Help Center/ Object Storage Service/ Permissions Configuration Guide (Paris Region)/ Appendix/ Bucket Policy Parameters

Updated on 2024-02-29 GMT+08:00

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Bucket Policy Parameters

A policy in JSON format is described as follows:

{ 
"Statement" : [{
     statement1
  },
  {
     statement2
  },
  ......
 ]
}

Example:

{ 
"Statement" : [{
     "Sid": "ExampleStatementID1",
     "Principal": "*",
     "Effect": "Allow",   
     "Action": "ListBucket",
     "Resource": "examplebucket",
     "Condition": "some conditions"
  },
  {
     "Sid": "ExampleStatementID2",
     "Principal": "*",
     "Effect": "Allow",   
     "Action": "PutObject",
     "Resource": "examplebucket",
     "Condition": "some conditions"
  },
......
]
}

A policy is comprised of one or more statements. Each statement contains the following elements:

**Table 1** Statement elements
Element	Description	Mandatory/Optional
Sid	ID of a statement. The value is a string that describes the statement.	Optional
Principal	Domains and users to which a statement applies. The wildcard () is supported, indicating all users. When permissions are authorized to all users under a domain, the format of Principal* is domain/domainid:user/. When permissions are authorized to a specific user under a domain, the format of Principal* is domain/domainid:user/userId or domain/domainid:user/userName.	Optional. Select either Principal or NotPrincipal.
NotPrincipal	An exception to a list of principals in the statement. You can deny access to all principals except the ones named in the NotPrincipal element. This parameter has the same value format as Principal.	Optional. Select either NotPrincipal or Principal.
Action	Actions which a statement applies to. This parameter specifies a set of all the operations supported by OBS. Its values are case insensitive. The value supports a wildcard character () that indicates all actions, for example, "Action":["List", "Get"]*.	Optional. Select either Action or NotAction.
NotAction	An exception to a list of actions in the statement. All actions are performed except the ones specified in NotAction. This parameter has the same value format as Action.	Optional. Select either Action or NotAction.
Effect	Whether the permission in a statement is allowed or denied. The value is Allow or Deny.	Mandatory
Resource	Resources on which the statement takes effect. The wildcard (*) is supported, indicating all resources.	Optional. Select either Resource or NotResource.
NotResource	An exception to a list of resources in a statement. A policy is not applied to the resources specified in NotResource. This parameter has the same value format as Resource.	Optional. Select either Resource or NotResource.
Condition	Conditions for a statement to take effect.	Optional

A statement must contain either Action or NotAction, either Resource or NotResource, and either Principal or NotPrincipal.

Principal/NotPrincipal

Principal or NotPrincipal supported by OBS includes anonymous users, specific tenants, specific users, federated users, and agencies.

All (anonymous users)
```
"Principal": {"ID": "*"}
```
In the example, the wildcard (*) is used as a placeholder for Everyone/Anonymous. We strongly recommend that you do not use wildcards in the Principal element of the role's trust policy unless you have restricted access by using the Condition element in the policy.

Specific tenants
If the tenant identifier is used as the authorizer in the policy, permissions in the policy statement can be granted to all roles, including all the users, contained in this tenant. The following example demonstrates how to specify a tenant as an authorizer.
```
"Principal": { "ID": " domain/domainIdxxxx:user/*" }
```
You can grant permissions to multiple tenants, as described in the following example:
```
"Principal": { 
  "ID": [
    "domain/domainIDxx1:user/useridxxxx",
    "domain/domainIDxx2:user/*"
  ]
}
```

Specific users

In the Principal element, user names are case sensitive.

"Principal": {"ID": "domain/domainIDxxx:user/user-name" }
"Principal": {
  "ID": [
    "domain/domainIDxxx:user/UserID1", 
    "domain/domainIDxxx:user/UserID2"
  ]
}

Federated users (using SAML identity provider)

"Principal": { "Federated": "domain/domainIDxxx:identity-provider/provider-name" }
"Principal": { "Federated": "domain/domainIDxxx:group/groupname" }

Agencies

* indicates all agencies of a tenant.

