Merge pull request #2 from ooni/issue/2106

feat(tls): add stdlib-aware Client-like factory

See ooni/probe#2106

tls/stdlibwrapper.go

@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+package tls
+
+import (
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"reflect"
+)
+
+// ErrIncompatibleStdlibConfig is returned when NewClientConnStdlib is
+// passed an incompatible config (i.e., a config containing fields that
+// we don't know how to convert and whose value is not ~zero).
+var ErrIncompatibleStdlibConfig = errors.New("ootls: incompatible stdlib config")
+
+// NewClientConnStdlib is like Client but takes in input a *crypto/tls.Config
+// rather than a *github.com/ooni/oocrypto/tls.Config.
+//
+// The config cannot be nil: users must set either ServerName or
+// InsecureSkipVerify in the config.
+//
+// This function will return ErrIncompatibleStdlibConfig if unsupported
+// fields have a nonzero value, because the resulting Conn will not
+// be compatible with the configuration you provided us with.
+//
+// We currently support these fields:
+//
+// - DynamicRecordSizingDisabled
+//
+// - InsecureSkipVerify
+//
+// - MaxVersion
+//
+// - MinVersion
+//
+// - NextProtos
+//
+// - RootCAs
+//
+// - ServerName
+func NewClientConnStdlib(conn net.Conn, config *tls.Config) (*Conn, error) {
+	supportedFields := map[string]bool{
+		"DynamicRecordSizingDisabled": true,
+		"InsecureSkipVerify":          true,
+		"MaxVersion":                  true,
+		"MinVersion":                  true,
+		"NextProtos":                  true,
+		"RootCAs":                     true,
+		"ServerName":                  true,
+	}
+	value := reflect.ValueOf(config).Elem()
+	kind := value.Type()
+	for idx := 0; idx < value.NumField(); idx++ {
+		field := value.Field(idx)
+		if field.IsZero() {
+			continue
+		}
+		fieldKind := kind.Field(idx)
+		if supportedFields[fieldKind.Name] {
+			continue
+		}
+		err := fmt.Errorf("%w: field %s is nonzero", ErrIncompatibleStdlibConfig, fieldKind.Name)
+		return nil, err
+	}
+	ourConfig := &Config{
+		DynamicRecordSizingDisabled: config.DynamicRecordSizingDisabled,
+		InsecureSkipVerify:          config.InsecureSkipVerify,
+		MaxVersion:                  config.MaxVersion,
+		MinVersion:                  config.MinVersion,
+		NextProtos:                  config.NextProtos,
+		RootCAs:                     config.RootCAs,
+		ServerName:                  config.ServerName,
+	}
+	return Client(conn, ourConfig), nil
+}

tls/stdlibwrapper_test.go

@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+package tls
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"net"
+	"testing"
+	"time"
+)
+
+func TestNewClientConnStdlib(t *testing.T) {
+	tests := []struct {
+		name   string
+		config *tls.Config
+		err    error
+	}{{
+		name: "with only supported config fields",
+		config: &tls.Config{
+			DynamicRecordSizingDisabled: true,
+			RootCAs:                     x509.NewCertPool(),
+			ServerName:                  "ooni.org",
+			InsecureSkipVerify:          true,
+			MinVersion:                  VersionTLS10,
+			MaxVersion:                  VersionTLS13,
+			NextProtos:                  []string{"h3"},
+		},
+		err: nil,
+	}, {
+		name: "with unsupported fields",
+		config: &tls.Config{
+			Time: func() time.Time {
+				return time.Now()
+			},
+		},
+		err: ErrIncompatibleStdlibConfig,
+	}}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			conn, err := net.Dial("udp", "8.8.8.8:443") // we just want a valid conn
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer conn.Close()
+			got, err := NewClientConnStdlib(conn, tt.config)
+			if !errors.Is(err, tt.err) {
+				t.Fatal("unexpected error", err)
+			}
+			if err == nil && got == nil {
+				t.Fatal("expected non-nil conn here")
+			}
+		})
+	}
+}