python - 为 Amazon CloudFront 创建签名 Cookie

Question

亚马逊推出了Cloudfront signed cookie最近除了签名的网址。

一个类似的问题是关于 signed url .显然支持 signed url in the cloudfront SDK

但是我在 aws python SDK 中找不到此功能的支持。

我怎样才能创建一个签名的 cookie？

Answer 1

我创建了一个 boto 功能请求来添加它，但与此同时我让它与我的 django python 应用程序一起工作。这是我自己生成的简单代码。底部是一个示例 django View 方法，因此您可以看到我如何为包含 Cloudfront 内容的网页设置 cookie。

import time
from boto.cloudfront import CloudFrontConnection
from boto.cloudfront.distribution import Distribution
from config import settings
import logging
from django.template.context import RequestContext
from django.shortcuts import render_to_response
logger = logging.getLogger('boto')
logger.setLevel(logging.CRITICAL) #disable DEBUG logging that's enabled in AWS by default (outside of django)

AWS_ACCESS_KEY="AKABCDE1235ABCDEF22A"#SAMPLE
AWS_SECRET_KEY="a1wd2sD1A/GS8qggkXK1u8kHlh+BiLp0C3nBJ2wW" #SAMPLE
key_pair_id="APKABCDEF123ABCDEFAG" #SAMPLE
DOWNLOAD_DIST_ID = "E1ABCDEF3ABCDE" #SAMPLE replace with the ID of your Cloudfront dist from Cloudfront console

############################################
def generate_signed_cookies(resource,expire_minutes=5):
    """
    @resource   path to s3 object inside bucket(or a wildcard path,e.g. '/blah/*' or  '*')
    @expire_minutes     how many minutes before we expire these access credentials (within cookie)
    return tuple of domain used in resource URL & dict of name=>value cookies
    """
    if not resource:
        resource = 'images/*'
    dist_id = DOWNLOAD_DIST_ID
    conn = CloudFrontConnection(AWS_ACCESS_KEY, AWS_SECRET_KEY)
    dist = SignedCookiedCloudfrontDistribution(conn,dist_id)
    return dist.create_signed_cookies(resource,expire_minutes=expire_minutes)

############################################
class SignedCookiedCloudfrontDistribution():

    def __init__(self,connection,download_dist_id,cname=True):
        """
        @download_dist_id   id of your Cloudfront download distribution
        @cname          boolean True to use first domain cname, False to use 
                        cloudfront domain name, defaults to cname
                        which presumably matches your writeable cookies ( .mydomain.com)
        """
        self.download_dist = None
        self.domain = None
        try:
            download_dist = connection.get_distribution_info(download_dist_id)
            if cname and download_dist.config.cnames:
                self.domain = download_dist.config.cnames[0] #use first cname if defined
            else:
                self.domain = download_dist.domain_name
            self.download_dist = download_dist
        except Exception, ex:
            logging.error(ex)

    def get_http_resource_url(self,resource=None,secure=False):
        """
        @resource   optional path and/or filename to the resource 
                   (e.g. /mydir/somefile.txt);
                    defaults to wildcard if unset '*'
        @secure     whether to use https or http protocol for Cloudfront URL - update  
                    to match your distribution settings 
        return constructed URL
        """
        if not resource:
            resource = '*'
        protocol = "http" if not secure else "https"
        http_resource = '%s://%s/%s' % (protocol,self.domain,resource)
        return http_resource

    def create_signed_cookies(self,resource,expire_minutes=3):
        """
        generate the Cloudfront download distirbution signed cookies
        @resource   path to the file, path, or wildcard pattern to generate policy for
        @expire_minutes  number of minutes until expiration
        return      tuple with domain used within policy (so it matches 
                    cookie domain), and dict of cloudfront cookies you
                    should set in request header
        """
        http_resource = self.get_http_resource_url(resource,secure=False)    #per-file access #NOTE secure should match security settings of cloudfront distribution
    #    http_resource = self.get_http_resource_url("somedir/*")  #blanket access to all /somedir files inside my bucket
    #    http_resource = self.get_http_resource_url("*")          #blanket access to all files inside my bucket

        #generate no-whitespace json policy, then base64 encode & make url safe
        policy = Distribution._canned_policy(http_resource,SignedCookiedCloudfrontDistribution.get_expires(expire_minutes))
        encoded_policy = Distribution._url_base64_encode(policy)

