image.go

Documentation: github.com/google/go-containerregistry/pkg/v1/mutate

     1  // Copyright 2019 Google LLC All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package mutate
    16  
    17  import (
    18  	"bytes"
    19  	"encoding/json"
    20  	"errors"
    21  	"sync"
    22  
    23  	v1 "github.com/google/go-containerregistry/pkg/v1"
    24  	"github.com/google/go-containerregistry/pkg/v1/partial"
    25  	"github.com/google/go-containerregistry/pkg/v1/stream"
    26  	"github.com/google/go-containerregistry/pkg/v1/types"
    27  )
    28  
    29  type image struct {
    30  	base v1.Image
    31  	adds []Addendum
    32  
    33  	computed        bool
    34  	configFile      *v1.ConfigFile
    35  	manifest        *v1.Manifest
    36  	annotations     map[string]string
    37  	mediaType       *types.MediaType
    38  	configMediaType *types.MediaType
    39  	diffIDMap       map[v1.Hash]v1.Layer
    40  	digestMap       map[v1.Hash]v1.Layer
    41  	subject         *v1.Descriptor
    42  
    43  	sync.Mutex
    44  }
    45  
    46  var _ v1.Image = (*image)(nil)
    47  
    48  func (i *image) MediaType() (types.MediaType, error) {
    49  	if i.mediaType != nil {
    50  		return *i.mediaType, nil
    51  	}
    52  	return i.base.MediaType()
    53  }
    54  
    55  func (i *image) compute() error {
    56  	i.Lock()
    57  	defer i.Unlock()
    58  
    59  	// Don't re-compute if already computed.
    60  	if i.computed {
    61  		return nil
    62  	}
    63  	var configFile *v1.ConfigFile
    64  	if i.configFile != nil {
    65  		configFile = i.configFile
    66  	} else {
    67  		cf, err := i.base.ConfigFile()
    68  		if err != nil {
    69  			return err
    70  		}
    71  		configFile = cf.DeepCopy()
    72  	}
    73  	diffIDs := configFile.RootFS.DiffIDs
    74  	history := configFile.History
    75  
    76  	diffIDMap := make(map[v1.Hash]v1.Layer)
    77  	digestMap := make(map[v1.Hash]v1.Layer)
    78  
    79  	for _, add := range i.adds {
    80  		history = append(history, add.History)
    81  		if add.Layer != nil {
    82  			diffID, err := add.Layer.DiffID()
    83  			if err != nil {
    84  				return err
    85  			}
    86  			diffIDs = append(diffIDs, diffID)
    87  			diffIDMap[diffID] = add.Layer
    88  		}
    89  	}
    90  
    91  	m, err := i.base.Manifest()
    92  	if err != nil {
    93  		return err
    94  	}
    95  	manifest := m.DeepCopy()
    96  	manifestLayers := manifest.Layers
    97  	for _, add := range i.adds {
    98  		if add.Layer == nil {
    99  			// Empty layers include only history in manifest.
   100  			continue
   101  		}
   102  
   103  		desc, err := partial.Descriptor(add.Layer)
   104  		if err != nil {
   105  			return err
   106  		}
   107  
   108  		// Fields in the addendum override the original descriptor.
   109  		if len(add.Annotations) != 0 {
   110  			desc.Annotations = add.Annotations
   111  		}
   112  		if len(add.URLs) != 0 {
   113  			desc.URLs = add.URLs
   114  		}
   115  
   116  		if add.MediaType != "" {
   117  			desc.MediaType = add.MediaType
   118  		}
   119  
   120  		manifestLayers = append(manifestLayers, *desc)
   121  		digestMap[desc.Digest] = add.Layer
   122  	}
   123  
   124  	configFile.RootFS.DiffIDs = diffIDs
   125  	configFile.History = history
   126  
   127  	manifest.Layers = manifestLayers
   128  
   129  	rcfg, err := json.Marshal(configFile)
   130  	if err != nil {
   131  		return err
   132  	}
   133  	d, sz, err := v1.SHA256(bytes.NewBuffer(rcfg))
   134  	if err != nil {
   135  		return err
   136  	}
   137  	manifest.Config.Digest = d
   138  	manifest.Config.Size = sz
   139  
   140  	// If Data was set in the base image, we need to update it in the mutated image.
   141  	if m.Config.Data != nil {
   142  		manifest.Config.Data = rcfg
   143  	}
   144  
   145  	// If the user wants to mutate the media type of the config
   146  	if i.configMediaType != nil {
   147  		manifest.Config.MediaType = *i.configMediaType
   148  	}
   149  
   150  	if i.mediaType != nil {
   151  		manifest.MediaType = *i.mediaType
   152  	}
   153  
   154  	if i.annotations != nil {
   155  		if manifest.Annotations == nil {
   156  			manifest.Annotations = map[string]string{}
   157  		}
   158  
   159  		for k, v := range i.annotations {
   160  			manifest.Annotations[k] = v
   161  		}
   162  	}
   163  	manifest.Subject = i.subject
   164  
   165  	i.configFile = configFile
   166  	i.manifest = manifest
   167  	i.diffIDMap = diffIDMap
   168  	i.digestMap = digestMap
   169  	i.computed = true
   170  	return nil
   171  }
   172  
   173  // Layers returns the ordered collection of filesystem layers that comprise this image.
