Check all data on keys when comparing for equality

This eliminates the possibility that a hash collision results in two PKey
objects that == each other.

5 files changed, 29 insertions, 14 deletions

diff --git a/paramiko/agent.py b/paramiko/agent.py
index 622b95e4..c7c8b7cb 100644
--- a/paramiko/agent.py
+++ b/paramiko/agent.py
@@ -407,6 +407,10 @@ class AgentKey(PKey):
     def get_name(self):
         return self.name
 
+    @property
+    def _fields(self):
+        raise NotImplementedError
+
     def sign_ssh_data(self, data):
         msg = Message()
         msg.add_byte(cSSH2_AGENTC_SIGN_REQUEST)
diff --git a/paramiko/dsskey.py b/paramiko/dsskey.py
index 7e74836c..09d6f648 100644
--- a/paramiko/dsskey.py
+++ b/paramiko/dsskey.py
@@ -92,8 +92,9 @@ class DSSKey(PKey):
     def __str__(self):
         return self.asbytes()
 
-    def __hash__(self):
-        return hash((self.get_name(), self.p, self.q, self.g, self.y))
+    @property
+    def _fields(self):
+        return (self.get_name(), self.p, self.q, self.g, self.y)
 
     def get_name(self):
         return "ssh-dss"
diff --git a/paramiko/ecdsakey.py b/paramiko/ecdsakey.py
index 3d3d09be..a59017f5 100644
--- a/paramiko/ecdsakey.py
+++ b/paramiko/ecdsakey.py
@@ -194,14 +194,13 @@ class ECDSAKey(PKey):
     def __str__(self):
         return self.asbytes()
 
-    def __hash__(self):
-        return hash(
-            (
-                self.get_name(),
-                self.verifying_key.public_numbers().x,
-                self.verifying_key.public_numbers().y,
-            )
-        )
+    @property
+    def _fields(self):
+        return (
+	    self.get_name(),
+	    self.verifying_key.public_numbers().x,
+	    self.verifying_key.public_numbers().y,
+	)
 
     def get_name(self):
         return self.ecdsa_curve.key_format_identifier
diff --git a/paramiko/ed25519key.py b/paramiko/ed25519key.py
index b584f521..7b19e352 100644
--- a/paramiko/ed25519key.py
+++ b/paramiko/ed25519key.py
@@ -174,12 +174,13 @@ class Ed25519Key(PKey):
         m.add_string(v.encode())
         return m.asbytes()
 
-    def __hash__(self):
+    @property
+    def _fields(self):
         if self.can_sign():
             v = self._signing_key.verify_key
         else:
             v = self._verifying_key
-        return hash((self.get_name(), v))
+        return (self.get_name(), v)
 
     def get_name(self):
         return "ssh-ed25519"
diff --git a/paramiko/pkey.py b/paramiko/pkey.py
index a54d502d..fed68da8 100644
--- a/paramiko/pkey.py
+++ b/paramiko/pkey.py
@@ -20,6 +20,9 @@
 Common API for all public keys.
 """
 
+from abc import ABC
+from abc import abstractproperty
+from abc import abstractmethod
 import base64
 from binascii import unhexlify
 import os
@@ -59,7 +62,7 @@ def _unpad_openssh(data):
     return data[:-padding_length]
 
 
-class PKey(object):
+class PKey(ABC):
     """
     Base class for public keys.
     """
@@ -140,7 +143,14 @@ class PKey(object):
         return cmp(self.asbytes(), other.asbytes())  # noqa
 
     def __eq__(self, other):
-        return hash(self) == hash(other)
+        return self._fields == other._fields
+
+    def __hash__(self):
+        return hash(self._fields)
+
+    @abstractproperty
+    def _fields(self):
+        pass
 
     def get_name(self):
         """