[project @ Arch-1:robey@lag.net--2003-public%secsh--dev--1.0--patch-87]

clean up pkey interface
change the pkey interface so that it's no longer possible to have a pkey
that doesn't represent a valid key.  (ie: no more "blank" key objects.)
also add "get_bits" and "can_sign" methods to determine the key bit length
and whether it can sign things (contains the "private parts") respectively.

3 files changed, 144 insertions, 132 deletions

diff --git a/paramiko/dsskey.py b/paramiko/dsskey.py
index eaefba3f..09952b9d 100644
--- a/paramiko/dsskey.py
+++ b/paramiko/dsskey.py
@@ -38,22 +38,24 @@ class DSSKey (PKey):
     data.
     """
 
-    def __init__(self, msg=None, data=None):
-        self.valid = False
+    def __init__(self, msg=None, data=None, filename=None, password=None, vals=None):
+        if filename is not None:
+            self._from_private_key_file(filename, password)
+            return
         if (msg is None) and (data is not None):
             msg = Message(data)
-        if (msg is None) or (msg.get_string() != 'ssh-dss'):
-            return
-        self.p = msg.get_mpint()
-        self.q = msg.get_mpint()
-        self.g = msg.get_mpint()
-        self.y = msg.get_mpint()
-        self.size = len(util.deflate_long(self.p, 0))
-        self.valid = True
+        if vals is not None:
+            self.p, self.q, self.g, self.y = vals
+        else:
+            if (msg is None) or (msg.get_string() != 'ssh-dss'):
+                raise SSHException('Invalid key')
+            self.p = msg.get_mpint()
+            self.q = msg.get_mpint()
+            self.g = msg.get_mpint()
+            self.y = msg.get_mpint()
+        self.size = util.bit_length(self.p)
 
     def __str__(self):
-        if not self.valid:
-            return ''
         m = Message()
         m.add_string('ssh-dss')
         m.add_mpint(self.p)
@@ -74,6 +76,12 @@ class DSSKey (PKey):
     def get_name(self):
         return 'ssh-dss'
 
+    def get_bits(self):
+        return self.size
+        
+    def can_sign(self):
+        return hasattr(self, 'x')
+
     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)))
@@ -90,8 +98,6 @@ class DSSKey (PKey):
         return m
 
     def verify_ssh_sig(self, data, msg):
-        if not self.valid:
-            return 0
         if len(str(msg)) == 40:
             # spies.com bug: signature has no header
             sig = str(msg)
@@ -109,28 +115,7 @@ class DSSKey (PKey):
         dss = DSA.construct((long(self.y), long(self.g), long(self.p), long(self.q)))
         return dss.verify(sigM, (sigR, sigS))
 
-    def read_private_key_file(self, filename, password=None):
-        # private key file contains:
-        # DSAPrivateKey = { version = 0, p, q, g, y, x }
-        self.valid = False
-        data = self._read_private_key_file('DSA', filename, password)
-        try:
-            keylist = BER(data).decode()
-        except BERException, x:
-            raise SSHException('Unable to parse key file: ' + str(x))
-        if (type(keylist) is not list) or (len(keylist) < 6) or (keylist[0] != 0):
-            raise SSHException('not a valid DSA private key file (bad ber encoding)')
-        self.p = keylist[1]
-        self.q = keylist[2]
-        self.g = keylist[3]
-        self.y = keylist[4]
-        self.x = keylist[5]
-        self.size = len(util.deflate_long(self.p, 0))
-        self.valid = True
-
     def write_private_key_file(self, filename, password=None):
-        if not self.valid:
-            raise SSHException('Invalid key')
         keylist = [ 0, self.p, self.q, self.g, self.y, self.x ]
         try:
             b = BER()
@@ -155,12 +140,29 @@ class DSSKey (PKey):
         @since: fearow
         """
         dsa = DSA.generate(bits, randpool.get_bytes, progress_func)
-        key = DSSKey()
-        key.p = dsa.p
-        key.q = dsa.q
-        key.g = dsa.g
-        key.y = dsa.y
+        key = DSSKey(vals=(dsa.p, dsa.q, dsa.g, dsa.y))
         key.x = dsa.x
-        key.valid = True
         return key
     generate = staticmethod(generate)
+
+
+    ###  internals...
+
+
+    def _from_private_key_file(self, filename, password):
+        # private key file contains:
+        # DSAPrivateKey = { version = 0, p, q, g, y, x }
+        data = self._read_private_key_file('DSA', filename, password)
+        try:
+            keylist = BER(data).decode()
+        except BERException, x:
+            raise SSHException('Unable to parse key file: ' + str(x))
+        if (type(keylist) is not list) or (len(keylist) < 6) or (keylist[0] != 0):
+            raise SSHException('not a valid DSA private key file (bad ber encoding)')
+        self.p = keylist[1]
+        self.q = keylist[2]
+        self.g = keylist[3]
+        self.y = keylist[4]
+        self.x = keylist[5]
+        self.size = util.bit_length(self.p)
+
diff --git a/paramiko/pkey.py b/paramiko/pkey.py
index 8faacc5b..a7dc8a8f 100644
--- a/paramiko/pkey.py
+++ b/paramiko/pkey.py
@@ -55,7 +55,10 @@ class PKey (object):
         type.
         @type msg: L{Message}
         @param data: an optional string containing a public key of this type
-        @type data: string
+        @type data: str
+
+        @raise SSHException: if a key cannot be created from the C{data} or
+        C{msg} given, or no key was passed in.
         """
         pass
 
