Windows处理驱动Path流程

标题：Windows处理驱动Path流程
作者：boywhp
时间：2011-08-31 15:50:13
链接：http://bbs.pediy.com/showthread.php?t=139566

昨天写了一个类似SC查询驱动服务的信息的程序，发现获取到的路径ImagePath是\??\c:\xxxxx，导致我用CreateFile什么的函数，居然失败！就比较好奇windows是怎么处理驱动服务一类的路径处理。我知道windows是在注册表中记录的启动服务信息，直接用注册表打开查看如下：

注意其中的ImagePath，我发现大致有好几种情况：
1、  无ImagePath项
2、  system32\xxxxxxxx
3、  \??\c:\xxxxxx
4、  %SystemRoot%xxxxxx
我想了解的是windows驱动服务是怎么处理这玩意的，既然是驱动最终会调用NtLoadDriver函数
NTSTATUS NtLoadDriver ( __in PUNICODE_STRING DriverServiceName )
直接Windbg启动调试 bp NtLoadDriver

fa06fa2c fa06fa38 80821a99 nt!NtLoadDriver+0x143
fa06fa2c fa06fa38 80821a99 nt!KiFastCallEntry+0xf8
fa06fa2c 815d5828 815b08e8 nt!ZwLoadDriver+0x11
817c7030 815d5770 fa06fab8 NDIS!ndisPnPDispatch+0x3ad

哦，NDIS不错哦，还可以加载驱动，呵呵，相关兴趣的可以IDA研究下，下面是我发现的一些非常规驱动加载列表[2003 server]：

1 "\Registry\Machine\System\CurrentControlSet\Services\Gpc"
fa01fa20 fa01fa3c 80821a99 nt!NtLoadDriver
fa01fa20 fa01fa3c 80821a99 nt!KiFastCallEntry+0xf8
fa01fa20 8142e000 8089547a nt!ZwLoadDriver+0x11
f96454b8 8142e000 8089547a ipsec!GpcInitialize+0x7f
00000000 8081dceb 815142f0 ipsec!IPSecGpcInitialize+0x35
815142f0 e12a75dc 00000000 ipsec!IPSecGeneralInit+0x168
815142f0 81430000 e144aa30 ipsec!DriverEntry+0x104
000000ec 00000001 00000000 nt!IopLoadDriver+0x689
00000000 00043000 00000000 nt!IopInitializeSystemDrivers+0x16d
00000000 00000000 8179d740 nt!IoInitSystem+0x6ad
80087000 fa01fddc 80905b5b nt!Phase1InitializationDiscard+0x9cf
80087000 00000000 00000000 nt!Phase1Initialization+0xd
808c9f21 80087000 00000000 nt!PspSystemThreadStartup+0x2e
00000000 00000000 00000000 nt!KiThreadStartup+0x16

2 "\Registry\Machine\System\CurrentControlSet\Services\WANARP"
f9948bdc f9948bf4 80821a99 nt!NtLoadDriver
f9948bdc f9948bf4 80821a99 nt!KiFastCallEntry+0xf8
f9948bdc 00000000 81503dd0 nt!ZwLoadDriver+0x11
f9948c8c f9948c1c 8160d2dc tcpip!IPBindAdapter+0xf2
80a719b0 80a71988 f99a7534 NDIS!ndisInitializeBinding+0x189
f99a53bc 00000000 81503e60 NDIS!ndisCheckAdapterBindings+0xd9
81503dd0 00000000 81289db0 NDIS!ndisCheckProtocolBindings+0xd2
81503e50 00000000 00000000 NDIS!ndisWorkerThread+0x74
f99a8a41 81503e50 00000000 nt!PspSystemThreadStartup+0x2e
00000000 00000000 00000000 nt!KiThreadStartup+0x16

3 "\Registry\Machine\System\CurrentControlSet\Services\Cdfs"
f9948974 f994897c 80821a99 nt!NtLoadDriver
f9948974 f994897c 80821a99 nt!KiFastCallEntry+0xf8
f9948974 81751200 814861d0 nt!ZwLoadDriver+0x11
c000010e f9f0439e 814861d0 Fs_Rec!FsRecLoadFileSystem+0x4f
814861d0 81751200 8163bad8 Fs_Rec!CdfsRecFsControl+0x29
814861d0 81751200 814861d0 Fs_Rec!FsRecFsControl+0x75
81668680 808a73a0 815fa8f8 nt!IofCallDriver+0x45
814861d0 80a71908 815fa8f8 nt!IopLoadFileSystemDriver+0x62
c000019c 8163cd00 00000000 nt!IopMountVolume+0x2cc
8163cd20 815fa800 f9948b9c nt!IopCheckVpbMounted+0x54
815fa8f8 00000000 81533c60 nt!IopParseDevice+0x3d4
00000000 f9948c18 00000040 nt!ObpLookupObjectName+0x5b0
00000000 00000000 0007ff01 nt!ObOpenObjectByName+0xea
0015fe0c 00100180 0015fdd0 nt!IopCreateFile+0x447
0015fe0c 00100180 0015fdd0 nt!IoCreateFile+0xa3
0015fe0c 00100180 0015fdd0 nt!NtOpenFile+0x27
0015fe0c 00100180 0015fdd0 nt!KiFastCallEntry+0xf8
WARNING: Stack unwind information not available. Following frames may be wrong.
7c959e17 4858d650 7c958270 ntdll+0x285fe
00000000 7c94a469 00000000 0x48584401
ffffffff 4858afe8 48582f48 0x485894ec

