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Examples: Signature Calculations in AWS Signature Version 4

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For authenticated requests, unless you are using the AWS SDKs, you have to write code to calculate signatures that provide authentication information in your requests. Signature calculation in AWS Signature Version 4 (see Authenticating Requests (AWS Signature Version 4)) can be a complex undertaking, and we recommend that you use the AWS SDKs whenever possible.

This section provides examples of signature calculations written in Java and C#. The code samples send the following requests and use the HTTP Authorization header to provide authentication information:

• PUT object – Separate examples illustrate both uploading the full payload at once and uploading the payload in chunks. For information about using the Authorization header for authentication, see Authenticating Requests: Using the Authorization Header (AWS Signature Version 4).

• GET object – This example generates a presigned URL to get an object. Query parameters provide the signature and other authentication information. Users can paste a presigned URL in their browser to retrieve the object, or you can use the URL to create a clickable link. For information about using query parameters for authentication, see Authenticating Requests: Using Query Parameters (AWS Signature Version 4).

The rest of this section describes the examples in Java and C#. The topics include instructions for downloading the samples and for executing them.

Signature Calculation Examples Using Java (AWS Signature Version 4)

The Java sample that shows signature calculation can be downloaded at https://docs.aws.amazon.com/AmazonS3/latest/API/samples/AWSS3SigV4JavaSamples.zip. In RunAllSamples.java, the main() function executes sample requests to create an object, retrieve an object, and create a presigned URL for the object. The sample creates an object from the text string provided in the code:

PutS3ObjectSample.putS3Object(bucketName, regionName, awsAccessKey, awsSecretKey); 
GetS3ObjectSample.getS3Object(bucketName, regionName, awsAccessKey, awsSecretKey); 
PresignedUrlSample.getPresignedUrlToS3Object(bucketName, regionName, awsAccessKey, awsSecretKey); 
PutS3ObjectChunkedSample.putS3ObjectChunked(bucketName, regionName, awsAccessKey, awsSecretKey);

To test the examples on a Linux-based computer

The following instructions are for the Linux operating system.

1. In a terminal, navigate to the directory that contains AWSS3SigV4JavaSamples.zip.

2. Extract the .zip file.

3. In a text editor, open the file ./com/amazonaws/services/s3/samples/RunAllSamples.java. Update code with the following information:

   • The name of a bucket where the new object can be created.

     Note

     The examples use a virtual-hosted style request to access the bucket. To avoid potential errors, ensure that your bucket name conforms to the bucket naming rules as explained in Bucket Restrictions and Limitations in the Amazon Simple Storage Service User Guide.

   • AWS Region where the bucket resides.

     If bucket is in the US East (N. Virginia) region, use us-east-1 to specify the region. For a list of other AWS Regions, go to Amazon Simple Storage Service (S3) in the AWS General Reference.

4. Compile the source code and store the compiled classes into the bin/ directory.

   javac -d bin -source 6 -verbose com

5. Change the directory to bin/, and then run RunAllSamples.

   java com.amazonaws.services.s3.sample.RunAllSamples

   The code runs all the methods in main(). For each request, the output will show the canonical request, the string to sign, and the signature.

Examples of Signature Calculations Using C# (AWS Signature Version 4)

The C# sample that shows signature calculation can be downloaded at https://docs.aws.amazon.com/AmazonS3/latest/API/samples/AmazonS3SigV4_Samples_CSharp.zip. In Program.cs, the main() function executes sample requests to create an object, retrieve an object, and create a presigned URL for the object. The code for signature calculation is in the \Signers folder.

PutS3ObjectSample.Run(awsRegion, bucketName, "MySampleFile.txt");

Console.WriteLine("\n\n************************************************");
PutS3ObjectChunkedSample.Run(awsRegion, bucketName, "MySampleFileChunked.txt");

Console.WriteLine("\n\n************************************************");
GetS3ObjectSample.Run(awsRegion, bucketName, "MySampleFile.txt");

Console.WriteLine("\n\n************************************************");
PresignedUrlSample.Run(awsRegion, bucketName, "MySampleFile.txt");

To test the examples with Microsoft Visual Studio 2010 or later

1. Extract the .zip file.

2. Start Visual Studio, and then open the .sln file.

3. Update the App.config file with valid security credentials.

4. Update the code as follows:

   • In Program.cs, provide the bucket name and the AWS Region where the bucket resides. The sample creates an object in this bucket.

5. Run the code.

6. To verify that the object was created, copy the presigned URL that the program creates, and then paste it in a browser window.