AWS S3 Transfer Manager ${cognito-identity.amazonaws.com:sub} 策略变量访问被拒绝

Question

我正在尝试使用传输管理器从 AWS S3 将文件从特定于用户的文件夹下载到我的 iOS 移动应用程序，如下所示：

@IBAction func download() {
    let transferManager = AWSS3TransferManager.default()!
    let downloadingFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("disney1.jpg")
    let downloadRequest = AWSS3TransferManagerDownloadRequest()!
    downloadRequest.bucket = "sidestreamx"
    // user's UUID/disney1
    downloadRequest.key = "631d121f-b294-4318-b3cd-36b3b74ebdff/disney1"
    downloadRequest.downloadingFileURL = downloadingFileURL

    transferManager.download(downloadRequest).continue(with: AWSExecutor.mainThread(), with: {
        (task: AWSTask<AnyObject>) -> Any? in
        if let error = task.error as? NSError {
            // handle error
            return nil
        }
        self.imageView.image = UIImage(contentsOfFile: downloadingFileURL.path)
        return nil
    })
}

我的 IAM 角色权限策略如下，来自 this AWS doc：

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "GetBucketListIfRequestIsForUser",
            "Action": [
                "s3:ListBucket"
            ],
            "Effect": "Allow",
            "Resource": [
                "arn:aws:s3:::sidestreamx"
            ],
            "Condition": {
                "StringLike": {
                    "s3:prefix": [
                        "${cognito-identity.amazonaws.com:sub}/*"
                    ]
                }
            }
        },
        {
            "Sid": "S3GetObjects",
            "Action": [
                "s3:GetObject",
                "s3:PutObject"
            ],
            "Effect": "Allow",
            "Resource": [
                "arn:aws:s3:::sidestreamx/${cognito-identity.amazonaws.com:sub}/*"
            ]
        }
    ]
}

我得到的响应是

<?xml version="1.0" encoding="UTF-8"?>
<Error><Code>AccessDenied</Code>
   <Message>Access Denied</Message>    
   <RequestId>E1F205B58EF4A670</RequestId>
   <HostId>dUWI8PfVZL3mJmykjhXRqvFd1yt/CqDFNlwgwD3kmLk2vrMBP6JvVgezMYSROt3KyE3dx0+3eDE=</HostId>
</Error>

用户通过 AWS Cognito 用户池和 Cognito 联合身份验证。我已经调试并提取了 JWT 令牌，并看到 sub = "631d121f-b294-4318-b3cd-36b3b74ebdff"。我什至用 Charles 看到了 Request/Response。

如果我将最后一个语句S3GetObjects中的${cognito-identity.amazonaws.com:sub}替换为631d121f-b294-4318-b3cd-36b3b74ebdff得到arn:aws:s3:::sidestreamx/631d121f-b294-4318-b3cd-36b3b74ebdff/*，它确实有效。第一条语句可以继续使用策略变量并且它仍然有效。如果我完全删除第一个语句，它将起作用！当我将策略变量添加到它开始崩溃的最后一个语句时。

我已经检查过这个 Stack Overflow question and this one，但没有用。所以是的，我不知道。我已经为此工作了将近 9 个多小时，因此我们将不胜感激任何帮助。

Answer 1

问题已解决。事实证明，${cognito-identity.amazonaws.com:sub} 并没有真正引用 JWT 令牌中的 sub。它指的是来自 credentialsProvider 的 IdentityID：

    (AWSServiceManager.default().defaultServiceConfiguration.credentialsProvider
        as! AWSCognitoCredentialsProvider).getIdentityId()
        .continue({task -> Any? in
        print("Credentials ID is \(task.result!)")
        return nil
    })

我在我的存储桶中手动创建了一个名称等于 task.result! 的文件夹（格式为 us-east-1:XXXXXXXXXXXXXXXXXX fyi），并且它有效。

AWS S3 Transfer Manager ${cognito-identity.amazonaws.com:sub} 策略变量访问被拒绝

AWS S3 Transfer Manager ${cognito-identity.amazonaws.com:sub} Policy Variable Access Denied

amazon-s3

amazon-web-services

amazon-iam

swift

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