signer.go

Documentation: github.com/sassoftware/relic/signers/msi

     1  //
     2  // Copyright (c) SAS Institute Inc.
     3  //
     4  // Licensed under the Apache License, Version 2.0 (the "License");
     5  // you may not use this file except in compliance with the License.
     6  // You may obtain a copy of the License at
     7  //
     8  //     http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  //
    16  
    17  package msi
    18  
    19  // Sign Microsoft Installer files
    20  
    21  import (
    22  	"io"
    23  	"io/ioutil"
    24  	"os"
    25  
    26  	"github.com/sassoftware/relic/lib/atomicfile"
    27  	"github.com/sassoftware/relic/lib/authenticode"
    28  	"github.com/sassoftware/relic/lib/certloader"
    29  	"github.com/sassoftware/relic/lib/comdoc"
    30  	"github.com/sassoftware/relic/lib/magic"
    31  	"github.com/sassoftware/relic/signers"
    32  )
    33  
    34  var MsiSigner = &signers.Signer{
    35  	Name:      "msi",
    36  	Aliases:   []string{"msi-tar"},
    37  	Magic:     magic.FileTypeMSI,
    38  	CertTypes: signers.CertTypeX509,
    39  	Transform: transform,
    40  	Sign:      sign,
    41  	Verify:    verify,
    42  }
    43  
    44  func init() {
    45  	MsiSigner.Flags().Bool("no-extended-sig", false, "(MSI) Don't emit a MsiDigitalSignatureEx digest")
    46  	signers.Register(MsiSigner)
    47  }
    48  
    49  type msiTransformer struct {
    50  	f     *os.File
    51  	cdf   *comdoc.ComDoc
    52  	exsig []byte
    53  }
    54  
    55  func transform(f *os.File, opts signers.SignOpts) (signers.Transformer, error) {
    56  	cdf, err := comdoc.ReadFile(f)
    57  	if err != nil {
    58  		return nil, err
    59  	}
    60  	var exsig []byte
    61  	noExtended := opts.Flags.GetBool("no-extended-sig")
    62  	if !noExtended {
    63  		exsig, err = authenticode.PrehashMSI(cdf, opts.Hash)
    64  		if err != nil {
    65  			return nil, err
    66  		}
    67  	}
    68  	return &msiTransformer{f, cdf, exsig}, nil
    69  }
    70  
    71  // transform the MSI to a tar stream for upload
    72  func (t *msiTransformer) GetReader() (io.Reader, error) {
    73  	r, w := io.Pipe()
    74  	go func() {
    75  		w.CloseWithError(authenticode.MsiToTar(t.cdf, w))
    76  	}()
    77  	return r, nil
    78  }
    79  
    80  // apply a signed PKCS#7 blob to an already-open MSI document
    81  func (t *msiTransformer) Apply(dest, mimeType string, result io.Reader) error {
    82  	t.cdf.Close()
    83  	blob, err := ioutil.ReadAll(result)
    84  	if err != nil {
    85  		return err
    86  	}
    87  	// copy src to dest if needed, otherwise open in-place
    88  	f, err := atomicfile.WriteInPlace(t.f, dest)
    89  	if err != nil {
    90  		return err
    91  	}
    92  	defer f.Close()
    93  	cdf, err := comdoc.WriteFile(f.GetFile())
    94  	if err != nil {
    95  		return err
    96  	}
    97  	if err := authenticode.InsertMSISignature(cdf, blob, t.exsig); err != nil {
    98  		return err
    99  	}
   100  	if err := cdf.Close(); err != nil {
   101  		return err
   102  	}
   103  	return f.Commit()
   104  }
   105  
   106  // sign a transformed tarball and return the PKCS#7 blob
   107  func sign(r io.Reader, cert *certloader.Certificate, opts signers.SignOpts) ([]byte, error) {
   108  	noExtended := opts.Flags.GetBool("no-extended-sig")
   109  	sum, err := authenticode.DigestMsiTar(r, opts.Hash, !noExtended)
   110  	if err != nil {
   111  		return nil, err
   112  	}
   113  	ts, err := authenticode.SignMSIImprint(opts.Context(), sum, opts.Hash, cert)
   114  	if err != nil {
   115  		return nil, err
   116  	}
   117  	return opts.SetPkcs7(ts)
   118  }
   119  
   120  func verify(f *os.File, opts signers.VerifyOpts) ([]*signers.Signature, error) {
   121  	sig, err := authenticode.VerifyMSI(f, opts.NoDigests)
   122  	if err != nil {
   123  		return nil, err
   124  	}
   125  	return []*signers.Signature{&signers.Signature{
   126  		Hash:          sig.HashFunc,
   127  		X509Signature: &sig.TimestampedSignature,
   128  	}}, nil
   129  }
   130
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