wchen-r7's assessment of CVE-2017-18044 - Commvault Communications Service execCmd Vulnerability

Attacker Value

Unknown

CVE-2017-18044 - Commvault Communications Service execCmd Vulnerability

Description

A Command Injection issue was discovered in ContentStore/Base/CVDataPipe.dll in Commvault before v11 SP6. A certain message parsing function inside the Commvault service does not properly validate the input of an incoming string before passing it to CreateProcess. As a result, a specially crafted message can inject commands that will be executed on the target operating system. Exploitation of this vulnerability does not require authentication and can lead to SYSTEM level privilege on any system running the cvd daemon. This is a different vulnerability than CVE-2017-3195.

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wchen-r7 (173)

September 12, 2019 6:08pm UTC (5 years ago)•Edited 4 years ago

Technical Analysis

Introduction

Commvault is a data protection and information management software; an enterprise-level data
platform that contains modules to back up, restore, archive, replicate, and search data.

According to public documentation, the data is protected by installing agent software on the
physical or virtual hosts, which use the OS or application native APIs to protect data in a
consistent state. Production data is processed by the agent on client computers and backuped
up through a data manager (the MediaAgent) to disk, tape, or cloud storage. All data
management activity in the environment is tracked by a centralized server (called CommServe),
and can be managed by administrators through a central user interface. End users can access
protected data using web browsers or mobile devices.

One of the base services of Commvault is vulnerable to a remote command injection attack,
specifically the cvd service. It was a Metasploit submission by @rwincey as PR #9340.

Vulnerable Application

According to the public advisory, Commvault v11 SP5 or prior are vulnerable to this
vulnerability.

The specific vulnerable version I tested was 11.0.80.0, and the software was obtained from
the Metasploit contributor @rwincey. The software is available from our Google Drive at:

Vulnerable Apps –> Commvault –> Commvault_R80_SP5_22September16.exe.

The version of the vulnerable DLL is:

    Image path: C:\Program Files\Commvault\ContentStore\Base\CVDataPipe.dll
    Image name: CVDataPipe.dll
    Timestamp:        Wed Dec 21 11:59:21 2016 (585AC2F9)
    CheckSum:         002ED404
    ImageSize:        002F0000
    File version:     11.80.50.60437
    Product version:  11.0.0.0
    File flags:       1 (Mask 3F) Debug
    File OS:          40004 NT Win32
    File type:        1.0 App
    File date:        00000000.00000000
    Translations:     0409.04b0
    CompanyName:      Commvault
    ProductName:      Commvault
    InternalName:     CVDataPipe
    OriginalFilename: CVDataPipe.dll
    ProductVersion:   11.0.0.0
    FileVersion:      11.80.50.60437
    PrivateBuild:
    SpecialBuild:
    FileDescription:
    LegalCopyright:   Copyright (c) 2000-2016
    LegalTrademarks:
    Comments:

Root Cause Analysis

Based on the information we have from the pull request, the vulnerability is a command injection, so
that’s where we begin reversing.

Usually, there are two ways to execute a command in a C/C++ application, one of them is WinExec(),
and the other one is CreateProcess():

BOOL WINAPI CreateProcess(
  _In_opt_    LPCTSTR               lpApplicationName,
  _Inout_opt_ LPTSTR                lpCommandLine,
  _In_opt_    LPSECURITY_ATTRIBUTES lpProcessAttributes,
  _In_opt_    LPSECURITY_ATTRIBUTES lpThreadAttributes,
  _In_        BOOL                  bInheritHandles,
  _In_        DWORD                 dwCreationFlags,
  _In_opt_    LPVOID                lpEnvironment,
  _In_opt_    LPCTSTR               lpCurrentDirectory,
  _In_        LPSTARTUPINFO         lpStartupInfo,
  _Out_       LPPROCESS_INFORMATION lpProcessInformation
);

Since CreateProcess() is meant to replace WinExec() according to Microsoft, we can create a
break point there fist in our debugger (WinDBG), and we hit it:

0:044> g
Breakpoint 3 hit
kernel32!CreateProcessA:
00000000`76fe8730 4c8bdc          mov     r11,rsp

Looking at the callstack of this kernel32!CreateProcessA, we already have a pretty good idea
locating the vulnerability:

