如何从Lambda函数访问S3存储桶中的文件

Question

I have a file a my S3 bucket and I want to access this file from a Lambda function.

When I pass the path of this file to one of the methods, I get the error:

Could not find a part of the path '/var/task/https:/s3.amazonaws.com/TestBucket/testuser/AWS_sFTP_Key.pem".

For example:

TestMethod("https://s3.amazonaws.com/TestBucket/testuser/AWS_sFTP_Key.pem")

code:

public void FunctionHandler(S3Event s3Event, ILambdaContext lambdaContext)
        {
            ConnectionInfo connectionInfo = new ConnectionInfo("xxx.xxx.xx.xxx", "testuser",
                                                   new AuthenticationMethod[]{
            new PrivateKeyAuthenticationMethod("testuser", new PrivateKeyFile[] {
                new PrivateKeyFile("https://s3.amazonaws.com/TestBucket/testuser/AWS_sFTP_Key.pem")})
});

            SftpClient sftpClient = new SftpClient(connectionInfo);
            sftpClient.Connect();
            lambdaContext.Logger.Log(sftpClient.WorkingDirectory);
            sftpClient.Disconnect();
        }

Answer 1

You can use AWS SDK for reading the file from S3 as shown below, however I would suggest to use AWS Certificate Manager or IAM for storing and managing your certificates and keys:

PS: Make sure you assign the proper role for your lambda function or bucket policy for your bucket to be able to GetObject from S3 :

    RegionEndpoint bucketRegion = RegionEndpoint.USWest2;//region where you store your file

    client = new AmazonS3Client(bucketRegion);

    GetObjectRequest request = new GetObjectRequest();

    request.WithBucketName(BUCKET_NAME);//TestBucket
    request.WithKey(S3_KEY);//testuser/AWS_sFTP_Key.pem

    GetObjectResponse response = client.GetObject(request);

    StreamReader reader = new StreamReader(response.ResponseStream);

    String content = reader.ReadToEnd();

More Help:

• https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_server-certs.html
• https://docs.aws.amazon.com/acm/latest/userguide/import-certificate.html
• https://docs.aws.amazon.com/AmazonS3/latest/dev/RetrievingObjectUsingNetSDK.html