[Python] Support for HTTP signature (#4958)

* start implementation of HTTP signature

* add api key parameters for http message signature

* HTTP signature authentication

* start implementation of HTTP signature

* add api key parameters for http message signature

* HTTP signature authentication

* HTTP signature authentication

* start implementation of HTTP signature

* fix merge issues

* Address formatting issues

* Address formatting issues

* move python-experimental-openapiv3-sample to a separate PR

* Add support for HTTP signature

* Add code comments

* Add code comments

* Fix formatting issues

* Fix formatting issues

* Fix formatting issues

* add code comments

* add code comments

* fix python formatting issues

* Make PKCS1v15 string constant consistent between Python and Golang

* fix python formatting issues

* Add code comments in generated Python. Start adding unit tests for HTTP signature

* compliance with HTTP signature draft 12

* compliance with HTTP signature draft 12

* working on review comments

* working on review comments

* working on review comments

* working on review comments

* working on review comments

* working on review comments

* working on review comments

* working on review comments

* working on review comments

* fix python formatting issues

* fix trailing white space

* address PR comments

* address PR comments

* address PR comments

* Add suppport for '(expires)' signature parameter

* address PR comments

* address PR comments

* Fix python formatting issues

* Fix python formatting issues

* Starting to move code to dedicated file for HTTP signatures

* Continue to refactor code to dedicated file for HTTP signatures

* Continue to refactor code to dedicated file for HTTP signatures

* Continue to refactor code to dedicated file for HTTP signatures

* Continue to refactor code to dedicated file for HTTP signatures

* move method to ProcessUtils

* conditionally build signing.py

* move method to ProcessUtils

* Code reformatting

* externalize http signature configuration

* address PR review comments

* address PR review comments

* run samples scripts

* Address PR review comments

* Move 'private_key' field to signing module

* Move 'private_key' field to signing module

* code cleanup

* remove use of strftime('%s'), which is non portable

* code cleanup

* code cleanup

* code cleanup

* run sample scripts

* Address PR review comments.

* Add http-signature security scheme

* Run sample scripts for go

* Fix issue uncovered in integration branch

* Fix issue uncovered in integration branch

* Fix issue uncovered in integration branch

* Fix issue uncovered in integration branch

* Run samples scripts

* move http signature tests to separate file

* move http signature tests to separate file

* unit tests for HTTP signature

* continue implementation of unit tests

* add http_signature_test to security scheme

* add unit tests for http signature

* address review comments

* remove http signature from petapi

* Add separate OAS file with support for HTTP signature

* Add support for private key passphrase. Add more unit tests

* Add unit test to validate the signature against the public key

* remove http signature from petstore-with-fake-endpoints-models-for-testing.yaml

* fix unit test issues

* run scripts in bin directory

* Refact unit test with better variable names

* do not throw exception if security scheme is unrecognized

* change URL of apache license to use https

* sync from master

* fix usage of escape character in python regex. Fix generated python documentation

* write HTTP signed headers in user-specified order. Fix PEP8 formatting issues

* write HTTP signed headers in user-specified order. Fix PEP8 formatting issues

* http signature unit tests

* Fix PEP8 format issue

* spread out each requirement to a separate line

* run samples scripts

* run sample scripts

* remove encoding of '+' character

samples/client/petstore/python/petstore_api/configuration.py

@@ -37,6 +37,8 @@ class Configuration(object):
       The dict value is an API key prefix when generating the auth data.
     :param username: Username for HTTP basic authentication
     :param password: Password for HTTP basic authentication
+    :param signing_info: Configuration parameters for HTTP signature.
+        Must be an instance of petstore_api.signing.HttpSigningConfiguration
 
     :Example:
 
@@ -55,11 +57,50 @@ class Configuration(object):
       )
     The following cookie will be added to the HTTP request:
        Cookie: JSESSIONID abc123
+
+    Configure API client with HTTP basic authentication:
+      conf = petstore_api.Configuration(
+          username='the-user',
+          password='the-password',
+      )
+
+    Configure API client with HTTP signature authentication. Use the 'hs2019' signature scheme,
+    sign the HTTP requests with the RSA-SSA-PSS signature algorithm, and set the expiration time
+    of the signature to 5 minutes after the signature has been created.
+    Note you can use the constants defined in the petstore_api.signing module, and you can
+    also specify arbitrary HTTP headers to be included in the HTTP signature, except for the
+    'Authorization' header, which is used to carry the signature.
+
+    One may be tempted to sign all headers by default, but in practice it rarely works.
+    This is beccause explicit proxies, transparent proxies, TLS termination endpoints or
+    load balancers may add/modify/remove headers. Include the HTTP headers that you know
+    are not going to be modified in transit.
+
+      conf = petstore_api.Configuration(
+        signing_info = petstore_api.signing.HttpSigningConfiguration(
+            key_id =                 'my-key-id',
+            private_key_path =       'rsa.pem',
+            signing_scheme =         signing.SCHEME_HS2019,
+            signing_algorithm =      signing.ALGORITHM_RSASSA_PSS,
+            signed_headers =         [signing.HEADER_REQUEST_TARGET,
+                                      signing.HEADER_CREATED,
+                                      signing.HEADER_EXPIRES,
+                                      signing.HEADER_HOST,
+                                      signing.HEADER_DATE,
+                                      signing.HEADER_DIGEST,
+                                      'Content-Type',
+                                      'Content-Length',
+                                      'User-Agent'
+                                     ],
+            signature_max_validity = datetime.timedelta(minutes=5)
+        )
+      )
     """
 
     def __init__(self, host="http://petstore.swagger.io:80/v2",
                  api_key=None, api_key_prefix=None,
-                 username=None, password=None):
+                 username=None, password=None,
+                 signing_info=None):
         """Constructor
         """
         self.host = host
@@ -88,6 +129,11 @@ class Configuration(object):
         self.password = password
         """Password for HTTP basic authentication
         """
+        if signing_info is not None:
+            signing_info.host = host
+        self.signing_info = signing_info
+        """The HTTP signing configuration
+        """
         self.access_token = ""
         """access token for OAuth/Bearer
         """