Setting signed cookies using a custom policy - Amazon CloudFront

Setting signed cookies using a custom policy

To set a signed cookie that uses a custom policy, complete the following steps.

Example Set-Cookie headers for one signed cookie when you're using the domain name that is associated with your distribution in the URLs for your files:

Set-Cookie: CloudFront-Policy=eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cDovL2QxMTExMTFhYmNkZWY4LmNsb3VkZnJvbnQubmV0L2dhbWVfZG93bmxvYWQuemlwIiwiQ29uZGl0aW9uIjp7IklwQWRkcmVzcyI6eyJBV1M6U291cmNlSXAiOiIxOTIuMC4yLjAvMjQifSwiRGF0ZUxlc3NUaGFuIjp7IkFXUzpFcG9jaFRpbWUiOjE0MjY1MDAwMDB9fX1dfQ__; Domain=d111111abcdef8.cloudfront.net; Path=/; Secure; HttpOnly Set-Cookie: CloudFront-Signature=dtKhpJ3aUYxqDIwepczPiDb9NXQ_; Domain=d111111abcdef8.cloudfront.net; Path=/; Secure; HttpOnly Set-Cookie: CloudFront-Key-Pair-Id=K2JCJMDEHXQW5F; Domain=d111111abcdef8.cloudfront.net; Path=/; Secure; HttpOnly

Example Set-Cookie headers for one signed cookie when you're using the alternate domain name example.org in the URLs for your files:

Set-Cookie: CloudFront-Policy=eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cDovL2QxMTExMTFhYmNkZWY4LmNsb3VkZnJvbnQubmV0L2dhbWVfZG93bmxvYWQuemlwIiwiQ29uZGl0aW9uIjp7IklwQWRkcmVzcyI6eyJBV1M6U291cmNlSXAiOiIxOTIuMC4yLjAvMjQifSwiRGF0ZUxlc3NUaGFuIjp7IkFXUzpFcG9jaFRpbWUiOjE0MjY1MDAwMDB9fX1dfQ__; Domain=example.org; Path=/; Secure; HttpOnly Set-Cookie: CloudFront-Signature=dtKhpJ3aUYxqDIwepczPiDb9NXQ_; Domain=example.org; Path=/; Secure; HttpOnly Set-Cookie: CloudFront-Key-Pair-Id=K2JCJMDEHXQW5F; Domain=example.org; Path=/; Secure; HttpOnly

If you want to use an alternate domain name such as example.com in URLs, you must add the alternate domain name to your distribution regardless of whether you specify the Domain attribute. For more information, see Alternate domain names (CNAMEs) in the topic Values that you specify when you create or update a distribution.

Creating a policy statement for a signed cookie that uses a custom policy

To create a policy statement for a custom policy, complete the following steps. For several example policy statements that control access to files in a variety of ways, see Example policy statements for a signed cookie that uses a custom policy.

To create the policy statement for a signed cookie that uses a custom policy
  1. Construct the policy statement using the following JSON format.

    { "Statement": [ { "Resource": "URL of the file", "Condition": { "DateLessThan": { "AWS:EpochTime":required ending date and time in Unix time format and UTC }, "DateGreaterThan": { "AWS:EpochTime":optional beginning date and time in Unix time format and UTC }, "IpAddress": { "AWS:SourceIp": "optional IP address" } } } ] }

    Note the following:

    • You can include only one statement.

    • Use UTF-8 character encoding.

    • Include all punctuation and parameter names exactly as specified. Abbreviations for parameter names are not accepted.

    • The order of the parameters in the Condition section doesn't matter.

    • For information about the values for Resource, DateLessThan, DateGreaterThan, and IpAddress, see Values that you specify in the policy statement for a custom policy for signed cookies.

  2. Remove all white space (including tabs and newline characters) from the policy statement. You might have to include escape characters in the string in application code.

