internal ExcelVbaProtection(ExcelVbaProject project)
{
_project = project;
VisibilityState = true;
}
/// <summary>
/// Create an empty VBA project.
/// </summary>
public void CreateVBAProject()
{
if (_vba != null || _package.Package.PartExists(new Uri(ExcelVbaProject.PartUri, UriKind.Relative)))
{
throw (new InvalidOperationException("VBA project already exists."));
}
_vba = new ExcelVbaProject(this);
_vba.Create();
}
internal byte[] SignProject(ExcelVbaProject proj)
{
if (!Certificate.HasPrivateKey)
{
//throw (new InvalidOperationException("The certificate doesn't have a private key"));
Certificate = null;
return null;
}
var hash = GetContentHash(proj);
BinaryWriter bw = new BinaryWriter(new MemoryStream());
bw.Write((byte)0x30); //Constructed Type
bw.Write((byte)0x32); //Total length
bw.Write((byte)0x30); //Constructed Type
bw.Write((byte)0x0E); //Length SpcIndirectDataContent
bw.Write((byte)0x06); //Oid Tag Indentifier
bw.Write((byte)0x0A); //Lenght OId
bw.Write(new byte[] { 0x2B, 0x06, 0x01, 0x04, 0x01, 0x82, 0x37, 0x02, 0x01, 0x1D }); //Encoded Oid 1.3.6.1.4.1.311.2.1.29
bw.Write((byte)0x04); //Octet String Tag Identifier
bw.Write((byte)0x00); //Zero length
bw.Write((byte)0x30); //Constructed Type (DigestInfo)
bw.Write((byte)0x20); //Length DigestInfo
bw.Write((byte)0x30); //Constructed Type (Algorithm)
bw.Write((byte)0x0C); //length AlgorithmIdentifier
bw.Write((byte)0x06); //Oid Tag Indentifier
bw.Write((byte)0x08); //Lenght OId
bw.Write(new byte[] { 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05 }); //Encoded Oid for 1.2.840.113549.2.5 (AlgorithmIdentifier MD5)
bw.Write((byte)0x05); //Null type identifier
bw.Write((byte)0x00); //Null length
bw.Write((byte)0x04); //Octet String Identifier
bw.Write((byte)hash.Length); //Hash length
bw.Write(hash); //Content hash
ContentInfo contentInfo = new ContentInfo(((MemoryStream)bw.BaseStream).ToArray());
contentInfo.ContentType.Value = "1.3.6.1.4.1.311.2.1.4";
Verifier = new SignedCms(contentInfo);
var signer = new CmsSigner(Certificate);
Verifier.ComputeSignature(signer, false);
return Verifier.Encode();
}
private byte[] GetContentHash(ExcelVbaProject proj)
{
//MS-OVBA 2.4.2
var enc = System.Text.Encoding.GetEncoding(proj.CodePage);
BinaryWriter bw = new BinaryWriter(new MemoryStream());
bw.Write(enc.GetBytes(proj.Name));
bw.Write(enc.GetBytes(proj.Constants));
foreach (var reference in proj.References)
{
if (reference.ReferenceRecordID == 0x0D)
{
bw.Write((byte)0x7B);
}
if (reference.ReferenceRecordID == 0x0E)
{
//var r = (ExcelVbaReferenceProject)reference;
//BinaryWriter bwTemp = new BinaryWriter(new MemoryStream());
//bwTemp.Write((uint)r.Libid.Length);
//bwTemp.Write(enc.GetBytes(r.Libid));
//bwTemp.Write((uint)r.LibIdRelative.Length);
//bwTemp.Write(enc.GetBytes(r.LibIdRelative));
//bwTemp.Write(r.MajorVersion);
//bwTemp.Write(r.MinorVersion);
foreach (byte b in BitConverter.GetBytes((uint)reference.Libid.Length)) //Length will never be an UInt with 4 bytes that aren't 0 (> 0x00FFFFFF), so no need for the rest of the properties.
{
if (b != 0)
{
bw.Write(b);
}
else
{
break;
}
}
}
}
foreach (var module in proj.Modules)
{
var lines = module.Code.Split(new char[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
foreach (var line in lines)
{
if (!line.StartsWith("attribute", true, null))
{
bw.Write(enc.GetBytes(line));
}
}
}
var buffer = (bw.BaseStream as MemoryStream).ToArray();
var hp = System.Security.Cryptography.MD5CryptoServiceProvider.Create();
return hp.ComputeHash(buffer);
}
//Create Oid from a bytearray
//private string ReadHash(byte[] content)
//{
// StringBuilder builder = new StringBuilder();
// int offset = 0x6;
// if (0 < (content.Length))
// {
// byte num = content[offset];
// byte num2 = (byte)(num / 40);
// builder.Append(num2.ToString(null, null));
// builder.Append(".");
// num2 = (byte)(num % 40);
// builder.Append(num2.ToString(null, null));
// ulong num3 = 0L;
// for (int i = offset + 1; i < content.Length; i++)
// {
// num2 = content[i];
// num3 = (ulong)(ulong)(num3 << 7) + ((byte)(num2 & 0x7f));
// if ((num2 & 0x80) == 0)
// {
// builder.Append(".");
// builder.Append(num3.ToString(null, null));
// num3 = 0L;
// }
// //1.2.840.113549.2.5
// }
// }
// string oId = builder.ToString();
// return oId;
//}
internal void Save(ExcelVbaProject proj)
{
if (Certificate == null || Certificate.HasPrivateKey==false) //No signature. Remove any Signature part
{
if (Part != null)
{
foreach (var r in Part.GetRelationships())
{
Part.DeleteRelationship(r.Id);
}
Part.Package.DeletePart(Part.Uri);
}
return;
}
var ms = new MemoryStream();
var bw = new BinaryWriter(ms);
byte[] certStore = GetCertStore();
byte[] cert = SignProject(proj);
bw.Write((uint)cert.Length);
bw.Write((uint)44); //?? 36 ref inside cert ??
bw.Write((uint)certStore.Length); //cbSigningCertStore
bw.Write((uint)(cert.Length + 44)); //certStoreOffset
bw.Write((uint)0); //cbProjectName
bw.Write((uint)(cert.Length + certStore.Length + 44)); //projectNameOffset
bw.Write((uint)0); //fTimestamp
bw.Write((uint)0); //cbTimestampUrl
bw.Write((uint)(cert.Length + certStore.Length + 44 + 2)); //timestampUrlOffset
bw.Write(cert);
bw.Write(certStore);
bw.Write((ushort)0);//rgchProjectNameBuffer
bw.Write((ushort)0);//rgchTimestampBuffer
bw.Write((ushort)0);
bw.Flush();
var rel = proj.Part.GetRelationshipsByType(schemaRelVbaSignature).FirstOrDefault();
if (Part == null)
{
if (rel != null)
{
Uri = rel.TargetUri;
Part = proj._pck.GetPart(rel.TargetUri);
}
else
{
Uri = new Uri("/xl/vbaProjectSignature.bin", UriKind.Relative);
Part = proj._pck.CreatePart(Uri, ExcelPackage.schemaVBASignature);
}
}
if (rel == null)
{
proj.Part.CreateRelationship(PackUriHelper.ResolvePartUri(proj.Uri, Uri), TargetMode.Internal, schemaRelVbaSignature);
}
var b = ms.ToArray();
Part.GetStream(FileMode.Create).Write(b, 0, b.Length);
}
