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Amazon Simple Storage Service
Developer Guide (API Version 2006-03-01)

Specifying a Principal in a Policy

The Principal element specifies the user, account, service, or other entity that is allowed or denied access to a resource. The following are examples of specifying Principal. For more information, see Principal in the IAM User Guide.

  • To grant permissions to an AWS account, identify the account using the following format.

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    "AWS":"account-ARN"

    For example:

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    "Principal":{"AWS":"arn:aws:iam::AccountNumber-WithoutHyphens:root"}

    Amazon S3 also supports a canonical user ID, which is an obfuscated form of the AWS account ID. You can specify this ID using the following format.

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    "CanonicalUser":"64-digit-alphanumeric-value"

    For example:

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    "Principal":{"CanonicalUser":"64-digit-alphanumeric-value"}

    For information about how to find the canonical user ID for your account, see Finding Your Account Canonical User ID.

  • To grant permission to an IAM user within your account, you must provide an "AWS":"user-ARN" name-value pair.

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    "Principal":{"AWS":"arn:aws:iam::account-number-without-hyphens:user/username"}
  • To grant permission to everyone, also referred as anonymous access, you set the wildcard, "*", as the Principal value. For example, if you configure your bucket as a website, you want all the objects in the bucket to be publicly accessible. The following are equivalent:

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    "Principal":"*"
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    "Principal":{"AWS":"*"}

    Warning

    Use caution when granting anonymous access to your S3 bucket. When you grant anonymous access, anyone in the world can access your bucket. We highly recommend that you never grant any kind of anonymous write access to your S3 bucket.

  • You can require that your users access your Amazon S3 content by using CloudFront URLs (instead of Amazon S3 URLs). To do this, create a CloudFront origin access identity (OAI), and then change the permissions either on your bucket or on the objects in your bucket. The format for specifying the OAI in a Principal statement is as follows:

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    "Principal":{"CanonicalUser":"Amazon S3 Canonical User ID assigned to origin access identity"}

    For more information, see Using an Origin Access Identity to Restrict Access to Your Amazon S3 Content in the Amazon CloudFront Developer Guide.

For more information about other access policy language elements, see Access Policy Language Overview.