"Principal": { "ID": "domain/domainIDxxx:agency/agencyname" }
"Principal": { "ID": "domain/domainIDxxx:agency/*" }

The principals on OBS Console refer to the users which the bucket policies apply to. These users can be accounts and IAM users. Principals can be specified in either of the following ways:

Include: The policy applies to specified users.
Exclude: The policy applies to users except the specified ones.

Specifying IAM users under the current account

With Principal set to Current account, you can select one or more IAM users under this account, so the bucket policy applies to the selected IAM users.

Specifying another account

With Principal set to Other account, you can enter an account ID. If you want to grant access only to IAM users under the account, you need to enter user IDs, and use commas (,) to separate one user ID from another.

To obtain the account ID and user ID, log in to the console as an IAM user and go to the My Credentials page.

Specifying anonymous users

To grant the bucket access to anyone, set Principal to Other account and enter a wildcard (*) as the account ID.

Exercise caution when granting bucket access permissions to anonymous users. If you grant the access permissions to anonymous users, anyone can access your bucket, and all the traffic and storage fees incurred will be borne by the bucket owner. You are advised to set restrictions on access requests. For example, you can allow the access requests from only one IP address.

Action/NotAction

If a policy applies to a bucket, configure bucket-related actions; if the policy applies to the objects in a bucket, configure object-related actions.

Actions can be specified in either of the following ways:

Include: The bucket policy applies to specified actions.
Exclude: The bucket policy applies to actions except the specified ones.

Bucket Actions

**Table 2** Action description
Type	Value	Description
General	*	Indicates that all operations can be performed on a resource.
	Get*	Indicates that all GET operations can be performed on a resource.
	Put*	Indicates that all PUT operations can be performed on a resource.
	List*	Indicates that all LIST operations can be performed on a resource.
Bucket	CreateBucket	Creates a bucket.
	DeleteBucket	Deletes a bucket.
	ListBucket	Lists objects in a bucket, and obtains the bucket metadata.
	ListBucketVersions	Lists versioned objects in a bucket.
	ListBucketMultipartUploads	Lists multipart upload tasks.
	GetBucketAcl	Gets the bucket ACL information.
	PutBucketAcl	Configures a bucket ACL.
	GetBucketCORS	Gets the CORS configuration of a bucket.
	PutBucketCORS	Configures CORS for a bucket.
	GetBucketVersioning	Gets the bucket versioning information.
	PutBucketVersioning	Configures versioning for a bucket.
	GetBucketLocation	Gets the bucket location.
	GetBucketLogging	Gets the bucket logging information.
	PutBucketLogging	Configures logging for a bucket.
	GetBucketWebsite	Obtains the static website configuration information of a bucket.
	PutBucketWebsite	Configures static website hosting for a bucket.
	DeleteBucketWebsite	Cancels the static website hosting of a bucket.
	GetLifecycleConfiguration	Obtains the lifecycle rules of a bucket.
	PutLifecycleConfiguration	Configures a lifecycle rule for a bucket.

Object Actions

**Table 3** Action description
Type	Value	Description
General	*	Indicates that all operations can be performed on a resource.
	Get*	Indicates that all GET operations can be performed on a resource.
	Put*	Indicates that all PUT operations can be performed on a resource.
	List*	Indicates that all LIST operations can be performed on a resource.
Object	GetObject	Gets the content and metadata of an object.
	GetObjectVersion	Gets the content and metadata of a specified object version.
	PutObject	Performs PUT upload, POST upload, multipart upload, initialization of uploaded parts, and merging of parts.
	GetObjectAcl	Gets the object ACL information.
	GetObjectVersionAcl	Gets the ACL information of a specified object version.
	PutObjectAcl	Configures the ACL for an object.
	PutObjectVersionAcl	Configures the ACL for a specified object version.
	DeleteObject	Deletes an object.
	DeleteObjectVersion	Deletes a specified object version.
	ListMultipartUploadParts	Lists uploaded parts.
	AbortMultipartUpload	Cancels a multipart upload.

