Re: shadow file
From: Walter Roberson (roberson_at_ibd.nrc-cnrc.gc.ca)
Date: 12/08/04
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Date: 8 Dec 2004 17:11:22 GMT
In article <cp6ki9$je4$05$1@news.t-online.com>, Frank <lol@privacy.net> wrote:
:i'd like to see if it's possible to decode this file....
:root:$1$BZftq3sP$xEeZmr2fGEnKjVAxzj/o51:12747:0:99999:7:::
That looks like a standard /etc/shadow line in an OS that allows
the glibc extensions to encrypted passwords. According to
http://unixhelp.ed.ac.uk/CGI/man-cgi?crypt+3
GNU EXTENSION
The glibc2 version of this function has the following additional fea-
tures. If salt is a character string starting with the three charac-
ters "$1$" followed by at most eight characters, and optionally termi-
nated by "$", then instead of using the DES machine, the glibc crypt
function uses an MD5-based algorithm, and outputs up to 34 bytes,
namely "$1$<string>$", where "<string>" stands for the up to 8 charac-
ters following "$1$" in the salt, followed by 22 bytes chosen from the
set [a-zA-Z0-9./]. The entire key is significant here (instead of only
the first 8 bytes).
Thus, in order to decode the password, one would have to find a
password whose MD5 was represented in base64 as xEeZmr2fGEnKjVAxzj/o51 .
MD5 is a 128 bit hash, so brute force would require an
average of 2^127 operations to find a match. That's a lot of
computation.
There are services which are generating pretty much all 8 bit
lowercase + digit plaintexts and using MD5 to encrypt them and
saving the result, but these services don't work with the "salted"
MD5 of shadow password files.
-- *We* are now the times. -- Wim Wenders (WoD)
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