ERAF Go SDK

This is an SDK to read, edit and create Entity-related Authentication Format files, entity meaning a person, a device, an app, an endpoint or whatever it is you want to authenticate.

There is of course some slight overhead. The data fields, like Certificate or Nonce can all be empty, but there is always space reserved for headers, even if no data has been set yet. This overhead currently amounts to 50 bytes. If this is acceptable for your use case, please give it a try and send feedback if it works out for you.

This library is now considered stable.

Due tests

Tested successfully on

• windows/amd64
• linux/amd64
• darwin/amd64

Not yet tested

• Tests on other OS/Arch combinations (Issue #4)
• Integration tests in example applications

Purpose

There are a lot of different ways to authenticate an entity. Using username and password, a bearer token or a certificate are just a few examples. This format is for bundling different authentication information into a single, portable file, easily transmittable over the line, e.g. via HTTP or email. You can for example use the Nonce and Tag fields to save meta data for AES encryption of the data (e.g. the certificate) and decrypt the content at the recipient's device. This is just one example of the many possible use cases.

Installation

Install via go get github.com/KaiserWerk/ERAF-Go-SDK@vX.X.X and add the import line eraf "github.com/KaiserWerk/ERAF-Go-SDK to your Go file(s).

If you want the bleeding edge version from the master branch, just drop the @version.

Usage

Creating and Marshalling

First, create a new *eraf.Container and fill it with data. Set calls for setting fields can be chained.

cert, _ := ioutil.ReadFile("localhost.cert")
key, _ := ioutil.ReadFile("localhost.key")
sig := sha256.Sum256(cert)

container := eraf.New()
container.
	SetCertificate(cert).
	SetPrivateKey(key).
	SetSignature(sig[:])

Available fields (that means data blocks) for you to use are as follows:

• VersionMajor
• VersionMinor
• VersionPatch
• Nonce
• Tag
• SerialNumber
• Identifier
• Certificate
• PrivateKey
• Email
• Username
• Password
• Token
• Signature
• RootCertificate

There is a setter and getter method for every field. Setters can be chained.

The maximum size (amount of bytes) you can put into any field is that of an unsigned 16 bit integer, that means 65,535 bytes. Byte slices too large will be truncated.

Now, you can either marshal (serialize) the created ERAF container into an io.Writer, directly into a file or into a byte slice:

// into a buffer
var b bytes.Buffer
err := container.Marshal(&b) // as a reference

// or into an http.ResponseWriter
func handler(w http.ResponseWriter, r *http.Request) {
	// some code here
	err := container.Marshal(w)
}

// or into a file, given the file permissions
err := container.MarshalToFile("somefile.eraf", 0744) // the file extension does not matter, actually


// or just get a []byte
var s []byte = container.MarshalBytes()

Reading and Unmarshalling

You can either read an ERAF container from an io.Reader, directly from a file or from a byte slice:

// from an io.Reader
resp, _ := http.Do(req)
defer resp.Body.Close()
container := &eraf.Container{}
err := eraf.Unmarshal(resp.Body, container)

// or directly from a file
container := &eraf.Container{}
err := eraf.UnmarshalFromFile("somefile.eraf", container) // again, the extension doesn't matter

// or from a []byte
container := &eraf.Container{}
err := eraf.UnmarshalBytes(somebytes, container)

The ERAF container implements the io.Reader interface, so you can (for example) supply it as the body parameter for HTTP requests which will read the whole container into the request body:

container := &eraf.Container{}
// set some fields
req, err := http.NewRequest(http.MethodPost, "https://some-url.com/", container)

Obtaining Information

Get some byte amount information:

// Total length
totalLen := container.Len()

// header length (constant)
headerLen := container.HeaderLen()

// payload length
payloadLen := container.PayloadLen()

Obtaining data

Get the version as a properly constructed Semantic Version string:

versionStr := container.GetSemVer() // e.g. 2.14.8

For every Set method there is an equal Get method you can use to read the field from the container, e.g.

n := container.GetNonce()
// or
u := container.GetUsername()
// etc
// ...

You can get just the headers or just the payload for custom parsing as you need:

// Just the headers
headers := container.Headers()

// Just the payload
payload := container.Payload()

Certificate convenience functions

A basic assumption is that all certificate and private key data set is PEM-encoded. For easier certificate handling, there are a few convenience functions:

c := &eraf.Container{}
// set some fields

// obtain the certificate bytes as *x509.Certificate
x509Cert, err := c.GetX509Certificate()

// or certificate and private key combined as *tls.Certificate
tlsCert, err := c.GetTlsCertificate()

// and the root certificate
rootCert, err := c.GetX509RootCertificate()

Encryption & Decryption

Encryption

For every field, there is a method to encrypt it, e.g. for field Email there is a method b, err := container.EncryptEmail(key) which returns the email encrypted with AES using the given key. A nonce is required and must be set beforehand using the SetNonce(n) method, otherwise an error will be returned. The nonce can be reused for subsequent calls. This method does not alter the container.

If you want to encrypt all fields, use err := container.EncryptEverything(key). This method does alter the container. A new nonce will be generated and set automatically. This method replaces all field values with their respective encrypted values.

Decryption

The decryption processes are the exact inverse of the encryption processes. E.g. use email, err := container.DecryptEmail(key) to just decrypt the email.

Otherwise, use err := container.DecryptEverything(key) to simply decrypt every field in place.

Examples

1. Simple example with encryption
2. Extended example with encryption and (un)marshalling
3. Sending an encrypted ERAF container via HTTP and Receiving an ERAF container via HTTP and decrypt it

Tests

Unit tests

Use go test ./... to run all unit tests. Not everything is covered yet. But everything should pass. :)

Benchmark Tests

Use go test -bench=. to run all benchmark tests. Not everything is covered yet.

goos: windows
goarch: amd64
pkg: github.com/KaiserWerk/ERAF-Go-SDK
cpu: AMD FX(tm)-8320 Eight-Core Processor
BenchmarkUnmarshalFromFile-8       15057             83189 ns/op
BenchmarkUnmarshalBytes-8       26284489                43.90 ns/op
BenchmarkMarshal-8               7802852               158.0 ns/op
BenchmarkMarshalToFile-8          139986              8587 ns/op
PASS
coverage: 78.1% of statements