cmd/age-keyserver: hash age public key to prevent log poisoning

Author: FiloSottile

cmd/age-keylookup/main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"crypto/sha256"
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
@@ -138,8 +139,9 @@ func lookupKey(serverURL string, v note.Verifier, vrfKey *vrf.PublicKey, email s
 	}
 
 	// Verify spicy signature
-	vrfHashB64 := base64.StdEncoding.EncodeToString(vrfHash)
-	entry := fmt.Appendf(nil, "%s\n%s\n", vrfHashB64, result.Pubkey)
+	h := sha256.New()
+	h.Write([]byte(result.Pubkey))
+	entry := h.Sum(vrfHash) // vrf-r255(email) || SHA-256(pubkey)
 	if err := torchwood.VerifyProof(v.Name(), func(b []byte) (*note.Note, error) {
 		return note.Open(b, note.VerifierList(v))
 	}, tlog.RecordHash(entry), []byte(result.Proof)); err != nil {

cmd/age-keylookup/main_test.go

@@ -3,7 +3,7 @@ package main
 import (
 	"context"
 	"crypto/rand"
-	"encoding/base64"
+	"crypto/sha256"
 	"encoding/json"
 	"fmt"
 	"html/template"
@@ -150,10 +150,11 @@ func TestCLIDirect(t *testing.T) {
 
 		// Compute VRF hash and proof
 		vrfProof := srv.vrf.Prove([]byte(testEmail))
-		vrfHash := base64.StdEncoding.EncodeToString(vrfProof.Hash())
 
 		// Add to transparency log
-		entry := tessera.NewEntry(fmt.Appendf(nil, "%s\n%s\n", vrfHash, testKey))
+		h := sha256.New()
+		h.Write([]byte(testKey))
+		entry := tessera.NewEntry(h.Sum(vrfProof.Hash())) // vrf-r255(email) || SHA-256(pubkey)
 		index, _, err := srv.awaiter.Await(ctx, srv.appender.Add(ctx, entry))
 		if err != nil {
 			t.Fatal(err)
@@ -219,10 +220,11 @@ func TestCLIDirect(t *testing.T) {
 
 			// Compute VRF hash and proof
 			vrfProof := srv.vrf.Prove([]byte(email))
-			vrfHash := base64.StdEncoding.EncodeToString(vrfProof.Hash())
 
 			// Add to transparency log
-			entry := tessera.NewEntry(fmt.Appendf(nil, "%s\n%s\n", vrfHash, testKey))
+			h := sha256.New()
+			h.Write([]byte(testKey))
+			entry := tessera.NewEntry(h.Sum(vrfProof.Hash())) // vrf-r255(email) || SHA-256(pubkey)
 			index, _, err := srv.awaiter.Await(ctx, srv.appender.Add(ctx, entry))
 			if err != nil {
 				t.Fatal(err)
@@ -562,10 +564,11 @@ func insertKeyCmd() script.Cmd {
 
 			// Compute VRF hash and proof
 			vrfProof := globalEnv.server.vrf.Prove([]byte(email))
-			vrfHash := base64.StdEncoding.EncodeToString(vrfProof.Hash())
 
 			// Add to transparency log
-			entry := tessera.NewEntry(fmt.Appendf(nil, "%s\n%s\n", vrfHash, pubkey))
+			h := sha256.New()
+			h.Write([]byte(pubkey))
+			entry := tessera.NewEntry(h.Sum(vrfProof.Hash())) // vrf-r255(email) || SHA-256(pubkey)
 			index, _, err := globalEnv.server.awaiter.Await(ctx, globalEnv.server.appender.Add(ctx, entry))
 			if err != nil {
 				return nil, fmt.Errorf("failed to add to transparency log: %w", err)

cmd/age-keyserver-keygen/keygen.go

@@ -25,8 +25,8 @@ func main() {
 
 	vrfKey := vrf.GenerateKey()
 
-	fmt.Printf("Private key (for LOG_KEY in keyserver): %s\n", skey)
-	fmt.Printf("Private VRF key (for VRF_KEY in keyserver): %s\n", base64.StdEncoding.EncodeToString(vrfKey.Bytes()))
+	fmt.Printf("Private key (for LOG_KEY in age-keyserver): %s\n", skey)
+	fmt.Printf("Private VRF key (for VRF_KEY in age-keyserver): %s\n", base64.StdEncoding.EncodeToString(vrfKey.Bytes()))
 	fmt.Printf("Public key (for AGE_KEYSERVER_PUBKEY in age-keylookup): %s\n", vkey)
 	fmt.Printf("Public VRF key (for AGE_KEYSERVER_VRFKEY in age-keylookup): %s\n", base64.StdEncoding.EncodeToString(vrfKey.PublicKey().Bytes()))
 }

cmd/age-keyserver/main.go

@@ -332,10 +332,11 @@ func (s *Server) handleSetKey(w http.ResponseWriter, r *http.Request) {
 
 		// Compute VRF hash and proof
 		vrfProof := s.vrf.Prove([]byte(email))
-		vrfHash := base64.StdEncoding.EncodeToString(vrfProof.Hash())
 
 		// Add to transparency log
-		entry := tessera.NewEntry(fmt.Appendf(nil, "%s\n%s\n", vrfHash, pubkey))
+		h := sha256.New()
+		h.Write([]byte(pubkey))
+		entry := tessera.NewEntry(h.Sum(vrfProof.Hash())) // vrf-r255(email) || SHA-256(pubkey)
 		index, _, err := s.awaiter.Await(r.Context(), s.appender.Add(r.Context(), entry))
 		if err != nil {
 			http.Error(w, "Failed to add to transparency log", http.StatusInternalServerError)