OWA not verifying emails signed and encrypted by OpenSSL

[Yash Dosi]

I am trying to create an android app which can send sign and encrypted
mails using OpenSSL.

So far I am able to send Signed Emails and verify them using both web
browsers and my android apps.

Same is the case with Encryption and Decryption.

But now when I am trying to send signed+encrypted mails from my android
app. The Exchange server is unable to verify/decrypt the mails send from my
android app.

When I am trying to open open these mails using OWA I get this error:

One or more errors occurred while the message was being loaded. Error:
(0x800ccef6)
The digital signature of this message couldn't be validated because an
error occurred while the message was being loaded.


Encryption and signing code:

*Sign Code:*

public static boolean Java_PKCS7Sign(File inputFile, File outputFile,
PrivateKey privateKey, X509Certificate certificate, String
signingAlgorithm) {
    try {
        String inputFilePath = inputFile.getAbsolutePath();
        String outputFilePath = outputFile.getAbsolutePath();

        byte arr[] = android.security.Credentials.convertToPem(certificate);
        InputStream certIs = new  ByteArrayInputStream(arr);
        OpenSSLX509Certificate openSSLcert =
OpenSSLX509Certificate.fromX509PemInputStream(certIs);
        byte openSSLcertEncoded[] = openSSLcert.getEncoded();
        long signCertRef = NativeCrypto.d2i_X509(openSSLcertEncoded);

        OpenSSLKey oKey = OpenSSLKey.fromPrivateKey(privateKey);
        long evpKeyRef = oKey.getPkeyContext();

        //boolean res = PKCS7Sign(signCertRef, pkeyRef, certs, bioRef,
flags, a, b)
        long arr1[] = new long[0];
        return PKCS7Sign(inputFilePath, signCertRef, evpKeyRef, arr1,
outputFilePath);
    } catch (Exception e) {
        e.printStackTrace();
    }


    return false;
}

In the above code PKCS7Sign is a JNI call to OpenSSL. And the flags used
are for signing are: int flgs = PKCS7_STREAM | PKCS7_DETACHED |
PKCS7_BINARY ;

*Encrypt Code:*

public static boolean Java_PKCS7encrypt(File inputData, File output,
X509Certificate[] recipientCertificates, String encryptionAlgorithm) {
    if(!inputData.exists() || !output.exists())
        return false;

    try {
        fis = new FileInputStream(inputData);
        OpenSSLBIOInputStream bis = new OpenSSLBIOInputStream(fis);
        long bioRef = NativeCrypto.create_BIO_InputStream(bis);

        int certsRefArrLength = recipientCertificates.length;
        long certsRefArr[] = new long[certsRefArrLength];
        for (int i = 0; i < certsRefArrLength; i++) {
            byte arr[] =
android.security.Credentials.convertToPem(recipientCertificates[i]);
            InputStream certIs = new  ByteArrayInputStream(arr);
            OpenSSLX509Certificate openSSLcert =
OpenSSLX509Certificate.fromX509PemInputStream(certIs);
            byte openSSLcertEncoded[] = openSSLcert.getEncoded();
            certsRefArr[i] = NativeCrypto.d2i_X509(openSSLcertEncoded);
        }

        String outputFilePath = output.getAbsolutePath();

        return PKCS7encrypt(bioRef, certsRefArr, outputFilePath,
encryptionAlgorithm);


    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (CertificateEncodingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return false;
}

Same as in case of sign PKCS7encrypt is a JNI call to OpenSSL. And flags
used are:

int flags = PKCS7_STREAM | PKCS7_BINARY;

And cipher used for encryption is cipher = EVP_rc2_40_cbc();

Any pointers about my mistake?