Question

我的代码基于以下资源：https://docs.aws.amazon.com/general/latest/gr/sigv4-signed-request-examples.html#sig-v4-examples-get-auth-header

我无法直接使用boto3，因为我的代码实际上托管在Google App Engine上。 Boto3无法在GAE / python2.7上运行

我遇到SignatureDoesNotMatch错误。

一些注意事项：

我的目标是将s3预签名url传递给前端客户端以供使用。
我没有将request_parameters添加到request_url，因为它是空的
我没有使用authorization_header，因为我想生成一个预先签名的url，以供前端javascript客户端放置对象。

我的代码在下面列出。在我进行更改之前，先进行# ME条评论

def _generate_presigned_url(s3_bucket, object_name,
                            access_key, secret_key):

    # ************* REQUEST VALUES *************
    method = 'PUT'
    service = 's3'
    host = s3_bucket + '.s3.amazonaws.com'
    region = 'us-west-2'
    endpoint = 'https://' + host + '/' + object_name
    request_parameters = ''

    # Key derivation functions. See:
    # http://docs.aws.amazon.com/general/latest/gr/signature-v4-examples.html#signature-v4-examples-python
    def sign(key, msg):
        return hmac.new(key, msg.encode('utf-8'), hashlib.sha256).digest()

    def getSignatureKey(key, dateStamp, regionName, serviceName):
        kDate = sign(('AWS4' + key).encode('utf-8'), dateStamp)
        kRegion = sign(kDate, regionName)
        kService = sign(kRegion, serviceName)
        kSigning = sign(kService, 'aws4_request')
        return kSigning

    # Create a date for headers and the credential string
    t = datetime.datetime.utcnow()
    amzdate = t.strftime('%Y%m%dT%H%M%SZ')
    datestamp = t.strftime('%Y%m%d')  # Date w/o time, used in credential scope


    # ************* TASK 1: CREATE A CANONICAL REQUEST *************
    # http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html

    # Step 1 is to define the verb (GET, POST, etc.)--already done.

    # Step 2: Create canonical URI--the part of the URI from domain to query
    # string (use '/' if no path)
    canonical_uri = '/' + object_name

    # Step 3: Create the canonical query string. In this example (a GET request),
    # request parameters are in the query string. Query string values must
    # be URL-encoded (space=%20). The parameters must be sorted by name.
    # For this example, the query string is pre-formatted in the request_parameters variable.
    canonical_querystring = request_parameters

    # Step 4: Create the canonical headers and signed headers. Header names
    # must be trimmed and lowercase, and sorted in code point order from
    # low to high. Note that there is a trailing \n.

    # ME: Not modifing the headers
    # canonical_headers = 'host:' + host + '\n' + 'x-amz-date:' + amzdate + '\n'
    canonical_headers = 'host:' + host + '\n'

    # Step 5: Create the list of signed headers. This lists the headers
    # in the canonical_headers list, delimited with ";" and in alpha order.
    # Note: The request can include any headers; canonical_headers and
    # signed_headers lists those that you want to be included in the
    # hash of the request. "Host" and "x-amz-date" are always required.

    # ME: Not modifing the headers
    # signed_headers = 'host;x-amz-date'
    signed_headers = 'host'

    # Step 6: Create payload hash (hash of the request body content). For GET
    # requests, the payload is an empty string ("").
    payload_hash = hashlib.sha256(('').encode('utf-8')).hexdigest()

    # Step 7: Combine elements to create canonical request
    # ME: payload is unknown at this point. The presigned_url will be returned to a javascript client for upload
    # canonical_request = method + '\n' + canonical_uri + '\n' + canonical_querystring + '\n' + canonical_headers + '\n' + signed_headers + '\n' + payload_hash
    canonical_request = method + '\n' + canonical_uri + '\n' + canonical_querystring + '\n' + canonical_headers + '\n' + signed_headers


    # ************* TASK 2: CREATE THE STRING TO SIGN*************
    # Match the algorithm to the hashing algorithm you use, either SHA-1 or
    # SHA-256 (recommended)
    algorithm = 'AWS4-HMAC-SHA256'
    credential_scope = datestamp + '/' + region + '/' + service + '/' + 'aws4_request'
    string_to_sign = algorithm + '\n' + amzdate + '\n' + credential_scope + '\n' + hashlib.sha256(canonical_request.encode('utf-8')).hexdigest()

    # ************* TASK 3: CALCULATE THE SIGNATURE *************
    # Create the signing key using the function defined above.
    signing_key = getSignatureKey(secret_key, datestamp, region, service)

    # Sign the string_to_sign using the signing_key
    signature = hmac.new(signing_key, (string_to_sign).encode('utf-8'), hashlib.sha256).hexdigest()


    # ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************
    # The signing information can be either in a query string value or in
    # a header named Authorization. This code shows how to use a header.
    # Create authorization header and add to request headers
enter code here
    authorization_header = algorithm + ' ' + \
                           'Credential=' + access_key + '/' + credential_scope + \
                            ', ' +  'SignedHeaders=' + signed_headers + \
                           ', ' + 'Signature=' + signature

    # ME: Use a list of tuple so I can apply urlencode later
    authorization =[
        ('X-Amz-Algorithm', algorithm),
        ('X-Amz-Expires', '86400'),
        ('X-Amz-Credential', access_key + '/' + credential_scope),
        ('X-Amz-SignedHeaders', signed_headers),
        ('X-Amz-Date', amzdate),
        ('X-Amz-Signature', signature),
    ]

    authorization_query = urlencode(authorization)

    # The request can include any headers, but MUST include "host", "x-amz-date",
    # and (for this scenario) "Authorization". "host" and "x-amz-date" must
    # be included in the canonical_headers and signed_headers, as noted
    # earlier. Order here is not significant.
    # Python note: The 'host' header is added automatically by the Python 'requests' library.

    # ME: not using headers because I want a presigned url
    # headers = {'x-amz-date': amzdate, 'Authorization': authorization_header}


    # ************* SEND THE REQUEST *************
    request_url = endpoint + '?' + authorization_query

    return request_url

我附上了s3的错误响应的屏幕截图。我混淆了屏幕截图中的一些值。但希望它可能有助于发现问题。

导致SignatureDoesNotMatch的此代码（生成用于将对象放入s3的预签名URL）的代码有什么问题？

0 个答案: