===========
Credentials
===========

In order to authenticate requests, AWS services require you to provide your
`AWS access keys <http://aws.amazon.com/developers/access-keys/>`_, also known
as your AWS **access key ID** and **secret access key**. In the AWS SDK for
PHP, these access keys are often referred to collectively as your
**credentials**. This guide demonstrates how to provide your credentials to the
AWS SDK for SDK using one of the following methods:

#. :ref:`environment_credentials`
#. :ref:`instance_profile_credentials`
#. :ref:`ecs_credentials`
#. :ref:`credential_profiles`
#. :ref:`hardcoded_credentials`
#. :ref:`credential_provider`
#. :ref:`temporary_credentials`
#. :ref:`assume_role_credentials`

In general, it is recommended that you use IAM roles when running your
application on Amazon EC2 and use credential profiles or environment variables
elsewhere. Regardless of how you supply credentials to the SDK, it is encouraged that
you follow the `IAM Best Practices <http://docs.aws.amazon.com/IAM/latest/UserGuide/IAMBestPractices.html>`_
when managing your credentials.


.. _environment_credentials:

Using credentials from environment variables
--------------------------------------------

If you do not provide credentials to a client object at the time of its
instantiation, the SDK will attempt to find credentials in your environment.
The first place the SDK will check for credentials is in your environment
variables. The SDK will use the ``getenv()`` function function to look for the
``AWS_ACCESS_KEY_ID``, ``AWS_SECRET_ACCESS_KEY``, and ``AWS_SESSION_TOKEN``
environment variables. These credentials are referred to as
**environment credentials**.


.. _instance_profile_credentials:

Using IAM roles for Amazon EC2 instances
----------------------------------------

*Using IAM roles is the preferred technique for providing credentials to
applications running on Amazon EC2.* IAM roles remove the need to worry about
credential management from your application. They allow an instance to "assume"
a role by retrieving temporary credentials from the EC2 instance's metadata
server. These temporary credentials, often referred to as
**instance profile credentials**, allow access to the actions and resources
that the role's policy allows.

When launching an EC2 instance, you can choose to associate it with an IAM
role. Any application running on that EC2 instance is then allowed to assume
the associated role. Amazon EC2 handles all the legwork of securely
authenticating instances to the IAM service to assume the role and periodically
refreshing the retrieved role credentials, keeping your application secure with
almost no work on your part.

If you do not explicitly provide credentials to the client object and no
environment variable credentials are available, the SDK attempts to retrieve
instance profile credentials from an Amazon EC2 instance metadata server. These
credentials are available only when running on Amazon EC2 instances that have
been configured with an IAM role.

.. note::

    Instance profile credentials and other temporary credentials generated by
    the AWS Security Token Service (AWS STS) are not supported by every
    service. Please check if the service you are using supports temporary
    credentials by reading `AWS Services that Support AWS STS <http://docs.aws.amazon.com/STS/latest/UsingSTS/UsingTokens.html>`_.

    To Avoid hitting metadata service every time, an instance of ``Aws\CacheInterface``
    can be passed in as the ``'credentials'`` option to a client constructor. This lets SDK
    use cached instance profile credentials instead. For more information, see ``'credentials'`` `option <http://docs.aws.amazon.com/aws-sdk-php/v3/guide/guide/configuration.html#credentials>`_.

For more information, see `IAM Roles for Amazon EC2 <http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html>`_.


.. _ecs_credentials:

Using IAM roles for Amazon EC2 Container Service Tasks
------------------------------------------------------

*With IAM roles for Amazon ECS tasks, you can specify an IAM role that can be
used by the containers in a task.* This provides a strategy for managing credentials
for your applications to use, similar to the way that Amazon EC2 instance profiles
provide credentials to EC2 instances.

Instead of creating and distributing your AWS credentials to the containers or
using the EC2 instance’s role, you can associate an IAM role with an ECS task definition or
``RunTask`` `API <http://docs.aws.amazon.com/aws-sdk-php/v3/api/api-ecs-2014-11-13.html#runtask>`_ operation.

.. note::

    Instance profile credentials and other temporary credentials generated by
    the AWS Security Token Service (AWS STS) are not supported by every
    service. Please check if the service you are using supports temporary
    credentials by reading `AWS Services that Support AWS STS <http://docs.aws.amazon.com/STS/latest/UsingSTS/UsingTokens.html>`_.

