aws-cloudfront-signed-cookies: Generate signed cookies for AWS CloudFront

One way to serve private content through AWS CloudFront is to use signed cookies. This package helps you generate signed cookies using a custom IAM policy which may include a range of time for which the cookie is valid and an IP address restriction.

The library

Creating signed cookies

Example usage:

{-# LANGUAGE OverloadedStrings, ScopedTypeVariables #-}
import Network.AWS.CloudFront.SignedCookies
import qualified Data.Text.IO
main :: IO ()
main = do
  -- Construct an IAM policy that expires three days from now
  policy :: Policy <- simplePolicy
    (Resource "https://example.com/secrets/*")
    (Lifespan (3 * nominalDay))
  -- Parse the .pem file to get the private key
  key :: PrivateKey <- readPrivateKeyPemFile
    (PemFilePath "./pk-APKAIATXN3RCIOVT5WRQ.pem")
  -- Construct signed cookies
  cookies :: CookiesText <- createSignedCookies
    (KeyPairId "APKAIATXN3RCIOVT5WRQ") key policy
  Data.Text.IO.putStrLn (renderCookiesText cookies)

The output should look something like this:

Cookie: CloudFront-Policy=eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9zZWNyZXRzLyoiLCJDb25kaXRpb24iOnsiRGF0ZUxlc3NUaGFuIjp7IkFXUzpFcG9jaFRpbWUiOjE1MjM2NjQxMjV9fX1dfQ__
Cookie: CloudFront-Signature=R17isgiJD36sb4kh4pNxqq5eFCx5Q~vC~QbQKMhi9BqyhLboLQfb3pCdPp-WSVYOn4wlOobqhgcwoX2vjCd3y8eiUtelX1~ddaDlPBkkdZA~5Imd2z-W1o3r0coKB1SE2SPFT7M1XgNvwOPanQoft1VLchfVPGaitFYMum4KS~GXffqQZzaVybKJ64KfFLLBPSobg8MmBhHvpO9DBiwKijmGhDip~6L3W7OcqGT8HdqAmWxjnTHInXpx7bbVotla6a~J6WB6xmtJrmQzMLdTUxAY6IbJ2PzMtTXKgdNzbByGHvImg9k3Q3fNBTim8l7Tds1zpwX9GsuPcFkPe9HZ1Q__
Cookie: CloudFront-Key-Pair-Id=APKAIATXN3RCIOVT5WRQ

You can see a very similar example in action in the Network.AWS.CloudFront.SignedCookies.CLI.Sign module which defines the command-line interface for creating signed cookies.

Decoding policy cookies

After you generate a policy cookie and send it to a client, you may later want to parse it back into a Policy value -- for example, to determine whether you need to send a new set of cookies to replace an expired policy.

Example in GHCi:

λ> cookiePolicy (PolicyCookie "eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9zZWNyZXRzLyoiLCJDb25kaXRpb24iOnsiRGF0ZUxlc3NUaGFuIjp7IkFXUzpFcG9jaFRpbWUiOjE1MjM2NjQxMjV9fX1dfQ__")
Right (Policy {policyResource = Resource "https://example.com/secrets/*", policyStart = StartImmediately, policyEnd = EndTime 1523664125s, policyIpAddress = AnyIp})

The executable

You can also generate cookies using the command-line interface. It provides two commands:

• sign - Given a private key and policy options, produces signed cookies and prints them as HTTP request headers.
• decode - Decodes a CloudFront-Policy cookie and prints it in human-readable JSON format.

sign

$ aws-cloudfront-signed-cookies sign --help
Generate signed cookies for AWS CloudFront
Usage: aws-cloudfront-signed-cookies sign --pem-file ARG --key-pair-id ARG
                                          --resource ARG --days ARG
Available options:
  --pem-file ARG           Location in the filesystem where a .pem file
                           containing an RSA secret key can be found
  --key-pair-id ARG        CloudFront key pair ID for the key pair that you are
                           using to generate signature
  --resource ARG           URL that the policy will grant access to, optionally
                           containing asterisks for wildcards
  --days ARG               Integer number of days until the policy expires
  -h,--help                Show this help text

Example usage:

$ aws-cloudfront-signed-cookies sign           \
    --pem-file pk-APKAIATXN3RCIOVT5WRQ.pem     \
    --key-pair-id APKAIATXN3RCIOVT5WRQ         \
    --resource "https://example.com/secrets/*" \
    --days 2

Output:

Cookie: CloudFront-Policy=eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9zZWNyZXRzLyoiLCJDb25kaXRpb24iOnsiRGF0ZUxlc3NUaGFuIjp7IkFXUzpFcG9jaFRpbWUiOjE1MjM2NjQxMjV9fX1dfQ__
Cookie: CloudFront-Signature=R17isgiJD36sb4kh4pNxqq5eFCx5Q~vC~QbQKMhi9BqyhLboLQfb3pCdPp-WSVYOn4wlOobqhgcwoX2vjCd3y8eiUtelX1~ddaDlPBkkdZA~5Imd2z-W1o3r0coKB1SE2SPFT7M1XgNvwOPanQoft1VLchfVPGaitFYMum4KS~GXffqQZzaVybKJ64KfFLLBPSobg8MmBhHvpO9DBiwKijmGhDip~6L3W7OcqGT8HdqAmWxjnTHInXpx7bbVotla6a~J6WB6xmtJrmQzMLdTUxAY6IbJ2PzMtTXKgdNzbByGHvImg9k3Q3fNBTim8l7Tds1zpwX9GsuPcFkPe9HZ1Q__
Cookie: CloudFront-Key-Pair-Id=APKAIATXN3RCIOVT5WRQ

decode

$ aws-cloudfront-signed-cookies decode --help
Decode signed AWS CloudFront policy cookies
Usage: aws-cloudfront-signed-cookies decode --policy-cookie ARG
Available options:
  --policy-cookie ARG      The value of a CloudFront-Policy cookie
  -h,--help                Show this help text

Example usage:

$ aws-cloudfront-signed-cookies decode --policy-cookie eyJTdGF0ZW1lbnQiOlt7IlJlc291cmNlIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9zZWNyZXRzLyoiLCJDb25kaXRpb24iOnsiRGF0ZUxlc3NUaGFuIjp7IkFXUzpFcG9jaFRpbWUiOjE1MjM2NjQxMjV9fX1dfQ__
{
    "Statement": [
        {
            "Resource": "https://example.com/secrets/*",
            "Condition": {
                "DateLessThan": {
                    "AWS:EpochTime": 1523664125
                }
            }
        }
    ]
}