test: pk: keep PK_WRITE_C only in RSA tests

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/suites/test_suite_pk.data b/tests/suites/test_suite_pk.data
index 531a2f1..01d8d2d 100644
--- a/tests/suites/test_suite_pk.data
+++ b/tests/suites/test_suite_pk.data
@@ -618,7 +618,7 @@
 pk_psa_sign:MBEDTLS_ECP_DP_BP512R1:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_BRAINPOOL_P_R1):512
 
 PSA wrapped sign: RSA PKCS1 v1.5
-depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_GENPRIME
+depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_GENPRIME:MBEDTLS_PK_WRITE_C
 pk_psa_sign:1024:PSA_KEY_TYPE_RSA_KEY_PAIR:1024
 
 PK Sign ext:RSA2048,PK_RSA,MD_SHA256
diff --git a/tests/suites/test_suite_pk.function b/tests/suites/test_suite_pk.function
index 9ec354e..f124c9a 100644
--- a/tests/suites/test_suite_pk.function
+++ b/tests/suites/test_suite_pk.function
@@ -1182,7 +1182,7 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE depends_on:MBEDTLS_HAS_ALG_SHA_256_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO:MBEDTLS_PK_WRITE_C */
+/* BEGIN_CASE depends_on:MBEDTLS_HAS_ALG_SHA_256_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_USE_PSA_CRYPTO */
 void pk_psa_sign(int parameter_arg,
                  int psa_type_arg, int expected_bits_arg)
 {
@@ -1242,12 +1242,22 @@
     }
 
     /* Export underlying public key for re-importing in a legacy context. */
+#if defined(MBEDTLS_PK_WRITE_C)
     ret = mbedtls_pk_write_pubkey_der(&pk, pkey_legacy,
                                       sizeof(pkey_legacy));
     TEST_ASSERT(ret >= 0);
     klen_legacy = (size_t) ret;
     /* mbedtls_pk_write_pubkey_der() writes backwards in the data buffer. */
     pkey_legacy_start = pkey_legacy + sizeof(pkey_legacy) - klen_legacy;
+#else
+    ret = mbedtls_ecp_point_write_binary(&(mbedtls_pk_ec(pk)->grp),
+                                        &(mbedtls_pk_ec(pk)->Q),
+                                        MBEDTLS_ECP_PF_UNCOMPRESSED,
+                                        &klen_legacy, pkey_legacy,
+                                        sizeof(pkey_legacy));
+    TEST_EQUAL(ret, 0);
+    pkey_legacy_start = pkey_legacy;
+#endif /* MBEDTLS_PK_WRITE_C */
 
     /* Turn PK context into an opaque one. */
     TEST_ASSERT(mbedtls_pk_wrap_as_opaque(&pk, &key_id, alg_psa,
@@ -1268,12 +1278,21 @@
                                 NULL, NULL) == 0);
 
     /* Export underlying public key for re-importing in a psa context. */
+#if defined(MBEDTLS_PK_WRITE_C)
     ret = mbedtls_pk_write_pubkey_der(&pk, pkey_psa,
                                       sizeof(pkey_psa));
     TEST_ASSERT(ret >= 0);
     klen_psa = (size_t) ret;
     /* mbedtls_pk_write_pubkey_der() writes backwards in the data buffer. */
     pkey_psa_start = pkey_psa + sizeof(pkey_psa) - klen_psa;
+#else
+    psa_status_t status;
+
+    status = psa_export_public_key(key_id, pkey_psa, sizeof(pkey_psa),
+                                &klen_psa);
+    TEST_EQUAL(status, PSA_SUCCESS);
+    pkey_psa_start = pkey_psa;
+#endif /* MBEDTLS_PK_WRITE_C */
 
     TEST_ASSERT(klen_psa == klen_legacy);
     TEST_ASSERT(memcmp(pkey_psa_start, pkey_legacy_start, klen_psa) == 0);
@@ -1282,8 +1301,24 @@
     TEST_ASSERT(PSA_SUCCESS == psa_destroy_key(key_id));
 
     mbedtls_pk_init(&pk);
-    TEST_ASSERT(mbedtls_pk_parse_public_key(&pk, pkey_legacy_start,
-                                            klen_legacy) == 0);
+
+    /* If we used "pk_write" previously, then we go for a "pk_parse" here;
+     * otherwise if we went for "ecp_point_write_binary" then we'll go
+     * for a "ecp_point_read_binary" here. This allows to drop dependencies
+     * on "PK_WRITE" and "PK_PARSE" if required */
+#if defined(MBEDTLS_PK_WRITE_C) && defined(MBEDTLS_PK_PARSE_C)
+    TEST_EQUAL(mbedtls_pk_parse_public_key(&pk, pkey_legacy_start,
+                                            klen_legacy), 0);
+#else
+    TEST_EQUAL(mbedtls_pk_setup(&pk,
+                        mbedtls_pk_info_from_type(MBEDTLS_PK_ECKEY)), 0);
+    TEST_EQUAL(mbedtls_ecp_group_load(
+                                &(mbedtls_pk_ec(pk)->grp),
+                                (mbedtls_ecp_group_id) parameter_arg), 0);
+    TEST_EQUAL(mbedtls_ecp_point_read_binary(&(mbedtls_pk_ec(pk)->grp) ,
+                                        &(mbedtls_pk_ec(pk)->Q),
+                                        pkey_legacy_start, klen_legacy), 0);
+#endif
     TEST_ASSERT(mbedtls_pk_verify(&pk, MBEDTLS_MD_SHA256,
                                   hash, sizeof(hash), sig, sig_len) == 0);