perf(jwk,cache): cache parsed public keys + RLock token cache reads

Hot-path JWT verification rebuilt the public key on every call:
  jwk -> ToRSAPublicKey -> x509.MarshalPKIXPublicKey -> pem.Encode
  -> verifySignature -> pem.Decode -> x509.ParsePKIXPublicKey -> verify
Under yaegi this pinned a CPU when many concurrent dashboard panels
poll behind the middleware. The PEM round trip is pure waste.

* jwk.go: cache pre-parsed crypto.PublicKey per kid alongside the
  raw JWKSet (parallel cache entry, same 1h TTL, invalidates together).
* jwt.go: split verifySignatureWithKey from verifySignature; existing
  PEM-input entry point preserved for backchannel-logout callers.
* token_manager.go: VerifyJWTSignatureAndClaims now goes straight from
  jwks cache to verifySignatureWithKey, no PEM round trip and no
  per-request availableKids slice.
* universal_cache.go: token/JWK/session Get() takes RLock when the
  entry is unexpired, so concurrent token verifications no longer
  serialize on a single mutex. LRU semantics for general and metadata
  caches are unchanged (tests cover the strict-LRU contract there).
* mocks: MockJWKCache, EnhancedMockJWKCache, mockJWKCacheForLogout,
  staticJWKCache satisfy the extended interface.

enhanced_mocks_test.go

@@ -2,6 +2,8 @@ package traefikoidc
 
 import (
 	"context"
+	"crypto"
+	"fmt"
 	"net/http"
 	"sync"
 	"sync/atomic"
@@ -40,6 +42,31 @@ func (m *EnhancedMockJWKCache) GetJWKS(ctx context.Context, jwksURL string, http
 	return m.JWKS, m.Err
 }
 
+func (m *EnhancedMockJWKCache) GetPublicKey(ctx context.Context, jwksURL, kid string, httpClient *http.Client) (crypto.PublicKey, error) {
+	jwks, err := m.GetJWKS(ctx, jwksURL, httpClient)
+	if err != nil {
+		return nil, err
+	}
+	if jwks == nil {
+		return nil, fmt.Errorf("JWKS is nil")
+	}
+	for i := range jwks.Keys {
+		k := &jwks.Keys[i]
+		if k.Kid != kid {
+			continue
+		}
+		switch k.Kty {
+		case "RSA":
+			return k.ToRSAPublicKey()
+		case "EC":
+			return k.ToECDSAPublicKey()
+		default:
+			return nil, fmt.Errorf("unsupported key type: %s", k.Kty)
+		}
+	}
+	return nil, fmt.Errorf("no matching public key found for kid: %s", kid)
+}
+
 func (m *EnhancedMockJWKCache) Cleanup() {
 	atomic.AddInt32(&m.CleanupCalls, 1)
 	m.mu.Lock()

jwk.go

@@ -2,6 +2,7 @@ package traefikoidc
 
 import (
 	"context"
+	"crypto"
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rsa"
@@ -18,6 +19,18 @@ import (
 	"time"
 )
 
+// parsedKeysSuffix marks the parallel UniversalCache entry that stores
+// pre-parsed public keys for a given JWKS URL.
+const parsedKeysSuffix = ":parsed"
+
+// parsedJWKS holds keys decoded from a JWKSet, indexed by kid. Storing the
+// already-parsed crypto.PublicKey avoids re-running the DER/PEM round trip
+// on every JWT verification — a costly operation under the yaegi interpreter
+// that hosts Traefik plugins.
+type parsedJWKS struct {
+	keys map[string]crypto.PublicKey
+}
+
 // JWK represents a JSON Web Key as defined in RFC 7517.
 // It can represent different key types including RSA, EC, and symmetric keys.
 type JWK struct {
@@ -49,6 +62,7 @@ type JWKCache struct {
 // JWKCacheInterface defines the contract for JWK caching implementations.
 type JWKCacheInterface interface {
 	GetJWKS(ctx context.Context, jwksURL string, httpClient *http.Client) (*JWKSet, error)
+	GetPublicKey(ctx context.Context, jwksURL, kid string, httpClient *http.Client) (crypto.PublicKey, error)
 	Cleanup()
 	Close()
 }
@@ -96,6 +110,62 @@ func (c *JWKCache) GetJWKS(ctx context.Context, jwksURL string, httpClient *http
 	return jwks, nil
 }
 
