检测并禁用隐藏服务
隐藏服务的概念是由hxdef 和rootkit这些后门工具提出的。这些后门工具通过挂钩系统本地调用来隐藏自己，原本通过调用Windows API调用查看系统服务的企图都是徒劳的。所以这时的系统是不可靠的，不值得信任的。目前针对查找隐藏服务的工具已经有很多，比如IceSword，knlsc，FHS等等。虽然这些软件都是免费的，但是它们到目前为止都不是开源，所以将自己的实现版本展示出来，正如knlsc的作者所说的那样，这是一个简单的小程序。
Knlsc是通过将%SystemRoot%/System32/Config/System这个Hive文件转储出来，提取出ControlSet001/Services的子项再与RegEnumKeyEx的输出结果进行比对，发现若是在RegEnumKeyEx的输出结果中没有的子项就可以认为是一个隐藏的服务。当然knlsc还认为隐藏服务必须同时拥有ImagePath，Start，Type三个键值。据说knlsc运行时还将从资源段中放出一个驱动程序，但是估计这个驱动是假的。将knlsc托壳后用VC从资源段中导出的文件是一个没有EntryPoint但有MZ标志的驱动，没有办法进行反汇编。或许作者使用了SMC技术，放出资源文件后在进行修改，在执行文件中也有NtLoadDriver的调用片段，但是同一作者的knlps中的资源驱动却未作任何的处理。要实现检测隐藏服务的功能其实没有必要使用驱动程序，即使可以验证knlsc驱动的真实性。直接对Hive文件的转储也不是必须的，虽然这只要通过修改Gary Nebbett的示例代码就可做到。
Hive文件的转储可以通过RegSaveKey函数来进行，rootkitrevealer就是使用这个API的扩充函数RegSaveKeyEx工作的，至少到目前为止还没有挂钩这类函数的后门，但是世上没有永远的安全，在理论上是可行的，可能不得不对该函数的输出文件进行处理，这将在一定程度上影响该函数的执行时间。使用该函数时还必须赋予调用进程以SE_BACKUP_NAME权限。
在实现中将“HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services"的子项都转储为Hive格式文件（使用DumpServiceInfo函数），存放在C:\tmp.hive，在Ｃ盘下不可有同名文件，否则会发生Dump错误。现在的问题是如何对Hive格式文件进行处理，在这一点上必须感谢Petter Nordahl-Hagen所写的NT Registry Hive access library，它是The Offline NT Password Editor的一部分。本人的实现很大程度上就是参照他的程序，然而这个库工作在Linux环境，但是它向VC编译器移植的工作量是极少的，只需稍加修改。
１．将 #include <unistd.h> 去掉
２．将程序中三处的
#define D_OFFS(o) ( (void *)&(key->o)-(void *)hdesc->buffer-vofs )
改为
#define D_OFFS(o) ( (int *)&(key->o)-(int *)hdesc->buffer-vofs )
因为在ＶＣ中无法打印void * 类型，只得改为int * 。
３．将程序中唯一的一处使用snprintf函数该为_snprintf，即
snprintf(path,maxlen,"(...)%s",tmp);改为
_snprintf(ptth,maxlen,”(…)%s”,tmp);
４．添加两个ＶＣ不支持的函数来使编译通过
void bzero(void *s,int n)
{
memset(s,0,n);
}
int strncasecmp(const char *s1, const char *s2, size_t n)
{
return _stricmp(s1,s2);
}
为了表示对Petter Nordahl-Hagen的尊重，我不再修改他的库文件ntreg.c和ntreg.h（除了以上移植的需要），而是将所有需要重写和添加的函数放到KHS.C文件中，这样可以使原来的库文件保持其独立性。
由于在Petter库中openHive函数使用open 和 read 函数来进行hive文件的读取，在VC条件下的read函数有一个问题，每当文件中存在一个0x1a的二进制数值时，read函数就会在那儿终止，这样就会导致hive文件无法完全导入。所以就使用了Windows API重写openHive，命名为My_openHive。相应的还重写了closeHive，writeHive并加上了前缀My_。
随后GetPatterns函数将使用RegEnumKey枚举的服务键值名称保存在pattern的全局变量指针中，为以后的匹配作准备。ShowHideService函数是由nk_ls函数改写的，将由Hive文件导出的buffer中的服务名称与pattern[I]作比较，这个比较过程使用CompareHive函数。若比较结果为相同，CompareHive会将pattern[I]置为NULL，以提高匹配速度，或许有更好的匹配算法，但在这个小程序中也不使用了。若结果不同，则说明该服务是隐藏的，显示出该隐藏服务的名称，文件路径（ShowPathImage是由cat_vk改写的），启动类型和服务类型，并将该隐藏服务的启动类型改为SERVICE_DISABLED。如果存在隐藏服务并且禁止了该隐藏服务（仅在buffer中的修改），通过调用My_writeHive将修改过的hive 的buffer保存在C:\tmp2.hiv文件中，此时提供用户一个选择“是否要禁用隐藏服务”，默认的选择是“否”，如果用户确实想要禁用，可输入“Yes”或“Ｙ＂，接着使用RestoreServiceInfo函数将C:\tmp2.hiv文件导回原来的%SystemRoot%/System32/Config/System这个Hive文件中，这一步由系统自己来完成，值得一提的是Win32函数RegRestoreKey即使在dwFlags参数中使用了REG_FORCE_RESTORE (8) ，在第一次调用时往往会错误返回，一般在第二次调用就会成功，所以就使用了一个循环直到它成功后为止，并且调用它的进程需要有SE_RESTORE_NAME的权限。
