allow pomerium to be embedded as a library (#3415)

.gitignore

@@ -90,8 +90,8 @@ docs/.vuepress/dist/
 .service-accounts
 
 /bazel-*
-internal/envoy/files/envoy-*-?????
+pkg/envoy/files/envoy-*-?????
-internal/envoy/files/envoy-*-?????.sha256
+pkg/envoy/files/envoy-*-?????.sha256
-internal/envoy/files/envoy-*-?????.version
+pkg/envoy/files/envoy-*-?????.version
 
 yarn-error.log

Makefile

@@ -113,8 +113,8 @@ clean: ## Cleanup any build binaries or packages.
 	@echo "==> $@"
 	$(RM) -r $(BINDIR)
 	$(RM) -r $(BUILDDIR)
-	$(RM) internal/envoy/files/envoy-*
+	$(RM) pkg/envoy/files/envoy-*
-	$(RM) $GOPATH/bin/protoc-gen-validate
+	$(RM) $(GOPATH)/bin/protoc-gen-validate
 	$(RM) -r /tmp/pomerium-protoc
 	$(RM) -r /tmp/pomerium-protoc-3pp
 

cmd/pomerium/main.go

@@ -6,10 +6,13 @@ import (
 	"flag"
 	"fmt"
 
-	"github.com/pomerium/pomerium/internal/cmd/pomerium"
+	"github.com/rs/zerolog"
-	"github.com/pomerium/pomerium/internal/envoy/files"
+
+	"github.com/pomerium/pomerium/config"
 	"github.com/pomerium/pomerium/internal/log"
 	"github.com/pomerium/pomerium/internal/version"
+	"github.com/pomerium/pomerium/pkg/cmd/pomerium"
+	"github.com/pomerium/pomerium/pkg/envoy/files"
 )
 
 var (
@@ -33,5 +36,16 @@ func main() {
 }
 
 func run(ctx context.Context) error {
-	return pomerium.Run(ctx, *configFile)
+	ctx = log.WithContext(ctx, func(c zerolog.Context) zerolog.Context {
+		return c.Str("config_file_source", *configFile).Bool("bootstrap", true)
+	})
+
+	var src config.Source
+
+	src, err := config.NewFileOrEnvironmentSource(*configFile, files.FullVersion())
+	if err != nil {
+		return err
+	}
+
+	return pomerium.Run(ctx, src)
 }

config/config.go

@@ -4,6 +4,7 @@ import (
 	"crypto/tls"
 
 	"github.com/pomerium/pomerium/internal/hashutil"
+	"github.com/pomerium/pomerium/internal/netutil"
 )
 
 // Config holds pomerium configuration options.
@@ -58,3 +59,19 @@ func (cfg *Config) AllCertificates() ([]tls.Certificate, error) {
 func (cfg *Config) Checksum() uint64 {
 	return hashutil.MustHash(cfg)
 }
+
+// AllocatePorts populates
+func (cfg *Config) AllocatePorts() error {
+	ports, err := netutil.AllocatePorts(5)
+	if err != nil {
+		return err
+	}
+
+	cfg.GRPCPort = ports[0]
+	cfg.HTTPPort = ports[1]
+	cfg.OutboundPort = ports[2]
+	cfg.MetricsPort = ports[3]
+	cfg.DebugPort = ports[4]
+
+	return nil
+}

config/config_source.go

@@ -3,6 +3,7 @@ package config
 import (
 	"context"
 	"crypto/sha256"
+	"fmt"
 	"os"
 	"sync"
 
@@ -11,7 +12,6 @@ import (
 
 	"github.com/pomerium/pomerium/internal/fileutil"
 	"github.com/pomerium/pomerium/internal/log"
-	"github.com/pomerium/pomerium/internal/netutil"
 	"github.com/pomerium/pomerium/internal/telemetry/metrics"
 )
 
