Add Prompt

[ChrisMissal]

Sometimes I'll have tasks in my builds that are run manually. These may occasionally require data that I don't want to commit. One example would be publishing to NuGet, but in doing so, prompts for an API key.

An example in gulp: https://www.npmjs.com/package/gulp-prompt

[patriksvensson]

Could be very useful for scenarios as the one you mention!

[yvschmid]

@ChrisMissal @patriksvensson
I was thinking to give this one a go. If I get it right, you want to be able to do something like this:

NuGetPush(packagePath, new NuGetPushSettings {
    ApiKey = Prompt("Enter api key for NuGetPush:")
});

So if we ignore all the fancy stuff gulp-prompt can do for the moment this would be a very simple API with just a single method:

string Prompt(string message)

Some thoughts about the implementation:

• we need access to the console (read and write), should we use the Cake.Core.IConsole and add a ReadLine() method?
• Is there a better way to get access to the console than adding it to the CakeContext?

[patriksvensson]

I see little use for adding the IConsole to ICakeContext. Especially adding functionality for something that require interaction from the user.

Since you know that the user runs in interactive mode (otherwise you should not display an prompt), you could use the Console directly.

if(Environment.UserInteractive)
{
   Console.WriteLine("What is you name?");
   var name = Console.ReadLine();
}

[patriksvensson]

That said, A new property UserInteractive should be added the the ICakeEnvironment.

[patriksvensson]

I'm not against adding IConsole to the ICakeContext, but this abstraction is mostly there for unit testing at the moment. I think that a Prompt alias must throw if it's not running in user interactive mode.

[patriksvensson]

@devlead What do you think about this?

[yvschmid]

Throwing if not running in user interactive mode sounds very reasonable 👍

[devlead]

I'm on the fence, can see the use case presented, for fallback scenarios i.e. environment variable / argument missing and some other scenarios. But impotent as stated that it fails if it runs in any server triggered/scheduled scenario.

[patriksvensson]

I agree. Maybe this is better suited as an addin.

[devlead]

Well it could definitely start as such.

[ChrisMissal]

@yvschmid

If I get it right, you want to be able to do something like this

Exactly!

@patriksvensson @devlead

I agree. Maybe this is better suited as an addin.

👍

[yvschmid]

I've just added a very basic implementation: https://github.com/yvschmid/Cake.Prompt

This will prevent it from throwing:

cake.exe build.cake -interactive=true

@patriksvensson Should we still add the Environment.UserInteractive property?

[xclayl]

Prompting seems to be used for secrets -- why not do something specific for secrets? I'm thinking of the following:

var secretKey = Argument("encryption_key", null as string) ?? EnvironmentVariable("encryption_key");
var dbPassword = PromptOrDecryptAesSecret("db_password", "Please enter the DB password:", secretKey);

PromptOrDecryptAesSecret() would look in a folder called ".cake.secrets" for the file "db_password.aes". If not found, it'd prompt and then save the secret in db_password.aes for later.

You probably could use async/await to detect if you're in a non-interactive session -- if there is no activity for 30 seconds, throw an exception.

[xclayl]

This is what I did if anyone else is interested. It works like I described above.

You can put your password in a password manager and then run the following after opening a powershell prompt:

$env:encryption_key = "your password as long as you want"

Below is the cake code:

var IsValidFilename = new Func<string, bool>((name) => {
    var invalidChars = from iv in System.IO.Path.GetInvalidFileNameChars()
    join nc in (name + ".aes") on iv equals nc
    select iv;

    return !invalidChars.Any();
});

var Decrypt = new Func<FileInfo, string, string>((file, encryptionPassword) => {

    if (!file.Exists) {
        return null;
    }


    byte[] cipherBytes = System.IO.File.ReadAllBytes(file.FullName);

    using (var cipher = System.Security.Cryptography.AesManaged.Create())
    {

        var salt = Convert.FromBase64String("mBLf3umGnNA=");

        using(var pdb = new System.Security.Cryptography.Rfc2898DeriveBytes(encryptionPassword, salt)) {
            cipher.Key = pdb.GetBytes(32);
            cipher.IV = pdb.GetBytes(16);
        }
        using (var ms = new MemoryStream())
        {
            using (var cs = new System.Security.Cryptography.CryptoStream(ms, cipher.CreateDecryptor(), System.Security.Cryptography.CryptoStreamMode.Write))
            {
                cs.Write(cipherBytes, 0, cipherBytes.Length);
                cs.Close();
            }
            return Encoding.UTF8.GetString(ms.ToArray());
        }
    }

});




var Encrypt = new Action<string, FileInfo, string>((unencrypted, fileInfo, encryptionPassword) => {


    using (var cipher = System.Security.Cryptography.AesManaged.Create())
    {

        var salt = Convert.FromBase64String("mBLf3umGnNA=");

        using(var pdb = new System.Security.Cryptography.Rfc2898DeriveBytes(encryptionPassword, salt)) {
            cipher.Key = pdb.GetBytes(32);
            cipher.IV = pdb.GetBytes(16);
        }


       var valueBytes = Encoding.UTF8.GetBytes(unencrypted);


        using (var encryptor = cipher.CreateEncryptor()) {
            using (var to = fileInfo.OpenWrite()) {
                using (var writer = new System.Security.Cryptography.CryptoStream(to, encryptor, System.Security.Cryptography.CryptoStreamMode.Write)) {
                    writer.Write(valueBytes, 0, valueBytes.Length);
                    writer.FlushFinalBlock();
                }
            }
        }

    }

});

var AskForSecret = new Func<string, string>((prompt) => {


    System.Console.WriteLine(prompt);


    string response = null;

    System.Threading.Tasks.Task.Run<Task>(() => { 
        return System.Threading.Tasks.Task.WhenAny(
            new System.Threading.Tasks.Task[] {
                System.Threading.Tasks.Task.Run(() => {
                    response = Console.ReadLine();
                }),
                System.Threading.Tasks.Task.Delay(TimeSpan.FromSeconds(30))
            }
        );
    }).Wait();

    if (response == null) {
        throw new Exception("No response in 30 seconds, so I assume this is a non-interactive session.");
    }

    return response;
});

var PromptOrDecryptAesSecret = new Func<string, string, string, string>((name, prompt, encryptionPassword) => {

    if (!IsValidFilename(name)) {
        throw new Exception("The name, " + name + ", is not a valid filename.");
    }

    if (encryptionPassword == null) {
        throw new Exception("The encryption password is null.");
    }


    var d = new DirectoryInfo(".cake.secrets");

    if (!d.Exists) {
        d.Create();
    }



    var fileInfo = new FileInfo(System.IO.Path.Combine(d.FullName, name + ".aes"));

    var unencrypted = Decrypt(fileInfo, encryptionPassword);

    if (unencrypted == null) {

        unencrypted = AskForSecret(prompt);

        Encrypt(unencrypted, fileInfo, encryptionPassword);
    }

    return unencrypted;
});