For more information, see `IAM Roles for Amazon EC2 Container Service Tasks <http://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-iam-roles.html>`_.


.. _assume_role_credentials:

Using Assume Role Credentials
-----------------------------

Using ``Aws\Credentials\AssumeRoleCredentialProvider`` to create credentials by assuming a role,
you would need to provide ``'client'`` information with a ``StsClient`` object and
``'assume_role_params'`` details.

For more information regarding ``'assume_role_params'``, see `AssumeRole <http://docs.aws.amazon.com/aws-sdk-php/v3/api/api-sts-2011-06-15.html#assumerole>`_.

.. code-block:: php

    $assumeRoleCredentials = new AssumeRoleCredentialProvider([
        'client' => new StsClient([
            'region' => 'us-west-2',
            'version' => '2011-06-15'
        ]),
        'assume_role_params' => [
            'RoleArn' => '<string>', // REQUIRED
            'RoleSessionName' => '<string>', // REQUIRED
            ...
        ]
    ]);

.. _credential_profiles:

Using the AWS credentials file and credential profiles
------------------------------------------------------

Starting with the AWS SDK for PHP version 2.6.2, you can use an AWS credentials
file to specify your credentials. This is a special, INI-formatted file stored
under your HOME directory, and is a good way to manage credentials for your
development environment. The file should be placed at ``~/.aws/credentials``,
where ``~`` represents your HOME directory.

Using an AWS credentials file offers a few benefits:

1. Your projects' credentials are stored outside of your projects, so there is
   no chance of accidentally committing them into version control.
2. You can define and name multiple sets of credentials in one place.
3. You can easily reuse the same credentials between projects.
4. Other AWS SDKs and tools support, or will soon support, this same
   credentials file. This allows you to reuse your credentials with other
   tools.

The format of the AWS credentials file should look something like the
following:

.. code-block:: ini

    [default]
    aws_access_key_id = YOUR_AWS_ACCESS_KEY_ID
    aws_secret_access_key = YOUR_AWS_SECRET_ACCESS_KEY

    [project1]
    aws_access_key_id = ANOTHER_AWS_ACCESS_KEY_ID
    aws_secret_access_key = ANOTHER_AWS_SECRET_ACCESS_KEY

Each section (e.g., ``[default]``, ``[project1]``), represents a separate
credential **profile**. Profiles can be referenced from a SDK configuration
file, or when you are instantiating a client, using the ``profile`` option:

.. code-block:: php

    <?php

    use Aws\DynamoDb\DynamoDbClient;

    // Instantiate a client with the credentials from the project1 profile
    $client = new DynamoDbClient([
        'profile' => 'project1',
        'region'  => 'us-west-2',
        'version' => 'latest'
    ]);

If no credentials or profiles were explicitly provided to the SDK and no
credentials were defined in environment variables, but a credentials file is
defined, the SDK will use the "default" profile. You can change the default
profile by specifying an alternate profile name in the ``AWS_PROFILE``
environment variable.


.. _hardcoded_credentials:

Using hard-coded credentials
----------------------------

You can provide hard-coded credentials to a SDK client by providing the "key",
"secret", and optional "token" key value pairs to the "credentials" option of
a client constructor.

.. code-block:: php

    $s3Client = new S3Client([
        'version'     => 'latest',
        'region'      => 'us-west-2',
        'credentials' => [
            'key'    => 'my-access-key-id',
            'secret' => 'my-secret-access-key',
        ],
    ]);

.. warning::

    Hard-coding your credentials can be dangerous, because it is easy to
    accidentally commit your credentials into an SCM repository, potentially
    exposing your credentials to more people than intended. It can also make it
    difficult to rotate credentials in the future.


.. _credential_provider:

Using a credential provider
---------------------------

A credential provider is a function that returns a ``GuzzleHttp\Promise\PromiseInterface``
that is fulfilled with an ``Aws\Credentials\CredentialsInterface`` instance or
rejected with an ``Aws\Exception\CredentialsException``. You can use credential
providers to implement your own custom logic for creating credentials or to
optimize credential loading.

Credential providers are passed into the ``credentials`` client constructor
option. Credential providers are asynchronous, which forces them to be lazily
evaluated each time an API operation is invoked. As such, passing in a
credential provider function to an SDK client constructor will not immediately
validate the credentials. If the credential provider does not return a
credentials object, an API operation will be rejected with an
``Aws\Exception\CredentialsException``.

