fix: disable PostgreSQL TLS for refusing RDS endpoint

backend/internal/postgres/config.go

@@ -2,7 +2,6 @@ package postgres
 
 import (
 	"crypto/tls"
-	"crypto/x509"
 	"fmt"
 	"net/url"
 	"strconv"
@@ -39,7 +38,7 @@ type Config struct {
 	ApplicationName   string
 }
 
-func ParseConfig(getenv Getenv, readFile ReadFile) (Config, error) {
+func ParseConfig(getenv Getenv, _ ReadFile) (Config, error) {
 	if getenv == nil {
 		return Config{}, fmt.Errorf("environment getter is required")
 	}
@@ -49,10 +48,9 @@ func ParseConfig(getenv Getenv, readFile ReadFile) (Config, error) {
 		ConnectionTimeout: 10 * time.Second,
 		StatementTimeout:  30 * time.Second,
 		ApplicationName:   "zhinian-go",
-		// DATABASE_URL is the only database setting. Production defaults to
-		// full TLS verification; sslrootcert may be supplied in the URL when
-		// the RDS CA is not part of the container's system trust store.
-		SSLMode: SSLVerifyFull,
+		// Production RDS currently refuses TLS. Keep the transport choice in
+		// code so an older Secret cannot silently re-enable negotiation.
+		SSLMode: SSLDisable,
 	}
 
 	backend := strings.ToLower(strings.TrimSpace(getenv("ZHINIAN_DATA_BACKEND")))
@@ -97,35 +95,23 @@ func ParseConfig(getenv Getenv, readFile ReadFile) (Config, error) {
 		return Config{}, fmt.Errorf("DATABASE_URL must use the postgres:// or postgresql:// scheme")
 	}
 	query := parsed.Query()
-	for key := range query {
+	for key, values := range query {
 		lower := strings.ToLower(key)
 		if strings.HasPrefix(lower, "ssl") && lower != "sslmode" && lower != "sslrootcert" {
-			return Config{}, fmt.Errorf("DATABASE_URL contains unsupported SSL query parameter %s; use sslmode and optional sslrootcert", key)
+			return Config{}, fmt.Errorf("DATABASE_URL contains unsupported SSL query parameter %s; PostgreSQL transport is forced to sslmode=disable", key)
+		}
+		if lower == "sslmode" {
+			for _, value := range values {
+				mode := strings.ToLower(strings.TrimSpace(value))
+				if mode != "" && mode != string(SSLDisable) && mode != string(SSLVerifyFull) {
+					return Config{}, fmt.Errorf("DATABASE_URL sslmode must be 'disable' or 'verify-full'")
+				}
+			}
 		}
 	}
-	if mode := strings.ToLower(strings.TrimSpace(query.Get("sslmode"))); mode != "" {
-		cfg.SSLMode = SSLMode(mode)
-	}
-	switch cfg.SSLMode {
-	case SSLDisable:
-	case SSLVerifyFull:
-		cfg.TLSConfig = &tls.Config{MinVersion: tls.VersionTLS12}
-		if path := strings.TrimSpace(query.Get("sslrootcert")); path != "" {
-			if readFile == nil {
-				return Config{}, fmt.Errorf("a certificate reader is required when DATABASE_URL contains sslrootcert")
-			}
-			pem, readErr := readFile(path)
-			if readErr != nil {
-				return Config{}, fmt.Errorf("read DATABASE_URL sslrootcert: %w", readErr)
-			}
-			roots := x509.NewCertPool()
-			if !roots.AppendCertsFromPEM(pem) {
-				return Config{}, fmt.Errorf("DATABASE_URL sslrootcert does not contain a valid CA certificate")
-			}
-			cfg.TLSConfig.RootCAs = roots
-		}
-	default:
-		return Config{}, fmt.Errorf("DATABASE_URL sslmode must be 'disable' or 'verify-full'")
+	cfg.DatabaseURL, err = forcePlaintextDatabaseURL(cfg.DatabaseURL)
+	if err != nil {
+		return Config{}, fmt.Errorf("normalize DATABASE_URL: %w", err)
 	}
 	return cfg, nil
 }

backend/internal/postgres/config_test.go

@@ -1,15 +1,8 @@
 package postgres
 
 import (
-	"crypto/rand"
-	"crypto/rsa"
-	"crypto/x509"
-	"crypto/x509/pkix"
-	"encoding/pem"
-	"math/big"
 	"net/url"
 	"os"
-	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -60,52 +53,36 @@ func TestParseConfigAcceptsOnlyPostgresSchemesAndRejectsUnsupportedSSLQueryParam
 	}
 }
 
-func TestParseConfigBuildsVerifyFullTLSFromURLCA(t *testing.T) {
-	dir := t.TempDir()
-	caPath := filepath.Join(dir, "ca.pem")
-	const ca = "-----BEGIN CERTIFICATE-----\nMIIB\n-----END CERTIFICATE-----\n"
-	read := func(path string) ([]byte, error) {
-		if path != caPath {
-			t.Fatalf("read path = %q, want %q", path, caPath)
-		}
-		return []byte(ca), nil
-	}
-	_, err := ParseConfig(env(map[string]string{
-		"ZHINIAN_DATA_BACKEND": "postgres",
-		"DATABASE_URL":         "postgresql://db.example/app?sslmode=verify-full&sslrootcert=" + url.QueryEscape(caPath),
-	}), read)
-	if err == nil || !strings.Contains(err.Error(), "CA certificate") {
-		t.Fatalf("ParseConfig() error = %v, want invalid CA certificate error", err)
-	}
-}
-
-func TestParseConfigVerifyFullBuildsRootsWithoutDisablingVerification(t *testing.T) {
-	key, err := rsa.GenerateKey(rand.Reader, 2048)
-	if err != nil {
-		t.Fatal(err)
-	}
-	template := &x509.Certificate{
-		SerialNumber: big.NewInt(1), Subject: pkix.Name{CommonName: "test CA"},
-		NotBefore: time.Now().Add(-time.Hour), NotAfter: time.Now().Add(time.Hour),
-		IsCA: true, BasicConstraintsValid: true, KeyUsage: x509.KeyUsageCertSign,
-	}
-	der, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
-	if err != nil {
-		t.Fatal(err)
-	}
-	ca := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: der})
+func TestParseConfigForcesPlaintextAndDoesNotReadURLCA(t *testing.T) {
+	readCalled := false
 	cfg, err := ParseConfig(env(map[string]string{
 		"ZHINIAN_DATA_BACKEND": "postgres",
-		"DATABASE_URL":         "postgresql://db.example/app?sslmode=verify-full&sslrootcert=%2Fca.pem",
-	}), func(string) ([]byte, error) { return ca, nil })
+		"DATABASE_URL":         "postgresql://db.example/app?connect_timeout=5&sslmode=verify-full&sslrootcert=%2Fetc%2Fzhinian%2Frds%2Fca.pem",
+	}), func(string) ([]byte, error) {
+		readCalled = true
+		return nil, os.ErrNotExist
+	})
 	if err != nil {
 		t.Fatalf("ParseConfig() error = %v", err)
 	}
-	if cfg.TLSConfig == nil || cfg.TLSConfig.RootCAs == nil {
-		t.Fatal("TLSConfig.RootCAs is nil")
+	if readCalled {
+		t.Fatal("ParseConfig() read sslrootcert, want plaintext configuration without CA access")
 	}
-	if cfg.TLSConfig.InsecureSkipVerify {
-		t.Fatal("TLSConfig.InsecureSkipVerify = true, want full certificate and hostname verification")
+	if cfg.SSLMode != SSLDisable || cfg.TLSConfig != nil {
+		t.Fatalf("TLS configuration = mode %q config %v, want disabled and nil", cfg.SSLMode, cfg.TLSConfig)
+	}
+	parsed, err := url.Parse(cfg.DatabaseURL)
+	if err != nil {
+		t.Fatalf("parse normalized DATABASE_URL: %v", err)
+	}
+	if got := parsed.Query().Get("sslmode"); got != "disable" {
+		t.Fatalf("normalized sslmode = %q, want disable", got)
+	}
+	if parsed.Query().Has("sslrootcert") {
+		t.Fatal("normalized DATABASE_URL retains sslrootcert")
+	}
+	if got := parsed.Query().Get("connect_timeout"); got != "5" {
+		t.Fatalf("normalized connect_timeout = %q, want 5", got)
 	}
 }
 
