1 files changed, 91 insertions, 0 deletions
diff --git a/pkg/signatures/signify/signify.go b/pkg/signatures/signify/signify.go
new file mode 100644
index 0000000..6dbbf07
--- /dev/null
+++ b/pkg/signatures/signify/signify.go
@@ -0,0 +1,91 @@
+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
+}