From dafb2da44bb35c7057744ca820833cde6d43c534 Mon Sep 17 00:00:00 2001
Message-Id: <dafb2da44bb35c7057744ca820833cde6d43c534.1716318819.git.mdw@distorted.org.uk>
From: Mark Wooding <mdw@chiark.greenend.org.uk>
Date: Thu, 26 May 2016 09:26:09 +0100
Subject: [PATCH] pubkey.c, ...: Support Bernstein's `Ed25519' signature
 scheme.
Organization: Straylight/Edgeware

From: Mark Wooding <mdw@distorted.org.uk>

---
 catacomb-python.h    |  1 +
 catacomb.c           |  1 +
 catacomb/__init__.py | 16 +++++++++++++
 pubkey.c             | 57 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 75 insertions(+)

diff --git a/catacomb-python.h b/catacomb-python.h
index 679920f..41c5292 100644
--- a/catacomb-python.h
+++ b/catacomb-python.h
@@ -88,6 +88,7 @@
 #include <catacomb/bintab.h>
 #include <catacomb/dsa.h>
 #include <catacomb/x25519.h>
+#include <catacomb/ed25519.h>
 
 #include <catacomb/gf.h>
 #include <catacomb/gfreduce.h>
diff --git a/catacomb.c b/catacomb.c
index 1d6f7f6..d64a16e 100644
--- a/catacomb.c
+++ b/catacomb.c
@@ -46,6 +46,7 @@ static const struct nameval consts[] = {
   C(KF_BURN), C(KF_OPT),
   C(EC_XONLY), C(EC_YBIT), C(EC_LSB), C(EC_CMPR), C(EC_EXPLY), C(EC_SORT),
   C(X25519_KEYSZ), C(X25519_PUBSZ), C(X25519_OUTSZ),
+  C(ED25519_KEYSZ), C(ED25519_PUBSZ), C(ED25519_SIGSZ),
 #define ENTRY(tag, val, str) C(KERR_##tag),
   KEY_ERRORS(ENTRY)
 #undef ENTRY
diff --git a/catacomb/__init__.py b/catacomb/__init__.py
index 115e8fe..9522528 100644
--- a/catacomb/__init__.py
+++ b/catacomb/__init__.py
@@ -495,6 +495,22 @@ class X25519Priv (_BoxyPriv, X25519Pub):
   def _op(me, k, X): return x25519(k, X)
   def _hashkey(me, z): return hsalsa20_prf(z, Z128)
 
+class Ed25519Pub (object):
+  def __init__(me, pub):
+    me.pub = pub
+  def verify(me, msg, sig):
+    return ed25519_verify(me.pub, msg, sig)
+
+class Ed25519Priv (Ed25519Pub):
+  def __init__(me, priv):
+    me.priv = priv
+    Ed25519Pub.__init__(me, ed25519_pubkey(priv))
+  def sign(me, msg):
+    return ed25519_sign(me.priv, msg, pub = me.pub)
+  @classmethod
+  def generate(cls, rng = rand):
+    return cls(rng.block(ED25519_KEYSZ))
+
 ###--------------------------------------------------------------------------
 ### Built-in named curves and prime groups.
 
diff --git a/pubkey.c b/pubkey.c
index 50fa78c..391db31 100644
--- a/pubkey.c
+++ b/pubkey.c
@@ -1136,6 +1136,57 @@ end:
   return (0);
 }
 
+/*----- Ed25519 -----------------------------------------------------------*/
+
+static PyObject *meth_ed25519_pubkey(PyObject *me, PyObject *arg)
+{
+  const char *k;
+  Py_ssize_t ksz;
+  PyObject *rc = 0;
+  if (!PyArg_ParseTuple(arg, "s#:ed25519_pubkey", &k, &ksz)) goto end;
+  rc = bytestring_pywrap(0, ED25519_PUBSZ);
+  ed25519_pubkey((octet *)PyString_AS_STRING(rc), k, ksz);
+  return (rc);
+end:
+  return (0);
+}
+
+static PyObject *meth_ed25519_sign(PyObject *me, PyObject *arg, PyObject *kw)
+{
+  const char *k, *p = 0, *m;
+  Py_ssize_t ksz, psz, msz;
+  PyObject *rc = 0;
+  octet pp[ED25519_PUBSZ];
+  char *kwlist[] = { "key", "msg", "pub", 0 };
+  if (!PyArg_ParseTupleAndKeywords(arg, kw, "s#s#|s#:ed25519_sign", kwlist,
+				   &k, &ksz, &m, &msz, &p, &psz))
+    goto end;
+  if (p && psz != ED25519_PUBSZ) VALERR("bad public length");
+  if (!p) { p = (const char *)pp; ed25519_pubkey(pp, k, ksz); }
+  rc = bytestring_pywrap(0, ED25519_SIGSZ);
+  ed25519_sign((octet *)PyString_AS_STRING(rc), k, ksz,
+	       (const octet *)p, m, msz);
+  return (rc);
+end:
+  return (0);
+}
+
+static PyObject *meth_ed25519_verify(PyObject *me, PyObject *arg)
+{
+  const char *p, *m, *s;
+  Py_ssize_t psz, msz, ssz;
+  PyObject *rc = 0;
+  if (!PyArg_ParseTuple(arg, "s#s#s#:ed25519_verify",
+			&p, &psz, &m, &msz, &s, &ssz))
+    goto end;
+  if (psz != ED25519_PUBSZ) VALERR("bad public length");
+  if (ssz != ED25519_SIGSZ) VALERR("bad signature length");
+  rc = getbool(!ed25519_verify((const octet *)p, m, msz, (const octet *)s));
+  return (rc);
+end:
+  return (0);
+}
+
 /*----- Global stuff ------------------------------------------------------*/
 
 static PyMethodDef methods[] = {
@@ -1152,6 +1203,12 @@ static PyMethodDef methods[] = {
 generate(NBITS, [event = pgen_nullev, rng = rand, nsteps = 0]) -> R")
   METH  (x25519,			"\
 x25519(KEY, PUBLIC) -> SHARED")
+  METH  (ed25519_pubkey,		"\
+ed25519_pubkey(KEY) -> PUBLIC")
+  KWMETH(ed25519_sign,			"\
+ed25519_sign(KEY, MSG, [PUBLIC]) -> SIG")
+  METH  (ed25519_verify,		"\
+ed25519_verify(PUBLIC, MSG, SIG) -> BOOL")
 #undef METHNAME
   { 0 }
 };
-- 
[mdw]