4 "\Registry\Machine\System\CurrentControlSet\Services\tdtcp"
f7ed2b4c f7ed2b6c 80821a99 nt!NtLoadDriver
f7ed2b4c f7ed2b6c 80821a99 nt!KiFastCallEntry+0xf8
f7ed2b4c f9db12e8 8118bf78 nt!ZwLoadDriver+0x11
8127b178 f7ed2b88 81182258 termdd!_IcaLoadSdWorker+0x11b
8118225c f7ed2ba8 811c29e8 termdd!_IcaLoadSd+0x8b
811c29e8 81182258 8122cf68 termdd!_IcaPushStack+0x7b
811c29e8 8122cf68 8122cfd8 termdd!IcaDeviceControlStack+0x11f
8122cf68 8122cfd8 8122cf68 termdd!IcaDeviceControl+0x4e
81617f10 8122cf68 8151db90 termdd!IcaDispatch+0x12a
8122cfd8 ffa7ed10 8122cf68 nt!IofCallDriver+0x45
81617f10 8122cf68 ffa7ed10 nt!IopSynchronousServiceTail+0x10b
00000208 00000000 00000000 nt!IopXxxControlFile+0x60f
00000208 00000000 00000000 nt!NtDeviceIoControlFile+0x2a
00000208 00000000 00000000 nt!KiFastCallEntry+0xf8
WARNING: Stack unwind information not available. Following frames may be wrong.
00000208 0038002b 0250fa18 ntdll+0x285fe
000a0498 0038002b 0250fa18 0x74cd166f
000a0498 0038002b 0250fa18 0x74cd16b4
000be2f0 000a0498 0038002b 0x764a0759
000a0498 0038002b 0250fa18 0x74cd16fe
00000000 00000000 808466ca 0x74cd17cf
以及"\Registry\Machine\System\CurrentControlSet\Services\rdpwd"

然后是NtLoadDriver -> IopLoadUnloadDriver -> IopLoadDriver->IopBuildFullDriverPath

NTSTATUS
IopBuildFullDriverPath(
    IN PUNICODE_STRING KeyName,
    IN HANDLE KeyHandle,
    OUT PUNICODE_STRING FullPath
    )
这里处理了下注册表路径，具体WRK代码如下

代码:

    status = IopGetRegistryValue( KeyHandle,
                                  L"ImagePath",
                                  &keyValueInformation);
    if (NT_SUCCESS(status) && keyValueInformation->DataLength) {
        nameLength = keyValueInformation->DataLength - sizeof(WCHAR);
        name = (PWCHAR)KEY_VALUE_DATA(keyValueInformation);
        if (name[0] != L'\\') {
            path = L"\\SystemRoot\\";
            pathLength = sizeof(L"\\SystemRoot\\") - sizeof(UNICODE_NULL);
        } else {
            path = NULL;
        }
        ext = NULL;
    } else {
        nameLength = KeyName->Length;
        name = KeyName->Buffer;
        pathLength = sizeof(L"\\SystemRoot\\System32\\Drivers\\") - sizeof(UNICODE_NULL);
        path = L"\\SystemRoot\\System32\\Drivers\\";
        extLength = sizeof(L".SYS") - sizeof(UNICODE_NULL);
        ext = L".SYS";
}

  1、如果没有ImagePath项目就在”\SystemRoot\System32\Drivers\” + BaseName.sys 找
  2、如何ImagePath = 是'\'开头，=ImagePath
        3、如果不是'\‘开头 path = “\SystemRoot\” + ImagePath

这里SystemRoot我比较好奇，想看看系统是怎么处理这个路径的，继续：
IopLoadDriver 会调用MmLoadSystemImage-> ZwOpenFile->NtOpenFile

bp NtOpenFile命中
kd> dt !_OBJECT_ATTRIBUTES fa06f734
nt!_OBJECT_ATTRIBUTES
   +0x000 Length           : 0x18
   +0x004 RootDirectory    : (null)
   +0x008 ObjectName       : 0xfa06f888 _UNICODE_STRING "\SystemRoot\System32\Drivers\NDProxy.SYS"
   +0x00c Attributes       : 0x240
   +0x010 SecurityDescriptor : (null)
   +0x014 SecurityQualityOfService : (null)
继续跟踪->IopCreateFile->ObOpenObjectByName->ObpLookupObjectName