  3. Base64-encode the policy statement using MIME base64 encoding. For more information, see Section 6.8, Base64 Content-Transfer-Encoding in RFC 2045, MIME (Multipurpose Internet Mail Extensions) Part One: Format of Internet Message Bodies.

  4. Replace characters that are invalid in a URL query string with characters that are valid. The following table lists invalid and valid characters.

    Replace these invalid characters With these valid characters

    +

    - (hyphen)

    =

    _ (underscore)

    /

    ~ (tilde)

  5. Include the resulting value in your Set-Cookie header after CloudFront-Policy=.

  6. Create a signature for the Set-Cookie header for CloudFront-Signature by hashing, signing, and base64-encoding the policy statement. For more information, see Creating a signature for a signed cookie that uses a custom policy.

Values that you specify in the policy statement for a custom policy for signed cookies

When you create a policy statement for a custom policy, you specify the following values.

Resource

The base URL including your query strings, if any:

https://d111111abcdef8.cloudfront.net/images/horizon.jpg?size=large&license=yes

Important

If you omit the Resource parameter, users can access all of the files associated with any distribution that is associated with the key pair that you use to create the signed URL.

You can specify only one value for Resource.

Note the following:

  • Protocol – The value must begin with http:// or https://.

  • Query string parameters – If you have no query string parameters, omit the question mark.

  • Wildcards – You can use the wildcard character that matches zero or more characters (*) or the wild-card character that matches exactly one character (?) anywhere in the string. For example, the value:

    https://d111111abcdef8.cloudfront.net/*game_download.zip*

    would include (for example) the following files:

    • https://d111111abcdef8.cloudfront.net/game_download.zip

    • https://d111111abcdef8.cloudfront.net/example_game_download.zip?license=yes

    • https://d111111abcdef8.cloudfront.net/test_game_download.zip?license=temp

  • Alternate domain names – If you specify an alternate domain name (CNAME) in the URL, you must specify the alternate domain name when referencing the file in your webpage or application. Do not specify the Amazon S3 URL for the file.

DateLessThan

The expiration date and time for the URL in Unix time format (in seconds) and Coordinated Universal Time (UTC). Do not enclose the value in quotation marks.

For example, March 16, 2015 10:00 am UTC converts to 1426500000 in Unix time format.

For more information, see When does CloudFront check the expiration date and time in a signed cookie?.

DateGreaterThan (Optional)

An optional start date and time for the URL in Unix time format (in seconds) and Coordinated Universal Time (UTC). Users are not allowed to access the file on or before the specified date and time. Do not enclose the value in quotation marks.

IpAddress (Optional)

The IP address of the client making the GET request. Note the following:

  • To allow any IP address to access the file, omit the IpAddress parameter.

  • You can specify either one IP address or one IP address range. For example, you can't set the policy to allow access if the client's IP address is in one of two separate ranges.

  • To allow access from a single IP address, you specify:

    "IPv4 IP address/32"

  • You must specify IP address ranges in standard IPv4 CIDR format (for example, 192.0.2.0/24). For more information, go to RFC 4632, Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan, https://tools.ietf.org/html/rfc4632.

    Important

    IP addresses in IPv6 format, such as 2001:0db8:85a3::8a2e:0370:7334, are not supported.

    If you're using a custom policy that includes IpAddress, do not enable IPv6 for the distribution. If you want to restrict access to some content by IP address and support IPv6 requests for other content, you can create two distributions. For more information, see Enable IPv6 in the topic Values that you specify when you create or update a distribution.

Example policy statements for a signed cookie that uses a custom policy

The following example policy statements show how to control access to a specific file, all of the files in a directory, or all of the files associated with a key pair ID. The examples also show how to control access from an individual IP address or a range of IP addresses, and how to prevent users from using the signed cookie after a specified date and time.

If you copy and paste any of these examples, remove any white space (including tabs and newline characters), replace the values with your own values, and include a newline character after the closing brace ( } ).

For more information, see Values that you specify in the policy statement for a custom policy for signed cookies.