+// GetPublicKey returns the parsed public key for a given kid, fetching and
+// caching the JWKS plus its derived parsedJWKS on miss. The parsed entry is
+// stored alongside the raw JWKSet under a sibling cache key with the same
+// 1-hour TTL, so both invalidate together when the upstream JWKS rotates.
+func (c *JWKCache) GetPublicKey(ctx context.Context, jwksURL, kid string, httpClient *http.Client) (crypto.PublicKey, error) {
+	parsedKey := jwksURL + parsedKeysSuffix
+	if v, found := c.cache.Get(parsedKey); found {
+		if pj, ok := v.(*parsedJWKS); ok {
+			if k, ok := pj.keys[kid]; ok {
+				return k, nil
+			}
+		}
+	}
+
+	jwks, err := c.GetJWKS(ctx, jwksURL, httpClient)
+	if err != nil {
+		return nil, err
+	}
+
+	pj := buildParsedJWKS(jwks)
+	_ = c.cache.Set(parsedKey, pj, 1*time.Hour) // Safe to ignore: cache failures are non-critical
+
+	if k, ok := pj.keys[kid]; ok {
+		return k, nil
+	}
+	return nil, fmt.Errorf("no matching public key found for kid: %s", kid)
+}
+
+// buildParsedJWKS pre-parses every JWK in the set into the matching
+// crypto.PublicKey, indexed by kid. Errors on individual keys are skipped so
+// a single bad key does not block the rest of the keyset.
+func buildParsedJWKS(jwks *JWKSet) *parsedJWKS {
+	out := make(map[string]crypto.PublicKey, len(jwks.Keys))
+	for i := range jwks.Keys {
+		k := &jwks.Keys[i]
+		if k.Kid == "" {
+			continue
+		}
+		var pub crypto.PublicKey
+		var err error
+		switch k.Kty {
+		case "RSA":
+			pub, err = k.ToRSAPublicKey()
+		case "EC":
+			pub, err = k.ToECDSAPublicKey()
+		default:
+			continue
+		}
+		if err != nil {
+			continue
+		}
+		out[k.Kid] = pub
+	}
+	return &parsedJWKS{keys: out}
+}
+
 // Cleanup is a no-op as cleanup is handled by UniversalCache
 func (c *JWKCache) Cleanup() {
 	// Handled internally by UniversalCache

jwt.go

@@ -528,6 +528,21 @@ func verifyNotBefore(notBefore float64) error {
 //   - An error if the key parsing fails, the algorithm is unsupported,
 //     or the signature verification fails
 func verifySignature(tokenString string, publicKeyPEM []byte, alg string) error {
+	block, _ := pem.Decode(publicKeyPEM)
+	if block == nil {
+		return fmt.Errorf("failed to parse PEM block containing the public key")
+	}
+	pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)
+	if err != nil {
+		return fmt.Errorf("failed to parse public key: %w", err)
+	}
+	return verifySignatureWithKey(tokenString, pubKey, alg)
+}
+
+// verifySignatureWithKey verifies a JWT signature using an already-parsed
+// public key, skipping the PEM-encode/decode round trip that verifySignature
+// performs. This is the hot path used by VerifyJWTSignatureAndClaims.
+func verifySignatureWithKey(tokenString string, pubKey crypto.PublicKey, alg string) error {
 	parts := strings.Split(tokenString, ".")
 	if len(parts) != 3 {
 		return fmt.Errorf("invalid token format")
@@ -537,14 +552,6 @@ func verifySignature(tokenString string, publicKeyPEM []byte, alg string) error
 	if err != nil {
 		return fmt.Errorf("failed to decode signature: %w", err)
 	}
-	block, _ := pem.Decode(publicKeyPEM)
-	if block == nil {
-		return fmt.Errorf("failed to parse PEM block containing the public key")
-	}
-	pubKey, err := x509.ParsePKIXPublicKey(block.Bytes)
-	if err != nil {
-		return fmt.Errorf("failed to parse public key: %w", err)
-	}
 	var hashFunc crypto.Hash
 	switch alg {
 	case "RS256", "PS256", "ES256":

