offsetgen: support Docker username and password (open-telemetry#1239)

* offsetgen: support Docker username and password

* Pass environment variables to make docker-offsets

Makefile

@@ -126,7 +126,7 @@ offsets: | $(OFFSETGEN)
 
 .PHONY: docker-offsets
 docker-offsets:
-	docker run --rm -v /tmp:/tmp -v /var/run/docker.sock:/var/run/docker.sock -v $(shell pwd):/app golang:1.22 /bin/sh -c "cd ../app && make offsets"
+	docker run -e DOCKER_USERNAME=$(DOCKER_USERNAME) -e DOCKER_PASSWORD=$(DOCKER_PASSWORD) --rm -v /tmp:/tmp -v /var/run/docker.sock:/var/run/docker.sock -v $(shell pwd):/app golang:1.22 /bin/sh -c "cd ../app && make offsets"
 
 .PHONY: update-licenses
 update-licenses: generate $(GOLICENSES)

internal/tools/inspect/builder.go

@@ -6,15 +6,19 @@ package inspect
 import (
 	"bytes"
 	"context"
+	"encoding/base64"
+	"encoding/json"
 	"fmt"
 	"io"
 	"log/slog"
+	"os"
 	"path/filepath"
 
 	"github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/api/types/filters"
 	"github.com/docker/docker/api/types/image"
 	"github.com/docker/docker/api/types/mount"
+	"github.com/docker/docker/api/types/registry"
 	"github.com/docker/docker/client"
 	"github.com/docker/docker/pkg/stdcopy"
 	"github.com/hashicorp/go-version"
@@ -112,7 +116,23 @@ func (b *builder) pullImage(ctx context.Context) error {
 		return nil
 	}
 
-	rc, err := b.cli.ImagePull(ctx, b.GoImage, image.PullOptions{})
+	pullOpts := image.PullOptions{}
+	username := os.Getenv("DOCKER_USERNAME")
+	password := os.Getenv("DOCKER_PASSWORD")
+	if len(username) > 0 && len(password) > 0 {
+		authConfig := registry.AuthConfig{
+			Username: username,
+			Password: password,
+		}
+		encodedJSON, err := json.Marshal(authConfig)
+		if err != nil {
+			panic(err)
+		}
+		authStr := base64.URLEncoding.EncodeToString(encodedJSON)
+		pullOpts.RegistryAuth = authStr
+	}
+
+	rc, err := b.cli.ImagePull(ctx, b.GoImage, pullOpts)
 	if err != nil {
 		return err
 	}