extensions/libipt_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/ipv4/netfilter/ipt_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 #include <stdio.h>
  11 #include <netdb.h>
  12 #include <string.h>
  13 #include <stdlib.h>
  14 #include <getopt.h>
  15 #include <iptables.h>
  16 #include <linux/netfilter_ipv4/ipt_u32.h>
  17 #include <errno.h>
  18 #include <ctype.h>
  19
  20 /* Function which prints out usage message. */
  21 static void
  22 help(void)
  23 {
  24         printf( "u32 v%s options:\n"
  25                 " --u32 tests\n"
  26                 " tests := location = value | tests && location = value\n"
  27                 " value := range | value , range\n"
  28                 " range := number | number : number\n"
  29                 " location := number | location operator number\n"
  30                 " operator := & | << | >> | @\n"
  31                 ,IPTABLES_VERSION);
  32 }
  33
  34 /* defined in /usr/include/getopt.h maybe in man getopt */
  35 static struct option opts[] = {
  36         { "u32", 1, 0, '1' },
  37         { 0 }
  38 };
  39
  40 /* shared printing code */
  41 static void print_u32(struct ipt_u32 *data)
  42 {
  43         unsigned int testind;
  44
  45         for (testind=0; testind < data->ntests; testind++) {
  46                 if (testind) printf("&&");
  47                 {
  48                         unsigned int i;
  49
  50                         printf("0x%x", data->tests[testind].location[0].number);
  51                         for (i = 1; i < data->tests[testind].nnums; i++) {
  52                                 switch (data->tests[testind].location[i].nextop) {
  53                                 case IPT_U32_AND: printf("&"); break;
  54                                 case IPT_U32_LEFTSH: printf("<<"); break;
  55                                 case IPT_U32_RIGHTSH: printf(">>"); break;
  56                                 case IPT_U32_AT: printf("@"); break;
  57                                 }
  58                                 printf("0x%x", data->tests[testind].location[i].number);
  59                         }
  60                         printf("=");
  61                         for (i = 0; i < data->tests[testind].nvalues; i++) {
  62                                 if (i) printf(",");
  63                                 if (data->tests[testind].value[i].min
  64                                     == data->tests[testind].value[i].max)
  65                                         printf("0x%x", data->tests[testind].value[i].min);
  66                                 else printf("0x%x:0x%x", data->tests[testind].value[i].min,
  67                                             data->tests[testind].value[i].max);
  68                         }
  69                 }
  70         }
  71         printf(" ");
  72 }
  73
  74 /* string_to_number is not quite what we need here ... */
  75 u_int32_t parse_number(char **s, int pos)
  76 {
  77         u_int32_t number;
  78         char *end;
  79         errno = 0;
  80
  81         number = strtoul(*s, &end, 0);
  82         if (end == *s)
  83                 exit_error(PARAMETER_PROBLEM,
  84                            "u32: at char %d expected number", pos);
  85         if (errno)
  86                 exit_error(PARAMETER_PROBLEM,
  87                            "u32: at char %d error reading number", pos);
  88         *s = end;
  89         return number;
  90 }
  91
  92 /* Function which parses command options; returns true if it ate an option */
  93 static int
  94 parse(int c, char **argv, int invert, unsigned int *flags,
  95       const struct ipt_entry *entry,
  96       struct ipt_entry_match **match)
  97 {
  98         struct ipt_u32 *data = (struct ipt_u32 *)(*match)->data;
  99         char *arg = argv[optind-1]; /* the argument string */
 100         char *start = arg;
 101         int state=0, testind=0, locind=0, valind=0;
 102
 103         if (c != '1') return 0;
 104         /* states: 0 = looking for numbers and operations, 1 = looking for ranges */
 105         while (1) { /* read next operand/number or range */
 106                 while (isspace(*arg))
 107                         arg++;  /* skip white space */
 108                 if (! *arg) { /* end of argument found */
 109                         if (state == 0)
 110                                 exit_error(PARAMETER_PROBLEM,
 111                                            "u32: input ended in location spec");
 112                         if (valind == 0)
 113                                 exit_error(PARAMETER_PROBLEM,
 114                                            "u32: test ended with no value spec");
 115                         data->tests[testind].nnums = locind;
 116                         data->tests[testind].nvalues = valind;
 117                         testind++;
 118                         data->ntests=testind;
 119                         if (testind > U32MAXSIZE)
 120                                 exit_error(PARAMETER_PROBLEM,
 121                                            "u32: at char %d too many &&'s",
 122                                            arg-start);
 123                         /* debugging
 124                            print_u32(data);printf("\n");
 125                            exit_error(PARAMETER_PROBLEM, "debugging output done"); */
 126                         return 1;
 127                 }
 128                 if (state == 0) {
 129                         /* reading location: read a number if nothing read yet,
 130                            otherwise either op number or = to end location spec */
 131                         if (*arg == '=') {
 132                                 if (locind == 0)
 133                                         exit_error(PARAMETER_PROBLEM,
 134                                                    "u32: at char %d location spec missing", arg-start);
 135                                 else {
 136                                         arg++;
 137                                         state=1;
 138                                 }
 139                         }
 140                         else {
 141                                 if (locind) { /* need op before number */
 142                                         if (*arg == '&') {
 143                                                 data->tests[testind].location[locind].nextop = IPT_U32_AND;
 144                                         }