0:044> k
Child-SP          RetAddr           Call Site
00000000`11a36b78 000007fe`f378a40f kernel32!CreateProcessA
00000000`11a36b80 000007fe`f377714e CVDataPipe!execCmd+0x7af
00000000`11a3f340 000007fe`f3777a69 CVDataPipe!CVDMessageHandler+0x78e
00000000`11a3fbd0 000007fe`f9cdc58d CVDataPipe!CVDMessageHandler+0x10a9
00000000`11a3fd40 000007fe`f9cdc1b1 CvBasicLib!CvThreadPool::th_defaultWorkerObj+0x3cd
00000000`11a3fe40 000007fe`f9cd2073 CvBasicLib!CvThreadPool::th_defaultWorker+0x51
00000000`11a3fe90 000007fe`f9a84f7f CvBasicLib!CvThread::~CvThread+0x63
00000000`11a3fee0 000007fe`f9a85126 MSVCR120!_callthreadstartex+0x17 [f:\dd\vctools\crt\crtw32\startup\threadex.c @ 376]
00000000`11a3ff10 00000000`76f6f56d MSVCR120!_threadstartex+0x102 [f:\dd\vctools\crt\crtw32\startup\threadex.c @ 354]
00000000`11a3ff40 00000000`770a3281 kernel32!BaseThreadInitThunk+0xd
00000000`11a3ff70 00000000`00000000 ntdll!RtlUserThreadStart+0x1d

There are two things that are interesting. One of them is CVDataPipe!CVDMessageHandler, and the
other one is CVDataPipe!execCmd.

The Metasploit exploit specifically sends a code of ```9h```, which is the message type for ```execCmd```:

.text:0000000180147103 loc_180147103: ; CODE XREF: CVDMessageHandler(int,selectStruct_t *,CQiSocket,void *):loc_180146D78j
.text:0000000180147103 lea rax, [rsp+888h+var_220] ; jumptable 0000000180146D78 case 9
.text:000000018014710B mov [rsp+888h+var_600], rax
.text:0000000180147113 mov rdx, [rsp+888h+sock]
.text:000000018014711B mov rcx, [rsp+888h+var_600]
.text:0000000180147123 call cs:??0CQiSocket@@QEAA@AEBV0@@Z ; CQiSocket::CQiSocket(CQiSocket const &)
.text:0000000180147129 mov [rsp+888h+var_5F0], rax
.text:0000000180147131 mov r8, [rsp+888h+arg_18]
.text:0000000180147139 mov rdx, [rsp+888h+var_5F0]
.text:0000000180147141 mov rcx, [rsp+888h+structSelect]
.text:0000000180147149 call ?execCmd@@YAXPEAUselectStruct_t@@VCQiSocket@@PEAX@Z ; execCmd(selectStruct_t *,CQiSocket,void *)


If we take a closer look at the ```execCmd``` function, we can tell the purpose of it is for processes such as:

* ifind (For restoring purposes)
* BackupShadow.exe (For archiving)
* Pub (Map file)
* createIndex (A Commvault process for building index)

.text:0000000180159F1B loc_180159F1B: ; CODE XREF: execCmd(selectStruct_t *,CQiSocket,void *)+261j
.text:0000000180159F1B ; DATA XREF: .rdata:0000000180286258o
.text:0000000180159F1B lea rdx, aIfind ; “ifind”
.text:0000000180159F22 lea rcx, [rsp+87B8h+ApplicationName] ; Str
.text:0000000180159F2A call cs:strstr
.text:0000000180159F30 test rax, rax
.text:0000000180159F33 jnz short loc_180159F6D
.text:0000000180159F35 lea rdx, aBackupshadow_e ; “BackupShadow.exe”
.text:0000000180159F3C lea rcx, [rsp+87B8h+ApplicationName] ; Str
.text:0000000180159F44 call cs:strstr
.text:0000000180159F4A test rax, rax
.text:0000000180159F4D jnz short loc_180159F6D
.text:0000000180159F4F lea rdx, aPub ; “Pub”
.text:0000000180159F56 lea rcx, [rsp+87B8h+ApplicationName] ; Str
.text:0000000180159F5E call cs:strstr
…
.text:000000018015A0BA loc_18015A0BA: ; CODE XREF: execCmd(selectStruct_t *,CQiSocket,void *)+307j
.text:000000018015A0BA lea rdx, aCreateindex ; “createIndex”
.text:000000018015A0C1 lea rcx, [rsp+87B8h+ApplicationName] ; Str
.text:000000018015A0C9 call cs:strstr
.text:000000018015A0CF test rax, rax
.text:000000018015A0D2 jz loc_18015A220


