internal static void HashUInt32(Sha512HashFunction hashFunc, uint value)
{
byte[] array = BitConverter.GetBytes(value);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(array);
}
SignedPackageArchiveIOUtility.HashBytes(hashFunc, array);
}
internal static void HashUInt32(HashAlgorithm hashAlgorithm, uint value)
{
byte[] array = BitConverter.GetBytes(value);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(array);
}
SignedPackageArchiveIOUtility.HashBytes(hashAlgorithm, array);
}
/// <summary>
/// Verifies that a signed package archive's signature is valid and it has not been tampered with.
/// </summary>
/// <param name="reader">Signed package to verify</param>
/// <param name="hashAlgorithm">Hash algorithm to be used to hash data.</param>
/// <param name="expectedHash">Hash value of the original data.</param>
/// <returns>True if package archive's hash matches the expected hash</returns>
internal static bool VerifySignedPackageIntegrity(BinaryReader reader, HashAlgorithm hashAlgorithm, byte[] expectedHash)
{
if (reader == null)
{
throw new ArgumentNullException(nameof(reader));
}
if (hashAlgorithm == null)
{
throw new ArgumentNullException(nameof(hashAlgorithm));
}
if (expectedHash == null || expectedHash.Length == 0)
{
throw new ArgumentException(Strings.ArgumentCannotBeNullOrEmpty, nameof(reader));
}
// Make sure it is signed with a valid signature file
if (!IsSigned(reader))
{
throw new Exception(Strings.SignedPackageNotSignedOnVerify);
}
var metadata = SignedPackageArchiveIOUtility.ReadSignedArchiveMetadata(reader);
// Assert exactly one primary signature
SignedPackageArchiveIOUtility.AssertExactlyOnePrimarySignatureAndUpdateMetadata(metadata);
var signatureCentralDirectoryHeader = metadata.CentralDirectoryHeaders[metadata.SignatureCentralDirectoryHeaderIndex];
// Assert signature entry metadata
SignedPackageArchiveIOUtility.AssertSignatureEntryMetadata(reader, signatureCentralDirectoryHeader);
var centralDirectoryRecordsWithoutSignature = RemoveSignatureAndOrderByOffset(metadata);
try
{
// Read and hash from the start of the archive to the start of the file headers
reader.BaseStream.Seek(offset: 0, origin: SeekOrigin.Begin);
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashAlgorithm, metadata.StartOfFileHeaders);
// Read and hash file headers
foreach (var record in centralDirectoryRecordsWithoutSignature)
{
reader.BaseStream.Seek(offset: record.OffsetToFileHeader, origin: SeekOrigin.Begin);
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashAlgorithm, record.OffsetToFileHeader + record.FileEntryTotalSize);
}
// Order central directory records by their position
centralDirectoryRecordsWithoutSignature.Sort((x, y) => x.Position.CompareTo(y.Position));
// Update offset of any central directory record that has a file entry after signature
foreach (var record in centralDirectoryRecordsWithoutSignature)
{
reader.BaseStream.Seek(offset: record.Position, origin: SeekOrigin.Begin);
// Hash from the start of the central directory record until the relative offset of local file header (42 from the start of central directory record, including signature length)
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashAlgorithm, reader.BaseStream.Position + 42);
var relativeOffsetOfLocalFileHeader = (uint)(reader.ReadUInt32() + record.ChangeInOffset);
SignedPackageArchiveIOUtility.HashBytes(hashAlgorithm, BitConverter.GetBytes(relativeOffsetOfLocalFileHeader));
// Continue hashing file name, extra field, and file comment fields.
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashAlgorithm, reader.BaseStream.Position + record.HeaderSize - CentralDirectoryHeader.SizeInBytesOfFixedLengthFields);
}
reader.BaseStream.Seek(offset: metadata.EndOfCentralDirectory, origin: SeekOrigin.Begin);
// Hash until total entries in end of central directory record (8 bytes from the start of EOCDR)
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashAlgorithm, metadata.EndOfCentralDirectoryRecordPosition + 8);
var eocdrTotalEntries = (ushort)(reader.ReadUInt16() - 1);
var eocdrTotalEntriesOnDisk = (ushort)(reader.ReadUInt16() - 1);
SignedPackageArchiveIOUtility.HashBytes(hashAlgorithm, BitConverter.GetBytes(eocdrTotalEntries));
SignedPackageArchiveIOUtility.HashBytes(hashAlgorithm, BitConverter.GetBytes(eocdrTotalEntriesOnDisk));
// update the central directory size by substracting the size of the package signature file's central directory header
var eocdrSizeOfCentralDirectory = (uint)(reader.ReadUInt32() - signatureCentralDirectoryHeader.HeaderSize);
SignedPackageArchiveIOUtility.HashBytes(hashAlgorithm, BitConverter.GetBytes(eocdrSizeOfCentralDirectory));
var eocdrOffsetOfCentralDirectory = reader.ReadUInt32() - (uint)signatureCentralDirectoryHeader.FileEntryTotalSize;
SignedPackageArchiveIOUtility.HashBytes(hashAlgorithm, BitConverter.GetBytes(eocdrOffsetOfCentralDirectory));
// Hash until the end of the reader
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashAlgorithm, reader.BaseStream.Length);
hashAlgorithm.TransformFinalBlock(new byte[0], inputOffset: 0, inputCount: 0);
return(CompareHash(expectedHash, hashAlgorithm.Hash));
}
// If exception is throw in means the archive was not a valid package. It has been tampered, return false.
