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v4-signing-get-authheader.py

v4-signing-get-authheader shows how to make a request using the Amazon DynamoDB query API. The request makes a POST request and passes values to AWS in the body of the request. Authentication information is passed using the Authorization request header.

# Copyright 2010-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved. # # This file is licensed under the Apache License, Version 2.0 (the "License"). # You may not use this file except in compliance with the License. A copy of the # License is located at # # http://aws.amazon.com/apache2.0/ # # This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS # OF ANY KIND, either express or implied. See the License for the specific # language governing permissions and limitations under the License. # # ABOUT THIS PYTHON SAMPLE: This sample is part of the AWS General Reference # Signing AWS API Requests top available at # https://docs.aws.amazon.com/general/latest/gr/sigv4-signed-request-examples.html # # AWS Version 4 signing example # EC2 API (DescribeRegions) # See: http://docs.aws.amazon.com/general/latest/gr/sigv4_signing.html # This version makes a GET request and passes the signature # in the Authorization header. import sys, os, base64, datetime, hashlib, hmac import requests # pip install requests # ************* REQUEST VALUES ************* method = 'GET' service = 'ec2' host = 'ec2.amazonaws.com' region = 'us-east-1' endpoint = 'https://ec2.amazonaws.com' request_parameters = 'Action=DescribeRegions&Version=2013-10-15' # 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 # Read AWS access key from env. variables or configuration file. Best practice is NOT # to embed credentials in code. access_key = os.environ.get('AWS_ACCESS_KEY_ID') secret_key = os.environ.get('AWS_SECRET_ACCESS_KEY') if access_key is None or secret_key is None: print('No access key is available.') sys.exit() # 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 = '/' # 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. canonical_headers = 'host:' + host + '\n' + 'x-amz-date:' + amzdate + '\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. signed_headers = 'host;x-amz-date' # 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 canonical_request = method + '\n' + canonical_uri + '\n' + canonical_querystring + '\n' + canonical_headers + '\n' + signed_headers + '\n' + payload_hash # ************* 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 authorization_header = algorithm + ' ' + 'Credential=' + access_key + '/' + credential_scope + ', ' + 'SignedHeaders=' + signed_headers + ', ' + 'Signature=' + signature # 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. headers = {'x-amz-date':amzdate, 'Authorization':authorization_header} # ************* SEND THE REQUEST ************* request_url = endpoint + '?' + canonical_querystring print('\nBEGIN REQUEST++++++++++++++++++++++++++++++++++++') print('Request URL = ' + request_url) r = requests.get(request_url, headers=headers) print('\nRESPONSE++++++++++++++++++++++++++++++++++++') print('Response code: %d\n' % r.status_code) print(r.text)

Sample Details

Service: AWS Signature Version 4 Signing Process

Last tested: 2018-09-20

Author: AWS

Type: full-example

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