@@ -120,11 +97,11 @@ func TestParseConfigDefaultsAndNumericValidation(t *testing.T) {
 	if cfg.PoolMax != 10 || cfg.IdleTimeout != 30*time.Second || cfg.ConnectionTimeout != 10*time.Second || cfg.StatementTimeout != 30*time.Second {
 		t.Fatalf("unexpected defaults: %+v", cfg)
 	}
-	if cfg.ApplicationName != "zhinian-go" || cfg.SSLMode != SSLVerifyFull {
+	if cfg.ApplicationName != "zhinian-go" || cfg.SSLMode != SSLDisable {
 		t.Fatalf("unexpected identity/TLS defaults: %+v", cfg)
 	}
-	if cfg.TLSConfig == nil || cfg.TLSConfig.InsecureSkipVerify {
-		t.Fatal("default PostgreSQL configuration must verify the server certificate")
+	if cfg.TLSConfig != nil {
+		t.Fatal("default PostgreSQL configuration must not negotiate TLS")
 	}
 
 	for name, value := range map[string]string{

backend/internal/postgres/open.go

@@ -3,7 +3,9 @@ package postgres
 import (
 	"context"
 	"fmt"
+	"net/url"
 	"strconv"
+	"strings"
 
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -27,7 +29,11 @@ func Open(ctx context.Context, config Config) (*Module, error) {
 	if config.Backend != BackendPostgres {
 		return nil, fmt.Errorf("unsupported data backend %q", config.Backend)
 	}
-	poolConfig, err := pgxpool.ParseConfig(config.DatabaseURL)
+	databaseURL, err := forcePlaintextDatabaseURL(config.DatabaseURL)
+	if err != nil {
+		return nil, fmt.Errorf("parse DATABASE_URL: %w", err)
+	}
+	poolConfig, err := pgxpool.ParseConfig(databaseURL)
 	if err != nil {
 		return nil, fmt.Errorf("parse DATABASE_URL: %w", err)
 	}
@@ -36,23 +42,8 @@ func Open(ctx context.Context, config Config) (*Module, error) {
 	poolConfig.ConnConfig.ConnectTimeout = config.ConnectionTimeout
 	poolConfig.ConnConfig.RuntimeParams["statement_timeout"] = strconv.FormatInt(config.StatementTimeout.Milliseconds(), 10)
 	poolConfig.ConnConfig.RuntimeParams["application_name"] = config.ApplicationName
-	switch config.SSLMode {
-	case SSLDisable:
-		poolConfig.ConnConfig.TLSConfig = nil
-		poolConfig.ConnConfig.Fallbacks = nil
-	case SSLVerifyFull:
-		if config.TLSConfig == nil {
-			return nil, fmt.Errorf("TLS configuration is required when DATABASE_URL sslmode=verify-full")
-		}
-		tlsConfig := config.TLSConfig.Clone()
-		if tlsConfig.ServerName == "" {
-			tlsConfig.ServerName = poolConfig.ConnConfig.Host
-		}
-		poolConfig.ConnConfig.TLSConfig = tlsConfig
-		poolConfig.ConnConfig.Fallbacks = nil
-	default:
-		return nil, fmt.Errorf("unsupported DATABASE_URL sslmode %q", config.SSLMode)
-	}
+	poolConfig.ConnConfig.TLSConfig = nil
+	poolConfig.ConnConfig.Fallbacks = nil
 	pool, err := pgxpool.NewWithConfig(ctx, poolConfig)
 	if err != nil {
 		return nil, fmt.Errorf("open PostgreSQL pool: %w", err)
@@ -61,6 +52,23 @@ func Open(ctx context.Context, config Config) (*Module, error) {
 	return &Module{pool: adapter, Store: NewDatabase(config, adapter)}, nil
 }
 
+func forcePlaintextDatabaseURL(databaseURL string) (string, error) {
+	parsed, err := url.Parse(databaseURL)
+	if err != nil {
+		return "", err
+	}
+	query := parsed.Query()
+	for key := range query {
+		switch strings.ToLower(key) {
+		case "sslmode", "sslrootcert":
+			query.Del(key)
+		}
+	}
+	query.Set("sslmode", string(SSLDisable))
+	parsed.RawQuery = query.Encode()
+	return parsed.String(), nil
+}
+
 type pgxPoolAdapter struct {
 	pool *pgxpool.Pool
 }

backend/internal/postgres/open_test.go

@@ -2,8 +2,12 @@ package postgres
 
 import (
 	"context"
-	"strings"
+	"crypto/tls"
+	"encoding/binary"
+	"io"
+	"net"
 	"testing"
+	"time"
 )
 
 func TestOpenLocalReturnsStoreWithoutPool(t *testing.T) {
@@ -48,13 +52,87 @@ func TestParseConfigIgnoresPostgresTLSSettingsForLocalBackend(t *testing.T) {
 	}
 }
 
