For example, if a write-what-where is mitigated by the existence of a read-only page (which, in Linux, would often imply requiring the WP bit to be disabled in CR0), a Windows attacker can simply direct the write-what-where attack toward the pre-computed PTE address in order to disable the WriteProtect bit, and then follow that by the actual write-what-where on the data. ((PMMPTE)(((((ULONG)(x)) > 12) << 2) + PTE_BASE))Īs attackers have figured out, however, this “elegance” has notable security implications. * Convert an address to a corresponding PTE */ (MiAddressToPpe(Address)->u.Hard.Valid) &Įach iteration of the MMU table walk uses simple MiAddressTo macros such as the one below, which in turn rely on hard-code static addresses. (MiAddressToPxe(Address)->u.Hard.Valid) & For example, the function MmGetPhysicalAddress only needs to work as follows: PHYSICAL_ADDRESS
This elegant solutions allows instant O(1) translation of any virtual address to its corresponding PTE, and with the correct shifts and base addresses, a conversion into the corresponding PDE (and PPE/PXE on 圆4 systems). One of the most unique aspects of the Windows kernel is the reliance on a fixed kernel address to represent the virtual base address of an array of page table entries that describes the entire virtual address space, and the usage of a self-referencing entry which acts as a pivot describing the page directory for the space itself (and, on 圆4 systems, describing the page directory table itself, and the page map level 4 itself).
#Reactos cyrix windows 10
In the latest builds of Windows 10 Redstone 1, aka “Anniversary Update”, the kernel takes a much stronger toward Kernel Address Space Layout Randomization (KASLR), employing an arsenal of tools that can only be available to an operating system developer that also happens to own the world’s most commercially successful compiler, and the world’s most pervasive executable object image format. In some cases, entire mitigations (such as CFG) are undone due to their reliance on a single, well-known static address. As the Windows kernel continues to pursue in its quest for ever-stronger security features and exploit mitigations, the existence of fixed addresses in memory continues to undermine the advances in this area, as attackers can use data corruption vulnerabilities and combine these with stack and instruction pointer control in order to bypass SMEP, DEP, and countless other architectural defense-in-depth techniques.
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