autocert: add support for storage in s3 (#3793)

* autocert: add support for storage in s3

* go mod tidy

* skip on mac

internal/autocert/storage.go

@@ -0,0 +1,79 @@
+package autocert
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/caddyserver/certmagic"
+)
+
+var (
+	errUnknownStorageProvider = errors.New("unknown storage provider")
+	s3virtualRE               = regexp.MustCompile(`^([-a-zA-Z0-9]+)\.s3\.([-a-zA-Z0-9]+)\.amazonaws\.com(/.*)?$`)
+	s3hostRE                  = regexp.MustCompile(`^([^/]+)/([^/]+)(/.*)?$`)
+)
+
+// GetCertMagicStorage gets the certmagic storage provider based on the destination.
+func GetCertMagicStorage(ctx context.Context, dst string) (certmagic.Storage, error) {
+	idx := strings.Index(dst, "://")
+	if idx == -1 {
+		return &certmagic.FileStorage{Path: dst}, nil
+	}
+
+	scheme := dst[:idx]
+	switch scheme {
+	case "s3":
+		bucket := ""
+		prefix := ""
+		var options []func(*config.LoadOptions) error
+
+		if match := s3virtualRE.FindStringSubmatch(dst[idx+3:]); len(match) == 4 {
+			// s3://{bucket}.s3.{region}.amazonaws.com/{prefix}
+			bucket = match[1]
+			prefix = match[3]
+			options = append(options, config.WithRegion(match[2]))
+		} else if match := s3hostRE.FindStringSubmatch(dst[idx+3:]); len(match) == 4 {
+			// s3://{host}/{bucket-name}/{prefix}
+			host := match[1]
+			bucket = match[2]
+			if strings.HasPrefix(match[3], "/") {
+				prefix = match[3][1:]
+			}
+			options = append(options,
+				config.WithRegion("us-east-1"),
+				config.WithEndpointResolver(aws.EndpointResolverFunc(func(service, region string) (aws.Endpoint, error) {
+					return aws.Endpoint{
+						PartitionID:       "aws",
+						URL:               "http://" + host,
+						SigningRegion:     "us-east-1",
+						HostnameImmutable: true,
+					}, nil
+				})))
+		}
+
+		if prefix != "" && !strings.HasSuffix(prefix, "/") {
+			prefix += "/"
+		}
+
+		cfg, err := config.LoadDefaultConfig(ctx, options...)
+		if err != nil {
+			return nil, fmt.Errorf("autocert: error creating aws config: %w", err)
+		}
+
+		client := s3.NewFromConfig(cfg)
+
+		return &s3Storage{
+			client: client,
+			bucket: bucket,
+			prefix: prefix,
+		}, nil
+	}
+
+	return nil, errUnknownStorageProvider
+}