Mini Shell

"""M2Crypto wrapper for OpenSSL BIO API.

Copyright (c) 1999-2004 Ng Pheng Siong. All rights reserved."""

import m2 

# Deprecated
from m2 import bio_do_handshake as bio_do_ssl_handshake

from cStringIO import StringIO

class BIOError(Exception): pass

m2.bio_init(BIOError)

class BIO:

    """Abstract object interface to the BIO API."""

    m2_bio_free = m2.bio_free

    def __init__(self, bio=None, _pyfree=0, _close_cb=None):
        self.bio = bio
        self._pyfree = _pyfree
        self._close_cb = _close_cb
        self.closed = 0
        self.write_closed = 0
        
    def __del__(self):
        if self._pyfree:
            self.m2_bio_free(self.bio)

    def _ptr(self):
        return self.bio

    # Deprecated.
    bio_ptr = _ptr

    def fileno(self):
        return m2.bio_get_fd(self.bio)

    def readable(self):
        return not self.closed

    def read(self, size=None):
        if not self.readable():
            raise IOError, 'cannot read'
        if size is None:
            buf = StringIO()
            while 1:
                data = m2.bio_read(self.bio, 4096)
                if not data: break
                buf.write(data)
            return buf.getvalue()
        elif size == 0:
            return ''
        elif size < 0:
            raise ValueError, 'read count is negative'
        else:
            return m2.bio_read(self.bio, size)

    def readline(self, size=4096):
        if not self.readable():
            raise IOError, 'cannot read'
        buf = m2.bio_gets(self.bio, size)
        return buf

    def readlines(self, sizehint='ignored'):
        if not self.readable():
            raise IOError, 'cannot read'
        lines=[]
        while 1:
            buf=m2.bio_gets(self.bio, 4096)
            if buf is None:
                break
            lines.append(buf)
        return lines

    def writeable(self):
        return (not self.closed) and (not self.write_closed)
       
    def write(self, data):
        if not self.writeable():
            raise IOError, 'cannot write'
        return m2.bio_write(self.bio, data)

    def write_close(self):
        self.write_closed = 1

    def flush(self):
        m2.bio_flush(self.bio)

    def reset(self):
        """
        Sets the bio to its initial state
        """
        return m2.bio_reset(self.bio)

    def close(self):
        self.closed = 1
        if self._close_cb:
            self._close_cb()

    def should_retry(self):
        """
        Can the call be attempted again, or was there an error
        ie do_handshake 
       
        """
        return m2.bio_should_retry(self.bio) 

    def should_read(self):
        """
        Returns whether the cause of the condition is the bio
        should read more data
        """
        return m2.bio_should_read(self.bio)
    
    def should_write(self):
        """
        Returns whether the cause of the condition is the bio
        should write more data
        """
        return m2.bio_should_write(self.bio)
    
class MemoryBuffer(BIO):

    """
    Object interface to BIO_s_mem. 
    
    Empirical testing suggests that this class performs less well than cStringIO, 
    because cStringIO is implemented in C, whereas this class is implemented in 
    Python. Thus, the recommended practice is to use cStringIO for regular work and 
    convert said cStringIO object to a MemoryBuffer object only when necessary.
    """

    def __init__(self, data=None):
        BIO.__init__(self)
        self.bio = m2.bio_new(m2.bio_s_mem())
        self._pyfree = 1
        if data is not None:
            m2.bio_write(self.bio, data)

    def __len__(self):
        return m2.bio_ctrl_pending(self.bio)

    def read(self, size=0):
        if not self.readable():
            raise IOError, 'cannot read'
        if size:
            return m2.bio_read(self.bio, size)
        else:
            return m2.bio_read(self.bio, m2.bio_ctrl_pending(self.bio))
            
    # Backwards-compatibility.
    getvalue = read_all = read

    def write_close(self):
        self.write_closed = 1
        m2.bio_set_mem_eof_return(self.bio, 0)

    close = write_close


class File(BIO):

    """
    Object interface to BIO_s_fp. 
    
    This class interfaces Python to OpenSSL functions that expect BIO *. For
    general file manipulation in Python, use Python's builtin file object.
    """

    def __init__(self, pyfile, close_pyfile=1):
        BIO.__init__(self, _pyfree=1)
        self.pyfile = pyfile
        self.close_pyfile = close_pyfile
        self.bio = m2.bio_new_fp(pyfile, 0)

    def close(self):
        self.closed = 1
        if self.close_pyfile:
            self.pyfile.close()

def openfile(filename, mode='rb'):
    return File(open(filename, mode))


class IOBuffer(BIO):

    """
    Object interface to BIO_f_buffer. 
    
    Its principal function is to be BIO_push()'ed on top of a BIO_f_ssl, so
    that makefile() of said underlying SSL socket works.
    """

    m2_bio_pop = m2.bio_pop
    m2_bio_free = m2.bio_free

    def __init__(self, under_bio, mode='rwb', _pyfree=1):
        BIO.__init__(self, _pyfree=_pyfree)
        self.io = m2.bio_new(m2.bio_f_buffer())
        self.bio = m2.bio_push(self.io, under_bio._ptr())
        # This reference keeps the underlying BIO alive while we're not closed.
        self._under_bio = under_bio 
        if 'w' in mode:
            self.write_closed = 0
        else:
            self.write_closed = 1
            
    def __del__(self):
        if getattr(self, '_pyfree', 0):
            self.m2_bio_pop(self.bio)
        self.m2_bio_free(self.io)

    def close(self):
        BIO.close(self)


class CipherStream(BIO):

    """
    Object interface to BIO_f_cipher.
    """

    SALT_LEN = m2.PKCS5_SALT_LEN

    m2_bio_pop = m2.bio_pop
    m2_bio_free = m2.bio_free

    def __init__(self, obio):
        BIO.__init__(self, _pyfree=1)
        self.obio = obio
        self.bio = m2.bio_new(m2.bio_f_cipher())
        self.closed = 0
        
    def __del__(self):
        if not getattr(self, 'closed', 1):
            self.close()

    def close(self):
        self.m2_bio_pop(self.bio)
        self.m2_bio_free(self.bio)
        self.closed = 1
        
    def write_close(self):
        self.obio.write_close()

    def set_cipher(self, algo, key, iv, op):
        cipher = getattr(m2, algo, None)
        if cipher is None:
            raise ValueError, ('unknown cipher', algo)
        m2.bio_set_cipher(self.bio, cipher(), key, iv, op) 
        m2.bio_push(self.bio, self.obio._ptr())


class SSLBio(BIO):
    """
    Object interface to BIO_f_ssl 
    """
    def __init__(self, _pyfree=1):
        BIO.__init__(self, _pyfree)
        self.bio = m2.bio_new(m2.bio_f_ssl())
        self.closed = 0

   
    def set_ssl(self, conn, close_flag=m2.bio_noclose):
        """
        Sets the bio to the SSL pointer which is
        contained in the connection object.  
        """
        self._pyfree = 0 
        m2.bio_set_ssl(self.bio, conn.ssl, close_flag)
        if close_flag == m2.bio_noclose:
            conn.set_ssl_close_flag(m2.bio_close)
       
    def do_handshake(self):
        """
        Do the handshake.
        
        Return 1 if the handshake completes
        Return 0 or a negative number if there is a problem
        """
        return m2.bio_do_handshake(self.bio)