Change: extended the nasl functions ereg(), egrep(), eregmatch(). (#1044

)

* Change: extended the nasl functions ereg(), egrep(), eregmatch().
Now, they accept a new parameter "rnul" (replace null) with . This option will replace the null char '\0' with '\x00'.
If you use this option and you want to match the null char (replaced), you must adjust the regex to search for '\\x00' (it is replaces with 4 chars, so the back slash must be escaped as well).

Example:
```
string = 'NASL' + raw_string(0x00) + 'Test';

if(egrep(string:string, pattern:"NASL\\x00Test", icase:FALSE, rnul:TRUE))     #   <<<<<<<<<< Searchs for the replacement, escaping the backslash.
  display("egrep succeeded");
else
  display("egrep failed");

if(eregmatch(string:string, pattern:"NASL.+Test", icase:FALSE, rnul:TRUE))
  display("eregmatch succeeded");
else
  display("eregmatch failed");

if(ereg(string:string, pattern:"NASL.+Test", icase:FALSE, rnul:TRUE))
  display("ereg succeeded");
else
  display("ereg failed");
```
 

Output:
```
$ openvas-nasl -X -B -d -i $PLUGINSPATH regex.nasl
lib  nasl-Message: 08:29:21.150: egrep succeeded
lib  nasl-Message: 08:29:21.150: eregmatch succeeded
lib  nasl-Message: 08:29:21.151: ereg succeeded
```

* Make the new nul char replacement, the default behaviour

nasl/nasl_text_utils.c

@@ -443,19 +443,30 @@ nasl_toupper (lex_ctxt *lexic)
 
 /*---------------------------------------------------------------------*/
 
-/*
- * regex syntax :
+/**
+ * @brief Matches a string against a regular expression.
+ * @naslfn{egrep}
  *
- *	ereg(pattern, string)
+ * @naslnparam
+ * - @a string  String to search the pattern in
+ * - @a pattern the patern that should be matched
+ * - @a icase   case insensitive flag
+ * - @a rnul    replace the null char in the string. Default TRUE.
+ * - @a multiline Is FALSE by default (string is truncated at the first
+ *                “end of line”), and can be set to TRUE for multiline search.
+ * @naslret The first found pattern.
+ *
+ * @param[in] lexic Lexical context of NASL interpreter.
  */
-
 tree_cell *
 nasl_ereg (lex_ctxt *lexic)
 {
   char *pattern = get_str_var_by_name (lexic, "pattern");
   char *string = get_str_var_by_name (lexic, "string");
   int icase = get_int_var_by_name (lexic, "icase", 0);
   int multiline = get_int_var_by_name (lexic, "multiline", 0);
+  int replace_nul = get_int_var_by_name (lexic, "rnul", 1);
+  int max_size = get_var_size_by_name (lexic, "string");
   char *s;
   int copt = 0;
   tree_cell *retc;
@@ -475,7 +486,12 @@ nasl_ereg (lex_ctxt *lexic)
     }
 
   retc = alloc_typed_cell (CONST_INT);
-  string = g_strdup (string);
+
+  if (replace_nul)
+    string = g_regex_escape_nul (string, max_size);
+  else
+    string = g_strdup (string);
+
   if (multiline)
     s = NULL;
   else
@@ -648,13 +664,31 @@ _regreplace (const char *pattern, const char *replace, const char *string,
   return (buf);
 }
 
