Ignore domain parameters in RSA key generation

Remove the ability to select a custom public exponent via domain parameters
in RSA key generation. The only way to select a custom public exponent is
now to pass custom production parameters to psa_generate_key_ext().

A subsequent commit will remove domain parameters altogether from the API,
thus this commit does not bother to update the documentation.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto_rsa.c b/library/psa_crypto_rsa.c
index 4a574d1..472a0e8 100644
--- a/library/psa_crypto_rsa.c
+++ b/library/psa_crypto_rsa.c
@@ -223,11 +223,6 @@
     size_t i;
     uint32_t acc = 0;
 
-    if (domain_parameters_size == 0) {
-        *exponent = 65537;
-        return PSA_SUCCESS;
-    }
-
     /* Mbed TLS encodes the public exponent as an int. For simplicity, only
      * support values that fit in a 32-bit integer, which is larger than
      * int on just about every platform anyway. */
@@ -246,18 +241,20 @@
 
 psa_status_t mbedtls_psa_rsa_generate_key(
     const psa_key_attributes_t *attributes,
+    const psa_key_production_parameters_t *params, size_t params_data_length,
     uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length)
 {
     psa_status_t status;
     mbedtls_rsa_context rsa;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
-    int exponent;
+    int exponent = 65537;
 
-    status = psa_rsa_read_exponent(attributes->domain_parameters,
-                                   attributes->domain_parameters_size,
-                                   &exponent);
-    if (status != PSA_SUCCESS) {
-        return status;
+    if (params_data_length != 0) {
+        status = psa_rsa_read_exponent(params->data, params_data_length,
+                                       &exponent);
+        if (status != PSA_SUCCESS) {
+            return status;
+        }
     }
 
     mbedtls_rsa_init(&rsa);