src/bpfc.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2011 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,
   5  * Swiss federal institute of technology (ETH Zurich)
   6  * Subject to the GPL, version 2.
   7  *
   8  * This is a tiny Berkeley Packet Filter compiler that understands the
   9  * Syntax / Semantic from the USENIX paper {"The BSD Packet Filter: A New
  10  * Architecture for User-level Packet Capture", McCanne, Steven and
  11  * Jacobson, Van, Lawrence Berkeley Laboratory}. With this, BPFs can be
  12  * written the good old way and understood by the Linux kernel and *BSD
  13  * kernels where Berkeley Packet Filters are used.
  14  *
  15  *   The one small garden of a free gardener was all his need and due, not
  16  *   a garden swollen to a realm; his own hands to use, not the hands of
  17  *   others to command.
  18  *
  19  *     -- The Lord of the Rings, Sam, Chapter 'The Tower of Cirith Ungol'.
  20  */
  21
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <getopt.h>
  25 #include <ctype.h>
  26 #include <unistd.h>
  27 #include <sys/fsuid.h>
  28
  29 #include "xmalloc.h"
  30 #include "xutils.h"
  31 #include "die.h"
  32 #include "bpf.h"
  33
  34 static const char *short_options = "vhi:VdbHLg";
  35 static const struct option long_options[] = {
  36         {"input",       required_argument,      NULL, 'i'},
  37         {"verbose",     no_argument,            NULL, 'V'},
  38         {"hla",         no_argument,            NULL, 'H'},
  39         {"lla",         no_argument,            NULL, 'L'},
  40         {"hla-debug",   no_argument,            NULL, 'g'},
  41         {"bypass",      no_argument,            NULL, 'b'},
  42         {"dump",        no_argument,            NULL, 'd'},
  43         {"version",     no_argument,            NULL, 'v'},
  44         {"help",        no_argument,            NULL, 'h'},
  45         {NULL, 0, NULL, 0}
  46 };
  47
  48 extern int compile_filter(char *file, int verbose, int bypass);
  49 extern int compile_hla_filter(char *file, int verbose, int debug);
  50
  51 static void help(void)
  52 {
  53         printf("\nbpfc %s, a tiny BPF compiler\n", VERSION_STRING);
  54         puts("http://www.netsniff-ng.org\n\n"
  55              "Usage: bpfc [options] || bpfc <program>\n"
  56              "Options:\n"
  57              "  -i|--input <program/-> Berkeley Packet Filter file/stdin\n"
  58              "  -H|--hla               Compile high-level BPF\n"
  59              "  -L|--lla               Compile low-level BPF\n"
  60              "  -V|--verbose           Be more verbose\n"
  61              "  -b|--bypass            Bypass filter validation (e.g. for bug testing)\n"
  62              "  -g|--hla-debug         Print BPF expressions to stdout\n"
  63              "  -d|--dump              Dump supported instruction table\n"
  64              "  -v|--version           Print version\n"
  65              "  -h|--help              Print this help\n\n"
  66              "Examples:\n"
  67              "  bpfc -Hi fubar\n"
  68              "  bpfc -Hgi fubar\n"
  69              "  bpfc -Li fubar\n"
  70              "  bpfc -Lbi fubar\n"
  71              "  bpfc -Li -    (read from stdin)\n\n"
  72              "Please report bugs to <bugs@netsniff-ng.org>\n"
  73              "Copyright (C) 2011-2012 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
  74              "Swiss federal institute of technology (ETH Zurich)\n"
  75              "License: GNU GPL version 2.0\n"
  76              "This is free software: you are free to change and redistribute it.\n"
  77              "There is NO WARRANTY, to the extent permitted by law.\n");
  78         die();
  79 }
  80
  81 static void version(void)
  82 {
  83         printf("\nbpfc %s, a tiny BPF compiler\n", VERSION_STRING);
  84         puts("http://www.netsniff-ng.org\n\n"
  85              "Please report bugs to <bugs@netsniff-ng.org>\n"
  86              "Copyright (C) 2011-2012 Daniel Borkmann <dborkma@tik.ee.ethz.ch>,\n"
  87              "Swiss federal institute of technology (ETH Zurich)\n"
  88              "License: GNU GPL version 2.0\n"
  89              "This is free software: you are free to change and redistribute it.\n"
  90              "There is NO WARRANTY, to the extent permitted by law.\n");
  91         die();
  92 }
  93
  94 int main(int argc, char **argv)
  95 {
  96         int ret, verbose = 0, c, opt_index, bypass = 0, hla = 0, debug = 0;
  97         char *file = NULL;
  98
  99         setfsuid(getuid());
 100         setfsgid(getgid());
 101
 102         if (argc == 1)
 103                 help();
 104
 105         while ((c = getopt_long(argc, argv, short_options,
 106                                 long_options, &opt_index)) != EOF) {
 107                 switch (c) {
 108                 case 'h':
 109                         help();
 110                         break;
 111                 case 'v':
 112                         version();
 113                         break;
 114                 case 'H':
 115                         hla = 1;
 116                         break;
 117                 case 'L':
 118                         hla = 0;
 119                         break;
 120                 case 'g':
 121                         debug = 1;
 122                         break;
 123                 case 'V':
 124                         verbose = 1;
 125                         break;
 126                 case 'b':
 127                         bypass = 1;
 128                         break;
 129                 case 'd':
 130                         bpf_dump_op_table();
 131                         die();
 132                 case 'i':
 133                         file = xstrdup(optarg);
 134                         break;
 135                 case '?':
 136                         switch (optopt) {
 137                         case 'i':
 138                                 panic("Option -%c requires an argument!\n",
 139                                       optopt);
 140                         default:
 141                                 if (isprint(optopt))
 142                                         whine("Unknown option character "
 143                                               "`0x%X\'!\n", optopt);
 144                                 die();
 145                         }
 146                 default:
 147                         break;
 148                 }
 149         }
 150         if (argc == 2)
 151                 file = xstrdup(argv[1]);
 152
 153         if (!file)
 154                 panic("No Berkeley Packet Filter program specified!\n");
 155
 156         if (hla) {
 157                 ret = compile_hla_filter(file, verbose, debug);
 158                 if (!ret) {
 159                         char file_tmp[128];
 160
 161                         slprintf(file_tmp, sizeof(file_tmp), ".%s", file);
 162                         ret = compile_filter(file_tmp, verbose, bypass);
 163                         unlink(file_tmp);
 164                 }
 165         } else {
 166                 ret = compile_filter(file, verbose, bypass);
 167         }
 168
 169         xfree(file);
 170         return ret;
 171 }