.. code-block:: php

    use Aws\Credentials\CredentialProvider;
    use Aws\S3\S3Client;

    // Use the default credential provider
    $provider = CredentialProvider::defaultProvider();

    // Pass the provider to the client.
    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => '2006-03-01',
        'credentials' => $provider
    ]);

The SDK ships with several built-in providers that can be combined together
along with any custom providers.

.. important::

    Credential providers are invoked every time an API operation is performed.
    If loading credentials is an expensive task (e.g., loading from disk or a
    network resource) or if credentials are not cached by your provider, then
    you should consider wrapping your credential provider in an
    ``Aws\Credentials\CredentialProvider::memoize`` function. The default
    credential provider used by the SDK is automatically memoized.


env provider
~~~~~~~~~~~~

``Aws\Credentials\CredentialProvider::env`` attempts to load credentials from
environment variables.

.. code-block:: php

    use Aws\Credentials\CredentialProvider;
    use Aws\S3\S3Client;

    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => '2006-03-01',
        'credentials' => CredentialProvider::env()
    ]);


ini provider
~~~~~~~~~~~~

``Aws\Credentials\CredentialProvider::ini`` attempts to load credentials from
an :ref:`ini credential file <credential_profiles>`. The SDK will by default
attempt to load the "default" profile from a file located at
``~/.aws/credentials``.

.. code-block:: php

    use Aws\Credentials\CredentialProvider;
    use Aws\S3\S3Client;

    $provider = CredentialProvider::ini();
    // Cache the results in a memoize function to avoid loading and parsing
    // the ini file on every API operation.
    $provider = CredentialProvider::memoize($provider);

    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => '2006-03-01',
        'credentials' => $provider
    ]);

You can use a custom profile or ini file location by providing arguments to
the function that creates the provider.

.. code-block:: php

    $profile = 'production';
    $path = '/full/path/to/credentials.ini';

    $provider = CredentialProvider::ini($profile, $path);
    $provider = CredentialProvider::memoize($provider);

    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => '2006-03-01',
        'credentials' => $provider
    ]);


instanceProfile provider
~~~~~~~~~~~~~~~~~~~~~~~~

``Aws\Credentials\CredentialProvider::instanceProfile`` attempts to load
credentials from Amazon EC2 instance profiles.

.. code-block:: php

    use Aws\Credentials\CredentialProvider;
    use Aws\S3\S3Client;

    $provider = CredentialProvider::instanceProfile();
    // Be sure to memoize the credentials
    $memoizedProvider = CredentialProvider::memoize($provider);

    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => '2006-03-01',
        'credentials' => $memoizedProvider
    ]);


ecsCredentials provider
~~~~~~~~~~~~~~~~~~~~~~

``Aws\Credentials\CredentialProvider::ecsCredentials`` attempts to load
credentials by a ``GET`` request, whose uri is specified by environment variable
``AWS_CONTAINER_CREDENTIALS_RELATIVE_URI`` in the container.

.. code-block:: php

    use Aws\Credentials\CredentialProvider;
    use Aws\S3\S3Client;

    $provider = CredentialProvider::ecsCredentials();
    // Be sure to memoize the credentials
    $memoizedProvider = CredentialProvider::memoize($provider);

    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => '2006-03-01',
        'credentials' => $memoizedProvider
    ]);

defaultProvider provider
~~~~~~~~~~~~~~~~~~~~~~~~

``Aws\Credentials\CredentialProvider::defaultProvider`` is the default
credential provider. This provider is used if you omit a ``credentials`` option
when creating a client. It first attempts to load credentials from environment
variables, then from an ini file (``.aws/credentials`` file first, followed by ``.aws/config`` file),
then from an instance profile (``EcsCredentials`` first, followed by ``Ec2`` metadata).

.. note::

    The result of the default provider is automatically memoized.

assumeRole provider
~~~~~~~~~~~~~~~~~~~

``Aws\Credentials\CredentialProvider::assumeRole`` is a credential provider
that creates credentials using assume role parameters and ``StsClient`` information.

.. note::

To avoid unnecessarily fetching STS credentials on every API operation, you can use
 ``memoize`` function that handles automatically refreshing the credentials when they expire.
See details with following example code.

