added regular expression checking

CMakeLists.txt

@@ -110,6 +110,7 @@ add_library(n2n STATIC
         src/tuntap_netbsd.c
         src/tuntap_linux.c
         src/tuntap_osx.c
+        src/n2n_regex.c
         )
 
 if(DEFINED WIN32)

include/n2n.h

@@ -155,6 +155,7 @@ typedef struct ether_hdr ether_hdr_t;
 #include "pearson.h"
 #include "portable_endian.h"
 #include "speck.h"
+#include "n2n_regex.h"
 
 #ifdef WIN32
 #define N2N_IFNAMSIZ            64
@@ -359,6 +360,13 @@ struct sn_community
   UT_hash_handle hh; /* makes this structure hashable */
 };
 
+struct sn_community_regular_expression
+{
+  re_t rule;         // compiles regular expression
+
+  UT_hash_handle hh; /* makes this structure hashable */
+};
+
 typedef struct n2n_sn
 {
     time_t start_time; /* Used to measure uptime. */
@@ -372,8 +380,9 @@ typedef struct n2n_sn
 	uid_t userid;
 	gid_t groupid;
 #endif
-    int lock_communities; /* If true, only loaded communities can be used. */
+    int lock_communities; /* If true, only loaded and matching communities can be used. */
     struct sn_community *communities;
+    struct sn_community_regular_expression *rules;
 } n2n_sn_t;
 
 /* ************************************** */

include/n2n_regex.h

@@ -0,0 +1,80 @@
+/**
+ * (C) 2007-20 - ntop.org and contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not see see <http://www.gnu.org/licenses/>
+ *
+ */
+
+// taken from https://github.com/kokke/tiny-regex-c
+// under Unlicense as of August 4, 2020
+
+/*
+ *
+ * Mini regex-module inspired by Rob Pike's regex code described in:
+ *
+ * http://www.cs.princeton.edu/courses/archive/spr09/cos333/beautiful.html
+ *
+ *
+ *
+ * Supports:
+ * ---------
+ *   '.'        Dot, matches any character
+ *   '^'        Start anchor, matches beginning of string
+ *   '$'        End anchor, matches end of string
+ *   '*'        Asterisk, match zero or more (greedy)
+ *   '+'        Plus, match one or more (greedy)
+ *   '?'        Question, match zero or one (non-greedy)
+ *   '[abc]'    Character class, match if one of {'a', 'b', 'c'}
+ *   '[^abc]'   Inverted class, match if NOT one of {'a', 'b', 'c'} -- NOTE: feature is currently broken!
+ *   '[a-zA-Z]' Character ranges, the character set of the ranges { a-z | A-Z }
+ *   '\s'       Whitespace, \t \f \r \n \v and spaces
+ *   '\S'       Non-whitespace
+ *   '\w'       Alphanumeric, [a-zA-Z0-9_]
+ *   '\W'       Non-alphanumeric
+ *   '\d'       Digits, [0-9]
+ *   '\D'       Non-digits
+ *
+ *
+ */
+
+#ifndef _N2N_REGEX_
+#define _N2N_REGEX_
+
+#ifdef __cplusplus
+extern "C"{
+#endif
+
+#include <stdio.h>
+
+/* Typedef'd pointer to get abstract datatype. */
+typedef struct regex_t* re_t;
+
+
+/* Compile regex string pattern to a regex_t-array. */
+re_t re_compile(const char* pattern);
+
+
+/* Find matches of the compiled pattern inside text. */
+int  re_matchp(re_t pattern, const char* text, int* matchlenght);
+
+
+/* Find matches of the txt pattern inside text (will compile automatically first). */
+int  re_match(const char* pattern, const char* text, int* matchlenght);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/n2n_regex.c