至于让隐藏服务真正失去作用，仍然需要重新启动计算机之后。
下面给出KHS.C的完整源代码：
/*
* KHS.cpp - Kill Hide Services v0.1
* Copyright (c) 2005 linux2linux.
*
* It takes notes from knlsc and FHS.
* Thank you, Petter Nordahl-Hagen, for your "NT Registry Hive access library"
*
* Freely distributable in source or binary for noncommercial purposes.
*
* THIS SOFTWARE IS PROVIDED BY PETTER NORDAHL-HAGEN `AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#include "ntreg.h"
#include <windows.h>
char **pattern;
int pattern_count;
int nohideservice;
int ischange;
extern char *val_types[REG_MAX+1];
struct hive *My_openHive(char *filename, int mode);
void My_closeHive(struct hive *hdesc);
int CompareHive(char *sample)
{
int i;
for(i = 0; i < pattern_count ; i++)
{
if(pattern[i]!=NULL)
{
if( strcmp ( sample , pattern[ i ] ) == 0 )
{
free(pattern[i]);
pattern[i]=NULL;
return 1;
}
}
}
return 0;
}
//Because read can't work well in windows.
//while it read 0x1a from the opened file, the function read will stop there.
//I don't know the reason why, it work well in linux envoriment.
// read the dumped hive file to fill hive struct.
// return the point
struct hive *My_openHive(char *filename, int mode)
{
HANDLE hFile;
int szread;
struct hive *hdesc;
int vofs;
unsigned long pofs;
char *c;
struct hbin_page *p;
struct regf_header *hdr;
int verbose = (mode & HMODE_VERBOSE);
CREATE(hdesc,struct hive,1);
hdesc->filename = str_dup(filename);
hdesc->state = 0;
hdesc->size = 0;
hdesc->buffer = NULL;
hFile = CreateFile(hdesc->filename,
GENERIC_READ, // open for reading
0, // do not share
NULL, // no security
OPEN_ALWAYS, // existing file only
FILE_ATTRIBUTE_NORMAL, // normal file
NULL); // no attr. template
if (hFile == INVALID_HANDLE_VALUE)
{
printf("Could not open hive file."); // process error
return 0;
}
/* Read the whole file */
hdesc->size = GetFileSize(hFile, NULL);
ALLOC(hdesc->buffer,1,hdesc->size);
ReadFile(hFile, (void *)hdesc->buffer, hdesc->size, &szread, NULL);
CloseHandle(hFile);
if (szread < hdesc->size) {
printf("Could not read file, got %d bytes while expecting %d\n",
szread, hdesc->size);
My_closeHive(hdesc);
return(NULL);
}
/* Now run through file, tallying all pages */
/* NOTE/KLUDGE: Assume first page starts at offset 0x1000 */
pofs = 0x1000;
hdr = (struct regf_header *)hdesc->buffer;
if (hdr->id != 0x66676572) {
printf("openHive(%s): File does not seem to be a registry hive!\n",filename);
return(hdesc);
}
for (c = hdr->name; *c && (c < hdr->name + 64); c += 2) putchar(*c);
hdesc->rootofs = hdr->ofs_rootkey + 0x1000;
while (pofs < hdesc->size) {
#ifdef LOAD_DEBUG
