Introduce mbedtls_ssl_get_ciphersuite_sig_pk_ext_alg() and use it in ssl_pick_cert()

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/library/ssl_ciphersuites.c b/library/ssl_ciphersuites.c
index 7deb57a..73a99e3 100644
--- a/library/ssl_ciphersuites.c
+++ b/library/ssl_ciphersuites.c
@@ -1921,6 +1921,53 @@
     }
 }
 
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+psa_algorithm_t mbedtls_ssl_get_ciphersuite_sig_pk_ext_alg( const mbedtls_ssl_ciphersuite_t *info )
+{
+    switch( info->key_exchange )
+    {
+        case MBEDTLS_KEY_EXCHANGE_RSA:
+        case MBEDTLS_KEY_EXCHANGE_RSA_PSK:
+            return( PSA_ALG_RSA_PKCS1V15_CRYPT );
+        case MBEDTLS_KEY_EXCHANGE_DHE_RSA:
+        case MBEDTLS_KEY_EXCHANGE_ECDHE_RSA:
+            return( PSA_ALG_RSA_PKCS1V15_SIGN(
+                        mbedtls_psa_translate_md( info->mac ) ) );
+
+        case MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA:
+            return( PSA_ALG_ECDSA( mbedtls_psa_translate_md( info->mac ) ) );
+
+        case MBEDTLS_KEY_EXCHANGE_ECDH_RSA:
+        case MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA:
+            return( PSA_ALG_ECDH );
+
+        default:
+            return( PSA_ALG_NONE );
+    }
+}
+
+psa_key_usage_t mbedtls_ssl_get_ciphersuite_sig_pk_ext_usage( const mbedtls_ssl_ciphersuite_t *info )
+{
+    switch( info->key_exchange )
+    {
+        case MBEDTLS_KEY_EXCHANGE_RSA:
+        case MBEDTLS_KEY_EXCHANGE_RSA_PSK:
+            return( PSA_KEY_USAGE_DECRYPT );
+        case MBEDTLS_KEY_EXCHANGE_DHE_RSA:
+        case MBEDTLS_KEY_EXCHANGE_ECDHE_RSA:
+        case MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA:
+            return( PSA_KEY_USAGE_SIGN_HASH );
+
+        case MBEDTLS_KEY_EXCHANGE_ECDH_RSA:
+        case MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA:
+            return( PSA_KEY_USAGE_DERIVE );
+
+        default:
+            return( 0 );
+    }
+}
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
 mbedtls_pk_type_t mbedtls_ssl_get_ciphersuite_sig_alg( const mbedtls_ssl_ciphersuite_t *info )
 {
     switch( info->key_exchange )