@@ -0,0 +1,523 @@
+/**
+ * (C) 2007-20 - ntop.org and contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not see see <http://www.gnu.org/licenses/>
+ *
+ */
+
+// taken from https://github.com/kokke/tiny-regex-c
+// under Unlicense as of August 4, 2020
+
+/*
+ *
+ * Mini regex-module inspired by Rob Pike's regex code described in:
+ *
+ * http://www.cs.princeton.edu/courses/archive/spr09/cos333/beautiful.html
+ *
+ *
+ *
+ * Supports:
+ * ---------
+ *   '.'        Dot, matches any character
+ *   '^'        Start anchor, matches beginning of string
+ *   '$'        End anchor, matches end of string
+ *   '*'        Asterisk, match zero or more (greedy)
+ *   '+'        Plus, match one or more (greedy)
+ *   '?'        Question, match zero or one (non-greedy)
+ *   '[abc]'    Character class, match if one of {'a', 'b', 'c'}
+ *   '[^abc]'   Inverted class, match if NOT one of {'a', 'b', 'c'} -- NOTE: feature is currently broken!
+ *   '[a-zA-Z]' Character ranges, the character set of the ranges { a-z | A-Z }
+ *   '\s'       Whitespace, \t \f \r \n \v and spaces
+ *   '\S'       Non-whitespace
+ *   '\w'       Alphanumeric, [a-zA-Z0-9_]
+ *   '\W'       Non-alphanumeric
+ *   '\d'       Digits, [0-9]
+ *   '\D'       Non-digits
+ *
+ *
+ */
+
+
+#include "n2n_regex.h"
+
+/* Definitions: */
+
+#define MAX_REGEXP_OBJECTS      30    /* Max number of regex symbols in expression. */
+#define MAX_CHAR_CLASS_LEN      40    /* Max length of character-class buffer in.   */
+
+
+enum { UNUSED, DOT, BEGIN, END, QUESTIONMARK, STAR, PLUS, CHAR, CHAR_CLASS, INV_CHAR_CLASS, DIGIT, NOT_DIGIT, ALPHA, NOT_ALPHA, WHITESPACE, NOT_WHITESPACE, /* BRANCH */ };
+
+typedef struct regex_t
+{
+  unsigned char  type;   /* CHAR, STAR, etc.                      */
+  union
+  {
+    unsigned char  ch;   /*      the character itself             */
+    unsigned char* ccl;  /*  OR  a pointer to characters in class */
+  };
+} regex_t;
+
+
+
+/* Private function declarations: */
+static int matchpattern(regex_t* pattern, const char* text, int* matchlength);
+static int matchcharclass(char c, const char* str);
+static int matchstar(regex_t p, regex_t* pattern, const char* text, int* matchlength);
+static int matchplus(regex_t p, regex_t* pattern, const char* text, int* matchlength);
+static int matchone(regex_t p, char c);
+static int matchdigit(char c);
+static int matchalpha(char c);
+static int matchwhitespace(char c);
+static int matchmetachar(char c, const char* str);
+static int matchrange(char c, const char* str);
+static int matchdot(char c);
+static int ismetachar(char c);
+
+
+
+/* Public functions: */
+int re_match(const char* pattern, const char* text, int* matchlength)
+{
+  return re_matchp(re_compile(pattern), text, matchlength);
+}
+
+int re_matchp(re_t pattern, const char* text, int* matchlength)
+{
+  *matchlength = 0;
+  if (pattern != 0)
+  {
+    if (pattern[0].type == BEGIN)
+    {
+      return ((matchpattern(&pattern[1], text, matchlength)) ? 0 : -1);
+    }
+    else
+    {
+      int idx = -1;
+
+      do
+      {
+        idx += 1;
+        
+        if (matchpattern(pattern, text, matchlength))
+        {
+          if (text[0] == '\0')
+            return -1;
+        
+          return idx;
+        }
+      }
+      while (*text++ != '\0');
+    }
+  }
+  return -1;
+}
+
+re_t re_compile(const char* pattern)
+{
+  /* The sizes of the two static arrays below substantiates the static RAM usage of this module.
+     MAX_REGEXP_OBJECTS is the max number of symbols in the expression.