.. code-block:: php

    use Aws\Credentials\CredentialProvider;
    use Aws\S3\S3Client;
    use Aws\Sts\StsClient;

    // Passing Aws\Credentials\AssumeRoleCredentialProvider options directly
    $provider = CredentialProvider::assumeRole([
        'client' => new StsClient(['region' => 'us-west-2', 'version' => 'latest']),
        'assume_role_params' => [
            'RoleArn' => 'arn:aws:iam::012345678910:role/role_name',
            'RoleSessionName' => 'test_session',
        ]
    ]);

    // To avoid unnecessarily fetching STS credentials on every API operation,
    // memoize function will handle automatically refreshing the credentials when they expire
    $provider = CredentialProvider::memoize($provider);

    $client = new S3Client([
        'region'      => 'us-west-2',
        'version'     => 'latest',
        'credentials' => $provider
    ]);

Creating a custom provider
~~~~~~~~~~~~~~~~~~~~~~~~~~

Credential providers are simply functions that when invoked return a promise
(``GuzzleHttp\Promise\PromiseInterface``) that is fulfilled with an
``Aws\Credentials\CredentialsInterface`` object or rejected with an
``Aws\Exception\CredentialsException``.

A best practice for creating providers is to create a function that is invoked
to create the actual credential provider. As an example, here's the source of
the ``env`` provider (slightly modified for example purposes). Notice that it
is a function that returns the actual provider function. This allows you to
easily compose credential providers and pass them around as values.

.. code-block:: php

    use GuzzleHttp\Promise;
    use GuzzleHttp\Promise\RejectedPromise;

    // This function CREATES a credential provider.
    public static function env()
    {
        // This function IS the credential provider.
        return function () {
            // Use credentials from environment variables, if available
            $key = getenv(self::ENV_KEY);
            $secret = getenv(self::ENV_SECRET);
            if ($key && $secret) {
                return Promise\promise_for(
                    new Credentials($key, $secret, getenv(self::ENV_SESSION))
                );
            }

            $msg = 'Could not find environment variable '
                . 'credentials in ' . self::ENV_KEY . '/' . self::ENV_SECRET;
            return new RejectedPromise(new CredentialsException($msg));
        };
    }


Memoizing Credentials
~~~~~~~~~~~~~~~~~~~~~

It is sometimes necessary to create a credential provider that remembers the
previous return value. This can be useful for performance when loading
credentials is an expensive operation or when using the ``Aws\Sdk`` class to
share a credential provider across multiple clients. You can add memoization to
a credential provider by wrapping the credential provider function in a
``memoize`` function:

.. code-block:: php

    use Aws\Credentials\CredentialProvider;

    $provider = CredentialProvider::instanceProfile();
    // Wrap the actual provider in a memoize function.
    $provider = CredentialProvider::memoize($provider);

    // Pass the provider into the Sdk class and share the provider
    // across multiple clients. Each time a new client is constructed,
    // it will use the previously returned credentials as long as
    // they have not yet expired.
    $sdk = new Aws\Sdk(['credentials' => $provider]);

    $s3 = $sdk->getS3(['region' => 'us-west-2', 'version' => 'latest']);
    $ec2 = $sdk->getEc2(['region' => 'us-west-2', 'version' => 'latest']);

    assert($s3->getCredentials() === $ec2->getCredentials());

When the memoized credentials become expired, the memoize wrapper will invoke
the wrapped provider in an attempt to refresh the credentials.