However, if you don't call one of these processes, the ```exeCmd``` will assume you want to run your
custom process, and pass it to ```CreateProcess``` anyway:

.text:000000018015A361 .text:000000018015A361 .text:000000018015A367 .text:000000018015A36F .text:000000018015A377 .text:000000018015A37A .text:000000018015A37C .text:000000018015A381 .text:000000018015A383 .text:000000018015A38E .text:000000018015A396 .text:000000018015A399 .text:000000018015A39B .text:000000018015A3A0 .text:000000018015A3A2 .text:000000018015A3AD .text:000000018015A3AF .text:000000018015A3B7 .text:000000018015A3BF .text:000000018015A3C4 .text:000000018015A3CC .text:000000018015A3D1 .text:000000018015A3DA .text:000000018015A3E3 .text:000000018015A3EB .text:000000018015A3F3 .text:000000018015A3F6 .text:000000018015A3F9 .text:000000018015A401 .text:000000018015A409 ”` loc_18015A361: ; CODE XREF: execCmd(selectStruct_t *,CQiSocket,void *)+675j
call cs:GetEnvironmentStrings
mov [rsp+87B8h+var_86A8], rax
lea rax, [rsp+87B8h+StartupInfo]
mov rdi, rax
xor eax, eax
mov ecx, 68h
rep stosb
mov [rsp+87B8h+StartupInfo.cb], 68h
lea rax, [rsp+87B8h+ProcessInformation]
mov rdi, rax
xor eax, eax
mov ecx, 18h
rep stosb
mov [rsp+87B8h+StartupInfo.dwFlags], 1
xor eax, eax
mov [rsp+87B8h+StartupInfo.wShowWindow], ax
lea rax, [rsp+87B8h+ProcessInformation]
mov [rsp+87B8h+lpProcessInformation], rax ; lpProcessInformation
lea rax, [rsp+87B8h+StartupInfo]
mov [rsp+87B8h+lpStartupInfo], rax ; lpStartupInfo
mov [rsp+87B8h+lpCurrentDirectory], 0 ; lpCurrentDirectory
mov [rsp+87B8h+lpEnvironment], 0 ; lpEnvironment
mov [rsp+87B8h+dwCreationFlags], 10h ; dwCreationFlags
mov [rsp+87B8h+bInheritHandles], 0 ; bInheritHandles
xor r9d, r9d ; lpThreadAttributes
xor r8d, r8d ; lpProcessAttributes
lea rdx, [rsp+87B8h+CommandLine] ; lpCommandLine
lea rcx, [rsp+87B8h+ApplicationName] ; lpApplicationName
call cs:CreateProcessA

It is unclear whether allowing an arbitrary custom process is intentional or not, it is unsafe
anyway considering the cvd process binds to 0.0.0.0, so anybody can access to it.

CVSS V3 Severity and Metrics

Data provided by the National Vulnerability Database (NVD)

Base Score:

None

Impact Score:

Unknown

Exploitability Score:

Unknown

Vector:

Unknown

Attack Vector (AV):

Unknown

Attack Complexity (AC):

Unknown

Privileges Required (PR):

Unknown

User Interaction (UI):

Unknown

Scope (S):

Unknown

Confidentiality (C):

Unknown

Integrity (I):

Unknown

Availability (A):

Unknown

Vendors

commvault

Products

commvault,
commvault 11.0

Metasploit Modules

exploit/windows/misc/commvault_cmd_exec (https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/misc/commvault_cmd_exec.rb)

References

Rapid7

Unknown

CVE-2017-18044 - Commvault Communications Service execCmd Vulnerability

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CVE-2017-18044 - Commvault Communications Service execCmd Vulnerability

Description

Add Assessment

Technical Analysis

Introduction

Vulnerable Application

Root Cause Analysis

CVSS V3 Severity and Metrics

General Information

Vendors

Products

Metasploit Modules

References

Canonical

Exploit

Miscellaneous

Additional Info

Technical Analysis

Unknown

CVE-2017-18044 - Commvault Communications Service execCmd Vulnerability

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Unknown

CVE-2017-18044 - Commvault Communications Service execCmd Vulnerability

Description

Add Assessment

Technical Analysis

Introduction

Vulnerable Application

Root Cause Analysis

CVSS V3 Severity and Metrics

General Information

Vendors

Products

Metasploit Modules

References

Canonical

Exploit

Miscellaneous

Additional Info

Technical Analysis

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