verify: starts of a checking function

tar/verify/example_xattr.go

@@ -0,0 +1,31 @@
+// +build ignore
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	verify "."
+)
+
+func main() {
+	for _, arg := range os.Args[1:] {
+		keys, err := verify.Listxattr(arg)
+		if err != nil {
+			fmt.Println(err)
+			continue
+		}
+		if len(keys) > 0 {
+			fmt.Printf("%s : %q\n", arg, keys)
+			for _, key := range keys {
+				buf, err := verify.Lgetxattr(arg, key)
+				if err != nil {
+					fmt.Printf("  ERROR: %s\n", err)
+					continue
+				}
+				fmt.Printf("  %s = %s\n", key, string(buf))
+			}
+		}
+	}
+}

tar/verify/headers.go

@@ -1,15 +1,20 @@
 package verify
 
-import "time"
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
 
 // PosixHeader is the structure from a POSIX tar header, to be marshalled from
 // the tar stream, and available for on-disk comparison and verification
 type PosixHeader struct {
 	Name     string      `json:"name,omitempty"`
-	Mode     uint32    `json:"mode,omitempty"`
+	Mode     os.FileMode `json:"mode,omitempty"`
 	UID      uint32      `json:"uid,omitempty"`
 	GID      uint32      `json:"gid,omitempty"`
-	Size     int       `json:"size,omitempty"`
+	Size     int64       `json:"size,omitempty"`
 	Mtime    time.Time   `json:"mtime,omitempty"`
 	Checksum []byte      `json:"chksum,omitempty"`
 	LinkName string      `json:"linkname,omitempty"`
@@ -21,3 +26,75 @@ type PosixHeader struct {
 	DevMinor int         `json:"devminor,omitempty"`
 	Prefix   string      `json:"prefix,omitempty"`
 }
+
+type PaxHeader struct {
+	Atime  time.Time
+	Ctime  time.Time
+	Xattrs map[string]string
+}
+
+type Header struct {
+	// maybe I do not want these grouped like this. Maybe this should be an interface instead.
+	Posix PosixHeader
+	Pax   PaxHeader
+}
+
+// Size returns file size (implements Sizer)
+func (hdr Header) Size() int64 {
+	return int64(hdr.Posix.Size)
+}
+
+// ModTime returns file mtime (implements ModTimer)
+func (hdr Header) ModTime() time.Time {
+	return hdr.Posix.Mtime
+}
+
+// Mode returns file mode (implements Moder)
+func (hdr Header) Mode() os.FileMode {
+	return hdr.Posix.Mode
+}
+
+func (hdr Header) LinkName() string {
+	return hdr.Posix.LinkName
+}
+
+// HeaderFromFile takes a relative root and the filename of the file to collect
+// information on.
+func HeaderFromFile(rel, filename string) (*Header, error) {
+	absRel, err := filepath.Abs(rel)
+	if err != nil {
+		return nil, err
+	}
+	if strings.HasPrefix(filename, "/") {
+		var err error
+		filename, err = filepath.Abs(filename)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	stat, err := os.Lstat(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	name := filename
+	if strings.HasPrefix(filename, absRel) {
+		name = strings.TrimPrefix(filename, absRel)
+	}
+
+	hdr := Header{
+		Posix: PosixHeader{
+			Name:  name,
+			Size:  stat.Size(),
+			Mode:  stat.Mode(),
+			Mtime: stat.ModTime(),
+		},
+	}
+	if stat.Mode()&os.ModeSymlink != 0 {
+		l, _ := os.Readlink(filename) // if this errors, the empty string is OK
+		hdr.Posix.LinkName = l
+	}
+
+	return &hdr, nil
+}

tar/verify/verify.go

@@ -1,6 +1,10 @@
 package verify
 
-import "fmt"
+import (
+	"fmt"
+	"os"
+	"time"
+)
 
 // CheckType is how the on disk attributes will be verified against the
 // recorded header information
@@ -15,14 +19,15 @@ const (
 	CheckFileUser
 	CheckFileGroup
 	CheckFileMtime
-	CheckFileDevice
+	CheckFileDevice // major/minor
-	CheckFileLink
+	CheckFileLink   // linkname
-	CheckFileCaps
+	CheckFileCaps   // which is just a subset of xattrs on linux
 )
 
 var (
 	// DefaultChecks is the default for verfication steps against each
-	// storage.VerficationEntry
+	// storage.VerficationEntry.
+	// These may need to vary from platform to platform
 	DefaultChecks = CheckDigest | CheckFileAttributes
 	// CheckFileAttributes are the group of file attribute checks done
 	CheckFileAttributes = CheckFileSize | CheckFileMode | CheckFileUser |
@@ -32,3 +37,26 @@ var (
 	// ErrNotSupportedPlatform is when the platform does not support given features
 	ErrNotSupportedPlatform = fmt.Errorf("platform does not support this feature")
 )
+
+// FileAttrer exposes the functions corresponding to file attribute checks
+type FileAttrer interface {
+	Sizer
+	Moder
+	ModTimer
+	LinkName() string
+}
+
+// Sizer returns the size of the file (see also os.FileInfo)
+type Sizer interface {
+	Size() int64
+}
+
+// Moder returns the mode of the file (see also os.FileInfo)
+type Moder interface {
+	Mode() os.FileMode
+}
+
+// ModTimer returns the mtime of the file (see also os.FileInfo)
+type ModTimer interface {
+	ModTime() time.Time
+}

tar/verify/xattrs_linux.go

@@ -13,29 +13,6 @@ import (
 	"unsafe"
 )
 
-/*
-func main() {
-	for _, arg := range os.Args[1:] {
-		keys, err := Listxattr(arg)
-		if err != nil {
-			fmt.Println(err)
-			continue
-		}
-		if len(keys) > 0 {
-			fmt.Printf("%s : %q\n", arg, keys)
-			for _, key := range keys {
-				buf, err := Lgetxattr(arg, key)
-				if err != nil {
-					fmt.Printf("  ERROR: %s\n", err)
-					continue
-				}
-				fmt.Printf("  %s = %s\n", key, string(buf))
-			}
-		}
-	}
-}
-*/
-
 // Listxattr is a helper around the syscall.Listxattr
 func Listxattr(path string) ([]string, error) {
 	buf := make([]byte, 1024)
@@ -48,7 +25,7 @@ func Listxattr(path string) ([]string, error) {
 		sz, err = syscall.Listxattr(path, buf)
 	}
 	keys := []string{}
-	for _, key := range bytes.Split(bytes.TrimSpace(buf), []byte{0x0}) {
+	for _, key := range bytes.Split(bytes.Trim(buf, "\x00"), []byte{0x0}) {
 		if string(key) != "" {
 			keys = append(keys, string(key))
 		}