Added support code for RSA and EC key encoding (including reconstruction of all publi...

[BearSSL] / src / ec / ec_keygen.c

diff --git a/src/ec/ec_keygen.c b/src/ec/ec_keygen.c
new file mode 100644 (file)
index 0000000..02a3096
--- /dev/null
+++ b/src/ec/ec_keygen.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/* see bearssl_ec.h */
+size_t
+br_ec_keygen(const br_prng_class **rng_ctx,
+       const br_ec_impl *impl, br_ec_private_key *sk,
+       void *kbuf, int curve)
+{
+       const unsigned char *order;
+       unsigned char *buf;
+       size_t len;
+       unsigned mask;
+
+       if (curve < 0 || curve >= 32
+               || ((impl->supported_curves >> curve) & 1) == 0)
+       {
+               return 0;
+       }
+       order = impl->order(curve, &len);
+       while (len > 0 && *order == 0) {
+               order ++;
+               len --;
+       }
+       if (kbuf == NULL || len == 0) {
+               return len;
+       }
+       mask = order[0];
+       mask |= (mask >> 1);
+       mask |= (mask >> 2);
+       mask |= (mask >> 4);
+
+       /*
+        * We generate sequences of random bits of the right size, until
+        * the value is strictly lower than the curve order (we also
+        * check for all-zero values, which are invalid).
+        */
+       buf = kbuf;
+       for (;;) {
+               size_t u;
+               unsigned cc, zz;
+
+               (*rng_ctx)->generate(rng_ctx, buf, len);
+               buf[0] &= mask;
+               cc = 0;
+               u = len;
+               zz = 0;
+               while (u -- > 0) {
+                       cc = ((unsigned)(buf[u] - order[u] - cc) >> 8) & 1;
+                       zz |= buf[u];
+               }
+               if (cc != 0 && zz != 0) {
+                       break;
+               }
+       }
+
+       if (sk != NULL) {
+               sk->curve = curve;
+               sk->x = buf;
+               sk->xlen = len;
+       }
+       return len;
+}