@@ -110,26 +110,15 @@ func NewFileOrEnvironmentSource(
 		return nil, err
 	}
 
-	ports, err := netutil.AllocatePorts(5)
-	if err != nil {
-		return nil, err
-	}
-	grpcPort := ports[0]
-	httpPort := ports[1]
-	outboundPort := ports[2]
-	metricsPort := ports[3]
-	debugPort := ports[4]
-
 	cfg := &Config{
 		Options:      options,
 		EnvoyVersion: envoyVersion,
-
-		GRPCPort:     grpcPort,
-		HTTPPort:     httpPort,
-		OutboundPort: outboundPort,
-		MetricsPort:  metricsPort,
-		DebugPort:    debugPort,
 	}
+
+	if err = cfg.AllocatePorts(); err != nil {
+		return nil, fmt.Errorf("allocating ports: %w", err)
+	}
+
 	metrics.SetConfigInfo(ctx, cfg.Options.Services, "local", cfg.Checksum(), true)
 
 	src := &FileOrEnvironmentSource{

databroker/cache.go

@@ -16,7 +16,6 @@ import (
 
 	"github.com/pomerium/pomerium/config"
 	"github.com/pomerium/pomerium/internal/directory"
-	"github.com/pomerium/pomerium/internal/envoy/files"
 	"github.com/pomerium/pomerium/internal/events"
 	"github.com/pomerium/pomerium/internal/identity"
 	"github.com/pomerium/pomerium/internal/identity/manager"
@@ -24,6 +23,7 @@ import (
 	"github.com/pomerium/pomerium/internal/telemetry"
 	"github.com/pomerium/pomerium/internal/version"
 	"github.com/pomerium/pomerium/pkg/cryptutil"
+	"github.com/pomerium/pomerium/pkg/envoy/files"
 	"github.com/pomerium/pomerium/pkg/grpc/databroker"
 	"github.com/pomerium/pomerium/pkg/grpc/registry"
 	"github.com/pomerium/pomerium/pkg/grpcutil"

internal/controlplane/server.go

@@ -21,7 +21,6 @@ import (
 	"github.com/pomerium/pomerium/config/envoyconfig"
 	"github.com/pomerium/pomerium/config/envoyconfig/filemgr"
 	"github.com/pomerium/pomerium/internal/controlplane/xdsmgr"
-	"github.com/pomerium/pomerium/internal/envoy/files"
 	"github.com/pomerium/pomerium/internal/events"
 	"github.com/pomerium/pomerium/internal/httputil/reproxy"
 	"github.com/pomerium/pomerium/internal/log"
@@ -29,6 +28,7 @@ import (
 	"github.com/pomerium/pomerium/internal/telemetry/requestid"
 	"github.com/pomerium/pomerium/internal/urlutil"
 	"github.com/pomerium/pomerium/internal/version"
+	"github.com/pomerium/pomerium/pkg/envoy/files"
 	pom_grpc "github.com/pomerium/pomerium/pkg/grpc"
 	"github.com/pomerium/pomerium/pkg/grpcutil"
 )

