在代码中提供临时凭证

如果默认凭证链、特定的或自定义的提供程序或提供程序链都不适用于您的应用程序，您可直接在代码中提供所需的临时凭证。这些凭证可以是上文介绍的 IAM 角色凭证，也可以是从 Amazon Security Token Service (Amazon STS) 中检索的临时凭证。如果您使用 Amazon STS 检索临时凭证，请将其提供给 Amazon Web Service 客户端，如以下代码示例所示。

以下示例使用 Amazon STS 为 IAM 代入的角色返回的临时凭证创建 Amazon S3 服务客户端。

    // The AWS IAM Identity Center identity (user) who executes this method does not have permission to list buckets.
    // The identity is configured in the [default] profile.
    public static void assumeRole(String roleArn, String roleSessionName) {
        // The IAM role represented by the 'roleArn' parameter can be assumed by identities in two different accounts
        // and the role permits the user to only list buckets.

        // The SDK's default credentials provider chain will find the single sign-on settings in the [default] profile.
        // The identity configured with the [default] profile needs permission to call AssumeRole on the STS service.
        try {
            Credentials tempRoleCredentials;
            try (StsClient stsClient = StsClient.create()) {
                AssumeRoleRequest roleRequest = AssumeRoleRequest.builder()
                        .roleArn(roleArn)
                        .roleSessionName(roleSessionName)
                        .build();

                AssumeRoleResponse roleResponse = stsClient.assumeRole(roleRequest);
                tempRoleCredentials = roleResponse.credentials();
            }
            // Use the following temporary credential items for the S3 client.
            String key = tempRoleCredentials.accessKeyId();
            String secKey = tempRoleCredentials.secretAccessKey();
            String secToken = tempRoleCredentials.sessionToken();

            // List all buckets in the account associated with the assumed role
            // by using the temporary credentials retrieved by invoking stsClient.assumeRole().
            StaticCredentialsProvider staticCredentialsProvider = StaticCredentialsProvider.create(
                    AwsSessionCredentials.create(key, secKey, secToken));
            try (S3Client s3 = S3Client.builder()
                    .credentialsProvider(staticCredentialsProvider)
                    .build()) {
                List<Bucket> buckets = s3.listBuckets().buckets();
                for (Bucket bucket : buckets) {
                    System.out.println("bucket name: " + bucket.name());
                }
            }
        } catch (StsException | S3Exception e) {
            logger.error(e.getMessage());
            System.exit(1);
        }
    }

{
	"Version": "2012-10-17",
	"Statement": [
		{
			"Effect": "Allow",
			"Action": [
				"s3:GetObject",
				"sts:AssumeRole"
			],
			"Resource": [
				"*"
			]
		}
	]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:ListAllMyBuckets"
            ],
            "Resource": [
                "*"
            ]
        }
    ]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": [
                    "arn:aws:iam::111122223333:root",
                    "arn:aws:iam::555555555555:root"
                ]
            },
            "Action": "sts:AssumeRole",
            "Condition": {}
        }
    ]
}