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SSE-KMS

In SSE-KMS mode, OBS uses the keys provided by KMS for server-side encryption. When an object encrypted using SSE-KMS is added to a bucket in a region for the first time, OBS creates a default customer master key (CMK), which is used to encrypt and decrypt the keys provided by KMS. Only users with the tenant_admin role can use SSE-KMS interfaces. The SSE-KMS mode does not support the keys created by customers. The bucket ACL and policy do not allow cross-tenant authorized access to objects encrypted using SSE-KMS. OBS does not support KMS with multiple projects.

Table 1 lists two headers that are added to support SSE-KMS in SSE-KMS mode.

Table 1 Headers needed in SSE-KMS mode

Header	Description
x-amz-server-side-encryption	Indicates that SSE-KMS is used. Objects are encrypted using SSE-KMS. Example: x-amz-server-side-encryption:aws:kms
x-amz-server-side-encryption-aws-kms-key-id	Indicates the master key ID of an encrypted object. This header is used in SSE-KMS mode. If the customer does not provide the master key, the default master key will be used. Example: x-amz-server-side-encryption-aws-kms-key-id:arn:aws:kms:sichuan:domainiddomainiddomainiddoma0001:key/4f1cd4de-ab64-4807-920a-47fc42e7f0d0 Note: sichuan: indicates the region name. Set the value based on site requirements. domainiddomainiddomainiddoma0001: indicates the tenant ID. Set the value based on site requirements. key/4f1cd4de-ab64-4807-920a-47fc42e7f0d0: indicates the key ID. Set the value based on site requirements.

Table 2 Interfaces to which the newly added headers apply

Interface
PUT Object
POST Object
PUT Object - Copy (the newly added headers apply to target objects)
Initiate Multipart Upload

OBS supports bucket policies. If you want to restrict server-side encryption for all objects stored in a bucket, you can use bucket policies. For example, if an object upload request does not contain x-amz-server-side-encryption:"aws:kms", the header for requesting server-side encryption (SSE-KMS), the following bucket policy rejects the upload request:

{
"Version":"2008-10-17",
"Id":"PutObjPolicy",
"Statement": [
        {
            "Sid": "DenyUnEncryptedObjectUploads",
            "Effect": "Deny",
            "Principal": "*",
            "Action": "s3:PutObject",
            "Resource": "arn:aws:s3:::YourBucket/*",
            "Condition": {
                "StringNotEquals": {
                    "s3:x-amz-server-side-encryption": "aws:kms"
                }
            }
        }
    ]
}

Parent topic: Server-Side Encryption