internal/envoy/embed.go

@@ -1,71 +0,0 @@
-package envoy
-
-import (
-	"bytes"
-	"context"
-	"fmt"
-	"io/fs"
-	"os"
-	"path/filepath"
-	"sync"
-
-	"github.com/natefinch/atomic"
-
-	"github.com/pomerium/pomerium/internal/envoy/files"
-	"github.com/pomerium/pomerium/internal/log"
-)
-
-const (
-	embeddedEnvoyPermissions     fs.FileMode = 0o700
-	embeddedDirectoryPermissions fs.FileMode = 0o755
-)
-
-// OverrideEnvoyPath is an override for using an envoy path instead of the embedded envoy path.
-var OverrideEnvoyPath = ""
-
-var (
-	embeddedFilesBaseDirectory = filepath.Join(os.TempDir(), "pomerium-embedded-files")
-	extractEmbeddedEnvoyOnce   sync.Once
-)
-
-func extractEmbeddedEnvoy(ctx context.Context) (outPath string, err error) {
-	extractEmbeddedEnvoyOnce.Do(func() {
-		// clean up our base directory before starting
-		err = os.RemoveAll(embeddedFilesBaseDirectory)
-		if err != nil {
-			err = fmt.Errorf("error cleaning embedded file directory: (directory=%s): %w", embeddedFilesBaseDirectory, err)
-			return
-		}
-
-		// create known directory base to clean at startup
-		err = os.MkdirAll(embeddedFilesBaseDirectory, embeddedDirectoryPermissions)
-		if err != nil {
-			err = fmt.Errorf("error creating embedded file directory: (directory=%s): %w", embeddedFilesBaseDirectory, err)
-			return
-		}
-
-		// build a random temp directory inside our base directory to guarantee permissions
-		var tmpDir string
-		tmpDir, err = os.MkdirTemp(embeddedFilesBaseDirectory, "envoy-")
-		if err != nil {
-			err = fmt.Errorf("error creating embedded file tmp directory: (directory=%s): %w", embeddedFilesBaseDirectory, err)
-			return
-		}
-
-		outPath = filepath.Join(tmpDir, "envoy")
-
-		log.Info(ctx).Str("path", outPath).Msg("extracting envoy binary")
-		err = atomic.WriteFile(outPath, bytes.NewReader(files.Binary()))
-		if err != nil {
-			err = fmt.Errorf("error extracting embedded envoy binary to temporary directory (path=%s): %w", outPath, err)
-			return
-		}
-
-		err = os.Chmod(outPath, embeddedEnvoyPermissions)
-		if err != nil {
-			err = fmt.Errorf("error chmoding embedded envoy binary: %w", err)
-			return
-		}
-	})
-	return outPath, err
-}

pkg/cmd/pomerium/pomerium.go

@@ -11,7 +11,6 @@ import (
 	"syscall"
 
 	envoy_service_auth_v3 "github.com/envoyproxy/go-control-plane/envoy/service/auth/v3"
-	"github.com/rs/zerolog"
 	"golang.org/x/sync/errgroup"
 
 	"github.com/pomerium/pomerium/authenticate"
@@ -21,29 +20,22 @@ import (
 	"github.com/pomerium/pomerium/internal/autocert"
 	"github.com/pomerium/pomerium/internal/controlplane"
 	"github.com/pomerium/pomerium/internal/databroker"
-	"github.com/pomerium/pomerium/internal/envoy"
-	"github.com/pomerium/pomerium/internal/envoy/files"
 	"github.com/pomerium/pomerium/internal/events"
 	"github.com/pomerium/pomerium/internal/log"
 	"github.com/pomerium/pomerium/internal/registry"
 	"github.com/pomerium/pomerium/internal/version"
+	"github.com/pomerium/pomerium/pkg/envoy"
+	"github.com/pomerium/pomerium/pkg/envoy/files"
 	"github.com/pomerium/pomerium/proxy"
 )
 
 // Run runs the main pomerium application.
-func Run(ctx context.Context, configFile string) error {
+func Run(ctx context.Context, src config.Source) error {
 	log.Info(ctx).
 		Str("envoy_version", files.FullVersion()).
 		Str("version", version.FullVersion()).
 		Msg("cmd/pomerium")
 
-	var src config.Source
-
-	src, err := config.NewFileOrEnvironmentSource(configFile, files.FullVersion())
-	if err != nil {
-		return err
-	}
-
 	src = databroker.NewConfigSource(ctx, src)
 	logMgr := config.NewLogManager(ctx, src)
 	defer logMgr.Close()
@@ -51,7 +43,7 @@ func Run(ctx context.Context, configFile string) error {
 	// trigger changes when underlying files are changed
 	src = config.NewFileWatcherSource(src)
 
-	src, err = autocert.New(src)
+	src, err := autocert.New(src)
 	if err != nil {
 		return err
 	}
@@ -78,9 +70,7 @@ func Run(ctx context.Context, configFile string) error {
 			}
 		})
 