+     MAX_CHAR_CLASS_LEN determines the size of buffer for chars in all char-classes in the expression. */
+  static regex_t re_compiled[MAX_REGEXP_OBJECTS];
+  static unsigned char ccl_buf[MAX_CHAR_CLASS_LEN];
+  int ccl_bufidx = 1;
+
+  char c;     /* current char in pattern   */
+  int i = 0;  /* index into pattern        */
+  int j = 0;  /* index into re_compiled    */
+
+  while (pattern[i] != '\0' && (j+1 < MAX_REGEXP_OBJECTS))
+  {
+    c = pattern[i];
+
+    switch (c)
+    {
+      /* Meta-characters: */
+      case '^': {    re_compiled[j].type = BEGIN;           } break;
+      case '$': {    re_compiled[j].type = END;             } break;
+      case '.': {    re_compiled[j].type = DOT;             } break;
+      case '*': {    re_compiled[j].type = STAR;            } break;
+      case '+': {    re_compiled[j].type = PLUS;            } break;
+      case '?': {    re_compiled[j].type = QUESTIONMARK;    } break;
+/*    case '|': {    re_compiled[j].type = BRANCH;          } break; <-- not working properly */
+
+      /* Escaped character-classes (\s \w ...): */
+      case '\\':
+      {
+        if (pattern[i+1] != '\0')
+        {
+          /* Skip the escape-char '\\' */
+          i += 1;
+          /* ... and check the next */
+          switch (pattern[i])
+          {
+            /* Meta-character: */
+            case 'd': {    re_compiled[j].type = DIGIT;            } break;
+            case 'D': {    re_compiled[j].type = NOT_DIGIT;        } break;
+            case 'w': {    re_compiled[j].type = ALPHA;            } break;
+            case 'W': {    re_compiled[j].type = NOT_ALPHA;        } break;
+            case 's': {    re_compiled[j].type = WHITESPACE;       } break;
+            case 'S': {    re_compiled[j].type = NOT_WHITESPACE;   } break;
+
+            /* Escaped character, e.g. '.' or '$' */ 
+            default:  
+            {
+              re_compiled[j].type = CHAR;
+              re_compiled[j].ch = pattern[i];
+            } break;
+          }
+        }
+        /* '\\' as last char in pattern -> invalid regular expression. */
+/*
+        else
+        { 
+          re_compiled[j].type = CHAR;
+          re_compiled[j].ch = pattern[i];
+        }
+*/
+      } break;
+
+      /* Character class: */
+      case '[':
+      {
+        /* Remember where the char-buffer starts. */
+        int buf_begin = ccl_bufidx;
+
+        /* Look-ahead to determine if negated */
+        if (pattern[i+1] == '^')
+        {
+          re_compiled[j].type = INV_CHAR_CLASS;
+          i += 1; /* Increment i to avoid including '^' in the char-buffer */
+        }  
+        else
+        {
+          re_compiled[j].type = CHAR_CLASS;
+        }
+
+        /* Copy characters inside [..] to buffer */
+        while (    (pattern[++i] != ']')
+                && (pattern[i]   != '\0')) /* Missing ] */
+        {
+          if (pattern[i] == '\\')
+          {
+            if (ccl_bufidx >= MAX_CHAR_CLASS_LEN - 1)
+            {
+              //fputs("exceeded internal buffer!\n", stderr);
+              return 0;
+            }
+            ccl_buf[ccl_bufidx++] = pattern[i++];
+          }
+          else if (ccl_bufidx >= MAX_CHAR_CLASS_LEN)
+          {
+              //fputs("exceeded internal buffer!\n", stderr);
+              return 0;
+          }
+          ccl_buf[ccl_bufidx++] = pattern[i];
+        }
+        if (ccl_bufidx >= MAX_CHAR_CLASS_LEN)
+        {
