Comodo防火墙SSDT钩子多个本地拒绝服务漏洞

BUGTRAQ ID: 28742
CVE(CAN) ID: CVE-2008-1736

Comodo是一款功能强大的个人防火墙。

Comodo防火墙的NtDeleteFile、NtCreateFile和NtSetThreadContext函数没有正确地验证参数，本地攻击者可能利用此漏洞导致防火墙不可用。

NtDeleteFile只接收了一个参数，也就是指向OBJECT_ATTRIBUTES结构的指针，这些属性会包含ObjectName和SECURITY_DESCRIPTOR。例如，以下是Comodo在NtDeleteFile所设置的钩子：

/-----------

NTDeleteFile (POBJECT_ATTRIBUTES ObjectAttributes)

.text:0001ACB0 push 1Ch
.text:0001ACB2 push offset stru_1E3F0
.text:0001ACB7 call __SEH_prolog
.text:0001ACBC xor ebx, ebx
.text:0001ACBE inc ebx
.text:0001ACBF mov [ebp+var_1C], ebx
.text:0001ACC2 xor esi, esi
.text:0001ACC4 mov [ebp+var_24], esi
.text:0001ACC7 mov [ebp+var_20], ebx
.text:0001ACCA mov [ebp+var_28], esi
.text:0001ACCD mov [ebp+ms_exc.disabled], esi
.text:0001ACD0 call ds:ExGetPreviousMode
.text:0001ACD6 mov edi, [ebp+ObjectAttributes]

• -----------/

这里执行了很多ProbeForRead检查判断结构指针是否有效（EDI仍有指向OBJECT_ATTRIBUTES结构的指针）：

/-----------

…
.text:0001AD25 push edi ; ObjectAttributes
.text:0001AD26 call sub_1A692 ; Here it passes the
OBJECT_ATTRIBUTES structure pointer to the next function.

sub_1A692
.text:0001A692 push 28h
.text:0001A694 push offset stru_1E3C0
.text:0001A699 call __SEH_prolog
.text:0001A69E xor edi, edi
…
.text:0001A6B3 mov [ebp+ms_exc.disabled], edi
.text:0001A6B6 push 72747052h ; Tag
.text:0001A6BB mov ebx, 400h
.text:0001A6C0 push ebx ; NumberOfBytes
.text:0001A6C1 push 1 ; PoolType
.text:0001A6C3 call ds:ExAllocatePoolWithTag ; Allocates memory to
hold the data retrieved by ZwQueryObject
.text:0001A6C9 mov esi, eax
.text:0001A6CB mov [ebp+var_28], esi
.text:0001A6CE cmp esi, edi
.text:0001A6D0 jz short loc_1A74F

.text:0001A6D2 mov edi, [ebp+ObjectAttributes]
.text:0001A6D5 mov eax, [edi+OBJECT_ATTRIBUTES.RootDirectory] ;
Here, the code retrieves the RootDirectory’s field value from the
structure, controled by us.
.text:0001A6D8 test eax, eax
.text:0001A6DA jz short loc_1A71B

.text:0001A6DC push 0 ; ReturnLength
.text:0001A6DE push ebx ; ObjectInformationLength
.text:0001A6DF push esi ; ObjectInformation
; buffer where ZwQueryObject will put the object information

.text:0001A6E0 push 1 ; ObjectInformationClass
; Specifies an OBJECT_INFORMATION_CLASS value that determines the type
; of information returned in the ObjectInformation buffer. It’s using
; an undocumented type (OBJECT_NAME_INFORMATION) which returns an
UNICODE_STRING structure
.text:0001A6E2 push eax ; ObjectHandle
; Now, the user-controlled handle 'll be used here to identify the
object by ZwQueryObject,
.text:0001A6E3 call ds:ZwQueryObject
.text:0001A6E9 mov [ebp+var_20], eax
.text:0001A6EC test eax, eax
.text:0001A6EE jl short loc_1A746

• -----------/

代码没有正确地验证ZwQueryObject所接收到的数据，攻击者可以通过各种句柄调用函数以获得空结构，导致在代码试图引用Buffer字段时系统出现崩溃。

/-----------

.text:0001A6F0 movzx eax, [esi+UNICODE_STRING.Length]
.text:0001A6F3 shr eax, 1
.text:0001A6F5 mov ecx, [esi+UNICODE_STRING.Buffer]
.text:0001A6F8 movzx eax, word ptr [ecx+eax*2-2] ; Here is the problem
.text:0001A6FD mov [ebp+var_30], eax
.text:0001A700 cmp ax, 5Ch
.text:0001A704 jz short loc_1A725

• -----------/

Comodo Firewall Pro 2.4.18.184
Comodo

目前厂商已经发布了升级补丁以修复这个安全问题，请到厂商的主页下载：

<a href=“http://www.personalfirewall.comodo.com/download_firewall.html” target=“_blank”>http://www.personalfirewall.comodo.com/download_firewall.html</a>