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 (at) isis.cs3-inc.com> 8 * Released under the terms of GNU GPL v2 9 * 10 * Copyright CC Computer Consultants GmbH, 2007 11 * Contact: <jengelh (at) computergmbh.de> 12 */ 13 #include <ctype.h> 14 #include <errno.h> 15 #include <stdint.h> 16 #include <stdlib.h> 17 #include <stdio.h> 18 #include <xtables.h> 19 #include <linux/netfilter/xt_u32.h> 20 21 enum { 22 O_U32 = 0, 23 }; 24 25 static const struct xt_option_entry u32_opts[] = { 26 {.name = "u32", .id = O_U32, .type = XTTYPE_STRING, 27 .flags = XTOPT_MAND | XTOPT_INVERT}, 28 XTOPT_TABLEEND, 29 }; 30 31 static void u32_help(void) 32 { 33 printf( 34 "u32 match options:\n" 35 "[!] --u32 tests\n" 36 "\t\t""tests := location \"=\" value | tests \"&&\" location \"=\" value\n" 37 "\t\t""value := range | value \",\" range\n" 38 "\t\t""range := number | number \":\" number\n" 39 "\t\t""location := number | location operator number\n" 40 "\t\t""operator := \"&\" | \"<<\" | \">>\" | \"@\"\n"); 41 } 42 43 static void u32_dump(const struct xt_u32 *data) 44 { 45 const struct xt_u32_test *ct; 46 unsigned int testind, i; 47 48 printf(" \""); 49 for (testind = 0; testind < data->ntests; ++testind) { 50 ct = &data->tests[testind]; 51 52 if (testind > 0) 53 printf("&&"); 54 55 printf("0x%x", ct->location[0].number); 56 for (i = 1; i < ct->nnums; ++i) { 57 switch (ct->location[i].nextop) { 58 case XT_U32_AND: 59 printf("&"); 60 break; 61 case XT_U32_LEFTSH: 62 printf("<<"); 63 break; 64 case XT_U32_RIGHTSH: 65 printf(">>"); 66 break; 67 case XT_U32_AT: 68 printf("@"); 69 break; 70 } 71 printf("0x%x", ct->location[i].number); 72 } 73 74 printf("="); 75 for (i = 0; i < ct->nvalues; ++i) { 76 if (i > 0) 77 printf(","); 78 if (ct->value[i].min == ct->value[i].max) 79 printf("0x%x", ct->value[i].min); 80 else 81 printf("0x%x:0x%x", ct->value[i].min, 82 ct->value[i].max); 83 } 84 } 85 putchar('\"'); 86 } 87 88 /* string_to_number() is not quite what we need here ... */ 89 static uint32_t parse_number(const char **s, int pos) 90 { 91 unsigned int number; 92 char *end; 93 94 if (!xtables_strtoui(*s, &end, &number, 0, UINT32_MAX) || 95 end == *s) 96 xtables_error(PARAMETER_PROBLEM, 97 "u32: at char %d: not a number or out of range", pos); 98 *s = end; 99 return number; 100 } 101 102 static void u32_parse(struct xt_option_call *cb) 103 { 104 struct xt_u32 *data = cb->data; 105 unsigned int testind = 0, locind = 0, valind = 0; 106 struct xt_u32_test *ct = &data->tests[testind]; /* current test */ 107 const char *arg = cb->arg; /* the argument string */ 108 const char *start = cb->arg; 109 int state = 0; 110 111 xtables_option_parse(cb); 112 data->invert = cb->invert; 113 114 /* 115 * states: 116 * 0 = looking for numbers and operations, 117 * 1 = looking for ranges 118 */ 119 while (1) { 120 /* read next operand/number or range */ 121 while (isspace(*arg)) 122 ++arg; 123 124 if (*arg == '\0') { 125 /* end of argument found */ 126 if (state == 0) 127 xtables_error(PARAMETER_PROBLEM, 128 "u32: abrupt end of input after location specifier"); 129 if (valind == 0) 130 xtables_error(PARAMETER_PROBLEM, 131 "u32: test ended with no value specified"); 132 133 ct->nnums = locind; 134 ct->nvalues = valind; 135 data->ntests = ++testind; 136 137 if (testind > XT_U32_MAXSIZE) 138 xtables_error(PARAMETER_PROBLEM, 139 "u32: at char %u: too many \"&&\"s", 140 (unsigned int)(arg - start)); 141 return; 142 } 143 144 if (state == 0) { 145 /* 146 * reading location: read a number if nothing read yet, 147 * otherwise either