代码:

ParseFromRoot:
if (DeviceMap != NULL) {
ObfDereferenceDeviceMap(DeviceMap);
DeviceMap = NULL;
}

if (!((ULONG_PTR)(ObjectName->Buffer) & (sizeof(ULONGLONG)-1))) {
//
//  Check if the object name is actually equal to the
//  global dos devices short name prefix "\??\"
//

if ((ObjectName->Length >= ObpDosDevicesShortName.Length)
                        &&
(*(PULONGLONG)(ObjectName->Buffer) == ObpDosDevicesShortNamePrefix.Alignment.QuadPart)) {
  XXXXXXXXXXXXXXXXXXXX
}

其ObpXxxx定义如下：

代码:

const ALIGNEDNAME ObpDosDevicesShortNamePrefix = { L'\\',L'?',L'?',L'\\' }; // L"\??\"
const ALIGNEDNAME ObpDosDevicesShortNameRoot = { L'\\',L'?',L'?',L'\0' }; // L"\??"
const UNICODE_STRING ObpDosDevicesShortName = {
    sizeof(ObpDosDevicesShortNamePrefix),
    sizeof(ObpDosDevicesShortNamePrefix),
    (PWSTR)&ObpDosDevicesShortNamePrefix
};

随便问一下if (!((ULONG_PTR)(ObjectName->Buffer) & (sizeof(ULONGLONG)-1)))是要求64字节对齐吗？
大致流程是：
如果是\??\开头的直接获取RootDirectory，否则需要解析root目录，通过下面函数
PVOID
ObpLookupDirectoryEntry (
    IN POBJECT_DIRECTORY Directory,
    IN PUNICODE_STRING Name,
    IN ULONG Attributes,
    IN BOOLEAN SearchShadow,
    OUT POBP_LOOKUP_CONTEXT LookupContext
)
bp ObpLookupDirectoryEntry命中：
kd> dd esp
fa06f3ec  80902d75 e1000700 fa06f410 00000240
kd> dt !_UNICODE_STRING fa06f410
nt!_UNICODE_STRING
"SystemRoot"
   +0x000 Length           : 0x14
   +0x002 MaximumLength    : 0xf8
   +0x004 Buffer           : 0xe12c4d62  "SystemRoot"
我们关心的SystemRoot出现了，大致看了下，居然就是计算了SystemRoot字符串的hash！！！然后估计就是查表，其hash算法为：

代码:

    HashIndex = 0;

    while (WcharLength--) {
        Wchar = *Buffer++;
        HashIndex += (HashIndex << 1) + (HashIndex >> 1);

        if (Wchar < 'a') {
            HashIndex += Wchar;
        } else if (Wchar > 'z') {
            HashIndex += RtlUpcaseUnicodeChar( (WCHAR)Wchar );
        } else {
            HashIndex += (Wchar - ('a'-'A'));
        }
    }

    HashValue = HashIndex;
    HashIndex %= NUMBER_HASH_BUCKETS;
#define NUMBER_HASH_BUCKETS 37

好像大致是一个hash目录表，首先简单的通过hash快速查找，对应的37个链表之1，然后遍历链表比较名称是否为SystemRoot。
在WRK中搜索"SystemRoot"，发现其在Initos.c的CreateSystemRootLink函数中被初始化创建符号链接

代码:

    //
    // Create the symbolic link to the root of the system directory.
    //

    RtlInitAnsiString( &linkString, INIT_SYSTEMROOT_LINKNAME );

    status = RtlAnsiStringToUnicodeString( &linkUnicodeString,
                                           &linkString,
                                           TRUE);
    InitializeObjectAttributes( &objectAttributes,
                                &linkUnicodeString,
                                OBJ_CASE_INSENSITIVE | OBJ_PERMANENT,
                                NULL,
                                SePublicDefaultUnrestrictedSd );
。。。。。。
    status = NtCreateSymbolicLinkObject( &linkHandle,
                                         SYMBOLIC_LINK_ALL_ACCESS,
                                         &objectAttributes,
                                         &deviceNameUnicodeString );

#define INIT_SYSTEMROOT_LINKNAME "\\SystemRoot"

至此，大致了解了这个路径的处理过程，至于我的问题应该可以很好的使用ZwOpenFile还处理，因为操作系统本身也是直接调用ZwOpenFile，或者直接把\??\过滤掉得了。