Index '1' is out of valid index range '0' to '0' for possibly stack al-CodePudding

Im using this function to adjust multiple privileges for the application at the same time but I run into this warning and I dont know how to fix it. I tried to do it with the union and offsetof but it didn't work. How would I allocate more memory for that structure?

#include <Windows.h>

int main()
{
    HANDLE hToken;
    TOKEN_PRIVILEGES tp = { 0 };
    LUID luid1, luid2;

    OpenProcessToken(hProcess, TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken);

    LookupPrivilegeValueW(NULL, SE_DEBUG_NAME, &luid1);
    LookupPrivilegeValueW(NULL, SE_SHUTDOWN_NAME, &luid2);

    //the code I tried
    union {
        TOKEN_PRIVILEGES tp;
        unsigned char storage[offsetof(TOKEN_PRIVILEGES, Privileges)   sizeof(LUID_AND_ATTRIBUTES) * 2];
    };

    tp.PrivilegeCount = 2;
    
    tp.Privileges[0].Luid = luid1;
    tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

    tp.Privileges[1].Luid = luid2; //the warning is here
    tp.Privileges[1].Attributes = SE_PRIVILEGE_ENABLED; //and here

    AdjustTokenPrivileges(hToken, FALSE, &tp, sizeof(TOKEN_PRIVILEGES), NULL, NULL);
}

CodePudding user response：

you can use for instanse such code

union {         
    ::TOKEN_PRIVILEGES tp;      
    struct {
        ULONG PrivilegeCount;
        LUID_AND_ATTRIBUTES Privileges[2];  
    };
};

PrivilegeCount = 2;
Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
Privileges[0].Luid = { SE_DEBUG_PRIVILEGE };
Privileges[1].Attributes = SE_PRIVILEGE_ENABLED;
Privileges[1].Luid = { SE_SHUTDOWN_PRIVILEGE };
AdjustTokenPrivileges(hToken, FALSE, &tp, 0, 0, 0);

also note that 4-th parameter of AdjustTokenPrivileges BufferLength (where you pass sizeof(TOKEN_PRIVILEGES) ) related to 5-th parameter but not to 3-th (which size also not equal to sizeof(TOKEN_PRIVILEGES) ). so you need pass 0 here.

also not need use LookupPrivilegeValueW but possible use hardcoded constants, like SE_DEBUG_PRIVILEGE - it declared in wdm.h

also you not need TOKEN_QUERY here - this need only if the PreviousState parameter is not NULL,

CodePudding user response：

The point of structures with trailing array of zero (or 1) size is to malloc a larger memory block and cast it to the struct.

DWORD numPriviledges = 5;
void* buffer = malloc (sizeof(TOKEN_PRIVILEGES)   sizeof(LUID_AND_ATTRIBUTES) * (numPriviledges - ANYSIZE_ARRAY));
PTOKEN_PRIVILEGES ptp = (PTOKEN_PRIVILEGES) buffer;
ptp->PrivilegeCount = numPriviledges;
...
ptp->Privileges[4] = something;
...
AdjustTokenPrivileges(hToken, FALSE, ptp, 0, NULL, 0);
ptp = NULL;
free(buffer);
buffer = NULL;

It's not meant to be allocated on stack, that's what the warning is trying to tell you. It's poor man's flexible array member from C99