Merge pull request #8664 from valeriosetti/issue7764

Conversion function from ecp group to PSA curve
diff --git a/ChangeLog.d/7764.txt b/ChangeLog.d/7764.txt
new file mode 100644
index 0000000..4cd2079
--- /dev/null
+++ b/ChangeLog.d/7764.txt
@@ -0,0 +1,3 @@
+Features
+   * Add functions mbedtls_ecc_group_to_psa() and mbedtls_ecc_group_from_psa()
+     to convert between Mbed TLS and PSA curve identifiers.
diff --git a/docs/psa-transition.md b/docs/psa-transition.md
index 067ffaf..617426c 100644
--- a/docs/psa-transition.md
+++ b/docs/psa-transition.md
@@ -725,7 +725,11 @@
 An ECC key pair has the type [`PSA_KEY_TYPE_ECC_KEY_PAIR(curve)`](https://mbed-tls.readthedocs.io/projects/api/en/development/api/group/group__crypto__types/#group__crypto__types_1ga0b6f5d4d5037c54ffa850d8059c32df0) where `curve` is a curve family identifier. A key with this type can be used both for private-key and public-key operations (there is no separate key type for a private key without the corresponding public key).
 You can always use a private key for operations on the corresponding public key (as long as the policy permits it).
 
-A curve is fully determined by a curve family identifier and the private key size in bits. The following table gives the correspondence between legacy and PSA elliptic curve designations.
+A curve is fully determined by a curve family identifier and the private key size in bits. You can use the following functions to convert between the PSA and legacy elliptic curve designations:
+- [`mbedtls_ecc_group_to_psa()`](https://mbed-tls.readthedocs.io/projects/api/en/development/api/group/group__psa__tls__helpers/#group__psa__tls__helpers_1ga9c83c095adfec7da99401cf81e164f99) converts from the legacy curve type identifier to PSA curve family and bit-size.
+- [`mbedtls_ecc_group_from_psa()`](https://mbed-tls.readthedocs.io/projects/api/en/development/api/group/group__psa__tls__helpers/#group__psa__tls__helpers_1ga6243eb619d5b2f5fe4667811adeb8a12) converts from PSA curve family and bit-size to the legacy identifier.
+
+The following table gives the correspondence between legacy and PSA elliptic curve designations.
 
 | Mbed TLS legacy curve identifier | PSA curve family | Curve bit-size |
 | -------------------------------- | ---------------- | -------------- |
diff --git a/include/mbedtls/psa_util.h b/include/mbedtls/psa_util.h
index 5f6a053..1b14256 100644
--- a/include/mbedtls/psa_util.h
+++ b/include/mbedtls/psa_util.h
@@ -110,42 +110,33 @@
 
 /** Convert an ECC curve identifier from the Mbed TLS encoding to PSA.
  *
- * \note This function is provided solely for the convenience of
- *       Mbed TLS and may be removed at any time without notice.
- *
  * \param grpid         An Mbed TLS elliptic curve identifier
  *                      (`MBEDTLS_ECP_DP_xxx`).
- * \param[out] bits     On success, the bit size of the curve.
+ * \param[out] bits     On success the bit size of the curve; 0 on failure.
  *
- * \return              The corresponding PSA elliptic curve identifier
- *                      (`PSA_ECC_FAMILY_xxx`).
- * \return              \c 0 on failure (\p grpid is not recognized).
+ * \return              If the curve is supported in the PSA API, this function
+ *                      returns the proper PSA curve identifier
+ *                      (`PSA_ECC_FAMILY_xxx`). This holds even if the curve is
+ *                      not supported by the ECP module.
+ * \return              \c 0 if the curve is not supported in the PSA API.
  */
 psa_ecc_family_t mbedtls_ecc_group_to_psa(mbedtls_ecp_group_id grpid,
                                           size_t *bits);
 
 /** Convert an ECC curve identifier from the PSA encoding to Mbed TLS.
  *
- * \note This function is provided solely for the convenience of
- *       Mbed TLS and may be removed at any time without notice.
- *
- * \param curve         A PSA elliptic curve identifier
+ * \param family        A PSA elliptic curve family identifier
  *                      (`PSA_ECC_FAMILY_xxx`).
  * \param bits          The bit-length of a private key on \p curve.
- * \param bits_is_sloppy If true, \p bits may be the bit-length rounded up
- *                      to the nearest multiple of 8. This allows the caller
- *                      to infer the exact curve from the length of a key
- *                      which is supplied as a byte string.
  *
- * \return              The corresponding Mbed TLS elliptic curve identifier
- *                      (`MBEDTLS_ECP_DP_xxx`).
- * \return              #MBEDTLS_ECP_DP_NONE if \c curve is not recognized.
- * \return              #MBEDTLS_ECP_DP_NONE if \p bits is not
- *                      correct for \p curve.
+ * \return              If the curve is supported in the PSA API, this function
+ *                      returns the corresponding Mbed TLS elliptic curve
+ *                      identifier (`MBEDTLS_ECP_DP_xxx`).
+ * \return              #MBEDTLS_ECP_DP_NONE if the combination of \c curve
+ *                      and \p bits is not supported.
  */
-mbedtls_ecp_group_id mbedtls_ecc_group_of_psa(psa_ecc_family_t curve,
-                                              size_t bits,
-                                              int bits_is_sloppy);
+mbedtls_ecp_group_id mbedtls_ecc_group_from_psa(psa_ecc_family_t family,
+                                                size_t bits);
 #endif /* PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY */
 
 /**@}*/
diff --git a/library/pk_internal.h b/library/pk_internal.h
index 025ee8b..3d5adf8 100644
--- a/library/pk_internal.h
+++ b/library/pk_internal.h
@@ -98,13 +98,13 @@
         }
         opaque_key_type = psa_get_key_type(&opaque_attrs);
         curve = PSA_KEY_TYPE_ECC_GET_FAMILY(opaque_key_type);
-        id = mbedtls_ecc_group_of_psa(curve, psa_get_key_bits(&opaque_attrs), 0);
+        id = mbedtls_ecc_group_from_psa(curve, psa_get_key_bits(&opaque_attrs));
         psa_reset_key_attributes(&opaque_attrs);
     } else
 #endif /* MBEDTLS_USE_PSA_CRYPTO */
     {
 #if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
-        id = mbedtls_ecc_group_of_psa(pk->ec_family, pk->ec_bits, 0);
+        id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits);
 #else /* MBEDTLS_PK_USE_PSA_EC_DATA */
         id = mbedtls_pk_ec_ro(*pk)->grp.id;
 #endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
diff --git a/library/pkparse.c b/library/pkparse.c
index d36fa3f..5f95545 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -250,7 +250,7 @@
     mbedtls_ecp_group_id ecp_group_id;
     int ret;
 
-    ecp_group_id = mbedtls_ecc_group_of_psa(pk->ec_family, pk->ec_bits, 0);
+    ecp_group_id = mbedtls_ecc_group_from_psa(pk->ec_family, pk->ec_bits);
 
     mbedtls_ecp_keypair_init(&ecp_key);
     ret = mbedtls_ecp_group_load(&(ecp_key.grp), ecp_group_id);
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index f17e14f..b4dffa9 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -5741,7 +5741,7 @@
     psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY(
         slot->attr.type);
     mbedtls_ecp_group_id grp_id =
-        mbedtls_ecc_group_of_psa(curve, bits, 0);
+        mbedtls_ecc_group_from_psa(curve, bits);
 