+            /* Catches cases such as [00000000000000000000000000000000000000][ */
+            //fputs("exceeded internal buffer!\n", stderr);
+            return 0;
+        }
+        /* Null-terminate string end */
+        ccl_buf[ccl_bufidx++] = 0;
+        re_compiled[j].ccl = &ccl_buf[buf_begin];
+      } break;
+
+      /* Other characters: */
+      default:
+      {
+        re_compiled[j].type = CHAR;
+        re_compiled[j].ch = c;
+      } break;
+    }
+    i += 1;
+    j += 1;
+  }
+  /* 'UNUSED' is a sentinel used to indicate end-of-pattern */
+  re_compiled[j].type = UNUSED;
+
+  return (re_t) re_compiled;
+}
+
+void re_print(regex_t* pattern)
+{
+  const char* types[] = { "UNUSED", "DOT", "BEGIN", "END", "QUESTIONMARK", "STAR", "PLUS", "CHAR", "CHAR_CLASS", "INV_CHAR_CLASS", "DIGIT", "NOT_DIGIT", "ALPHA", "NOT_ALPHA", "WHITESPACE", "NOT_WHITESPACE", "BRANCH" };
+
+  int i;
+  int j;
+  char c;
+  for (i = 0; i < MAX_REGEXP_OBJECTS; ++i)
+  {
+    if (pattern[i].type == UNUSED)
+    {
+      break;
+    }
+
+    printf("type: %s", types[pattern[i].type]);
+    if (pattern[i].type == CHAR_CLASS || pattern[i].type == INV_CHAR_CLASS)
+    {
+      printf(" [");
+      for (j = 0; j < MAX_CHAR_CLASS_LEN; ++j)
+      {
+        c = pattern[i].ccl[j];
+        if ((c == '\0') || (c == ']'))
+        {
+          break;
+        }
+        printf("%c", c);
+      }
+      printf("]");
+    }
+    else if (pattern[i].type == CHAR)
+    {
+      printf(" '%c'", pattern[i].ch);
+    }
+    printf("\n");
+  }
+}
+
+
+
+/* Private functions: */
+static int matchdigit(char c)
+{
+  return ((c >= '0') && (c <= '9'));
+}
+static int matchalpha(char c)
+{
+  return ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z'));
+}
+static int matchwhitespace(char c)
+{
+  return ((c == ' ') || (c == '\t') || (c == '\n') || (c == '\r') || (c == '\f') || (c == '\v'));
+}
+static int matchalphanum(char c)
+{
+  return ((c == '_') || matchalpha(c) || matchdigit(c));
+}
+static int matchrange(char c, const char* str)
+{
+  return ((c != '-') && (str[0] != '\0') && (str[0] != '-') &&
+         (str[1] == '-') && (str[1] != '\0') &&
+         (str[2] != '\0') && ((c >= str[0]) && (c <= str[2])));
+}
+static int matchdot(char c)
+{
+  return c != '\n' && c != '\r';
+}
+static int ismetachar(char c)
+{
+  return ((c == 's') || (c == 'S') || (c == 'w') || (c == 'W') || (c == 'd') || (c == 'D'));
+}
+
+static int matchmetachar(char c, const char* str)
+{
+  switch (str[0])
+  {
+    case 'd': return  matchdigit(c);
+    case 'D': return !matchdigit(c);
+    case 'w': return  matchalphanum(c);
+    case 'W': return !matchalphanum(c);
+    case 's': return  matchwhitespace(c);
+    case 'S': return !matchwhitespace(c);
+    default:  return (c == str[0]);
+  }
+}
+
+static int matchcharclass(char c, const char* str)
+{
+  do
+  {
+    if (matchrange(c, str))
+    {
+      return 1;
+    }
+    else if (str[0] == '\\')
+    {
+      /* Escape-char: increment str-ptr and match on next char */
+      str += 1;
+      if (matchmetachar(c, str))
+      {
+        return 1;
+      } 
+      else if ((c == str[0]) && !ismetachar(c))
+      {
+        return 1;
+      }
+    }
+    else if (c == str[0])
+    {
+      if (c == '-')
+      {
+        return ((str[-1] == '\0') || (str[1] == '\0'));
+      }
+      else
+      {
+        return 1;
+      }
+    }
+  }
+  while (*str++ != '\0');
+
+  return 0;
+}
+
+static int matchone(regex_t p, char c)
+{
+  switch (p.type)
+  {
+    case DOT:            return matchdot(c);
