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CloverBootloader/MemoryFix/AptioMemoryFix/CustomSlide.c
Sergey Isakov 6a56c2951b refactoring, renaming, cleanup
2019-10-04 23:32:02 +03:00

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/**
Allows to choose a random KASLR slide offset,
when some offsets cannot be used.
by Download-Fritz & vit9696
**/
#include <Library/UefiLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/DeviceTreeLib.h>
#include <Library/OcMiscLib.h>
#include <Library/PrintLib.h>
#include <Library/RngLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <IndustryStandard/AppleCsrConfig.h>
#include <Register/Microcode.h>
#include "Config.h"
#include "CustomSlide.h"
#include "BootArgs.h"
#include "BootFixes.h"
#include "MemoryMap.h"
#include "RtShims.h"
#include "ServiceOverrides.h"
//
// Modified boot-args buffer with an additional slide parameter, when custom slide is used.
//
STATIC BOOLEAN mStoredBootArgsVarSet;
STATIC UINTN mStoredBootArgsVarSize;
STATIC CHAR8 mStoredBootArgsVar[BOOT_LINE_LENGTH];
//
// Memory map slide availability analysis status.
//
STATIC BOOLEAN mAnalyzeMemoryMapDone;
//
// Original csr-active-config value to be restored before kernel handoff.
//
STATIC BOOLEAN mCsrActiveConfigSet;
STATIC UINT32 mCsrActiveConfig;
//
// List of KASLR slides that do not conflict with the previously allocated memory.
//
STATIC UINT8 mValidSlides[TOTAL_SLIDE_NUM];
STATIC UINT32 mValidSlidesNum = TOTAL_SLIDE_NUM;
//
// Detect Sandy or Ivy Bridge CPUs, since they use a different slide formula.
//
STATIC BOOLEAN mSandyOrIvy;
STATIC BOOLEAN mSandyOrIvySet;
STATIC
BOOLEAN
IsSandyOrIvy (
VOID
)
{
CPU_MICROCODE_PROCESSOR_SIGNATURE Sig;
UINT32 CpuFamily;
UINT32 CpuModel;
if (!mSandyOrIvySet) {
Sig.Uint32 = 0;
AsmCpuid (1, &Sig.Uint32, NULL, NULL, NULL);
CpuFamily = Sig.Bits.Family;
if (CpuFamily == 15) {
CpuFamily += Sig.Bits.ExtendedFamily;
}
CpuModel = Sig.Bits.Model;
if (CpuFamily == 15 || CpuFamily == 6) {
CpuModel |= Sig.Bits.ExtendedModel << 4;
}
mSandyOrIvy = CpuFamily == 6 && (CpuModel == 0x2A || CpuModel == 0x3A);
mSandyOrIvySet = TRUE;
DEBUG ((DEBUG_VERBOSE, "Discovered CpuFamily %d CpuModel %d SandyOrIvy %d\n", CpuFamily, CpuModel, mSandyOrIvy));
}
return mSandyOrIvy;
}
STATIC
VOID
GetSlideRangeForValue (
UINT8 Slide,
UINTN *StartAddr,
UINTN *EndAddr
)
{
*StartAddr = (UINTN)Slide * SLIDE_GRANULARITY + BASE_KERNEL_ADDR;
//
// Skip ranges used by Intel HD 2000/3000.
//
if (Slide >= 0x80 && IsSandyOrIvy ()) {
*StartAddr += 0x10200000;
}
*EndAddr = *StartAddr + APTIOFIX_SPECULATED_KERNEL_SIZE;
}
STATIC
UINT8
GenerateRandomSlideValue (
VOID
)
{
UINT32 Clock = 0;
UINT32 Ecx = 0;
UINT8 Slide = 0;
UINT16 Value = 0;
BOOLEAN RdRandSupport;
AsmCpuid (0x1, NULL, NULL, &Ecx, NULL);
RdRandSupport = (Ecx & 0x40000000) != 0;
do {
if (RdRandSupport && GetRandomNumber16 (&Value) == EFI_SUCCESS && (UINT8) Value != 0) {
Slide = (UINT8) Value;
} else {
Clock = (UINT32) AsmReadTsc ();
Slide = (Clock & 0xFF) ^ ((Clock >> 8) & 0xFF);
}
} while (Slide == 0);
DEBUG ((DEBUG_VERBOSE, "Generated slide index %d value %d\n", Slide, mValidSlides[Slide % mValidSlidesNum]));
//
//FIXME: This is bad due to uneven distribution, but let's use it for now.
