108 lines
2.8 KiB
Go
108 lines
2.8 KiB
Go
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// Copyright 2015 clair authors
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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 utils
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import (
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"archive/tar"
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"bufio"
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"bytes"
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"compress/gzip"
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"errors"
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"io"
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"io/ioutil"
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"strings"
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)
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var (
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// ErrCouldNotExtract occurs when an extraction fails.
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ErrCouldNotExtract = errors.New("utils: could not extract the archive")
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// ErrExtractedFileTooBig occurs when a file to extract is too big.
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ErrExtractedFileTooBig = errors.New("utils: could not extract one or more files from the archive: file too big")
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gzipHeader = []byte{0x1f, 0x8b}
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)
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// SelectivelyExtractArchive extracts the specified files and folders
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// from targz data read from the given reader and store them in a map indexed by file paths
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func SelectivelyExtractArchive(r io.Reader, toExtract []string, maxFileSize int64) (map[string][]byte, error) {
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data := make(map[string][]byte)
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// Create a tar or tar/tar-gzip reader
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tr, err := getTarReader(r)
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if err != nil {
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return data, ErrCouldNotExtract
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}
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// For each element in the archive
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for {
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hdr, err := tr.Next()
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if err == io.EOF {
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break
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}
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if err != nil {
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return data, ErrCouldNotExtract
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}
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// Get element filename
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filename := hdr.Name
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filename = strings.TrimPrefix(filename, "./")
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// Determine if we should extract the element
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toBeExtracted := false
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for _, s := range toExtract {
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if strings.HasPrefix(filename, s) {
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toBeExtracted = true
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break
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}
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}
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if toBeExtracted {
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// File size limit
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if maxFileSize > 0 && hdr.Size > maxFileSize {
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return data, ErrExtractedFileTooBig
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}
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// Extract the element
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if hdr.Typeflag == tar.TypeSymlink || hdr.Typeflag == tar.TypeLink || hdr.Typeflag == tar.TypeReg {
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d, _ := ioutil.ReadAll(tr)
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data[filename] = d
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}
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}
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}
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return data, nil
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}
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// getTarReader returns a tar.Reader associated with the specified io.Reader,
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// optionally backed by a gzip.Reader if gzip compression is detected.
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//
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// Gzip detection is done by using the magic numbers defined in the RFC1952 :
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// the first two bytes should be 0x1f and 0x8b..
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func getTarReader(r io.Reader) (*tar.Reader, error) {
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br := bufio.NewReader(r)
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header, err := br.Peek(2)
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if err == nil && bytes.Equal(header, gzipHeader) {
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gr, err := gzip.NewReader(br)
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if err != nil {
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return nil, err
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}
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return tar.NewReader(gr), nil
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}
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return tar.NewReader(br), nil
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}
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