From d879c287ac1da7990c97b911018d63410c60433c Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Tue, 25 Jan 2011 20:28:25 +0100
Subject: Started with some code cleanups in ECDH.

The goal is to have the ECDH code more uniform with the other
algorithms.  Also make error messages and variable names more similar
to other places.
---
 g10/pkglue.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 57 insertions(+), 13 deletions(-)

(limited to 'g10/pkglue.c')

diff --git a/g10/pkglue.c b/g10/pkglue.c
index f5c85976f..3aba4e4c1 100644
--- a/g10/pkglue.c
+++ b/g10/pkglue.c
@@ -28,6 +28,7 @@
 #include "util.h"
 #include "pkglue.h"
 #include "main.h"
+#include "options.h"
 
 /* FIXME: Better chnage the fucntion name because mpi_ is used by
    gcrypt macros.  */
@@ -156,26 +157,39 @@ pk_encrypt (int algo, gcry_mpi_t *resarr, gcry_mpi_t data,
       rc = gcry_sexp_build (&s_pkey, NULL,
 			    "(public-key(elg(p%m)(g%m)(y%m)))",
 			    pkey[0], pkey[1], pkey[2]);
+      /* Put DATA into a simplified S-expression.  */
+      if (rc || gcry_sexp_build (&s_data, NULL, "%m", data))
+        BUG ();
+
     }
   else if (algo == GCRY_PK_RSA || algo == GCRY_PK_RSA_E)
     {
       rc = gcry_sexp_build (&s_pkey, NULL,
 			    "(public-key(rsa(n%m)(e%m)))",
 			    pkey[0], pkey[1]);
+      /* Put DATA into a simplified S-expression.  */
+      if (rc || gcry_sexp_build (&s_data, NULL, "%m", data))
+        BUG ();
     }
   else if (algo == PUBKEY_ALGO_ECDH)	
     {
-      return pk_ecdh_encrypt (resarr, pk_fp, data, pkey);
+      gcry_mpi_t k;
+
+      rc = pk_ecdh_generate_ephemeral_key (pkey, &k);
+      if (rc)
+        return rc;
+      
+      /* Now use the ephemeral secret to compute the shared point.  */
+      rc = gcry_sexp_build (&s_pkey, NULL,
+                            "(public-key(ecdh(c%m)(q%m)(p%m)))",
+                            pkey[0], pkey[1], pkey[2]);
+      /* Put K into a simplified S-expression.  */
+      if (rc || gcry_sexp_build (&s_data, NULL, "%m", k))
+        BUG ();
     }
   else
-    return GPG_ERR_PUBKEY_ALGO;
-
-  if (rc)
-    BUG ();
+    return gpg_error (GPG_ERR_PUBKEY_ALGO);
 
-  /* Put the data into a simple list.  */
-  if (gcry_sexp_build (&s_data, NULL, "%m", data))
-    BUG ();
 
   /* Pass it to libgcrypt. */
   rc = gcry_pk_encrypt (&s_ciph, s_data, s_pkey);
@@ -184,12 +198,42 @@ pk_encrypt (int algo, gcry_mpi_t *resarr, gcry_mpi_t data,
 
   if (rc)
     ;
-  else
-    { /* Add better error handling or make gnupg use S-Exp directly.  */
+  else if (algo == PUBKEY_ALGO_ECDH)	
+    {
+      gcry_mpi_t shared, public, result;
+
+      /* Get the shared point and the ephemeral public key.  */
+      shared = mpi_from_sexp (s_ciph, "a"); 
+      public = mpi_from_sexp (s_ciph, "b");
+      gcry_sexp_release (s_ciph);
+      s_ciph = NULL;
+      if (DBG_CIPHER)
+        {
+          log_debug ("ECDH ephemeral key:");
+          gcry_mpi_dump (public);
+          log_printf ("\n");
+        }
+    
+      result = NULL;
+      rc = pk_ecdh_encrypt_with_shared_point (1 /*=encrypton*/, shared,
+                                              pk_fp, data, pkey, &result);
+      gcry_mpi_release (shared);
+      if (!rc)
+        {
+          resarr[0] = public;
+          resarr[1] = result;
+        }
+      else
+        {
+          gcry_mpi_release (public);
+          gcry_mpi_release (result);
+        }
+    }
+  else /* Elgamal or RSA case.  */
+    { /* Fixme: Add better error handling or make gnupg use
+         S-expressions directly.  */
       resarr[0] = mpi_from_sexp (s_ciph, "a");
-      if (algo != GCRY_PK_RSA 
-          && algo != GCRY_PK_RSA_E
-          && algo != PUBKEY_ALGO_ECDH)
+      if (algo != GCRY_PK_RSA && algo != GCRY_PK_RSA_E)
         resarr[1] = mpi_from_sexp (s_ciph, "b");
     }
 
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