gitee.com/mysnapcore/mysnapd@v0.1.0/image/helpers.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2014-2022 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package image
    21  
    22  // TODO: put these in appropriate package(s) once they are clarified a bit more
    23  
    24  import (
    25  	"fmt"
    26  	"os"
    27  	"path/filepath"
    28  
    29  	"gitee.com/mysnapcore/mysnapd/asserts"
    30  	"gitee.com/mysnapcore/mysnapd/asserts/snapasserts"
    31  	"gitee.com/mysnapcore/mysnapd/gadget"
    32  	"gitee.com/mysnapcore/mysnapd/release"
    33  	"gitee.com/mysnapcore/mysnapd/snap"
    34  )
    35  
    36  // FetchAndCheckSnapAssertions fetches and cross checks the snap assertions
    37  // matching the given snap file using the provided asserts.Fetcher and
    38  // assertion database.
    39  // The optional model assertion must be passed for full cross checks.
    40  func FetchAndCheckSnapAssertions(snapPath string, info *snap.Info, model *asserts.Model, f asserts.Fetcher, db asserts.RODatabase) (*asserts.SnapDeclaration, error) {
    41  	sha3_384, size, err := asserts.SnapFileSHA3_384(snapPath)
    42  	if err != nil {
    43  		return nil, err
    44  	}
    45  
    46  	expectedProv := info.Provenance()
    47  	// this assumes series "16"
    48  	if err := snapasserts.FetchSnapAssertions(f, sha3_384, expectedProv); err != nil {
    49  		return nil, fmt.Errorf("cannot fetch snap signatures/assertions: %v", err)
    50  	}
    51  
    52  	// cross checks
    53  	verifiedRev, err := snapasserts.CrossCheck(info.InstanceName(), sha3_384, expectedProv, size, &info.SideInfo, model, db)
    54  	if err != nil {
    55  		return nil, err
    56  	}
    57  	if err := snapasserts.CheckProvenanceWithVerifiedRevision(snapPath, verifiedRev); err != nil {
    58  		return nil, err
    59  	}
    60  
    61  	a, err := db.Find(asserts.SnapDeclarationType, map[string]string{
    62  		"series":  release.Series,
    63  		"snap-id": info.SnapID,
    64  	})
    65  	if err != nil {
    66  		return nil, fmt.Errorf("internal error: lost snap declaration for %q: %v", info.InstanceName(), err)
    67  	}
    68  	return a.(*asserts.SnapDeclaration), nil
    69  }
    70  
    71  // var so that it can be mocked for tests
    72  var writeResolvedContent = writeResolvedContentImpl
    73  
    74  // writeResolvedContent takes gadget.Info and the unpacked
    75  // gadget/kernel snaps and outputs the resolved content from the
    76  // {gadget,kernel}.yaml into a filesystem tree with the structure:
    77  // <prepareImageDir>/resolved-content/<volume-name>/part<structure-nr>/...
    78  //
    79  // E.g.
    80  // /tmp/prep-img/resolved-content/pi/part0/{config.txt,bootcode.bin,...}
    81  func writeResolvedContentImpl(prepareDir string, info *gadget.Info, gadgetUnpackDir, kernelUnpackDir string) error {
    82  	fullPrepareDir, err := filepath.Abs(prepareDir)
    83  	if err != nil {
    84  		return err
    85  	}
    86  	targetDir := filepath.Join(fullPrepareDir, "resolved-content")
    87  
    88  	opts := &gadget.LayoutOptions{
    89  		GadgetRootDir: gadgetUnpackDir,
    90  		KernelRootDir: kernelUnpackDir,
    91  	}
    92  	for volName, vol := range info.Volumes {
    93  		pvol, err := gadget.LayoutVolume(vol, gadget.DefaultConstraints, opts)
    94  		if err != nil {
    95  			return err
    96  		}
    97  		for i, ps := range pvol.LaidOutStructure {
    98  			if !ps.HasFilesystem() {
    99  				continue
   100  			}
   101  			mw, err := gadget.NewMountedFilesystemWriter(&ps, nil)
   102  			if err != nil {
   103  				return err
   104  			}
   105  			// ubuntu-image uses the "part{}" nomenclature
   106  			dst := filepath.Join(targetDir, volName, fmt.Sprintf("part%d", i))
   107  			// on UC20, ensure system-seed links back to the
   108  			// <PrepareDir>/system-seed
   109  			if ps.Role == gadget.SystemSeed {
   110  				uc20systemSeedDir := filepath.Join(fullPrepareDir, "system-seed")
   111  				if err := os.MkdirAll(filepath.Dir(dst), 0755); err != nil {
   112  					return err
   113  				}
   114  				if err := os.Symlink(uc20systemSeedDir, dst); err != nil {
   115  					return err
   116  				}
   117  			}
   118  			if err := mw.Write(dst, nil); err != nil {
   119  				return err
   120  			}
   121  		}
   122  	}
   123  
   124  	return nil
   125  }