Factor 'generate_signed_url' into a free function in 'gcloud.credenti…

…als'.

Leave a wrapper method in 'gcloud.storage.connection.Connection'.

Fixes #57.

gcloud/credentials.py

@@ -1,6 +1,24 @@
 """A simple wrapper around the OAuth2 credentials library."""
 
+import base64
+import calendar
+import datetime
+import urllib
+
+from Crypto.Hash import SHA256
+from Crypto.PublicKey import RSA
+from Crypto.Signature import PKCS1_v1_5
 from oauth2client import client
+from OpenSSL import crypto
+import pytz
+
+
+def _utcnow():  # pragma: NO COVER testing replaces
+    """Returns current time as UTC datetime.
+
+    NOTE: on the module namespace so tests can replace it.
+    """
+    return datetime.datetime.utcnow()
 
 
 def get_for_service_account(client_email, private_key_path, scope=None):
@@ -36,3 +54,105 @@ def get_for_service_account(client_email, private_key_path, scope=None):
         service_account_name=client_email,
         private_key=open(private_key_path).read(),
         scope=scope)
+
+
+def generate_signed_url(credentials, endpoint, resource, expiration,
+                        method='GET', content_md5=None, content_type=None):
+    """Generate signed URL to provide query-string auth'n to a resource.
+
+    :type credentials:
+        :class:`oauth2client.client.SignedJwtAssertionCredentials`
+    :param credentials: the credentials used to sign the URL.
+
+    :type endpoint: string
+    :param endpoint: Base API endpoint URL.
+
+    :type resource: string
+    :param resource: A pointer to a specific resource within the endpoint
+                     (e.g., ``/bucket-name/file.txt``).
+
+    :type expiration: int, long, datetime.datetime, datetime.timedelta
+    :param expiration: When the signed URL should expire.
+
+    :type method: string
+    :param method: The HTTP verb that will be used when requesting the URL.
+
+    :type content_md5: string
+    :param content_md5: The MD5 hash of the object referenced by
+                        ``resource``.
+
+    :type content_type: string
+    :param content_type: The content type of the object referenced by
+                            ``resource``.
+
+    :rtype: string
+    :returns: A signed URL you can use to access the resource
+                until expiration.
+    """
+    expiration = _get_expiration_seconds(expiration)
+
+    # Generate the string to sign.
+    signature_string = '\n'.join([
+        method,
+        content_md5 or '',
+        content_type or '',
+        str(expiration),
+        resource])
+
+    # Take our PKCS12 (.p12) key and make it into a RSA key we can use...
+    pkcs12 = crypto.load_pkcs12(
+        base64.b64decode(credentials.private_key),
+        'notasecret')
+    pem = crypto.dump_privatekey(
+        crypto.FILETYPE_PEM, pkcs12.get_privatekey())
+    pem_key = RSA.importKey(pem)
+
+    # Sign the string with the RSA key.
+    signer = PKCS1_v1_5.new(pem_key)
+    signature_hash = SHA256.new(signature_string)
+    signature_bytes = signer.sign(signature_hash)
+    signature = base64.b64encode(signature_bytes)
+
+    # Set the right query parameters.
+    query_params = {
+        'GoogleAccessId': credentials.service_account_name,
+        'Expires': str(expiration),
+        'Signature': signature,
+    }
+
+    # Return the built URL.
+    return '{endpoint}{resource}?{querystring}'.format(
+        endpoint=endpoint, resource=resource,
+        querystring=urllib.urlencode(query_params))
+
+
+def _get_expiration_seconds(expiration):
+    """Convert 'expiration' to a number of seconds in the future.
+
+    :type expiration: int, long, datetime.datetime, datetime.timedelta
+    :param expiration: When the signed URL should expire.
+
+    :rtype: int
+    :returns: a timestamp as an absolute number of seconds.
+    """
+    # If it's a timedelta, add it to `now` in UTC.
+    if isinstance(expiration, datetime.timedelta):
+        now = _utcnow().replace(tzinfo=pytz.utc)
+        expiration = now + expiration
+
+    # If it's a datetime, convert to a timestamp.
+    if isinstance(expiration, datetime.datetime):
+        # Make sure the timezone on the value is UTC
+        # (either by converting or replacing the value).
+        if expiration.tzinfo:
+            expiration = expiration.astimezone(pytz.utc)
+        else:
+            expiration = expiration.replace(tzinfo=pytz.utc)
+
+        # Turn the datetime into a timestamp (seconds, not microseconds).
+        expiration = int(calendar.timegm(expiration.timetuple()))
+
+    if not isinstance(expiration, (int, long)):
+        raise TypeError('Expected an integer timestamp, datetime, or '
+                        'timedelta. Got %s' % type(expiration))
+    return expiration

gcloud/storage/connection.py

@@ -1,31 +1,16 @@
 """Create / interact with gcloud storage connections."""
 