if (verbose) hexdump(hdesc->buffer,pofs,pofs+0x20,1);
#endif
p = (struct hbin_page *)(hdesc->buffer + pofs);
if (p->id != 0x6E696268) {
printf("Page at 0x%lx is not 'hbin', assuming file contains garbage at end",pofs);
break;
}
hdesc->pages++;
#ifdef LOAD_DEBUG
if (verbose) printf("\n###### Page at 0x%0lx has size 0x%0lx, next at 0x%0lx ######\n",pofs,p->len_page,p->ofs_next);
#endif
if (p->ofs_next == 0) {
#ifdef LOAD_DEBUG
if (verbose) printf("openhive debug: bailing out.. pagesize zero!\n");
#endif
return(hdesc);
}
#if 0
if (p->len_page != p->ofs_next) {
#ifdef LOAD_DEBUG
if (verbose) printf("openhive debug: len & ofs not same. HASTA!\n");
#endif
exit(0);
}
#endif
vofs = pofs + 0x20; /* Skip page header */
#if 1
while (vofs-pofs < p->ofs_next) {
vofs += parse_block(hdesc,vofs,verbose);
}
#endif
pofs += p->ofs_next;
}
return(hdesc);
}
void My_closeHive(struct hive *hdesc)
{
FREE(hdesc->filename);
FREE(hdesc->buffer);
FREE(hdesc);
}
int My_writeHive(struct hive *hdesc)
{
HANDLE hFile;
DWORD dwBytesWritten;
hFile = CreateFile("C:\\tmp2.hiv",
GENERIC_WRITE, // open for writing
0, // do not share
NULL, // no security
CREATE_ALWAYS, // open or create
FILE_ATTRIBUTE_NORMAL, // normal file
NULL);
if(hFile == INVALID_HANDLE_VALUE)
{ printf("Can't open dump file");
return 0;
}
WriteFile(hFile, hdesc->buffer, hdesc->size,&dwBytesWritten, NULL);
if(dwBytesWritten != hdesc->size)
{
printf("WriteHive error\n");
}
CloseHandle(hFile);
return 0;
}
void CleanPatterns()
{
int i;
if(pattern!=NULL)
{
for(i = 0; i < pattern_count; i++)
{
if(pattern[i]!=NULL)
free(pattern[i]);
}
free(pattern);
}
}
void GetPatterns()
{
HANDLE hService;
CHAR achKey[MAX_PATH];
DWORD i;
DWORD retCode;
int Nohide = 1;
DWORD SubKeyNum = 0;
pattern_count = 0;
if(RegOpenKeyEx(
HKEY_LOCAL_MACHINE, // handle to open key
"SYSTEM\\ControlSet001\\Services", // subkey name
NULL, // reserved
KEY_ALL_ACCESS,// security access mask
&hService // handle to open key
) != ERROR_SUCCESS)
{
printf("sorry %d\n",GetLastError());
return;
}
RegQueryInfoKey( hService,
NULL,
NULL,
NULL,
&SubKeyNum,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL);
//Before it don't work well , because i set the wrong premission of HKEY
//KEY_ALL_ACCESS is needed
if(SubKeyNum == 0)
{
printf("SubKey's Number is NULL, it's too strange.\n");
return;
}
pattern = malloc(sizeof(char *) * SubKeyNum );
for (i = 0, retCode = ERROR_SUCCESS; retCode == ERROR_SUCCESS; i++)
{
retCode = RegEnumKey(
hService, // handle to key to query
i, // index of subkey to query
achKey, // buffer for subkey name
MAX_PATH // size of subkey name buffer
);
if (retCode == (DWORD)ERROR_SUCCESS)
{
//What i add to get pattern Services Table.
