private bool VerifyFileChecksum(byte[] Image, UInt32 Offset)
{
// This function only checks fixed checksum-values 0x55 and 0xAA.
UInt16 FileHeaderSize = 0x18;
UInt32 FileSize = ByteOperations.ReadUInt24(Image, Offset + 0x14);
byte[] Header = new byte[FileHeaderSize - 1];
System.Buffer.BlockCopy(Image, (int)Offset, Header, 0, FileHeaderSize - 1);
ByteOperations.WriteUInt16(Header, 0x10, 0); // Clear checksum
byte CurrentHeaderChecksum = ByteOperations.ReadUInt8(Image, Offset + 0x10);
byte CalculatedHeaderChecksum = ByteOperations.CalculateChecksum8(Header, 0, (UInt32)FileHeaderSize - 1);
if (CurrentHeaderChecksum != CalculatedHeaderChecksum)
{
return(false);
}
byte FileAttribs = ByteOperations.ReadUInt8(Image, Offset + 0x13);
byte CurrentFileChecksum = ByteOperations.ReadUInt8(Image, Offset + 0x11);
if ((FileAttribs & 0x40) > 0)
{
// Calculate file checksum
byte CalculatedFileChecksum = ByteOperations.CalculateChecksum8(Image, Offset + FileHeaderSize, FileSize - FileHeaderSize);
if (CurrentFileChecksum != CalculatedFileChecksum)
{
return(false);
}
}
else
{
// Fixed file checksum
if ((CurrentFileChecksum != 0xAA) && (CurrentFileChecksum != 0x55))
{
return(false);
}
}
return(true);
}
private void CalculateFileChecksum(byte[] Image, UInt32 Offset)
{
UInt16 FileHeaderSize = 0x18;
UInt32 FileSize = ByteOperations.ReadUInt24(Image, Offset + 0x14);
ByteOperations.WriteUInt16(Image, Offset + 0x10, 0); // Clear checksum
byte NewChecksum = ByteOperations.CalculateChecksum8(Image, Offset, (UInt32)FileHeaderSize - 1);
ByteOperations.WriteUInt8(Image, Offset + 0x10, NewChecksum); // File-Header checksum
byte FileAttribs = ByteOperations.ReadUInt8(Image, Offset + 0x13);
if ((FileAttribs & 0x40) > 0)
{
// Calculate file checksum
byte CalculatedFileChecksum = ByteOperations.CalculateChecksum8(Image, Offset + FileHeaderSize, FileSize - FileHeaderSize);
ByteOperations.WriteUInt8(Image, Offset + 0x11, CalculatedFileChecksum);
}
else
{
// Fixed file checksum
ByteOperations.WriteUInt8(Image, Offset + 0x11, 0xAA);
}
}
internal UEFI(byte[] UefiBinary)
{
Binary = UefiBinary;
string VolumeHeaderMagic;
UInt32?Offset = ByteOperations.FindAscii(Binary, "_FVH");
if (Offset == null)
{
throw new BadImageFormatException();
}
else
{
VolumeHeaderOffset = (UInt32)Offset - 0x28;
}
if (!VerifyVolumeChecksum(Binary, VolumeHeaderOffset))
{
throw new BadImageFormatException();
}
VolumeSize = ByteOperations.ReadUInt32(Binary, VolumeHeaderOffset + 0x20); // TODO: This is actually a QWORD
VolumeHeaderSize = ByteOperations.ReadUInt16(Binary, VolumeHeaderOffset + 0x30);
PaddingByteValue = (ByteOperations.ReadUInt32(Binary, VolumeHeaderOffset + 0x2C) & 0x00000800) > 0 ? (byte)0xFF : (byte)0x00; // EFI_FVB_ERASE_POLARITY = 0x00000800
// In the volume look for a file of type EFI_FV_FILETYPE_FIRMWARE_VOLUME_IMAGE (0x0B)
FileHeaderOffset = VolumeHeaderOffset + VolumeHeaderSize;
bool VolumeFound = false;
int FileType;
UInt32 FileSize;
do
{
if (!VerifyFileChecksum(Binary, FileHeaderOffset))
{
throw new BadImageFormatException();
}
FileType = ByteOperations.ReadUInt8(Binary, FileHeaderOffset + 0x12);
FileSize = ByteOperations.ReadUInt24(Binary, FileHeaderOffset + 0x14);
if (FileType == 0x0B) // EFI_FV_FILETYPE_FIRMWARE_VOLUME_IMAGE
{
VolumeFound = true;
}
else
{
FileHeaderOffset += FileSize;
// FileHeaderOffset in Volume-body must be Align 8
// In the file-header-attributes the file-alignment relative to the start of the volume is always set to 1,
// so that alignment can be ignored.