@@ -66,7 +69,7 @@ class PKey (object):
         re-create the key object later.
 
         @return: string representation of an SSH key message.
-        @rtype: string
+        @rtype: str
         """
         return ''
 
@@ -94,10 +97,30 @@ class PKey (object):
 
         @return: name of this private key type, in SSH terminology (for
         example, C{"ssh-rsa"}).
-        @rtype: string
+        @rtype: str
         """
         return ''
 
+    def get_bits(self):
+        """
+        Return the number of significant bits in this key.  This is useful
+        for judging the relative security of a key.
+
+        @return: bits in the key.
+        @rtype: int
+        """
+        return 0
+
+    def can_sign(self):
+        """
+        Return C{True} if this key has the private part necessary for signing
+        data.
+
+        @return: C{True} if this is a private key.
+        @rtype: bool
+        """
+        return False
+
     def get_fingerprint(self):
         """
         Return an MD5 fingerprint of the public part of this key.  Nothing
@@ -105,7 +128,7 @@ class PKey (object):
 
         @return: a 16-byte string (binary) of the MD5 fingerprint, in SSH
         format.
-        @rtype: string
+        @rtype: str
         """
         return MD5.new(str(self)).digest()
 
@@ -116,7 +139,7 @@ class PKey (object):
         public key files or recognized host keys.
 
         @return: a base64 string containing the public part of the key.
-        @rtype: string
+        @rtype: str
 
         @since: fearow
         """
@@ -130,7 +153,7 @@ class PKey (object):
         @param randpool: a secure random number generator.
         @type randpool: L{Crypto.Util.randpool.RandomPool}
         @param data: the data to sign.
-        @type data: string
+        @type data: str
         @return: an SSH signature message.
         @rtype: L{Message}
         """
@@ -142,7 +165,7 @@ class PKey (object):
         that data, verify that it was signed with this key.
 
         @param data: the data that was signed.
-        @type data: string
+        @type data: str
         @param msg: an SSH signature message
         @type msg: L{Message}
         @return: C{True} if the signature verifies correctly; C{False}
@@ -150,40 +173,21 @@ class PKey (object):
         @rtype: boolean
         """
         return False
-    
-    def read_private_key_file(self, filename, password=None):
+   
+    def from_private_key_file(cl, filename, password=None):
         """
-        Read private key contents from a file into this object.  If the private
+        Create a key object by reading a private key file.  If the private
         key is encrypted and C{password} is not C{None}, the given password
         will be used to decrypt the key (otherwise L{PasswordRequiredException}
-        is thrown).
-
-        @param filename: name of the file to read.
-        @type filename: string
-        @param password: an optional password to use to decrypt the key file,
-        if it's encrypted.
-        @type password: string
-
-        @raise IOError: if there was an error reading the file.
-        @raise PasswordRequiredException: if the private key file is
-        encrypted, and C{password} is C{None}.
-        @raise SSHException: if the key file is invalid.
-        """
-        raise exception('Not implemented in PKey')
-
-    def from_private_key_file(cl, filename, password=None):
-        """
-        Create a key object by reading a private key file.  This is roughly
-        equivalent to creating a new key object and then calling
-        L{read_private_key_file} on it.  Through the magic of python, this
-        factory method will exist in all subclasses of PKey (such as L{RSAKey}
-        or L{DSSKey}), but is useless on the abstract PKey class.
+        is thrown).  Through the magic of python, this factory method will
+        exist in all subclasses of PKey (such as L{RSAKey} or L{DSSKey}), but
+        is useless on the abstract PKey class.
 
