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verify.go
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verify.go
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//
// Copyright (c) SAS Institute Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
package signjar
import (
"archive/zip"
"bytes"
"crypto"
"encoding/base64"
"fmt"
"hash"
"io"
"io/ioutil"
"net/http"
"path"
"strings"
"github.com/pkg/errors"
"github.com/sassoftware/relic/lib/pkcs7"
"github.com/sassoftware/relic/lib/pkcs9"
"github.com/sassoftware/relic/lib/x509tools"
"github.com/sassoftware/relic/signers/sigerrors"
)
var errNoDigests = errors.New("no recognized digests found")
type JarSignature struct {
pkcs9.TimestampedSignature
SignatureHeader http.Header
Hash crypto.Hash
}
func Verify(inz *zip.Reader, skipDigests bool) ([]*JarSignature, error) {
var manifest []byte
sigfiles := make(map[string][]byte)
sigblobs := make(map[string][]byte)
for _, f := range inz.File {
dir, name := path.Split(strings.ToUpper(f.Name))
if dir != "META-INF/" || name == "" {
continue
}
i := strings.LastIndex(name, ".")
if i < 0 {
continue
}
base, ext := name[:i], name[i:]
r2, err := f.Open()
if err != nil {
return nil, err
}
contents, err := ioutil.ReadAll(r2)
if err != nil {
return nil, err
}
if err := r2.Close(); err != nil {
return nil, err
}
if name == "MANIFEST.MF" {
manifest = contents
} else if ext == ".SF" {
sigfiles[base] = contents
} else if ext == ".RSA" || ext == ".DSA" || ext == ".EC" || strings.HasPrefix(name, "SIG-") {
sigblobs[base] = contents
}
}
if manifest == nil {
return nil, errors.New("JAR contains no META-INF/MANIFEST.MF")
} else if len(sigfiles) == 0 {
return nil, sigerrors.NotSignedError{Type: "JAR"}
}
sigs := make([]*JarSignature, 0, len(sigfiles))
for base, sigfile := range sigfiles {
pkcs := sigblobs[base]
if pkcs == nil {
return nil, fmt.Errorf("JAR contains sigfile META-INF/%s.SF with no matching signature", base)
}
psd, err := pkcs7.Unmarshal(pkcs)
if err != nil {
return nil, err
}
sig, err := psd.Content.Verify(sigfile, false)
if err != nil {
return nil, err
}
ts, err := pkcs9.VerifyOptionalTimestamp(sig)
if err != nil {
return nil, err
}
hdr, err := verifySigFile(sigfile, manifest)
if err != nil {
return nil, err
}
hash, _ := x509tools.PkixDigestToHash(ts.SignerInfo.DigestAlgorithm)
sigs = append(sigs, &JarSignature{
TimestampedSignature: ts,
Hash: hash,
SignatureHeader: hdr,
})
}
if !skipDigests {
if err := verifyManifest(inz, manifest); err != nil {
return nil, err
}
}
return sigs, nil
}
// Verify all digests in MANIFEST.MF
func verifyManifest(inz *zip.Reader, manifest []byte) error {
parsed, err := ParseManifest(manifest)
if err != nil {
return err
}
zipfiles := make(map[string]*zip.File, len(inz.File))
for _, fh := range inz.File {
zipfiles[fh.Name] = fh
}
for filename, keys := range parsed.Files {
if keys.Get("Magic") != "" {
continue
}
fh := zipfiles[filename]
if fh == nil {
return fmt.Errorf("file %s is in manifest but not JAR", filename)
}
r, err := fh.Open()
if err != nil {
return err
}
if err := hashFile(keys, r, ""); err != nil {
return errors.Wrapf(err, "file \"%s\" in MANIFEST.MF", filename)
}
if err := r.Close(); err != nil {
return err
}
}
return nil
}
type digester struct {
key, value string
hash hash.Hash
}
// Verify any hashes present in a single manifest section against the given content.
func hashFile(keys http.Header, content io.Reader, suffix string) error {
digesters := make([]digester, 0)
suffix = "-Digest" + suffix
for key, value := range keys {
if !strings.HasSuffix(key, suffix) {
continue
}
hashName := strings.ToUpper(key[:len(key)-len(suffix)])
hash := x509tools.HashByName(hashName)
if !hash.Available() {
return fmt.Errorf("unknown digest key in manifest: %s", hashName)
}
digesters = append(digesters, digester{key, value[0], hash.New()})
}
if len(digesters) == 0 {
return errNoDigests
}
buf := make([]byte, 32*1024)
for {
n, err := content.Read(buf)
if n > 0 {
for _, digester := range digesters {
digester.hash.Write(buf[:n])
}
}
if err == io.EOF {
break
} else if err != nil {
return err
}
}
for _, digester := range digesters {
calculated := base64.StdEncoding.EncodeToString(digester.hash.Sum(nil))
if calculated != digester.value {
return fmt.Errorf("%s mismatch: manifest %s != calculated %s", digester.key, digester.value, calculated)
}
}
return nil
}
func verifySigFile(sigfile, manifest []byte) (http.Header, error) {
sfParsed, err := ParseManifest(sigfile)
if err != nil {
return nil, err
}
if err := hashFile(sfParsed.Main, bytes.NewReader(manifest), "-Manifest"); err != nil {
if err != errNoDigests {
return nil, errors.Wrap(err, "manifest signature")
}
// fall through and verify all the section digests
} else {
// if the whole-file digest passed then skip the sections
return sfParsed.Main, nil
}
sections, err := splitManifest(manifest)
if err != nil {
return nil, err
}
sectionMap := make(map[string][]byte, len(sections)-1)
for i, section := range sections {
if i == 0 {
if err := hashFile(sfParsed.Main, bytes.NewReader(sections[0]), "-Manifest-Main-Attributes"); err != nil {
return nil, errors.Wrap(err, "manifest main attributes signature")
}
} else {
hdr, err := parseSection(section)
if err != nil {
return nil, err
}
name := hdr.Get("Name")
if name == "" {
return nil, errors.New("manifest has section with no \"Name\" attribute")
}
sectionMap[name] = section
}
}
for name, keys := range sfParsed.Files {
section := sectionMap[name]
if section == nil {
return nil, fmt.Errorf("manifest is missing signed section \"%s\"", name)
}
if err := hashFile(keys, bytes.NewReader(section), ""); err != nil {
return nil, errors.Wrapf(err, "manifest signature over section \"%s\"", name)
}
}
return sfParsed.Main, nil
}