Chapter 2. Object Gateway S3 Application Programming Interface (API)

1. Get the value of the header string.
2. Normalize the request header string into canonical form.
3. Generate an HMAC using a SHA-1 hashing algorithm.
4. Encode the hmac result as base-64.

1. Get all content- headers.
2. Remove all content- headers except for content-type and content-md5.
3. Ensure the content- header names are lowercase.
4. Sort the content- headers lexicographically.
5. Ensure you have a Date header AND ensure the specified date uses GMT and not an offset.
6. Get all headers beginning with x-amz-.
7. Ensure that the x-amz- headers are all lowercase.
8. Sort the x-amz- headers lexicographically.
9. Combine multiple instances of the same field name into a single field and separate the field values with a comma.
10. Replace white space and line breaks in header values with a single space.
11. Remove white space before and after colons.
12. Append a new line after each header.
13. Merge the headers back into the request header.

1. Set up the gateway server properly by following the instructions based on the operating system:

   1. For Red Hat Enterprise Linux, see the Ceph Object Gateway Installation chapter in the Installation Guide for Red hat Enterprise Linux.
   2. For Ubuntu, see the Ceph Object Gateway Installation chapter in the Installation Guide for Ubuntu.
2. DO NOT modify the Ceph configuration file to use port 80 and let Civetweb use the default Ansible configured port of 8080.

3. As root, open port 8080 on firewall:

   # firewall-cmd --zone=public --add-port=8080/tcp --permanent
   # firewall-cmd --reload

4. Add a wildcard to the DNS server that you are using for the gateway as mentioned in the Object Gateway Guide.

   You can also set up the gateway node for local DNS caching. To do so, execute the following steps:

   1. As root, install and setup dnsmasq:

      # yum install dnsmasq
      # echo "address=/.<FQDN_of_gateway_node>/<IP_of_gateway_node>" | tee --append /etc/dnsmasq.conf
      # systemctl start dnsmasq
      # systemctl enable dnsmasq

      Replace <IP_of_gateway_node> and <FQDN_of_gateway_node> with the IP address and FQDN of the gateway node.

   2. As root, stop NetworkManager:

      # systemctl stop NetworkManager
      # systemctl disable NetworkManager

   3. As root, set the gateway server’s IP as the nameserver:

      # echo "DNS1=<IP_of_gateway_node>" | tee --append /etc/sysconfig/network-scripts/ifcfg-eth0
      # echo "<IP_of_gateway_node> <FQDN_of_gateway_node>" | tee --append /etc/hosts
      # systemctl restart network
      # systemctl enable network
      # systemctl restart dnsmasq

      Replace <IP_of_gateway_node> and <FQDN_of_gateway_node> with the IP address and FQDN of the gateway node.

   4. Verify subdomain requests:

      $ ping mybucket.<FQDN_of_gateway_node>

      Replace <FQDN_of_gateway_node> with the FQDN of the gateway node.

      Warning

      Setting up the gateway server for local DNS caching is for testing purposes only. You won’t be able to access outside network after doing this. It is strongly recommended to use a proper DNS server for the Ceph cluster and gateway node.

5. Create the radosgw user for S3 access carefully as mentioned in the Object Gateway Guide for Red Hat Enterprise Linux or Object Gateway Guide for Ubuntu and copy the generated access_key and secret_key. You will need these keys for S3 access and subsequent bucket management tasks.

1. As root, install ruby:

   # yum install ruby

   Note

   The above command will install ruby and it’s essential dependencies like rubygems and ruby-libs too. If somehow the command doesn’t install all the dependencies, install them separately.

2. As root, install aws-s3:

   # gem install aws-s3

Creating a connection

1. Create a project directory:

   $ mkdir ruby_aws_s3
   $ cd ruby_aws_s3

2. Create the connection file:

   $ vim conn.rb

3. Paste the following contents into the conn.rb file:

   #!/usr/bin/env ruby
   
   require 'aws/s3'
   require 'resolv-replace'
   
   AWS::S3::Base.establish_connection!(
           :server            => '<FQDN_of_gateway_node>',
           :port           => '8080',
           :access_key_id     => 'my-access-key',
           :secret_access_key => 'my-secret-key'
   )

   Replace <FQDN_of_gateway_node> with the FQDN of your gateway node. Replace my-access-key and my-secret-key with the access_key and secret_key that were generated when you created the radosgw user for S3 access as mentioned in the Object Gateway Guide for Red Hat Enterprise Linux or the Object Gateway Guide for Ubuntu.

