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riak_cs_s3_rewrite.erl
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riak_cs_s3_rewrite.erl
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%% ---------------------------------------------------------------------
%%
%% Copyright (c) 2007-2015 Basho Technologies, Inc. All Rights Reserved.
%%
%% This file is provided to you under the Apache License,
%% Version 2.0 (the "License"); you may not use this file
%% except in compliance with the License. You may obtain
%% a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing,
%% software distributed under the License is distributed on an
%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
%% KIND, either express or implied. See the License for the
%% specific language governing permissions and limitations
%% under the License.
%%
%% ---------------------------------------------------------------------
%% @doc Rewrite rule of Riak CS S3 API. Following diagram is overall url quote/unquote diagram
%% in case of hosted path style object names. Bucket names are much different in case of path
%% style; they won't be doubly escaped.
%%
%% quote state RAW escaped(1) escaped(2) example
%%
%% * 'baz/foo bar' 'baz/foo+bar'
%% client app +--------+ 'baz/foo%20bar' 'baz/foo%2Bbar'
%% |
%% HTTP |
%% |
%% webmachine |
%% before rewrite |
%% rewrite +------------+ 'baz%2Ffoo%2520bar' 'baz%2Ffoo%252Bbar'
%% after rewrite |
%% |
%% extract_key +---------------------+
%% |
%% v
%% * 'baz/foo bar' 'baz/foo+bar'
-module(riak_cs_s3_rewrite).
-export([rewrite/5, original_resource/1, raw_url/1]).
-export([rewrite_path_and_headers/5]).
-include("riak_cs.hrl").
-include("s3_api.hrl").
-define(RCS_REWRITE_HEADER, "x-rcs-rewrite-path").
-define(RCS_RAW_URL_HEADER, "x-rcs-raw-url").
-ifdef(TEST).
-compile(export_all).
-endif.
-type subresource() :: {string(), string()}.
-type query_params() :: [{string(), string()}].
-type subresources() :: [subresource()].
%% @doc Function to rewrite headers prior to processing by webmachine.
-spec rewrite(atom(), atom(), {integer(), integer()}, gb_tree(), string()) ->
{gb_tree(), string()}.
rewrite(Method, _Scheme, _Vsn, Headers, Url) ->
riak_cs_dtrace:dt_wm_entry(?MODULE, <<"rewrite">>),
{Path, QueryString, _} = mochiweb_util:urlsplit_path(Url),
rewrite_path_and_headers(Method, Headers, Url, Path, QueryString).
-spec original_resource(term()) -> undefined | {string(), [{term(),term()}]}.
original_resource(RD) ->
case wrq:get_req_header(?RCS_REWRITE_HEADER, RD) of
undefined -> undefined;
RawPath ->
{Path, QS, _} = mochiweb_util:urlsplit_path(RawPath),
{Path, mochiweb_util:parse_qs(QS)}
end.
-spec raw_url(term()) -> undefined | {string(), [{term(), term()}]}.
raw_url(RD) ->
case wrq:get_req_header(?RCS_RAW_URL_HEADER, RD) of
undefined -> undefined;
RawUrl ->
{Path, QS, _} = mochiweb_util:urlsplit_path(RawUrl),
{Path, mochiweb_util:parse_qs(QS)}
end.
-spec rewrite_path_and_headers(atom(), gb_tree(), string(), string(), string()) ->
{gb_tree(), string()}.
rewrite_path_and_headers(Method, Headers, Url, Path, QueryString) ->
Host = mochiweb_headers:get_value("host", Headers),
HostBucket = bucket_from_host(Host),
RewrittenPath = rewrite_path(Method,
Path,
QueryString,
HostBucket),
RewrittenHeaders = mochiweb_headers:default(
?RCS_RAW_URL_HEADER, Url,
mochiweb_headers:default(?RCS_REWRITE_HEADER,
rcs_rewrite_header(Url, HostBucket),
Headers)),
{RewrittenHeaders, RewrittenPath}.
%% @doc Internal function to handle rewriting the URL
-spec rewrite_path(atom(),string(), string(), undefined | string()) -> string().
rewrite_path(_Method, "/", _QS, undefined) ->
"/buckets";
rewrite_path(Method, Path, QS, undefined) ->
{Bucket, UpdPath} = separate_bucket_from_path(Path),
rewrite_path(Method, UpdPath, QS, mochiweb_util:unquote(Bucket));
rewrite_path(_Method, Path, _QS, "riak-cs") ->
"/riak-cs" ++ Path;
rewrite_path(_Method, Path, _QS, "usage") ->
"/usage" ++ Path;
rewrite_path(Method, "/", [], Bucket) when Method =/= 'GET' ->
lists:flatten(["/buckets/", Bucket]);
rewrite_path(Method, "/", QS, Bucket) ->
{SubResources, QueryParams} = get_subresources(QS),
lists:flatten(["/buckets/", Bucket, format_bucket_qs(Method,
QueryParams,
SubResources)]);
rewrite_path(_Method, Path, QS, Bucket) ->
lists:flatten(["/buckets/",
Bucket,
"/objects/",
mochiweb_util:quote_plus(string:strip(Path, left, $/)),
format_object_qs(get_subresources(QS))
]).