Resource/NotResource

The resources supported by OBS are as follows:

bucketname (bucket operation): The Action drop-down list box contains the list of supported bucket actions. If you want to perform the listed operations on the bucket, set Resource to the bucket name.
bucketname/objectname (object operation): The Action drop-down list box contains the list of supported object actions. If you want to respond to an object in a bucket, set Resource to bucketname/objectname. objectname supports wildcards. For example, if you have permissions on the directory object in a bucket, set Resource to "bucketname/directory/*". If you have permissions on all the objects in a bucket, set Resource to "bucketname/*". If permissions for both a bucket and its objects need to be granted, set Resource to ["examplebucket/*","examplebucket"].

The following example policy grants all operation permissions on examplebucket (including the bucket and its objects) to user1 whose user ID is 71f3901173514e6988115ea2c26d1999 under account b4bf1b36d9ca43d984fbcb9491b6fce9 (account ID).

{ 
    "Statement":[ 
    { 
      "Sid":"test", 
      "Effect":"Allow", 
      "Principal": {"ID": ["domain/b4bf1b36d9ca43d984fbcb9491b6fce9:user/71f3901173514e6988115ea2c26d1999"]}, 
      "Action":["*"], 
      "Resource":["examplebucket/*","examplebucket"]
    } 
  ] 
}

On OBS Console, you can apply a bucket policy to the following resources: the current bucket, and all objects in a bucket.

Resources can be specified in either of the following ways:

Include: The bucket policy applies to specified OBS resources.
Exclude: The bucket policy applies to OBS resources except the specified ones.

Applying a bucket policy to a bucket

To apply a bucket policy to the current bucket, keep the resource text box empty. When configuring actions for the policy, select bucket related actions.

Applying a bucket policy to specified objects

To apply the bucket policy to specified objects in a bucket, object-related actions must be configured in the policy. The configuration format is as follows:

For an object, enter the object name (including its folder name if any). For example, if the specified resource is the example.jpg file in the imgs-folder folder in the bucket, enter the following content in the resource text box:
imgs-folder/example.jpg
For an object set, the wildcard asterisk (*) should be used. The asterisk (*) indicates an empty string or any combination of multiple characters. The format rules are as follows:
- Use only one asterisk (*) to indicate all objects in a bucket.
- Use Object name prefix* to indicate objects starting with this prefix in a bucket. Example:
  imgs*
- Use *Object name suffix to indicate objects ending with this suffix in a bucket. Example:
  *.jpg

Use commas (,) to separate one object (or object set) from another.

Condition

In addition to the effect, principals, resources, and actions, you can also specify the conditions under which a bucket policy takes effect. The bucket policy takes effect only when its condition expressions match values contained in the request. Conditions are optional. You can choose whether to configure them.

For example, if account A needs to have full control over an object uploaded by account B to bucket example of account A, the x-obs-acl key must be specified in the upload request and the policy effect must be set to Allow for account A. The complete condition expression is as follows:

Condition Operator	Key	Value
StringEquals	x-obs-acl	bucket-owner-full-control

A condition consists of three parts: condition operator, key, and value. If there are multiple identical keys in the same condition operator, only the last key is retained. Condition operators and keys are mutually restricted. If you select a condition operator of the string type, for example, StringEquals, the key can only be of the string type, for example, UserAgent. Likewise, if a key of the date type is selected, for example, CurrentTime, the condition operator can only be of the date type, for example, DateEquals.

