v0.1.0-alpha

Changes:
- Implement bootstrapping library for managing several concurrent internal services
- Refactor concurrency model for connections/logical clients and their associated I/O
- Refactor server context singleton
- Refactor error handling
    - Most errors are now gracefully sent to the FSD client directly encoded as an $ER packet,
      enhancing visibility and debugging
    - Most errors are now rightfully treated as non-fatal
- Refactor package/dependency graph
- Refactor calling conventions/interfaces for many packages
- Refactor database package
- Refactor post office

Features:
- Add VATSIM-esque HTTP/JSON "data feed"
- Add ephemeral in-memory database option
- Add user management REST API
- Add improved web interface
- Add MySQL support (drop SQLite support)

protocol/vatsimauth/vatsimauth.go

@@ -0,0 +1,93 @@
+package vatsimauth
+
+import (
+	"crypto/md5"
+	"crypto/rand"
+	"encoding/hex"
+	"io"
+	"strings"
+)
+
+var Keys = map[uint16]string{
+	8464:  "945507c4c50222c34687e742729252e6",
+	10452: "0ad74157c7f449c216bfed04f3af9fb9",
+	27095: "3518a62c421937ffa46ac3316957da43",
+	33456: "52d9343020e9c7d0c6b04b0cca20ad3b",
+	35044: "fe28334fb753cf0e3d19942197b9ce3e",
+	55538: "ImuL1WbbhVuD8d3MuKpWn2rrLZRa9iVP",
+	56862: "3518a62c421937ffa46ac3316957da43",
+}
+
+type VatsimAuth struct {
+	clientID uint16
+	init     string
+	state    string
+}
+
+func NewVatsimAuth(clientID uint16, privateKey string) *VatsimAuth {
+	return &VatsimAuth{
+		clientID: clientID,
+		init:     "",
+		state:    privateKey,
+	}
+}
+
+// SetInitialChallenge stores the initial challenge for this authentication state. This should be called once before running GenerateResponse
+func (v *VatsimAuth) SetInitialChallenge(initialChallenge string) {
+	v.init = v.GenerateResponse(initialChallenge)
+	v.state = v.init
+}
+
+// GenerateResponse returns the response for the provided challenge.
+func (v *VatsimAuth) GenerateResponse(challenge string) string {
+	c1, c2 := challenge[0:(len(challenge)/2)], challenge[(len(challenge)/2):]
+
+	if (v.clientID & 1) == 1 {
+		c1, c2 = c2, c1
+	}
+
+	s1, s2, s3 := v.state[0:12], v.state[12:22], v.state[22:32]
+
+	h := strings.Builder{}
+	h.Grow(len(s1) + len(s2) + len(s3) + len(c1) + len(c2))
+
+	switch v.clientID % 3 {
+	case 0:
+		h.WriteString(s1)
+		h.WriteString(c1)
+		h.WriteString(s2)
+		h.WriteString(c2)
+		h.WriteString(s3)
+	case 1:
+		h.WriteString(s2)
+		h.WriteString(c1)
+		h.WriteString(s3)
+		h.WriteString(c2)
+		h.WriteString(s1)
+	default:
+		h.WriteString(s3)
+		h.WriteString(c1)
+		h.WriteString(s1)
+		h.WriteString(c2)
+		h.WriteString(s2)
+	}
+
+	hash := md5.Sum([]byte(h.String()))
+	return hex.EncodeToString(hash[:])
+}
+
+// UpdateState updates this authentication state with a response hash. This is conventionally called with the return value of GenerateResponse
+func (v *VatsimAuth) UpdateState(hash string) {
+	newStateHash := md5.Sum([]byte(v.init + hash))
+	v.state = hex.EncodeToString(newStateHash[:])
+}
+
+// GenerateChallenge returns a cryptographically secure random challenge string
+func GenerateChallenge() (string, error) {
+	challenge := make([]byte, 8)
+	if _, err := io.ReadFull(rand.Reader, challenge); err != nil {
+		return "", err
+	}
+
+	return hex.EncodeToString(challenge), nil
+}

protocol/vatsimauth/vatsimauth_test.go

@@ -0,0 +1,35 @@
+package vatsimauth
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestVatsimAuth(t *testing.T) {
+
+	// vPilot clientID and key
+	v := NewVatsimAuth(35044, Keys[35044])
+	assert.NotNil(t, v)
+
+	// Initial challenge
+	// $DISERVER:CLIENT:VATSIM FSD V3.43:30984979d8caed23
+	v.SetInitialChallenge("30984979d8caed23")
+
+	// First challenge from server
+	// $ZCSERVER:N12345:de6acb8e
+	res := v.GenerateResponse("de6acb8e")
+
+	// Expected response:
+	// $ZRN12345:SERVER:f8ee97157f66455ed6108fccef6ccf5f
+	assert.Equal(t, "f8ee97157f66455ed6108fccef6ccf5f", res)
+	v.UpdateState(res)
+
+	// Second challenge from server
+	// $ZCSERVER:N12345:65b479573b0e
+	res = v.GenerateResponse("65b479573b0e")
+
+	// Expected response
+	// $ZRN12345:SERVER:8953f545c4e0ffd20943ad89b8ddd087
+	assert.Equal(t, "8953f545c4e0ffd20943ad89b8ddd087", res)
+	v.UpdateState(res)
+}