// Returns true if the MD5 and SHA256 checksums set on this file match the
// checksums of the file's contents. If a checksum is not provided, then it
// is not checked. If neither checksum is provided, then returns true.
func (f *file) Verify() bool {
r := f.Open()
defer r.Close()
ok, _ := util.VerifyStreamHash(r, f.MD5, f.SHA256)
return ok
}
// Verify computes the checksum of each file in this bag, and checks it against
// the manifest files. Both payload ("data/") and tag files are checked.
// The file list is read from manifest files for MD5, SHA1, SHA256, and SHA512
// hashes, although only MD5 and SHA256 hashes are actually computed and verified.
// Files missing an entry in a manifest file, or manifest entires missing a
// corresponding file will cause a verification error. Tag files which are
// missing a manifest entry are the only execption to the verification error.
func (r *Reader) Verify() error {
err := r.loadManifests()
if err != nil {
return err
}
// Check the quick stuff first, and do the time consuming checksum
// verification last.
var dataprefix = r.t.dirname + "data/"
var npayload int
// Does every payload ("data/") file in this zip appear in our manifest
// map? tag files may also appear in the map, we don't care yet.
//
// We need to do some pathname manipulation since the zip directory
// names have the form "bagname/data/blah/blah" but the manifest
// has names of the form "data/blah/blah".
for _, f := range r.z.File {
if !strings.HasPrefix(f.Name, dataprefix) {
continue
}
npayload++
xname := strings.TrimPrefix(f.Name, r.t.dirname)
if r.t.manifest[xname] == nil {
return BagError{Err: ErrExtraFile, File: xname}
}
}
// Does every file listed in the manifest exist in the zip file?
//
// The loop above ensures npayload <= nmanifest.
// so if nmanifest != npayload, it must be because it contains files
// not present in the zip file. The downside of this method is we do
// not know the name of the missing file.
var nmanifest int
for k := range r.t.manifest {
if strings.HasPrefix(k, "data/") {
nmanifest++
}
}
if npayload != nmanifest {
return BagError{Err: ErrMissingFile}
}
// Do all the checksums match?
// Since t.manifest includes both payload and data files, we will
// verify more than nmanifest files here.
for _, f := range r.z.File {
xname := strings.TrimPrefix(f.Name, r.t.dirname)
checksum := r.t.manifest[xname]
if checksum == nil {
// this file is not in the manifest. We don't care
// since we have already verified all the payload
// files are accounted for.
continue
}
in, err := f.Open()
if err != nil {
return err
}
ok, err := util.VerifyStreamHash(in, checksum.MD5, checksum.SHA256)
_ = in.Close()
if err != nil {
return err
} else if !ok {
// checksum error!
return BagError{Err: ErrChecksum, File: xname}
}
}
return nil
}