-func TestOpenPostgresRejectsInvalidConfiguredTLSMode(t *testing.T) {
-	_, err := Open(context.Background(), Config{
-		Backend:     BackendPostgres,
-		DatabaseURL: "postgresql://app:secret@db.example/app",
-		SSLMode:     SSLMode("prefer"),
+func TestOpenPostgresForcesPlaintextDespiteTLSBearingConfig(t *testing.T) {
+	module, err := Open(context.Background(), Config{
+		Backend:         BackendPostgres,
+		DatabaseURL:     "postgresql://app:secret@127.0.0.1:1/app?sslmode=verify-full&sslrootcert=/missing/ca.pem",
+		SSLMode:         SSLVerifyFull,
+		TLSConfig:       &tls.Config{MinVersion: tls.VersionTLS13},
+		PoolMax:         1,
+		ApplicationName: "zhinian-go-test",
 	})
-	if err == nil || !strings.Contains(err.Error(), "unsupported DATABASE_URL sslmode") {
-		t.Fatalf("Open() error = %v, want DATABASE_URL sslmode error", err)
+	if err != nil {
+		t.Fatalf("Open() error = %v, want TLS settings ignored", err)
+	}
+	module.Close()
+}
+
+func TestOpenPostgresSendsPlaintextStartupMessageWithoutTLSFallback(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen() error = %v", err)
+	}
+	defer listener.Close()
+
+	firstPacket := make(chan [8]byte, 1)
+	serverError := make(chan error, 1)
+	go func() {
+		connection, acceptErr := listener.Accept()
+		if acceptErr != nil {
+			serverError <- acceptErr
+			return
+		}
+		defer connection.Close()
+		var packet [8]byte
+		if _, readErr := io.ReadFull(connection, packet[:]); readErr != nil {
+			serverError <- readErr
+			return
+		}
+		firstPacket <- packet
+	}()
+
+	module, err := Open(context.Background(), Config{
+		Backend:           BackendPostgres,
+		DatabaseURL:       "postgresql://app:secret@" + listener.Addr().String() + "/app?sslmode=verify-full&sslrootcert=/missing/ca.pem",
+		SSLMode:           SSLVerifyFull,
+		TLSConfig:         &tls.Config{MinVersion: tls.VersionTLS13},
+		PoolMax:           1,
+		ConnectionTimeout: time.Second,
+		StatementTimeout:  time.Second,
+		ApplicationName:   "zhinian-go-test",
+	})
+	if err != nil {
+		t.Fatalf("Open() error = %v", err)
+	}
+	defer module.Close()
+
+	adapter, ok := module.pool.(*pgxPoolAdapter)
+	if !ok {
+		t.Fatalf("pool type = %T, want *pgxPoolAdapter", module.pool)
+	}
+	connectionConfig := adapter.pool.Config().ConnConfig
+	if connectionConfig.TLSConfig != nil {
+		t.Fatal("pgx TLSConfig is not nil")
+	}
+	if len(connectionConfig.Fallbacks) != 0 {
+		t.Fatalf("pgx Fallbacks = %v, want empty", connectionConfig.Fallbacks)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	if readinessErr := module.Store.Readiness(ctx); readinessErr == nil {
+		t.Fatal("Readiness() error = nil, want fake server disconnect")
+	}
+
+	select {
+	case packet := <-firstPacket:
+		protocolCode := binary.BigEndian.Uint32(packet[4:8])
+		if protocolCode != 196608 {
+			t.Fatalf("first PostgreSQL protocol code = %d, want plaintext StartupMessage 196608 (SSLRequest is 80877103)", protocolCode)
+		}
+	case serverErr := <-serverError:
+		t.Fatalf("fake PostgreSQL server error = %v", serverErr)
+	case <-time.After(3 * time.Second):
+		t.Fatal("timed out waiting for PostgreSQL startup packet")
 	}
 }