Added root CA config

kindling.go

@@ -2,7 +2,9 @@ package kindling
 
 import (
 	"context"
+	"crypto/x509"
 	"embed"
+	"encoding/pem"
 	"fmt"
 	"io"
 	"log/slog"
@@ -31,6 +33,7 @@ type httpDialer func(ctx context.Context, addr string) (http.RoundTripper, error
 type kindling struct {
 	httpDialers []httpDialer
 	logWriter   io.Writer
+	rootCA      string
 }
 
 // Make sure that kindling implements the Kindling interface.
@@ -75,10 +78,10 @@ func WithDomainFronting(configURL, countryCode string) Option {
 	}
 }
 
-// WithDoHTunnel is a functional option that enables DNS over HTTPS (DoH) tunneling for the Kindling.
-func WithDoHTunnel() Option {
+// WithRootCA pins the root CA to use for TLS.
+func WithRootCA(rootCA string) Option {
 	return func(k *kindling) {
-
+		k.rootCA = rootCA
 	}
 }
 
@@ -149,7 +152,7 @@ func (k *kindling) newSmartHTTPDialer(domains ...string) (httpDialer, error) {
 		}
 		return k.newTransportWithDialContext(func(ctx context.Context, network, addr string) (net.Conn, error) {
 			return streamConn, nil
-		}), nil
+		})
 	}, nil
 }
 
@@ -165,18 +168,31 @@ func (k *kindling) newSmartHTTPTransport(domains ...string) (*http.Transport, er
 			return nil, fmt.Errorf("failed to dial stream: %v", err)
 		}
 		return streamConn, nil
-	}), nil
+	})
 }
 
-func (k *kindling) newTransportWithDialContext(dialContext func(ctx context.Context, network, addr string) (net.Conn, error)) *http.Transport {
-	return &http.Transport{
+func (k *kindling) newTransportWithDialContext(dialContext func(ctx context.Context, network, addr string) (net.Conn, error)) (*http.Transport, error) {
+	tr := &http.Transport{
 		DialContext:           dialContext,
 		ForceAttemptHTTP2:     true,
 		MaxIdleConns:          100,
 		IdleConnTimeout:       90 * time.Second,
 		TLSHandshakeTimeout:   20 * time.Second,
 		ExpectContinueTimeout: 4 * time.Second,
 	}
+	if k.rootCA != "" {
+		block, _ := pem.Decode([]byte(k.rootCA))
+		if block == nil {
+			return nil, fmt.Errorf("failed to decode root CA PEM block")
+		}
+		certPool := x509.NewCertPool()
+		if !certPool.AppendCertsFromPEM(block.Bytes) {
+			log.Error("Failed to append root CA to pool")
+			return nil, fmt.Errorf("failed to append root CA to pool")
+		}
+		tr.TLSClientConfig.RootCAs = certPool
+	}
+	return tr, nil
 }
 
 //go:embed smart_dialer_config.yml