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Native support for cross-site scripting (XSS) in an nginx
C Perl Shell Ragel in Ruby Host

tests: disabled the test cases exercising multiple http {} blocks sin…

…ce this undocumented feature has been disabled since nginx 1.9.3.
latest commit 97c213962f
@agentzh agentzh authored

README.md

Name

xss-nginx-module - Native cross-site scripting support in nginx

Table of Contents

Synopsis

# accessing /foo?callback=process gives the response
# body "process(...);" (without quotes) where "..."
# is the original response body of the /foo location.
server {
    location /foo {
        # your content handler goes here...

        xss_get on;
        xss_callback_arg 'callback';
        xss_input_types 'application/json'; # default
        xss_output_type 'application/x-javascript'; # default
    }
    ...
}

Description

This module adds cross-site AJAX support to nginx. Currently only cross-site GET is supported. But cross-site POST will be added in the future.

The cross-site GET is currently implemented as JSONP (or "JSON with padding"). See http://en.wikipedia.org/wiki/JSON#JSONP for more details.

Directives

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xss_get

syntax: xss_get on | off

default: xss_get off

context: http, server, location, if location

Enables JSONP support for GET requests.

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xss_callback_arg

syntax: xss_callback_arg <name>

default: none

context: http, http, location, if location

Specifies the JavaScript callback function name used in the responses.

For example,

location /foo {
    xss_get on;
    xss_callback_arg c;
    ...
}

then

GET /foo?c=blah

returns

blah(...);

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xss_override_status

syntax: xss_override_status on | off

default: xss_check_status on

context: http, server, location, if location

Specifies whether to override 30x, 40x and 50x status to 200 when the response is actually being processed.

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xss_check_status

syntax: xss_check_status on | off

default: xss_check_status on

context: http, server, location, if location

By default, ngx_xss only process responses with the status code 200 or 201.

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xss_input_types

syntax: xss_input_types [mime-type]...

default: xss_input_types application/json

context: http, server, location, if location

Only processes the responses of the specified MIME types.

Example:

xss_input_types application/json text/plain;

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Limitations

  • ngx_xss will not work with ngx_echo's subrequest interfaces, due to the underlying limitations imposed by subrequests' "postponed chain" mechanism in the nginx core. The standard ngx_addition module also falls into this category. You're recommended, however, to use ngx_lua as the content handler to issue subrequests and ngx_xss to do JSONP, because ngx_lua's ngx.location.capture() interface does not utilize the "postponed chain" mechanism, thus getting out of this limitation. We're taking this approach in production and it works great.

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Trouble Shooting

Use the "info" error log level (or lower) to get more diagnostics when things go wrong.

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Installation

You're recommended to install this module (as well as the Nginx core and many other goodies) via the ngx_openresty bundle. See the detailed instructions for downloading and installing ngx_openresty into your system. This is the easiest and most safe way to set things up.

Alternatively, you can install this module manually with the Nginx source:

Grab the nginx source code from nginx.org, for example, the version 1.7.10 (see nginx compatibility), and then build the source with this module:

 $ wget 'http://nginx.org/download/nginx-1.7.10.tar.gz'
 $ tar -xzvf nginx-1.7.10.tar.gz
 $ cd nginx-1.7.10/

 # Here we assume you would install you nginx under /opt/nginx/.
 $ ./configure --prefix=/opt/nginx \
     --add-module=/path/to/rds-json-nginx-module

 $ make -j2
 $ make install

Download the latest version of the release tarball of this module from xss-nginx-module file list.

Also, this module is included and enabled by default in the ngx_openresty bundle.

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Compatibility

The following versions of Nginx should work with this module:

  • 1.7.x (last tested: 1.7.10)
  • 1.6.x
  • 1.5.x
  • 1.4.x (last tested: 1.4.3)
  • 1.2.x (last tested: 1.2.9)
  • 1.0.x (last tested: 1.0.10)
  • 0.9.x (last tested: 0.9.4)
  • 0.8.x (last tested: 0.8.54)
  • 0.7.x >= 0.7.30 (last tested: 0.7.67)

Earlier versions of Nginx like 0.6.x and 0.5.x will not work.

If you find that any particular version of Nginx above 0.7.30 does not work with this module, please consider reporting a bug.

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TODO

  • add cross-site POST support.

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Author

Yichun "agentzh" Zhang (章亦春) <agentzh@gmail@com>

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Copyright & License

The implementation of the builtin connection pool has borrowed a lot of code from Maxim Dounin's upstream_keepalive module. This part of code is copyrighted by Maxim Dounin.

This module is licenced under the BSD license.

Copyright (C) 2009-2015 by Yichun "agentzh" Zhang (章亦春) <agentzh@gmail.com>.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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See Also

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