[project @ Arch-1:robey@lag.net--2003-public%secsh--dev--1.0--patch-12]

fix dss key signing
(expanded on a patch from fred gansevles)
add a demo dss key for server mode, and fix some bugs that had caused the dss
signing stuff to never work before.  the demo_server is a bit more verbose
now, too.  both key types (RSAKey & DSSKey) now have a function to return the
fingerprint of the key, and both versions of read_private_key_file() now raise
exceptions on failure, instead of just silently setting "valid" to false.

demo_dss_key

@@ -0,0 +1,12 @@
+-----BEGIN DSA PRIVATE KEY-----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+-----END DSA PRIVATE KEY-----

demo_server.py

@@ -12,8 +12,12 @@ if len(l.handlers) == 0:
     lh.setFormatter(logging.Formatter('%(levelname)-.3s [%(asctime)s] %(name)s: %(message)s', '%Y%m%d:%H%M%S'))
     l.addHandler(lh)
 
-host_key = paramiko.RSAKey()
-host_key.read_private_key_file('demo_host_key')
+#host_key = paramiko.RSAKey()
+#host_key.read_private_key_file('demo_host_key')
+
+host_key = paramiko.DSSKey()
+host_key.read_private_key_file('demo_dss_key')
+print 'Read key: ' + paramiko.hexify(host_key.get_fingerprint())
 
 
 class ServerTransport(paramiko.Transport):
@@ -54,12 +58,15 @@ except Exception, e:
 
 try:
     sock.listen(100)
+    print 'Listening for connection ...'
     client, addr = sock.accept()
 except Exception, e:
     print '*** Listen/accept failed: ' + str(e)
     traceback.print_exc()
     sys.exit(1)
 
+print 'Got a connection!'
+
 try:
     event = threading.Event()
     t = ServerTransport(client)

dsskey.py

@@ -1,11 +1,12 @@
 #!/usr/bin/python
 
 import base64
+from paramiko import SSHException
 from message import Message
 from transport import MSG_USERAUTH_REQUEST
 from util import inflate_long, deflate_long
 from Crypto.PublicKey import DSA
-from Crypto.Hash import SHA
+from Crypto.Hash import SHA, MD5
 from ber import BER
 
 from util import format_binary
@@ -38,6 +39,9 @@ class DSSKey(object):
     def get_name(self):
         return 'ssh-dss'
 
+    def get_fingerprint(self):
+        return MD5.new(str(self)).digest()
+        
     def verify_ssh_sig(self, data, msg):
         if not self.valid:
             return 0
@@ -58,7 +62,7 @@ class DSSKey(object):
         dss = DSA.construct((long(self.y), long(self.g), long(self.p), long(self.q)))
         return dss.verify(sigM, (sigR, sigS))
 
-    def sign_ssh_data(self, data):
+    def sign_ssh_data(self, randpool, data):
         hash = SHA.new(data).digest()
         dss = DSA.construct((long(self.y), long(self.g), long(self.p), long(self.q), long(self.x)))
         # generate a suitable k
@@ -74,24 +78,19 @@ class DSSKey(object):
         return str(m)
 
     def read_private_key_file(self, filename):
+        "throws a file exception, or SSHException (on invalid key, or base64 decoding exception"
         # private key file contains:
         # DSAPrivateKey = { version = 0, p, q, g, y, x }
         self.valid = 0
-        try:
         f = open(filename, 'r')
         lines = f.readlines()
         f.close()
-        except:
-            return
         if lines[0].strip() != '-----BEGIN DSA PRIVATE KEY-----':
-            return
-        try:
+            raise SSHException('not a valid DSA private key file')
         data = base64.decodestring(''.join(lines[1:-1]))
-        except:
-            return
         keylist = BER(data).decode()
         if (type(keylist) != type([])) or (len(keylist) < 6) or (keylist[0] != 0):
-            return
+            raise SSHException('not a valid DSA private key file (bad ber encoding)')
         self.p = keylist[1]
         self.q = keylist[2]
         self.g = keylist[3]
@@ -110,4 +109,4 @@ class DSSKey(object):
         m.add_boolean(1)
         m.add_string('ssh-dss')
         m.add_string(str(self))
-        return self.sign_ssh_data(str(m))
+        return self.sign_ssh_data(randpool, str(m))

