c - Windbg 条件断点与嵌套结构中的字符串比较

Question

我一直在尝试仅当嵌套结构中的字符串作为参数匹配我选择的特定模式时才在函数内设置断点，如下所示:

bp `main.c:2236` ".block { .if ( $spat(\"@@(stNames->NameComponent.Buffer)\", \"*ab*\" )){.echo \"BKP HIT! \"; .printf \"%mu str\n\",> @@(NameInfo->FinalComponent.Buffer); } .else {.echo \"NO HIT \"; .printf \"%mu str:\n\", @@(stNames->NameComponent.Buffer); gc;} } "

这个断点设置在函数的开头，在参数符号已经被解析之后。它表现得很奇怪，有时即使 $spat 中的模式不匹配它也会一直被命中，有时即使模式匹配它也不会命中。

我也试过this运气不好，因为我找不到在嵌套结构的情况下使用 poi() 命令的方法。片段波纹管:

bp Kernel32!CreateFileW ".printf \"%mu\\n\", poi(esp+4); as /mu ${/v:FileName} poi(esp+4); .block{.if $spat(\"${FileName}\", \"*target*\") {.echo Hit} .else {.echo Not Yet;g;}}"

Answer 1

表达式\"@@(stNames->NameComponent.Buffer)\"可能 does not evaluate to a quoted string独立评估

当写条件时，把条件分解得越小越好
并将它们放在一个txt文件中，并提供断点的脚本文件
喜欢bp :32 " $$>a< c:\\windscrypted.txt更容易理解

如果问题是独立的，提供正确答案也会有帮助可复制的内容

因为我无法评估问题中难以理解的表达方式，所以我在下面提供了一个演示，看看这是否是要求的内容

编译链接助手

structnest:\>type "c:\Program Files\Microsoft Visual Studio 10.0\VC\compile.bat"

@ECHO OFF
REM Compile and Link Helper Utility.
REM Add New Entry CompileMe in Visual_Studio_IDE->Tools->ExternalTools.
REM Provide path to this bat file in command
REM Provide $(ItemFileName)$(ItemExt) as Arguments
REM $(BinDir) as Initial Directory
REM Enjoy One Click Compile & link Simple Single File Demo Sources
@call "C:\Program Files\Microsoft Visual Studio 10.0\VC\vcvarsall.bat" x86
cl /Zi /nologo /W4 /analyze %1% /link /RELEASE
pause

源文件详细信息

structnest:\>dir /b
structnest.cpp

structnest:\>type structnest.cpp
#include <windows.h>
#include <winternl.h>
#include <stdio.h>
#define SOMESIZE 20

typedef VOID (NTAPI *g_RtlInitUnicodeString) (PUNICODE_STRING DestinationStri
ng, PCWSTR SourceString );

#pragma pack (1)
typedef struct _OUTNEST
{
    int a;
    int b;
    short c;
    UNICODE_STRING Nestin;
}OutNest,*POutNest;
#pragma pack()

int main (void)
{
    POutNest MyNest = ( POutNest  ) calloc ( 0x01  , sizeof(OutNest)   );
    PWSTR    buff   = ( PWSTR     ) calloc ( 0x30 ,  sizeof(wchar_t)   );
    HMODULE hMod = LoadLibrary("ntdll.dll");
    if ( (hMod != NULL) && (MyNest != NULL)  && (buff != NULL))
    {
        g_RtlInitUnicodeString RtlInitUnicodeString = ( g_RtlInitUnicodeString )
 GetProcAddress ( hMod , "RtlInitUnicodeString");
        if (RtlInitUnicodeString != NULL )
        {
            for (int i = 0; i< SOMESIZE; i++)
            {
                swprintf_s(buff, 0x29 , L"this is string number %.2d",i);

                RtlInitUnicodeString(&MyNest->Nestin,buff);
                printf("%S\n",MyNest->Nestin.Buffer);
            }
            printf("done\n");
            goto getout;
        }
        printf("GetprocAddress failed\n");
        goto getout;
    }
    printf("calloc() %p %p LoadLib %p failed\n" , MyNest,buff,hMod);
getout:
    if (MyNest)
        free(MyNest);
    if(buff)
        free(buff);
    if(hMod)
        FreeLibrary(hMod);
    return 0;
}
structnest:\>"c:\Program Files\Microsoft Visual Studio 10.0\VC\compile.bat" stru
ctnest.cpp
Setting environment for using Microsoft Visual Studio 2010 x86 tools.
structnest.cpp
Press any key to continue . . .

