Cache cert verification methods (#871)

* cache cert verification

CheckSignature and Verify are expensive methods, and certificates are
static. Cache the results.

* use atomics

* make sure public key bytes match

* add VerifyWithCache and ResetCache

* cleanup

* use VerifyWithCache

* doc

cert/ca.go

@@ -91,9 +91,15 @@ func (ncp *NebulaCAPool) ResetCertBlocklist() {
 	ncp.certBlocklist = make(map[string]struct{})
 }
 
-// IsBlocklisted returns true if the fingerprint fails to generate or has been explicitly blocklisted
+// NOTE: This uses an internal cache for Sha256Sum() that will not be invalidated
+// automatically if you manually change any fields in the NebulaCertificate.
 func (ncp *NebulaCAPool) IsBlocklisted(c *NebulaCertificate) bool {
-	h, err := c.Sha256Sum()
+	return ncp.isBlocklistedWithCache(c, false)
+}
+
+// IsBlocklisted returns true if the fingerprint fails to generate or has been explicitly blocklisted
+func (ncp *NebulaCAPool) isBlocklistedWithCache(c *NebulaCertificate, useCache bool) bool {
+	h, err := c.sha256SumWithCache(useCache)
 	if err != nil {
 		return true
 	}

cert/cert.go

@@ -17,6 +17,7 @@ import (
 	"math"
 	"math/big"
 	"net"
+	"sync/atomic"
 	"time"
 
 	"golang.org/x/crypto/curve25519"
@@ -42,6 +43,14 @@ const (
 type NebulaCertificate struct {
 	Details   NebulaCertificateDetails
 	Signature []byte
+
+	// the cached hex string of the calculated sha256sum
+	// for VerifyWithCache
+	sha256sum atomic.Pointer[string]
+
+	// the cached public key bytes if they were verified as the signer
+	// for VerifyWithCache
+	signatureVerified atomic.Pointer[[]byte]
 }
 
 type NebulaCertificateDetails struct {
@@ -562,6 +571,27 @@ func (nc *NebulaCertificate) CheckSignature(key []byte) bool {
 	}
 }
 
+// NOTE: This uses an internal cache that will not be invalidated automatically
+// if you manually change any fields in the NebulaCertificate.
+func (nc *NebulaCertificate) checkSignatureWithCache(key []byte, useCache bool) bool {
+	if !useCache {
+		return nc.CheckSignature(key)
+	}
+
+	if v := nc.signatureVerified.Load(); v != nil {
+		return bytes.Equal(*v, key)
+	}
+
+	verified := nc.CheckSignature(key)
+	if verified {
+		keyCopy := make([]byte, len(key))
+		copy(keyCopy, key)
+		nc.signatureVerified.Store(&keyCopy)
+	}
+
+	return verified
+}
+
 // Expired will return true if the nebula cert is too young or too old compared to the provided time, otherwise false
 func (nc *NebulaCertificate) Expired(t time.Time) bool {
 	return nc.Details.NotBefore.After(t) || nc.Details.NotAfter.Before(t)
@@ -569,7 +599,26 @@ func (nc *NebulaCertificate) Expired(t time.Time) bool {
 
 // Verify will ensure a certificate is good in all respects (expiry, group membership, signature, cert blocklist, etc)
 func (nc *NebulaCertificate) Verify(t time.Time, ncp *NebulaCAPool) (bool, error) {
-	if ncp.IsBlocklisted(nc) {
+	return nc.verify(t, ncp, false)
+}
+
+// VerifyWithCache will ensure a certificate is good in all respects (expiry, group membership, signature, cert blocklist, etc)
+//
+// NOTE: This uses an internal cache that will not be invalidated automatically
+// if you manually change any fields in the NebulaCertificate.
+func (nc *NebulaCertificate) VerifyWithCache(t time.Time, ncp *NebulaCAPool) (bool, error) {
+	return nc.verify(t, ncp, true)
+}
+
+// ResetCache resets the cache used by VerifyWithCache.
+func (nc *NebulaCertificate) ResetCache() {
+	nc.sha256sum.Store(nil)
+	nc.signatureVerified.Store(nil)
+}
+
+// Verify will ensure a certificate is good in all respects (expiry, group membership, signature, cert blocklist, etc)
+func (nc *NebulaCertificate) verify(t time.Time, ncp *NebulaCAPool, useCache bool) (bool, error) {
+	if ncp.isBlocklistedWithCache(nc, useCache) {
 		return false, ErrBlockListed
 	}
 
@@ -586,7 +635,7 @@ func (nc *NebulaCertificate) Verify(t time.Time, ncp *NebulaCAPool) (bool, error
 		return false, ErrExpired
 	}
 
-	if !nc.CheckSignature(signer.Details.PublicKey) {
+	if !nc.checkSignatureWithCache(signer.Details.PublicKey, useCache) {
 		return false, ErrSignatureMismatch
 	}
 
@@ -809,6 +858,25 @@ func (nc *NebulaCertificate) Sha256Sum() (string, error) {
 	return hex.EncodeToString(sum[:]), nil
 }
 
+// NOTE: This uses an internal cache that will not be invalidated automatically
+// if you manually change any fields in the NebulaCertificate.
+func (nc *NebulaCertificate) sha256SumWithCache(useCache bool) (string, error) {
+	if !useCache {
+		return nc.Sha256Sum()
+	}
+
+	if s := nc.sha256sum.Load(); s != nil {
+		return *s, nil
+	}
+	s, err := nc.Sha256Sum()
+	if err != nil {
+		return s, err
+	}
+
+	nc.sha256sum.Store(&s)
+	return s, nil
+}
+
 func (nc *NebulaCertificate) MarshalJSON() ([]byte, error) {
 	toString := func(ips []*net.IPNet) []string {
 		s := []string{}

connection_manager.go

@@ -427,7 +427,7 @@ func (n *connectionManager) isInvalidCertificate(now time.Time, hostinfo *HostIn
 		return false
 	}
 
-	valid, err := remoteCert.Verify(now, n.intf.caPool)
+	valid, err := remoteCert.VerifyWithCache(now, n.intf.caPool)
 	if valid {
 		return false
 	}