     if (grp_id == MBEDTLS_ECP_DP_NONE) {
         ret = MBEDTLS_ERR_ASN1_INVALID_DATA;
diff --git a/library/psa_crypto_ecp.c b/library/psa_crypto_ecp.c
index e4a372d..61c9414 100644
--- a/library/psa_crypto_ecp.c
+++ b/library/psa_crypto_ecp.c
@@ -32,6 +32,61 @@
     defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) || \
     defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) || \
     defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH)
+/* Helper function to verify if the provided EC's family and key bit size are valid.
+ *
+ * Note: "bits" parameter is used both as input and output and it might be updated
+ *       in case provided input value is not multiple of 8 ("sloppy" bits).
+ */
+static int check_ecc_parameters(psa_ecc_family_t family, size_t *bits)
+{
+    switch (family) {
+        case PSA_ECC_FAMILY_SECP_R1:
+            switch (*bits) {
+                case 192:
+                case 224:
+                case 256:
+                case 384:
+                case 521:
+                    return PSA_SUCCESS;
+                case 528:
+                    *bits = 521;
+                    return PSA_SUCCESS;
+            }
+            break;
+
+        case PSA_ECC_FAMILY_BRAINPOOL_P_R1:
+            switch (*bits) {
+                case 256:
+                case 384:
+                case 512:
+                    return PSA_SUCCESS;
+            }
+            break;
+
+        case PSA_ECC_FAMILY_MONTGOMERY:
+            switch (*bits) {
+                case 448:
+                case 255:
+                    return PSA_SUCCESS;
+                case 256:
+                    *bits = 255;
+                    return PSA_SUCCESS;
+            }
+            break;
+
+        case PSA_ECC_FAMILY_SECP_K1:
+            switch (*bits) {
+                case 192:
+                /* secp224k1 is not and will not be supported in PSA (#3541). */
+                case 256:
+                    return PSA_SUCCESS;
+            }
+            break;
+    }
+
+    return PSA_ERROR_INVALID_ARGUMENT;
+}
+
 psa_status_t mbedtls_psa_ecp_load_representation(
     psa_key_type_t type, size_t curve_bits,
     const uint8_t *data, size_t data_length,
@@ -82,16 +137,15 @@
     }
     mbedtls_ecp_keypair_init(ecp);
 
+    status = check_ecc_parameters(PSA_KEY_TYPE_ECC_GET_FAMILY(type), &curve_bits);
+    if (status != PSA_SUCCESS) {
+        goto exit;
+    }
+
     /* Load the group. */
-    grp_id = mbedtls_ecc_group_of_psa(PSA_KEY_TYPE_ECC_GET_FAMILY(type),
-                                      curve_bits, !explicit_bits);
+    grp_id = mbedtls_ecc_group_from_psa(PSA_KEY_TYPE_ECC_GET_FAMILY(type),
+                                        curve_bits);
     if (grp_id == MBEDTLS_ECP_DP_NONE) {
-        /* We can't distinguish between a nonsensical family/size combination
-         * (which would warrant PSA_ERROR_INVALID_ARGUMENT) and a
-         * well-regarded curve that Mbed TLS just doesn't know about (which
-         * would warrant PSA_ERROR_NOT_SUPPORTED). For uniformity with how
-         * curves that Mbed TLS knows about but for which support is disabled
-         * at build time, return NOT_SUPPORTED. */
         status = PSA_ERROR_NOT_SUPPORTED;
         goto exit;
     }
@@ -285,7 +339,7 @@
     psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY(
         attributes->core.type);
     mbedtls_ecp_group_id grp_id =
-        mbedtls_ecc_group_of_psa(curve, attributes->core.bits, 0);
+        mbedtls_ecc_group_from_psa(curve, attributes->core.bits);
 
     const mbedtls_ecp_curve_info *curve_info =
         mbedtls_ecp_curve_info_from_grp_id(grp_id);
diff --git a/library/psa_util.c b/library/psa_util.c
index 36b7175..41586e2 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -232,9 +232,7 @@
             return PSA_ECC_FAMILY_SECP_K1;
 #endif
 #if defined(MBEDTLS_ECP_HAVE_SECP224K1)
-        case MBEDTLS_ECP_DP_SECP224K1:
-            *bits = 224;
-            return PSA_ECC_FAMILY_SECP_K1;
+    /* secp224k1 is not and will not be supported in PSA (#3541). */
 #endif
 #if defined(MBEDTLS_ECP_HAVE_SECP256K1)
         case MBEDTLS_ECP_DP_SECP256K1:
@@ -252,11 +250,10 @@
     }
 }
 
