GoBroke/conf/funcs_permspec.go

package conf

import (
	`errors`
	`io/fs`
	`os`
	`os/user`
	`strconv`
)

// chmod applies the PermSpec.Mode to path.
func (p *PermSpec) chmod(path string, isNew bool) (err error) {

	if p.Mode == nil || (!isNew && p.explicitMode == false) {
		return
	}

	if err = os.Chmod(path, *p.Mode); err != nil {
		return
	}

	return
}

// chown applies the Permspec.User and PermSpec.Group to path.
func (p *PermSpec) chown(path string) (err error) {

	/*
		ORIGINALLY, I thought I'd have to fetch the original UID/GID from fs.FileInfo.Sys().
		Linux uses https://pkg.go.dev/syscall?GOOS=linux#Stat_t
		macOS uses a https://pkg.go.dev/syscall?GOOS=darwin#Stat_t
		Windows uses a https://pkg.go.dev/syscall?GOOS=windows#Win32FileAttributeData which is completely useless.
		(And AIX, Plan9, JS don't have a Stat_t.)
		But per os.Chown, a -1 means "do not change", which is what we want.
	*/

	if (p.realUid == -1) || (p.realGid == -1) {
		// This evaluates as a no-op.
		return
	}

	if err = os.Chown(path, p.realUid, p.realGid); err != nil {
		return
	}

	return
}

// setMissing populates missing information from a PermSpec. It should only be invoked by the parent Perms.SetMissing.
func (p *PermSpec) setMissing(isDir bool) (err error) {

	var tmpUser *user.User
	var tmpGroup *user.Group
	var unameUnknown user.UnknownUserError
	// var uidUnknown user.UnknownUserIdError
	var gnameUnknown user.UnknownGroupError
	// var gidUnknown user.UnknownGroupIdError

	if p.idsSet {
		return
	}

	// MODE
	if p.Mode == nil {
		p.Mode = new(fs.FileMode)
		if isDir {
			*p.Mode = fs.FileMode(0o0700)
		} else {
			*p.Mode = fs.FileMode(0o0600)
		}
	} else {
		p.explicitMode = true
	}

	// OWNER/GROUP
	// If nil, no change from current on-disk.
	switch p.User {
	case "":
		p.realUid = p.parent.curUid
	case "-1":
		p.realUid = -1
	default:
		// Lookup, try username first then uid.
		if tmpUser, err = user.Lookup(p.User); err != nil {
			if errors.As(err, &unameUnknown) {
				err = nil
				if tmpUser, err = user.LookupId(p.User); err != nil {
					return
				}
			} else {
				return
			}
		}
		if p.realUid, err = strconv.Atoi(tmpUser.Uid); err != nil {
			return
		}
	}
	switch p.Group {
	case "":
		p.realGid = p.parent.curGid
	case "-1":
		p.realGid = -1
	default:
		// Lookup, try groupname first then gid.
		if tmpGroup, err = user.LookupGroup(p.Group); err != nil {
			if errors.As(err, &gnameUnknown) {
				err = nil
				if tmpGroup, err = user.LookupGroupId(p.Group); err != nil {
					return
				}
			} else {
				return
			}
		}
		if p.realGid, err = strconv.Atoi(tmpGroup.Gid); err != nil {
			return
		}
	}

	p.idsSet = true

	return
}