.. _admin-plugins-s3-auth:

AWS S3 Authentication plugin
****************************

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This is a plugin for Apache Traffic Server that provides support for the
``Amazon S3`` authentication features. This is useful if you for example want
to use ``S3`` as your origin server, yet want to avoid direct user access to
the content.

Using the plugin
================


Using the plugin in a remap rule would be e.g.::

   # remap.config

   ...  @plugin=s3_auth.so @pparam=--access_key @pparam=my-key \
                           @pparam=--secret_key @pparam=my-secret \
                           @pparam=--session_token @pparam=my-token \
                           @pparam=--virtual_host


Alternatively, you can store the access key and secret in an external configuration file, and point the remap rule(s) to it::

   # remap.config

   ...  @plugin=s3_auth.so @pparam=--config @pparam=s3_auth_v2.config


Where ``s3.config`` could look like::

    # s3_auth_v2.config

    access_key=my-key
    secret_key=my-secret
    version=2
    virtual_host=yes

Both ways could be combined as well


AWS Authentication version 4
============================

The s3_auth plugin fully implements: `AWS Signing Version 4 <http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html>`_ / `Authorization Header <http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-auth-using-authorization-header.html>`_ / `Transferring Payload in a Single Chunk <http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html>`_ / Unsigned Payload Option

Configuration options::

    # Mandatory options
    --access_key=<access_id>
    --secret_key=<key>
    --version=4

    # Optional
    --session_token=<token>
    --v4-include-headers=<comma-separated-list-of-headers-to-be-signed>
    --v4-exclude-headers=<comma-separated-list-of-headers-not-to-be-signed>
    --v4-region-map=region_map.config


If the following option is used then the options could be specified in a file::

    --config=s3_auth_v4.config


The ``s3_auth_v4.config`` config file could look like this::

    # s3_auth_v4.config

    access_key=<access_id>
    secret_key=<secret_key>
    session_token=<token>
    version=4
    v4-include-headers=<comma-separated-list-of-headers-to-be-signed>
    v4-exclude-headers=<comma-separated-list-of-headers-not-to-be-signed>
    v4-region-map=region_map.config

Where the ``region_map.config`` defines the entry-point hostname to region mapping i.e.::

    # region_map.config

    # "us-east-1"
    s3.amazonaws.com                     : us-east-1
    s3-external-1.amazonaws.com          : us-east-1
    s3.dualstack.us-east-1.amazonaws.com : us-east-1

    # us-west-1
    s3-us-west-1.amazonaws.com           : us-west-1
    s3.dualstack.us-west-1.amazonaws.com : us-west-1

    # Default region if no entry-point matches:
    : s3.amazonaws.com

If ``--v4-region-map`` is not specified the plugin defaults to the mapping defined in `"Regions and Endpoints - S3" <http://docs.aws.amazon.com/general/latest/gr/rande.html#s3_region>`_

According to `Transferring Payload in a Single Chunk <http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html>`_ specification
the ``CanonicalHeaders`` list *must* include the ``Host`` header,  the ``Content-Type`` header if present in the request and all the ``x-amz-*`` headers
so ``--v4-include-headers`` and ``--v4-exclude-headers`` do not impact those headers and they are *always* signed.

The ``Via`` and ``X-Forwarded-For`` headers are *always* excluded from the signature since they are meant to be changed by the proxies and signing them could lead to invalidation of the signature.

If ``--v4-include-headers`` is not specified all headers except those specified in ``--v4-exclude-headers`` will be signed.

If ``--v4-include-headers`` is specified only the headers specified will be signed except those specified in ``--v4-exclude-headers``


AWS Authentication version 2
============================

For more details on the S3 auth version 2 , see: `Signing and Authenticating REST Requests <http://docs.aws.amazon.com/AmazonS3/latest/dev/RESTAuthentication.html>`_


There are 4 plugin configuration options for version 2::

    --access_key    <access_id>
    --secret_key    <secret_key>
    --virtual_host
    --config        <config file>
    --version=2

This is a pretty bare bone start for the S3 services, it is missing a number of features:

- It does not do UTF8 encoding (as required)
- It does not deal with canonicalization of AMZ headers.
- It does not handle POST requests (but do we need to ?)
- It does not incorporate query parameters.
- It does not support session tokens.


Contributions to any of these would be appreciated.