Bug 183069 - rkhunter says clean, but file sizes differ???
Summary: rkhunter says clean, but file sizes differ???
Alias: None
Product: Fedora
Classification: Fedora
Component: rkhunter
Version: 4
Hardware: i686
OS: Linux
Target Milestone: ---
Assignee: Greg Houlette
QA Contact: Fedora Extras Quality Assurance
Keywords: Security
: 183070 183071 183072 183073 (view as bug list)
Depends On:
TreeView+ depends on / blocked
Reported: 2006-02-26 00:12 UTC by james
Modified: 2007-11-30 22:11 UTC (History)
1 user (show)

Clone Of:
Last Closed: 2006-02-26 05:22:43 UTC

Attachments (Terms of Use)

Description james 2006-02-26 00:12:08 UTC
From Bugzilla Helper:
User-Agent: Opera/8.52 (X11; Linux i686; U; en)

Description of problem:
Hmm - rkhunter and chkrootkit say everything is clean, but most, not all, libraries and _binary_ files larger than 
about 4096 bytes have a larger file size, and different file contents, compared to files from the corresponding rpm 

For the "larger" files, 'strings /usr/bin/<somefile>' always gives a line '/Cx2' near the top of the output, and a 
repeated line '/lib/ld-linux.so.2' near the bottom of the output from 'strings', compared to the same file from the rpm 
package.  Also, the output from 'strings' from the larger files looks vaguely like upper half and lower half hunks are 
swapped, top to bottom, compared to the output for the same file from the rpm package.

Question: Is this something to do with the ext3 filesystem, or with the way rpm writes files to disk?  Or has this box 
maybe been rooted?  by some rootkit nobody knows anything about?

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.sudo rkhunter --checkall --rootdir <nfs-mounted other machine>
2.ls -l /usr/bin/<anything seemingly bigger than 4096 bytes>
3.rpm -vV <whatever>

Actual Results:  For 1 - says everything is clean
For 2 - gives a file size larger than what comes out of the rpm package.
For 3 - usually says everything is fine, but did notice that "/usr/bin/passwd" had the wrong size, unless rpm - a 
version of rpm clean from the rpm package - was run as root, in which case, rpm did not notice the size 

Expected Results:  One might expect rkhunter  to notice that the file sizes are all too large?
Or rpm should notice?  Or the rpm database has been buggered?

Additional info:

Comment 1 Dennis Gilmore 2006-02-26 04:35:37 UTC
*** Bug 183070 has been marked as a duplicate of this bug. ***

Comment 2 Dennis Gilmore 2006-02-26 04:36:29 UTC
*** Bug 183071 has been marked as a duplicate of this bug. ***

Comment 3 Dennis Gilmore 2006-02-26 04:37:25 UTC
*** Bug 183072 has been marked as a duplicate of this bug. ***

Comment 4 Dennis Gilmore 2006-02-26 04:38:39 UTC
*** Bug 183073 has been marked as a duplicate of this bug. ***

Comment 5 Dennis Gilmore 2006-02-26 04:41:15 UTC
this is most likely an issue with prelink.  to verify  run prelink -ua  and 
then double check  what they show then.  from man prelink  
prelink  is  a program which modifies ELF shared libraries and ELF dynamically 
linked binaries, so that the time which dynamic linker 
       needs for their relocation at startup significantly decreases and also 
due to  fewer  relocations  the  run-time  memory  consumption 
       decreases  too (especially number of unshareable pages). Such 
prelinking information is only used if all its dependant libraries have 
       not changed since prelinking, otherwise programs are relocated 
       prelink first collects ELF binaries which should be prelinked and all 
the ELF shared libraries they depend  on.  Then  it  assigns  a 
       unique  virtual  address  space  slot  for each library and relinks the 
shared library to that base address.  When the dynamic linker 
       attempts to load such a library, unless that virtual address space slot 
is already occupied, it will map  it  into  the  given  slot. 
       After  this  is done, prelink with the help of dynamic linker resolves 
all relocations in the binary or library against its dependant 
       libraries and stores the relocations into the ELF object.  It also 
stores a list of  all  dependant  libraries  together  with  their 
       checksums  into  the binary or library.  For binaries, it also computes 
a list of conflicts (relocations which resolve differently in 
       the binaryâs symbol search scope than in the smaller search scope in 
which the dependant library was resolved) and stores it  into  a 
       special ELF section. 
       At  runtime,  the  dynamic linker first checks whether all dependant 
libraries were successfully mapped into their designated address 
       space slots and whether they have not changed since the prelinking was 
done.  If all checks are successful, the dynamic  linker  just 
       replays  the  list  of conflicts (which is usually significantly 
shorter than total number of relocations) instead of relocating each 

Comment 6 james 2006-02-26 05:22:43 UTC
Sorry about the duplicates.  Opera and Bugzilla do not play nicely together.  It
was running on automatic before I stopped it.

> this is most likely an issue with prelink.  to verify  run prelink -ua

Yes, that seems to solve the mystery.  Live and learn... and no root kit.


BTW, do you think "rpm -V" should say something about the "prelink" change to
the files?  It seems odd otherwise.

Comment 7 Michael Schwendt 2006-02-26 08:02:35 UTC
"rpm -V" is aware of prelinking.

Comment 8 james 2006-02-26 15:30:12 UTC
Reading from the rpm man page, there is no mention of "prelink", or that a file
size has been changed by prelink:

The format of the output is a string of 8 characters, a possible attribute marker:
       c %config configuration file.
       d %doc documentation file.
       g %ghost file (i.e. the file contents are not included in the package
       l %license license file.
       r %readme readme file.

Otherwise, the (mnemonically emBoldened) character denotes failure of the
corresponding --verify test:

       S file Size differs
       M Mode differs (includes permissions and file type)
       5 MD5 sum differs
       D Device major/minor number mismatch
       L readLink(2) path mismatch
       U User ownership differs
       G Group ownership differs
       T mTime differs

The rpm -V command could be enhanced with an additional "attribute marker":

 p %prelink this file has been modified by prelink. The file size and md5 sum
may differ from the original file.

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