         @param filename: name of the file to read.
-        @type filename: string
+        @type filename: str
         @param password: an optional password to use to decrypt the key file,
         if it's encrypted
-        @type password: string
+        @type password: str
         @return: a new key object based on the given private key.
         @rtype: L{PKey}
 
@@ -194,8 +198,7 @@ class PKey (object):
 
         @since: fearow
         """
-        key = cl()
-        key.read_private_key_file(filename, password)
+        key = cl(filename=filename, password=password)
         return key
     from_private_key_file = classmethod(from_private_key_file)
 
@@ -205,9 +208,9 @@ class PKey (object):
         C{None}, the key is encrypted before writing.
 
         @param filename: name of the file to write.
-        @type filename: string
+        @type filename: str
         @param password: an optional password to use to encrypt the key file.
-        @type password: string
+        @type password: str
 
         @raise IOError: if there was an error writing the file.
         @raise SSHException: if the key is invalid.
@@ -225,14 +228,14 @@ class PKey (object):
         the key (otherwise L{PasswordRequiredException} is thrown).
 
         @param tag: C{"RSA"} or C{"DSA"}, the tag used to mark the data block.
-        @type tag: string
+        @type tag: str
         @param filename: name of the file to read.
-        @type filename: string
+        @type filename: str
         @param password: an optional password to use to decrypt the key file,
         if it's encrypted.
-        @type password: string
+        @type password: str
         @return: data blob that makes up the private key.
-        @rtype: string
+        @rtype: str
 
         @raise IOError: if there was an error reading the file.
         @raise PasswordRequiredException: if the private key file is
@@ -296,13 +299,13 @@ class PKey (object):
         a password is given, DES-EDE3-CBC is used.
 
         @param tag: C{"RSA"} or C{"DSA"}, the tag used to mark the data block.
-        @type tag: string
+        @type tag: str
         @param filename: name of the file to write.
-        @type filename: string
+        @type filename: str
         @param data: data blob that makes up the private key.
-        @type data: string
+        @type data: str
         @param password: an optional password to use to encrypt the file.
-        @type password: string
+        @type password: str
 
         @raise IOError: if there was an error writing the file.
         """
diff --git a/paramiko/rsakey.py b/paramiko/rsakey.py
index aa85724c..e9e7d01a 100644
--- a/paramiko/rsakey.py
+++ b/paramiko/rsakey.py
@@ -39,20 +39,22 @@ class RSAKey (PKey):
     data.
     """
 
-    def __init__(self, msg=None, data=''):
-        self.valid = False
+    def __init__(self, msg=None, data='', filename=None, password=None, vals=None):
+        if filename is not None:
+            self._from_private_key_file(filename, password)
+            return
         if (msg is None) and (data is not None):
             msg = Message(data)
-        if (msg is None) or (msg.get_string() != 'ssh-rsa'):
-            return
-        self.e = msg.get_mpint()
-        self.n = msg.get_mpint()
-        self.size = len(util.deflate_long(self.n, 0))
-        self.valid = True
+        if vals is not None:
+            self.e, self.n = vals
+        else:
+            if (msg is None) or (msg.get_string() != 'ssh-rsa'):
+                raise SSHException('Invalid key')
+            self.e = msg.get_mpint()
+            self.n = msg.get_mpint()
+        self.size = util.bit_length(self.n)
 
     def __str__(self):
-        if not self.valid:
-            return ''
         m = Message()
         m.add_string('ssh-rsa')
         m.add_mpint(self.e)
@@ -68,14 +70,11 @@ class RSAKey (PKey):
     def get_name(self):
         return 'ssh-rsa'
 
