extensions/libxt_u32.c

   1 /* Shared library add-on to iptables to add u32 matching,
   2  * generalized matching on values found at packet offsets
   3  *
   4  * Detailed doc is in the kernel module source
   5  * net/netfilter/xt_u32.c
   6  *
   7  * (C) 2002 by Don Cohen <don-netf@isis.cs3-inc.com>
   8  * Released under the terms of GNU GPL v2
   9  *
  10  * Copyright © CC Computer Consultants GmbH, 2007
  11  * Contact: <jengelh@computergmbh.de>
  12  */
  13 #include <sys/types.h>
  14 #include <ctype.h>
  15 #include <errno.h>
  16 #include <getopt.h>
  17 #include <netdb.h>
  18 #include <stdlib.h>
  19 #include <stdio.h>
  20 #include <string.h>
  21
  22 #include <xtables.h>
  23 #include <linux/netfilter/xt_u32.h>
  24
  25 static const struct option u32_opts[] = {
  26         {"u32", 1, NULL, 'u'},
  27         { .name = NULL }
  28 };
  29
  30 static void u32_help(void)
  31 {
  32         printf(
  33                 "u32 match options:\n"
  34                 "[!] --u32 tests\n"
  35                 "\t\t""tests := location \"=\" value | tests \"&&\" location \"=\" value\n"
  36                 "\t\t""value := range | value \",\" range\n"
  37                 "\t\t""range := number | number \":\" number\n"
  38                 "\t\t""location := number | location operator number\n"
  39                 "\t\t""operator := \"&\" | \"<<\" | \">>\" | \"@\"\n");
  40 }
  41
  42 static void u32_dump(const struct xt_u32 *data)
  43 {
  44         const struct xt_u32_test *ct;
  45         unsigned int testind, i;
  46
  47         for (testind = 0; testind < data->ntests; ++testind) {
  48                 ct = &data->tests[testind];
  49
  50                 if (testind > 0)
  51                         printf("&&");
  52
  53                 printf("0x%x", ct->location[0].number);
  54                 for (i = 1; i < ct->nnums; ++i) {
  55                         switch (ct->location[i].nextop) {
  56                         case XT_U32_AND:
  57                                 printf("&");
  58                                 break;
  59                         case XT_U32_LEFTSH:
  60                                 printf("<<");
  61                                 break;
  62                         case XT_U32_RIGHTSH:
  63                                 printf(">>");
  64                                 break;
  65                         case XT_U32_AT:
  66                                 printf("@");
  67                                 break;
  68                         }
  69                         printf("0x%x", ct->location[i].number);
  70                 }
  71
  72                 printf("=");
  73                 for (i = 0; i < ct->nvalues; ++i) {
  74                         if (i > 0)
  75                                 printf(",");
  76                         if (ct->value[i].min == ct->value[i].max)
  77                                 printf("0x%x", ct->value[i].min);
  78                         else
  79                                 printf("0x%x:0x%x", ct->value[i].min,
  80                                        ct->value[i].max);
  81                 }
  82         }
  83         printf(" ");
  84 }
  85
  86 /* string_to_number() is not quite what we need here ... */
  87 static u_int32_t parse_number(char **s, int pos)
  88 {
  89         u_int32_t number;
  90         char *end;
  91
  92         errno  = 0;
  93         number = strtoul(*s, &end, 0);
  94         if (end == *s)
  95                 xtables_error(PARAMETER_PROBLEM,
  96                            "u32: at char %d: expected number", pos);
  97         if (errno != 0)
  98                 xtables_error(PARAMETER_PROBLEM,
  99                            "u32: at char %d: error reading number", pos);
 100         *s = end;
 101         return number;
 102 }
 103
 104 static int u32_parse(int c, char **argv, int invert, unsigned int *flags,
 105                      const void *entry, struct xt_entry_match **match)
 106 {
 107         struct xt_u32 *data = (void *)(*match)->data;
 108         unsigned int testind = 0, locind = 0, valind = 0;
 109         struct xt_u32_test *ct = &data->tests[testind]; /* current test */
 110         char *arg = optarg; /* the argument string */
 111         char *start = arg;
 112         int state = 0;
 113
 114         if (c != 'u')
 115                 return 0;
 116
 117         data->invert = invert;
 118
 119         /*
 120          * states:
 121          * 0 = looking for numbers and operations,
 122          * 1 = looking for ranges
 123          */
 124         while (1) {
 125                 /* read next operand/number or range */
 126                 while (isspace(*arg))
 127                         ++arg;
 128
 129                 if (*arg == '\0') {
 130                         /* end of argument found */
 131                         if (state == 0)
 132                                 xtables_error(PARAMETER_PROBLEM,
 133                                            "u32: abrupt end of input after location specifier");
 134                         if (valind == 0)
 135                                 xtables_error(PARAMETER_PROBLEM,
 136                                            "u32: test ended with no value specified");
 137
 138                         ct->nnums    = locind;
 139                         ct->nvalues  = valind;
 140                         data->ntests = ++testind;
 141
 142                         if (testind > XT_U32_MAXSIZE)
 143                                 xtables_error(PARAMETER_PROBLEM,
 144                                            "u32: at char %u: too many \"&&\"s",
 145                                            (unsigned int)(arg - start));
 146                         return 1;
 147                 }
 148
 149                 if (state == 0) {
 150                         /*
 151                          * reading location: read a number if nothing read yet,
 152                          * otherwise either op number or = to end location spec
 153                          */
 154                         if (*arg == '=') {
 155                                 if (locind == 0) {
 156                                         xtables_error(PARAMETER_PROBLEM,
 157                                                    "u32: at char %u: "
 158                                                    "location spec missing",
 159                                                    (unsigned int)(arg - start));
 160                                 } else {
 161                                         ++arg;
 162                                         state = 1;
 163                                 }
 164                         } else {
 165                                 if (locind != 0) {