structnest:\>dir /b *.exe
structnest.exe

structnest:\>structnest.exe
this is string number 00
this is string number 01
this is string number 02
this is string number 03
this is string number 04
this is string number 05
this is string number 06
this is string number 07
this is string number 08
this is string number 09
this is string number 10
this is string number 11
this is string number 12
this is string number 13
this is string number 14
this is string number 15
this is string number 16
this is string number 17
this is string number 18
this is string number 19
done

脚本文件详细信息

structnest:\>type c:\nestedbreak.txt
as /mu ${/v:mystr} @@( MyNest->Nestin.Buffer );
.block { r $t0 = $spat( "${mystr}", "*11" ); }
.if( @$t0 != 1 ) { gc } ;

explanation of script file

as /mu ${/v:mystr}
Sets the alias equivalent equal to the null-terminated Unicode string 
that begins at Address @@( MyNest->Nestin.Buffer ). 
.block {} to force alias evaluation.
a Pseudo register $t0 is set to the result of $spat() can be 0 or 1

"${mystr}" on alias evaluation will become "this is string number 00" 
a Double Quoted string not address or some other expression 

"*11" is again a Double Quoted wild card pattern string it will match "11"
 at any position in the Input String .

.if is a conditinal that will break only when @$t0 == 1 

现在我们有了一个稍微更全面的条件，其中每个表达式是独立可验证的，我们继续在断点中使用它

执行细节

structnest:\>cdb -c ".lines;g main;r;.echo SET A CONDITINAL BREAK POINT AND RUN
THE EXE;bp `:32` \" $$^>a^< c:\\nestedbreak.txt \";g ;.lastevent;.echo why did w
e break here ? now that we broke lets go again;g;q " structnest.exe

explanation as follows

cdb.exe      console mode windbg;
.lines;     load line information (lineinfo default off in cdb.exe needed to set bp on src lines)
g main;     ( we are interested in our code for which we have src not some random system module)
r;      print the registers to confirm we reached main properly
.echo       just a signal to show that we are alive and kicking
`:32` "$$>a< c:\\nestedbreak.txt"   conditional break point on src line 32 ( inner double quotes/ unaccpetable > < chars escaped )
g;      run the exe
.lastevent;     shows the reason why we broke;
.echo       a signal to indicate that we broke
g;q;        finish running the exe and quit debugger

执行输出详情

structnest:\>cdb -c ".lines;g main;r;.echo SET A CONDITINAL BREAK POINT AND RUN
THE EXE;bp `:32` \" $$^>a^< c:\\nestedbreak.txt \";g ;.lastevent;.echo why did w
e break here ? now that we broke lets go again;g;q " structnest.exe

Microsoft (R) Windows Debugger Version 6.12.0002.633 X86

0:000> cdb: Reading initial command '.lines;g main;r;.echo SET A CONDITINAL BREA
K POINT AND RUN THE EXE;bp `:32` " $$>a< c:\\nestedbreak.txt ";g ;.lastevent;.ec
ho why did we break here ? now that we broke lets go again;g;q '

Line number information will be loaded

eax=00034180 ebx=7ffd6000 ecx=00000001 edx=0041a5f0 esi=00000000 edi=00000000
eip=00401000 esp=0013ff7c ebp=0013ffc0 iopl=0         nv up ei pl zr na pe nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00000246
structnest!main:
00401000 55              push    ebp


SET A CONDITINAL BREAK POINT AND RUN THE EXE

this is string number 00
this is string number 01
this is string number 02
this is string number 03
this is string number 04
this is string number 05
this is string number 06
this is string number 07
this is string number 08
this is string number 09
this is string number 10
Last event: 16d0.2784: Hit breakpoint 0
  debugger time: Thu May 15 16:10:10.625 2014 (UTC + 5:30)
why did we break here ? now that we broke lets go again
this is string number 11
this is string number 12
this is string number 13
this is string number 14
this is string number 15
this is string number 16
this is string number 17
this is string number 18
this is string number 19
done
quit:

structnest:\>