-mbedtls_ecp_group_id mbedtls_ecc_group_of_psa(psa_ecc_family_t curve,
-                                              size_t bits,
-                                              int bits_is_sloppy)
+mbedtls_ecp_group_id mbedtls_ecc_group_from_psa(psa_ecc_family_t family,
+                                                size_t bits)
 {
-    switch (curve) {
+    switch (family) {
         case PSA_ECC_FAMILY_SECP_R1:
             switch (bits) {
 #if defined(PSA_WANT_ECC_SECP_R1_192)
@@ -278,11 +275,6 @@
 #if defined(PSA_WANT_ECC_SECP_R1_521)
                 case 521:
                     return MBEDTLS_ECP_DP_SECP521R1;
-                case 528:
-                    if (bits_is_sloppy) {
-                        return MBEDTLS_ECP_DP_SECP521R1;
-                    }
-                    break;
 #endif
             }
             break;
@@ -309,11 +301,6 @@
 #if defined(PSA_WANT_ECC_MONTGOMERY_255)
                 case 255:
                     return MBEDTLS_ECP_DP_CURVE25519;
-                case 256:
-                    if (bits_is_sloppy) {
-                        return MBEDTLS_ECP_DP_CURVE25519;
-                    }
-                    break;
 #endif
 #if defined(PSA_WANT_ECC_MONTGOMERY_448)
                 case 448:
@@ -329,8 +316,7 @@
                     return MBEDTLS_ECP_DP_SECP192K1;
 #endif
 #if defined(PSA_WANT_ECC_SECP_K1_224)
-                case 224:
-                    return MBEDTLS_ECP_DP_SECP224K1;
+            /* secp224k1 is not and will not be supported in PSA (#3541). */
 #endif
 #if defined(PSA_WANT_ECC_SECP_K1_256)
                 case 256:
@@ -340,7 +326,6 @@
             break;
     }
 
-    (void) bits_is_sloppy;
     return MBEDTLS_ECP_DP_NONE;
 }
 #endif /* PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY */
diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data
index 1bd8b65..eda6f5d 100644
--- a/tests/suites/test_suite_psa_crypto.data
+++ b/tests/suites/test_suite_psa_crypto.data
@@ -684,7 +684,7 @@
 
 PSA import EC keypair: explicit bit-size=255 for secp256r1
 depends_on:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_BASIC:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_IMPORT:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_EXPORT:PSA_WANT_ECC_SECP_R1_256
-import_with_data:"49c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eee":PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1):255:PSA_ERROR_NOT_SUPPORTED
+import_with_data:"49c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eee":PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1):255:PSA_ERROR_INVALID_ARGUMENT
 
 PSA import EC keypair: explicit bit-size=521 for secp521r1 (good)
 depends_on:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_BASIC:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_IMPORT:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_EXPORT:PSA_WANT_ECC_SECP_R1_521
@@ -692,7 +692,7 @@
 
 PSA import EC keypair: explicit bit-size=528 for secp521r1 (bad)
 depends_on:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_BASIC:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_IMPORT:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_EXPORT:PSA_WANT_ECC_SECP_R1_521
-import_with_data:"01b1b6ad07bb79e7320da59860ea28e055284f6058f279de666e06d435d2af7bda28d99fa47b7dd0963e16b0073078ee8b8a38d966a582f46d19ff95df3ad9685aae":PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1):528:PSA_ERROR_NOT_SUPPORTED
+import_with_data:"01b1b6ad07bb79e7320da59860ea28e055284f6058f279de666e06d435d2af7bda28d99fa47b7dd0963e16b0073078ee8b8a38d966a582f46d19ff95df3ad9685aae":PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1):528:PSA_ERROR_INVALID_ARGUMENT
 
