commit c80555d8359c736e01f9bd24ce37d4704f11950b
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Thu Apr 20 15:37:46 2017 +0200
committer Janos Follath <janos.follath@arm.com> Wed Jan 16 15:47:26 2019 +0000
tree 9e4cb9e3886ca1f11076252574d3fced74dc0b44
parent 78f040cf333e8f2938b4581f11a015e474a4a250

Add public function generating private keys

We need to separate the uses of the RNG for blinding and for key
generation for the sake of an upcoming security fix in deterministic
ECDSA.

include/mbedtls/ecp.h

diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 7b8ffff..9c6db19 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -596,6 +596,22 @@
 int mbedtls_ecp_check_privkey( const mbedtls_ecp_group *grp, const mbedtls_mpi *d );
 
 /**
+ * \brief           Generate a private key
+ *
+ * \param grp       ECP group
+ * \param d         Destination MPI (secret part)
+ * \param f_rng     RNG function
+ * \param p_rng     RNG parameter
+ *
+ * \return          0 if successful,
+ *                  or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
+ */
+int mbedtls_ecp_gen_privkey( const mbedtls_ecp_group *grp,
+                     mbedtls_mpi *d,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng );
+
+/**
  * \brief           Generate a keypair with configurable base point
  *
  * \param grp       ECP group

library/ecp.c

diff --git a/library/ecp.c b/library/ecp.c
index 75233f8..cb8e947 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1918,15 +1918,14 @@
 }
 
 /*
- * Generate a keypair with configurable base point
+ * Generate a private key
  */
-int mbedtls_ecp_gen_keypair_base( mbedtls_ecp_group *grp,
-                     const mbedtls_ecp_point *G,
-                     mbedtls_mpi *d, mbedtls_ecp_point *Q,
+int mbedtls_ecp_gen_privkey( const mbedtls_ecp_group *grp,
+                     mbedtls_mpi *d,
                      int (*f_rng)(void *, unsigned char *, size_t),
                      void *p_rng )
 {
-    int ret;
+    int ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
     size_t n_size = ( grp->nbits + 7 ) / 8;
 
 #if defined(ECP_MONTGOMERY)
@@ -1951,8 +1950,8 @@
         MBEDTLS_MPI_CHK( mbedtls_mpi_set_bit( d, 1, 0 ) );
         MBEDTLS_MPI_CHK( mbedtls_mpi_set_bit( d, 2, 0 ) );
     }
-    else
 #endif /* ECP_MONTGOMERY */
+
 #if defined(ECP_SHORTWEIERSTRASS)
     if( ecp_get_type( grp ) == ECP_TYPE_SHORT_WEIERSTRASS )
     {
@@ -1986,15 +1985,28 @@
         while( mbedtls_mpi_cmp_int( d, 1 ) < 0 ||
                mbedtls_mpi_cmp_mpi( d, &grp->N ) >= 0 );
     }
-    else
 #endif /* ECP_SHORTWEIERSTRASS */
-        return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
 cleanup:
-    if( ret != 0 )
-        return( ret );
+    return( ret );
+}
 
-    return( mbedtls_ecp_mul( grp, Q, d, G, f_rng, p_rng ) );
+/*
+ * Generate a keypair with configurable base point
+ */
+int mbedtls_ecp_gen_keypair_base( mbedtls_ecp_group *grp,
+                     const mbedtls_ecp_point *G,
+                     mbedtls_mpi *d, mbedtls_ecp_point *Q,
+                     int (*f_rng)(void *, unsigned char *, size_t),
+                     void *p_rng )
+{
+    int ret;
+
+    MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, d, f_rng, p_rng ) );
+    MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, Q, d, G, f_rng, p_rng ) );
+
+cleanup:
+    return( ret );
 }
 
 /*