Condition operators
A condition operator, a condition key, and a condition value together constitute a complete condition statement. A policy can be applied only when its request conditions are met. Table 4 lists the condition operators available for statements. String condition operators are not case-sensitive unless otherwise specified.

**Table 4** Condition operators
Type	Element	Description
String	StringEquals	Strict matching. Short version: streq
	StringNotEquals	Strict negated matching. Short version: strneq
	StringEqualsIgnoreCase	Strict matching, ignoring case. Short version: streqi
	StringNotEqualsIgnoreCase	Strict negated matching, ignoring case. Short version: strneqi
	StringLike	Loose case-sensitive matching. The values can include a multi-character match wildcard (*) or a single-character match wildcard (?) anywhere in the string. Short version: strl
	StringNotLike	Negated loose case-sensitive matching. The values can include a multi-character match wildcard (*) or a single-character match wildcard (?) anywhere in the string. Short version: strnl
Numeric	NumericEquals	Strict matching. Short version: numeq Numeric indicates a data type expressed in numbers.
	NumericNotEquals	Strict negated matching. Short version: numneq
	NumericLessThan	"Less than" matching. Short version: numlt
	NumericLessThanEquals	"Less than or equals" matching. Short version: numlteq
	NumericGreaterThan	"Greater than" matching. Short version: numgt
	NumericGreaterThanEquals	"Greater than or equals" matching. Short version: numgteq
Date	DateEquals	Strict matching. Short version: dateeq
	DateNotEquals	Strict negated matching. Short version: dateneq
	DateLessThan	The date is earlier than a specific date. Short version: datelt
	DateLessThanEquals	The date is earlier than or equal to a specific date. Short version: datelteq
	DateGreaterThan	The date is later than a specific date. Short version: dategt
	DateGreaterThanEquals	The date is later than or equal to a specific date. Short version: dategteq
Boolean	Bool	Strict Boolean matching
IP address	IpAddress	Specified IP address or IP address range
IP address	NotIpAddress	All IP addresses excluding the specified IP address or IP address range

Elements in a condition are case sensitive. The date format complies with the ISO 8601 standard, for example, 2015-07-01T12:00:00Z.

Each condition can contain multiple key-value pairs. The Condition combination in the following figure indicates that the request time ranges from 2015-07-01T12:00:00Z to 2018-04-16T15:00:00Z and the request IP address range is 192.168.176.0/24 or 192.168.143.0/24.

"Condition" : { 
  "DateGreaterThan" : { 
  "CurrentTime" : "2015-07-01T12:00:00Z" 
  }, 
  "DateLessThan": { 
  "CurrentTime" : "2018-04-16T15:00:00Z" 
  }, 
  "IpAddress" : { 
  "SourceIp" : ["192.168.176.0/24","192.168.143.0/24"] 
  } 
}

Condition keys

Keys in a condition can be classified into three types: general keys, keys related to bucket actions, and keys related to object actions.

The following table lists the keys that are not related to actions.

**Table 5** General keys
Key	Type	Description
CurrentTime	Date	Date when the request is received by the server. The date format must comply with ISO 8601.
EpochTime	Numeric	Time when the request is received by the server, which is expressed as seconds since 1970.01.01 00:00:00 UTC, regardless of the leap seconds
SecureTransport	Bool	Whether requests are encrypted using SSL NOTE: The value can be either true or false. Any other values you enter will become false by default.
SourceIp	IP address	Source (client) IP address of the request
UserAgent	String	Requested client software agent
Referer	String	Link from which the request is sent

Keys in a condition must be used in certain actions. The following table lists the mapping between actions and the keys in a condition.