+    case CHAR_CLASS:     return  matchcharclass(c, (const char*)p.ccl);
+    case INV_CHAR_CLASS: return !matchcharclass(c, (const char*)p.ccl);
+    case DIGIT:          return  matchdigit(c);
+    case NOT_DIGIT:      return !matchdigit(c);
+    case ALPHA:          return  matchalphanum(c);
+    case NOT_ALPHA:      return !matchalphanum(c);
+    case WHITESPACE:     return  matchwhitespace(c);
+    case NOT_WHITESPACE: return !matchwhitespace(c);
+    default:             return  (p.ch == c);
+  }
+}
+
+static int matchstar(regex_t p, regex_t* pattern, const char* text, int* matchlength)
+{
+  int prelen = *matchlength;
+  const char* prepoint = text;
+  while ((text[0] != '\0') && matchone(p, *text))
+  {
+    text++;
+    (*matchlength)++;
+  }
+  while (text >= prepoint)
+  {
+    if (matchpattern(pattern, text--, matchlength))
+      return 1;
+    (*matchlength)--;
+  }
+  
+  *matchlength = prelen;
+  return 0;
+}
+
+static int matchplus(regex_t p, regex_t* pattern, const char* text, int* matchlength)
+{
+  const char* prepoint = text;
+  while ((text[0] != '\0') && matchone(p, *text))
+  {
+    text++;
+    (*matchlength)++;
+  }
+  while (text > prepoint)
+  {
+    if (matchpattern(pattern, text--, matchlength))
+      return 1;
+    (*matchlength)--;
+  }
+  
+  return 0;
+}
+
+static int matchquestion(regex_t p, regex_t* pattern, const char* text, int* matchlength)
+{
+  if (p.type == UNUSED)
+    return 1;
+  if (matchpattern(pattern, text, matchlength))
+      return 1;
+  if (*text && matchone(p, *text++))
+  {
+    if (matchpattern(pattern, text, matchlength))
+    {
+      (*matchlength)++;
+      return 1;
+    }
+  }
+  return 0;
+}
+
+
+#if 0
+
+/* Recursive matching */
+static int matchpattern(regex_t* pattern, const char* text, int *matchlength)
+{
+  int pre = *matchlength;
+  if ((pattern[0].type == UNUSED) || (pattern[1].type == QUESTIONMARK))
+  {
+    return matchquestion(pattern[1], &pattern[2], text, matchlength);
+  }
+  else if (pattern[1].type == STAR)
+  {
+    return matchstar(pattern[0], &pattern[2], text, matchlength);
+  }
+  else if (pattern[1].type == PLUS)
+  {
+    return matchplus(pattern[0], &pattern[2], text, matchlength);
+  }
+  else if ((pattern[0].type == END) && pattern[1].type == UNUSED)
+  {
+    return text[0] == '\0';
+  }
+  else if ((text[0] != '\0') && matchone(pattern[0], text[0]))
+  {
+    (*matchlength)++;
+    return matchpattern(&pattern[1], text+1);
+  }
+  else
+  {
+    *matchlength = pre;
+    return 0;
+  }
+}
+
+#else
+
+/* Iterative matching */
+static int matchpattern(regex_t* pattern, const char* text, int* matchlength)
+{
+  int pre = *matchlength;
+  do
+  {
+    if ((pattern[0].type == UNUSED) || (pattern[1].type == QUESTIONMARK))
+    {
+      return matchquestion(pattern[0], &pattern[2], text, matchlength);
+    }
+    else if (pattern[1].type == STAR)
+    {
+      return matchstar(pattern[0], &pattern[2], text, matchlength);
+    }
+    else if (pattern[1].type == PLUS)
+    {
+      return matchplus(pattern[0], &pattern[2], text, matchlength);
+    }
+    else if ((pattern[0].type == END) && pattern[1].type == UNUSED)
+    {
+      return (text[0] == '\0');
+    }
+/*  Branching is not working properly
+    else if (pattern[1].type == BRANCH)
+    {
+      return (matchpattern(pattern, text) || matchpattern(&pattern[2], text));
+    }
+*/
+  (*matchlength)++;
+  }
+  while ((text[0] != '\0') && matchone(*pattern++, *text++));
+
+  *matchlength = pre;
+  return 0;
+}
+
+#endif

