[feature] S3 support (#674)

* feat: vendor minio client

* feat: introduce storage package with s3 support

* feat: serve s3 files directly

this saves a lot of bandwith as the files are fetched from the object
store directly

* fix: use explicit local storage in tests

* feat: integrate s3 storage with the main server

* fix: add s3 config to cli tests

* docs: explicitly set values in example config

also adds license header to the storage package

* fix: use better http status code on s3 redirect

HTTP 302 Found is the best fit, as it signifies that the resource
requested was found but not under its presumed URL

307/TemporaryRedirect would mean that this resource is usually located
here, not in this case

303/SeeOther indicates that the redirection does not link to the
requested resource but to another page

* refactor: use context in storage driver interface

1 files changed, 115 insertions, 0 deletions

diff --git a/vendor/github.com/minio/minio-go/v7/api-stat.go b/vendor/github.com/minio/minio-go/v7/api-stat.go
new file mode 100644
index 000000000..6deb5f5dc
--- /dev/null
+++ b/vendor/github.com/minio/minio-go/v7/api-stat.go
@@ -0,0 +1,115 @@
+/*
+ * MinIO Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2015-2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package minio
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+
+	"github.com/minio/minio-go/v7/pkg/s3utils"
+)
+
+// BucketExists verifies if bucket exists and you have permission to access it. Allows for a Context to
+// control cancellations and timeouts.
+func (c *Client) BucketExists(ctx context.Context, bucketName string) (bool, error) {
+	// Input validation.
+	if err := s3utils.CheckValidBucketName(bucketName); err != nil {
+		return false, err
+	}
+
+	// Execute HEAD on bucketName.
+	resp, err := c.executeMethod(ctx, http.MethodHead, requestMetadata{
+		bucketName:       bucketName,
+		contentSHA256Hex: emptySHA256Hex,
+	})
+	defer closeResponse(resp)
+	if err != nil {
+		if ToErrorResponse(err).Code == "NoSuchBucket" {
+			return false, nil
+		}
+		return false, err
+	}
+	if resp != nil {
+		resperr := httpRespToErrorResponse(resp, bucketName, "")
+		if ToErrorResponse(resperr).Code == "NoSuchBucket" {
+			return false, nil
+		}
+		if resp.StatusCode != http.StatusOK {
+			return false, httpRespToErrorResponse(resp, bucketName, "")
+		}
+	}
+	return true, nil
+}
+
+// StatObject verifies if object exists and you have permission to access.
+func (c *Client) StatObject(ctx context.Context, bucketName, objectName string, opts StatObjectOptions) (ObjectInfo, error) {
+	// Input validation.
+	if err := s3utils.CheckValidBucketName(bucketName); err != nil {
+		return ObjectInfo{}, err
+	}
+	if err := s3utils.CheckValidObjectName(objectName); err != nil {
+		return ObjectInfo{}, err
+	}
+	headers := opts.Header()
+	if opts.Internal.ReplicationDeleteMarker {
+		headers.Set(minIOBucketReplicationDeleteMarker, "true")
+	}
+
+	urlValues := make(url.Values)
+	if opts.VersionID != "" {
+		urlValues.Set("versionId", opts.VersionID)
+	}
+	// Execute HEAD on objectName.
+	resp, err := c.executeMethod(ctx, http.MethodHead, requestMetadata{
+		bucketName:       bucketName,
+		objectName:       objectName,
+		queryValues:      urlValues,
+		contentSHA256Hex: emptySHA256Hex,
+		customHeader:     headers,
+	})
+	defer closeResponse(resp)
+	if err != nil {
+		return ObjectInfo{}, err
+	}
+
+	if resp != nil {
+		deleteMarker := resp.Header.Get(amzDeleteMarker) == "true"
+		if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
+			if resp.StatusCode == http.StatusMethodNotAllowed && opts.VersionID != "" && deleteMarker {
+				errResp := ErrorResponse{
+					StatusCode: resp.StatusCode,
+					Code:       "MethodNotAllowed",
+					Message:    "The specified method is not allowed against this resource.",
+					BucketName: bucketName,
+					Key:        objectName,
+				}
+				return ObjectInfo{
+					VersionID:      resp.Header.Get(amzVersionID),
+					IsDeleteMarker: deleteMarker,
+				}, errResp
+			}
+			return ObjectInfo{
+				VersionID:      resp.Header.Get(amzVersionID),
+				IsDeleteMarker: deleteMarker,
+			}, httpRespToErrorResponse(resp, bucketName, objectName)
+		}
+	}
+
+	return ToObjectInfo(bucketName, objectName, resp.Header)
+}