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Ensure 3DES Exports are actually 3DES on all versions of Windows #112806

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Merged
vcsjones merged 1 commit into from
Feb 22, 2025
Merged

Ensure 3DES Exports are actually 3DES on all versions of Windows #112806

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71 changes: 35 additions & 36 deletions ...Cryptography/src/System/Security/Cryptography/X509Certificates/StorePal.Windows.Export.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,9 +75,7 @@ public void MoveTo(X509Certificate2Collection collection)
}

case X509ContentType.Pkcs12:
byte[] pkcs12 = ExportPkcs12(false, password, out bool aes256Sha256);
Debug.Assert(!aes256Sha256);
return pkcs12;
return ExportPkcs12Core(null, password);

case X509ContentType.SerializedStore:
return SaveToMemoryStore(Interop.Crypt32.CertStoreSaveAs.CERT_STORE_SAVE_AS_STORE);
Expand All @@ -92,55 +90,54 @@ public void MoveTo(X509Certificate2Collection collection)

public byte[] ExportPkcs12(Pkcs12ExportPbeParameters exportParameters, SafePasswordHandle password)
{
bool tryAes256sha256 = exportParameters is
Pkcs12ExportPbeParameters.Default or
Pkcs12ExportPbeParameters.Pbes2Aes256Sha256;

byte[] exported = ExportPkcs12(tryAes256sha256, password, out bool aes256Sha256);

// What we asked for and what we got are the same - so return it as-is.
if (tryAes256sha256 == aes256Sha256)
{
return exported;
}

if (!tryAes256sha256)
{
Debug.Fail("3DES PKCS12 export failed.");
throw new CryptographicException();
}

return ReEncryptAndSealPkcs12(exported, password, Helpers.WindowsAesPbe);
return ExportPkcs12Core(exportParameters, password);
}

public byte[] ExportPkcs12(PbeParameters exportParameters, SafePasswordHandle password)
{
byte[] exported = ExportPkcs12(preferAes256Sha256: true, password, out _);
byte[] exported = ExportPkcs12Core(null, password);
return ReEncryptAndSealPkcs12(exported, password, exportParameters);
}

private unsafe byte[] ExportPkcs12(bool preferAes256Sha256, SafePasswordHandle password, out bool aes256Sha256)
private unsafe byte[] ExportPkcs12Core(Pkcs12ExportPbeParameters? exportParameters, SafePasswordHandle password)
{
Interop.Crypt32.DATA_BLOB dataBlob = new Interop.Crypt32.DATA_BLOB(IntPtr.Zero, 0);
Interop.Crypt32.PFXExportFlags flags =
Interop.Crypt32.PFXExportFlags.EXPORT_PRIVATE_KEYS |
Interop.Crypt32.PFXExportFlags.REPORT_NOT_ABLE_TO_EXPORT_PRIVATE_KEY;

Interop.Crypt32.PKCS12_PBES2_EXPORT_PARAMS* exportParams = null;
aes256Sha256 = preferAes256Sha256 && s_supportsAes256Sha256;
PbeParameters? reEncodeParameters = null;

if (aes256Sha256)
if (exportParameters is Pkcs12ExportPbeParameters.Pbes2Aes256Sha256 or Pkcs12ExportPbeParameters.Default)
{
flags |= Interop.Crypt32.PFXExportFlags.PKCS12_EXPORT_PBES2_PARAMS;
// PKCS12_PBES2_ALG_AES256_SHA256
char* algStr = stackalloc char[] { 'A', 'E', 'S', '2', '5', '6', '-', 'S', 'H', 'A', '2', '5', '6', '\0' };
Interop.Crypt32.PKCS12_PBES2_EXPORT_PARAMS p = new()
if (s_supportsAes256Sha256)
{
dwSize = (uint)Marshal.SizeOf<Interop.Crypt32.PKCS12_PBES2_EXPORT_PARAMS>(),
hNcryptDescriptor = 0,
pwszPbes2Alg = algStr,
};
exportParams = &p;
flags |= Interop.Crypt32.PFXExportFlags.PKCS12_EXPORT_PBES2_PARAMS;
// PKCS12_PBES2_ALG_AES256_SHA256
char* algStr = stackalloc char[] { 'A', 'E', 'S', '2', '5', '6', '-', 'S', 'H', 'A', '2', '5', '6', '\0' };
Interop.Crypt32.PKCS12_PBES2_EXPORT_PARAMS p = new()
{
dwSize = (uint)Marshal.SizeOf<Interop.Crypt32.PKCS12_PBES2_EXPORT_PARAMS>(),
hNcryptDescriptor = 0,
pwszPbes2Alg = algStr,
};
exportParams = &p;
}
else
{
reEncodeParameters = Helpers.WindowsAesPbe;
}
}
else if (exportParameters == Pkcs12ExportPbeParameters.Pkcs12TripleDesSha1)
{
// Older Windows is not guaranteed to export in 3DES. If 3DES was asked for explicitly, then re-encode
// it as 3DES.
reEncodeParameters = Helpers.Windows3desPbe;
}
else
{
Debug.Assert(exportParameters is null);
}

if (!Interop.Crypt32.PFXExportCertStoreEx(_certStore, ref dataBlob, password, exportParams, flags))
Expand All @@ -160,7 +157,9 @@ private unsafe byte[] ExportPkcs12(bool preferAes256Sha256, SafePasswordHandle p
}
}

return pbEncoded;
return reEncodeParameters is not null ?
ReEncryptAndSealPkcs12(pbEncoded, password, reEncodeParameters) :
pbEncoded;
}

private static byte[] ReEncryptAndSealPkcs12(byte[] pkcs12, SafePasswordHandle password, PbeParameters newPbeParameters)
Expand Down
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