tencent cloud

Overview

Conditions are part of the access policy language. A complete condition includes the following elements:

• Condition key: Specifies the type of the condition, for example, user access source IP and authorization time.
• Condition operator: Specifies the condition determination method.
• Condition value: Specifies the value of the condition key.

For more information, see Conditions of Access Management.

Sample Condition

In the following sample bucket policy, the condition specifies that the cos:PutObject authorization operation can be completed only in the 10.217.182.3/24 or 111.21.33.72/24 IP range. In the condition:

• The condition key is qcs:ip, indicating that the condition type is IP.
• The operator is ip_equal, indicating that the condition determination method is to determine whether IP addresses match.
• The condition value is the ["10.217.182.3/24","111.21.33.72/24"] array, listing the specified values for condition determination. If the user's IP is in any of the specified IP ranges in the array, the condition is determined as true.

{
  "version":"2.0",
  "statement":[
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"allow",
          "Action":[
              "name/cos:PutObject"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "ip_equal":{
                  "qcs:ip":[
                      "10.217.182.3/24",
                      "111.21.33.72/24"
                  ]
              }
          }
      }
  ]
}

Condition Keys Supported by COS

Note：

The condition keys qcs:ip, vpc:requester_vpc, and cos:content-type can be used in all regions. The rest condition keys currently can be used in only the Chengdu, Guangzhou, Shanghai, Jakarta, Sao Paulo, Virginia, Tokyo, and Seoul regions, and will be supported in other regions in the future.

COS supports two types of condition keys: condition keys applicable to all requests, including IP, VPC, and HTTPS, and condition keys from request headers and request parameters and generally applicable only to requests that need to carry the request headers or request parameters. For the descriptions and use cases of these condition keys, see Descriptions and Use Cases of Condition Keys.

Note：

Conditions and condition keys are applicable only to the access management of user requests. When the lifecycle and cross-bucket replication rules are valid, actions such as deletion and replication are initiated by COS rather than users and therefore are not in the applicable scope of condition keys.

Condition keys applicable to all requests

Condition keys applicable to all requests are qcs:ip, qcs:vpc, and cos:secure-transport, which indicate the source IP range of the request, source VPC ID of the request, and whether the request uses HTTPS, respectively.

Condition Key	Applicable Request	Description	Type
cos:secure-transport	All requests	Whether the request uses HTTPS.	Boolean
qcs:ip	All requests	Source IP range of the request.	IP
qcs:vpc	All requests	Source VPC ID of the request.	String

Condition keys from request headers and request parameters

Because different requests have different request headers (Header) and request parameters (Param), condition keys from request headers and request parameters are applicable only to requests that contain such request headers or request parameters.

For example, the condition key cos:content-type is applicable to upload requests (such as PutObject) that need to use the request header Content-Type, while the condition key cos:response-content-type is applicable only to GetObject requests because only GetObject requests support the request parameter response-content-type.

The table below lists the condition keys from request headers and request parameters and the applicable requests.

Condition Key	Applicable Request	Check Request Header or Request Parameter	Type
cos:x-cos-storage-class	PutObject PostObject InitiateMultipartUpload AppendObject	Request header: x-cos-storage-class	String
cos:versionid	GetObject DeleteObject PostObjectRestore PutObjectTagging GetObjectTagging DeleteObjectTagging HeadObject	Request parameter: versionId	String
cos:prefix	GetBucket (List Objects) GET Bucket Object versions List Multipart Uploads ListLiveChannels	Request parameter: prefix	String
cos:x-cos-acl	PutObject PostObject PutObjectACL PutBucket PutBucketACL AppendObject Initiate Multipart Upload	Request header: x-cos-acl	String
cos:content-length	This request header has wide application, typically requests with request bodies.	Request header: Content-Length	Numeric
cos:content-type	This request header has wide application, typically requests with request bodies.	Request header: Content-Type	String
cos:response-content-type	GetObject	Request parameter: response-content-type	String
cos:x-cos-forbid-overwrite	PutObject PostObject InitMultipartUpload CompleteMultipartUpload	Request header: x-cos-forbid-overwrite	String

Condition Operators

COS supports the following condition operators, which are applicable to condition keys of the String, Numeric, Boolean, and IP types.

Condition Operator	Description	Type
string_equal	String equal to (case-sensitive).	String
string_not_equal	String not equal to (case-sensitive).	String
ip_equal	IP equal to.	IP
ip_not_equal	IP not equal to.	IP
numeric_equal	Number equal to.	Numeric
numeric_not_equal	Number not equal to.	Numeric
numeric_greater_than	Number greater than.	Numeric
numeric_greater_than_equal	Number greater than or equal to.	Numeric
numeric_less_than	Number less than.	Numeric
numeric_less_than_equal	Number less than or equal to.	Numeric

_if_exist

You can add _if_exist to the end of all the preceding condition operators to form new condition operators, such as string_equal_if_exist. The differences between condition operators with and without _if_exist are as follows:

• For a condition operator without _if_exist, such as string_equal, it is considered that the condition is met (False) by default if the request does not contain the specified request header or parameter.
• For a condition operator with _if_exist, such as string_equal_if_exist, it is considered that the condition is met (True) by default if the request does not contain the specified request header or parameter.

Samples

Sample 1: Allowing downloading objects of a specified version

In the bucket policy in this example, Effect is allow, allowing GetObject requests where the request parameter versionid is MTg0NDUxNTc1NjIzMTQ1MDAwODg. According to the allow authorization policy, if the condition is met (True), the request will be allowed; if the condition is not met (False), the request will not be allowed and will fail.

