forked from toolshed/abra
68 lines
2.4 KiB
Go
68 lines
2.4 KiB
Go
package tarheader
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import (
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"archive/tar"
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"os"
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)
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// assert that we implement [tar.FileInfoNames].
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var _ tar.FileInfoNames = (*nosysFileInfo)(nil)
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// nosysFileInfo hides the system-dependent info of the wrapped FileInfo to
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// prevent tar.FileInfoHeader from introspecting it and potentially calling into
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// glibc.
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//
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// It implements [tar.FileInfoNames] to further prevent [tar.FileInfoHeader]
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// from performing any lookups on go1.23 and up. see https://go.dev/issue/50102
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type nosysFileInfo struct {
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os.FileInfo
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}
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// Uname stubs out looking up username. It implements [tar.FileInfoNames]
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// to prevent [tar.FileInfoHeader] from loading libraries to perform
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// username lookups.
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func (fi nosysFileInfo) Uname() (string, error) {
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return "", nil
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}
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// Gname stubs out looking up group-name. It implements [tar.FileInfoNames]
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// to prevent [tar.FileInfoHeader] from loading libraries to perform
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// username lookups.
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func (fi nosysFileInfo) Gname() (string, error) {
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return "", nil
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}
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func (fi nosysFileInfo) Sys() interface{} {
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// A Sys value of type *tar.Header is safe as it is system-independent.
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// The tar.FileInfoHeader function copies the fields into the returned
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// header without performing any OS lookups.
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if sys, ok := fi.FileInfo.Sys().(*tar.Header); ok {
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return sys
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}
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return nil
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}
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// FileInfoHeaderNoLookups creates a partially-populated tar.Header from fi.
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//
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// Compared to the archive/tar.FileInfoHeader function, this function is safe to
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// call from a chrooted process as it does not populate fields which would
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// require operating system lookups. It behaves identically to
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// tar.FileInfoHeader when fi is a FileInfo value returned from
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// tar.Header.FileInfo().
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//
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// When fi is a FileInfo for a native file, such as returned from os.Stat() and
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// os.Lstat(), the returned Header value differs from one returned from
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// tar.FileInfoHeader in the following ways. The Uname and Gname fields are not
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// set as OS lookups would be required to populate them. The AccessTime and
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// ChangeTime fields are not currently set (not yet implemented) although that
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// is subject to change. Callers which require the AccessTime or ChangeTime
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// fields to be zeroed should explicitly zero them out in the returned Header
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// value to avoid any compatibility issues in the future.
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func FileInfoHeaderNoLookups(fi os.FileInfo, link string) (*tar.Header, error) {
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hdr, err := tar.FileInfoHeader(nosysFileInfo{fi}, link)
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if err != nil {
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return nil, err
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}
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return hdr, sysStat(fi, hdr)
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}
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