        #assemble the 3 Cloudfront cookies
        signature = SignedCookiedCloudfrontDistribution.generate_signature(policy,private_key_file=settings.AMAZON_PRIV_KEY_FILE)
        cookies = {
            "CloudFront-Policy" :encoded_policy,
            "CloudFront-Signature" :signature,
            "CloudFront-Key-Pair-Id" :key_pair_id #e.g, APKA..... -> same value you use when you sign URLs with boto distribution.create_signed_url() function
        }
        return self.domain,cookies

    @staticmethod
    def get_expires(minutes):
        unixTime = time.time() + (minutes * 60)
        expires = int(unixTime)  #if not converted to int causes Malformed Policy error and has 2 decimals in value
        return expires

    @staticmethod
    def generate_signature(policy,private_key_file=None):
        """
        @policy     no-whitespace json str (NOT encoded yet)
        @private_key_file   your .pem file with which to sign the policy
        return encoded signature for use in cookie
        """
        #sign the policy - code borrowed from Distribution._create_signing_params()
        signature = Distribution._sign_string(policy, private_key_file)
        #now base64 encode the signature & make URL safe
        encoded_signature = Distribution._url_base64_encode(signature)
        return encoded_signature

############################################
def sample_django_view_method(request,template="mytemplate.html"):
    expireLen = 30 #30 minutes
    s3resource = "somepath_in_my_bucket/afile.mp4"
    context = {} #variables I'm passing to my html template
    response = render_to_response(template, context, context_instance=RequestContext(request))
    domain,cookies = generate_signed_cookies(s3resource,expire_minutes=expireLen)
    #TROUBLESHOOTING COOKIES:
    #NOTE - Cookie Domain must be a domain you control that spans your app & your Cloudfront CNAME
    #NOTE - (e.g. if my webapp is www.mydomain.com and my AWS Download Distribution has cname cloud.mydomain.com, cant set cookies from webapp to 
            # www.mydomain.com or localhost.mydomain.com or cloud.mydomain.com and have them work 
        # -> instead set cookies to .mydomain.com to work across sub-domains, you can then verify in request headers to CloudFront that these cookies get passed.
        # TIP - if you set_cookies from a page with a .mydomain.com suffix, but don't see them get set in Chrome they didn't get set because of permissions - can't set to a diff subdomain or diff base domain
        # TIP - if you set_cookies and see them in Chrome but don't see them in request headers to Cloudfront, cookie domain is likely too narrow, need to widen to span subdomains
    base_domain = '.mydomain.com'
    # NOTE: Sanity check when testing so you can flag any gotchas - I have not fully tested using non-cname urls inside policy vs all possible domains for cookie itself   
    if not domain.endswith(base_domain):
        logger.warn("This likely won't work - your resource permissions use a different domain than your cookies")
    for name,value in cookies.items():
        response.set_cookie(name,value=value,httponly=True,domain=base_domain)
    return response

############################################

if __name__ == '__main__':
    domain,cookies = generate_signed_cookies('images/*',expire_minutes=30)

关于我的设置的注意事项:

• 我只需要对我的下载分配进行一项更改，该分配已经设置好并适用于签名 URL:我必须添加一个 cname，其基域与我的网站匹配。

• 我使用了 Chrome 网络开发者工具:

  • 网络:查看云端调用中发送的请求 header 并查看 403 与 200/状态/响应大小
  • 控制台:看到 403 错误，直到一切正常
  • 资源 > Cookies - 验证 [localhost or your host].mydomain.com cookies 显示填充的 3 个 Cloudfront cookies，它们设置为 Domain=.mydomain.com 并且这些值与请求 header 中的值匹配Cloudfront(如果缺少，可能是域配置错误)

我的 AWS 配置

• S3 需要 Cloudfront 来源
• Cloudfront 下载分发:
  • 分发设置:
    • cname 定义:cloud.mydomain.com(对我来说是新的!)
    • 默认 Cloudfront 证书
  • Origins 选项卡:定义了 1 个映射到我的 S3 存储桶的 origin
  • “行为”选项卡 - 默认值:
    • 所有这些都与我已经用于签名 URL 的设置没有变化
    • HTTP 和 HTTPS
    • 得到，头
    • 转发标题:无
    • 使用原始缓存 header
    • 最小 TTL:0
    • 转发 Cookie:无
    • 转发查询字符串:否
    • 流畅的流式传输:否
    • 限制查看者访问:是(自签名网址以来没有变化)
    • 可信签名者:自己

有了上面的 cookie 生成代码后，最棘手的部分是:

• 确保 cookie 域是正确的
• 确保您策略中的路径/资源与您的应用发出的请求相匹配