main.go

package main

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"io/ioutil"
	"log"
	"os"
	"strings"

	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/ecr"
	"github.com/aws/aws-sdk-go-v2/service/sts"
)

type auth struct {
	Auth string `json:"auth"`
}
type docker struct {
	Auths map[string]auth `json:"auths"`
}

func main() {
	dockercfg := docker{
		Auths: make(map[string]auth),
	}
	// Docker Hub authentication
	hubUsername := os.Getenv("DOCKER_HUB_USERNAME")
	hubPassword := os.Getenv("DOCKER_HUB_PASSWORD")
	if hubUsername != "" && hubPassword != "" {
		b64auth := base64.URLEncoding.EncodeToString([]byte(hubUsername + ":" + hubPassword))
		dockercfg.Auths["https://index.docker.io/v1/"] = auth{Auth: b64auth}
	}
	// ECR authentication
	cfg, err := config.LoadDefaultConfig(context.Background())
	if err != nil {
		log.Fatalf("unable to load SDK config, %v", err)
	}
	ids := os.Getenv("AWS_ECR_REGISTRY_IDS")
	if ids == "" {
		stsSvc := sts.NewFromConfig(cfg)
		callerID, err := stsSvc.GetCallerIdentity(context.Background(), &sts.GetCallerIdentityInput{})
		if err != nil {
			log.Fatalf("unable to get identity, %v", err)
		}
		ids = *callerID.Account
	}
	svc := ecr.NewFromConfig(cfg)
	resp, err := svc.GetAuthorizationToken(context.Background(), &ecr.GetAuthorizationTokenInput{
		RegistryIds: strings.Split(ids, " "),
	})
	if err != nil {
		log.Fatalf("unable to authorization token, %v", err)
	}
	for _, repo := range resp.AuthorizationData {
		dockercfg.Auths[(*repo.ProxyEndpoint)[8:]] = auth{Auth: *repo.AuthorizationToken}
	}
	out, err := json.Marshal(dockercfg)
	if err != nil {
		log.Fatalf("unable marshal json, %v", err)
	}
	err = ioutil.WriteFile(os.Args[1], out, 0644)
	if err != nil {
		log.Fatalf("unable to write output, %v", err)
	}
}