Source Code for Module paramiko.rng_posix

 1  #!/usr/bin/python 
 2  # -*- coding: ascii -*- 
 3  # Copyright (C) 2008  Dwayne C. Litzenberger <dlitz@dlitz.net> 
 4  # Copyright (C) 2008  Open Systems Canada Limited 
 5  # 
 6  # This file is part of paramiko. 
 7  # 
 8  # Paramiko is free software; you can redistribute it and/or modify it under the 
 9  # terms of the GNU Lesser General Public License as published by the Free 
10  # Software Foundation; either version 2.1 of the License, or (at your option) 
11  # any later version. 
12  # 
13  # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY 
14  # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR 
15  # A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more 
16  # details. 
17  # 
18  # You should have received a copy of the GNU Lesser General Public License 
19  # along with Paramiko; if not, write to the Free Software Foundation, Inc., 
20  # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 
21   
22  import os 
23  import stat 
24   
25 -class error(Exception): 
26      pass 
27   
28 -class _RNG(object): 
29 -    def __init__(self, file): 
30          self.file = file 
31   
32 -    def read(self, bytes): 
33          return self.file.read(bytes) 
34   
35 -    def close(self): 
36          return self.file.close() 
37   
38 -    def randomize(self): 
39          return 
40   
41 -def open_rng_device(device_path=None): 
42      """Open /dev/urandom and perform some sanity checks.""" 
43   
44      f = None 
45      g = None 
46   
47      if device_path is None: 
48          device_path = "/dev/urandom" 
49   
50      try: 
51          # Try to open /dev/urandom now so that paramiko will be able to access 
52          # it even if os.chroot() is invoked later. 
53          try: 
54              f = open(device_path, "rb", 0) 
55          except EnvironmentError: 
56              raise error("Unable to open /dev/urandom") 
57   
58          # Open a second file descriptor for sanity checking later. 
59          try: 
60              g = open(device_path, "rb", 0) 
61          except EnvironmentError: 
62              raise error("Unable to open /dev/urandom") 
63   
64          # Check that /dev/urandom is a character special device, not a regular file. 
65          st = os.fstat(f.fileno())   # f 
66          if stat.S_ISREG(st.st_mode) or not stat.S_ISCHR(st.st_mode): 
67              raise error("/dev/urandom is not a character special device") 
68   
69          st = os.fstat(g.fileno())   # g 
70          if stat.S_ISREG(st.st_mode) or not stat.S_ISCHR(st.st_mode): 
71              raise error("/dev/urandom is not a character special device") 
72   
73          # Check that /dev/urandom always returns the number of bytes requested 
74          x = f.read(20) 
75          y = g.read(20) 
76          if len(x) != 20 or len(y) != 20: 
77              raise error("Error reading from /dev/urandom: input truncated") 
78   
79          # Check that different reads return different data 
80          if x == y: 
81              raise error("/dev/urandom is broken; returning identical data: %r == %r" % (x, y)) 
82   
83          # Close the duplicate file object 
84          g.close() 
85   
86          # Return the first file object 
87          return _RNG(f) 
88   
89      except error: 
90          if f is not None: 
91              f.close() 
92          if g is not None: 
93              g.close() 
94          raise 
95   
96  # vim:set ts=4 sw=4 sts=4 expandtab: 
97