets_provided(Req, State)
	-> {[binary()], Req, State}
	when State::state().
charsets_provided(Req, State={Path, _, Extra}) ->
	case lists:keyfind(charset, 1, Extra) of
		%% We simulate the callback not being exported.
		false ->
			no_call;
		{charset, Module, Function} ->
			{[Module:Function(Path)], Req, State};
		{charset, Charset} when is_binary(Charset) ->
			{[Charset], Req, State}
	end.

%% Enable support for range requests.

-spec ranges_provided(Req, State)
	-> {[{binary(), auto}], Req, State}
	when State::state().
ranges_provided(Req, State) ->
	{[{<<"bytes">>, auto}], Req, State}.

%% 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={_, {_, #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, {_, #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={_, {_, #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, {direct, #file_info{size=Size}}, _}) ->
	{{sendfile, 0, Size, Path}, Req, State};
get_file(Req, State={Path, {archive, _}, _}) ->
	PathS = binary_to_list(Path),
	{ok, Bin, _} = erl_prim_loader:get_file(PathS),
	{Bin, Req, State}.