**Table 6** Keys related to bucket actions
Action	Optional Key	Description	Remarks
ListBucket	prefix	Type: String. Lists objects that begin with the specified prefix.	If prefix, delimiter, and max-keys are configured, the key-value pair meeting the conditions must be specified in the List operation for the bucket policy to take effect. For example, if a bucket policy (with the condition operator set to NumericEquals, the key to max-keys, and the value to 100) that allows anonymous users to read data is configured for a bucket, the anonymous users must add ?max-keys=100 to the end of the bucket domain name for listing objects. The listed objects are the first 100 objects in alphabetic order.
	delimiter	Type: String. Groups objects in a bucket.
	max-keys	Type: Numeric. Sets the maximum number of objects. Returned objects are listed in alphabetic order.
ListBucketVersions	prefix	Type: String. Lists multi-version objects whose name starts with the specified prefix.
	delimiter	Type: String. Groups objects of different versions in a bucket.
	max-keys	Type: Numeric. Sets the maximum number of objects. Returned objects are listed in alphabetic order.
PutBucketAcl	x-obs-acl	Type: String. Configures the bucket ACL. When modifying a bucket ACL, you can use the request that contains a canned ACL setting in its header. Value options of a canned ACL setting: private\|public-read\|public-read-write\|bucketowner-read\|log-delivery-write.	None

**Table 7** Keys related to object actions
Action	Optional Key	Description
PutObject	x-obs-acl	Type: String. Configures the object ACL. When uploading an object, you can use the request that contains a canned ACL setting in its header. Value options of a canned ACL setting: private\|public-read\|public-read-write\|bucketowner-read\|bucket-owner-full-control\|log-delivery-write.
	x-obs-copy-source	Type: String. Specifies names of the source bucket and the source object. Format: /bucketname/keyname
	x-obs-metadata-directive	Type: String. Specifies whether to copy the metadata from the source object or replace with the metadata in the request. The value can be COPY or REPLACE.
	x-obs-server-side-encryption	Type: String. Specifies that objects in a bucket are encrypted using SSE-KMS before they are stored. The value is kms.
PutObjectAcl	x-obs-acl	Type: String. Configures the object ACL. When uploading an object, you can use the request that contains a canned ACL setting in its header. Value options of a canned ACL setting: private\|public-read\|public-read-write\|bucketowner-read\|bucket-owner-full-control\|log-delivery-write.
GetObjectVersion	versionId	Type: String. Obtains the object with the specified version ID.
GetObjectVersionAcl	versionId	Type: String. Obtains the ACL of the object with the specified version ID.
PutObjectVersionAcl	versionId	Type: String. Specifies a version ID.
PutObjectVersionAcl	x-obs-acl	Type: String. Configures the ACL of the object with the specified version ID. When uploading an object, you can use the request that contains a canned ACL setting in its header. Value options of a canned ACL setting: private\|public-read\|public-read-write\|bucketowner-read\|bucket-owner-full-control\|log-delivery-write.
DeleteObjectVersion	versionId	Type: String. Deletes the object with the specified version ID.

Policy Permission Judgment Logic

A policy may pose any of the three results for each statement: Explicit Deny, Allow, and Default Deny. If a bucket policy contains multiple statements, the policy determines which statement prevails according to the following rules:

1. If conditions in any statement of a policy are not met, the policy poses a default deny result.

2. An explicit deny overrides an allow.

3. An allow overrides a default deny.

4. Statements can be in any order in a policy.

**Table 8** Statement results
Result	Description
explicit deny	A statement defines effect="deny". All requests for resources to which the statement applies are denied. No permission is returned.
allow	A statement defines effect="allow". All requests for resources to which the statement applies are allowed.
default deny	Conditions defined in a statement are not met. Requests are denied.

If an ACL and a bucket policy are applied together to an account, an explicit deny in the bucket policy overrides the allow in the ACL.

If a bucket policy and an IAM policy are applied together to an account, an explicit deny overrides the allow, and an allow overrides the default deny.

SSE-KMS server-side encrypted object does not support Bucket ACL/Policy for cross-tenant authorization.

Parent topic: Appendix

Previous topic: Appendix

Next topic: Relationship Between Bucket Policies and Bucket ACLs

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