commit 52cc2a6368872eb2116bc3ed1066e884920e91fa
author Gilles Peskine <Gilles.Peskine@arm.com> Thu Jun 22 22:32:05 2023 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Sun Dec 24 19:49:43 2023 +0100
tree 8510f5c6d06adae4ac9fce3f928d3d2c30efaa76
parent 62e33bcc64c05027a5873830b7a26dbdbb84f282

Use new mbedtls_ecp_keypair functions in sample programs

This eliminates the use of MBEDTLS_PRIVATE in sample programs to access
fields of an mbedtls_ecp_keypair structure.

When displaying elliptic curve points, the program now display the
coordinates in the standard form instead of the internal representation.

The auxiliary function show_ecp_key is present in three programs. It's more
complex than the previous code which was also triplicated. There's no good
place for such auxiliary functions that don't belong in the library and are
used in multiple sample programs.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

programs/pkey/ecdsa.c

diff --git a/programs/pkey/ecdsa.c b/programs/pkey/ecdsa.c
index afd6fb3..5664b8c 100644
--- a/programs/pkey/ecdsa.c
+++ b/programs/pkey/ecdsa.c
@@ -60,8 +60,8 @@
     unsigned char buf[300];
     size_t len;
 
-    if (mbedtls_ecp_point_write_binary(&key->MBEDTLS_PRIVATE(grp), &key->MBEDTLS_PRIVATE(Q),
-                                       MBEDTLS_ECP_PF_UNCOMPRESSED, &len, buf, sizeof(buf)) != 0) {
+    if (mbedtls_ecp_write_public_key(key, MBEDTLS_ECP_PF_UNCOMPRESSED,
+                                     &len, buf, sizeof(buf)) != 0) {
         mbedtls_printf("internal error\n");
         return;
     }
@@ -79,6 +79,8 @@
     int ret = 1;
     int exit_code = MBEDTLS_EXIT_FAILURE;
     mbedtls_ecdsa_context ctx_sign, ctx_verify;
+    mbedtls_ecp_point Q;
+    mbedtls_ecp_point_init(&Q);
     mbedtls_entropy_context entropy;
     mbedtls_ctr_drbg_context ctr_drbg;
     unsigned char message[100];
@@ -128,7 +130,10 @@
         goto exit;
     }
 
-    mbedtls_printf(" ok (key size: %d bits)\n", (int) ctx_sign.MBEDTLS_PRIVATE(grp).pbits);
+    mbedtls_ecp_group_id grp_id = mbedtls_ecp_keypair_get_group_id(&ctx_sign);
+    const mbedtls_ecp_curve_info *curve_info =
+        mbedtls_ecp_curve_info_from_grp_id(grp_id);
+    mbedtls_printf(" ok (key size: %d bits)\n", (int) curve_info->bit_size);
 
     dump_pubkey("  + Public key: ", &ctx_sign);
 
@@ -174,16 +179,13 @@
     mbedtls_printf("  . Preparing verification context...");
     fflush(stdout);
 
-    if ((ret =
-             mbedtls_ecp_group_copy(&ctx_verify.MBEDTLS_PRIVATE(grp),
-                                    &ctx_sign.MBEDTLS_PRIVATE(grp))) != 0) {
-        mbedtls_printf(" failed\n  ! mbedtls_ecp_group_copy returned %d\n", ret);
+    if ((ret = mbedtls_ecp_export(&ctx_sign, NULL, NULL, &Q)) != 0) {
+        mbedtls_printf(" failed\n  ! mbedtls_ecp_export returned %d\n", ret);
         goto exit;
     }
 
-    if ((ret =
-             mbedtls_ecp_copy(&ctx_verify.MBEDTLS_PRIVATE(Q), &ctx_sign.MBEDTLS_PRIVATE(Q))) != 0) {
-        mbedtls_printf(" failed\n  ! mbedtls_ecp_copy returned %d\n", ret);
+    if ((ret = mbedtls_ecp_set_public_key(grp_id, &ctx_verify, &Q)) != 0) {
+        mbedtls_printf(" failed\n  ! mbedtls_ecp_set_public_key returned %d\n", ret);
         goto exit;
     }
 
@@ -208,6 +210,7 @@
 
     mbedtls_ecdsa_free(&ctx_verify);
     mbedtls_ecdsa_free(&ctx_sign);
+    mbedtls_ecp_point_free(&Q);
     mbedtls_ctr_drbg_free(&ctr_drbg);
     mbedtls_entropy_free(&entropy);