logout_test.go

@@ -2,6 +2,7 @@ package traefikoidc
 
 import (
 	"context"
+	"crypto"
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
@@ -639,6 +640,26 @@ func (m *mockJWKCacheForLogout) GetJWKS(ctx context.Context, jwksURL string, htt
 	}, nil
 }
 
+func (m *mockJWKCacheForLogout) GetPublicKey(ctx context.Context, jwksURL, kid string, httpClient *http.Client) (crypto.PublicKey, error) {
+	jwks, err := m.GetJWKS(ctx, jwksURL, httpClient)
+	if err != nil {
+		return nil, err
+	}
+	for i := range jwks.Keys {
+		k := &jwks.Keys[i]
+		if k.Kid != kid {
+			continue
+		}
+		switch k.Kty {
+		case "RSA":
+			return k.ToRSAPublicKey()
+		case "EC":
+			return k.ToECDSAPublicKey()
+		}
+	}
+	return nil, fmt.Errorf("no matching public key found for kid: %s", kid)
+}
+
 func (m *mockJWKCacheForLogout) Clear()   {}
 func (m *mockJWKCacheForLogout) Cleanup() {}
 func (m *mockJWKCacheForLogout) Close()   {}
@@ -755,6 +776,22 @@ func (s *staticJWKCache) GetJWKS(ctx context.Context, jwksURL string, httpClient
 	return s.jwks, nil
 }
 
+func (s *staticJWKCache) GetPublicKey(ctx context.Context, jwksURL, kid string, httpClient *http.Client) (crypto.PublicKey, error) {
+	for i := range s.jwks.Keys {
+		k := &s.jwks.Keys[i]
+		if k.Kid != kid {
+			continue
+		}
+		switch k.Kty {
+		case "RSA":
+			return k.ToRSAPublicKey()
+		case "EC":
+			return k.ToECDSAPublicKey()
+		}
+	}
+	return nil, fmt.Errorf("no matching public key found for kid: %s", kid)
+}
+
 func (s *staticJWKCache) Clear()   {}
 func (s *staticJWKCache) Cleanup() {}
 func (s *staticJWKCache) Close()   {}

main_test.go

@@ -208,6 +208,32 @@ func (m *MockJWKCache) GetJWKS(ctx context.Context, jwksURL string, httpClient *
 	return m.JWKS, m.Err
 }
 
+func (m *MockJWKCache) GetPublicKey(ctx context.Context, jwksURL, kid string, httpClient *http.Client) (crypto.PublicKey, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	if m.Err != nil {
+		return nil, m.Err
+	}
+	if m.JWKS == nil {
+		return nil, fmt.Errorf("JWKS is nil")
+	}
+	for i := range m.JWKS.Keys {
+		k := &m.JWKS.Keys[i]
+		if k.Kid != kid {
+			continue
+		}
+		switch k.Kty {
+		case "RSA":
+			return k.ToRSAPublicKey()
+		case "EC":
+			return k.ToECDSAPublicKey()
+		default:
+			return nil, fmt.Errorf("unsupported key type: %s", k.Kty)
+		}
+	}
+	return nil, fmt.Errorf("no matching public key found for kid: %s", kid)
+}
+
 func (m *MockJWKCache) Cleanup() {
 	// Mock cleanup is a no-op - we don't want to destroy the mock JWKS data
 	// Real cleanup is for expired entries, not resetting all data

token_manager.go

@@ -315,15 +315,6 @@ func (t *TraefikOidc) VerifyJWTSignatureAndClaims(jwt *JWT, token string) error
 	jwksURL := t.jwksURL
 	t.metadataMu.RUnlock()
 
