Implemented alternate (SHA-1, SHA-256, SHA-256) digest algorithms/content and use proper token values.

requests_http_signature/__init__.py

@@ -45,7 +45,6 @@ class Crypto:
                 key.verify(signature, string_to_sign, self.PKCS1v15(), hasher)
 
 class HTTPSignatureAuth(requests.auth.AuthBase):
-    hasher_constructor = hashlib.sha256
     known_algorithms = {
         "rsa-sha1",
         "rsa-sha256",
@@ -53,23 +52,34 @@ class HTTPSignatureAuth(requests.auth.AuthBase):
         "hmac-sha256",
         "ecdsa-sha256",
     }
+    
+    known_digests = {
+        "sha256": "sha-256", 
+        "sha512": "sha-512",
+        "sha1": "sha"
+    }
 
-    def __init__(self, key, key_id, algorithm="hmac-sha256", headers=None, passphrase=None, expires_in=None):
+    def __init__(self, key, key_id, algorithm="hmac-sha256", headers=None, passphrase=None, expires_in=None, digest="sha256"):
         """
         :param typing.Union[bytes, string] passphrase: The passphrase for an encrypted RSA private key
         :param datetime.timedelta expires_in: The time after which this signature should expire
         """
         assert algorithm in self.known_algorithms
+        assert digest in self.known_digests
         self.key = key
         self.key_id = key_id
         self.algorithm = algorithm
         self.headers = [h.lower() for h in headers] if headers is not None else ["date"]
         self.passphrase = passphrase if passphrase is None or isinstance(passphrase, bytes) else passphrase.encode()
         self.expires_in = expires_in
+        self.digest_alg = digest
 
     def add_date(self, request, timestamp):
         if "Date" not in request.headers:
             request.headers["Date"] = email.utils.formatdate(timestamp, usegmt=True)
+            
+    def digest_content(self, request):
+        return request.body
 
     def add_digest(self, request):
         if request.body is None and "digest" in self.headers:
@@ -77,8 +87,9 @@ class HTTPSignatureAuth(requests.auth.AuthBase):
         if request.body is not None and "Digest" not in request.headers:
             if "digest" not in self.headers:
                 self.headers.append("digest")
-            digest = self.hasher_constructor(request.body).digest()
-            request.headers["Digest"] = "SHA-256=" + base64.b64encode(digest).decode()
+            hash = hashlib.new(self.digest_alg)
+            hash.update(self.digest_content(request))
+            request.headers["Digest"] = self.known_digests[self.digest_alg] + "=" + base64.b64encode(hash.digest()).decode()
 
     @classmethod
     def get_string_to_sign(self, request, headers, created_timestamp, expires_timestamp):