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package signify
import (
"bytes"
"encoding/base64"
"fmt"
"io"
"io/ioutil"
"git.sigsum.org/sigsum-lib-go/pkg/types"
)
type Parser struct{}
func (p *Parser) SignatureSuffix() string {
return ".sig"
}
func (p *Parser) PublicKey(r io.Reader) (*types.PublicKey, error) {
b, err := ioutil.ReadAll(r)
if err != nil {
return nil, fmt.Errorf("signify: read failed: %v", err)
}
var pub types.PublicKey
if err := parse(pub[:], b); err != nil {
return nil, fmt.Errorf("signify: %v", err)
}
return &pub, nil
}
func (p *Parser) Signature(r io.Reader) (*types.Signature, error) {
b, err := ioutil.ReadAll(r)
if err != nil {
return nil, fmt.Errorf("signify: read failed: %v", err)
}
var sig types.Signature
if err := parse(sig[:], b); err != nil {
return nil, fmt.Errorf("signify: %v", err)
}
return &sig, nil
}
func parse(dst, lines []byte) error {
commentLine, dataLine, err := parseLines(lines)
if err != nil {
return fmt.Errorf("invalid: %v", err)
}
if err := parseCommentLine(commentLine); err != nil {
return fmt.Errorf("invalid: %v", err)
}
if err := parseDataLine(dst, dataLine); err != nil {
return fmt.Errorf("invalid: %v", err)
}
return nil
}
func parseLines(lines []byte) ([]byte, []byte, error) {
split := bytes.Split(lines, []byte("\n"))
if len(split) != 3 {
return nil, nil, fmt.Errorf("number of lines")
}
return split[0], split[1], nil
}
func parseCommentLine(line []byte) error {
if !bytes.HasPrefix(line, []byte("untrusted comment: ")) {
return fmt.Errorf("no untrusted comment")
}
return nil
}
func parseDataLine(dst, line []byte) error {
data, err := base64.StdEncoding.DecodeString(string(line))
if err != nil {
return fmt.Errorf("base64 encoding")
}
if len(data) < 2 || !bytes.Equal(data[:2], []byte("Ed")) {
return fmt.Errorf("algorithm")
}
data = data[2:]
if len(data) < 8 {
return fmt.Errorf("random fingerprint")
}
data = data[8:]
if len(data) != len(dst) {
return fmt.Errorf("data length")
}
copy(dst[:], data)
return nil
}
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