-	jwks, err := t.jwkCache.GetJWKS(context.Background(), jwksURL, t.httpClient)
-	if err != nil {
-		return fmt.Errorf("failed to get JWKS: %w", err)
-	}
-
-	if !t.suppressDiagnosticLogs && jwks != nil {
-		t.safeLogDebugf("DIAGNOSTIC: Retrieved JWKS with %d keys from URL: %s", len(jwks.Keys), jwksURL)
-	}
-
 	kid, ok := jwt.Header["kid"].(string)
 	if !ok {
 		return fmt.Errorf("missing key ID in token header")
@@ -337,38 +328,12 @@ func (t *TraefikOidc) VerifyJWTSignatureAndClaims(jwt *JWT, token string) error
 		t.safeLogDebugf("DIAGNOSTIC: Looking for kid=%s, alg=%s in JWKS", kid, alg)
 	}
 
-	if jwks == nil {
-		return fmt.Errorf("JWKS is nil, cannot verify token")
-	}
-
-	// Find the matching key in JWKS
-	var matchingKey *JWK
-	availableKids := make([]string, 0, len(jwks.Keys))
-	for _, key := range jwks.Keys {
-		availableKids = append(availableKids, key.Kid)
-		if key.Kid == kid {
-			matchingKey = &key
-			break
-		}
-	}
-
-	if matchingKey == nil {
-		if !t.suppressDiagnosticLogs {
-			t.safeLogErrorf("DIAGNOSTIC: No matching key found for kid=%s. Available kids: %v", kid, availableKids)
-		}
-		return fmt.Errorf("no matching public key found for kid: %s", kid)
-	}
-
-	if !t.suppressDiagnosticLogs {
-		t.safeLogDebugf("DIAGNOSTIC: Found matching key for kid=%s, key type: %s", kid, matchingKey.Kty)
-	}
-
-	publicKeyPEM, err := jwkToPEM(matchingKey)
+	pubKey, err := t.jwkCache.GetPublicKey(context.Background(), jwksURL, kid, t.httpClient)
 	if err != nil {
-		return fmt.Errorf("failed to convert JWK to PEM: %w", err)
+		return fmt.Errorf("failed to get public key: %w", err)
 	}
 
-	if err := verifySignature(token, publicKeyPEM, alg); err != nil {
+	if err := verifySignatureWithKey(token, pubKey, alg); err != nil {
 		if !t.suppressDiagnosticLogs {
 			t.safeLogErrorf("DIAGNOSTIC: Signature verification failed for kid=%s, alg=%s: %v", kid, alg, err)
 		}

universal_cache.go

@@ -343,6 +343,31 @@ func (c *UniversalCache) Get(key string) (interface{}, bool) {
 		}
 	}
 
+	// Fast read path for caches whose eviction is dominated by TTL rather than
+	// access-recency (token, JWK, session). Holding only an RLock here lets all
+	// concurrent readers verify cached tokens in parallel — under yaegi the
+	// previous unconditional Lock serialized every JWT verify on a single
+	// mutex and pinned a CPU under load.
+	switch c.config.Type {
+	case CacheTypeToken, CacheTypeJWK, CacheTypeSession:
+		c.mu.RLock()
+		item, exists := c.items[key]
+		if !exists {
+			c.mu.RUnlock()
+			atomic.AddInt64(&c.misses, 1)
+			return nil, false
+		}
+		if !time.Now().After(item.ExpiresAt) {
+			value := item.Value
+			c.mu.RUnlock()
+			atomic.AddInt64(&c.hits, 1)
+			return value, true
+		}
+		c.mu.RUnlock()
+		// Expired — fall through to the write-locked slow path below to
+		// remove the entry under exclusive access.
+	}
+
 	c.mu.Lock()
 	defer c.mu.Unlock()