首先，如果我的标题在技术上不准确，我会道歉。我不确定究竟发生了什么，并且无论如何都能描述它。
我正在尝试为程序中的特定用途解码SSL证书。我p /调用了所有必要的CryptoAPI函数和结构，并且在调试模式下，一切都按预期工作。但是，当程序作为服务在发布模式下运行时（这是该程序的目的），我在尝试解码扩展时遇到访问冲突。为了使扩展更容易解码，我创建了一个可用于表示任何扩展的泛型类。此类包含TStruct类型的对象，该对象表示扩展所基于的基础结构。它有一个byte []类型的EncryptedValue字段，它将加密/解密扩展数据并将其放在结构中。基类如下：
public abstract class ExtensionBase<TStruct> : IExtensionBase where TStruct : new()
{
//The underlying struct
protected TStruct objectData = new TStruct();
//The identifier of the struct, ie: szOID_BASIC_CONSTRAINTS
public string Identifier { get; protected set; }
//An enum representing the structure type, ie: X509_BASIC_CONSTRAINTS
public CertStructType StructureType { get; protected set; }
//Determines if the extension is critical
public bool IsCritical { get; protected set; }
//Overridden in any child class to determine if that extension actually contains
//data that should be encoded
public abstract bool HasData { get; }
//Encrypts/decrypts the data from/to the underlying structure
public virtual byte[] EncryptedValue
{
get
{
uint encodedSize = 0;
//PinnedHandle is a class that I wrote to wrap a GCHandle.
//It has an implicit cast to IntPtr that returns GCHandle.AddrOfPinnedObject
//The finalizer of the class releases the GCHandle if it is a valid handle
IntPtr dataPtr = new PinnedHandle(objectData);
byte[] retVal = null;
if (StructureType != CertStructType.None)
{
if (!Crypt32.CryptEncodeObjectEx((uint)CertEncoding.X509Asn,
(uint)StructureType,
dataPtr,
0,
IntPtr.Zero,
null,
ref encodedSize))
throw new Win32Exception();
retVal = new byte[encodedSize];
if (!Crypt32.CryptEncodeObjectEx((uint)CertEncoding.X509Asn,
(uint)StructureType,
dataPtr,
0,
IntPtr.Zero,
retVal,
ref encodedSize))
throw new Win32Exception();
}
else
{
if (!Crypt32.CryptEncodeObjectEx((uint)CertEncoding.X509Asn,
Identifier,
dataPtr,
0,
IntPtr.Zero,
null,
ref encodedSize))
throw new Win32Exception();
retVal = new byte[encodedSize];
if (!Crypt32.CryptEncodeObjectEx((uint)CertEncoding.X509Asn,
Identifier,
dataPtr,
0,
IntPtr.Zero,
retVal,
ref encodedSize))
throw new Win32Exception();
}
return retVal;
}
set
{
uint decodedSize = 0;
IntPtr decodedData = IntPtr.Zero;
if(StructureType != CertStructType.None)
decodedData = Crypt32.CryptDecodeObjectEx(StructureType, value);
else
decodedData = Crypt32.CryptDecodeObjectEx(Identifier, value);
TStruct data = (TStruct)Marshal.PtrToStructure(decodedData, typeof(TStruct));
objectData = data;
Marshal.FreeHGlobal(decodedData);
}
}
public ExtensionBase(string id)
{
Identifier = id;
StructureType = CertStructType.None;
}
public ExtensionBase(string id, CertStructType structType)
{
Identifier = id;
StructureType = structType;
}
}
给我带来问题的一个子类是CertKeyUsage类，它使用CRYPT_BIT_BLOB结构来表示它的数据：
public class CertKeyUsage : ExtensionBase<CertKeyUsageFlags, CRYPT_BIT_BLOB>
{
public override bool HasData
{
get { return Value != CertKeyUsageFlags.None; }
}
public override unsafe byte[] EncryptedValue
{
get
{
CertKeyUsageFlags flags = Value;
objectData.cbData = 2;
objectData.cUnusedBits = 0;
objectData.pbData = new IntPtr(&flags);
return base.EncryptedValue;
}
set
{
try
{
//The following code was taken directly from Microsoft's implementation
//of X509Certificate
base.EncryptedValue = value;
if (objectData.cbData > 4)
objectData.cbData = 4;
byte[] keyUsage = new byte[4];
//This if statement returns true, and the following Marshal.Copy statement