 145                                         else if (*arg == '<') {
 146                                                 arg++;
 147                                                 if (*arg != '<')
 148                                                         exit_error(PARAMETER_PROBLEM,
 149                                                                    "u32: at char %d a second < expected", arg-start);
 150                                                 data->tests[testind].location[locind].nextop = IPT_U32_LEFTSH;
 151                                         }
 152                                         else if (*arg == '>') {
 153                                                 arg++;
 154                                                 if (*arg != '>')
 155                                                         exit_error(PARAMETER_PROBLEM,
 156                                                                    "u32: at char %d a second > expected", arg-start);
 157                                                 data->tests[testind].location[locind].nextop = IPT_U32_RIGHTSH;
 158                                         }
 159                                         else if (*arg == '@') {
 160                                                 data->tests[testind].location[locind].nextop = IPT_U32_AT;
 161                                         }
 162                                         else exit_error(PARAMETER_PROBLEM,
 163                                                         "u32: at char %d operator expected", arg-start);
 164                                         arg++;
 165                                 }
 166                                 /* now a number; string_to_number skips white space? */
 167                                 data->tests[testind].location[locind].number =
 168                                         parse_number(&arg, arg-start);
 169                                 locind++;
 170                                 if (locind > U32MAXSIZE)
 171                                         exit_error(PARAMETER_PROBLEM,
 172                                                    "u32: at char %d too many operators", arg-start);
 173                         }
 174                 }
 175                 else {
 176                         /* state 1 - reading values: read a range if nothing read yet,
 177                            otherwise either ,range or && to end test spec */
 178                         if (*arg == '&') {
 179                                 arg++;
 180                                 if (*arg != '&')
 181                                         exit_error(PARAMETER_PROBLEM,
 182                                                    "u32: at char %d a second & expected", arg-start);
 183                                 if (valind == 0)
 184                                         exit_error(PARAMETER_PROBLEM,
 185                                                    "u32: at char %d value spec missing", arg-start);
 186                                 else {
 187                                         data->tests[testind].nnums = locind;
 188                                         data->tests[testind].nvalues = valind;
 189                                         testind++;
 190                                         if (testind > U32MAXSIZE)
 191                                                 exit_error(PARAMETER_PROBLEM,
 192                                                            "u32: at char %d too many &&'s", arg-start);
 193                                         arg++; state=0; locind=0; valind=0;
 194                                 }
 195                         }
 196                         else { /* read value range */
 197                                 if (valind) { /* need , before number */
 198                                         if (*arg != ',')
 199                                                 exit_error(PARAMETER_PROBLEM,
 200                                                            "u32: at char %d expected , or &&", arg-start);
 201                                         arg++;
 202                                 }
 203                                 data->tests[testind].value[valind].min = parse_number(&arg, arg-start);
 204                                 while (isspace(*arg))
 205                                         arg++;  /* another place white space could be */
 206                                 if (*arg==':') {
 207                                         arg++;
 208                                         data->tests[testind].value[valind].max
 209                                                 = parse_number(&arg, arg-start);
 210                                 }
 211                                 else data->tests[testind].value[valind].max
 212                                              = data->tests[testind].value[valind].min;
 213                                 valind++;
 214                                 if (valind > U32MAXSIZE)
 215                                         exit_error(PARAMETER_PROBLEM,
 216                                                    "u32: at char %d too many ,'s", arg-start);
 217                         }
 218                 }
 219         }
 220 }
 221
 222 /* Final check; must specify something. */
 223 static void
 224 final_check(unsigned int flags)
 225 {
 226 }
 227
 228 /* Prints out the matchinfo. */
 229 static void
 230 print(const struct ipt_ip *ip,
 231       const struct ipt_entry_match *match,
 232       int numeric)
 233 {
 234         printf("u32 ");
 235         print_u32((struct ipt_u32 *)match->data);
 236 }
 237
 238 /* Saves the union ipt_matchinfo in parsable form to stdout. */
 239 static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
 240 {
 241         printf("--u32 ");
 242         print_u32((struct ipt_u32 *)match->data);
 243 }
 244
 245 struct iptables_match u32 = {
 246         .next           = NULL,
 247         .name           = "u32",
 248         .version        = IPTABLES_VERSION,
 249         .size           = IPT_ALIGN(sizeof(struct ipt_u32)),
 250         .userspacesize  = IPT_ALIGN(sizeof(struct ipt_u32)),
 251         .help           = &help,
 252         .parse          = &parse,
 253         .final_check    = &final_check,
 254         .print          = &print,
 255         .save           = &save,
 256         .extra_opts     = opts
 257 };
 258
 259 void
 260 _init(void)
 261 {
 262         register_match(&u32);
 263 }