   An example connection file looks like the following:

   #!/usr/bin/env ruby
   
   require 'aws/s3'
   
   require 'resolv-replace'
   
   AWS::S3::Base.establish_connection!(
           :server            => 'testclient.englab.pnq.redhat.com',
           :port           => '8080',
           :access_key_id     => '98J4R9P22P5CDL65HKP8',
           :secret_access_key => '6C+jcaP0dp0+FZfrRNgyGA9EzRy25pURldwje049'
   )

   Save the file and exit the editor.

4. Make the file executable:

   $ chmod +x conn.rb

5. Run the file:

   $ ./conn.rb | echo $?

   If you have provided the values correctly in the file, the output of the command will be 0.

Creating a bucket

1. Create a new file:

   $ vim create_bucket.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   AWS::S3::Bucket.create('my-new-bucket1')

   Save the file and exit the editor.

2. Make the file executable:

   $ chmod +x create_bucket.rb

3. Run the file:

   $ ./create_bucket.rb

   If the output of the command is true it would mean that bucket my-new-bucket1 was created successfully.

Listing owned buckets

1. Create a new file:

   $ vim list_owned_buckets.rb

   Paste the following content into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   AWS::S3::Service.buckets.each do |bucket|
           puts "#{bucket.name}\t#{bucket.creation_date}"
   end

   Save the file and exit the editor.

2. Make the file executable:

   $ chmod +x list_owned_buckets.rb

3. Run the file:

   $ ./list_owned_buckets.rb

   The output should look something like this:

   my-new-bucket1 2016-01-21 10:33:19 UTC

Creating an object

1. Create a new file:

   $ vim create_object.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   AWS::S3::S3Object.store(
           'hello.txt',
           'Hello World!',
           'my-new-bucket1',
           :content_type => 'text/plain'
   )

   Save the file and exit the editor.

2. Make the file executable:

   $ chmod +x create_object.rb

3. Run the file:

   $ ./create_object.rb

   This will create a file hello.txt with the string Hello World!.

Listing a Bucket’s Content

1. Create a new file:

   $ vim list_bucket_content.rb

   Paste the following content into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   new_bucket = AWS::S3::Bucket.find('my-new-bucket1')
   new_bucket.each do |object|
           puts "#{object.key}\t#{object.about['content-length']}\t#{object.about['last-modified']}"
   end

   Save the file and exit the editor.

2. Make the file executable.

   $ chmod +x list_bucket_content.rb

3. Run the file:

   $ ./list_bucket_content.rb

   The output will look something like this:

   hello.txt    12    Fri, 22 Jan 2016 15:54:52 GMT

Deleting a empty bucket

1. Create a new file:

   $ vim del_empty_bucket.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   AWS::S3::Bucket.delete('my-new-bucket1')

   Save the file and exit the editor.

2. Make the file executable:

   $ chmod +x del_empty_bucket.rb

3. Run the file:

   $ ./del_empty_bucket.rb | echo $?

   If the bucket is successfully deleted, the command will return 0 as output.

   Note

   Please edit the create_bucket.rb file to create empty buckets like my-new-bucket9, my-new-bucket10 etc and edit the above mentioned del_empty_bucket.rb file accordingly before trying to delete empty buckets.

Deleting a non-empty bucket (forcefully)

1. Create a new file:

   $ vim del_non_empty_bucket.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   AWS::S3::Bucket.delete('my-new-bucket1', :force => true)

   Save the file and exit the editor.

2. Make the file executable:

   $ chmod +x del_non_empty_bucket.rb

3. Run the file:

   $ ./del_non_empty_bucket.rb | echo $?

   If the bucket is successfully deleted, the command will return 0 as output.

Deleting an object

1. Create a new file:

   $ vim delete_object.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   AWS::S3::S3Object.delete('hello.txt', 'my-new-bucket1')

   Save the file and exit the editor.

2. Make the file executable:

   $ chmod +x delete_object.rb

3. Run the file:

   $ ./delete_object.rb

   This will delete the object hello.txt.

