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package main
import (
"crypto/ed25519"
"encoding/base64"
"encoding/gob"
"errors"
"net/http"
"os"
"strings"
)
type user struct {
dhtVal []byte
phase int64
servers []string
log []string
nextIndex map[string]int
}
var users map[string]user
// Verify that a body was signed by this ID
func verify(id string, body []byte) error {
b, err := base64.RawURLEncoding.DecodeString(id)
if err != nil {
return err
}
if len(body) < ed25519.SignatureSize {
return errors.New("body too short")
}
message := body[:len(body)-ed25519.SignatureSize]
sig := body[len(body)-ed25519.SignatureSize:]
if !ed25519.Verify(ed25519.PublicKey(b), message, sig) {
return errors.New("signature verification failed")
}
return nil
}
// Persist a user's data to disk
func persist(id string) {
writer, err := os.OpenFile(dataDir+"/"+id+"/gob", os.O_CREATE|os.O_WRONLY, 0644)
if err != nil {
return
}
enc := gob.NewEncoder(writer)
enc.Encode(users[id])
}
// Reconfigure a user based on a DHT get
func reconfigure(id string, dhtVal []byte) {
mu.Lock()
defer mu.Unlock()
user := users[id]
if timestamp(dhtVal) < timestamp(user.dhtVal) {
return
}
user.dhtVal = dhtVal
servers := strings.Split(string(dhtVal[8:len(dhtVal)-ed25519.SignatureSize]), "\n")
if servers[0] == me {
if user.nextIndex == nil {
user.nextIndex = make(map[string]int)
}
for _, server := range servers {
if _, ok := user.nextIndex[server]; !ok {
user.nextIndex[server] = len(user.log)
go replicate(id, server)
}
}
}
inServers := false
for _, server := range servers {
if server == me {
inServers = true
}
}
persist(id)
if !inServers {
delete(users, id)
_ = os.RemoveAll(id)
}
}
// Handle user configuration changes
func userHandler(w http.ResponseWriter, r *http.Request) {
id := r.URL.Path[6:]
// Resolve ID to server list
val := dhtGet(id, false)
if verify(id, val) != nil {
w.WriteHeader(http.StatusNotFound)
return
}
mu.Lock()
if _, ok := users[id]; !ok {
// Add user
users[id] = user{dhtVal: val}
os.Mkdir(dataDir+"/"+id, 0755)
persist(id)
}
mu.Unlock()
reconfigure(id, val)
w.WriteHeader(http.StatusOK)
}
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