authorization for API gateway - aws-api-gateway

Question

I used this tutorial and created "put" endpoint successfully.
https://sanderknape.com/2017/10/creating-a-serverless-api-using-aws-api-gateway-and-dynamodb/
When I follow this advice, I get authroization required error..
Using your favorite REST client, try to PUT an item into DynamoDB
using your API Gateway URL.
python is my favorite client:
import requests
api_url = "https://0pg2858koj.execute-api.us-east-1.amazonaws.com/tds"
PARAMS = {"name": "test", "favorite_movie":"asdsf"}
r = requests.put(url=api_url, params=PARAMS)
the response is 403
My test from console is successful, but not able to put a record from python.

Answer 1

The first step you can take to resolve the problem is to investigate the information returned by AWS in the 403 response. It will provide a header, x-amzn-ErrorType and error message with information about the concrete error. You can test it with curl in verbose mode (-v) or with your Python code. Please, review the relevant documentation to obtain a detailed enumeration of all the possible error reasons.
In any case, looking at your code, it is very likely that you did not provide the necessary authentication or authorization information to AWS.
The kind of information that you must provide depends on which mechanism you configured to access your REST API in API Gateway.
If, for instance, you configured IAM based authentication, you need to set up your Python code to generate an Authorization header with an AWS Signature derived from your user access key ID and associated secret key. The AWS documentation provides an example of use with Postman.
The AWS documentation also provides several examples of how to use python and requests to perform this kind of authorization.
Consider, for instance, this example for posting information to DynamoDB:
# Copyright 2010-2019 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.
# AWS Version 4 signing example
# DynamoDB API (CreateTable)
# See: http://docs.aws.amazon.com/general/latest/gr/sigv4_signing.html
# This version makes a POST request and passes request parameters
# in the body (payload) of the request. Auth information is passed in
# an Authorization header.
import sys, os, base64, datetime, hashlib, hmac
import requests # pip install requests
# ************* REQUEST VALUES *************
method = 'POST'
service = 'dynamodb'
host = 'dynamodb.us-west-2.amazonaws.com'
region = 'us-west-2'
endpoint = 'https://dynamodb.us-west-2.amazonaws.com/'
# POST requests use a content type header. For DynamoDB,
# the content is JSON.
content_type = 'application/x-amz-json-1.0'
# DynamoDB requires an x-amz-target header that has this format:
# DynamoDB_<API version>.<operationName>
amz_target = 'DynamoDB_20120810.CreateTable'
# Request parameters for CreateTable--passed in a JSON block.
request_parameters = '{'
request_parameters += '"KeySchema": [{"KeyType": "HASH","AttributeName": "Id"}],'
request_parameters += '"TableName": "TestTable","AttributeDefinitions": [{"AttributeName": "Id","AttributeType": "S"}],'
request_parameters += '"ProvisionedThroughput": {"WriteCapacityUnits": 5,"ReadCapacityUnits": 5}'
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, date_stamp, regionName, serviceName):
kDate = sign(('AWS4' + key).encode('utf-8'), date_stamp)
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()
amz_date = t.strftime('%Y%m%dT%H%M%SZ')
date_stamp = 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, request
# parameters are passed in the body of the request and the query string
# is blank.
canonical_querystring = ''
# Step 4: Create the canonical 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 = 'content-type:' + content_type + '\n' + 'host:' + host + '\n' + 'x-amz-date:' + amz_date + '\n' + 'x-amz-target:' + amz_target + '\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 include those that you want to be included in the
# hash of the request. "Host" and "x-amz-date" are always required.
# For DynamoDB, content-type and x-amz-target are also required.
signed_headers = 'content-type;host;x-amz-date;x-amz-target'
# Step 6: Create payload hash. In this example, the payload (body of
# the request) contains the request parameters.
payload_hash = hashlib.sha256(request_parameters.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 = date_stamp + '/' + region + '/' + service + '/' + 'aws4_request'
string_to_sign = algorithm + '\n' + amz_date + '\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, date_stamp, 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 *************
# Put the signature information in a header named Authorization.
authorization_header = algorithm + ' ' + 'Credential=' + access_key + '/' + credential_scope + ', ' + 'SignedHeaders=' + signed_headers + ', ' + 'Signature=' + signature
# For DynamoDB, the request can include any headers, but MUST include "host", "x-amz-date",
# "x-amz-target", "content-type", and "Authorization". Except for the authorization
# header, the headers must be included in the canonical_headers and signed_headers values, as
# noted earlier. Order here is not significant.
# # Python note: The 'host' header is added automatically by the Python 'requests' library.
headers = {'Content-Type':content_type,
'X-Amz-Date':amz_date,
'X-Amz-Target':amz_target,
'Authorization':authorization_header}
# ************* SEND THE REQUEST *************
print('\nBEGIN REQUEST++++++++++++++++++++++++++++++++++++')
print('Request URL = ' + endpoint)
r = requests.post(endpoint, data=request_parameters, headers=headers)
print('\nRESPONSE++++++++++++++++++++++++++++++++++++')
print('Response code: %d\n' % r.status_code)
print(r.text)
I think it could be easily adapted to your needs.
In the console, everything works fine because when you invoke your REST endpoints in API Gateway, you are connected to a user who is already authenticated and authorized to access these REST endpoints.