diff options
Diffstat (limited to 'extensions/libxt_length.c')
| -rw-r--r-- | extensions/libxt_length.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/extensions/libxt_length.c b/extensions/libxt_length.c new file mode 100644 index 0000000..5b6453e --- /dev/null +++ b/extensions/libxt_length.c @@ -0,0 +1,168 @@ +/* Shared library add-on to iptables to add packet length matching support. */ +#include <stdio.h> +#include <netdb.h> +#include <string.h> +#include <stdlib.h> +#include <getopt.h> + +#include <xtables.h> +#include <linux/netfilter/xt_length.h> + +/* Function which prints out usage message. */ +static void +help(void) +{ + printf( +"length v%s options:\n" +"[!] --length length[:length] Match packet length against value or range\n" +" of values (inclusive)\n", +IPTABLES_VERSION); + +} + +static struct option opts[] = { + { "length", 1, 0, '1' }, + {0} +}; + +static u_int16_t +parse_length(const char *s) +{ + unsigned int len; + + if (string_to_number(s, 0, 0xFFFF, &len) == -1) + exit_error(PARAMETER_PROBLEM, "length invalid: `%s'\n", s); + else + return (u_int16_t )len; +} + +/* If a single value is provided, min and max are both set to the value */ +static void +parse_lengths(const char *s, struct xt_length_info *info) +{ + char *buffer; + char *cp; + + buffer = strdup(s); + if ((cp = strchr(buffer, ':')) == NULL) + info->min = info->max = parse_length(buffer); + else { + *cp = '\0'; + cp++; + + info->min = buffer[0] ? parse_length(buffer) : 0; + info->max = cp[0] ? parse_length(cp) : 0xFFFF; + } + free(buffer); + + if (info->min > info->max) + exit_error(PARAMETER_PROBLEM, + "length min. range value `%u' greater than max. " + "range value `%u'", info->min, info->max); + +} + +/* Function which parses command options; returns true if it + ate an option */ +static int +parse(int c, char **argv, int invert, unsigned int *flags, + const void *entry, + unsigned int *nfcache, + struct xt_entry_match **match) +{ + struct xt_length_info *info = (struct xt_length_info *)(*match)->data; + + switch (c) { + case '1': + if (*flags) + exit_error(PARAMETER_PROBLEM, + "length: `--length' may only be " + "specified once"); + check_inverse(optarg, &invert, &optind, 0); + parse_lengths(argv[optind-1], info); + if (invert) + info->invert = 1; + *flags = 1; + break; + + default: + return 0; + } + return 1; +} + +/* Final check; must have specified --length. */ +static void +final_check(unsigned int flags) +{ + if (!flags) + exit_error(PARAMETER_PROBLEM, + "length: You must specify `--length'"); +} + +/* Common match printing code. */ +static void +print_length(struct xt_length_info *info) +{ + if (info->invert) + printf("! "); + + if (info->max == info->min) + printf("%u ", info->min); + else + printf("%u:%u ", info->min, info->max); +} + +/* Prints out the matchinfo. */ +static void +print(const void *ip, + const struct xt_entry_match *match, + int numeric) +{ + printf("length "); + print_length((struct xt_length_info *)match->data); +} + +/* Saves the union ipt_matchinfo in parsable form to stdout. */ +static void +save(const void *ip, const struct xt_entry_match *match) +{ + printf("--length "); + print_length((struct xt_length_info *)match->data); +} + +static struct xtables_match length = { + .next = NULL, + .family = AF_INET, + .name = "length", + .version = IPTABLES_VERSION, + .size = XT_ALIGN(sizeof(struct xt_length_info)), + .userspacesize = XT_ALIGN(sizeof(struct xt_length_info)), + .help = &help, + .parse = &parse, + .final_check = &final_check, + .print = &print, + .save = &save, + .extra_opts = opts +}; + +static struct xtables_match length6 = { + .next = NULL, + .family = AF_INET6, + .name = "length", + .version = IPTABLES_VERSION, + .size = XT_ALIGN(sizeof(struct xt_length_info)), + .userspacesize = XT_ALIGN(sizeof(struct xt_length_info)), + .help = &help, + .parse = &parse, + .final_check = &final_check, + .print = &print, + .save = &save, + .extra_opts = opts +}; + +void _init(void) +{ + xtables_register_match(&length); + xtables_register_match(&length6); +} |