op number or = to end location spec 148 */ 149 if (*arg == '=') { 150 if (locind == 0) { 151 xtables_error(PARAMETER_PROBLEM, 152 "u32: at char %u: " 153 "location spec missing", 154 (unsigned int)(arg - start)); 155 } else { 156 ++arg; 157 state = 1; 158 } 159 } else { 160 if (locind != 0) { 161 /* need op before number */ 162 if (*arg == '&') { 163 ct->location[locind].nextop = XT_U32_AND; 164 } else if (*arg == '<') { 165 if (*++arg != '<') 166 xtables_error(PARAMETER_PROBLEM, 167 "u32: at char %u: a second '<' was expected", (unsigned int)(arg - start)); 168 ct->location[locind].nextop = XT_U32_LEFTSH; 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_RIGHTSH; 174 } else if (*arg == '@') { 175 ct->location[locind].nextop = XT_U32_AT; 176 } else { 177 xtables_error(PARAMETER_PROBLEM, 178 "u32: at char %u: operator expected", (unsigned int)(arg - start)); 179 } 180 ++arg; 181 } 182 /* now a number; string_to_number skips white space? */ 183 ct->location[locind].number = 184 parse_number(&arg, arg - start); 185 if (++locind > XT_U32_MAXSIZE) 186 xtables_error(PARAMETER_PROBLEM, 187 "u32: at char %u: too many operators", (unsigned int)(arg - start)); 188 } 189 } else { 190 /* 191 * state 1 - reading values: read a range if nothing 192 * read yet, otherwise either ,range or && to end 193 * test spec 194 */ 195 if (*arg == '&') { 196 if (*++arg != '&') 197 xtables_error(PARAMETER_PROBLEM, 198 "u32: at char %u: a second '&' was expected", (unsigned int)(arg - start)); 199 if (valind == 0) { 200 xtables_error(PARAMETER_PROBLEM, 201 "u32: at char %u: value spec missing", (unsigned int)(arg - start)); 202 } else { 203 ct->nnums = locind; 204 ct->nvalues = valind; 205 ct = &data->tests[++testind]; 206 if (testind > XT_U32_MAXSIZE) 207 xtables_error(PARAMETER_PROBLEM, 208 "u32: at char %u: too many \"&&\"s", (unsigned int)(arg - start)); 209 ++arg; 210 state = 0; 211 locind = 0; 212 valind = 0; 213 } 214 } else { /* read value range */ 215 if (valind > 0) { /* need , before number */ 216 if (*arg != ',') 217 xtables_error(PARAMETER_PROBLEM, 218 "u32: at char %u: expected \",\" or \"&&\"", (unsigned int)(arg - start)); 219 ++arg; 220 } 221 ct->value[valind].min = 222 parse_number(&arg, arg - start); 223 224 while (isspace(*arg)) 225 ++arg; 226 227 if (*arg == ':') { 228 ++arg; 229 ct->value[valind].max = 230 parse_number(&arg, arg-start); 231 } else { 232 ct->value[valind].max = 233 ct->value[valind].min; 234 } 235 236 if (++valind > XT_U32_MAXSIZE) 237 xtables_error(PARAMETER_PROBLEM, 238 "u32: at char %u: too many \",\"s", (unsigned int)(arg - start)); 239 } 240 } 241 } 242 } 243 244 static void u32_print(const void *ip, const struct xt_entry_match *match, 245 int numeric) 246 { 247 const struct xt_u32 *data = (const void *)match->data; 248 printf(" u32"); 249 if (data->invert) 250 printf(" !"); 251 u32_dump(data); 252 } 253 254 static void u32_save(const void *ip, const struct xt_entry_match *match) 255 { 256 const struct xt_u32 *data = (const void *)match->data; 257 if (data->invert) 258 printf(" !"); 259 printf(" --u32"); 260 u32_dump(data); 261 } 262 263 static struct xtables_match u32_match = { 264 .name = "u32", 265 .family = NFPROTO_UNSPEC, 266 .version = XTABLES_VERSION, 267 .size = XT_ALIGN(sizeof(struct xt_u32)), 268 .userspacesize = XT_ALIGN(sizeof(struct xt_u32)), 269 .help = u32_help, 270 .print = u32_print, 271 .save = u32_save, 272 .x6_parse = u32_parse, 273 .x6_options = u32_opts, 274 }; 275 276 void _init(void) 277 { 278 xtables_register_match(&u32_match); 279 } 280
