[project @ Arch-1:robey@lag.net--2003-public%secsh--dev--1.0--base-0]

initial import

(automatically generated log message)

1 files changed, 104 insertions, 0 deletions

diff --git a/kex_group1.py b/kex_group1.py
new file mode 100644
index 00000000..7d65c388
--- /dev/null
+++ b/kex_group1.py
@@ -0,0 +1,104 @@
+#!/usr/bin/python
+
+# standard SSH key exchange ("kex" if you wanna sound cool):
+# diffie-hellman of 1024 bit key halves, using a known "p" prime and
+# "g" generator.
+
+from message import Message, inflate_long
+from secsh import SSHException
+from transport import MSG_NEWKEYS
+from Crypto.Hash import SHA
+from logging import DEBUG, INFO, WARNING, ERROR, CRITICAL
+
+MSG_KEXDH_INIT, MSG_KEXDH_REPLY = range(30, 32)
+
+# draft-ietf-secsh-transport-09.txt, page 17
+P = 0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFFL
+G = 2
+
+
+class KexGroup1(object):
+
+    name = 'diffie-hellman-group1-sha1'
+
+    def __init__(self, transport):
+        self.transport = transport
+
+    def generate_x(self):
+        # generate an "x" (1 < x < q), where q is (p-1)/2.
+        # p is a 128-byte (1024-bit) number, where the first 64 bits are 1. 
+        # therefore q can be approximated as a 2^1023.  we drop the subset of
+        # potential x where the first 63 bits are 1, because some of those will be
+        # larger than q (but this is a tiny tiny subset of potential x).
+        while 1:
+            self.transport.randpool.stir()
+            x_bytes = self.transport.randpool.get_bytes(128)
+            x_bytes = chr(ord(x_bytes[0]) & 0x7f) + x_bytes[1:]
+            if (x_bytes[:8] != '\x7F\xFF\xFF\xFF\xFF\xFF\xFF\xFF') and \
+                   (x_bytes[:8] != '\x00\x00\x00\x00\x00\x00\x00\x00'):
+                break
+        self.x = inflate_long(x_bytes)
+
+    def start_kex(self):
+        self.generate_x()
+        if self.transport.server_mode:
+            # compute f = g^x mod p, but don't send it yet
+            self.f = pow(G, self.x, P)
+            self.transport.expected_packet = MSG_KEXDH_INIT
+            return
+        # compute e = g^x mod p (where g=2), and send it
+        self.e = pow(G, self.x, P)
+        m = Message()
+        m.add_byte(chr(MSG_KEXDH_INIT))
+        m.add_mpint(self.e)
+        self.transport.send_message(m)
+        self.transport.expected_packet = MSG_KEXDH_REPLY
+
+    def parse_next(self, ptype, m):
+        if self.transport.server_mode and (ptype == MSG_KEXDH_INIT):
+            return self.parse_kexdh_init(m)
+        elif not self.transport.server_mode and (ptype == MSG_KEXDH_REPLY):
+            return self.parse_kexdh_reply(m)
+        raise SSHException('KexGroup1 asked to handle packet type %d' % ptype)
+
+    def parse_kexdh_reply(self, m):
+        # client mode
+        host_key = m.get_string()
+        self.f = m.get_mpint()
+        if (self.f < 1) or (self.f > P - 1):
+            raise SSHException('Server kex "f" is out of range')
+        sig = m.get_string()
+        K = pow(self.f, self.x, P)
+        # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K)
+        hm = Message().add(self.transport.local_version).add(self.transport.remote_version)
+        hm.add(self.transport.local_kex_init).add(self.transport.remote_kex_init).add(host_key)
+        hm.add(self.e).add(self.f).add(K)
+        self.transport.set_K_H(K, SHA.new(str(hm)).digest())
+        self.transport.verify_key(host_key, sig)
+        self.transport.activate_outbound()
+        self.transport.expected_packet = MSG_NEWKEYS
+
+    def parse_kexdh_init(self, m):
+        # server mode
+        self.e = m.get_mpint()
+        if (self.e < 1) or (self.e > P - 1):
+            raise SSHException('Client kex "e" is out of range')
+        K = pow(self.e, self.x, P)
+        key = str(self.transport.get_server_key())
+        # okay, build up the hash H of (V_C || V_S || I_C || I_S || K_S || e || f || K)
+        hm = Message().add(self.transport.remote_version).add(self.transport.local_version)
+        hm.add(self.transport.remote_kex_init).add(self.transport.local_kex_init).add(key)
+        hm.add(self.e).add(self.f).add(K)
+        H = SHA.new(str(hm)).digest()
+        self.transport.set_K_H(K, H)
+        # sign it
+        sig = self.transport.get_server_key().sign_ssh_data(H)
+        # send reply
+        m = Message()
+        m.add_byte(chr(MSG_KEXDH_REPLY))
+        m.add_string(key)
+        m.add_mpint(self.f)
+        m.add_string(sig)
+        self.transport.send_message(m)
+        self.transport.activate_outbound()
+        self.transport.expected_packet = MSG_NEWKEYS