Question

我正在尝试为私有内容分发设置CloudFront，但是当我按照生成的URL时，我不断收到“拒绝访问”错误。为了清楚起见，我已经创建了CloudFront发行版，将其标记为私有，创建了一个Origin Access ID，该ID已被授予对所有相关文件的读取权限。

我编写了一个简单的Python脚本，使用亚马逊网页上提供的示例生成URL，用于签名URL，包括以下文本：

import os, time

def GetCloudFrontURL(file, expires=86400):
  resource = "http://mydistribution.cloudfront.net/" + file
  exptime = int(time.time()) + expires
  epochtime = str(exptime)
  policy = '{"Statement":[{"Resource":"' + resource + '","Condition":{"DateLessThan":{"AWS:EpochTime":' + epochtime + '}}}]}'
  pk = "MY-PK-GOES-HERE"
  signature = os.popen("echo '" + policy + "' | openssl sha1 -sign /path/to/file/pk-" + pk + ".pem | openssl base64 | tr '+=/' '-_~'").read()
  signature = signature.replace('\n','')
  url = resource + "&Expires=" + epochtime + "&Signature=" + signature + "&Key-Pair-Id=" + pk
  return url

任何人都可以看到我正在做的事情明显错误吗？我已经验证了当我使用私钥对摘要进行签名时，我可以使用公钥对其进行验证（前提是我在通过base64和转换步骤进行验证之前进行了验证）。

感谢。

Answer 1

运行你的方法我在第一个关键字Expires之前得到一个＆符号。

>>> GetCloudFrontURL('test123')
http://mydistribution.cloudfront.net/test123&Expires=1297954193&Signature=&Key-Pair-Id=MY-PK-GOES-HERE

不知道它是否解决了您的整个问题，但我怀疑您需要在URL中使用问号以使params正确解析。尝试这样的事情：

url = resource + "?Expires=" + epochtime + "&Signature=" + signature + "&Key-Pair-Id=" + pk

除此之外，urllib.urlencode方法会将params字典转换为您的URL。 http://docs.python.org/library/urllib.html#urllib.urlencode

Answer 2

基于此，我能够通过一些调整来实现它。

另外，请参阅boto的set_all_permissions函数，该函数将自动为您设置S3 ACL。

from OpenSSL.crypto import *
import base64
import time
from django.conf import settings

ALT_CHARS = '-~' 

def get_cloudfront_url(file, expires=86400):
    resource = "https://" + settings.AWS_CLOUDFRONT_URL + "/" + file
    exptime = int(time.time()) + expires

    epochtime = str(exptime)
    policy = '{"Statement":[{"Resource":"' + resource + '","Condition":{"DateLessThan":{"AWS:EpochTime":' + epochtime + '}}}]}'

    f = open(settings.AWS_PRIVATE_KEY, 'r')
    private_key = load_privatekey(FILETYPE_PEM, f.read())
    f.close()

    signature = base64.b64encode(sign(private_key, policy, 'sha1'), ALT_CHARS)
    signature = signature.replace('=', '_')

    url = resource + "?Expires=" + epochtime + "&Signature=" + signature + "&Key-Pair-Id=" + settings.AWS_CLOUDFRONT_KEY_PAIR_ID
    return url

Answer 3

以下是如何生成签名URL而无需os.popen到openssl。这使用了优秀的M2Crypto python库

此代码基于Amazon在CloudFront文档中提供的PHP示例代码。

from M2Crypto import EVP
import base64
import time

def aws_url_base64_encode(msg):
    msg_base64 = base64.b64encode(msg)
    msg_base64 = msg_base64.replace('+', '-')
    msg_base64 = msg_base64.replace('=', '_')
    msg_base64 = msg_base64.replace('/', '~')
    return msg_base64

def sign_string(message, priv_key_string):
    key = EVP.load_key_string(priv_key_string)
    key.reset_context(md='sha1')
    key.sign_init()
    key.sign_update(message)
    signature = key.sign_final()
    return signature

def create_url(url, encoded_signature, key_pair_id, expires):
    signed_url = "%(url)s?Expires=%(expires)s&Signature=%(encoded_signature)s&Key-Pair-Id=%(key_pair_id)s" % {
            'url':url,
            'expires':expires,
            'encoded_signature':encoded_signature,
            'key_pair_id':key_pair_id,
            }
    return signed_url

def get_canned_policy_url(url, priv_key_string, key_pair_id, expires):
    #we manually construct this policy string to ensure formatting matches signature
    canned_policy = '{"Statement":[{"Resource":"%(url)s","Condition":{"DateLessThan":{"AWS:EpochTime":%(expires)s}}}]}' % {'url':url, 'expires':expires}

    #now base64 encode it (must be URL safe)
    encoded_policy = aws_url_base64_encode(canned_policy)
    #sign the non-encoded policy
    signature = sign_string(canned_policy, priv_key_string)
    #now base64 encode the signature (URL safe as well)
    encoded_signature = aws_url_base64_encode(signature)

    #combine these into a full url
    signed_url = create_url(url, encoded_signature, key_pair_id, expires);

    return signed_url

def encode_query_param(resource):
    enc = resource
    enc = enc.replace('?', '%3F')
    enc = enc.replace('=', '%3D')
    enc = enc.replace('&', '%26')
    return enc


#Set parameters for URL
key_pair_id = "APKAIAZVIO4BQ" #from the AWS accounts CloudFront tab
priv_key_file = "cloudfront-pk.pem" #your private keypair file
# Use the FULL URL for non-streaming:
resource = "http://34254534.cloudfront.net/video.mp4"
#resource = 'video.mp4' #your resource (just object name for streaming videos)
expires = int(time.time()) + 300 #5 min

#Create the signed URL
priv_key_string = open(priv_key_file).read()
signed_url = get_canned_policy_url(resource, priv_key_string, key_pair_id, expires)

print(signed_url)

#Flash player doesn't like query params so encode them if you're using a streaming distribution
#enc_url = encode_query_param(signed_url)
#print(enc_url)

确保使用设置为持有密钥对的帐户的TrustedSigners参数设置您的分配（如果是您自己的帐户，则设置为“自我”）

请参阅Getting started with secure AWS CloudFront streaming with Python以获取有关使用Python进行流式传输的完整工作示例

使用Amazon CloudFront专用分发拒绝访问

3 个答案: