feat: Add custom HTTP header management via CLI flags and config files

cmd/cloudflared/tunnel/cmd.go

@@ -1056,6 +1056,19 @@ func configureProxyFlags(shouldHide bool) []cli.Flag {
 			Hidden:  shouldHide,
 			Value:   false,
 		}),
+		altsrc.NewStringSliceFlag(&cli.StringSliceFlag{
+			Name:    "header",
+			Aliases: []string{"H"},
+			Usage:   "Add custom header when forwarding to origin (format: 'Name: Value')",
+			EnvVars: []string{"TUNNEL_HEADERS"},
+			Hidden:  shouldHide,
+		}),
+		altsrc.NewStringSliceFlag(&cli.StringSliceFlag{
+			Name:    "remove-header",
+			Usage:   "Remove header when forwarding to origin",
+			EnvVars: []string{"TUNNEL_REMOVE_HEADERS"},
+			Hidden:  shouldHide,
+		}),
 		altsrc.NewStringFlag(&cli.StringFlag{
 			Name:    cfdflags.ManagementHostname,
 			Usage:   "Management hostname to signify incoming management requests",

config/configuration.go

@@ -231,6 +231,10 @@ type OriginRequestConfig struct {
 	Http2Origin *bool `yaml:"http2Origin" json:"http2Origin,omitempty"`
 	// Access holds all access related configs
 	Access *AccessConfig `yaml:"access" json:"access,omitempty"`
+	// Custom headers to add/modify when forwarding to origin
+	Headers map[string]string `yaml:"headers" json:"headers,omitempty"`
+	// Headers to remove when forwarding to origin
+	RemoveHeaders []string `yaml:"removeHeaders" json:"removeHeaders,omitempty"`
 }
 
 type AccessConfig struct {

ingress/config.go

@@ -2,6 +2,7 @@ package ingress
 
 import (
 	"encoding/json"
+	"strings"
 	"time"
 
 	"github.com/urfave/cli/v2"
@@ -137,6 +138,16 @@ func originRequestFromSingleRule(c *cli.Context) OriginRequestConfig {
 	var proxyPort uint
 	var proxyType string
 	var http2Origin bool
+
+	var cliHeaders map[string]string
+	var cliRemoveHeaders []string
+	if c.IsSet("header") {
+		cliHeaders = parseHeadersFromCLI(c)
+	}
+	if c.IsSet("remove-header") {
+		cliRemoveHeaders = parseRemoveHeadersFromCLI(c)
+	}
+
 	if flag := ProxyConnectTimeoutFlag; c.IsSet(flag) {
 		connectTimeout = config.CustomDuration{Duration: c.Duration(flag)}
 	}
@@ -209,6 +220,8 @@ func originRequestFromSingleRule(c *cli.Context) OriginRequestConfig {
 		ProxyPort:              proxyPort,
 		ProxyType:              proxyType,
 		Http2Origin:            http2Origin,
+		Headers:                cliHeaders,
+		RemoveHeaders:          cliRemoveHeaders,
 	}
 }
 
@@ -333,6 +346,12 @@ type OriginRequestConfig struct {
 
 	// Access holds all access related configs
 	Access config.AccessConfig `yaml:"access" json:"access,omitempty"`
+
+	// Custom headers to add/modify when forwarding to origin
+	Headers map[string]string `yaml:"headers" json:"headers,omitempty"`
+
+	// Headers to remove when forwarding to origin
+	RemoveHeaders []string `yaml:"removeHeaders" json:"removeHeaders,omitempty"`
 }
 
 func (defaults *OriginRequestConfig) setConnectTimeout(overrides config.OriginRequestConfig) {
@@ -456,6 +475,26 @@ func (defaults *OriginRequestConfig) setAccess(overrides config.OriginRequestCon
 	}
 }
 
+func (defaults *OriginRequestConfig) setHeaders(overrides config.OriginRequestConfig) {
+	if overrides.Headers != nil {
+		if defaults.Headers == nil {
+			defaults.Headers = make(map[string]string)
+		}
+		for k, v := range overrides.Headers {
+			defaults.Headers[k] = v
+		}
+	}
+}
+
+func (defaults *OriginRequestConfig) setRemoveHeaders(overrides config.OriginRequestConfig) {
+	if overrides.RemoveHeaders != nil {
+		if defaults.RemoveHeaders == nil {
+			defaults.RemoveHeaders = make([]string, 0)
+		}
+		defaults.RemoveHeaders = append(defaults.RemoveHeaders, overrides.RemoveHeaders...)
+	}
+}
+
 // SetConfig gets config for the requests that cloudflared sends to origins.
 // Each field has a setter method which sets a value for the field by trying to find:
 //  1. The user config for this rule
@@ -485,6 +524,8 @@ func setConfig(defaults OriginRequestConfig, overrides config.OriginRequestConfi
 	cfg.setIPRules(overrides)
 	cfg.setHttp2Origin(overrides)
 	cfg.setAccess(overrides)
+	cfg.setHeaders(overrides)
+	cfg.setRemoveHeaders(overrides)
 
 	return cfg
 }
@@ -540,6 +581,8 @@ func ConvertToRawOriginConfig(c OriginRequestConfig) config.OriginRequestConfig
 		IPRules:                convertToRawIPRules(c.IPRules),
 		Http2Origin:            defaultBoolToNil(c.Http2Origin),
 		Access:                 access,
+		Headers:                c.Headers,
+		RemoveHeaders:          c.RemoveHeaders,
 	}
 }
 