1. As root, install ruby:

   # yum install ruby

   Note

   The above command will install ruby and its essential dependencies such as rubygems and ruby-libs. If somehow the command doesn’t install all the dependencies, install them separately.

2. As root, install aws-sdk:

   # gem install aws-sdk

Creating a connection

1. Create a project directory:

   $ mkdir ruby_aws_sdk
   $ cd ruby_aws_sdk

2. Create the connection file:

   $ vim conn.rb

3. Paste the following contents into the conn.rb file:

   #!/usr/bin/env ruby
   
   require 'aws-sdk'
   require 'resolv-replace'
   
   Aws.config.update(
           endpoint: 'http://<FQDN_of_gateway_node>:8080',
           access_key_id: 'my-access-key',
           secret_access_key: 'my-secret-key',
           force_path_style: true,
           region: 'us-east-1'
   )

   Replace <FQDN_of_gateway_node> with the FQDN of your gateway node. Replace my-access-key and my-secret-key with the access_key and secret_key that were generated when you created the radosgw user for S3 access as mentioned in the Red Hat Ceph Storage Object Gateway Guide.

   An example connection file looks like the following:

   #!/usr/bin/env ruby
   
   require 'aws-sdk'
   require 'resolv-replace'
   
   Aws.config.update(
           endpoint: 'http://testclient.englab.pnq.redhat.com:8080',
           access_key_id: '98J4R9P22P5CDL65HKP8',
           secret_access_key: '6C+jcaP0dp0+FZfrRNgyGA9EzRy25pURldwje049',
           force_path_style: true,
           region: 'us-east-1'
   )

   Save the file and exit the editor.

4. Make the file executable:

   chmod +x conn.rb

5. Run the file:

   ./conn.rb | echo $?

   If you have provided the values correctly in the file, the output of the command will be 0.

Creating a bucket

1. Create a new file:

   vim create_bucket.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   s3_client.create_bucket(bucket: 'my-new-bucket2')

   Save the file and exit the editor.

2. Make the file executable:

   chmod +x create_bucket.rb

3. Run the file:

   ./create_bucket.rb

   If the output of the command is true it would mean that bucket my-new-bucket2 was created successfully.

Listing owned buckets

1. Create a new file:

   vim list_owned_buckets.rb

   Paste the following content into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   s3_client.list_buckets.buckets.each do |bucket|
           puts "#{bucket.name}\t#{bucket.creation_date}"
   end

   Save the file and exit the editor.

2. Make the file executable:

   chmod +x list_owned_buckets.rb

3. Run the file:

   ./list_owned_buckets.rb

   The output should look something like this:

   my-new-bucket2 2016-01-21 10:33:19 UTC

Creating an object

1. Create a new file:

   vim create_object.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   s3_client.put_object(
           key: 'hello.txt',
           body: 'Hello World!',
           bucket: 'my-new-bucket2',
           content_type: 'text/plain'
   )

   Save the file and exit the editor.

2. Make the file executable:

   chmod +x create_object.rb

3. Run the file:

   ./create_object.rb

   This will create a file hello.txt with the string Hello World!.

Listing a Bucket’s Content

1. Create a new file:

   vim list_bucket_content.rb

   Paste the following content into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   s3_client.list_objects(bucket: 'my-new-bucket2').contents.each do |object|
           puts "#{object.key}\t#{object.size}"
   end

   Save the file and exit the editor.

2. Make the file executable.

   chmod +x list_bucket_content.rb

3. Run the file:

   ./list_bucket_content.rb

   The output will look something like this:

   hello.txt    12    Fri, 22 Jan 2016 15:54:52 GMT

Deleting a empty bucket

1. Create a new file:

   vim del_empty_bucket.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   s3_client.delete_bucket(bucket: 'my-new-bucket2')

   Save the file and exit the editor.

2. Make the file executable:

   chmod +x del_empty_bucket.rb

3. Run the file:

   ./del_empty_bucket.rb | echo $?

   If the bucket is successfully deleted, the command will return 0 as output.

   Note

   Please edit the create_bucket.rb file to create empty buckets like my-new-bucket6, my-new-bucket7 etc and edit the above mentioned del_empty_bucket.rb file accordingly before trying to delete empty buckets.