//
return mValidSlides[Slide % mValidSlidesNum];
}
#if APTIOFIX_CLEANUP_SLIDE_BOOT_ARGUMENT == 1
STATIC
VOID
HideSlideFromOS (
AMF_BOOT_ARGUMENTS *BootArgs
)
{
EFI_STATUS Status;
DTEntry Chosen;
CHAR8 *ArgsStr;
UINT32 ArgsSize;
//
// First, there is a BootArgs entry for XNU
//
RemoveArgumentFromCommandLine (BootArgs->CommandLine, "slide=");
//
// Second, there is a DT entry
//
DTInit ((VOID *)(UINTN)(*BootArgs->deviceTreeP), BootArgs->deviceTreeLength);
Status = DTLookupEntry (NULL, "/chosen", &Chosen);
if (!EFI_ERROR (Status)) {
DEBUG ((DEBUG_VERBOSE, "Found /chosen\n"));
Status = DTGetProperty (Chosen, "boot-args", (VOID **)&ArgsStr, &ArgsSize);
if (!EFI_ERROR (Status) && ArgsSize > 0) {
DEBUG ((DEBUG_VERBOSE, "Found boot-args in /chosen\n"));
RemoveArgumentFromCommandLine (ArgsStr, "slide=");
}
}
//
// Third, clean the boot args just in case
//
mValidSlidesNum = 0;
mStoredBootArgsVarSize = 0;
ZeroMem (mValidSlides, sizeof(mValidSlides));
ZeroMem (mStoredBootArgsVar, sizeof(mStoredBootArgsVar));
}
#endif
STATIC
VOID
DecideOnCustomSlideImplementation (
VOID
)
{
UINTN AllocatedMapPages;
UINTN MemoryMapSize;
EFI_MEMORY_DESCRIPTOR *MemoryMap;
UINTN MapKey;
EFI_STATUS Status;
UINTN DescriptorSize;
UINT32 DescriptorVersion;
UINTN Index;
UINTN Slide;
UINTN NumEntries;
UINTN MaxAvailableSize = 0;
UINT8 FallbackSlide = 0;
Status = GetMemoryMapAlloc (
&AllocatedMapPages,
&MemoryMapSize,
&MemoryMap,
&MapKey,
&DescriptorSize,
&DescriptorVersion
);
if (Status != EFI_SUCCESS) {
Print (L"AMF: Failed to obtain memory map for KASLR - %r\n", Status);
return;
}
//
// At this point we have a memory map that we could use to determine what slide values are allowed.
//
NumEntries = MemoryMapSize / DescriptorSize;
//
// Reset valid slides to zero and find actually working ones.
//
mValidSlidesNum = 0;
for (Slide = 0; Slide < TOTAL_SLIDE_NUM; Slide++) {
EFI_MEMORY_DESCRIPTOR *Desc = MemoryMap;
BOOLEAN Supported = TRUE;
UINTN StartAddr;
UINTN EndAddr;
UINTN DescEndAddr;
UINTN AvailableSize;
GetSlideRangeForValue ((UINT8)Slide, &StartAddr, &EndAddr);
AvailableSize = 0;
for (Index = 0; Index < NumEntries; Index++) {
DescEndAddr = (Desc->PhysicalStart + EFI_PAGES_TO_SIZE (Desc->NumberOfPages));
if ((Desc->PhysicalStart < EndAddr) && (DescEndAddr > StartAddr)) {
//
// The memory overlaps with the slide region.
//
if (Desc->Type != EfiConventionalMemory) {
//
// The memory is unusable atm.
//
Supported = FALSE;
break;
} else {
//
// The memory will be available for the kernel.
//
AvailableSize += EFI_PAGES_TO_SIZE (Desc->NumberOfPages);
if (Desc->PhysicalStart < StartAddr) {
//
// The region starts before the slide region.
// Subtract the memory that is located before the slide region.
//
AvailableSize -= (StartAddr - Desc->PhysicalStart);
}
if (DescEndAddr > EndAddr) {
//
// The region ends after the slide region.
// Subtract the memory that is located after the slide region.
//
AvailableSize -= (DescEndAddr - EndAddr);
}
}
}
Desc = NEXT_MEMORY_DESCRIPTOR (Desc, DescriptorSize);
}
if (AvailableSize > MaxAvailableSize) {
MaxAvailableSize = AvailableSize;
FallbackSlide = (UINT8)Slide;
}
if ((StartAddr + AvailableSize) != EndAddr) {
//
// The slide region is not continuous.