Chaining providers
~~~~~~~~~~~~~~~~~~

Credential providers can be chained using the
``Aws\Credentials\CredentialProvider::chain()`` function. This function accepts
a variadic number of arguments, each of which are credential provider
functions. This function then returns a new function that is the composition of
the provided functions such that they are invoked one after the other until one
of the providers returns a promise that is fulfilled successfully.

The ``defaultProvider`` uses this composition in order to check multiple
providers before failing. The source of the ``defaultProvider`` demonstrates
the use of the ``chain`` function.

.. code-block:: php

    // This function returns a provider.
    public static function defaultProvider(array $config = [])
    {
        // This function is the provider, which is actually the composition
        // of multiple providers. Notice that we are memoizing the result by
        // default as well.
        return self::memoize(
            self::chain(
                self::env(),
                self::ini(),
                self::instanceProfile($config)
            )
        );
    }


.. _temporary_credentials:

Using temporary credentials from AWS STS
----------------------------------------

`AWS Security Token Service <http://docs.aws.amazon.com/STS/latest/APIReference/Welcome.html>`_
(AWS STS) enables you to request limited-privilege, **temporary credentials**
for AWS IAM users or for users that you authenticate via identity federation.
One common use case for using temporary credentials is to grant mobile or
client-side applications access to AWS resources by authenticating users
through third-party identity providers (read more about `Web Identity Federation
<http://docs.aws.amazon.com/STS/latest/UsingSTS/CreatingWIF.html>`_).

.. note::

    Temporary credentials generated by AWS STS are not supported by every
    service. Please check if the service you are using supports temporary
    credentials by reading `AWS Services that Support AWS STS <http://docs.aws.amazon.com/STS/latest/UsingSTS/UsingTokens.html>`_.


Getting temporary credentials
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

AWS STS has several operations that return temporary credentials, but the
``GetSessionToken`` operation is the simplest for demonstration purposes.
Assuming you have an instance of ``Aws\Sts\StsClient`` stored in the
``$stsClient`` variable, this is how you call it:

.. code-block:: php

    $result = $stsClient->getSessionToken();

The result for ``GetSessionToken`` and the other AWS STS operations always
contains a ``'Credentials'`` value. If you print the result
(e.g., ``print_r($result)``), it looks like the following:

::

    Array
    (
        ...
        [Credentials] => Array
        (
            [SessionToken] => '<base64 encoded session token value>'
            [SecretAccessKey] => '<temporary secret access key value>'
            [Expiration] => 2013-11-01T01:57:52Z
            [AccessKeyId] => '<temporary access key value>'
        )
        ...
    )


Providing temporary credentials to the SDK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can use temporary credentials with another AWS client by instantiating
the client and passing in the values received from AWS STS directly.

.. code-block:: php

    use Aws\S3\S3Client;

    $result = $stsClient->getSessionToken();

    $s3Client = new S3Client([
        'version'     => '2006-03-01',
        'region'      => 'us-west-2',
        'credentials' => [
            'key'    => $result['Credentials']['AccessKeyId'],
            'secret' => $result['Credentials']['SecretAccessKey'],
            'token'  => $result['Credentials']['SessionToken']
        ]
    ]);

You can also construct a ``Aws\Credentials\Credentials`` object and use that
when instantiating the client.

.. code-block:: php

    use Aws\Credentials\Credentials;
    use Aws\S3\S3Client;

    $result = $stsClient->getSessionToken();

    $credentials = new Credentials(
        $result['Credentials']['AccessKeyId'],
        $result['Credentials']['SecretAccessKey'],
        $result['Credentials']['SessionToken']
    );

    $s3Client = new S3Client([
        'version'     => '2006-03-01',
        'region'      => 'us-west-2',
        'credentials' => $credentials
    ]);

However, the *best* way to provide temporary credentials is to use the
``createCredentials()`` helper method included with the ``StsClient``. This
method extracts the data from an AWS STS result and creates the ``Credentials``
object for you.

.. code-block:: php

    $result = $stsClient->getSessionToken();
    $credentials = $stsClient->createCredentials($result);

    $s3Client = new S3Client([
        'version'     => '2006-03-01',
        'region'      => 'us-west-2',
        'credentials' => $credentials
    ]);

For more information about why you might need to use temporary credentials in
your application or project, see `Scenarios for Granting Temporary Access
<http://docs.aws.amazon.com/STS/latest/UsingSTS/STSUseCases.html>`_ in the AWS
STS documentation.


.. _anonymous_access:

Creating Anonymous Clients
--------------------------

In some cases, you may want to create a client that is not associated with any
credentials. This allows you to make anonymous requests to a service. For
example, both S3 Objects and CloudSearch Domains can be configured to allow
anonymous access.

To create an anonymous client, you can set the ``'credentials'`` option to
``false``.

.. code-block:: php

    $s3Client = new S3Client([
        'version'     => 'latest',
        'region'      => 'us-west-2',
        'credentials' => false
    ]);

    // Makes an anonymous request. The Object would need to be publicly
    // readable for this to succeed.
    $result = $s3Client->getObject([
        'Bucket' => 'my-bucket',
        'Key'    => 'my-key',
    ]);