-	if err = controlPlane.OnConfigChange(log.WithContext(ctx, func(c zerolog.Context) zerolog.Context {
+	if err = controlPlane.OnConfigChange(ctx, src.GetConfig()); err != nil {
-		return c.Str("config_file_source", configFile).Bool("bootstrap", true)
-	}), src.GetConfig()); err != nil {
 		return fmt.Errorf("applying config: %w", err)
 	}
 

pkg/cmd/pomerium/pomerium_test.go

@@ -1,20 +1,36 @@
-package pomerium
+package pomerium_test
 
 import (
 	"context"
 	"os"
 	"testing"
 	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/pomerium/pomerium/config"
+	"github.com/pomerium/pomerium/pkg/cmd/pomerium"
+	"github.com/pomerium/pomerium/pkg/envoy/files"
 )
 
 func Test_run(t *testing.T) {
 	os.Clearenv()
+
+	run := func(ctx context.Context, configFile string) error {
+		src, err := config.NewFileOrEnvironmentSource(configFile, files.FullVersion())
+		if err != nil {
+			return err
+		}
+
+		return pomerium.Run(ctx, src)
+	}
+
 	tests := []struct {
 		name           string
 		configFileFlag string
-		wantErr        bool
+		check          func(require.TestingT, error, ...any)
 	}{
-		{"nil configuration", "", true},
+		{"nil configuration", "", require.Error},
 		{"bad proxy no authenticate url", `
 		{
 			"address": ":9433",
@@ -26,7 +42,7 @@ func Test_run(t *testing.T) {
 			"services": "proxy",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 		{"bad authenticate no cookie secret", `
 		{
 			"address": ":9433",
@@ -37,7 +53,7 @@ func Test_run(t *testing.T) {
 			"services": "authenticate",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 		{"bad authorize service bad shared key", `
 		{
 			"address": ":9433",
@@ -49,7 +65,7 @@ func Test_run(t *testing.T) {
 			"services": "authorize",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 		{"bad http port", `
 		{
 			"address": ":-1",
@@ -63,7 +79,7 @@ func Test_run(t *testing.T) {
 			"services": "proxy",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 		{"bad redirect port", `
 		{
 			"address": ":9433",
@@ -78,7 +94,7 @@ func Test_run(t *testing.T) {
 			"services": "proxy",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 		{"bad metrics port ", `
 		{
 			"address": ":9433",
@@ -92,7 +108,7 @@ func Test_run(t *testing.T) {
 			"services": "proxy",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 		{"malformed tracing provider", `
 		{
 			"tracing_provider": "bad tracing provider",
@@ -107,7 +123,7 @@ func Test_run(t *testing.T) {
 			"services": "proxy",
 			"policy": [{ "from": "https://pomerium.io", "to": "https://httpbin.org" }]
 		  }
-		`, true},
+		`, require.Error},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -115,7 +131,7 @@ func Test_run(t *testing.T) {
 			if err != nil {
 				t.Fatal("Cannot create temporary file", err)
 			}
-			defer os.Remove(tmpFile.Name())
+			defer func() { _ = os.Remove(tmpFile.Name()) }()
 			fn := tmpFile.Name()
 			if _, err := tmpFile.Write([]byte(tt.configFileFlag)); err != nil {
 				tmpFile.Close()
@@ -126,10 +142,7 @@ func Test_run(t *testing.T) {
 			ctx, clearTimeout := context.WithTimeout(context.Background(), 500*time.Millisecond)
 			defer clearTimeout()
 