@@ -583,3 +626,58 @@ func zeroUIntToNil(v uint) *uint {
 
 	return &v
 }
+
+func parseHeadersFromCLI(c *cli.Context) map[string]string {
+	headers := make(map[string]string)
+
+	if c.IsSet("header") {
+		headerFlags := c.StringSlice("header")
+		for _, headerFlag := range headerFlags {
+			if name, value, valid := parseHeaderFlag(headerFlag); valid {
+				headers[name] = value
+			}
+		}
+	}
+
+	return headers
+}
+
+func parseRemoveHeadersFromCLI(c *cli.Context) []string {
+	if c.IsSet("remove-header") {
+		return c.StringSlice("remove-header")
+	}
+	return nil
+}
+
+func parseHeaderFlag(headerFlag string) (name, value string, valid bool) {
+	parts := strings.SplitN(headerFlag, ":", 2)
+	if len(parts) != 2 {
+		return "", "", false
+	}
+
+	name = strings.TrimSpace(parts[0])
+	value = strings.TrimSpace(parts[1])
+
+	if name == "" || value == "" || !isValidHeaderName(name) {
+		return "", "", false
+	}
+
+	return name, value, true
+}
+
+func isValidHeaderName(name string) bool {
+	if name == "" || strings.Contains(name, ":") {
+		return false
+	}
+	if strings.ContainsAny(name, " \t\r\n") {
+		return false
+	}
+	if strings.TrimSpace(name) == "" {
+		return false
+	}
+	if len(name) > 256 {
+		return false
+	}
+
+	return true
+}

ingress/config_test.go

@@ -3,6 +3,7 @@ package ingress
 import (
 	"encoding/json"
 	"flag"
+	"strings"
 	"testing"
 	"time"
 
@@ -12,6 +13,7 @@ import (
 
 	"github.com/cloudflare/cloudflared/config"
 	"github.com/cloudflare/cloudflared/ipaccess"
+	"github.com/stretchr/testify/assert"
 )
 
 // Ensure that the nullable config from `config` package and the
@@ -415,6 +417,187 @@ func TestDefaultConfigFromCLI(t *testing.T) {
 	require.Equal(t, expected, actual)
 }
 
