github.com/coreos/rocket@v1.30.1-0.20200224141603-171c416fac02/rkt/image/asc.go (about)

     1  // Copyright 2015 The rkt Authors
     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 image
    16  
    17  import (
    18  	"errors"
    19  	"net/url"
    20  	"os"
    21  
    22  	"github.com/hashicorp/errwrap"
    23  	"github.com/rkt/rkt/store/imagestore"
    24  )
    25  
    26  // ascFetcher is an interface used by asc to get the desired signature
    27  // file.
    28  type ascFetcher interface {
    29  	// Get fetches the file from passed location.
    30  	Get(location string) (readSeekCloser, error)
    31  }
    32  
    33  // localAscFetcher is an implementation of ascFetcher getting
    34  // signature files from a local filesystem.
    35  type localAscFetcher struct{}
    36  
    37  func (*localAscFetcher) Get(location string) (readSeekCloser, error) {
    38  	return os.Open(location)
    39  }
    40  
    41  // remoteAscFetcher is an implementation of ascFetcher getting
    42  // signature files from remote locations.
    43  type remoteAscFetcher struct {
    44  	// F is a function that actually does the fetching
    45  	F func(*url.URL, *os.File) error
    46  	// S is a store - used for getting a temporary file
    47  	S *imagestore.Store
    48  }
    49  
    50  func (f *remoteAscFetcher) Get(location string) (readSeekCloser, error) {
    51  	var roc *removeOnClose // closed on error
    52  	var errClose error     // error signaling to close roc
    53  
    54  	roc, err := getTmpROC(f.S, location)
    55  	if err != nil {
    56  		return nil, err
    57  	}
    58  
    59  	defer func() {
    60  		if errClose != nil {
    61  			roc.Close()
    62  		}
    63  	}()
    64  
    65  	u, errClose := url.Parse(location)
    66  	if errClose != nil {
    67  		return nil, errwrap.Wrap(errors.New("invalid signature location"), errClose)
    68  	}
    69  
    70  	errClose = f.F(u, roc.File)
    71  	if errClose != nil {
    72  		return nil, errClose
    73  	}
    74  
    75  	return roc, nil
    76  }
    77  
    78  // asc is an abstraction for getting signature files.
    79  type asc struct {
    80  	// Location is a string passed to the Fetcher.
    81  	Location string
    82  	// Fetcher (if available) does the actual fetching of a
    83  	// signature key.
    84  	Fetcher ascFetcher
    85  }
    86  
    87  // Get fetches a signature file. It returns nil and no error if there
    88  // was no fetcher set.
    89  func (a *asc) Get() (readSeekCloser, error) {
    90  	if a.Fetcher != nil {
    91  		return a.Fetcher.Get(a.Location)
    92  	}
    93  	return NopReadSeekCloser(nil), nil
    94  }