added v3

venv/lib/python3.11/site-packages/paramiko/kex_ecdh_nist.py

@@ -0,0 +1,151 @@
+"""
+Ephemeral Elliptic Curve Diffie-Hellman (ECDH) key exchange
+RFC 5656, Section 4
+"""
+
+from hashlib import sha256, sha384, sha512
+from paramiko.common import byte_chr
+from paramiko.message import Message
+from paramiko.ssh_exception import SSHException
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.hazmat.primitives import serialization
+from binascii import hexlify
+
+_MSG_KEXECDH_INIT, _MSG_KEXECDH_REPLY = range(30, 32)
+c_MSG_KEXECDH_INIT, c_MSG_KEXECDH_REPLY = [byte_chr(c) for c in range(30, 32)]
+
+
+class KexNistp256:
+
+    name = "ecdh-sha2-nistp256"
+    hash_algo = sha256
+    curve = ec.SECP256R1()
+
+    def __init__(self, transport):
+        self.transport = transport
+        # private key, client public and server public keys
+        self.P = 0
+        self.Q_C = None
+        self.Q_S = None
+
+    def start_kex(self):
+        self._generate_key_pair()
+        if self.transport.server_mode:
+            self.transport._expect_packet(_MSG_KEXECDH_INIT)
+            return
+        m = Message()
+        m.add_byte(c_MSG_KEXECDH_INIT)
+        # SEC1: V2.0  2.3.3 Elliptic-Curve-Point-to-Octet-String Conversion
+        m.add_string(
+            self.Q_C.public_bytes(
+                serialization.Encoding.X962,
+                serialization.PublicFormat.UncompressedPoint,
+            )
+        )
+        self.transport._send_message(m)
+        self.transport._expect_packet(_MSG_KEXECDH_REPLY)
+
+    def parse_next(self, ptype, m):
+        if self.transport.server_mode and (ptype == _MSG_KEXECDH_INIT):
+            return self._parse_kexecdh_init(m)
+        elif not self.transport.server_mode and (ptype == _MSG_KEXECDH_REPLY):
+            return self._parse_kexecdh_reply(m)
+        raise SSHException(
+            "KexECDH asked to handle packet type {:d}".format(ptype)
+        )
+
+    def _generate_key_pair(self):
+        self.P = ec.generate_private_key(self.curve, default_backend())
+        if self.transport.server_mode:
+            self.Q_S = self.P.public_key()
+            return
+        self.Q_C = self.P.public_key()
+
+    def _parse_kexecdh_init(self, m):
+        Q_C_bytes = m.get_string()
+        self.Q_C = ec.EllipticCurvePublicKey.from_encoded_point(
+            self.curve, Q_C_bytes
+        )
+        K_S = self.transport.get_server_key().asbytes()
+        K = self.P.exchange(ec.ECDH(), self.Q_C)
+        K = int(hexlify(K), 16)
+        # compute exchange hash
+        hm = Message()
+        hm.add(
+            self.transport.remote_version,
+            self.transport.local_version,
+            self.transport.remote_kex_init,
+            self.transport.local_kex_init,
+        )
+        hm.add_string(K_S)
+        hm.add_string(Q_C_bytes)
+        # SEC1: V2.0  2.3.3 Elliptic-Curve-Point-to-Octet-String Conversion
+        hm.add_string(
+            self.Q_S.public_bytes(
+                serialization.Encoding.X962,
+                serialization.PublicFormat.UncompressedPoint,
+            )
+        )
+        hm.add_mpint(int(K))
+        H = self.hash_algo(hm.asbytes()).digest()
+        self.transport._set_K_H(K, H)
+        sig = self.transport.get_server_key().sign_ssh_data(
+            H, self.transport.host_key_type
+        )
+        # construct reply
+        m = Message()
+        m.add_byte(c_MSG_KEXECDH_REPLY)
+        m.add_string(K_S)
+        m.add_string(
+            self.Q_S.public_bytes(
+                serialization.Encoding.X962,
+                serialization.PublicFormat.UncompressedPoint,
+            )
+        )
+        m.add_string(sig)
+        self.transport._send_message(m)
+        self.transport._activate_outbound()
+
+    def _parse_kexecdh_reply(self, m):
+        K_S = m.get_string()
+        Q_S_bytes = m.get_string()
+        self.Q_S = ec.EllipticCurvePublicKey.from_encoded_point(
+            self.curve, Q_S_bytes
+        )
+        sig = m.get_binary()
+        K = self.P.exchange(ec.ECDH(), self.Q_S)
+        K = int(hexlify(K), 16)
+        # compute exchange hash and verify signature
+        hm = Message()
+        hm.add(
+            self.transport.local_version,
+            self.transport.remote_version,
+            self.transport.local_kex_init,
+            self.transport.remote_kex_init,
+        )
+        hm.add_string(K_S)
+        # SEC1: V2.0  2.3.3 Elliptic-Curve-Point-to-Octet-String Conversion
+        hm.add_string(
+            self.Q_C.public_bytes(
+                serialization.Encoding.X962,
+                serialization.PublicFormat.UncompressedPoint,
+            )
+        )
+        hm.add_string(Q_S_bytes)
+        hm.add_mpint(K)
+        self.transport._set_K_H(K, self.hash_algo(hm.asbytes()).digest())
+        self.transport._verify_key(K_S, sig)
+        self.transport._activate_outbound()
+
+
+class KexNistp384(KexNistp256):
+    name = "ecdh-sha2-nistp384"
+    hash_algo = sha384
+    curve = ec.SECP384R1()
+
+
+class KexNistp521(KexNistp256):
+    name = "ecdh-sha2-nistp521"
+    hash_algo = sha512
+    curve = ec.SECP521R1()