+/**
+ * @brief Search for a pattern in a string and replace it
+ * @naslfn{ereg_replace}
+ *
+ * @naslnparam
+ * - @a string  String to search the pattern in
+ * - @a pattern patern to search in the string for
+ * - @a replace string to replace the pattern with
+ * - @a icase   case insensitive flag
+ * - @a rnul    replace the null char in the string. Default TRUE.
+ *
+ * @naslret The new string with the pattern replaced with replace
+ *
+ * @param[in] lexic Lexical context of NASL interpreter.
+ */
 tree_cell *
 nasl_ereg_replace (lex_ctxt *lexic)
 {
   char *pattern = get_str_var_by_name (lexic, "pattern");
   char *replace = get_str_var_by_name (lexic, "replace");
   char *string = get_str_var_by_name (lexic, "string");
   int icase = get_int_var_by_name (lexic, "icase", 0);
+  int replace_nul = get_int_var_by_name (lexic, "rnul", 1);
+  int max_size = get_var_size_by_name (lexic, "string");
+
   char *r;
   tree_cell *retc;
 
@@ -668,6 +702,11 @@ nasl_ereg_replace (lex_ctxt *lexic)
   if (string == NULL)
     return NULL;
 
+  if (replace_nul)
+    string = g_regex_escape_nul (string, max_size);
+  else
+    string = g_strdup (string);
+
   r = _regreplace (pattern, replace, string, icase, 1);
   if (r == NULL)
     return FAKE_CELL;
@@ -681,17 +720,27 @@ nasl_ereg_replace (lex_ctxt *lexic)
 
 /*---------------------------------------------------------------------*/
 
-/*
- * regex syntax :
+/**
+ * @brief looks for a pattern in a string, line by line.
+ * @naslfn{egrep}
  *
- *	egrep(pattern, string)
+ * @naslnparam
+ * - @a string  String to search the pattern in
+ * - @a pattern the patern that should be matched
+ * - @a icase   case insensitive flag
+ * - @a rnul    replace the null char in the string. Default TRUE.
+ *
+ * @naslret  The concatenation of all lines that match. Null otherwise.
+ *
+ * @param[in] lexic Lexical context of NASL interpreter.
  */
 tree_cell *
 nasl_egrep (lex_ctxt *lexic)
 {
   char *pattern = get_str_var_by_name (lexic, "pattern");
   char *string = get_str_var_by_name (lexic, "string");
   int icase = get_int_var_by_name (lexic, "icase", 0);
+  int replace_nul = get_int_var_by_name (lexic, "rnul", 1);
   tree_cell *retc;
   regex_t re;
   regmatch_t subs[NS];
@@ -712,7 +761,10 @@ nasl_egrep (lex_ctxt *lexic)
     copt = 0;
 
   rets = g_malloc0 (max_size + 2);
-  string = g_strdup (string);
+  if (replace_nul)
+    string = g_regex_escape_nul (string, max_size);
+  else
+    string = g_strdup (string);
 
   s = string;
   while (s[0] == '\n')
@@ -798,6 +850,7 @@ nasl_egrep (lex_ctxt *lexic)
  * - @a string A string
  * - @a icase Boolean, for case sensitve
  * - @a find_all Boolean, to find all matches
+ * - @a rnul replace the null char in the string. Default TRUE.
  *
  * @naslret An array with the first match (find_all: False)
  *          or an array with all matches (find_all: TRUE).
@@ -813,6 +866,8 @@ nasl_eregmatch (lex_ctxt *lexic)
   char *string = get_str_var_by_name (lexic, "string");
   int icase = get_int_var_by_name (lexic, "icase", 0);
   int find_all = get_int_var_by_name (lexic, "find_all", 0);
+  int replace_nul = get_int_var_by_name (lexic, "rnul", 1);
+  int max_size = get_var_size_by_name (lexic, "string");
   int copt = 0;
   tree_cell *retc;
   regex_t re;
@@ -826,6 +881,11 @@ nasl_eregmatch (lex_ctxt *lexic)
   if (pattern == NULL || string == NULL)
     return NULL;
 
+  if (replace_nul)
+    string = g_regex_escape_nul (string, max_size);
+  else
+    string = g_strdup (string);
+
   if (regcomp (&re, pattern, REG_EXTENDED | copt))
     {
       nasl_perror (lexic, "regmatch() : regcomp() failed for pattern '%s'.\n",