//
Supported = FALSE;
}
if (Supported) {
DEBUG ((DEBUG_VERBOSE, "Slide %03d at %08x:%08x should be ok.\n", (UINT32)Slide, (UINT32)StartAddr, (UINT32)EndAddr));
mValidSlides[mValidSlidesNum++] = (UINT8)Slide;
} else {
DEBUG ((DEBUG_VERBOSE, "Slide %03d at %08x:%08x cannot be used!\n", (UINT32)Slide, (UINT32)StartAddr, (UINT32)EndAddr));
}
}
gBS->FreePages ((EFI_PHYSICAL_ADDRESS)MemoryMap, AllocatedMapPages);
if (mValidSlidesNum != TOTAL_SLIDE_NUM) {
if (mValidSlidesNum == 0) {
Print (L"AMF: No slide values are usable! Falling back to %d with 0x%08X bytes!\n", FallbackSlide, MaxAvailableSize);
mValidSlides[mValidSlidesNum++] = (UINT8)FallbackSlide;
} else {
//
// Pretty-print valid slides as ranges.
// For example, 1, 2, 3, 4, 5 will become 1-5.
//
Print (L"AMF: Only %d/%d slide values are usable!\n", mValidSlidesNum, TOTAL_SLIDE_NUM);
NumEntries = 0;
for (Index = 0; Index <= mValidSlidesNum; Index++) {
if (Index == 0) {
Print (L"Valid slides: %d", mValidSlides[Index]);
} else if (Index == mValidSlidesNum || mValidSlides[Index - 1] + 1 != mValidSlides[Index]) {
if (NumEntries == 1) {
Print (L", %d", mValidSlides[Index - 1]);
} else if (NumEntries > 1) {
Print (L"-%d", mValidSlides[Index - 1]);
}
if (Index == mValidSlidesNum) {
Print (L"\n");
} else {
Print (L", %d", mValidSlides[Index]);
}
NumEntries = 0;
} else {
NumEntries++;
}
}
}
}
}
STATIC
EFI_STATUS
GetVariableCsrActiveConfig (
IN CHAR16 *VariableName,
IN EFI_GUID *VendorGuid,
OUT UINT32 *Attributes OPTIONAL,
IN OUT UINTN *DataSize,
OUT VOID *Data
)
{
EFI_STATUS Status;
UINT32 *Config;
//
// If we were asked for the size, just return it right away.
//
if (!Data || *DataSize < sizeof(UINT32)) {
*DataSize = sizeof(UINT32);
return EFI_BUFFER_TOO_SMALL;
}
Config = (UINT32 *)Data;
//
// Otherwise call the original function.
//
Status = OrgGetVariable (VariableName, VendorGuid, Attributes, DataSize, Data);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_INFO, "GetVariable csr-active-config returned %r\n", Status));
*Config = 0;
Status = EFI_SUCCESS;
if (Attributes) {
*Attributes =
EFI_VARIABLE_BOOTSERVICE_ACCESS |
EFI_VARIABLE_RUNTIME_ACCESS |
EFI_VARIABLE_NON_VOLATILE;
}
}
//
// We must unrestrict NVRAM from SIP or slide=X will not be supported.
//
mCsrActiveConfig = *Config;
mCsrActiveConfigSet = TRUE;
*Config |= CSR_ALLOW_UNRESTRICTED_NVRAM;
return Status;
}
STATIC
EFI_STATUS
GetVariableBootArgs (
IN CHAR16 *VariableName,
IN EFI_GUID *VendorGuid,
OUT UINT32 *Attributes OPTIONAL,
IN OUT UINTN *DataSize,
OUT VOID *Data
)
{
EFI_STATUS Status;
UINTN StoredBootArgsSize = BOOT_LINE_LENGTH;
UINT8 Slide;
CHAR8 SlideArgument[10];
CONST UINTN SlideArgumentLength = ARRAY_SIZE (SlideArgument)-1;
if (!mStoredBootArgsVarSet) {
Slide = GenerateRandomSlideValue ();
Status = OrgGetVariable (VariableName, VendorGuid, Attributes, &StoredBootArgsSize, mStoredBootArgsVar);
if (EFI_ERROR (Status)) {
mStoredBootArgsVar[0] = '\0';
}
//
// Note, the point is to always pass 3 characters to avoid side attacks on value length.
//
AsciiSPrint (SlideArgument, ARRAY_SIZE (SlideArgument), "slide=%-03d", Slide);
if (!AppendArgumentToCommandLine (mStoredBootArgsVar, SlideArgument, SlideArgumentLength)) {
//
// Broken boot-args, try to overwrite.
