From a1c91b3e85c8b6f18f04dc5c361a87f82c927bea Mon Sep 17 00:00:00 2001
From: Markus Rudy <mr@edgeless.systems>
Date: Fri, 14 Jun 2024 20:42:51 +0200
Subject: [PATCH] coordinator: make history thread-safe

---
 coordinator/history/history.go | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/coordinator/history/history.go b/coordinator/history/history.go
index 535d33063..8ea762865 100644
--- a/coordinator/history/history.go
+++ b/coordinator/history/history.go
@@ -13,6 +13,7 @@ import (
 	"fmt"
 	"hash"
 	"os"
+	"sync/atomic"
 
 	"github.com/spf13/afero"
 )
@@ -28,7 +29,7 @@ const (
 type History struct {
 	store      Store
 	hashFun    func() hash.Hash
-	signingKey *ecdsa.PrivateKey
+	signingKey atomic.Pointer[ecdsa.PrivateKey]
 }
 
 // New creates a new History backed by the default filesystem store.
@@ -55,7 +56,7 @@ func NewWithStore(store Store) *History {
 
 // ConfigureSigningKey sets the signing key for validation and signing of the protected history parts.
 func (h *History) ConfigureSigningKey(signingKey *ecdsa.PrivateKey) {
-	h.signingKey = signingKey
+	h.signingKey.Store(signingKey)
 }
 
 // GetManifest returns the manifest for the given hash.
@@ -98,7 +99,8 @@ func (h *History) SetTransition(transition *Transition) ([HashSize]byte, error)
 
 // GetLatest returns the verified transition for the given hash.
 func (h *History) GetLatest() (*LatestTransition, error) {
-	if h.signingKey == nil {
+	signingKey := h.signingKey.Load()
+	if signingKey == nil {
 		return nil, errors.New("signing key not configured")
 	}
 	transitionBytes, err := h.store.Get("transitions/latest")
@@ -109,7 +111,7 @@ func (h *History) GetLatest() (*LatestTransition, error) {
 	if err := latestTransition.unmarshalBinary(transitionBytes); err != nil {
 		return nil, fmt.Errorf("unmarshaling latest transition: %w", err)
 	}
-	if err := latestTransition.verify(&h.signingKey.PublicKey); err != nil {
+	if err := latestTransition.verify(&signingKey.PublicKey); err != nil {
 		return nil, fmt.Errorf("verifying latest transition: %w", err)
 	}
 	return &latestTransition, nil
@@ -129,10 +131,11 @@ func (h *History) HasLatest() (bool, error) {
 
 // SetLatest signs and sets the latest transition if the current latest is equal to oldT.
 func (h *History) SetLatest(oldT, newT *LatestTransition) error {
-	if h.signingKey == nil {
+	signingKey := h.signingKey.Load()
+	if signingKey == nil {
 		return errors.New("signing key not configured")
 	}
-	if err := newT.sign(h.signingKey); err != nil {
+	if err := newT.sign(signingKey); err != nil {
 		return fmt.Errorf("signing latest transition: %w", err)
 	}
 	if err := h.store.CompareAndSwap("transitions/latest", oldT.marshalBinary(), newT.marshalBinary()); err != nil {