Add a wrapper around, and test and build support for, curve25519.

We want to use donna-c64 when we have a GCC with support for
64x64->uint128_t multiplying.  If not, we want to use libnacl if we
can, unless it's giving us the unsafe "ref" implementation.  And if
that isn't going to work, we'd like to use the
portable-and-safe-but-slow 32-bit "donna" implementation.

We might need more library searching for the correct libnacl,
especially once the next libnacl release is out -- it's likely to have
bunches of better curve25519 implementations.

I also define a set of curve25519 wrapper functions, though it really
shouldn't be necessary.

We should eventually make the -donna*.c files get build with
-fomit-frame-pointer, since that can make a difference.

1 files changed, 43 insertions, 0 deletions

diff --git a/src/common/crypto_curve25519.h b/src/common/crypto_curve25519.h
new file mode 100644
index 0000000000..3e093be7bf
--- /dev/null
+++ b/src/common/crypto_curve25519.h
@@ -0,0 +1,43 @@
+/* Copyright (c) 2012, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_CRYPTO_CURVE25519_H
+#define TOR_CRYPTO_CURVE25519_H
+
+#include "torint.h"
+
+/** Length of a curve25519 public key when encoded. */
+#define CURVE25519_PUBKEY_LEN 32
+/** Length of a curve25519 secret key when encoded. */
+#define CURVE25519_SECKEY_LEN 32
+/** Length of the result of a curve25519 handshake. */
+#define CURVE25519_OUTPUT_LEN 32
+
+/** Wrapper type for a curve25519 public key */
+typedef struct curve25519_public_key_t {
+  uint8_t public_key[CURVE25519_PUBKEY_LEN];
+} curve25519_public_key_t;
+
+/** Wrapper type for a curve25519 secret key */
+typedef struct curve25519_secret_key_t {
+  uint8_t secret_key[CURVE25519_SECKEY_LEN];
+} curve25519_secret_key_t;
+
+int curve25519_public_key_is_ok(const curve25519_public_key_t *);
+
+void curve25519_secret_key_generate(curve25519_secret_key_t *key_out,
+                                    int extra_strong);
+void curve25519_public_key_generate(curve25519_public_key_t *key_out,
+                                    const curve25519_secret_key_t *seckey);
+
+void curve25519_handshake(uint8_t *output,
+                          const curve25519_secret_key_t *,
+                          const curve25519_public_key_t *);
+
+#ifdef CRYPTO_CURVE25519_PRIVATE
+int curve25519_impl(uint8_t *output, const uint8_t *secret,
+                    const uint8_t *basepoint);
+#endif
+
+#endif
+