//
AsciiStrnCpyS (mStoredBootArgsVar, SlideArgumentLength + 1, SlideArgument, SlideArgumentLength + 1);;
}
mStoredBootArgsVarSize = AsciiStrLen (mStoredBootArgsVar) + 1;
mStoredBootArgsVarSet = TRUE;
}
if (Attributes) {
*Attributes =
EFI_VARIABLE_BOOTSERVICE_ACCESS |
EFI_VARIABLE_RUNTIME_ACCESS |
EFI_VARIABLE_NON_VOLATILE;
}
if (*DataSize >= mStoredBootArgsVarSize && Data) {
AsciiStrnCpyS (Data, *DataSize, mStoredBootArgsVar, mStoredBootArgsVarSize);
Status = EFI_SUCCESS;
} else {
Status = EFI_BUFFER_TOO_SMALL;
}
*DataSize = mStoredBootArgsVarSize;
return Status;
}
VOID
UnlockSlideSupportForSafeMode (
UINT8 *ImageBase,
UINTN ImageSize
)
{
//
// boot.efi performs the following check:
// if (State & (BOOT_MODE_SAFE | BOOT_MODE_ASLR)) == (BOOT_MODE_SAFE | BOOT_MODE_ASLR)) {
// * Disable KASLR *
// }
// We do not care about the asm it will use for it, but we could assume that the constants
// will be used twice and their location will be very close to each other.
//
// BOOT_MODE_SAFE | BOOT_MODE_ASLR constant is 0x4001 in hex.
// It has not changed since its appearance, so is most likely safe to look for.
// Furthermore, since boot.efi state mask uses higher bits, it is safe to assume that
// the comparison will be at least 32-bit.
//
//
// The new way patch is a workaround for 10.13.5 and newer, where the code got finally changed.
// if (State & BOOT_MODE_SAFE) {
// ReportFeature(FEATURE_BOOT_MODE_SAFE);
// if (State & BOOT_MODE_ASLR) {
// * Disable KASLR *
// }
// }
//
CONST UINT8 SearchSeqNew[] = {0xF6, 0xC4, 0x40, 0x75};
CONST UINT8 SearchSeq[] = {0x01, 0x40, 0x00, 0x00};
//
// This is a reasonable maximum distance to expect between the instructions.
//
CONST UINTN MaxDist = 0x10;
UINT8 *StartOff = ImageBase;
UINT8 *EndOff = StartOff + ImageSize - sizeof (SearchSeq) - MaxDist;
UINTN FirstOff = 0;
UINTN SecondOff = 0;
BOOLEAN NewWay = FALSE;
do {
while (StartOff + FirstOff <= EndOff) {
if (!CompareMem (StartOff + FirstOff, SearchSeqNew, sizeof (SearchSeqNew))) {
NewWay = TRUE;
break;
} else if (!CompareMem (StartOff + FirstOff, SearchSeq, sizeof (SearchSeq))) {
break;
}
FirstOff++;
}
DEBUG ((DEBUG_VERBOSE, "Found first %d at off %X\n", (UINT32)NewWay, (UINT32)FirstOff));
if (StartOff + FirstOff > EndOff) {
DEBUG ((DEBUG_INFO, "Failed to find first BOOT_MODE_SAFE | BOOT_MODE_ASLR sequence\n"));
break;
}
if (NewWay) {
//
// Here we just patch the comparison code and the check by straight nopping.
//
DEBUG ((DEBUG_VERBOSE, "Patching new safe mode aslr check...\n"));
SetMem (StartOff + FirstOff, sizeof (SearchSeqNew) + 1, 0x90);
return;
}
SecondOff = FirstOff + sizeof (SearchSeq);
while (
StartOff + SecondOff <= EndOff && FirstOff + MaxDist >= SecondOff &&
CompareMem (StartOff + SecondOff, SearchSeq, sizeof (SearchSeq))) {
SecondOff++;
}
DEBUG ((DEBUG_VERBOSE, "Found second at off %X\n", (UINT32)SecondOff));
if (FirstOff + MaxDist < SecondOff) {
DEBUG ((DEBUG_VERBOSE, "Trying next match...\n"));
SecondOff = 0;
FirstOff += sizeof (SearchSeq);
}
} while (SecondOff == 0);
if (SecondOff != 0) {
//
// Here we use 0xFFFFFFFF constant as a replacement value.
// Since the state values are contradictive (e.g. safe & single at the same time)
// We are allowed to use this instead of to simulate if (false).