-    def _pkcs1imify(self, data):
-        """
-        turn a 20-byte SHA1 hash into a blob of data as large as the key's N,
-        using PKCS1's \"emsa-pkcs1-v1_5\" encoding.  totally bizarre.
-        """
-        SHA1_DIGESTINFO = '\x30\x21\x30\x09\x06\x05\x2b\x0e\x03\x02\x1a\x05\x00\x04\x14'
-        filler = '\xff' * (self.size - len(SHA1_DIGESTINFO) - len(data) - 3)
-        return '\x00\x01' + filler + '\x00' + SHA1_DIGESTINFO + data
+    def get_bits(self):
+        return self.size
+
+    def can_sign(self):
+        return hasattr(self, 'd')
 
     def sign_ssh_data(self, randpool, data):
         hash = SHA.new(data).digest()
@@ -87,7 +86,7 @@ class RSAKey (PKey):
         return m
 
     def verify_ssh_sig(self, data, msg):
-        if (not self.valid) or (msg.get_string() != 'ssh-rsa'):
+        if msg.get_string() != 'ssh-rsa':
             return False
         sig = util.inflate_long(msg.get_string(), 1)
         # verify the signature by SHA'ing the data and encrypting it using the
@@ -97,29 +96,7 @@ class RSAKey (PKey):
         rsa = RSA.construct((long(self.n), long(self.e)))
         return rsa.verify(hash, (sig,))
 
-    def read_private_key_file(self, filename, password=None):
-        # 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 = False
-        data = self._read_private_key_file('RSA', filename, password)
-        try:
-            keylist = BER(data).decode()
-        except BERException:
-            raise SSHException('Unable to parse key file')
-        if (type(keylist) is not list) or (len(keylist) < 4) or (keylist[0] != 0):
-            raise SSHException('Not a valid RSA private key file (bad ber encoding)')
-        self.n = keylist[1]
-        self.e = keylist[2]
-        self.d = keylist[3]
-        # not really needed
-        self.p = keylist[4]
-        self.q = keylist[5]
-        self.size = len(util.deflate_long(self.n, 0))
-        self.valid = True
-
     def write_private_key_file(self, filename, password=None):
-        if not self.valid:
-            raise SSHException('Invalid key')
         keylist = [ 0, self.n, self.e, self.d, self.p, self.q,
                     self.d % (self.p - 1), self.d % (self.q - 1),
                     util.mod_inverse(self.q, self.p) ]
@@ -146,12 +123,42 @@ class RSAKey (PKey):
         @since: fearow
         """
         rsa = RSA.generate(bits, randpool.get_bytes, progress_func)
-        key = RSAKey()
-        key.n = rsa.n
-        key.e = rsa.e
+        key = RSAKey(vals=(rsa.e, rsa.n))
         key.d = rsa.d
         key.p = rsa.p
         key.q = rsa.q
-        key.valid = True
         return key
     generate = staticmethod(generate)
+
+
+    ###  internals...
+
+
+    def _pkcs1imify(self, data):
+        """
+        turn a 20-byte SHA1 hash into a blob of data as large as the key's N,
+        using PKCS1's \"emsa-pkcs1-v1_5\" encoding.  totally bizarre.
+        """
+        SHA1_DIGESTINFO = '\x30\x21\x30\x09\x06\x05\x2b\x0e\x03\x02\x1a\x05\x00\x04\x14'
+        size = len(util.deflate_long(self.n, 0))
+        filler = '\xff' * (size - len(SHA1_DIGESTINFO) - len(data) - 3)
+        return '\x00\x01' + filler + '\x00' + SHA1_DIGESTINFO + data
+
+    def _from_private_key_file(self, filename, password):
+        # private key file contains:
+        # RSAPrivateKey = { version = 0, n, e, d, p, q, d mod p-1, d mod q-1, q**-1 mod p }
+        data = self._read_private_key_file('RSA', filename, password)
+        try:
+            keylist = BER(data).decode()
+        except BERException:
+            raise SSHException('Unable to parse key file')
+        if (type(keylist) is not list) or (len(keylist) < 4) or (keylist[0] != 0):
+            raise SSHException('Not a valid RSA private key file (bad ber encoding)')
+        self.n = keylist[1]
+        self.e = keylist[2]
+        self.d = keylist[3]
+        # not really needed
+        self.p = keylist[4]
+        self.q = keylist[5]
+        self.size = util.bit_length(self.n)
+