0002-00000704

Problem description

The Signature form field in a PostObject request is left blank.

Causes

When you send a PostObject request with a signature, OSS reads the signature value from the corresponding form field to re-create and verify the signature. If the field is blank, the verification fails.

The required form field depends on the signature version:

Examples

You send a PostObject request using the default V1 signature, but the Signature form field is missing from the request.

Solutions

Calculate the signature and write it to the correct form field (Signature, x-oss-signature, or x-amz-signature) based on your signature version.

1. Create a policy encoded in UTF-8.

2. Encode the policy in Base64. The result is the value of the policy form field and serves as the string-to-sign.

3. Sign the string-to-sign with your AccessKeySecret:

   Signature = base64(hmac-sha1(AccessKeySecret, base64(policy)))

4. Write the calculated signature to the correct form field. The following example sets the Signature form field:

   Content-Disposition: form-data; name="Signature"
   {signature}
   --9431149156168

For complete parameter details, see PostObject.

References

To see complete PostObject request examples with signatures, refer to the following SDK samples:

• .NET SDK

• Java SDK

• Add signatures on the client by using JavaScript and upload data to OSS