1 files changed, 150 insertions, 0 deletions
diff --git a/namespace/namespace.go b/namespace/namespace.go
new file mode 100644
index 0000000..a02de6d
--- /dev/null
+++ b/namespace/namespace.go
@@ -0,0 +1,150 @@
+// Package namespace provides namespace functionality.  A namespace refers to a
+// particular verification key and signing algorithm that can be serialized with
+// TLS 1.2 notation, see RFC 5246 (§4).  Only Ed25519 is supported at this time.
+//
+// For example, this is how a serialized Ed25519 namespace looks like:
+//
+// 0   2                      34 (byte index)
+// +---+----------------------+
+// | 1 +   Verification key   +
+// +---+----------------------+
+package namespace
+
+import (
+	"fmt"
+
+	"crypto/ed25519"
+
+	"github.com/google/certificate-transparency-go/tls"
+)
+
+// NamespaceFormat defines a particular namespace type that is versioend
+type NamespaceFormat tls.Enum
+
+const (
+	NamespaceFormatReserved  NamespaceFormat = 0
+	NamespaceFormatEd25519V1 NamespaceFormat = 1
+)
+
+// Namespace references a versioned namespace based on a given format specifier
+type Namespace struct {
+	Format             NamespaceFormat     `tls:"maxval:65535"`
+	NamespaceEd25519V1 *NamespaceEd25519V1 `tls:"selector:Format,val:1"`
+}
+
+// NamespaceEd25519V1 uses an Ed25519 verification key as namespace.  Encoding,
+// signing, and verification operations are defined by RFC 8032.
+type NamespaceEd25519V1 struct {
+	Namespace []byte `tls:"minlen:32,maxlen:32"`
+}
+
+// String returns a human-readable representation of a namespace.
+func (n Namespace) String() string {
+	switch n.Format {
+	case NamespaceFormatEd25519V1:
+		return fmt.Sprintf("%x", n.NamespaceEd25519V1.Namespace)
+	default:
+		return "reserved"
+	}
+}
+
+// NewNamespaceEd25519V1 returns an new Ed25519V1 namespace based on a
+// verification key.
+func NewNamespaceEd25519V1(vk []byte) (*Namespace, error) {
+	if len(vk) != 32 {
+		return nil, fmt.Errorf("invalid verification key: must be 32 bytes")
+	}
+	return &Namespace{
+		Format: NamespaceFormatEd25519V1,
+		NamespaceEd25519V1: &NamespaceEd25519V1{
+			Namespace: vk,
+		},
+	}, nil
+}
+
+// Verify checks that signature is valid over message for this namespace
+func (ns *Namespace) Verify(message, signature []byte) error {
+	switch ns.Format {
+	case NamespaceFormatEd25519V1:
+		if !ed25519.Verify(ed25519.PublicKey(ns.NamespaceEd25519V1.Namespace), message, signature) {
+			return fmt.Errorf("ed25519 signature verification failed")
+		}
+	default:
+		return fmt.Errorf("namespace not supported: %v", ns.Format)
+	}
+	return nil
+}
+
+func (ns *Namespace) Marshal() ([]byte, error) {
+	serialized, err := tls.Marshal(*ns)
+	if err != nil {
+		return nil, fmt.Errorf("marshaled failed for namespace(%v): %v", ns.Format, err)
+	}
+	return serialized, err
+}
+
+func (ns *Namespace) Unmarshal(serialized []byte) error {
+	extra, err := tls.Unmarshal(serialized, ns)
+	if err != nil {
+		return fmt.Errorf("unmarshal failed for namespace: %v", err)
+	} else if len(extra) > 0 {
+		return fmt.Errorf("unmarshal found extra data for namespace(%v): %v", ns.Format, err)
+	}
+	return nil
+}
+
+// NamespacePool is a pool of namespaces that contain complete verification keys
+type NamespacePool struct {
+	pool map[string]*Namespace
+	list []*Namespace
+	// If we need to update this structure without a restart => add mutex.
+}
+
+// NewNameSpacePool creates a new namespace pool from a list of namespaces.  An
+// error is returned if there are duplicate namespaces or namespaces without a
+// complete verification key.  The latter is determined by namespaceWithKey().
+func NewNamespacePool(namespaces []*Namespace) (*NamespacePool, error) {
+	np := &NamespacePool{
+		pool: make(map[string]*Namespace),
+		list: make([]*Namespace, 0),
+	}
+	for _, namespace := range namespaces {
+		if !namespaceWithKey(namespace.Format) {
+			return nil, fmt.Errorf("need verification key in namespace pool: %v", namespace.Format)
+		}
+		if _, ok := np.pool[namespace.String()]; ok {
+			return nil, fmt.Errorf("duplicate namespace: %v", namespace.String())
+		}
+		np.pool[namespace.String()] = namespace
+		np.list = append(np.list, namespace)
+	}
+	return np, nil
+}
+
+// Find checks if namespace is a member of the namespace pool.
+func (np *NamespacePool) Find(namespace *Namespace) (*Namespace, bool) {
+	if _, ok := np.pool[namespace.String()]; !ok {
+		return nil, false
+	}
+	// If the passed namespace is a key fingerprint the actual key needs to be
+	// attached before returning.  Not applicable for Ed25519.  Docdoc later.
+	return namespace, true
+}
+
+// List returns a copied list of namespaces that is used by this pool.
+func (np *NamespacePool) List() []*Namespace {
+	namespaces := make([]*Namespace, len(np.list))
+	copy(namespaces, np.list)
+	return namespaces
+}
+
+// namespaceWithKey returns true if a namespace format contains a complete
+// verification key.  I.e., some formats might have a key fingerprint instead.
+func namespaceWithKey(format NamespaceFormat) bool {
+	switch format {
+	case NamespaceFormatEd25519V1:
+		return true
+	default:
+		return false
+	}
+}