Pythonでs3バケットを取得する際の問題

Question

アマゾンdocsのpythonサンプルコードを使用して、s3バケットで「GET with Authorization Header」メカニズムを使用しようとしています。私が使用しているソースコードは以下の通りです：

# 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 = 's3' 
host = 's3.amazonaws.com' 
region = 'us-east-1' 
endpoint = 'http://s3.amazonaws.com/sample_object/foo' 
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 

# 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 = '/sample_object/foo' 

# 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 
# and value must be trimmed and lowercase, and sorted in ASCII order. 
# Note that there is a trailing \n. 
# amz_content_sha256 = hashlib.sha256('').hexdigest() 
amz_content_sha256 = 'UNSIGNED-PAYLOAD' 
canonical_headers = 'host:' + host + '\n' + 'x-amz-content-sha256:' + amz_content_sha256 + '\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-content-sha256;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('').hexdigest() 

# Step 7: Combine elements to create create canonical request 
canonical_request = method + '\n' + canonical_uri + '\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).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, 'x-amz-content-sha256':amz_content_sha256} 


# ************* SEND THE REQUEST ************* 
request_url = endpoint 

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 

私は正しくアクセスIDと秘密のアクセスキーを設定しました。私はbotoのpythonライブラリと同じものを使っていましたが、バケットやオブジェクトなどをリストするときにはうまくいくようです。上記の方法を使うと403エラーが返ってきます。あなたの鍵と署名方法を確認してください。私は上記の方法で何が間違っているか分かりません。任意のポインタ。？

Answer 1

正規のヘッダーの末尾に改行があり、canonical_requestに空白の場合でもcanonical_querystring行が必要です。また、GET要求の場合はamz_content_sha256にはUNSIGNED_PAYLOADを使用してください。

実例があります。 403は、アクセスが禁止意味

import sys, os, base64, datetime, hashlib, hmac 
import requests 
method = 'GET' 
service = 's3' 
host = 's3-us-west-2.amazonaws.com' 
region = 'us-west-2' 
endpoint = 'http://s3-us-west-2.amazonaws.com' 
request_parameters = '' 

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 

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() 

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 

canonical_uri = '/bucket/key' 
canonical_querystring = request_parameters 
canonical_headers = 'host:' + host + '\n' + 'x-amz-content-sha256:UNSIGNED-PAYLOAD' + '\n' + 'x-amz-date:' + amzdate + '\n' 
signed_headers = 'host;x-amz-content-sha256;x-amz-date' 
payload_hash = 'UNSIGNED-PAYLOAD' 
canonical_request = method + '\n' + canonical_uri + '\n' + canonical_querystring + '\n' + canonical_headers + '\n' + signed_headers + '\n' + payload_hash 
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).hexdigest() 
signing_key = getSignatureKey(secret_key, datestamp, region, service) 
signature = hmac.new(signing_key, (string_to_sign).encode('utf-8'), hashlib.sha256).hexdigest() 
authorization_header = algorithm + ' ' + 'Credential=' + access_key + '/' + credential_scope + ', ' + 'SignedHeaders=' + signed_headers + ', ' + 'Signature=' + signature 
headers = {'x-amz-date':amzdate, 'x-amz-content-sha256': 'UNSIGNED-PAYLOAD', 'Authorization':authorization_header} 
request_url = endpoint + canonical_uri 

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