123 lines
3.4 KiB
Go
123 lines
3.4 KiB
Go
// Copyright 2020 Google LLC All Rights Reserved.
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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 verify provides a ReadCloser that verifies content matches the
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// expected hash values.
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package verify
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import (
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"bytes"
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"encoding/hex"
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"errors"
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"fmt"
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"hash"
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"io"
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"github.com/google/go-containerregistry/internal/and"
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v1 "github.com/google/go-containerregistry/pkg/v1"
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)
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// SizeUnknown is a sentinel value to indicate that the expected size is not known.
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const SizeUnknown = -1
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type verifyReader struct {
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inner io.Reader
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hasher hash.Hash
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expected v1.Hash
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gotSize, wantSize int64
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}
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// Error provides information about the failed hash verification.
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type Error struct {
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got string
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want v1.Hash
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gotSize int64
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}
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func (v Error) Error() string {
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return fmt.Sprintf("error verifying %s checksum after reading %d bytes; got %q, want %q",
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v.want.Algorithm, v.gotSize, v.got, v.want)
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}
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// Read implements io.Reader
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func (vc *verifyReader) Read(b []byte) (int, error) {
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n, err := vc.inner.Read(b)
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vc.gotSize += int64(n)
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if err == io.EOF {
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if vc.wantSize != SizeUnknown && vc.gotSize != vc.wantSize {
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return n, fmt.Errorf("error verifying size; got %d, want %d", vc.gotSize, vc.wantSize)
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}
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got := hex.EncodeToString(vc.hasher.Sum(nil))
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if want := vc.expected.Hex; got != want {
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return n, Error{
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got: vc.expected.Algorithm + ":" + got,
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want: vc.expected,
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gotSize: vc.gotSize,
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}
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}
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}
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return n, err
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}
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// ReadCloser wraps the given io.ReadCloser to verify that its contents match
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// the provided v1.Hash before io.EOF is returned.
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//
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// The reader will only be read up to size bytes, to prevent resource
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// exhaustion. If EOF is returned before size bytes are read, an error is
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// returned.
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//
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// A size of SizeUnknown (-1) indicates disables size verification when the size
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// is unknown ahead of time.
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func ReadCloser(r io.ReadCloser, size int64, h v1.Hash) (io.ReadCloser, error) {
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w, err := v1.Hasher(h.Algorithm)
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if err != nil {
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return nil, err
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}
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r2 := io.TeeReader(r, w) // pass all writes to the hasher.
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if size != SizeUnknown {
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r2 = io.LimitReader(r2, size) // if we know the size, limit to that size.
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}
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return &and.ReadCloser{
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Reader: &verifyReader{
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inner: r2,
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hasher: w,
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expected: h,
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wantSize: size,
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},
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CloseFunc: r.Close,
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}, nil
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}
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// Descriptor verifies that the embedded Data field matches the Size and Digest
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// fields of the given v1.Descriptor, returning an error if the Data field is
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// missing or if it contains incorrect data.
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func Descriptor(d v1.Descriptor) error {
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if d.Data == nil {
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return errors.New("error verifying descriptor; Data == nil")
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}
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h, sz, err := v1.SHA256(bytes.NewReader(d.Data))
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if err != nil {
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return err
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}
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if h != d.Digest {
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return fmt.Errorf("error verifying Digest; got %q, want %q", h, d.Digest)
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}
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if sz != d.Size {
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return fmt.Errorf("error verifying Size; got %d, want %d", sz, d.Size)
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}
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return nil
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}
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