python - 如何使用 Python 在 Lambda 中为 CloudFront 生成 SignedUrl？

Question

我目前的 python 代码有问题，此代码生成一个 Cloud Front 签名 URL 并打印它。我在 VS Code 中有一个虚拟环境，它工作正常，但是当我将其上传到 lambda 时，我收到错误:“errorMessage”:“没有名为 '_cffi_backend”的模块”

我已经尝试过:

pip install -t $PWD cffi

pip install -t $PWD 加密

将它们压缩到 .zip 文件中并将其上传到 lambda 以满足要求，并且我还压缩了虚拟环境中具有工作依赖项的所有包。

如何解决这个问题？我需要将它放在 lambda 中，并且我之前也重新安装了 cffi。

import datetime

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding
from botocore.signers import CloudFrontSigner


def rsa_signer(message):
    with open('key.pem', 'rb') as key_file:
        private_key = serialization.load_pem_private_key(
            key_file.read(),
            password=None,
            backend=default_backend()
        )
        print (message)
    return private_key.sign(message, padding.PKCS1v15(), hashes.SHA1())

def lambda_handler(event, context):

    key_id = 'APKAJSKEXampleKNQ'
    url = 'https://example.com/example.html'
    expire_date = datetime.datetime(2021, 1, 1)

    cloudfront_signer = CloudFrontSigner(key_id, rsa_signer)

    # Create a signed url that will be valid until the specfic expiry date
    # provided using a canned policy.
    signed_url = cloudfront_signer.generate_presigned_url(
        url, date_less_than=expire_date)
    print(signed_url)

{
  "errorMessage": "No module named '_cffi_backend'",
  "errorType": "ModuleNotFoundError",
  "stackTrace": [
    "  File \"/var/task/why.py\", line 31, in lambda_handler\n    url, date_less_than=expire_date)\n",
    "  File \"/var/runtime/botocore/signers.py\", line 344, in generate_presigned_url\n    signature = self.rsa_signer(policy)\n",
    "  File \"/var/task/why.py\", line 15, in rsa_signer\n    backend=default_backend()\n",
    "  File \"/var/task/cryptography/hazmat/backends/__init__.py\", line 15, in default_backend\n    from cryptography.hazmat.backends.openssl.backend import backend\n",
    "  File \"/var/task/cryptography/hazmat/backends/openssl/__init__.py\", line 7, in <module>\n    from cryptography.hazmat.backends.openssl.backend import backend\n",
    "  File \"/var/task/cryptography/hazmat/backends/openssl/backend.py\", line 109, in <module>\n    from cryptography.hazmat.bindings.openssl import binding\n",
    "  File \"/var/task/cryptography/hazmat/bindings/openssl/binding.py\", line 14, in <module>\n    from cryptography.hazmat.bindings._openssl import ffi, lib\n"
  ]
}

Answer 1

我阅读了“boto”Cloud Front Signer 的源代码，发现所有功能都是内置的。无需使用“cryptography.hazmat”。

我将上面的代码改为更简单的代码。

from boto.cloudfront.distribution import Distribution
from boto.cloudfront import CloudFrontConnection
from botocore.signers import CloudFrontSigner
import datetime
import rsa

def rsa_signer(message):
    private_key = open('key.pem', 'r').read()
    return rsa.sign(message, rsa.PrivateKey.load_pkcs1(private_key.encode('utf8')),'SHA-1')

def lambda_handler(event, context):
    url = "https://Example.com/Register.html"                                                                                                                                                                      
    expire_date = datetime.datetime(2021, 1, 1)
    key_id = 'APKAJSEXAMPLENXQ'
    cf_signer = CloudFrontSigner(key_id, rsa_signer)
    signed_url = cf_signer.generate_presigned_url(url, date_less_than=expire_date)
    print(signed_url)

对于任何想知道如何使用 python 正确生成 Cloud Front PresignedUrl 的人。上传到 lambda 时，请确保将“boto”和“rsa”打包到您的 zip 文件中。