mpi: Add an API for EC math.

* src/context.c, src/context.h: New.
* src/Makefile.am (libgcrypt_la_SOURCES): Add new files.
* src/gcrypt.h.in (struct gcry_context, gcry_ctx_t): New types.
(gcry_ctx_release): New prototype.
(gcry_mpi_ec_p_new, gcry_mpi_ec_get_affine, gcry_mpi_ec_dup)
(gcry_mpi_ec_add, gcry_mpi_ec_mul): New prototypes.
* mpi/ec.c: Include errno.h and context.h.
(_gcry_mpi_ec_init): Rename to ..
(ec_p_init): this, make static, remove allocation and add arg CTX.
(_gcry_mpi_ec_p_internal_new): New; to replace _gcry_mpi_ec_init.
Change all callers to use this func.
(_gcry_mpi_ec_free): Factor code out to ..
(ec_deinit): New func.
(gcry_mpi_ec_p_new): New.
* src/visibility.c: Include context.h and mpi.h.
(gcry_mpi_ec_p_new, gcry_mpi_ec_get_affine, gcry_mpi_ec_dup)
(gcry_mpi_ec_add, gcry_mpi_ec_mul)
(gcry_ctx_release): New wrapper functions.
* src/visibility.h: Mark new wrapper functions visible.
* src/libgcrypt.def, src/libgcrypt.vers: Add new symbols.
* tests/t-mpi-point.c (print_mpi, hex2mpi, cmp_mpihex): New.
(context_alloc): New.
(make_point, basic_ec_math): New.
--

This part finishes the basic API to do EC math.  It provides a wrapper
around all internal functions.  tests/t-mpi-point.c may be useful as
sample code.  Eventually we will add function to retrieve curve
parameters etc.

1 files changed, 118 insertions, 0 deletions

diff --git a/src/context.c b/src/context.c
new file mode 100644
index 00000000..ae991c52
--- /dev/null
+++ b/src/context.c
@@ -0,0 +1,118 @@
+/* context.c - Context management
+ * Copyright (C) 2013  g10 Code GmbH
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Libgcrypt is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * Libgcrypt is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+#include <unistd.h>
+
+#include "g10lib.h"
+#include "mpi.h"
+#include "context.h"
+
+#define CTX_MAGIC "cTx"
+#define CTX_MAGIC_LEN 3
+
+
+/* The definition of the generic context object.  The public typedef
+   gcry_ctx_t is used to access it.  */
+struct gcry_context
+{
+  char magic[CTX_MAGIC_LEN]; /* Magic value to cross check that this
+                                is really a context object. */
+  char type;     /* The type of the context (CONTEXT_TYPE_foo).  */
+
+  void (*deinit)(void*); /* Function used to free the private part. */
+  PROPERLY_ALIGNED_TYPE u;
+};
+
+
+/* Allocate a fresh generic context of contect TYPE and allocate
+   LENGTH extra bytes for private use of the type handler. DEINIT is a
+   fucntion used called to deinitialize the private part; it may be
+   NULL if de-initialization is not required.  Returns NULL and sets
+   ERRNO if memory allocation failed.  */
+gcry_ctx_t
+_gcry_ctx_alloc (int type, size_t length, void (*deinit)(void*))
+{
+  gcry_ctx_t ctx;
+
+  switch (type)
+    {
+    case CONTEXT_TYPE_EC:
+      break;
+    default:
+      log_bug ("bad context type %d given to _gcry_ctx_alloc\n", type);
+      break;
+    }
+
+  if (length < sizeof (PROPERLY_ALIGNED_TYPE))
+    length = sizeof (PROPERLY_ALIGNED_TYPE);
+
+  ctx = gcry_calloc (1, sizeof *ctx - sizeof (PROPERLY_ALIGNED_TYPE) + length);
+  if (!ctx)
+    return NULL;
+  memcpy (ctx->magic, CTX_MAGIC, CTX_MAGIC_LEN);
+  ctx->type = type;
+  ctx->deinit = deinit;
+
+  return ctx;
+}
+
+
+/* Return a pointer to the private part of the context CTX.  TYPE is
+   the requested context type.  Using an explicit type allows to cross
+   check the type and eventually allows to store several private
+   contexts in one context object.  The function does not return an
+   error but aborts if the provided CTX is not valid.  */
+void *
+_gcry_ctx_get_pointer (gcry_ctx_t ctx, int type)
+{
+  if (memcmp (ctx->magic, CTX_MAGIC, CTX_MAGIC_LEN))
+    log_fatal ("bad pointer %p passed to _gcry_ctx_get_pointer\n", ctx);
+  if (ctx->type != type)
+    log_fatal ("wrong context type %d request for context %p of type %d\n",
+               type, ctx, ctx->type);
+  return &ctx->u;
+}
+
+
+/* Release the generic context CTX.  */
+void
+gcry_ctx_release (gcry_ctx_t ctx)
+{
+  if (!ctx)
+    return;
+  if (memcmp (ctx->magic, CTX_MAGIC, CTX_MAGIC_LEN))
+    log_fatal ("bad pointer %p passed to gcry_ctx_relase\n", ctx);
+  switch (ctx->type)
+    {
+    case CONTEXT_TYPE_EC:
+      break;
+    default:
+      log_fatal ("bad context type %d detected in gcry_ctx_relase\n",
+                 ctx->type);
+      break;
+    }
+  if (ctx->deinit)
+    ctx->deinit (&ctx->u);
+  gcry_free (ctx);
+}