Example policy statement: accessing one file from a range of IP addresses

The following example custom policy in a signed cookie specifies that a user can access the file https://d111111abcdef8.cloudfront.net/game_download.zip from IP addresses in the range 192.0.2.0/24 until January 1, 2023 10:00 am UTC:

{ "Statement": [ { "Resource": "https://d111111abcdef8.cloudfront.net/game_download.zip", "Condition": { "IpAddress": { "AWS:SourceIp": "192.0.2.0/24" }, "DateLessThan": { "AWS:EpochTime": 1357034400 } } } ] }

Example policy statement: accessing all files in a directory from a range of IP addresses

The following example custom policy allows you to create signed cookies for any file in the training directory, as indicated by the * wildcard character in the Resource parameter. Users can access the file from an IP address in the range 192.0.2.0/24 until January 1, 2013 10:00 am UTC:

{ "Statement": [ { "Resource": "https://d111111abcdef8.cloudfront.net/training/*", "Condition": { "IpAddress": { "AWS:SourceIp": "192.0.2.0/24" }, "DateLessThan": { "AWS:EpochTime": 1357034400 } } } ] }

Each signed cookie in which you use this policy includes a base URL that identifies a specific file, for example:

https://d111111abcdef8.cloudfront.net/training/orientation.pdf

Example policy statement: accessing all files associated with a key pair ID from one IP address

The following sample custom policy allows you to set signed cookies for any file associated with any distribution, as indicated by the * wildcard character in the Resource parameter. The user must use the IP address 192.0.2.10/32. (The value 192.0.2.10/32 in CIDR notation refers to a single IP address, 192.0.2.10.) The files are available only from January 1, 2013 10:00 am UTC until January 2, 2013 10:00 am UTC:

{ "Statement": [ { "Resource": "https://*", "Condition": { "IpAddress": { "AWS:SourceIp": "192.0.2.10/32" }, "DateGreaterThan": { "AWS:EpochTime": 1357034400 }, "DateLessThan": { "AWS:EpochTime": 1357120800 } } } ] }

Each signed cookie in which you use this policy includes a base URL that identifies a specific file in a specific CloudFront distribution, for example:

https://d111111abcdef8.cloudfront.net/training/orientation.pdf

The signed cookie also includes a key pair ID, which must be associated with a trusted key group in the distribution (d111111abcdef8.cloudfront.net) that you specify in the base URL.

Creating a signature for a signed cookie that uses a custom policy

The signature for a signed cookie that uses a custom policy is a hashed, signed, and base64-encoded version of the policy statement.

For additional information and examples of how to hash, sign, and encode the policy statement, see:

To create a signature for a signed cookie by using a custom policy
  1. Use the SHA-1 hash function and RSA to hash and sign the JSON policy statement that you created in the procedure To create the policy statement for a signed URL that uses a custom policy. Use the version of the policy statement that no longer includes white space but that has not yet been base64-encoded.

    For the private key that is required by the hash function, use a private key whose public key is in an active trusted key group for the distribution.

    Note

    The method that you use to hash and sign the policy statement depends on your programming language and platform. For sample code, see Code examples for creating a signature for a signed URL.

  2. Remove white space (including tabs and newline characters) from the hashed and signed string.

  3. Base64-encode the string using MIME base64 encoding. For more information, see Section 6.8, Base64 Content-Transfer-Encoding in RFC 2045, MIME (Multipurpose Internet Mail Extensions) Part One: Format of Internet Message Bodies.

  4. Replace characters that are invalid in a URL query string with characters that are valid. The following table lists invalid and valid characters.

    Replace these invalid characters With these valid characters

    +

    - (hyphen)

    =

    _ (underscore)

    /

    ~ (tilde)

  5. Include the resulting value in the Set-Cookie header for the CloudFront-Signature= name-value pair, and return to To set a signed cookie using a custom policy to add the Set-Cookie header for CloudFront-Key-Pair-Id.