Deleting a non-empty bucket (forcefully)

1. Create a new file:

   vim del_non_empty_bucket.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   Aws::S3::Bucket.new('my-new-bucket2', client: s3_client).clear!
   s3_client.delete_bucket(bucket: 'my-new-bucket2')

   Save the file and exit the editor.

2. Make the file executable:

   chmod +x del_non_empty_bucket.rb

3. Run the file:

   ./del_non_empty_bucket.rb | echo $?

   If the bucket is successfully deleted, the command will return 0 as output.

Deleting an object

1. Create a new file:

   vim delete_object.rb

   Paste the following contents into the file:

   #!/usr/bin/env ruby
   
   load 'conn.rb'
   
   s3_client = Aws::S3::Client.new
   s3_client.delete_object(key: 'hello.txt', bucket: 'my-new-bucket2')

   Save the file and exit the editor.

2. Make the file executable:

   chmod +x delete_object.rb

3. Run the file:

   ./delete_object.rb

   This will delete the object hello.txt.

1. As root, install php:

   # yum install php

2. Install aws-sdk for php:

   Download the zip archive of aws-sdk for php and extract it.

Creating a connection

1. Create a project directory:

   $ mkdir php_s3
   $ cd php_s3

2. Copy the extracted aws directory to the project directory. For example:

   $ cp -r ~/Downloads/aws/ ~/php_s3/

3. Create the connection file:

   $ vim conn.php

4. Paste the following contents in the conn.php file:

   <?php
   define('AWS_KEY', 'my_access_key');
   define('AWS_SECRET_KEY', 'my_secret_key');
   define('HOST', '<FQDN_of_gateway_node>');
   define('PORT', '8080');
   
   // require the AWS SDK for php library
   require '/path_to_aws/aws-autoloader.php';
   
   use Aws\S3\S3Client;
   
   // Establish connection with host using S3 Client
   $client = S3Client::factory(array(
       'base_url' => HOST,
       'port' => PORT,
       'key'      => AWS_KEY,
       'secret'   => AWS_SECRET_KEY
   ));
   ?>

   Replace <FQDN_of_gateway_node> with the FQDN of the gateway node. Replace my-access-key and my-secret-key with the access_key and secret_key that were generated when you created the radosgw user for S3 access as mentioned in the Red Hat Ceph Storage Object Gateway Guide. Also, replace path_to_aws with absolute path to the extracted aws directory that you copied to the php project directory.

   An example connection file will look like the following:

   <?php
   define('AWS_KEY', '{key}');
   define('AWS_SECRET_KEY', '{secret}');
   define('HOST', 'http://{hostname}');
   
   // require the AWS SDK for php library
   require '/home/ceph/php_s3/aws/aws-autoloader.php';
   
   use Aws\S3\S3Client;
   
   // Establish connection with host using S3 Client
   $client = S3Client::factory(array(
       'base_url' => HOST,
       'port' => PORT,
       'key'      => AWS_KEY,
       'secret'   => AWS_SECRET_KEY
   ));
   ?>

   Save the file and exit the editor.

5. Run the file:

   $ php -f conn.php | echo $?

   If you have provided the values correctly in the file, the output of the command will be 0.

Creating a bucket

1. Create a new file:

   vim create_bucket.php

   Paste the following contents into the file:

   <?php
   
   include 'conn.php';
   
   $client->createBucket(array('Bucket' => 'my-new-bucket3'));
   
   ?>

   Save the file and exit the editor.

2. Run the file:

   php -f create_bucket.php

Listing owned buckets

1. Create a new file:

   vim list_owned_buckets.php

   Paste the following content into the file:

   <?php
   
   include 'conn.php';
   
   $blist = $client->listBuckets();
   echo "   Buckets belonging to " . $blist['Owner']['ID'] . ":\n";
   foreach ($blist['Buckets'] as $b) {
       echo "{$b['Name']}\t{$b['CreationDate']}\n";
   }
   
   ?>

   Save the file and exit the editor.