pattern[ pattern_count ] = strdup ( achKey ) ;
pattern_count++;
}
}
CloseHandle(hService);
}
void ShowPathImage(struct hive *hdesc, int nkofs, char *path)
{
void *data;
int len,i,type;
char string[SZ_MAX+1];
type = get_val_type(hdesc, nkofs, path);
if (type == -1) {
printf("No such value <%s>\n",path);
return;
}
len = get_val_len(hdesc, nkofs, path);
if (!len) {
printf("Value <%s> has zero length\n",path);
return;
}
data = (void *)get_val_data(hdesc, nkofs, path, 0);
if (!data) {
printf("Value <%s> references NULL-pointer (bad boy!)\n",path);
abort();
return;
}
switch (type) {
case REG_SZ:
case REG_EXPAND_SZ:
case REG_MULTI_SZ:
cheap_uni2ascii(data,string,len);
for (i = 0; i < (len>>1)-1; i++) {
if (string[i] == 0) string[i] = '\n';
if (type == REG_SZ) break;
}
puts(string);
break;
case REG_DWORD:
printf("0x%08x",*(unsigned short *)data);
break;
default:
printf("Don't know how to handle type yet!\n");
case REG_BINARY:
hexdump((char *)data, 0, len, 1);
}
}
void EnablePriv(LPCTSTR lpName)
{
HANDLE hToken;
LUID sedebugnameValue;
TOKEN_PRIVILEGES tkp;
if ( ! OpenProcessToken( GetCurrentProcess(),
TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken ) )
{ printf("open process error\n");
return;
}
if ( ! LookupPrivilegeValue( NULL, lpName , &sedebugnameValue ) ){
printf("can't find privilege error\n");
CloseHandle( hToken );
return;
}
tkp.PrivilegeCount = 1;
tkp.Privileges[0].Luid = sedebugnameValue;
tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
if ( ! AdjustTokenPrivileges( hToken, FALSE, &tkp, sizeof (tkp), NULL, NULL ) )
{
printf("adjust error\n");
CloseHandle( hToken );
}
}
int DumpServiceInfo()
{
HKEY hService;
EnablePriv(SE_BACKUP_NAME);
if(RegOpenKeyEx(
HKEY_LOCAL_MACHINE, // handle to open key
"SYSTEM\\ControlSet001\\Services", // subkey name
NULL, // reserved
KEY_ALL_ACCESS, // security access mask
&hService // handle to open key
) != ERROR_SUCCESS)
{ printf("can't get key handle\n");
return 0;
}
if(RegSaveKey(hService,"C:\\tmp.hiv",NULL) != ERROR_SUCCESS)
{
printf("Can't dump Service info\n");
CloseHandle(hService);
return 0;
}
CloseHandle(hService);
return 1;
}
void ShowHideService(struct hive *hdesc, char *path, int vofs, int type)
{
struct nk_key *key;
int nkofs;
struct ex_data ex;
int count = 0, countri = 0;
//wHAT I ADD
void *data;
int nkofs_cat;
int serviceno;
serviceno = 1;
nkofs = trav_path(hdesc, vofs, path, 0);
if(!nkofs) {
printf("nk_ls: Key <%s> not found\n",path);
abort();
return;
}
nkofs += 4;
key = (struct nk_key *)(hdesc->buffer + nkofs);
if (key->id != 0x6b6e) {
printf("Error: Not a 'nk' node!\n");
debugit(hdesc->buffer,hdesc->size);
}
if (key->no_subkeys) {
while ((ex_next_n(hdesc, nkofs, &count, &countri, &ex) > 0)) {
if(!CompareHive(ex.name) )
{
nohideservice = 0;
if(!(serviceno - 1))
printf("Hide Service List:\n");
printf("\n%d.------------------------------------------------------------\n",serviceno++ );
printf("Hide Service : %s\n", ex.name );
nkofs_cat = trav_path(hdesc, vofs, ex.name, 0);
