Access aws services without key & secret in php - php

Question

To be clear, We have created the EC2 policy, so my site can directly access the services like Parameter store, S3, Amazon SES etc.
As of now, all of my credentials are stored on AWS Parameter Store and then site is using those credentials i.e. DB credentials, diff. API keys etc. So only hard coded credentials are the one which fetch the parameters from Parameter Store. Now client want to remove those hard coded credentials as well, that's why we have created the EC2 Policy.
Till now, we have code like below to fetch the parameters:
$config = array(
'version' => 'latest',
'region' => '*****',
'credentials' => array(
'key' => '*******',
'secret' => '******',
)
);
$s3_instance = new \Aws\Ssm\SsmClient($config);
$result = $s3_instance->getParameters([
'Names' => $credential_group,
'WithDecryption' => true
]);
//converting S3 private data to array to read
$keys = $result->toArray();
var_dump($keys);
Now the question is what i have to change in above code, so it should work without passing those credentials.
Note: I am using AWS PHP library to perform above.
Update
Further reading the documentation, https://docs.aws.amazon.com/sdk-for-php/v3/developer-guide/guide_credentials.html
Using Credentials from Environment Variables
If you don't provide credentials to a client object at the time of its instantiation, the SDK attempts to find credentials in your environment. The first place the SDK checks for credentials is in your environment variables. The SDK uses 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.
So after that, i have tried the below:
var_dump(getenv('AWS_ACCESS_KEY_ID'));
But it returns the bool(false). So does i need to manually setup those in environment credentials?
Which things i need to change in above code?
Update
Based on this doc: https://docs.aws.amazon.com/sdk-for-php/v3/developer-guide/guide_configuration.html#credentials
I had made below change (Removed the credentials part from array):
$config = array(
'version' => 'latest',
'region' => '*****'
);
Then system throws the below warnings:
Warning: include(Test_Role_Cognitoaccess_from_instanceRole.php): failed to open stream
Warning: include(): Failed opening 'Test_Role_Cognitoaccess_from_instanceRole.php' for inclusion (include_path='.:/usr/share/pear:/usr/share/php')
Warning: include(Test_Role_Cognitoaccess_from_instanceRole.php): failed to open stream
Warning: include(): Failed opening 'Test_Role_Cognitoaccess_from_instanceRole.php' for inclusion (include_path='.:/usr/share/pear:/usr/share/php')

Answer 1

As you already mentioned that you attached the policy to EC2 IAM role to access other AWS services.
You should try to create a default credential provider, this will automatically pick keys from the role.
$provider = CredentialProvider::chain(CredentialProvider::env(), CredentialProvider::ini(), CredentialProvider::instanceProfile(), CredentialProvider::ecsCredentials());

Answer 2

When you pass credentials directly to SsmClient and same time you have defined a role to the EC2 machine then you are making confusion for the AWS. If you have defined the permission for the EC2 instance then just do as follow:
use Aws\Ssm\SsmClient;
$client = new SsmClient(['version' => 'latest', 'region' => 'ap-southeast-2']);
$result = $client->getParameters(['Names' => ['My-SECRATE-KEY'], 'WithDecryption' => true]);
print_r($result);
Please keep in mind that permissions take a little time to propagate and in this period you will get permission error for the specific user. If you wait and let the changes take effect then mentioned code will work without any error. In my case I attached AmazonSSMReadOnlyAccess to the EC2 role and to EC2 instance. If you key/value in Parameter store is not encrypted then you can remove 'WithDecryption' => true or change it to false.