Merge pull request #8863 from minosgalanakis/feature/add_ecdh_context_5016

[MBEDTLS_PRIVATE] Add a getter for the ECDH context->grp.id member.

ChangeLog.d/add_get_ecp_group_id.txt

@@ -0,0 +1,3 @@
+Features
+   * Add new accessor to expose the private group id member of
+     `mbedtls_ecdh_context` structure.

include/mbedtls/ecdh.h

@@ -141,6 +141,19 @@ typedef struct mbedtls_ecdh_context {
 }
 mbedtls_ecdh_context;
 
+/**
+ * \brief          Return the ECP group for provided context.
+ *
+ * \note           To access group specific fields, users should use
+ *                 `mbedtls_ecp_curve_info_from_grp_id` or
+ *                 `mbedtls_ecp_group_load` on the extracted `group_id`.
+ *
+ * \param ctx      The ECDH context to parse. This must not be \c NULL.
+ *
+ * \return         The \c mbedtls_ecp_group_id of the context.
+ */
+mbedtls_ecp_group_id mbedtls_ecdh_get_grp_id(mbedtls_ecdh_context *ctx);
+
 /**
  * \brief          Check whether a given group can be used for ECDH.
  *

library/ecdh.c

@@ -144,6 +144,15 @@ static void ecdh_init_internal(mbedtls_ecdh_context_mbed *ctx)
 #endif
 }
 
+mbedtls_ecp_group_id mbedtls_ecdh_get_grp_id(mbedtls_ecdh_context *ctx)
+{
+#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
+    return ctx->MBEDTLS_PRIVATE(grp).id;
+#else
+    return ctx->MBEDTLS_PRIVATE(grp_id);
+#endif
+}
+
 /*
  * Initialize context
  */

tests/suites/test_suite_ecdh.data

@@ -100,3 +100,19 @@ ecdh_exchange_get_params_fail:MBEDTLS_ECP_DP_BP256R1:"12345678123456781234567812
 ECDH get_params with mismatched groups: their SECP256R1, our BP256R1
 depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECP_DP_BP256R1_ENABLED
 ecdh_exchange_get_params_fail:MBEDTLS_ECP_DP_BP256R1:"1234567812345678123456781234567812345678123456781234567812345678":MBEDTLS_ECP_DP_SECP256R1:"04dad0b65394221cf9b051e1feca5787d098dfe637fc90b9ef945d0c37725811805271a0461cdb8252d61f1c456fa3e59ab1f45b33accf5f58389e0577b8990bb3":1:MBEDTLS_ERR_ECP_BAD_INPUT_DATA
+
+Context get ECP Group #1
+depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+ecdh_context_grp:MBEDTLS_ECP_DP_SECP256R1
+
+Context get ECP Group #2
+depends_on:MBEDTLS_ECP_DP_SECP384R1_ENABLED
+ecdh_primitive_random:MBEDTLS_ECP_DP_SECP384R1
+
+Context get ECP Group #3
+depends_on:MBEDTLS_ECP_DP_SECP521R1_ENABLED
+ecdh_primitive_random:MBEDTLS_ECP_DP_SECP521R1
+
+Context get ECP Group #4
+depends_on:MBEDTLS_ECP_DP_CURVE448_ENABLED
+ecdh_primitive_random:MBEDTLS_ECP_DP_CURVE448

tests/suites/test_suite_ecdh.function

@@ -464,3 +464,20 @@ exit:
     mbedtls_ecp_keypair_free(&their_key);
 }
 /* END_CASE */
+
+/* BEGIN_CASE */
+void ecdh_context_grp(int id)
+{
+    mbedtls_ecdh_context srv;
+
+    mbedtls_ecdh_init(&srv);
+    TEST_ASSERT(mbedtls_ecdh_setup(&srv, id) == 0);
+
+    /* Test the retrieved group id matches/*/
+    TEST_ASSERT((int) mbedtls_ecdh_get_grp_id(&srv) == id);
+
+exit:
+    mbedtls_ecdh_free(&srv);
+
+}
+/* END_CASE */