 PSA import EC keypair: explicit bit-size, DER format
 depends_on:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_BASIC:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_IMPORT:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_EXPORT:PSA_WANT_ECC_SECP_R1_256
@@ -716,7 +716,7 @@
 
 PSA import EC keypair: implicit bit-size, not a valid length
 depends_on:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_BASIC:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_IMPORT:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_EXPORT:PSA_WANT_ECC_SECP_R1_256
-import_with_data:"0123456789abcdef0123456789abcdef":PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1):0:PSA_ERROR_NOT_SUPPORTED
+import_with_data:"0123456789abcdef0123456789abcdef":PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1):0:PSA_ERROR_INVALID_ARGUMENT
 
 PSA import EC keypair: secp256r1, all-bits-zero (bad)
 depends_on:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_BASIC:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_IMPORT:PSA_WANT_KEY_TYPE_ECC_KEY_PAIR_EXPORT:PSA_WANT_ECC_SECP_R1_256
@@ -7406,3 +7406,62 @@
 
 PSA derive persistent key: HKDF SHA-256, exportable
 persistent_key_load_key_from_storage:"0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b0b":PSA_KEY_TYPE_RAW_DATA:1024:PSA_KEY_USAGE_EXPORT:0:DERIVE_KEY
+
+ECP group ID <-> PSA family - SECP192R1
+depends_on:PSA_WANT_ECC_SECP_R1_192
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP192R1:PSA_ECC_FAMILY_SECP_R1:192
+
+ECP group ID <-> PSA family - SECP224R1
+depends_on:PSA_WANT_ECC_SECP_R1_224
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP224R1:PSA_ECC_FAMILY_SECP_R1:224
+
+ECP group ID <-> PSA family - SECP256R1
+depends_on:PSA_WANT_ECC_SECP_R1_256
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP256R1:PSA_ECC_FAMILY_SECP_R1:256
+
+ECP group ID <-> PSA family - SECP384R1
+depends_on:PSA_WANT_ECC_SECP_R1_384
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP384R1:PSA_ECC_FAMILY_SECP_R1:384
+
+ECP group ID <-> PSA family - SECP521R1
+depends_on:PSA_WANT_ECC_SECP_R1_521
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP521R1:PSA_ECC_FAMILY_SECP_R1:521
+
+ECP group ID <-> PSA family - BP256R1
+depends_on:PSA_WANT_ECC_BRAINPOOL_P_R1_256
+ecc_conversion_functions:MBEDTLS_ECP_DP_BP256R1:PSA_ECC_FAMILY_BRAINPOOL_P_R1:256
+
+ECP group ID <-> PSA family - BP384R1
+depends_on:PSA_WANT_ECC_BRAINPOOL_P_R1_384
+ecc_conversion_functions:MBEDTLS_ECP_DP_BP384R1:PSA_ECC_FAMILY_BRAINPOOL_P_R1:384
+
+ECP group ID <-> PSA family - BP512R1
+depends_on:PSA_WANT_ECC_BRAINPOOL_P_R1_512
+ecc_conversion_functions:MBEDTLS_ECP_DP_BP512R1:PSA_ECC_FAMILY_BRAINPOOL_P_R1:512
+
+ECP group ID <-> PSA family - CURVE25519
+depends_on:PSA_WANT_ECC_MONTGOMERY_255
+ecc_conversion_functions:MBEDTLS_ECP_DP_CURVE25519:PSA_ECC_FAMILY_MONTGOMERY:255
+
+ECP group ID <-> PSA family - SECP192K1
+depends_on:PSA_WANT_ECC_SECP_K1_192
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP192K1:PSA_ECC_FAMILY_SECP_K1:192
+
+ECP group ID <-> PSA family - SECP224K1
+depends_on:PSA_WANT_ECC_SECP_K1_224
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP224K1:PSA_ECC_FAMILY_SECP_K1:224
+
+ECP group ID <-> PSA family - SECP256K1
+depends_on:PSA_WANT_ECC_SECP_K1_256
+ecc_conversion_functions:MBEDTLS_ECP_DP_SECP256K1:PSA_ECC_FAMILY_SECP_K1:256
+
+ECP group ID <-> PSA family - CURVE448
+depends_on:PSA_WANT_ECC_MONTGOMERY_448
+ecc_conversion_functions:MBEDTLS_ECP_DP_CURVE448:PSA_ECC_FAMILY_MONTGOMERY:448
+
+ECP group ID <-> PSA family - Null values
+ecc_conversion_functions:MBEDTLS_ECP_DP_NONE:0:0
+
+ECP group ID <-> PSA family - Wrong values
+ecc_conversion_functions_fail
+
diff --git a/tests/suites/test_suite_psa_crypto.function b/tests/suites/test_suite_psa_crypto.function
index 4c08a90..7b6f5ae 100644
--- a/tests/suites/test_suite_psa_crypto.function
+++ b/tests/suites/test_suite_psa_crypto.function
@@ -6,6 +6,8 @@
 #include "mbedtls/oid.h"
 #include "common.h"
 