-			err = Run(ctx, configFile)
+			tt.check(t, run(ctx, configFile))
-			if (err != nil) != tt.wantErr {
-				t.Errorf("run() error = %v, wantErr %v", err, tt.wantErr)
-			}
 		})
 	}
 }

pkg/envoy/envoy.go

@@ -5,13 +5,12 @@ import (
 	"bufio"
 	"bytes"
 	"context"
-	"crypto/sha256"
-	"encoding/hex"
 	"errors"
 	"fmt"
 	"io"
 	"os"
 	"os/exec"
+	"path"
 	"path/filepath"
 	"regexp"
 	"strconv"
@@ -30,14 +29,13 @@ import (
 
 	"github.com/pomerium/pomerium/config"
 	"github.com/pomerium/pomerium/config/envoyconfig"
-	"github.com/pomerium/pomerium/internal/envoy/files"
 	"github.com/pomerium/pomerium/internal/log"
 	"github.com/pomerium/pomerium/internal/telemetry"
+	"github.com/pomerium/pomerium/pkg/envoy/files"
 )
 
 const (
-	workingDirectoryName = ".pomerium-envoy"
+	configFileName = "envoy-config.yaml"
-	configFileName       = "envoy-config.yaml"
 )
 
 type serverOptions struct {
@@ -62,38 +60,13 @@ type Server struct {
 
 // NewServer creates a new server with traffic routed by envoy.
 func NewServer(ctx context.Context, src config.Source, builder *envoyconfig.Builder) (*Server, error) {
-	wd := filepath.Join(os.TempDir(), workingDirectoryName)
+	envoyPath, err := Extract()
-	err := os.MkdirAll(wd, embeddedEnvoyPermissions)
 	if err != nil {
-		return nil, fmt.Errorf("error creating temporary working directory for envoy: %w", err)
+		return nil, fmt.Errorf("extracting envoy: %w", err)
-	}
-
-	envoyPath := OverrideEnvoyPath
-	if envoyPath == "" {
-		envoyPath, err = extractEmbeddedEnvoy(ctx)
-		if err != nil {
-			return nil, fmt.Errorf("error extracting embedded envoy binary: %w", err)
-		}
-
-		// Checksum is written at build time, if it's not empty we verify the binary
-		if files.Checksum() != "" {
-			bs, err := os.ReadFile(envoyPath)
-			if err != nil {
-				return nil, fmt.Errorf("error reading envoy binary for checksum verification: %w", err)
-			}
-			h := sha256.New()
-			h.Write(bs)
-			s := hex.EncodeToString(h.Sum(nil))
-			if files.Checksum() != s {
-				return nil, fmt.Errorf("invalid envoy binary, expected %s but got %s", files.Checksum(), s)
-			}
-		} else {
-			log.Info(ctx).Msg("no checksum defined, envoy binary will not be verified!")
-		}
 	}
 
 	srv := &Server{
-		wd:        wd,
+		wd:        path.Dir(envoyPath),
 		builder:   builder,
 		grpcPort:  src.GetConfig().GRPCPort,
 		httpPort:  src.GetConfig().HTTPPort,

