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<title>8.4 crypt -- Function to check Unix passwords
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<H1><A NAME=
"SECTION0010400000000000000000">
8.4 <tt class=
"module">crypt
</tt> --
Function to check
<span class=
"Unix">Unix
</span> passwords
</A>
<A NAME=
"module-crypt"></A>
<p class=
"availability">Availability:
<span
class=
"platform">Unix
</span>.
</p>
This module implements an interface to the
<span class=
"manpage"><i>crypt
</i>(
3)
</span><a id='l2h-
2984' xml:id='l2h-
2984'
></a> routine, which is a one-way hash
function based upon a modified DES
<a id='l2h-
2982' xml:id='l2h-
2982'
></a> algorithm; see
the
<span class=
"Unix">Unix
</span> man page for further details. Possible uses include
allowing Python scripts to accept typed passwords from the user, or
attempting to crack
<span class=
"Unix">Unix
</span> passwords with a dictionary.
Notice that the behavior of this module depends on the actual implementation
of the
<span class=
"manpage"><i>crypt
</i>(
3)
</span><a id='l2h-
2985' xml:id='l2h-
2985'
></a> routine in the running system.
Therefore, any extensions available on the current implementation will also
be available on this module.
<dl><dt><table cellpadding=
"0" cellspacing=
"0"><tr valign=
"baseline">
<td><nobr><b><tt id='l2h-
2983' xml:id='l2h-
2983'
class=
"function">crypt
</tt></b>(
</nobr></td>
<td><var>word, salt
</var>)
</td></tr></table></dt>
<var>word
</var> will usually be a user's password as typed at a prompt or
in a graphical interface.
<var>salt
</var> is usually a random
two-character string which will be used to perturb the DES algorithm
in one of
4096 ways. The characters in
<var>salt
</var> must be in the
set
<tt class=
"regexp">[./a-zA-Z0-
9]
</tt>. Returns the hashed password as a
string, which will be composed of characters from the same alphabet
as the salt (the first two characters represent the salt itself).
Since a few
<span class=
"manpage"><i>crypt
</i>(
3)
</span><a id='l2h-
2986' xml:id='l2h-
2986'
></a> extensions allow different
values, with different sizes in the
<var>salt
</var>, it is recommended to use
the full crypted password as salt when checking for a password.
A simple example illustrating typical use:
<div class=
"verbatim"><pre>
import crypt, getpass, pwd
username = raw_input('Python login:')
cryptedpasswd = pwd.getpwnam(username)[
1]
if cryptedpasswd == 'x' or cryptedpasswd == '*':
raise
"Sorry, currently no support for shadow passwords"
cleartext = getpass.getpass()
return crypt.crypt(cleartext, cryptedpasswd) == cryptedpasswd
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<span class=
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2.4.2, documentation updated on
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2005.
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