feat: add --extra-header flag for custom gRPC headers

internal/client/client.go

@@ -21,6 +21,7 @@
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/metadata"
 
 	v1 "github.com/authzed/authzed-go/proto/authzed/api/v1"
 	"github.com/authzed/authzed-go/v1"
@@ -214,6 +215,43 @@
 	}
 }
 
+func extraHeadersUnaryInterceptor(headers map[string]string) grpc.UnaryClientInterceptor {
+	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+		if len(headers) > 0 {
+			md := metadata.New(headers)
+			ctx = metadata.NewOutgoingContext(ctx, md)
+		}
+		return invoker(ctx, method, req, reply, cc, opts...)
+	}
+}
+
+func extraHeadersStreamInterceptor(headers map[string]string) grpc.StreamClientInterceptor {
+	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+		if len(headers) > 0 {
+			md := metadata.New(headers)
+			ctx = metadata.NewOutgoingContext(ctx, md)
+		}
+		return streamer(ctx, desc, cc, method, opts...)
+	}
+}
+
+func parseExtraHeaders(headerStrings []string) (map[string]string, error) {
+	headers := make(map[string]string)
+	for _, headerStr := range headerStrings {
+		parts := strings.SplitN(headerStr, "=", 2)
+		if len(parts) != 2 {
+			return nil, fmt.Errorf("invalid header format '%s': expected 'key=value'", headerStr)
+		}
+		key := strings.TrimSpace(parts[0])
+		value := strings.TrimSpace(parts[1])
+		if key == "" {
+			return nil, fmt.Errorf("invalid header format '%s': key cannot be empty", headerStr)
+		}
+		headers[key] = value
+	}
+	return headers, nil
+}
+
 // DialOptsFromFlags returns the dial options from the CLI-specified flags.
 func DialOptsFromFlags(cmd *cobra.Command, token storage.Token) ([]grpc.DialOption, error) {
 	maxRetries := cobrautil.MustGetUint(cmd, "max-retries")
@@ -239,6 +277,17 @@
 		selector.StreamClientInterceptor(retry.StreamClientInterceptor(retryOpts...), selector.MatchFunc(isNoneOf(importBulkRoute, exportBulkRoute, watchRoute))),
 	}
 
+	// Parse and add extra headers if provided
+	extraHeaderStrings := cobrautil.MustGetStringSlice(cmd, "extra-header")
+	if len(extraHeaderStrings) > 0 {
+		headers, err := parseExtraHeaders(extraHeaderStrings)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse extra headers: %w", err)
+		}
+		unaryInterceptors = append(unaryInterceptors, extraHeadersUnaryInterceptor(headers))
+		streamInterceptors = append(streamInterceptors, extraHeadersStreamInterceptor(headers))
+	}
+
 	if !cobrautil.MustGetBool(cmd, "skip-version-check") {
 		unaryInterceptors = append(unaryInterceptors, zgrpcutil.CheckServerVersion)
 	}

internal/client/client_test.go

@@ -180,6 +180,7 @@ func TestRetries(t *testing.T) {
 		zedtesting.StringFlag{FlagName: "proxy", FlagValue: "", Changed: true},
 		zedtesting.StringFlag{FlagName: "hostname-override", FlagValue: "", Changed: true},
 		zedtesting.IntFlag{FlagName: "max-message-size", FlagValue: 1000, Changed: true},
+		zedtesting.StringSliceFlag{FlagName: "extra-header", FlagValue: []string{}, Changed: false},
 	)
 	dialOpts, err := client.DialOptsFromFlags(cmd, storage.Token{Insecure: &secure})
 	require.NoError(t, err)
@@ -224,6 +225,7 @@ func TestDoesNotRetry(t *testing.T) {
 		zedtesting.StringFlag{FlagName: "proxy", FlagValue: "", Changed: true},
 		zedtesting.StringFlag{FlagName: "hostname-override", FlagValue: "", Changed: true},
 		zedtesting.IntFlag{FlagName: "max-message-size", FlagValue: 1000, Changed: true},
+		zedtesting.StringSliceFlag{FlagName: "extra-header", FlagValue: []string{}, Changed: false},
 	)
 	dialOpts, err := client.DialOptsFromFlags(cmd, storage.Token{Insecure: &secure})
 	require.NoError(t, err)

internal/cmd/cmd.go

@@ -91,6 +91,7 @@ zed permission check --explain document:firstdoc writer user:emilia
 	rootCmd.PersistentFlags().Int("max-message-size", 0, "maximum size *in bytes* (defaults to 4_194_304 bytes ~= 4MB) of a gRPC message that can be sent or received by zed")
 	rootCmd.PersistentFlags().String("proxy", "", "specify a SOCKS5 proxy address")
 	rootCmd.PersistentFlags().Uint("max-retries", 10, "maximum number of sequential retries to attempt when a request fails")
+	rootCmd.PersistentFlags().StringSlice("extra-header", []string{}, "extra header(s) to add to gRPC requests in the format 'key=value' (can be specified multiple times)")
 	_ = rootCmd.PersistentFlags().MarkHidden("debug") // This cannot return its error.
 
 	versionCmd := &cobra.Command{

internal/testing/test_helpers.go

@@ -74,6 +74,12 @@ type StringFlag struct {
 	Changed   bool
 }
 
+type StringSliceFlag struct {
+	FlagName  string
+	FlagValue []string
+	Changed   bool
+}
+
 type BoolFlag struct {
 	FlagName  string
 	FlagValue bool
@@ -116,6 +122,9 @@ func CreateTestCobraCommandWithFlagValue(t *testing.T, flagAndValues ...any) *co
 		case StringFlag:
 			c.Flags().String(f.FlagName, f.FlagValue, "")
 			c.Flag(f.FlagName).Changed = f.Changed
+		case StringSliceFlag:
+			c.Flags().StringSlice(f.FlagName, f.FlagValue, "")
+			c.Flag(f.FlagName).Changed = f.Changed
 		case BoolFlag:
 			c.Flags().Bool(f.FlagName, f.FlagValue, "")
 			c.Flag(f.FlagName).Changed = f.Changed