FileHeaderOffset = ByteOperations.Align(VolumeHeaderOffset + VolumeHeaderSize, FileHeaderOffset, 8);
}
}while (!VolumeFound && (FileHeaderOffset < (VolumeHeaderOffset + VolumeSize)));
if (!VolumeFound)
{
throw new BadImageFormatException();
}
// Look in file for section of type EFI_SECTION_GUID_DEFINED (0x02)
SectionHeaderOffset = FileHeaderOffset + 0x18;
int SectionType;
UInt32 SectionSize;
UInt16 SectionHeaderSize = 0;
bool DecompressedVolumeFound = false;
do
{
SectionType = ByteOperations.ReadUInt8(Binary, SectionHeaderOffset + 0x03);
SectionSize = ByteOperations.ReadUInt24(Binary, SectionHeaderOffset + 0x00);
if (SectionType == 0x02) // EFI_SECTION_GUID_DEFINED
{
SectionHeaderSize = ByteOperations.ReadUInt16(Binary, SectionHeaderOffset + 0x14);
DecompressedVolumeFound = true;
}
else
{
SectionHeaderOffset += SectionSize;
// SectionHeaderOffset in File-body must be Align 4
SectionHeaderOffset = ByteOperations.Align(FileHeaderOffset + 0x18, SectionHeaderOffset, 4);
}
}while (!DecompressedVolumeFound && (SectionHeaderOffset < (FileHeaderOffset + FileSize)));
if (!DecompressedVolumeFound)
{
throw new BadImageFormatException();
}
// Decompress subvolume
CompressedSubImageOffset = SectionHeaderOffset + SectionHeaderSize;
CompressedSubImageSize = SectionSize - SectionHeaderSize;
// DECOMPRESS HERE
DecompressedImage = LZMA.Decompress(Binary, CompressedSubImageOffset, CompressedSubImageSize);
// Extracted volume contains Sections at its root level
DecompressedVolumeSectionHeaderOffset = 0;
DecompressedVolumeFound = false;
do
{
SectionType = ByteOperations.ReadUInt8(DecompressedImage, DecompressedVolumeSectionHeaderOffset + 0x03);
SectionSize = ByteOperations.ReadUInt24(DecompressedImage, DecompressedVolumeSectionHeaderOffset + 0x00);
SectionHeaderSize = ByteOperations.ReadUInt16(DecompressedImage, DecompressedVolumeSectionHeaderOffset + 0x14);
if (SectionType == 0x17) // EFI_SECTION_FIRMWARE_VOLUME_IMAGE
{
DecompressedVolumeFound = true;
}
else
{
DecompressedVolumeSectionHeaderOffset += SectionSize;
// SectionHeaderOffset in File-body must be Align 4
DecompressedVolumeSectionHeaderOffset = ByteOperations.Align(FileHeaderOffset + 0x18, DecompressedVolumeSectionHeaderOffset, 4);
}
}while (!DecompressedVolumeFound && (DecompressedVolumeSectionHeaderOffset < DecompressedImage.Length));
if (!DecompressedVolumeFound)
{
throw new BadImageFormatException();
}
DecompressedVolumeHeaderOffset = DecompressedVolumeSectionHeaderOffset + 4;
// PARSE COMPRESSED VOLUME
VolumeHeaderMagic = ByteOperations.ReadAsciiString(DecompressedImage, DecompressedVolumeHeaderOffset + 0x28, 0x04);
if (VolumeHeaderMagic != "_FVH")
{
throw new BadImageFormatException();
}
if (!VerifyVolumeChecksum(DecompressedImage, DecompressedVolumeHeaderOffset))
{
throw new BadImageFormatException();
}
Int32 DecompressedVolumeSize = ByteOperations.ReadInt32(DecompressedImage, DecompressedVolumeHeaderOffset + 0x20); // TODO: This is actually a QWORD
UInt16 DecompressedVolumeHeaderSize = ByteOperations.ReadUInt16(DecompressedImage, DecompressedVolumeHeaderOffset + 0x30);
// The files in this decompressed volume are the real EFI's.