pkg/envoy/extract.go

@@ -0,0 +1,99 @@
+package envoy
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"hash"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+
+	"github.com/pomerium/pomerium/pkg/envoy/files"
+)
+
+const (
+	ownerRX              = os.FileMode(0o500)
+	maxExpandedEnvoySize = 1 << 30
+)
+
+type hashReader struct {
+	hash.Hash
+	r io.Reader
+}
+
+func (hr *hashReader) Read(p []byte) (n int, err error) {
+	n, err = hr.r.Read(p)
+	_, _ = hr.Write(p[:n])
+	return n, err
+}
+
+var (
+	setupLock          sync.Mutex
+	setupDone          bool
+	setupFullEnvoyPath string
+	setupErr           error
+)
+
+// Extract extracts envoy binary and returns its location
+func Extract() (fullEnvoyPath string, err error) {
+	setupLock.Lock()
+	defer setupLock.Unlock()
+
+	// if we've extract at least once, and the file we previously extracted no longer exists, force a new extraction
+	if setupFullEnvoyPath != "" {
+		if _, err := os.Stat(setupFullEnvoyPath); os.IsNotExist(err) {
+			setupDone = false
+		}
+	}
+	if setupDone {
+		return setupFullEnvoyPath, setupErr
+	}
+
+	dir, err := os.MkdirTemp(os.TempDir(), "pomerium-envoy")
+	if err != nil {
+		setupErr = fmt.Errorf("envoy: failed making temporary working dir: %w", err)
+		return
+	}
+	setupFullEnvoyPath = filepath.Join(dir, "envoy")
+
+	err = extract(setupFullEnvoyPath)
+	if err != nil {
+		setupErr = fmt.Errorf("envoy: failed to extract embedded envoy binary: %w", err)
+		return
+	}
+
+	setupDone = true
+	return setupFullEnvoyPath, setupErr
+}
+
+func extract(dstName string) (err error) {
+	checksum, err := hex.DecodeString(strings.Fields(files.Checksum())[0])
+	if err != nil {
+		return fmt.Errorf("checksum %s: %w", files.Checksum(), err)
+	}
+
+	hr := &hashReader{
+		Hash: sha256.New(),
+		r:    bytes.NewReader(files.Binary()),
+	}
+
+	dst, err := os.OpenFile(dstName, os.O_CREATE|os.O_WRONLY, ownerRX)
+	if err != nil {
+		return err
+	}
+	defer func() { err = dst.Close() }()
+
+	if _, err = io.Copy(dst, io.LimitReader(hr, maxExpandedEnvoySize)); err != nil {
+		return err
+	}
+
+	sum := hr.Sum(nil)
+	if !bytes.Equal(sum, checksum) {
+		return fmt.Errorf("expected %x, got %x checksum", checksum, sum)
+	}
+	return nil
+}

pkg/envoy/files/files_darwin_amd64.go

@@ -1,5 +1,4 @@
-//go:build darwin && amd64
+//go:build darwin && amd64 && !embed_pomerium
-// +build darwin,amd64
 
 package files
 

pkg/envoy/files/files_darwin_arm64.go

@@ -1,5 +1,5 @@
-//go:build darwin && arm64
+//go:build darwin && arm64 && !embed_pomerium
-// +build darwin,arm64
+// +build darwin,arm64,!embed_pomerium
 
 package files
 

pkg/envoy/files/files_external.go

@@ -0,0 +1,16 @@
+//go:build embed_pomerium
+
+package files
+
+var rawBinary []byte
+
+var rawChecksum string
+
+var rawVersion string
+
+// SetFiles sets external source for envoy
+func SetFiles(bin []byte, checksum, version string) {
+	rawBinary = bin
+	rawChecksum = checksum
+	rawVersion = version
+}

pkg/envoy/files/files_linux_amd64.go

@@ -1,5 +1,5 @@
-//go:build linux && amd64
+//go:build linux && amd64 && !embed_pomerium
-// +build linux,amd64
+// +build linux,amd64,!embed_pomerium
 
 package files
 

pkg/envoy/files/files_linux_arm64.go

@@ -1,5 +1,5 @@
-//go:build linux && arm64
+//go:build linux && arm64 && !embed_pomerium
-// +build linux,arm64
+// +build linux,arm64,!embed_pomerium
 
 package files
 

scripts/get-envoy.bash

@@ -6,22 +6,24 @@ export PATH
 
 _project_root="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)/.."
 _envoy_version=1.21.3
-_dir="$_project_root/internal/envoy/files"
+_dir="$_project_root/pkg/envoy/files"
 _target="${TARGET:-"$(go env GOOS)-$(go env GOARCH)"}"
 