//
DEBUG ((DEBUG_VERBOSE, "Patching safe mode aslr check...\n"));
SetMem (StartOff + FirstOff, sizeof (SearchSeq), 0xFF);
SetMem (StartOff + SecondOff, sizeof (SearchSeq), 0xFF);
}
}
BOOLEAN
OverlapsWithSlide (
EFI_PHYSICAL_ADDRESS Address,
UINTN Size
)
{
BOOLEAN SandyOrIvy;
EFI_PHYSICAL_ADDRESS Start;
EFI_PHYSICAL_ADDRESS End;
UINTN Slide = 0xFF;
SandyOrIvy = IsSandyOrIvy ();
if (SandyOrIvy) {
Slide = 0x7F;
}
Start = BASE_KERNEL_ADDR;
End = Start + Slide * SLIDE_GRANULARITY + APTIOFIX_SPECULATED_KERNEL_SIZE;
if (End >= Address && Start <= Address + Size) {
return TRUE;
} else if (SandyOrIvy) {
Start = 0x80 * SLIDE_GRANULARITY + BASE_KERNEL_ADDR + 0x10200000;
End = Start + Slide * SLIDE_GRANULARITY + APTIOFIX_SPECULATED_KERNEL_SIZE;
if (End >= Address && Start <= Address + Size) {
return TRUE;
}
}
return FALSE;
}
EFI_STATUS
EFIAPI
GetVariableCustomSlide (
IN CHAR16 *VariableName,
IN EFI_GUID *VendorGuid,
OUT UINT32 *Attributes OPTIONAL,
IN OUT UINTN *DataSize,
OUT VOID *Data
)
{
if (gMacOSBootNestedCount > 0 && VariableName && VendorGuid && DataSize &&
CompareGuid (VendorGuid, &gEfiAppleBootGuid)) {
//
// We override csr-active-config with CSR_ALLOW_UNRESTRICTED_NVRAM bit set
// to allow one to pass a custom slide value even when SIP is on.
// This original value of csr-active-config is returned to OS at XNU boot.
// This allows SIP to be fully enabled in the operating system.
//
if (!StrCmp (VariableName, L"csr-active-config")) {
return GetVariableCsrActiveConfig (
VariableName,
VendorGuid,
Attributes,
DataSize,
Data
);
}
#if APTIOFIX_ALLOW_CUSTOM_ASLR_IMPLEMENTATION == 1
//
// When we cannot allow some KASLR values due to used address we generate
// a random slide value among the valid options, which we we pass via boot-args.
// See DecideOnCustomSlideImplementation for more details.
//
else if (!StrCmp (VariableName, L"boot-args")) {
//
// We delay memory map analysis as much as we can, in case boot.efi or anything else allocates
// stuff with gBS->AllocatePool and it overlaps with the kernel area.
// Overriding AllocatePool with a custom allocator does not really improve the situation,
// because on older boards allocated memory above BASE_4GB causes instant reboots, and
// on the only (so far) problematic X99 and X299 we have no free region for our pool anyway.
// In any case, the current APTIOFIX_SPECULATED_KERNEL_SIZE value appears to work reliably.
//
if (!gSlideArgPresent && !mAnalyzeMemoryMapDone) {
DecideOnCustomSlideImplementation ();
mAnalyzeMemoryMapDone = TRUE;
}
//
// Only return custom boot-args if mValidSlidesNum were determined to be less than TOTAL_SLIDE_NUM
// And thus we have to use a custom slide implementation to boot reliably.
//
if (mValidSlidesNum != TOTAL_SLIDE_NUM && mValidSlidesNum > 0) {
return GetVariableBootArgs (
VariableName,
VendorGuid,
Attributes,
DataSize,
Data
);
}
}
#endif
}
return OrgGetVariable (VariableName, VendorGuid, Attributes, DataSize, Data);
}
VOID
RestoreCustomSlideOverrides (
AMF_BOOT_ARGUMENTS *BA
)
{
//
// Restore csr-active-config to a value it was before our slide=X alteration.
//
if (BA->csrActiveConfig && mCsrActiveConfigSet) {
*BA->csrActiveConfig = mCsrActiveConfig;
}
#if APTIOFIX_CLEANUP_SLIDE_BOOT_ARGUMENT == 1
//
// Having slide=X values visible in the operating system defeats the purpose of KASLR.
// Since our custom implementation works by passing random KASLR slide via boot-args,
// this is especially important.
//
HideSlideFromOS(BA);
#endif
}
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