catch { }
return(false);
}
internal static string GetPackageContentHash(BinaryReader reader)
{
using (var hashFunc = new Sha512HashFunction())
{
// skip validating signature entry since we're just trying to get the content hash here instead of
// verifying signature entry.
var metadata = SignedPackageArchiveIOUtility.ReadSignedArchiveMetadata(reader, validateSignatureEntry: false);
var signatureCentralDirectoryHeader = metadata.GetPackageSignatureFileCentralDirectoryHeaderMetadata();
var centralDirectoryRecordsWithoutSignature = RemoveSignatureAndOrderByOffset(metadata);
// Read and hash from the start of the archive to the start of the file headers
reader.BaseStream.Seek(offset: 0, origin: SeekOrigin.Begin);
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashFunc, metadata.StartOfLocalFileHeaders);
// Read and hash file headers
foreach (var record in centralDirectoryRecordsWithoutSignature)
{
reader.BaseStream.Seek(offset: record.OffsetToLocalFileHeader, origin: SeekOrigin.Begin);
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashFunc, record.OffsetToLocalFileHeader + record.FileEntryTotalSize);
}
// Order central directory records by their position
centralDirectoryRecordsWithoutSignature.Sort((x, y) => x.Position.CompareTo(y.Position));
// Update offset of any central directory record that has a file entry after signature
foreach (var record in centralDirectoryRecordsWithoutSignature)
{
reader.BaseStream.Seek(offset: record.Position, origin: SeekOrigin.Begin);
// Hash from the start of the central directory record until the relative offset of local file header (42 from the start of central directory record, including signature length)
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashFunc, reader.BaseStream.Position + 42);
var relativeOffsetOfLocalFileHeader = (uint)(reader.ReadUInt32() + record.ChangeInOffset);
SignedPackageArchiveIOUtility.HashBytes(hashFunc, BitConverter.GetBytes(relativeOffsetOfLocalFileHeader));
// Continue hashing file name, extra field, and file comment fields.
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashFunc, reader.BaseStream.Position + record.HeaderSize - CentralDirectoryHeader.SizeInBytesOfFixedLengthFields);
}
reader.BaseStream.Seek(offset: metadata.EndOfCentralDirectory, origin: SeekOrigin.Begin);
// Hash until total entries in end of central directory record (8 bytes from the start of EOCDR)
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashFunc, metadata.EndOfCentralDirectory + 8);
var eocdrTotalEntries = (ushort)(reader.ReadUInt16() - 1);
var eocdrTotalEntriesOnDisk = (ushort)(reader.ReadUInt16() - 1);
SignedPackageArchiveIOUtility.HashBytes(hashFunc, BitConverter.GetBytes(eocdrTotalEntries));
SignedPackageArchiveIOUtility.HashBytes(hashFunc, BitConverter.GetBytes(eocdrTotalEntriesOnDisk));
// update the central directory size by substracting the size of the package signature file's central directory header
var eocdrSizeOfCentralDirectory = (uint)(reader.ReadUInt32() - signatureCentralDirectoryHeader.HeaderSize);
SignedPackageArchiveIOUtility.HashBytes(hashFunc, BitConverter.GetBytes(eocdrSizeOfCentralDirectory));
var eocdrOffsetOfCentralDirectory = reader.ReadUInt32() - (uint)signatureCentralDirectoryHeader.FileEntryTotalSize;
SignedPackageArchiveIOUtility.HashBytes(hashFunc, BitConverter.GetBytes(eocdrOffsetOfCentralDirectory));
// Hash until the end of the reader
SignedPackageArchiveIOUtility.ReadAndHashUntilPosition(reader, hashFunc, reader.BaseStream.Length);
hashFunc.Update(new byte[0], offset: 0, count: 0);
return(hashFunc.GetHash());
}
}