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|
package objects
import (
"bytes"
"errors"
"fmt"
"io"
"strings"
"time"
)
const (
snapshot_start_marker = "== BEGIN SNAPSHOT =="
snapshot_end_marker = "== END SNAPSHOT =="
snapshot_start_line = snapshot_start_marker + "\n"
snapshot_end_line = snapshot_end_marker + "\n"
)
// Snapshot objects describe the state of a directory structure at a given time. It references a tree object by it's ID,
// records the snapshot time and associates it ton an archive (which is just a short freeform text grouping multiple snapshots together).
// A snapshot can optionally contain a comment and can be signed with a gpg key.
// If the snapshot is signed and you trust the signature, you can automatically trust the whole associated file tree,
// since all references are really cryptographic hashes, guaranteeing data integrity.
type Snapshot struct {
Tree ObjectId
Date time.Time
Archive string
Comment string
Signed bool
raw []byte
}
func (s Snapshot) Type() ObjectType {
return OTSnapshot
}
func appendKVPair(b []byte, k, v string) []byte {
b = append(b, []byte(k)...)
b = append(b, ' ')
b = append(b, []byte(v)...)
b = append(b, '\n')
return b
}
func (s Snapshot) Payload() (out []byte) {
out = append(out, []byte(snapshot_start_line)...)
out = appendKVPair(out, "archive", s.Archive)
out = appendKVPair(out, "date", s.Date.Format(time.RFC3339))
if s.Signed {
out = appendKVPair(out, "signed", "yes")
}
out = appendKVPair(out, "tree", s.Tree.String())
if s.Comment != "" {
// We must prevent that the comment includes an end marker
comment := strings.Replace(s.Comment, snapshot_end_marker, "~~ END SNAPSHOT ~~", -1)
if comment[len(comment)-1] != '\n' {
comment += "\n"
}
out = append(out, '\n')
out = append(out, []byte(comment)...)
}
out = append(out, []byte(snapshot_end_line)...)
return out
}
type Verifyer interface {
Verify([]byte) error
}
// Verify verifies that the snapshot has a valid signature.
// Only works with unserialized snapshots, i.e. a freshly created snapshot can not be verified.
func (s Snapshot) Verify(v Verifyer) error {
if !s.Signed {
return nil
}
return v.Verify(s.raw)
}
type Signer interface {
Sign([]byte) ([]byte, error)
}
func (s Snapshot) SignedPayload(signer Signer) ([]byte, error) {
return signer.Sign(s.Payload())
}
func (s *Snapshot) FromPayload(payload []byte) error {
r := bytes.NewBuffer(payload)
s.raw = payload
seenArchive := false
seenDate := false
seenTree := false
start := false
terminated := false
comment := false
for {
line, err := r.ReadString('\n')
if err != nil && err != io.EOF {
return err
} else if err == io.EOF {
break
}
line = strings.TrimSpace(line)
if !start {
if line == snapshot_start_marker {
start = true
}
continue
}
if line == snapshot_end_marker {
terminated = true
break
}
if comment {
s.Comment += line + "\n"
continue
}
if line == "" {
comment = true
continue
}
parts := strings.SplitN(line, " ", 2)
if len(parts) != 2 {
return fmt.Errorf("Invalid header: %s", line)
}
headerval := strings.TrimSpace(parts[1])
switch parts[0] {
case "archive":
s.Archive = headerval
seenArchive = true
case "date":
d, err := time.Parse(time.RFC3339, headerval)
if err != nil {
return err
}
s.Date = d
seenDate = true
case "signed":
s.Signed = headerval == "yes"
case "tree":
oid, err := ParseObjectId(headerval)
if err != nil {
return err
}
s.Tree = oid
seenTree = true
}
}
if !terminated {
return errors.New("The snapshot was not properly terminated")
}
if !seenArchive || !seenDate || !seenTree {
return errors.New("Missing archive, date or tree header")
}
s.Comment = strings.TrimSpace(s.Comment)
return nil
}
func (a Snapshot) Equals(b Snapshot) bool {
return a.Tree.Equals(b.Tree) &&
a.Archive == b.Archive &&
a.Date.Equal(b.Date) &&
a.Comment == b.Comment
}
|