+func TestOriginRequestConfigHeaders(t *testing.T) {
+	config := OriginRequestConfig{
+		Headers: map[string]string{
+			"X-Custom-Header": "custom-value",
+			"Authorization":    "Bearer token123",
+		},
+		RemoveHeaders: []string{"X-Unwanted", "Server"},
+	}
+
+	jsonData, err := json.Marshal(config)
+	assert.NoError(t, err)
+	assert.Contains(t, string(jsonData), "X-Custom-Header")
+	assert.Contains(t, string(jsonData), "custom-value")
+	assert.Contains(t, string(jsonData), "X-Unwanted")
+
+	var unmarshaled OriginRequestConfig
+	err = json.Unmarshal(jsonData, &unmarshaled)
+	assert.NoError(t, err)
+	assert.Equal(t, "custom-value", unmarshaled.Headers["X-Custom-Header"])
+	assert.Equal(t, "Bearer token123", unmarshaled.Headers["Authorization"])
+	assert.Contains(t, unmarshaled.RemoveHeaders, "X-Unwanted")
+	assert.Contains(t, unmarshaled.RemoveHeaders, "Server")
+}
+
+func TestParseHeaderFlag(t *testing.T) {
+	name, value, valid := parseHeaderFlag("X-Custom-Header: custom-value")
+	assert.True(t, valid)
+	assert.Equal(t, "X-Custom-Header", name)
+	assert.Equal(t, "custom-value", value)
+
+	name, value, valid = parseHeaderFlag("  Authorization  :  Bearer token  ")
+	assert.True(t, valid)
+	assert.Equal(t, "Authorization", name)
+	assert.Equal(t, "Bearer token", value)
+
+	name, value, valid = parseHeaderFlag("X-Header:   ")
+	assert.False(t, valid)
+
+	name, value, valid = parseHeaderFlag("   : value")
+	assert.False(t, valid)
+
+	_, _, valid = parseHeaderFlag("invalid-format")
+	assert.False(t, valid)
+
+	_, _, valid = parseHeaderFlag(": value-only")
+	assert.False(t, valid)
+
+	_, _, valid = parseHeaderFlag("name-only:")
+	assert.False(t, valid)
+
+	_, _, valid = parseHeaderFlag("")
+	assert.False(t, valid)
+
+	name, value, valid = parseHeaderFlag("X-Special: value with @#$%^&*()")
+	assert.True(t, valid)
+	assert.Equal(t, "X-Special", name)
+	assert.Equal(t, "value with @#$%^&*()", value)
+
+	name, value, valid = parseHeaderFlag("X-URL: https://example.com:8080/path")
+	assert.True(t, valid)
+	assert.Equal(t, "X-URL", name)
+	assert.Equal(t, "https://example.com:8080/path", value)
+}
+
+func TestIsValidHeaderName(t *testing.T) {
+	assert.True(t, isValidHeaderName("X-Custom-Header"))
+	assert.True(t, isValidHeaderName("Authorization"))
+	assert.True(t, isValidHeaderName("Content-Type"))
+	assert.True(t, isValidHeaderName("X-API-Key"))
+	assert.True(t, isValidHeaderName("User-Agent"))
+
+	assert.False(t, isValidHeaderName(""))
+	assert.False(t, isValidHeaderName(" "))
+	assert.False(t, isValidHeaderName("\t"))
+	assert.False(t, isValidHeaderName("\n"))
+	assert.False(t, isValidHeaderName("\r"))
+
+	assert.False(t, isValidHeaderName("Header With Space"))
+	assert.False(t, isValidHeaderName("Header\tWith\tTab"))
+	assert.False(t, isValidHeaderName("Header\nWith\nNewline"))
+	assert.False(t, isValidHeaderName("Header\rWith\rCarriageReturn"))
+
+	assert.False(t, isValidHeaderName(":Header"))
+	assert.False(t, isValidHeaderName("Header:"))
+	assert.False(t, isValidHeaderName("Header::Value"))
+
+	longHeader := strings.Repeat("A", 257)
+	assert.False(t, isValidHeaderName(longHeader))
+
+	boundaryHeader := strings.Repeat("A", 256)
+	assert.True(t, isValidHeaderName(boundaryHeader))
+
+	assert.True(t, isValidHeaderName("X"))
+	assert.True(t, isValidHeaderName("a"))
+	assert.True(t, isValidHeaderName("1"))
+
+	assert.True(t, isValidHeaderName("X-Header"))
+	assert.True(t, isValidHeaderName("X_Header"))
+	assert.True(t, isValidHeaderName("X.Header"))
+}
+
+func TestParseHeadersFromCLI(t *testing.T) {
+	app := cli.NewApp()
+	app.Flags = []cli.Flag{
+		&cli.StringSliceFlag{
+			Name: "header",
+		},
+	}
+
+	app.Action = func(c *cli.Context) error {
+		headers := parseHeadersFromCLI(c)
+
+		assert.Equal(t, 3, len(headers))
+		assert.Equal(t, "test-value", headers["X-Test-Header"])
+		assert.Equal(t, "static-key-123", headers["X-API-Key"])
+		assert.Equal(t, "Bearer token", headers["Authorization"])
+
+		assert.NotContains(t, headers, "Invalid-Header")
+		assert.NotContains(t, headers, "X-Empty")
+
+		return nil
+	}
+
+	err := app.Run([]string{"app", "--header", "X-Test-Header: test-value", "--header", "X-API-Key: static-key-123", "--header", "Authorization: Bearer token", "--header", "Invalid-Header", "--header", "X-Empty: "})
+	assert.NoError(t, err)
+}
+
+func TestParseRemoveHeadersFromCLI(t *testing.T) {
+	app := cli.NewApp()
+	app.Flags = []cli.Flag{
+		&cli.StringSliceFlag{
+			Name: "remove-header",
+		},
+	}
+
+	app.Action = func(c *cli.Context) error {
+		removeHeaders := parseRemoveHeadersFromCLI(c)
+
+		assert.Equal(t, 3, len(removeHeaders))
+		assert.Contains(t, removeHeaders, "X-Unwanted")
+		assert.Contains(t, removeHeaders, "Server")
+		assert.Contains(t, removeHeaders, "User-Agent")
+
+		return nil
+	}
+
+	err := app.Run([]string{"app", "--remove-header", "X-Unwanted", "--remove-header", "Server", "--remove-header", "User-Agent"})
+	assert.NoError(t, err)
+}
+
+func TestParseHeadersFromCLINotSet(t *testing.T) {
+	app := cli.NewApp()
+
+	app.Action = func(c *cli.Context) error {
+		headers := parseHeadersFromCLI(c)
+
+		assert.Equal(t, 0, len(headers))
+		assert.NotNil(t, headers)
+
+		return nil
+	}
+
+	err := app.Run([]string{"app"})
+	assert.NoError(t, err)
+}
+
+func TestParseRemoveHeadersFromCLINotSet(t *testing.T) {
+	app := cli.NewApp()
+
+	app.Action = func(c *cli.Context) error {
+		removeHeaders := parseRemoveHeadersFromCLI(c)
+
+		assert.Nil(t, removeHeaders)
+
+		return nil
+	}
+
+	err := app.Run([]string{"app"})
+	assert.NoError(t, err)
+}
+
 func newIPRule(t *testing.T, prefix string, ports []int, allow bool) ipaccess.Rule {
 	rule, err := ipaccess.NewRuleByCIDR(&prefix, ports, allow)
 	require.NoError(t, err)