src/sn.c

@@ -30,6 +30,7 @@ static int load_allowed_sn_community(n2n_sn_t *sss, char *path) {
   char buffer[4096], *line;
   FILE *fd = fopen(path, "r");
   struct sn_community *s, *tmp;
+  struct sn_community_regular_expression *re, *tmp_re;
   uint32_t num_communities = 0;
 
   if(fd == NULL) {
@@ -44,13 +45,17 @@ static int load_allowed_sn_community(n2n_sn_t *sss, char *path) {
     free(s);
   }
 
+  HASH_ITER(hh, sss->rules, re, tmp_re) {
+    HASH_DEL(sss->rules, re);
+    free(re);
+  }
+
   while((line = fgets(buffer, sizeof(buffer), fd)) != NULL) {
     int len = strlen(line);
 
     if((len < 2) || line[0] == '#')
       continue;
-// !!! if (isregexp) then add to regExp list [check this using a "meta"-regExp]
+
-// !!! otherwise (fixed name) do the following
     len--;
     while(len > 0) {
       if((line[len] == '\n') || (line[len] == '\r')) {
@@ -60,6 +65,18 @@ static int load_allowed_sn_community(n2n_sn_t *sss, char *path) {
 	break;
     }
 
+    // if it contains typical characters...
+    if(NULL != strpbrk(line, ".^$*+?[]\\")) {
+      // ...it is treated as regular expression
+      re = (struct sn_community_regular_expression*)calloc(1,sizeof(struct sn_community_regular_expression));
+      if (re) {
+        re->rule = re_compile(line);
+        HASH_ADD_PTR(sss->rules, rule, re);
+        traceEvent(TRACE_INFO, "Added regular expression for allowed communities '%s'", line);
+        continue;
+      }
+    }
+
     s = (struct sn_community*)calloc(1,sizeof(struct sn_community));
 
     if(s != NULL) {
@@ -81,7 +98,7 @@ static int load_allowed_sn_community(n2n_sn_t *sss, char *path) {
 
   fclose(fd);
 
-  traceEvent(TRACE_NORMAL, "Loaded %u communities from %s",
+  traceEvent(TRACE_NORMAL, "Loaded %u fixed-name communities from %s",
 	     num_communities, path);
 
   /* No new communities will be allowed */

src/sn_utils.c

@@ -791,7 +791,9 @@ static int process_udp(n2n_sn_t * sss,
     n2n_common_t                    cmn2;
     uint8_t                         ackbuf[N2N_SN_PKTBUF_SIZE];
     size_t                          encx=0;
-
+    struct sn_community_regular_expression *re, *tmp_re;
+    int8_t                         allowed_match = -1;
+    int				   match_length = 0;
     /* Edge requesting registration with us.  */
     sss->stats.last_reg_super=now;
     ++(sss->stats.reg_super);
@@ -812,9 +814,14 @@ static int process_udp(n2n_sn_t * sss,
       not report any message back to the edge to hide the supernode
       existance (better from the security standpoint)
     */
-// !!! check if the requested name matches any of the regExps (ITERate)
+
-// !!! put result in variable uint8_t (or so) "allowed_match"
+    HASH_ITER(hh, sss->rules, re, tmp_re) {
-    if(!comm && (!sss->lock_communities || allowed_match)) {
+      allowed_match = re_matchp(re->rule, cmn.community, &match_length);
+      if(allowed_match != -1)
+        break;
+    }
+
+    if(!comm && (!sss->lock_communities || (allowed_match != -1))) {
       comm = calloc(1, sizeof(struct sn_community));
 
       if(comm) {