helpers.cpp: introduce safe_strncpy() and use it

Origin commit data
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Branch: ni/coolstream
Commit: 72edb6b46d
Author: GetAway <get-away@t-online.de>
Date: 2019-06-18 (Tue, 18 Jun 2019)


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No further description and justification available within origin commit message!

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This commit was generated by Migit

src/system/helpers.cpp

@@ -402,12 +402,35 @@ int mkdirhier(const char *pathname, mode_t mode)
 }
 # endif
 
+/* This function is a replacement which makes sure that a \0 is always added,
+   cuz standard strncpy does not terminate the string if the source is exactly
+   as long or longer as the specified size. This can raise security issues.
+   num should be the real size of char array (do not subtract -1)
+*/
+void safe_strncpy(char *dest, const char *src, size_t num)
+{
+	if(!src)
+	{
+		dest[0] = '\0';
+		return;
+	}
+
+	uint32_t l, size = strlen(src);
+	if(size > num - 1)
+		l = num - 1;
+	else
+	l = size;
+
+	memcpy(dest, src, l);
+	dest[l] = '\0';
+}
+
 int safe_mkdir(const char * path)
 {
 	struct statfs s;
 	size_t l = strlen(path);
-	char d[l + 3];
-	strncpy(d, path, l);
+	char d[l];
+	safe_strncpy(d, path, l);
 
 	// skip trailing slashes
 	while (l > 0 && d[l - 1] == '/')
@@ -739,7 +762,7 @@ const char *cstr_replace(const char *search, const char *replace, const char *te
 		tmp = strncpy(tmp, replace, len_replace) + len_replace;
 		text += len_front + len_search; // move to next "end of search"
 	}
-	strncpy(tmp, text, strlen(text));
+	safe_strncpy(tmp, text, strlen(text));
 	return result;
 }
 

src/system/helpers.h

@@ -46,6 +46,7 @@ int my_system(int argc, const char *arg, ...); /* argc is number of arguments in
 FILE* my_popen( pid_t& pid, const char *cmdstring, const char *type);
 int run_pty(pid_t &pid, const char *cmdstring);
 
+void safe_strncpy(char *dest, const char *src, size_t num);
 int safe_mkdir(const char * path);
 inline int safe_mkdir(std::string path) { return safe_mkdir(path.c_str()); }
 //int mkdirhier(const char *pathname, mode_t mode = 0755);