mirror of
https://github.com/containers/skopeo.git
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113 lines
2.9 KiB
Go
113 lines
2.9 KiB
Go
// Copyright 2016 The Linux Foundation
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package image
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import (
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"encoding/json"
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"io"
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"io/ioutil"
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"net/http"
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"os"
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"github.com/opencontainers/image-spec/schema"
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"github.com/pkg/errors"
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)
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// supported autodetection types
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const (
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TypeImageLayout = "imageLayout"
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TypeImage = "image"
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TypeImageZip = "imageZip"
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TypeManifest = "manifest"
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TypeImageIndex = "imageIndex"
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TypeConfig = "config"
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)
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// Autodetect detects the validation type for the given path
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// or an error if the validation type could not be resolved.
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func Autodetect(path string) (string, error) {
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fi, err := os.Stat(path)
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if err != nil {
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return "", errors.Wrapf(err, "unable to access path") // err from os.Stat includes path name
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}
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if fi.IsDir() {
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return TypeImageLayout, nil
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}
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f, err := os.Open(path)
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if err != nil {
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return "", errors.Wrap(err, "unable to open file") // os.Open includes the filename
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}
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defer f.Close()
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buf, err := ioutil.ReadAll(io.LimitReader(f, 512)) // read some initial bytes to detect content
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if err != nil {
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return "", errors.Wrap(err, "unable to read")
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}
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mimeType := http.DetectContentType(buf)
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switch mimeType {
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case "application/x-gzip", "application/x-rar-compressed", "application/octet-stream":
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return TypeImage, nil
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case "application/zip":
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return TypeImageZip, nil
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case "text/plain; charset=utf-8":
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// might be a JSON file, will be handled below
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default:
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return "", errors.New("unknown file type")
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}
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if _, err := f.Seek(0, io.SeekStart); err != nil {
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return "", errors.Wrap(err, "unable to seek")
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}
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header := struct {
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SchemaVersion int `json:"schemaVersion"`
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MediaType string `json:"mediaType"`
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Config interface{} `json:"config"`
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}{}
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if err := json.NewDecoder(f).Decode(&header); err != nil {
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if _, errSeek := f.Seek(0, io.SeekStart); errSeek != nil {
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return "", errors.Wrap(err, "unable to seek")
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}
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e := errors.Wrap(
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schema.WrapSyntaxError(f, err),
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"unable to parse JSON",
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)
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return "", e
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}
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switch {
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case header.MediaType == string(schema.ValidatorMediaTypeManifest):
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return TypeManifest, nil
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case header.MediaType == string(schema.ValidatorMediaTypeImageIndex):
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return TypeImageIndex, nil
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case header.MediaType == "" && header.SchemaVersion == 0 && header.Config != nil:
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// config files don't have mediaType/schemaVersion header
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return TypeConfig, nil
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}
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return "", errors.New("unknown media type")
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}
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