core/envoy: add command to download envoy binaries (#5133)

* core/envoy: add command to download envoy binaries

* use internal log

* remove original get-envoy script

pkg/envoy/get-envoy/main.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"time"
+
+	"golang.org/x/sync/errgroup"
+
+	"github.com/pomerium/pomerium/internal/log"
+)
+
+func main() {
+	ctx := context.Background()
+	err := run(ctx)
+	if err != nil {
+		log.Fatal().Err(err).Send()
+	}
+}
+
+func run(
+	ctx context.Context,
+) error {
+	envoyVersion := "1.30.2"
+	targets := []string{
+		"darwin-amd64",
+		"darwin-arm64",
+		"linux-amd64",
+		"linux-arm64",
+	}
+	baseURL := "https://github.com/pomerium/envoy-binaries/releases/download/v" + envoyVersion
+	eg, ctx := errgroup.WithContext(ctx)
+	for _, target := range targets {
+		target := target
+		eg.Go(func() error {
+			return download(ctx, "./envoy-"+target, baseURL+"/envoy-"+target)
+		})
+		eg.Go(func() error {
+			return download(ctx, "./envoy-"+target+".sha256", baseURL+"/envoy-"+target+".sha256")
+		})
+		eg.Go(func() error {
+			return os.WriteFile("./envoy-"+target+".version", []byte(envoyVersion+"\n"), 0o600)
+		})
+	}
+	return eg.Wait()
+}
+
+func download(
+	ctx context.Context,
+	dstPath string,
+	srcURL string,
+) error {
+	fi, err := os.Stat(dstPath)
+	if err == nil {
+		lastModified, err := getURLLastModified(ctx, srcURL)
+		if err != nil {
+			return fmt.Errorf("error getting download last modified (url=%s): %w", srcURL, err)
+		}
+
+		if timesMatch(fi.ModTime(), lastModified) {
+			log.Debug(ctx).Str("url", srcURL).Str("dst", dstPath).Msg("skipping download")
+			return nil
+		}
+
+	} else if !os.IsNotExist(err) {
+		return fmt.Errorf("error reading destination path file info (dst=%s): %w", dstPath, err)
+	}
+
+	log.Info(ctx).Str("url", srcURL).Str("dst", dstPath).Msg("downloading")
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, srcURL, nil)
+	if err != nil {
+		return fmt.Errorf("error creating GET request for download (url=%s): %w", srcURL, err)
+	}
+
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("error making GET request for download (url=%s): %w", srcURL, err)
+	}
+	defer res.Body.Close()
+
+	dst, err := os.Create(dstPath)
+	if err != nil {
+		return fmt.Errorf("error creating downloaded file (url=%s dst=%s): %w", srcURL, dstPath, err)
+	}
+
+	_, err = io.Copy(dst, res.Body)
+	if err != nil {
+		_ = dst.Close()
+		_ = os.Remove(dstPath)
+		return fmt.Errorf("error copying downloaded file (url=%s dst=%s): %w", srcURL, dstPath, err)
+	}
+
+	err = dst.Close()
+	if err != nil {
+		_ = os.Remove(dstPath)
+		return fmt.Errorf("error closing destination file: %w", err)
+	}
+
+	if lastModified, err := time.Parse(http.TimeFormat, res.Header.Get("Last-Modified")); err == nil {
+		err = os.Chtimes(dstPath, time.Time{}, lastModified)
+		if err != nil {
+			return fmt.Errorf("error writing last modified timestamp: %w", err)
+		}
+	}
+
+	return nil
+}
+
+func getURLLastModified(
+	ctx context.Context,
+	srcURL string,
+) (time.Time, error) {
+	// check to see if the file needs to be updated
+	headReq, err := http.NewRequestWithContext(ctx, http.MethodHead, srcURL, nil)
+	if err != nil {
+		return time.Time{}, fmt.Errorf("error creating head request for download: %w", err)
+	}
+
+	res, err := http.DefaultClient.Do(headReq)
+	if err != nil {
+		return time.Time{}, fmt.Errorf("error making head request for download: %w", err)
+	}
+	_ = res.Body.Close()
+
+	return time.Parse(http.TimeFormat, res.Header.Get("Last-Modified"))
+}
+
+func timesMatch(tm1, tm2 time.Time) bool {
+	diff := tm2.Sub(tm1)
+	return diff >= -5*time.Minute && diff <= 5*time.Minute
+}