Fix file IO ambiguity for UI scripts

The variable sm should contain the signature and the message,
not the message and the signature (i.e. the order is crucial).

test/xmss_open.c

@@ -12,7 +12,7 @@ int main(int argc, char **argv) {
 
     if (argc != 2) {
         fprintf(stderr, "Expected keypair filename as only parameter, "
-                        "and the message + signature via stdin.\n"
+                        "and the signature + message via stdin.\n"
                         "Keypair file needs only to contain the public key.\n"
                         "The return code 0 indicates verification success.\n");
         return -1;

test/xmss_sign.c

@@ -18,7 +18,7 @@ int main(int argc, char **argv) {
         return -1;
     }
 
-    keypair = fopen(argv[1], "rb");
+    keypair = fopen(argv[1], "r+b");
     if (keypair == NULL) {
         fprintf(stderr, "Could not open keypair file.\n");
         return -1;

test/xmssmt_open.c

@@ -12,7 +12,7 @@ int main(int argc, char **argv) {
 
     if (argc != 2) {
         fprintf(stderr, "Expected keypair filename as only parameter, "
-                        "and the message + signature via stdin.\n"
+                        "and the signature + message via stdin.\n"
                         "Keypair file needs only to contain the public key.\n"
                         "The return code 0 indicates verification success.\n");
         return -1;

test/xmssmt_sign.c

@@ -18,7 +18,7 @@ int main(int argc, char **argv) {
         return -1;
     }
 
-    keypair = fopen(argv[1], "rb");
+    keypair = fopen(argv[1], "r+b");
     if (keypair == NULL) {
         fprintf(stderr, "Could not open keypair file.\n");
         return -1;