MACLookup.cc

/***************************************************************************
 * MACLookup.cc -- This relatively simple system handles looking up the    *
 * vendor registered to a MAC address using the nmap-mac-prefixes          *
 * database.                                                               *
 *                                                                         *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
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 *                                                                         *
 ***************************************************************************/

/* $Id$ */


/* Character pool memory allocation */
#include "MACLookup.h"
#include "nmap.h"
#include "nmap_error.h"

struct MAC_entry {
  int prefix; /* -1 means none set */
  char *vendor;
};

struct MAC_hash_table {
  int table_capacity; /* How many members the table can hold */
  int table_members; /* How many members it has now */
  struct MAC_entry **table;
} MacTable;

static inline int MacCharPrefix2Key(const u8 *prefix) {
  return (prefix[0] << 16) + (prefix[1] << 8) + prefix[2];
}

/* Hashes the prefix into a position from 0 to table_capacity - 1.  Does not
   check if the position is free or anything */
static inline int MACTableHash(int prefix, int table_capacity) {
  // Maybe I should think about changing this sometime.
  return prefix % table_capacity;
}

static void mac_prefix_init() {
  static int initialized = 0;
  if (initialized) return;
  initialized = 1;
  char filename[256];
  FILE *fp;
  char line[128];
  int pfx, pos;
  char *endptr, *p;
  int lineno = 0;
  struct MAC_entry *ME;

  MacTable.table_capacity = 19037;
  MacTable.table_members = 0;
  MacTable.table = (struct MAC_entry **) safe_zalloc(MacTable.table_capacity * sizeof(struct MAC_entry *));

  /* Now it is time to read in all of the entries ... */
  if (nmap_fetchfile(filename, sizeof(filename), "nmap-mac-prefixes") != 1){
    error("Cannot find nmap-mac-prefixes: Ethernet vendor corolation will not be performed");
    return;
  }

  fp = fopen(filename, "r");
  if (!fp) {
    error("Unable to open %s.  Ethernet vendor correlation will not be performed ", filename);
    return;
  }

  while(fgets(line, sizeof(line), fp)) {
    lineno++;
    if (*line == '#') continue;
    if (!isxdigit(*line)) {
      error("Parse error one line #%d of %s. Giving up parsing.", lineno, filename);
      break;
    }
    /* First grab the prefix */
    pfx = strtol(line, &endptr, 16);
    if (!endptr || !isspace(*endptr)) {
      error("Parse error one line #%d of %s. Giving up parsing.", lineno, filename);
      break;
    }
    /* Now grab the vendor */
    while(*endptr && isspace(*endptr)) endptr++;
    assert(*endptr);
    p = endptr;
    while(*endptr && *endptr != '\n' && *endptr != '\r') endptr++;
    *endptr = '\0';

    // Create the new MAC_entry
    ME = (struct MAC_entry *) cp_alloc(sizeof(struct MAC_entry));
    ME->prefix = pfx;
    ME->vendor = cp_strdup(p);

    if (MacTable.table_members > MacTable.table_capacity * 0.8)
      error("WARNING:  nmap-mac-prefixes has grown to more than 80%% of our hash table size.  MacTable.table_capacity should be increased");

    // Now insert it into the table
    if (MacTable.table_members >= MacTable.table_capacity)
      fatal("No space for further MAC prefixes from nmap-mac-prefixes.  Increase MacTable.table_capacity");

    pos = MACTableHash(pfx, MacTable.table_capacity); 
    while (MacTable.table[pos]) pos = (pos + 1) % MacTable.table_capacity;
    MacTable.table[pos] = ME;
    MacTable.table_members++;
  }

  fclose(fp);
  return;
}


static struct MAC_entry *findMACEntry(int prefix) {
  int pos = MACTableHash(prefix, MacTable.table_capacity);

  while (MacTable.table[pos]) {
    if (MacTable.table[pos]->prefix == prefix)
      return MacTable.table[pos];
    pos = (pos + 1) % MacTable.table_capacity;
  }

  return NULL;
}

/* Takes a three byte MAC address prefix (passing the whole MAC is OK
   too) and returns the company which has registered the prefix.
   NULL is returned if no vendor is found for the given prefix or if there
   is some other error. */
const char *MACPrefix2Corp(const u8 *prefix) {
  struct MAC_entry *ent;

  if (!prefix) fatal("MACPrefix2Corp called with a NULL prefix");
  mac_prefix_init();

  ent = findMACEntry(MacCharPrefix2Key(prefix));
  return (ent)? ent->vendor : NULL;
}

/* Takes a string and looks through the table for a vendor name which
   contains that string.  Sets the first three bytes in mac_data and
   returns true for the first matching entry found.  If no entries
   match, leaves mac_data untouched and returns false.  Note that this
   is not particularly efficient and so should be rewriteen if it is
   called often */
bool MACCorp2Prefix(const char *vendorstr, u8 *mac_data) {
  if (!vendorstr) fatal("%s: vendorstr is NULL", __FUNCTION__);
  if (!mac_data) fatal("%s: mac_data is NULL", __FUNCTION__);
  mac_prefix_init();

  for(int i = 0; i < MacTable.table_capacity; i++ ) {
    if (MacTable.table[i])
      if (strcasestr(MacTable.table[i]->vendor, vendorstr)) {
	mac_data[0] = MacTable.table[i]->prefix >> 16;
	mac_data[1] = (MacTable.table[i]->prefix >> 8) & 0xFF;
	mac_data[2] = MacTable.table[i]->prefix & 0xFF;
	return true;
      }
  }
  return false;
}