printf("Image Path : ");
ShowPathImage(hdesc, nkofs_cat + 4, "ImagePath");
data = (void *) get_val_data(hdesc, nkofs_cat + 4, "Start", 0 );
if( data != NULL)
{
printf("Start Type : ");
switch(*(unsigned short *)data)
{
case 0:
printf("SERVICE_BOOT_START");
break;
case 1:
printf("SERVICE_SYSTEM_START");
break;
case 2:
printf("SERVICE_AUTO_START");
break;
case 3:
printf("SERVICE_DEMAND_START");
break;
case 4:
printf("SERVICE_DISABLED");
break;
default:
printf("UNKOWN START TYPE");
}
//disable the service
if( *(unsigned short *)data != 4 )
{
printf("(Will be set to Disabled)");
put_dword(hdesc, nkofs_cat + 4, "Start", 4);
ischange = 1;
}
printf("\n");
}
data = (void *) get_val_data(hdesc, nkofs_cat + 4, "Type", 0 );
printf("Service Type : ");
if( data != NULL)
{
if(*(unsigned short *)data & 1)
printf("SERVICE_KERNEL_DRIVER ");
if(*(unsigned short *)data & 2)
printf("SERVICE_FILE_SYSTEM_DRIVER " );
if(*(unsigned short *)data & 8)
printf("SERVICE_RECOGNIZER_DRIVER ");
if(*(unsigned short *)data & 16)
printf("SERVICE_WIN32_OWN_PROCESS ");
if(*(unsigned short *)data & 32)
printf("SERVICE_WIN32_SHARE_PROCESS ");
if(*(unsigned short *)data & 256)
printf("SERVICE_INTERACTIVE_PROCESS ");
printf("\n");
}
}
FREE(ex.name);
}
}
if(nohideservice)
printf("There are no hide services.\n");
else
printf("\nTotal Hide Services is %d\n\n",serviceno - 1);
}
int RestoreServiceInfo()
{
HKEY hService;
LONG tmp;
EnablePriv(SE_RESTORE_NAME);
if(RegOpenKeyEx(
HKEY_LOCAL_MACHINE, // handle to open key
"SYSTEM\\ControlSet001\\Services", // subkey name
NULL, // reserved
KEY_ALL_ACCESS,// security access mask
&hService // handle to open key
) != ERROR_SUCCESS)
{
printf("Can't open Service key\n");
return 0;
}
//The first time to Restore always fail even you set the Force flag
//The second time will success.
for(;;)
{
if((tmp = RegRestoreKey(hService,"C:\\tmp2.hiv", 8 ) ) == ERROR_SUCCESS )
{
break;
}
}
CloseHandle(hService);
return 1;
}
int main(int argc, char* argv[])
{
struct hive *pHive;
char c;
nohideservice = 1;
ischange = 0;
printf("KHS - kill hide services 0.1 by linux2linux, 2005/5/26.\n");
printf("Take notes from knlsc and FHS. \n\n");
if(!DumpServiceInfo())
return 0;
pHive = My_openHive("C:\\tmp.hiv",HMODE_RW);
if(pHive == NULL)
{
printf("Open Hive fail\n");
return 0;
}
GetPatterns();
ShowHideService(pHive,"",pHive->rootofs + 4 , 0);
CleanPatterns();
if(!nohideservice && ischange )
{
My_writeHive(pHive);
printf("Do you want Disable the hide Services ( Yes / No )? [ No ]:");
c = getchar();
if( ( c == 'Y' )|| c == 'y')
{
if( RestoreServiceInfo() )
printf("Success Restore\n");
}
else
{ printf("Quit without Restore.\n");
}
DeleteFile("C:\\tmp2.hiv");
}
DeleteFile("C:\\tmp.hiv");
My_closeHive(pHive);
return 0;
}
参考资源
１．The Offline NT Password Editor 源程序 - Petter Nordahl-Hagen
http://home.eunet.no/~pnordahl/ntpasswd/
２．<<Windows NT/2000 Native API Reference>> - Gary Nebbett
３．Knlsc, FHS, IceSword 使用说明
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