{
  "version":"2.0",
  "Statement":[
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"allow",
          "Action":[
              "name/cos:GetObject"
          ],
          "Condition":{
              "string_equal":{
                  "cos:versionid":"MTg0NDUxNTc1NjIzMTQ1MDAwODg"
              }
          },
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ]
      }
  ]
}

The table below lists the condition meeting and request allowing details of the condition operators string_equal and string_equal_if_exist.

Condition Operator	Request	Condition Met	Request Allowed
string_equal	Without versionid.	FALSE	No
string_equal_if_exist	Without versionid.	TRUE	Yes
string_equal	With versionid, whose value is specified.	TRUE	Yes
string_equal_if_exist	With versionid, whose value is specified.	TRUE	Yes
string_equal	With versionid, whose value is not specified.	FALSE	No
string_equal_if_exist	With versionid, whose value is not specified.	FALSE	No

Sample 2: Denying downloading objects of a specified version

In the bucket policy in this example, Effect is deny, disallowing GetObject requests where the request parameter versionid is MTg0NDUxNTc1NjIzMTQ1MDAwODg. According to the deny authorization policy, if the condition is met (True), the request will fail; if the condition is not met (False), the request will not be denied.

{
  "version":"2.0",
  "Statement":[
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"deny",
          "Action":[
              "name/cos:GetObject"
          ],
          "Condition":{
              "string_equal":{
                  "cos:versionid":"MTg0NDUxNTc1NjIzMTQ1MDAwODg"
              }
          },
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ]
      }
  ]
}

The table below lists the condition meeting and request denial details of the condition operators string_equal and string_equal_if_exist.

Condition Operator	Request	Condition Met	Request Denied
string_equal	Without versionid.	FALSE	No
string_equal_if_exist	Without versionid	TRUE	Yes
string_equal	With versionid, whose value is specified.	TRUE	Yes
string_equal_if_exist	With versionid, whose value is specified.	TRUE	Yes
string_equal	With versionid, whose value is not specified.	FALSE	No
string_equal_if_exist	With versionid, whose value is not specified.	FALSE	No

Notes

Special characters require URL encoding

Special characters in request parameters all require URL encoding, and therefore bucket policies that use condition keys from the request parameters require URL encoding as well. For example, if you are to use the cos:response-content-type condition key in a bucket policy, the condition value image/jpeg must be encoded (URL encoding) into image%2Fjpeg before it is entered into the bucket policy.

Principle of least privilege and no * wildcard

When using condition keys, comply with the principle of least privilege, add only actions for which you want to set permissions, and avoid using the * wildcard. Misuse of the * wildcard may cause some requests to fail. In the sample below, requests other than GetObject do not support using the request parameter response-content-type.

For "deny + string_equal_if_exist", if the operator does not exist in the request, it is considered true by default. Therefore, when you initiate requests such as PutObject and PutBucket, the deny statement will be met and the requests will be denied.

For "allow + string_equal", if the condition key does not exist in the request, it is considered false by default. Therefore, when you initiate requests such as PutObject and PutBucket, the allow statement will not be met and the requests will not be allowed.

{
  "version":"2.0",
  "Statement":[
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"allow",
          "Action":[
              "*"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "string_equal":{
                  "cos:response-content-type":"image%2Fjpeg"
              }
          }
      },
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"deny",
          "Action":[
              "*"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "string_not_equal_if_exist":{
                  "cos:response-content-type":"image%2Fjpeg"
              }
          }
      }
  ]
}

Alternatively, you can use "allow + string_equal_if_exist" and "deny + string_not_equal" to allow requests without the response-content-type request parameter.

For "deny + string_equal", if the operator does not exist in the request, it is considered false by default. Therefore, when you initiate requests such as PutObject and PutBucket, the deny statement will not be met and the requests will not be denied.

For "allow + string_equal_if_exist", if the condition key does not exist in the request, it is considered true by default. Therefore, when you initiate requests such as PutObject and PutBucket, the allow statement will be met and the requests will be allowed.

However, if you use condition operators in this way, you will not be able to restrict whether a GetObject request carries the response-content-type request parameter. A GetObject request without the response-content-type request parameter will be allowed by default like other requests. Only when the GetObject request carries the response-content-type request parameter, you can use your specified condition to check whether the content of the request parameter is the same as what you expect to implement conditional authorization.

{
  "version":"2.0",
  "Statement":[
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"allow",
          "Action":[
              "*"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "string_equal_if_exist":{
                  "cos:response-content-type":"image%2Fjpeg"
              }
          }
      },
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"deny",
          "Action":[
              "*"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "string_not_equal":{
                  "cos:response-content-type":"image%2Fjpeg"
              }
          }
      }
  ]
}

Therefore, the more secure way is to comply with the principle of least privilege and restrict the action to GetObject requests without using the * wildcard.

As shown in the sample policy below, the policy condition strictly specifies that authorization is performed only for GetObject requests carrying the response-content-type request parameter with value image%2Fjpeg.

Other requests are not affected by the policy in this example, and can be authorized separately based on the principle of least privilege.

{
  "version":"2.0",
  "statement":[
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"allow",
          "Action":[
              "name/cos:GetObject"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "string_equal":{
                  "cos:response-content-type":"image%2Fjpeg"
              }
          }
      },
      {
          "Principal":{
              "qcs":[
                  "qcs::cam::uin/1250000000:uin/1250000001"
              ]
          },
          "Effect":"deny",
          "Action":[
              "name/cos:GetObject"
          ],
          "Resource":[
              "qcs::cos:ap-guangzhou:uid/1250000000:examplebucket-1250000000/*"
          ],
          "Condition":{
              "string_not_equal_if_exist":{
                  "cos:response-content-type":"image%2Fjpeg"
              }
          }
      }
  ]
}