UInt32 DecompressedFileHeaderOffset = DecompressedVolumeHeaderOffset + DecompressedVolumeHeaderSize;
EFI CurrentEFI;
do
{
if ((DecompressedFileHeaderOffset + 0x18) >= (DecompressedVolumeHeaderOffset + DecompressedVolumeSize))
{
break;
}
bool ContentFound = false;
for (int i = 0; i < 0x18; i++)
{
if (DecompressedImage[DecompressedFileHeaderOffset + i] != PaddingByteValue)
{
ContentFound = true;
break;
}
}
if (!ContentFound)
{
break;
}
FileSize = ByteOperations.ReadUInt24(DecompressedImage, DecompressedFileHeaderOffset + 0x14);
if ((DecompressedFileHeaderOffset + FileSize) >= (DecompressedVolumeHeaderOffset + DecompressedVolumeSize))
{
break;
}
if (!VerifyFileChecksum(DecompressedImage, DecompressedFileHeaderOffset))
{
throw new BadImageFormatException();
}
CurrentEFI = new EFI();
CurrentEFI.Type = ByteOperations.ReadUInt8(DecompressedImage, DecompressedFileHeaderOffset + 0x12);
byte[] FileGuidBytes = new byte[0x10];
System.Buffer.BlockCopy(DecompressedImage, (int)DecompressedFileHeaderOffset + 0x00, FileGuidBytes, 0, 0x10);
CurrentEFI.Guid = new Guid(FileGuidBytes);
// Parse sections of the EFI
CurrentEFI.FileOffset = DecompressedFileHeaderOffset;
UInt32 DecompressedSectionHeaderOffset = DecompressedFileHeaderOffset + 0x18;
do
{
SectionType = ByteOperations.ReadUInt8(DecompressedImage, DecompressedSectionHeaderOffset + 0x03);
SectionSize = ByteOperations.ReadUInt24(DecompressedImage, DecompressedSectionHeaderOffset + 0x00);
// SectionTypes that are relevant here:
// 0x10 = PE File
// 0x19 = RAW
// 0x15 = Description
// Not all section headers in the UEFI specs are 4 bytes long,
// but the sections that are used in Windows Phone EFI's all have a header of 4 bytes.
if (SectionType == 0x15)
{
CurrentEFI.Name = ByteOperations.ReadUnicodeString(DecompressedImage, DecompressedSectionHeaderOffset + 0x04, SectionSize - 0x04).TrimEnd(new char[] { (char)0, ' ' });
}
else if ((SectionType == 0x10) || (SectionType == 0x19))
{
CurrentEFI.SectionOffset = DecompressedSectionHeaderOffset;
CurrentEFI.BinaryOffset = DecompressedSectionHeaderOffset + 0x04;
CurrentEFI.Size = SectionSize - 0x04;
}
DecompressedSectionHeaderOffset += SectionSize;
// SectionHeaderOffset in File-body must be Align 4
DecompressedSectionHeaderOffset = ByteOperations.Align(DecompressedFileHeaderOffset + 0x18, DecompressedSectionHeaderOffset, 4);
}while (DecompressedSectionHeaderOffset < (DecompressedFileHeaderOffset + FileSize));
DecompressedFileHeaderOffset += FileSize;
// FileHeaderOffset in Volume-body must be Align 8
// In the file-header-attributes the file-alignment relative to the start of the volume is always set to 1,
// so that alignment can be ignored.
DecompressedFileHeaderOffset = ByteOperations.Align(DecompressedVolumeHeaderOffset + DecompressedVolumeHeaderSize, DecompressedFileHeaderOffset, 8);
EFIs.Add(CurrentEFI);
}while (DecompressedFileHeaderOffset < (DecompressedVolumeHeaderOffset + DecompressedVolumeSize));
}
