Calling GnuPG in Java via a Runtime Process to encrypt and decrypt files - Decrypt always hangs

Question

NOTE: Coming back to this later as I\'ve been unable to find a working solution. Draining the input streams manually instead of using BufferedReaders doesn

Answer 1

The following code works with GNUPG 2.1.X

public static boolean gpgEncrypt(String file, String recipient,
        String outputFile) {
    boolean success = true;
    StringBuilder gpgCommand = new StringBuilder("gpg --recipient \"");
    gpgCommand.append(recipient).append("\" --output \"")
            .append(outputFile).append("\" --yes --encrypt \"");
    gpgCommand.append(file).append("\"");

    System.out.println("ENCRYPT COMMAND: " + gpgCommand);
    try {
        Process gpgProcess = Runtime.getRuntime().exec(
                gpgCommand.toString());

        BufferedReader gpgOutput = new BufferedReader(
                new InputStreamReader(gpgProcess.getInputStream()));
        BufferedWriter gpgInput = new BufferedWriter(
                new OutputStreamWriter(gpgProcess.getOutputStream()));
        BufferedReader gpgErrorOutput = new BufferedReader(
                new InputStreamReader(gpgProcess.getErrorStream()));

        boolean executing = true;

        while (executing) {
            try {
                int exitValue = gpgProcess.exitValue();

                if (gpgErrorOutput.ready()) {
                    String error = getStreamText(gpgErrorOutput);
                    System.err.println(error);
                    success = false;
                    break;
                } else if (gpgOutput.ready()) {
                    System.out.println(getStreamText(gpgOutput));
                }

                executing = false;
            } catch (Exception e) {
                // The process is not yet ready to exit. Take a break and
                // try again.
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e1) {
                    System.err.println("This thread has insomnia: "
                            + e1.getMessage());
                }
            }
        }
    } catch (IOException e) {
        System.err.println("Error running GPG via runtime: "
                + e.getMessage());
        success = false;
    }

    return success;
}

// gpg --pinentry-mode=loopback --passphrase "siv_test" -d -o
// "sample_enc_data_op.txt" "sample_enc_data_input.gpg"

public static String gpgDecrypt(String file, String passphrase,
        String outputfile) {
    String result = null;
    StringBuilder command = new StringBuilder(
            "gpg --pinentry-mode=loopback --passphrase \"");
    command.append(passphrase).append("\" -d -o \"").append(outputfile)

    .append("\" --yes \"").append(file)

    .append("\"");
    System.out.println("DECRYPT COMMAND: " + command.toString());
    try {

        Process gpgProcess = Runtime.getRuntime().exec(command.toString());

        BufferedReader gpgOutput = new BufferedReader(
                new InputStreamReader(gpgProcess.getInputStream()));
        BufferedReader gpgErrorOutput = new BufferedReader(
                new InputStreamReader(gpgProcess.getErrorStream()));
        BufferedWriter gpgInput = new BufferedWriter(
                new OutputStreamWriter(gpgProcess.getOutputStream()));

        boolean executing = true;

        while (executing) {
            try {
                if (gpgErrorOutput.ready()) {
                    result = getStreamText(gpgErrorOutput);
                    System.err.println(result);
                    break;
                } else if (gpgOutput.ready()) {
                    result = getStreamText(gpgOutput);
                }
                String line = null;
                while ((line = gpgOutput.readLine()) != null) {
                    System.out.println(line);
                }
                int exitValue = gpgProcess.exitValue();
                System.out.println("EXIT: " + exitValue);

                executing = false;
            } catch (IllegalThreadStateException e) {
                System.out.println("Not yet ready.  Stream status: "
                        + gpgOutput.ready() + ", error: "
                        + gpgErrorOutput.ready());

                try {
                    Thread.sleep(100);
                } catch (InterruptedException e1) {
                    System.err.println("This thread has insomnia: "
                            + e1.getMessage());
                }
            }
        }
    } catch (IOException e) {
        System.err
                .println("Unable to execute GPG decrypt command via command line: "
                        + e.getMessage());
    }

    return result;
}

private static String getStreamText(BufferedReader reader)
        throws IOException {
    StringBuilder result = new StringBuilder();
    try {
        while (reader.ready()) {
            result.append(reader.readLine());
            if (reader.ready()) {
                result.append("\n");
            }
        }
    } catch (IOException ioe) {
        System.err.println("Error while reading the stream: "
                + ioe.getMessage());
        throw ioe;
    }
    return result.toString();
}