commit 424fda5d7bbe86c351efd1d45a29b1e6b2a3980c
author Manuel Pégourié-Gonnard <mpg@elzevir.fr> Mon Feb 11 22:05:42 2013 +0100
committer Manuel Pégourié-Gonnard <mpg@elzevir.fr> Mon Feb 11 22:05:42 2013 +0100
tree 7d8c8b276cf6288e4805aa8567a8008180e3e5c0
parent 5cceb41d2c0c4c968374bea8411485e776f7c0ff

Add ecdh_calc_secret()

include/polarssl/ecdh.h

diff --git a/include/polarssl/ecdh.h b/include/polarssl/ecdh.h
index 67d1df5..7f6f4cb 100644
--- a/include/polarssl/ecdh.h
+++ b/include/polarssl/ecdh.h
@@ -150,6 +150,19 @@
                       const unsigned char *buf, size_t blen );
 
 /**
+ * \brief           Derive and export the shared secret
+ *
+ * \param ctx       ECDH context
+ * \param olen      number of bytes written
+ * \param buf       destination buffer
+ * \param blen      buffer length
+ *
+ * \return          0 if successful, or an POLARSSL_ERR_ECP_XXX error code
+ */
+int ecdh_calc_secret( ecdh_context *ctx, size_t *olen,
+                      unsigned char *buf, size_t blen );
+
+/**
  * \brief          Checkup routine
  *
  * \return         0 if successful, or 1 if the test failed

library/ecdh.c

diff --git a/library/ecdh.c b/library/ecdh.c
index dc585f4..c04d34c 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -186,6 +186,23 @@
     return ecp_tls_read_point( &ctx->grp, &ctx->Qp, &buf, blen );
 }
 
+/*
+ * Derive and export the shared secret
+ */
+int ecdh_calc_secret( ecdh_context *ctx, size_t *olen,
+                      unsigned char *buf, size_t blen )
+{
+    int ret;
+
+    if( ( ret = ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp, &ctx->d ) )
+                != 0 )
+        return( ret );
+
+    *olen = mpi_size( &ctx->z );
+    return mpi_write_binary( &ctx->z, buf, blen );
+}
+
+
 #if defined(POLARSSL_SELF_TEST)
 
 /*

tests/suites/test_suite_ecdh.function

diff --git a/tests/suites/test_suite_ecdh.function b/tests/suites/test_suite_ecdh.function
index 6f2d399..105f99c 100644
--- a/tests/suites/test_suite_ecdh.function
+++ b/tests/suites/test_suite_ecdh.function
@@ -99,11 +99,15 @@
                                    &rnd_pseudo_rand, &rnd_info ) == 0 );
     TEST_ASSERT( ecdh_read_params( &cli, &vbuf, buf + len ) == 0 );
 
-    memset( buf, 0x00, sizeof( buf ) ); vbuf = buf;
+    memset( buf, 0x00, sizeof( buf ) );
     TEST_ASSERT( ecdh_make_public( &cli, &len, buf, 1000,
                                    &rnd_pseudo_rand, &rnd_info ) == 0 );
     TEST_ASSERT( ecdh_read_public( &srv, buf, len ) == 0 );
 
+    TEST_ASSERT( ecdh_calc_secret( &srv, &len, buf, 1000 ) == 0 );
+    TEST_ASSERT( ecdh_calc_secret( &cli, &len, buf, 1000 ) == 0 );
+    TEST_ASSERT( mpi_cmp_mpi( &srv.z, &cli.z ) == 0 );
+
     ecdh_free( &srv );
     ecdh_free( &cli );
 }