 _url="https://github.com/pomerium/envoy-binaries/releases/download/v${_envoy_version}/envoy-${_target}"
 
 curl \
-  --compressed \
   --silent \
+  --fail \
+  --compressed \
   --location \
   --time-cond "$_dir/envoy-$_target" \
   --output "$_dir/envoy-$_target" \
   "$_url"
 
 curl \
-  --compressed \
   --silent \
+  --fail \
+  --compressed \
   --location \
   --time-cond "$_dir/envoy-$_target.sha256" \
   --output "$_dir/envoy-$_target.sha256" \

ui/embed.go

@@ -3,27 +3,18 @@ package ui
 
 import (
 	"bytes"
-	"embed"
 	"encoding/json"
-	"fmt"
 	"io"
-	"io/fs"
 	"net/http"
-	"os"
 	"path/filepath"
 	"time"
 
 	"github.com/pomerium/csrf"
 )
 
-var (
-	//go:embed dist/*
-	uiFS embed.FS
-)
-
 // ServeFile serves a file.
 func ServeFile(w http.ResponseWriter, r *http.Request, filePath string) error {
-	f, etag, err := openLocalOrEmbeddedFile(filepath.Join("dist", filePath))
+	f, etag, err := openFile(filepath.Join("dist", filePath))
 	if err != nil {
 		return err
 	}
@@ -47,7 +38,7 @@ func ServePage(w http.ResponseWriter, r *http.Request, page string, data map[str
 		return err
 	}
 
-	f, _, err := openLocalOrEmbeddedFile("dist/index.html")
+	f, _, err := openFile("dist/index.html")
 	if err != nil {
 		return err
 	}
@@ -67,27 +58,3 @@ func ServePage(w http.ResponseWriter, r *http.Request, page string, data map[str
 }
 
 var startTime = time.Now()
-
-func openLocalOrEmbeddedFile(name string) (f fs.File, etag string, err error) {
-	f, err = os.Open(filepath.Join("ui", name))
-	if os.IsNotExist(err) {
-		f, err = uiFS.Open(name)
-	}
-	if err != nil {
-		return nil, "", err
-	}
-
-	fi, err := f.Stat()
-	if err != nil {
-		_ = f.Close()
-		return nil, "", err
-	}
-
-	modTime := fi.ModTime()
-	if modTime.IsZero() {
-		modTime = startTime
-	}
-	etag = fmt.Sprintf("%x", modTime.UnixNano())
-
-	return f, etag, nil
-}

ui/embed_ext.go

@@ -0,0 +1,37 @@
+//go:build embed_pomerium
+
+package ui
+
+import (
+	"fmt"
+	"io/fs"
+)
+
+var (
+	// ExtUIFS must be set to provide access to UI dist/ files
+	ExtUIFS fs.FS
+)
+
+func openFile(name string) (f fs.File, etag string, err error) {
+	if ExtUIFS == nil {
+		return nil, "", fmt.Errorf("ui package was incorrectly compiled with embed_pomerium yet no FS was provided")
+	}
+	f, err = ExtUIFS.Open(name)
+	if err != nil {
+		return nil, "", fmt.Errorf("open %s: %w", name, err)
+	}
+
+	fi, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return nil, "", err
+	}
+
+	modTime := fi.ModTime()
+	if modTime.IsZero() {
+		modTime = startTime
+	}
+	etag = fmt.Sprintf("%x", modTime.UnixNano())
+
+	return f, etag, nil
+}

ui/embed_local.go

@@ -0,0 +1,40 @@
+//go:build !embed_pomerium
+
+package ui
+
+import (
+	"embed"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+var (
+	//go:embed dist/*
+	uiFS embed.FS
+)
+
+func openFile(name string) (f fs.File, etag string, err error) {
+	f, err = os.Open(filepath.Join("ui", name))
+	if os.IsNotExist(err) {
+		f, err = uiFS.Open(name)
+	}
+	if err != nil {
+		return nil, "", err
+	}
+
+	fi, err := f.Stat()
+	if err != nil {
+		_ = f.Close()
+		return nil, "", err
+	}
+
+	modTime := fi.ModTime()
+	if modTime.IsZero() {
+		modTime = startTime
+	}
+	etag = fmt.Sprintf("%x", modTime.UnixNano())
+
+	return f, etag, nil
+}