使用AWS Transfer for SFTP仅允许写入存储桶的访问，您可以按照以下步骤进行设置：

1. 创建一个S3存储桶：

   import boto3
   
   s3_client = boto3.client('s3')
   bucket_name = 'your-bucket-name'
   
   s3_client.create_bucket(Bucket=bucket_name)
   

2. 创建一个IAM角色，用于访问S3存储桶：

   import boto3
   
   iam_client = boto3.client('iam')
   role_name = 'sftp-to-s3-role'
   
   iam_client.create_role(
       RoleName=role_name,
       AssumeRolePolicyDocument='''{
           "Version": "2012-10-17",
           "Statement": [
               {
                   "Effect": "Allow",
                   "Principal": {
                       "Service": "transfer.amazonaws.com"
                   },
                   "Action": "sts:AssumeRole"
               }
           ]
       }'''
   )
   
   iam_client.attach_role_policy(
       RoleName=role_name,
       PolicyArn='arn:aws:iam::aws:policy/AmazonS3FullAccess'
   )
   

3. 创建AWS Transfer for SFTP服务器：

   import boto3
   
   transfer_client = boto3.client('transfer')
   
   s3_arn = 'arn:aws:s3:::your-bucket-name'
   role_arn = 'arn:aws:iam::your-account-id:role/sftp-to-s3-role'
   
   response = transfer_client.create_server(
       EndpointType='VPC',
       EndpointDetails={
           'VpcEndpointId': 'your-vpc-endpoint-id'
       },
       IdentityProviderType='SERVICE_MANAGED',
       IdentityProviderDetails={},
       LoggingRole=role_arn,
       Protocols=['SFTP'],
       Tags=[
           {
               'Key': 'Name',
               'Value': 'SFTP Server'
           }
       ]
   )
   

4. 创建AWS Transfer for SFTP用户：

   import boto3
   
   transfer_client = boto3.client('transfer')
   
   server_id = 'your-sftp-server-id'
   username = 'sftp-user'
   
   response = transfer_client.create_user(
       ServerId=server_id,
       UserName=username,
       HomeDirectory='/',
       Role='arn:aws:iam::your-account-id:role/sftp-to-s3-role'
   )
   

5. 配置AWS Transfer for SFTP服务器的存储桶访问：

   import boto3
   
   transfer_client = boto3.client('transfer')
   
   server_id = 'your-sftp-server-id'
   bucket_arn = 'arn:aws:s3:::your-bucket-name'
   
   response = transfer_client.update_server(
       ServerId=server_id,
       IdentityProviderType='SERVICE_MANAGED',
       IdentityProviderDetails={},
       EndpointDetails={
           'VpcEndpointId': 'your-vpc-endpoint-id',
           'VpcId': 'your-vpc-id',
           'SecurityGroupIds': ['your-security-group-id']
       },
       LoggingRole='arn:aws:iam::your-account-id:role/sftp-to-s3-role',
       Protocols=['SFTP'],
       DefaultPermissions=[
           {
               'HomeDirectory': '/',
               'Perm': 'WRITE',
               'Type': 'EXTENDED_SCOPE',
               'Values': [bucket_arn]
           }
       ]
   )
   

通过以上步骤，您可以创建一个AWS Transfer for SFTP服务器，配置只允许写入指定存储桶的访问权限。请根据您的实际情况修改代码中的参数值。