Revert "Merged RSA-PSS support in Certificate, CSR and CRL"

This reverts commit ab50d8d30c22f38e3e2d2373219cfbeb1940082e, reversing
changes made to e31b1d992ad0a3874646c73a44f3eb750d13e900.
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 4c79a7a..d18e117 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -529,9 +529,6 @@
     int ret;
     size_t len;
     unsigned char *p, *end, *crt_end;
-    x509_buf sig_params;
-
-    memset( &sig_params, 0, sizeof( x509_buf ) );
 
     /*
      * Check for valid input
@@ -595,8 +592,7 @@
      */
     if( ( ret = x509_get_version(  &p, end, &crt->version  ) ) != 0 ||
         ( ret = x509_get_serial(   &p, end, &crt->serial   ) ) != 0 ||
-        ( ret = x509_get_alg(      &p, end, &crt->sig_oid1,
-                                            &sig_params ) ) != 0 )
+        ( ret = x509_get_alg_null( &p, end, &crt->sig_oid1 ) ) != 0 )
     {
         x509_crt_free( crt );
         return( ret );
@@ -610,17 +606,13 @@
         return( POLARSSL_ERR_X509_UNKNOWN_VERSION );
     }
 
-    if( ( ret = x509_get_sig_alg( &crt->sig_oid1, &sig_params,
-                                  &crt->sig_md, &crt->sig_pk ) ) != 0 )
+    if( ( ret = x509_get_sig_alg( &crt->sig_oid1, &crt->sig_md,
+                                  &crt->sig_pk ) ) != 0 )
     {
         x509_crt_free( crt );
         return( ret );
     }
 
-#if defined(POLARSSL_RSASSA_PSS_CERTIFICATES)
-    memcpy( &crt->sig_params, &sig_params, sizeof( x509_buf ) );
-#endif
-
     /*
      * issuer               Name
      */
@@ -741,20 +733,14 @@
      *  signatureAlgorithm   AlgorithmIdentifier,
      *  signatureValue       BIT STRING
      */
-    if( ( ret = x509_get_alg( &p, end, &crt->sig_oid2, &sig_params ) ) != 0 )
+    if( ( ret = x509_get_alg_null( &p, end, &crt->sig_oid2 ) ) != 0 )
     {
         x509_crt_free( crt );
         return( ret );
     }
 
     if( crt->sig_oid1.len != crt->sig_oid2.len ||
-        memcmp( crt->sig_oid1.p, crt->sig_oid2.p, crt->sig_oid1.len ) != 0
-#if defined(POLARSSL_RSASSA_PSS_CERTIFICATES)
-        ||
-        crt->sig_params.len != sig_params.len ||
-        memcmp( crt->sig_params.p, sig_params.p, sig_params.len ) != 0
-#endif
-        )
+        memcmp( crt->sig_oid1.p, crt->sig_oid2.p, crt->sig_oid1.len ) != 0 )
     {
         x509_crt_free( crt );
         return( POLARSSL_ERR_X509_SIG_MISMATCH );
@@ -1124,12 +1110,8 @@
     int ret;
     size_t n;
     char *p;
+    const char *desc = NULL;
     char key_size_str[BEFORE_COLON];
-#if defined(POLARSSL_RSASSA_PSS_CERTIFICATES)
-    const x509_buf *sig_params = &crt->sig_params;
-#else
-    const x509_buf *sig_params = NULL;
-#endif
 
     p = buf;
     n = size;
@@ -1171,7 +1153,11 @@
     ret = snprintf( p, n, "\n%ssigned using  : ", prefix );
     SAFE_SNPRINTF();
 
-    ret = x509_sig_alg_gets( p, n, &crt->sig_oid1, crt->sig_pk, sig_params );
+    ret = oid_get_sig_alg_desc( &crt->sig_oid1, &desc );
+    if( ret != 0 )
+        ret = snprintf( p, n, "???"  );
+    else
+        ret = snprintf( p, n, "%s", desc );
     SAFE_SNPRINTF();
 
     if( ( ret = x509_key_size_helper( key_size_str, BEFORE_COLON,