S3: log human readable error on connection failure (#26856)

Should BucketExists (HeadBucket) fail because of an error related to
the connection rather than the existence of the bucket, no information
is available and the admin is left guessing.

https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadBucket.html

> This action is useful to determine if a bucket exists and you have
> permission to access it. The action returns a 200 OK if the bucket
> exists and you have permission to access it.
>
> If the bucket does not exist or you do not have permission to access
> it, the HEAD request returns a generic 400 Bad Request, 403
> Forbidden or 404 Not Found code. A message body is not included, so
> you cannot determine the exception beyond these error codes.

GetBucketVersioning is used instead and exclusively dedicated to
asserting if using the connection does not return a BadRequest.
If it does the NewMinioStorage logs an error and returns. Otherwise
it keeps going knowing that BucketExists is not going to fail for
reasons unrelated to the existence of the bucket and the permissions
to access it.

(cherry picked from commit d1df4b3bc62e5e61893a923f1c4b58f084eb03af)

Refs: https://codeberg.org/forgejo/forgejo/issues/1338

modules/storage/minio.go

@@ -71,6 +71,11 @@ func convertMinioErr(err error) error {
 	return err
 }
 
+var getBucketVersioning = func(ctx context.Context, minioClient *minio.Client, bucket string) error {
+	_, err := minioClient.GetBucketVersioning(ctx, bucket)
+	return err
+}
+
 // NewMinioStorage returns a minio storage
 func NewMinioStorage(ctx context.Context, cfg *setting.Storage) (ObjectStorage, error) {
 	config := cfg.MinioConfig
@@ -90,6 +95,23 @@ func NewMinioStorage(ctx context.Context, cfg *setting.Storage) (ObjectStorage,
 		return nil, convertMinioErr(err)
 	}
 
+	// The GetBucketVersioning is only used for checking whether the Object Storage parameters are generally good. It doesn't need to succeed.
+	// The assumption is that if the API returns the HTTP code 400, then the parameters could be incorrect.
+	// Otherwise even if the request itself fails (403, 404, etc), the code should still continue because the parameters seem "good" enough.
+	// Keep in mind that GetBucketVersioning requires "owner" to really succeed, so it can't be used to check the existence.
+	// Not using "BucketExists (HeadBucket)" because it doesn't include detailed failure reasons.
+	err = getBucketVersioning(ctx, minioClient, config.Bucket)
+	if err != nil {
+		errResp, ok := err.(minio.ErrorResponse)
+		if !ok {
+			return nil, err
+		}
+		if errResp.StatusCode == http.StatusBadRequest {
+			log.Error("S3 storage connection failure at %s:%s with base path %s and region: %s", config.Endpoint, config.Bucket, config.Location, errResp.Message)
+			return nil, err
+		}
+	}
+
 	// Check to see if we already own this bucket
 	exists, err := minioClient.BucketExists(ctx, config.Bucket)
 	if err != nil {

modules/storage/minio_test.go

@@ -4,10 +4,15 @@
 package storage
 
 import (
+	"context"
+	"net/http"
 	"os"
 	"testing"
 
 	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestMinioStorageIterator(t *testing.T) {
@@ -25,3 +30,31 @@ func TestMinioStorageIterator(t *testing.T) {
 		},
 	})
 }
+
+func TestS3StorageBadRequest(t *testing.T) {
+	if os.Getenv("CI") == "" {
+		t.Skip("S3Storage not present outside of CI")
+		return
+	}
+	cfg := &setting.Storage{
+		MinioConfig: setting.MinioStorageConfig{
+			Endpoint:        "minio:9000",
+			AccessKeyID:     "123456",
+			SecretAccessKey: "12345678",
+			Bucket:          "bucket",
+			Location:        "us-east-1",
+		},
+	}
+	message := "ERROR"
+	old := getBucketVersioning
+	defer func() { getBucketVersioning = old }()
+	getBucketVersioning = func(ctx context.Context, minioClient *minio.Client, bucket string) error {
+		return minio.ErrorResponse{
+			StatusCode: http.StatusBadRequest,
+			Code:       "FixtureError",
+			Message:    message,
+		}
+	}
+	_, err := NewStorage(setting.MinioStorageType, cfg)
+	assert.ErrorContains(t, err, message)
+}