 166                                         /* need op before number */
 167                                         if (*arg == '&') {
 168                                                 ct->location[locind].nextop = XT_U32_AND;
 169                                         } else if (*arg == '<') {
 170                                                 if (*++arg != '<')
 171                                                         xtables_error(PARAMETER_PROBLEM,
 172                                                                    "u32: at char %u: a second '<' was expected", (unsigned int)(arg - start));
 173                                                 ct->location[locind].nextop = XT_U32_LEFTSH;
 174                                         } else if (*arg == '>') {
 175                                                 if (*++arg != '>')
 176                                                         xtables_error(PARAMETER_PROBLEM,
 177                                                                    "u32: at char %u: a second '>' was expected", (unsigned int)(arg - start));
 178                                                 ct->location[locind].nextop = XT_U32_RIGHTSH;
 179                                         } else if (*arg == '@') {
 180                                                 ct->location[locind].nextop = XT_U32_AT;
 181                                         } else {
 182                                                 xtables_error(PARAMETER_PROBLEM,
 183                                                         "u32: at char %u: operator expected", (unsigned int)(arg - start));
 184                                         }
 185                                         ++arg;
 186                                 }
 187                                 /* now a number; string_to_number skips white space? */
 188                                 ct->location[locind].number =
 189                                         parse_number(&arg, arg - start);
 190                                 if (++locind > XT_U32_MAXSIZE)
 191                                         xtables_error(PARAMETER_PROBLEM,
 192                                                    "u32: at char %u: too many operators", (unsigned int)(arg - start));
 193                         }
 194                 } else {
 195                         /*
 196                          * state 1 - reading values: read a range if nothing
 197                          * read yet, otherwise either ,range or && to end
 198                          * test spec
 199                          */
 200                         if (*arg == '&') {
 201                                 if (*++arg != '&')
 202                                         xtables_error(PARAMETER_PROBLEM,
 203                                                    "u32: at char %u: a second '&' was expected", (unsigned int)(arg - start));
 204                                 if (valind == 0) {
 205                                         xtables_error(PARAMETER_PROBLEM,
 206                                                    "u32: at char %u: value spec missing", (unsigned int)(arg - start));
 207                                 } else {
 208                                         ct->nnums   = locind;
 209                                         ct->nvalues = valind;
 210                                         ct = &data->tests[++testind];
 211                                         if (testind > XT_U32_MAXSIZE)
 212                                                 xtables_error(PARAMETER_PROBLEM,
 213                                                            "u32: at char %u: too many \"&&\"s", (unsigned int)(arg - start));
 214                                         ++arg;
 215                                         state  = 0;
 216                                         locind = 0;
 217                                         valind = 0;
 218                                 }
 219                         } else { /* read value range */
 220                                 if (valind > 0) { /* need , before number */
 221                                         if (*arg != ',')
 222                                                 xtables_error(PARAMETER_PROBLEM,
 223                                                            "u32: at char %u: expected \",\" or \"&&\"", (unsigned int)(arg - start));
 224                                         ++arg;
 225                                 }
 226                                 ct->value[valind].min =
 227                                         parse_number(&arg, arg - start);
 228
 229                                 while (isspace(*arg))
 230                                         ++arg;
 231
 232                                 if (*arg == ':') {
 233                                         ++arg;
 234                                         ct->value[valind].max =
 235                                                 parse_number(&arg, arg-start);
 236                                 } else {
 237                                         ct->value[valind].max =
 238                                                 ct->value[valind].min;
 239                                 }
 240
 241                                 if (++valind > XT_U32_MAXSIZE)
 242                                         xtables_error(PARAMETER_PROBLEM,
 243                                                    "u32: at char %u: too many \",\"s", (unsigned int)(arg - start));
 244                         }
 245                 }
 246         }
 247 }
 248
 249 static void u32_print(const void *ip, const struct xt_entry_match *match,
 250                       int numeric)
 251 {
 252         const struct xt_u32 *data = (const void *)match->data;
 253         printf("u32 ");
 254         if (data->invert)
 255                 printf("! ");
 256         u32_dump(data);
 257 }
 258
 259 static void u32_save(const void *ip, const struct xt_entry_match *match)
 260 {
 261         const struct xt_u32 *data = (const void *)match->data;
 262         if (data->invert)
 263                 printf("! ");
 264         printf("--u32 ");
 265         u32_dump(data);
 266 }
 267
 268 static struct xtables_match u32_match = {
 269         .name          = "u32",
 270         .family        = NFPROTO_UNSPEC,
 271         .version       = XTABLES_VERSION,
 272         .size          = XT_ALIGN(sizeof(struct xt_u32)),
 273         .userspacesize = XT_ALIGN(sizeof(struct xt_u32)),
 274         .help          = u32_help,
 275         .parse         = u32_parse,
 276         .print         = u32_print,
 277         .save          = u32_save,
 278         .extra_opts    = u32_opts,
 279 };
 280
 281 void _init(void)
 282 {
 283         xtables_register_match(&u32_match);
 284 }