From e18d36ebae30536c77c61cd5da123991e0ca1629 Mon Sep 17 00:00:00 2001
From: Rasmus Dahlberg <rasmus@rgdd.se>
Date: Sun, 31 Dec 2023 09:39:25 +0100
Subject: Add drafty prototype

---
 pkg/submission/submission.go | 104 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 pkg/submission/submission.go

(limited to 'pkg/submission/submission.go')

diff --git a/pkg/submission/submission.go b/pkg/submission/submission.go
new file mode 100644
index 0000000..d33a49d
--- /dev/null
+++ b/pkg/submission/submission.go
@@ -0,0 +1,104 @@
+// Package submission provides creation and opening of a node's legitimately
+// issued certificate chains.  A submission is composed of a name, a message
+// authentication code, and one or more certificate chains in PEM format.
+//
+// Note: this package makes no attempt to parse any certificate chain.  In other
+// words, each certificate chain is treated as an opaque list of bytes.
+package submission
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"strings"
+
+	"rgdd.se/silent-ct/pkg/policy"
+)
+
+const (
+	Separator = "silent-ct:separator\n"
+)
+
+type Submission []byte
+
+func New(node policy.Node, data [][]byte) (Submission, error) {
+	mac, err := node.HMAC(message(data))
+	if err != nil {
+		return nil, fmt.Errorf("hmac: %v", err)
+	}
+
+	buf := bytes.NewBuffer(nil)
+	buf.WriteString(fmt.Sprintf("%s %x\n", node.Name, mac[:]))
+	buf.Write(message(data))
+	return buf.Bytes(), nil
+}
+
+func (s *Submission) Peek() (name string, err error) {
+	name, _, _, err = s.split()
+	return
+}
+
+func (s *Submission) Open(node policy.Node) ([][]byte, error) {
+	name, gotMAC, msg, err := s.split()
+	if err != nil {
+		return nil, err
+	}
+	if name != node.Name {
+		return nil, fmt.Errorf("wrong node name %s", name)
+	}
+	wantMAC, err := node.HMAC(msg)
+	if err != nil {
+		return nil, fmt.Errorf("hmac: %v", err)
+	}
+	if !hmac.Equal(gotMAC[:], wantMAC[:]) {
+		return nil, fmt.Errorf("hmac: mismatch")
+	}
+
+	return bytes.Split(msg, []byte(Separator)), nil
+}
+
+func (s *Submission) split() (name string, mac [sha256.Size]byte, msg []byte, err error) {
+	i := bytes.IndexByte(*s, '\n')
+	if i == -1 {
+		return name, mac, msg, fmt.Errorf("no authorization line")
+	}
+	authLine := (*s)[:i]
+	msg = (*s)[i+1:]
+
+	split := strings.Split(string(authLine), " ")
+	if len(split) != 2 {
+		return name, mac, msg, fmt.Errorf("invalid authorization line")
+	}
+	b, err := hex.DecodeString(split[1])
+	if err != nil {
+		return name, mac, msg, fmt.Errorf("mac: %v", err)
+	}
+	if len(b) != len(mac) {
+		return name, mac, msg, fmt.Errorf("mac: length must be %d bytes", len(mac))
+	}
+
+	name = split[0]
+	copy(mac[:], b)
+	return
+}
+
+func message(data [][]byte) []byte {
+	if len(data) == 0 {
+		return []byte{}
+	}
+
+	buf := bytes.NewBuffer(data[0])
+	for i, d := range data[1:] {
+		prev := data[i]
+		if prev[len(prev)-1] != '\n' {
+			buf.Write([]byte("\n"))
+		}
+
+		buf.Write([]byte(Separator))
+		buf.Write(d)
+	}
+
+	return buf.Bytes()
+}
-- 
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