//is where the program crashes with the Access Violation. As it is an unmanaged
//exception, the try/catch block doesn't do anything and the app dies
if (objectData.pbData != IntPtr.Zero)
Marshal.Copy(objectData.pbData, keyUsage, 0, (int) objectData.cbData);
Value = (CertKeyUsageFlags) BitConverter.ToUInt32(keyUsage, 0);
}
catch
{
}
}
}
public CertKeyUsage()
: base(CertOid.szOID_KEY_USAGE, CertStructType.X509KeyUsage)
{
IsCritical = true;
}
}
这段代码与调试版本有什么不同，会导致上述现场的访问冲突？我能做些什么来让它正常工作。这个特定的扩展并不重要，我可以跳过它，但在注释掉导致异常的上面的代码后，另一个扩展将崩溃。我不能评论所有扩展，并且它移动到不同位置的事实告诉我，我的代码存在一些我遗漏的潜在问题。任何帮助或建议将不胜感激。
这些是我正在调用的p /被调用函数：
[DllImport("crypt32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
public static extern bool CryptEncodeObjectEx(uint certEncodingType,
[MarshalAs(UnmanagedType.LPStr)]
string structType,
IntPtr structInfo,
uint flags,
IntPtr encodePara,
byte[] encodedData,
[In, Out] ref uint encodedSize);
[DllImport("crypt32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
public static extern bool CryptEncodeObjectEx(uint certEncodingType,
uint structType,
IntPtr structInfo,
uint flags,
IntPtr encodePara,
byte[] encodedData,
[In, Out] ref uint encodedSize);
[DllImport("crypt32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
public static extern bool CryptDecodeObjectEx(uint certEncodingType,
[MarshalAs(UnmanagedType.LPStr)]
string structType,
byte[] encodedData,
uint encodedDataSize,
uint flags,
IntPtr encodePara,
IntPtr decodedData,
[In, Out] ref uint decodedDataSize);
[DllImport("crypt32.dll", CharSet = CharSet.Ansi, SetLastError = true)]
public static extern bool CryptDecodeObjectEx(uint certEncodingType,
uint structType,
byte[] encodedData,
uint encodedDataSize,
uint flags,
IntPtr encodePara,
IntPtr decodedData,
[In, Out] ref uint decodedDataSize);
包装CryptDecodeObjectEx的函数：
public static IntPtr CryptDecodeObjectEx(string structType, byte[] encodedData)
{
uint encodedSize = (uint)encodedData.Length;
uint decodedSize = 0;
IntPtr decodedData = IntPtr.Zero;
if (!CryptDecodeObjectEx((uint)CertEncoding.X509Asn,
structType,
encodedData,
encodedSize,
0,
IntPtr.Zero,
decodedData,
ref decodedSize))
throw new Win32Exception();
decodedData = Marshal.AllocHGlobal((int)decodedSize);
if (!CryptDecodeObjectEx((uint)CertEncoding.X509Asn,
structType,
encodedData,
encodedSize,
0,
IntPtr.Zero,
decodedData,
ref decodedSize))
throw new Win32Exception();
return decodedData;
}
public static IntPtr CryptDecodeObjectEx(uint structType, byte[] encodedData)
{
uint encodedSize = (uint)encodedData.Length;
uint decodedSize = 0;
IntPtr decodedData = IntPtr.Zero;
if (!CryptDecodeObjectEx((uint)CertEncoding.X509Asn,
structType,
encodedData,
encodedSize,
0,
IntPtr.Zero,
decodedData,
ref decodedSize))
throw new Win32Exception();
decodedData = Marshal.AllocHGlobal((int)decodedSize);
if (!CryptDecodeObjectEx((uint)CertEncoding.X509Asn,
structType,
encodedData,
encodedSize,
0,
IntPtr.Zero,
decodedData,
ref decodedSize))
throw new Win32Exception();
return decodedData;
}
一时兴起，我决定将程序编译为X86而不是AnyCPU，一切都按预期工作。这让我相信问题实际上出现在这部分代码中：
public static IntPtr Next<T>(this IntPtr val)
{
T retVal = (T)Marshal.PtrToStructure(val, typeof(T));
if (Environment.Is64BitProcess)
return (IntPtr)((long)val + Marshal.SizeOf(retVal));
return (IntPtr)((int)val + Marshal.SizeOf(retVal));
}
这是我用来通过指向结构数组的指针枚举的代码。传入结构类型，并返回IntPtr到数组中的下一个结构。 32位版本正常工作，但显然我的64位版本的逻辑有点缺乏。