1 files changed, 116 insertions, 51 deletions

diff --git a/server/dht.go b/server/dht.go
index e5d96f1..8292280 100644
--- a/server/dht.go
+++ b/server/dht.go
@@ -1,16 +1,27 @@
 package main
 
 import (
-	"crypto/ed25519"
+	"bytes"
+	"crypto/sha256"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"io"
 	"log"
 	"net/http"
 	"sort"
+	"strconv"
 	"strings"
+	"sync"
+	"time"
 )
 
+// Get the sha256sum of string as a URL-safe unpadded base64 string
+func sha256sum(s string) string {
+	b := sha256.Sum256([]byte(s))
+	return base64.RawURLEncoding.EncodeToString(b[:])
+}
+
 // Try to peer with another server
 func addPeer(peer string) error {
 	peerHash := sha256sum(peer)
@@ -71,69 +82,123 @@ func peerHandler(w http.ResponseWriter, r *http.Request) {
 	go addPeer(peer)
 }
 
-// Handle DHT requests
-func dhtHandler(w http.ResponseWriter, r *http.Request) {
-	key := r.URL.String()[5:]
-	keyHash := sha256sum(key)
-	pubKey := asPubKey(key)
-	fmt.Println(key, keyHash, pubKey)
-	mu.Lock()
-	keyPos := sort.SearchStrings(peerHashes, keyHash)
+// Find the position of a key in the DHT
+func keyPos(key string) int {
+	keyPos := sort.SearchStrings(peerHashes, sha256sum(key))
 	if keyPos < myPos {
 		keyPos += len(peerHashes)
 	}
-	mu.Unlock()
-	if r.Method == "GET" {
-		if keyPos - myPos < 5 {
-			mu.Lock()
-			if val, ok := kvstore[key]; ok {
-				w.Write([]byte(val))
-			} else {
-				w.WriteHeader(http.StatusNotFound)
-			}
-			mu.Unlock()
-		} else {
-			for i := 0; i < 5 && i < len(peerHashes); i++ {
-				j := hashToDomain[peerHashes[(keyPos+i)%len(peerHashes)]]
-				go func() string {
-					resp, err := http.Get(j + r.URL.String())
-					if err != nil {
-						return ""
-					}
-					b, err := io.ReadAll(resp.Body)
-					if err != nil {
-						return ""
-					}
-					return string(b)
-				}()
+	return keyPos
+}
+
 
+// Get the value for a key from the DHT
+func dhtGet(key string) ([]byte, error) {
+	keyPos := keyPos(key)
+	var wg sync.WaitGroup
+	var ret []byte
+	bestTime := 0
+	for i := 0; i < 5 && i < len(peerHashes); i++ {
+		wg.Add(1)
+		j := hashToDomain[peerHashes[(keyPos+i)%len(peerHashes)]]
+		go func() {
+			defer wg.Done()
+			resp, err := http.Get(j + "/dht/" + key + "?direct")
+			if err != nil {
+				// TODO: Remove this server from DHT?
+				// For sanity reasons this might be a bad idea
+				return
 			}
+			b, err := io.ReadAll(resp.Body)
+			if err != nil {
+				return
+			}
+			err = verify(key, b)
+			if err != nil {
+				return
+			}
+			valTime, err := strconv.Atoi(strings.Split(string(b), "\n")[0])
+			if err != nil {
+				return
+			}
+			if ret == nil || valTime > bestTime {
+				ret = b
+				bestTime = valTime
+			}
+		}()
+	}
+	wg.Wait()
+	if ret == nil {
+		return nil, errors.New("id not in kvstore")
+	}
+	return ret, nil
+}
 
+// Put a key-value pair into the DHT
+func dhtPut(key string, val []byte) error {
+	err := verify(key, val)
+	if err != nil {
+		return err
+	}
+	keyPos := keyPos(key)
+	for i := 0; i < 5 && i < len(peerHashes); i++ {
+		j := hashToDomain[peerHashes[(keyPos+i)%len(peerHashes)]]
+		go func() {
+			http.Post(j + "/dht/" + key + "?direct", "application/octet-stream", bytes.NewBuffer(val))
+		}()
+	}
+	return nil
+}
 
+// Handle DHT requests
+func dhtHandler(w http.ResponseWriter, r *http.Request) {
+	key := r.URL.Path[5:]
+	r.ParseForm()
+	if r.Form.Get("direct") != "" {
+		// Directly modify kvstore
+		if keyPos(key) - myPos >= 5 {
+			w.WriteHeader(http.StatusNotFound)
+			return
+		}
+		if r.Method == "GET" {
+			mu.Lock()
+			val, ok := kvstore[key + fmt.Sprint(time.Now().Unix() / 600)]
+			mu.Unlock()
+			if !ok || verify(key, val) != nil {
+				w.WriteHeader(http.StatusNotFound)
+				return
+			}
+			w.Write(val)
+		} else if r.Method == "POST" {
+			val, err := io.ReadAll(r.Body)
+			if err != nil {
+				w.WriteHeader(http.StatusInternalServerError)
+				return
+			}
+			mu.Lock()
+			kvstore[key + fmt.Sprint(time.Now().Unix() / 600)] = val
+			mu.Unlock()
 		}
-	} else if r.Method == "PUT" {
-		// Read request body
-		b, err := io.ReadAll(r.Body)
+		return
+	}
+	if r.Method == "GET" {
+		val, err := dhtGet(key)
 		if err != nil {
-			w.WriteHeader(http.StatusInternalServerError)
+			w.WriteHeader(http.StatusNotFound)
 			return
 		}
-		// Extract signature
-		valSplit := strings.Split(string(b), "\n")
-		sig := valSplit[len(valSplit)-1]
-		// Verify signature
-		if !ed25519.Verify(pubKey, b[:len(b)-len(sig)-1], []byte(sig)) {
-			w.WriteHeader(http.StatusUnauthorized)
+		w.Write([]byte(val))
+	} else if r.Method == "POST" {
+		val, err := io.ReadAll(r.Body)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
 			return
 		}
-		if keyPos - myPos < 5 {
-			mu.Lock()
-			kvstore[key] = string(b[:len(b)-len(sig)-1])
-			mu.Unlock()
-		} else {
-
+		err = dhtPut(key, val)
+		if err != nil {
+			w.WriteHeader(http.StatusInternalServerError)
+			return
 		}
-	} else {
-		w.WriteHeader(http.StatusMethodNotAllowed)
+		w.WriteHeader(http.StatusOK)
 	}
 }