2. Run the file:

   php -f list_owned_buckets.php

   The output should look something like this:

   my-new-bucket3 2016-01-21 10:33:19 UTC

Creating an object

1. Create a source file hello.txt:

   echo "Hello World!" > hello.txt

2. Create a new php file:

   vim create_object.php

   Paste the following contents into the file:

   <?php
   
   include 'conn.php';
   
   $key         = 'hello.txt';
   $source_file = './hello.txt';
   $acl         = 'private';
   $bucket      = 'my-new-bucket3';
   $client->upload($bucket, $key, fopen($source_file, 'r'), $acl);
   
   ?>

   Save the file and exit the editor.

3. Run the file:

   php -f create_object.php

   This will create the object hello.txt in bucket my-new-bucket3.

Listing a Bucket’s Content

1. Create a new file:

   vim list_bucket_content.php

   Paste the following content into the file:

   <?php
   
   include 'conn.php';
   
   $o_iter = $client->getIterator('ListObjects', array(
       'Bucket' => 'my-new-bucket3'
   ));
   foreach ($o_iter as $o) {
       echo "{$o['Key']}\t{$o['Size']}\t{$o['LastModified']}\n";
   }
   ?>

   Save the file and exit the editor.

2. Run the file:

   php -f list_bucket_content.php

   The output will look something like this:

   hello.txt    12    Fri, 22 Jan 2016 15:54:52 GMT

Deleting an empty bucket

1. Create a new file:

   vim del_empty_bucket.php

   Paste the following contents into the file:

   <?php
   
   include 'conn.php';
   
   $client->deleteBucket(array('Bucket' => 'my-new-bucket3'));
   ?>

   Save the file and exit the editor.

2. Run the file:

   php -f del_empty_bucket.php | echo $?

   If the bucket is successfully deleted, the command will return 0 as output.

   Note

   Edit the create_bucket.php file to create empty buckets like my-new-bucket4, my-new-bucket5, and so on, and then edit the del_empty_bucket.php file accordingly before trying to delete empty buckets.

Deleting an object

1. Create a new file:

   vim delete_object.php

   Paste the following contents into the file:

   <?php
   
   include 'conn.php';
   
   $client->deleteObject(array(
       'Bucket' => 'my-new-bucket3',
       'Key'    => 'hello.txt',
   ));
   ?>

   Save the file and exit the editor.

2. Run the file:

   php -f delete_object.php

   This will delete the object hello.txt.

Procedure

1. Open and edit the group_vars/rgws.yml file with the following options:

   rgw_sts_key = $STS_KEY_FOR_ENCRYPTING_SESSION_TOKEN
   rgw_s3_auth_use_sts = true

2. Rerun the Ansible playbook:

   [user@admin ceph-ansible]$ ansible-playbook site.yml --limit rgws

3. Generate the EC2 credentials:

   Example

   $ openstack ec2 credentials create
   +------------+--------------------------------------------------------+
   | Field      | Value                                                  |
   +------------+--------------------------------------------------------+
   | access     | b924dfc87d454d15896691182fdeb0ef                       |
   | links      | {u'self': u'http://192.168.0.15/identity/v3/users/     |
   |            | 40a7140e424f493d8165abc652dc731c/credentials/          |
   |            | OS-EC2/b924dfc87d454d15896691182fdeb0ef'}              |
   | project_id | c703801dccaf4a0aaa39bec8c481e25a                       |
   | secret     | 6a2142613c504c42a94ba2b82147dc28                       |
   | trust_id   | None                                                   |
   | user_id    | 40a7140e424f493d8165abc652dc731c                       |
   +------------+--------------------------------------------------------+

4. Use the generated credentials to get back a set of temporary security credentials using GetSessionToken API.

   Example

   import boto3
   
   access_key = b924dfc87d454d15896691182fdeb0ef
   secret_key = 6a2142613c504c42a94ba2b82147dc28
   
   client = boto3.client('sts',
   aws_access_key_id=access_key,
   aws_secret_access_key=secret_key,
   endpoint_url=https://www.example.com/rgw,
   region_name='',
   )
   
   response = client.get_session_token(
       DurationSeconds=43200
   )

