1 files changed, 88 insertions, 0 deletions
diff --git a/src/common/crypto_curve25519.c b/src/common/crypto_curve25519.c
new file mode 100644
index 0000000000..1985e8af2d
--- /dev/null
+++ b/src/common/crypto_curve25519.c
@@ -0,0 +1,88 @@
+/* Copyright (c) 2012, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/* Wrapper code for a curve25519 implementation. */
+
+#define CRYPTO_CURVE25519_PRIVATE
+#include "orconfig.h"
+#include "crypto.h"
+#include "crypto_curve25519.h"
+#include "util.h"
+
+/* ==============================
+   Part 1: wrap a suitable curve25519 implementation as curve25519_impl
+   ============================== */
+
+#ifdef USE_CURVE25519_DONNA
+int curve25519_donna(uint8_t *mypublic,
+                     const uint8_t *secret, const uint8_t *basepoint);
+#endif
+#ifdef USE_CURVE25519_NACL
+#include <crypto_scalarmult_curve25519.h>
+#endif
+
+int
+curve25519_impl(uint8_t *output, const uint8_t *secret,
+                const uint8_t *basepoint)
+{
+#ifdef USE_CURVE25519_DONNA
+  return curve25519_donna(output, secret, basepoint);
+#elif defined(USE_CURVE25519_NACL)
+  return crypto_scalarmult_curve25519(output, secret, basepoint);
+#else
+#error "No implementation of curve25519 is available."
+#endif
+}
+
+/* ==============================
+   Part 2: Wrap curve25519_impl with some convenience types and functions.
+   ============================== */
+
+/**
+ * Return true iff a curve25519_public_key_t seems valid. (It's not necessary
+ * to see if the point is on the curve, since the twist is also secure, but we
+ * do need to make sure that it isn't the point at infinity.) */
+int
+curve25519_public_key_is_ok(const curve25519_public_key_t *key)
+{
+  static const uint8_t zero[] =
+    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
+    "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+
+  return tor_memneq(key->public_key, zero, CURVE25519_PUBKEY_LEN);
+}
+
+/** Generate a new keypair and return the secret key.  If <b>extra_strong</b>
+ * is true, this key is possibly going to get used more than once, so
+ * use a better-than-usual RNG. */
+void
+curve25519_secret_key_generate(curve25519_secret_key_t *key_out,
+                               int extra_strong)
+{
+  (void)extra_strong;
+
+  crypto_rand((char*)key_out->secret_key, 32);
+  key_out->secret_key[0] &= 248;
+  key_out->secret_key[31] &= 127;
+  key_out->secret_key[31] |= 64;
+}
+
+void
+curve25519_public_key_generate(curve25519_public_key_t *key_out,
+                               const curve25519_secret_key_t *seckey)
+{
+  static const uint8_t basepoint[32] = {9};
+
+  curve25519_impl(key_out->public_key, seckey->secret_key, basepoint);
+}
+
+/** Perform the curve25519 ECDH handshake with <b>skey</b> and <b>pkey</b>,
+ * writing CURVE25519_OUTPUT_LEN bytes of output into <b>output</b>. */
+void
+curve25519_handshake(uint8_t *output,
+                     const curve25519_secret_key_t *skey,
+                     const curve25519_public_key_t *pkey)
+{
+  curve25519_impl(output, skey->secret_key, pkey->public_key);
+}
+