Implement certificate caching in PublicKey Provider

Added certificate caching mechanism to the PublicKey Provider to reduce the number of calls to the CryptoProvider. Now, before performing an expensive certificate generation operation, the system will first check if a cached certificate for the requested key exists. If it does, it returns the cached certificate, otherwise, it generates a new one and stores it in the cache for future requests.

service/kas/access/publicKey.go

@@ -8,11 +8,12 @@ import (
 	"encoding/pem"
 	"errors"
 	"log/slog"
+	"sync"
 
 	kaspb "github.com/arkavo-org/opentdf-platform/protocol/go/kas"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
-	wrapperspb "google.golang.org/protobuf/types/known/wrapperspb"
+	"google.golang.org/protobuf/types/known/wrapperspb"
 )
 
 const (
@@ -21,9 +22,10 @@ const (
 	algorithmEc256       = "ec:secp256r1"
 )
 
+var ecCertCache sync.Map
+
 func (p *Provider) LegacyPublicKey(ctx context.Context, in *kaspb.LegacyPublicKeyRequest) (*wrapperspb.StringValue, error) {
 	algorithm := in.GetAlgorithm()
-	var cert string
 	var err error
 	if p.CryptoProvider == nil {
 		return nil, errors.Join(ErrConfig, status.Error(codes.Internal, "configuration error"))
@@ -34,17 +36,25 @@ func (p *Provider) LegacyPublicKey(ctx context.Context, in *kaspb.LegacyPublicKe
 		if !ok {
 			return nil, errors.New("services.kas.eccertid is not a string")
 		}
-		cert, err = p.CryptoProvider.ECCertificate(ecCertID)
-		if err != nil {
-			slog.ErrorContext(ctx, "CryptoProvider.ECPublicKey failed", "err", err)
-			return nil, errors.Join(ErrConfig, status.Error(codes.Internal, "configuration error"))
+		if cert, exists := ecCertCache.Load(ecCertID); exists {
+			return cert.(*wrapperspb.StringValue), nil
 		}
-	} else {
-		cert, err = p.CryptoProvider.RSAPublicKey("unknown")
+		cert, err := p.CryptoProvider.ECCertificate(ecCertID)
 		if err != nil {
-			slog.ErrorContext(ctx, "CryptoProvider.RSAPublicKey failed", "err", err)
+			slog.ErrorContext(ctx, "CryptoProvider.ECPublicKey failed", "err", err)
 			return nil, errors.Join(ErrConfig, status.Error(codes.Internal, "configuration error"))
 		}
+		// workaround for Error code 75497574.  [ec_key_pair.cpp:650] Failed to create X509 cert struct.error:04800066:PEM routines::bad end line
+		cert += "\n"
+		ecCertStringValue := &wrapperspb.StringValue{Value: cert}
+		// Store the certificate in the cache
+		ecCertCache.Store(ecCertID, ecCertStringValue)
+		return ecCertStringValue, nil
+	}
+	cert, err := p.CryptoProvider.RSAPublicKey("unknown")
+	if err != nil {
+		slog.ErrorContext(ctx, "CryptoProvider.RSAPublicKey failed", "err", err)
+		return nil, errors.Join(ErrConfig, status.Error(codes.Internal, "configuration error"))
 	}
 	// workaround for Error code 75497574.  [ec_key_pair.cpp:650] Failed to create X509 cert struct.error:04800066:PEM routines::bad end line
 	cert += "\n"