kex_gex.py

@@ -138,7 +138,7 @@ class KexGex(object):
         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)
+        sig = self.transport.get_server_key().sign_ssh_data(self.transport.randpool, H)
         # send reply
         m = Message()
         m.add_byte(chr(MSG_KEXDH_GEX_REPLY))

kex_group1.py

@@ -92,7 +92,7 @@ class KexGroup1(object):
         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)
+        sig = self.transport.get_server_key().sign_ssh_data(self.transport.randpool, H)
         # send reply
         m = Message()
         m.add_byte(chr(MSG_KEXDH_REPLY))

paramiko.py

@@ -14,6 +14,8 @@ from channel import Channel
 from rsakey import RSAKey
 from dsskey import DSSKey
 
+from util import hexify
+
 
 __author__ = "Robey Pointer <robey@lag.net>"
 __date__ = "10 Nov 2003"

rsakey.py

@@ -31,6 +31,9 @@ class RSAKey(object):
     def get_name(self):
         return 'ssh-rsa'
 
+    def get_fingerprint(self):
+        return MD5.new(str(self)).digest()
+
     def pkcs1imify(self, data):
         """
         turn a 20-byte SHA1 hash into a blob of data as large as the key's N,
@@ -51,7 +54,7 @@ class RSAKey(object):
         rsa = RSA.construct((long(self.n), long(self.e)))
         return rsa.verify(hash, (sig,))
 
-    def sign_ssh_data(self, data):
+    def sign_ssh_data(self, randpool, data):
         hash = SHA.new(data).digest()
         rsa = RSA.construct((long(self.n), long(self.e), long(self.d)))
         sig = deflate_long(rsa.sign(self.pkcs1imify(hash), '')[0], 0)
@@ -61,24 +64,19 @@ class RSAKey(object):
         return str(m)
 
     def read_private_key_file(self, filename):
+        "throws a file exception, or SSHException (on invalid key), or base64 decoding exception"
         # private key file contains:
         # RSAPrivateKey = { version = 0, n, e, d, p, q, d mod p-1, d mod q-1, q**-1 mod p }
         self.valid = 0
-        try:
         f = open(filename, 'r')
         lines = f.readlines()
         f.close()
-        except:
-            return
         if lines[0].strip() != '-----BEGIN RSA PRIVATE KEY-----':
-            return
-        try:
+            raise SSHException('not a valid DSA private key file')
         data = base64.decodestring(''.join(lines[1:-1]))
-        except:
-            return
         keylist = BER(data).decode()
         if (type(keylist) != type([])) or (len(keylist) < 4) or (keylist[0] != 0):
-            return
+            raise SSHException('not a valid DSA private key file (bad ber encoding)')
         self.n = keylist[1]
         self.e = keylist[2]
         self.d = keylist[3]
@@ -98,5 +96,5 @@ class RSAKey(object):
         m.add_boolean(1)
         m.add_string('ssh-rsa')
         m.add_string(str(self))
-        return self.sign_ssh_data(str(m))
+        return self.sign_ssh_data(randpool, str(m))
 

transport.py

@@ -532,7 +532,7 @@ class BaseTransport(threading.Thread):
         m.add_byte(chr(MSG_KEXINIT))
         m.add_bytes(randpool.get_bytes(16))
         m.add(','.join(self.preferred_kex))
-        m.add(','.join(self.available_server_keys))
+        m.add(','.join(available_server_keys))
         m.add(','.join(self.preferred_ciphers))
         m.add(','.join(self.preferred_ciphers))
         m.add(','.join(self.preferred_macs))