To protect against this kind of problems, the NT kernel has two mechanisms: probing (check) and SEH (structured exception handling, Structured Exception Handling). Of course, when the function is fully implemented, it will change the Flags variable before writing it back, providing the ability to modify an arbitrary piece of memory (kernel), and in a controlled way - a real celebration for a hacker.
But these are all just examples born along the way - and targeted attackers may have months to come to the best solution to achieve their goals, and a seemingly small security flaw, such as this one, may turn out to be enough for someone to pull all secrets from your car and gain complete control over it.
#Is reactos secure generator
Some sections of memory often change with high intensity, and restoring the value previously stored there may, for example, reduce the entropy level of a random number generator of some cryptographic algorithm, or rewrite the table of memory pages with its old version, which should have already been destroyed by this moment, allowing you to access more memory, which can be used to compromise the system. But in reality it can bring enough problems. At first glance, writing back a value read from a specified memory area back there does not look so bad. In this case, the caller has the ability to write to memory (here we recall that this is arbitrarypointer - it can even refer to the kernel area!). UserInitiateShutdown will dereference the mentioned pointer, which will lead to a BSOD, usually called a “bug check” among kernel developers. For example, a program can simply pass a NULL pointer and thus exploit the vulnerability. Well, just dereferencing an unverified pointer is enough to make a DoS attack (denial of service) possible - a malicious program can shut down a computer without having the right to do it. Since quite a large part of this function has not yet been implemented, everything that happens above is just a few read and write cycles of the 4-byte value that the user pointed to. If (PsGetThreadProcessId(Thread) != gpidLogon) * If the caller is not Winlogon, do some security checks */ Now let's see what happens with ThreadInformation when it is passed to UserInitiateShutdown: But note that both of these parameters come directly from the user program, which means that some malicious bookmark, calling this function, can pass anything to it.
#Is reactos secure code
The number of bytes transferred is stored in ThreadInformationLength, and, as you can easily see, the code really checks to see exactly “4”, otherwise the execution will be interrupted with the STATUS_INFO_LENGTH_MISMATCH error.
If it is UserThreadInitiateShutdown, the block must have a 4-byte integer. Here ThreadInformation is a pointer to a certain block with data, and the ThreadInformationClass parameter shows how this data should be interpreted. This is a small piece of the NtUserSetInformationThread function, which is a system call in win32k.sys, which can be (more or less) directly called by user programs. Status = UserInitiateShutdown(Thread, (PULONG)ThreadInformation) If (ThreadInformationLength != sizeof(ULONG))
IN USERTHREADINFOCLASS ThreadInformationClass,
NtUserSetInformationThread(IN HANDLE ThreadHandle, Let's take a look at this code and see what's what: I will use this case as an example of a simple, but security-related error, as well as to illustrate some of the measures to which kernel code should be exposed if you really want to get a safe system. Recent discussionon the 66192nd SVN ReactOS audit mailing list, it was shown how easy it is to add critical vulnerability to the kernel code.
#Is reactos secure windows
If you are a Windows user, you should be familiar with pop-up windows every second Tuesday of the month reporting the installation of "critical security updates." Microsoft is making considerable efforts to constantly fix vulnerabilities in its operating systems, but it's worth it: in a world where the number of cyber attacks is increasing day by day, not a single loophole in the defense of our computers should remain open to potential attackers. “Well, at least something is safe with us.”
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