wolfsshd: compare the terminated copy in GetConfigInt

- The zero check ran WSTRCMP() on the caller's buffer, which is a
  length-bounded slice of the config line and not NUL terminated, so it
  read past inSz and rejected valid "0" values whose slice had trailing
  text.
- Compare num, the NUL-terminated copy that atol() was given.

Issue: F-7213

apps/wolfsshd/configuration.c

@@ -151,7 +151,7 @@ static long GetConfigInt(const char* in, int inSz, int isTime, void* heap)
             WMEMCPY(num, in, sz);
             num[sz] = '\0';
             ret = atol(num);
-            if (ret == 0 && WSTRCMP(in, "0") != 0) {
+            if (ret == 0 && WSTRCMP(num, "0") != 0) {
                 ret = WS_BAD_ARGUMENT;
             }
             else if (ret > 0) {

apps/wolfsshd/test/test_configuration.c

@@ -301,6 +301,10 @@ static int test_ParseConfigLine(void)
         {"Invalid login grace time", "LoginGraceTime wolfsshd", 1},
         {"Bare multiplier m (no digit)", "LoginGraceTime m", 1},
         {"Bare multiplier h (no digit)", "LoginGraceTime h", 1},
+        {"Valid login grace time zero", "LoginGraceTime 0", 0},
+        {"Valid login grace time zero minutes", "LoginGraceTime 0m", 0},
+        {"Valid login grace time zero hours", "LoginGraceTime 0h", 0},
+        {"Invalid zero padded login grace time", "LoginGraceTime 00", 1},
 
         /* Permit empty password tests. */
         {"Permit empty password no", "PermitEmptyPasswords no", 0},