-import base64
-import calendar
-import datetime
 import json
 import urllib
 
-from Crypto.Hash import SHA256
-from Crypto.PublicKey import RSA
-from Crypto.Signature import PKCS1_v1_5
-from OpenSSL import crypto
-import pytz
 
 from gcloud import connection
+from gcloud import credentials
 from gcloud.storage import exceptions
 from gcloud.storage.bucket import Bucket
 from gcloud.storage.bucket import BucketIterator
 
 
-def _utcnow():  # pragma: NO COVER testing replaces
-    """Returns current time as UTC datetime.
-
-    NOTE: on the module namespace so tests can replace it.
-    """
-    return datetime.datetime.utcnow()
-
-
 class Connection(connection.Connection):
     """A connection to Google Cloud Storage via the JSON REST API.
 
@@ -453,70 +438,6 @@ def generate_signed_url(self, resource, expiration,
         :returns: A signed URL you can use to access the resource
                   until expiration.
         """
-        expiration = _get_expiration_seconds(expiration)
-
-        # Generate the string to sign.
-        signature_string = '\n'.join([
-            method,
-            content_md5 or '',
-            content_type or '',
-            str(expiration),
-            resource])
-
-        # Take our PKCS12 (.p12) key and make it into a RSA key we can use...
-        pkcs12 = crypto.load_pkcs12(
-            base64.b64decode(self.credentials.private_key),
-            'notasecret')
-        pem = crypto.dump_privatekey(
-            crypto.FILETYPE_PEM, pkcs12.get_privatekey())
-        pem_key = RSA.importKey(pem)
-
-        # Sign the string with the RSA key.
-        signer = PKCS1_v1_5.new(pem_key)
-        signature_hash = SHA256.new(signature_string)
-        signature_bytes = signer.sign(signature_hash)
-        signature = base64.b64encode(signature_bytes)
-
-        # Set the right query parameters.
-        query_params = {
-            'GoogleAccessId': self.credentials.service_account_name,
-            'Expires': str(expiration),
-            'Signature': signature,
-        }
-
-        # Return the built URL.
-        return '{endpoint}{resource}?{querystring}'.format(
-            endpoint=self.API_ACCESS_ENDPOINT, resource=resource,
-            querystring=urllib.urlencode(query_params))
-
-
-def _get_expiration_seconds(expiration):
-    """Convert 'expiration' to a number of seconds in the future.
-
-    :type expiration: int, long, datetime.datetime, datetime.timedelta
-    :param expiration: When the signed URL should expire.
-
-    :rtype: int
-    :returns: a timestamp as an absolute number of seconds.
-    """
-    # If it's a timedelta, add it to `now` in UTC.
-    if isinstance(expiration, datetime.timedelta):
-        now = _utcnow().replace(tzinfo=pytz.utc)
-        expiration = now + expiration
-
-    # If it's a datetime, convert to a timestamp.
-    if isinstance(expiration, datetime.datetime):
-        # Make sure the timezone on the value is UTC
-        # (either by converting or replacing the value).
-        if expiration.tzinfo:
-            expiration = expiration.astimezone(pytz.utc)
-        else:
-            expiration = expiration.replace(tzinfo=pytz.utc)
-
-        # Turn the datetime into a timestamp (seconds, not microseconds).
-        expiration = int(calendar.timegm(expiration.timetuple()))
-
-    if not isinstance(expiration, (int, long)):
-        raise TypeError('Expected an integer timestamp, datetime, or '
-                        'timedelta. Got %s' % type(expiration))
-    return expiration
+        return credentials.generate_signed_url(
+            self.credentials, self.API_ACCESS_ENDPOINT, resource, expiration,
+            method, content_md5, content_type)