1 files changed, 111 insertions, 0 deletions
diff --git a/pkg/types/leaf.go b/pkg/types/leaf.go
new file mode 100644
index 0000000..1476ead
--- /dev/null
+++ b/pkg/types/leaf.go
@@ -0,0 +1,111 @@
+package types
+
+import (
+	"crypto"
+	"crypto/ed25519"
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"git.sigsum.org/sigsum-lib-go/pkg/ascii"
+)
+
+type Statement struct {
+	ShardHint uint64 `ascii:"shard_hint"`
+	Checksum  Hash   `ascii:"checksum"`
+}
+
+type Leaf struct {
+	Statement
+	Signature Signature `ascii:"signature"`
+	KeyHash   Hash      `ascii:"key_hash"`
+}
+
+type Leaves []Leaf
+
+func (s *Statement) ToBinary() []byte {
+	b := make([]byte, 40)
+	binary.BigEndian.PutUint64(b[0:8], s.ShardHint)
+	copy(b[8:40], s.Checksum[:])
+	return b
+}
+
+func (s *Statement) Sign(signer crypto.Signer) (*Signature, error) {
+	sig, err := signer.Sign(nil, s.ToBinary(), crypto.Hash(0))
+	if err != nil {
+		return nil, fmt.Errorf("types: failed signing statement")
+	}
+
+	var signature Signature
+	copy(signature[:], sig)
+	return &signature, nil
+}
+
+func (s *Statement) Verify(key *PublicKey, sig *Signature) bool {
+	return ed25519.Verify(ed25519.PublicKey(key[:]), s.ToBinary(), sig[:])
+}
+
+func (l *Leaf) ToBinary() []byte {
+	b := make([]byte, 136)
+	binary.BigEndian.PutUint64(b[0:8], l.ShardHint)
+	copy(b[8:40], l.Checksum[:])
+	copy(b[40:104], l.Signature[:])
+	copy(b[104:136], l.KeyHash[:])
+	return b
+}
+
+func (l *Leaf) FromBinary(b []byte) error {
+	if len(b) != 136 {
+		return fmt.Errorf("types: invalid leaf size: %d", len(b))
+	}
+
+	l.ShardHint = binary.BigEndian.Uint64(b[0:8])
+	copy(l.Checksum[:], b[8:40])
+	copy(l.Signature[:], b[40:104])
+	copy(l.KeyHash[:], b[104:136])
+	return nil
+}
+
+func (l *Leaf) ToASCII(w io.Writer) error {
+	return ascii.StdEncoding.Serialize(w, l)
+}
+
+func (l *Leaf) FromASCII(r io.Reader) error {
+	return ascii.StdEncoding.Deserialize(r, l)
+}
+
+func (l *Leaves) FromASCII(r io.Reader) error {
+	leaves := &struct {
+		ShardHint []uint64    `ascii:"shard_hint"`
+		Checksum  []Hash      `ascii:"checksum"`
+		Signature []Signature `ascii:"signature"`
+		KeyHash   []Hash      `ascii:"key_hash"`
+	}{}
+
+	if err := ascii.StdEncoding.Deserialize(r, leaves); err != nil {
+		return err
+	}
+	n := len(leaves.ShardHint)
+	if n != len(leaves.Checksum) {
+		return fmt.Errorf("types: mismatched leaf field counts")
+	}
+	if n != len(leaves.Signature) {
+		return fmt.Errorf("types: mismatched leaf field counts")
+	}
+	if n != len(leaves.KeyHash) {
+		return fmt.Errorf("types: mismatched leaf field counts")
+	}
+
+	*l = make([]Leaf, 0, n)
+	for i := 0; i < n; i++ {
+		*l = append(*l, Leaf{
+			Statement: Statement{
+				ShardHint: leaves.ShardHint[i],
+				Checksum:  leaves.Checksum[i],
+			},
+			Signature: leaves.Signature[i],
+			KeyHash:   leaves.KeyHash[i],
+		})
+	}
+	return nil
+}