5. Obtaining the temporary credentials can be used for making S3 calls:

   Example

       s3client = boto3.client('s3',
         aws_access_key_id = response['Credentials']['AccessKeyId'],
         aws_secret_access_key = response['Credentials']['SecretAccessKey'],
         aws_session_token = response['Credentials']['SessionToken'],
         endpoint_url=https://www.example.com/s3,
         region_name='')
   
       bucket = s3client.create_bucket(Bucket='my-new-shiny-bucket')
       response = s3client.list_buckets()
       for bucket in response["Buckets"]:
           print "{name}\t{created}".format(
                       name = bucket['Name'],
                       created = bucket['CreationDate'],
       )

6. Create a new S3Access role and configure a policy.

   1. Assign a user with administrative CAPS:

      radosgw-admin caps add --uid="$USER" --caps="roles=*"

      Example

      [user@client]$ radosgw-admin caps add --uid="gwadmin" --caps="roles=*"

   2. Create the S3Access role:

      radosgw-admin role create --role-name=$ROLE_NAME --path=$PATH --assume-role-policy-doc=$TRUST_POLICY_DOC

      Example

      [user@client]$ radosgw-admin role create --role-name=S3Access --path=/application_abc/component_xyz/ --assume-role-policy-doc=\{\"Version\":\"2012-10-17\",\"Statement\":\[\{\"Effect\":\"Allow\",\"Principal\":\{\"AWS\":\[\"arn:aws:iam:::user/TESTER\"\]\},\"Action\":\[\"sts:AssumeRole\"\]\}\]\}

   3. Attach a permission policy to the S3Access role:

      radosgw-admin role-policy put --role-name=$ROLE_NAME --policy-name=$POLICY_NAME --policy-doc=$PERMISSION_POLICY_DOC

      Example

      [user@client]$ radosgw-admin role-policy put --role-name=S3Access --policy-name=Policy --policy-doc=\{\"Version\":\"2012-10-17\",\"Statement\":\[\{\"Effect\":\"Allow\",\"Action\":\[\"s3:*\"\],\"Resource\":\"arn:aws:s3:::example_bucket\"\}\]\}

   4. Now another user can assume the role of the gwadmin user. For example, the gwuser user can assume the permissions of the gwadmin user.

   5. Make a note of the assuming user’s access_key and secret_key values.

      Example

      [user@client]$ radosgw-admin user info --uid=gwuser | grep -A1 access_key

7. Use the AssumeRole API call, providing the access_key and secret_key values from the assuming user:

   Example

   import boto3
   
   access_key = 11BS02LGFB6AL6H1ADMW
   secret_key = vzCEkuryfn060dfee4fgQPqFrncKEIkh3ZcdOANY
   
   client = boto3.client('sts',
   aws_access_key_id=access_key,
   aws_secret_access_key=secret_key,
   endpoint_url=https://www.example.com/rgw,
   region_name='',
   )
   
   response = client.assume_role(
   RoleArn='arn:aws:iam:::role/application_abc/component_xyz/S3Access',
   RoleSessionName='Bob',
   DurationSeconds=3600
   )

   Important

   The AssumeRole API requires the S3Access role.

Procedure

1. Open and edit Boto’s auth.py file.

   1. Add the following four lines to the code block:

      class SigV4Auth(BaseSigner):
        """
        Sign a request with Signature V4.
        """
        REQUIRES_REGION = True
      
        def __init__(self, credentials, service_name, region_name):
            self.credentials = credentials
            # We initialize these value here so the unit tests can have
            # valid values.  But these will get overriden in ``add_auth``
            # later for real requests.
            self._region_name = region_name
            if service_name == 'sts': 1
                self._service_name = 's3' 2
            else: 3
                self._service_name = service_name 4

   2. Add the following two lines to the code block:

      def _modify_request_before_signing(self, request):
              if 'Authorization' in request.headers:
                  del request.headers['Authorization']
              self._set_necessary_date_headers(request)
              if self.credentials.token:
                  if 'X-Amz-Security-Token' in request.headers:
                      del request.headers['X-Amz-Security-Token']
                  request.headers['X-Amz-Security-Token'] = self.credentials.token
      
              if not request.context.get('payload_signing_enabled', True):
                  if 'X-Amz-Content-SHA256' in request.headers:
                      del request.headers['X-Amz-Content-SHA256']
                  request.headers['X-Amz-Content-SHA256'] = UNSIGNED_PAYLOAD 1
              else: 2
                  request.headers['X-Amz-Content-SHA256'] = self.payload(request)