%% @doc, build the path to be stored as the rewritten path in the request. Bucket name
%% from the host header is added if it exists.
rcs_rewrite_header(RawPath, undefined) ->
RawPath;
rcs_rewrite_header(RawPath, Bucket) ->
"/" ++ Bucket ++ RawPath.
%% @doc Extract the bucket name that may have been prepended to the
%% host name in the Host header value.
-spec bucket_from_host(undefined | string()) -> undefined | string().
bucket_from_host(undefined) ->
riak_cs_dtrace:dt_wm_entry(?MODULE, <<"bucket_from_host">>),
undefined;
bucket_from_host(HostHeader) ->
riak_cs_dtrace:dt_wm_entry(?MODULE, <<"bucket_from_host">>),
{ok, RootHost} = application:get_env(riak_cs, cs_root_host),
bucket_from_host(HostHeader, RootHost).
bucket_from_host(HostHeader, RootHost) ->
HostNoPort = case string:tokens(HostHeader, ":") of
[] -> HostHeader;
[H|_] -> H
end,
extract_bucket_from_host(HostNoPort,
string:rstr(HostNoPort, RootHost)).
%% @doc Extract the bucket name from the `Host' header value if a
%% bucket name is present.
-spec extract_bucket_from_host(string(), non_neg_integer()) -> undefined | string().
extract_bucket_from_host(_Host, 0) ->
undefined;
extract_bucket_from_host(_Host, 1) ->
undefined;
extract_bucket_from_host(Host, RootHostIndex) ->
%% Take the substring of the everything up to
%% the '.' preceding the root host
string:sub_string(Host, 1, RootHostIndex-2).
%% @doc Separate the bucket name from the rest of the raw path in the
%% case where the bucket name is included in the path.
-spec separate_bucket_from_path(string()) -> {nonempty_string(), string()}.
separate_bucket_from_path([$/ | Rest]) ->
separate_bucket_from_path(Rest, []).
separate_bucket_from_path([], Acc) ->
{lists:reverse(Acc), "/"};
separate_bucket_from_path([$/ | _] = Path, Acc) ->
{lists:reverse(Acc), Path};
separate_bucket_from_path([C | Rest], Acc) ->
separate_bucket_from_path(Rest, [C | Acc]).
%% @doc Format a bucket operation query string to conform the the
%% rewrite rules.
-spec format_bucket_qs(atom(), query_params(), subresources()) -> string().
format_bucket_qs('POST', [{"delete", []}], []) ->
"/delete";
format_bucket_qs(Method, QueryParams, [])
when Method =:= 'GET'; Method =:= 'POST' ->
["/objects",
format_query_params(QueryParams)];
format_bucket_qs(_Method, QueryParams, SubResources) ->
[format_subresources(SubResources),
format_query_params(QueryParams)].
%% @doc Format an object operation query string to conform the the
%% rewrite rules.
-spec format_object_qs({subresources(), query_params()}) -> string().
format_object_qs({SubResources, QueryParams}) ->
UploadId = proplists:get_value("uploadId", SubResources, []),
PartNum = proplists:get_value("partNumber", SubResources, []),
format_object_qs(SubResources, QueryParams, UploadId, PartNum).
%% @doc Format an object operation query string to conform the the
%% rewrite rules.
-spec format_object_qs(subresources(), query_params(), string(), string()) -> string().
format_object_qs(SubResources, QueryParams, [], []) ->
[format_subresources(SubResources), format_query_params(QueryParams)];
format_object_qs(_SubResources, QueryParams, UploadId, []) ->
["/uploads/", UploadId, format_query_params(QueryParams)];
format_object_qs(_SubResources, QueryParams, UploadId, PartNum) ->
["/uploads/", UploadId, format_query_params([{"partNumber", PartNum} | QueryParams])].
%% @doc Format a string that expresses the subresource request
%% that can be appended to the URL.
-spec format_subresources(subresources()) -> string().
format_subresources([]) ->
[];
format_subresources([{Key, []} | _]) ->
["/", Key].
%% @doc Format a proplist of query parameters into a string
-spec format_query_params(query_params()) -> iolist().
format_query_params([]) ->
[];
format_query_params(QueryParams) ->
format_query_params(QueryParams, []).
%% @doc Format a proplist of query parameters into a string
-spec format_query_params(query_params(), iolist()) -> iolist().
format_query_params([], QS) ->
["?", QS];
format_query_params([{Key, []} | RestParams], []) ->
format_query_params(RestParams, [Key]);
format_query_params([{Key, []} | RestParams], QS) ->
format_query_params(RestParams, [[Key, "&"] | QS]);
format_query_params([{Key, Value} | RestParams], []) ->
format_query_params(RestParams, [Key, "=", mochiweb_util:quote_plus(Value)]);
format_query_params([{Key, Value} | RestParams], QS) ->
format_query_params(RestParams, [[Key, "=", mochiweb_util:quote_plus(Value), "&"] | QS]).
%% @doc Parse the valid subresources from the raw path.
-spec get_subresources(string()) -> {subresources(), query_params()}.
get_subresources(QueryString) ->
lists:partition(fun valid_subresource/1, mochiweb_util:parse_qs(QueryString)).
%% @doc Determine if a query parameter key is a valid S3 subresource
-spec valid_subresource(subresource()) -> boolean().
valid_subresource({Key, _}) ->
lists:member(Key, ?SUBRESOURCES).