   174  // The order of the list is oldest/base layer first, and most-recent/top layer last.
   175  func (i *image) Layers() ([]v1.Layer, error) {
   176  	if err := i.compute(); errors.Is(err, stream.ErrNotComputed) {
   177  		// Image contains a streamable layer which has not yet been
   178  		// consumed. Just return the layers we have in case the caller
   179  		// is going to consume the layers.
   180  		layers, err := i.base.Layers()
   181  		if err != nil {
   182  			return nil, err
   183  		}
   184  		for _, add := range i.adds {
   185  			layers = append(layers, add.Layer)
   186  		}
   187  		return layers, nil
   188  	} else if err != nil {
   189  		return nil, err
   190  	}
   191  
   192  	diffIDs, err := partial.DiffIDs(i)
   193  	if err != nil {
   194  		return nil, err
   195  	}
   196  	ls := make([]v1.Layer, 0, len(diffIDs))
   197  	for _, h := range diffIDs {
   198  		l, err := i.LayerByDiffID(h)
   199  		if err != nil {
   200  			return nil, err
   201  		}
   202  		ls = append(ls, l)
   203  	}
   204  	return ls, nil
   205  }
   206  
   207  // ConfigName returns the hash of the image's config file.
   208  func (i *image) ConfigName() (v1.Hash, error) {
   209  	if err := i.compute(); err != nil {
   210  		return v1.Hash{}, err
   211  	}
   212  	return partial.ConfigName(i)
   213  }
   214  
   215  // ConfigFile returns this image's config file.
   216  func (i *image) ConfigFile() (*v1.ConfigFile, error) {
   217  	if err := i.compute(); err != nil {
   218  		return nil, err
   219  	}
   220  	return i.configFile.DeepCopy(), nil
   221  }
   222  
   223  // RawConfigFile returns the serialized bytes of ConfigFile()
   224  func (i *image) RawConfigFile() ([]byte, error) {
   225  	if err := i.compute(); err != nil {
   226  		return nil, err
   227  	}
   228  	return json.Marshal(i.configFile)
   229  }
   230  
   231  // Digest returns the sha256 of this image's manifest.
   232  func (i *image) Digest() (v1.Hash, error) {
   233  	if err := i.compute(); err != nil {
   234  		return v1.Hash{}, err
   235  	}
   236  	return partial.Digest(i)
   237  }
   238  
   239  // Size implements v1.Image.
   240  func (i *image) Size() (int64, error) {
   241  	if err := i.compute(); err != nil {
   242  		return -1, err
   243  	}
   244  	return partial.Size(i)
   245  }
   246  
   247  // Manifest returns this image's Manifest object.
   248  func (i *image) Manifest() (*v1.Manifest, error) {
   249  	if err := i.compute(); err != nil {
   250  		return nil, err
   251  	}
   252  	return i.manifest.DeepCopy(), nil
   253  }
   254  
   255  // RawManifest returns the serialized bytes of Manifest()
   256  func (i *image) RawManifest() ([]byte, error) {
   257  	if err := i.compute(); err != nil {
   258  		return nil, err
   259  	}
   260  	return json.Marshal(i.manifest)
   261  }
   262  
   263  // LayerByDigest returns a Layer for interacting with a particular layer of
   264  // the image, looking it up by "digest" (the compressed hash).
   265  func (i *image) LayerByDigest(h v1.Hash) (v1.Layer, error) {
   266  	if cn, err := i.ConfigName(); err != nil {
   267  		return nil, err
   268  	} else if h == cn {
   269  		return partial.ConfigLayer(i)
   270  	}
   271  	if layer, ok := i.digestMap[h]; ok {
   272  		return layer, nil
   273  	}
   274  	return i.base.LayerByDigest(h)
   275  }
   276  
   277  // LayerByDiffID is an analog to LayerByDigest, looking up by "diff id"
   278  // (the uncompressed hash).
   279  func (i *image) LayerByDiffID(h v1.Hash) (v1.Layer, error) {
   280  	if layer, ok := i.diffIDMap[h]; ok {
   281  		return layer, nil
   282  	}
   283  	return i.base.LayerByDiffID(h)
   284  }
   285  
   286  func validate(adds []Addendum) error {
   287  	for _, add := range adds {
   288  		if add.Layer == nil && !add.History.EmptyLayer {
   289  			return errors.New("unable to add a nil layer to the image")
   290  		}
   291  	}
   292  	return nil
   293  }
   294
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