+#include "mbedtls/psa_util.h"
+
 /* For MBEDTLS_CTR_DRBG_MAX_REQUEST, knowing that psa_generate_random()
  * uses mbedtls_ctr_drbg internally. */
 #include "mbedtls/ctr_drbg.h"
@@ -9479,6 +9481,45 @@
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY */
+void ecc_conversion_functions(int grp_id_arg, int psa_family_arg, int bits_arg)
+{
+    mbedtls_ecp_group_id grp_id = grp_id_arg;
+    psa_ecc_family_t ecc_family = psa_family_arg;
+    size_t bits = bits_arg;
+    size_t bits_tmp;
+
+    TEST_EQUAL(ecc_family, mbedtls_ecc_group_to_psa(grp_id, &bits_tmp));
+    TEST_EQUAL(bits, bits_tmp);
+    TEST_EQUAL(grp_id, mbedtls_ecc_group_from_psa(ecc_family, bits));
+}
+/* END_CASE */
+
+/* BEGIN_CASE depends_on:PSA_WANT_KEY_TYPE_ECC_PUBLIC_KEY */
+void ecc_conversion_functions_fail()
+{
+    size_t bits;
+
+    /* Invalid legacy curve identifiers. */
+    TEST_EQUAL(0, mbedtls_ecc_group_to_psa(MBEDTLS_ECP_DP_MAX, &bits));
+    TEST_EQUAL(0, bits);
+    TEST_EQUAL(0, mbedtls_ecc_group_to_psa(MBEDTLS_ECP_DP_NONE, &bits));
+    TEST_EQUAL(0, bits);
+
+    /* Invalid PSA EC family. */
+    TEST_EQUAL(MBEDTLS_ECP_DP_NONE, mbedtls_ecc_group_from_psa(0, 192));
+    /* Invalid bit-size for a valid EC family. */
+    TEST_EQUAL(MBEDTLS_ECP_DP_NONE, mbedtls_ecc_group_from_psa(PSA_ECC_FAMILY_SECP_R1, 512));
+
+    /* Twisted-Edward curves are not supported yet. */
+    TEST_EQUAL(MBEDTLS_ECP_DP_NONE,
+               mbedtls_ecc_group_from_psa(PSA_ECC_FAMILY_TWISTED_EDWARDS, 255));
+    TEST_EQUAL(MBEDTLS_ECP_DP_NONE,
+               mbedtls_ecc_group_from_psa(PSA_ECC_FAMILY_TWISTED_EDWARDS, 448));
+}
+/* END_CASE */
+
+
 /* BEGIN_CASE */
 void key_agreement_output(int alg_arg,
                           int our_key_type_arg, data_t *our_key_data,