372 lines
9.6 KiB
Diff
372 lines
9.6 KiB
Diff
--- /dev/null
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+++ b/libxt_layer7.c
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@@ -0,0 +1,368 @@
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+/*
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+ Shared library add-on to iptables for layer 7 matching support.
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+
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+ By Matthew Strait <quadong@users.sf.net>, Oct 2003-Aug 2008.
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+
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+ http://l7-filter.sf.net
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+
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+ This program is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU General Public License
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+ as published by the Free Software Foundation; either version
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+ 2 of the License, or (at your option) any later version.
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+ http://www.gnu.org/licenses/gpl.txt
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+*/
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+
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+#define _GNU_SOURCE
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+#include <stdio.h>
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+#include <netdb.h>
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+#include <string.h>
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+#include <stdlib.h>
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+#include <getopt.h>
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+#include <ctype.h>
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+#include <dirent.h>
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+
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+#include <xtables.h>
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+#include <linux/netfilter/xt_layer7.h>
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+
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+#define MAX_FN_LEN 256
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+
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+static char l7dir[MAX_FN_LEN] = "\0";
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+
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+/* Function which prints out usage message. */
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+static void help(void)
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+{
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+ printf(
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+ "layer7 match options:\n"
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+ " --l7dir <directory> : Look for patterns here instead of /etc/l7-protocols/\n"
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+ " (--l7dir must be specified before --l7proto if used)\n"
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+ "[!] --l7proto <name>: Match named protocol using /etc/l7-protocols/.../name.pat\n");
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+}
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+
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+static const struct option opts[] = {
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+ { .name = "l7proto", .has_arg = 1, .val = 'p' },
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+ { .name = "l7dir", .has_arg = 1, .val = 'd' },
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+ { .name = NULL }
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+};
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+
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+/* reads filename, puts protocol info into layer7_protocol_info, number of protocols to numprotos */
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+static int parse_protocol_file(char * filename, const char * protoname, struct xt_layer7_info *info)
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+{
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+ FILE * f;
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+ char * line = NULL;
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+ size_t len = 0;
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+
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+ enum { protocol, pattern, done } datatype = protocol;
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+
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+ f = fopen(filename, "r");
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+
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+ if(!f)
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+ return 0;
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+
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+ while(getline(&line, &len, f) != -1)
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+ {
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+ if(strlen(line) < 2 || line[0] == '#')
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+ continue;
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+
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+ /* strip the pesky newline... */
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+ if(line[strlen(line) - 1] == '\n')
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+ line[strlen(line) - 1] = '\0';
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+
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+ if(datatype == protocol)
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+ {
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+ /* Ignore everything on the line beginning with the
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+ first space or tab . For instance, this allows the
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+ protocol line in http.pat to be "http " (or
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+ "http I am so cool") instead of just "http". */
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+ if(strchr(line, ' ')){
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+ char * space = strchr(line, ' ');
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+ space[0] = '\0';
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+ }
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+ if(strchr(line, '\t')){
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+ char * space = strchr(line, '\t');
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+ space[0] = '\0';
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+ }
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+
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+ /* sanity check. First non-comment non-blank
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+ line must be the same as the file name. */
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+ if(strcmp(line, protoname))
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+ xtables_error(OTHER_PROBLEM,
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+ "Protocol name (%s) doesn't match file name (%s). Bailing out\n",
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+ line, filename);
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+
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+ if(strlen(line) >= MAX_PROTOCOL_LEN)
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+ xtables_error(PARAMETER_PROBLEM,
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+ "Protocol name in %s too long!", filename);
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+ strncpy(info->protocol, line, MAX_PROTOCOL_LEN);
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+
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+ datatype = pattern;
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+ }
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+ else if(datatype == pattern)
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+ {
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+ if(strlen(line) >= MAX_PATTERN_LEN)
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+ xtables_error(PARAMETER_PROBLEM, "Pattern in %s too long!", filename);
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+ strncpy(info->pattern, line, MAX_PATTERN_LEN);
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+
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+ datatype = done;
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+ break;
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+ }
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+ else
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+ xtables_error(OTHER_PROBLEM, "Internal error");
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+ }
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+
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+ if(datatype != done)
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+ xtables_error(OTHER_PROBLEM, "Failed to get all needed data from %s", filename);
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+
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+ if(line) free(line);
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+ fclose(f);
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+
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+ return 1;
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+}
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+
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+static int hex2dec(char c)
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+{
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+ switch (c)
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+ {
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+ case '0' ... '9':
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+ return c - '0';
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+ case 'a' ... 'f':
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+ return c - 'a' + 10;
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+ case 'A' ... 'F':
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+ return c - 'A' + 10;
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+ default:
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+ xtables_error(OTHER_PROBLEM, "hex2dec: bad value!\n");
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+ return 0;
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+ }
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+}
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+
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+/* takes a string with \xHH escapes and returns one with the characters
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+they stand for */
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+static char * pre_process(char * s)
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+{
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+ char * result = malloc(strlen(s) + 1);
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+ int sindex = 0, rrindex = 0;
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+ while( sindex < strlen(s) )
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+ {
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+ if( sindex + 3 < strlen(s) &&
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+ s[sindex] == '\\' && s[sindex+1] == 'x' &&
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+ isxdigit(s[sindex + 2]) && isxdigit(s[sindex + 3]) )
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+ {
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+ /* carefully remember to call tolower here... */
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+ result[rrindex] = tolower( hex2dec(s[sindex + 2])*16 +
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+ hex2dec(s[sindex + 3] ) );
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+
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+ switch ( result[rrindex] )
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+ {
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+ case 0x24:
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+ case 0x28:
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+ case 0x29:
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+ case 0x2a:
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+ case 0x2b:
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+ case 0x2e:
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+ case 0x3f:
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+ case 0x5b:
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+ case 0x5c:
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+ case 0x5d:
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+ case 0x5e:
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+ case 0x7c:
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+ fprintf(stderr,
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+ "Warning: layer7 regexp contains a control character, %c, in hex (\\x%c%c).\n"
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+ "I recommend that you write this as %c or \\%c, depending on what you meant.\n",
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+ result[rrindex], s[sindex + 2], s[sindex + 3], result[rrindex], result[rrindex]);
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+ break;
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+ case 0x00:
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+ fprintf(stderr,
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+ "Warning: null (\\x00) in layer7 regexp. A null terminates the regexp string!\n");
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+ break;
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+ default:
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+ break;
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+ }
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+
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+
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+ sindex += 3; /* 4 total */
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+ }
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+ else
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+ result[rrindex] = tolower(s[sindex]);
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+
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+ sindex++;
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+ rrindex++;
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+ }
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+ result[rrindex] = '\0';
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+
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+ return result;
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+}
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+
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+#define MAX_SUBDIRS 128
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+static char ** readl7dir(char * dirname)
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+{
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+ DIR * scratchdir;
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+ struct dirent ** namelist;
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+ char ** subdirs = malloc(MAX_SUBDIRS * sizeof(char *));
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+
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+ int n, d = 1;
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+ subdirs[0] = "";
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+
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+ n = scandir(dirname, &namelist, 0, alphasort);
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+
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+ if (n < 0)
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+ {
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+ perror("scandir");
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+ xtables_error(OTHER_PROBLEM, "Couldn't open %s\n", dirname);
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+ }
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+ else
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+ {
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+ while(n--)
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+ {
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+ char fulldirname[MAX_FN_LEN];
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+
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+ snprintf(fulldirname, MAX_FN_LEN, "%s/%s", dirname, namelist[n]->d_name);
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+
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+ if((scratchdir = opendir(fulldirname)) != NULL)
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+ {
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+ closedir(scratchdir);
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+
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+ if(!strcmp(namelist[n]->d_name, ".") ||
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+ !strcmp(namelist[n]->d_name, ".."))
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+ /* do nothing */ ;
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+ else
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+ {
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+ subdirs[d] = malloc(strlen(namelist[n]->d_name) + 1);
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+ strcpy(subdirs[d], namelist[n]->d_name);
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+ d++;
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+ if(d >= MAX_SUBDIRS - 1)
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+ {
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+ fprintf(stderr,
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+ "Too many subdirectories, skipping the rest!\n");
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+ break;
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+ }
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+ }
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+ }
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+ free(namelist[n]);
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+ }
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+ free(namelist);
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+ }
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+
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+ subdirs[d] = NULL;
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+
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+ return subdirs;
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+}
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+
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+static void parse_layer7_protocol(const char *s, struct xt_layer7_info *info)
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+{
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+ char filename[MAX_FN_LEN];
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+ char * dir = NULL;
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+ char ** subdirs;
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+ int n = 0, done = 0;
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+
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+ if(strlen(l7dir) > 0) dir = l7dir;
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+ else dir = "/etc/l7-protocols";
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+
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+ subdirs = readl7dir(dir);
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+
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+ while(subdirs[n] != NULL)
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+ {
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+ int c = snprintf(filename, MAX_FN_LEN, "%s/%s/%s.pat", dir, subdirs[n], s);
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+
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+ if(c > MAX_FN_LEN)
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+ xtables_error(OTHER_PROBLEM,
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+ "Filename beginning with %s is too long!\n", filename);
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+
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+ /* read in the pattern from the file */
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+ if(parse_protocol_file(filename, s, info)){
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+ done = 1;
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+ break;
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+ }
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+
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+ n++;
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+ }
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+
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+ if(!done)
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+ xtables_error(OTHER_PROBLEM,
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+ "Couldn't find a pattern definition file for %s.\n", s);
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+
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+ /* process \xHH escapes and tolower everything. (our regex lib has no
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+ case insensitivity option.) */
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+ strncpy(info->pattern, pre_process(info->pattern), MAX_PATTERN_LEN);
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+}
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+
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+/* Function which parses command options; returns true if it ate an option */
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+static int parse(int c, char **argv, int invert, unsigned int *flags,
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+ const void *entry, struct xt_entry_match **match)
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+{
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+ struct xt_layer7_info *layer7info =
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+ (struct xt_layer7_info *)(*match)->data;
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+
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+ switch (c) {
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+ case 'p':
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+ parse_layer7_protocol(argv[optind-1], layer7info);
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+ if (invert)
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+ layer7info->invert = true;
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+ *flags = 1;
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+ break;
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+
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+ case 'd':
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+ if(strlen(argv[optind-1]) >= MAX_FN_LEN)
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+ xtables_error(PARAMETER_PROBLEM, "directory name too long\n");
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+
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+ strncpy(l7dir, argv[optind-1], MAX_FN_LEN);
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+
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+ *flags = 1;
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+ break;
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+
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+ default:
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+ return 0;
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+ }
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+
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+ return 1;
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+}
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+
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+/* Final check; must have specified --l7proto */
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+static void final_check(unsigned int flags)
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+{
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+ if (!flags)
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+ xtables_error(PARAMETER_PROBLEM,
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+ "LAYER7 match: You must specify `--l7proto'");
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+}
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+
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+static void print_protocol(char s[], int invert, int numeric)
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+{
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+ fputs("l7proto ", stdout);
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+ if (invert) fputc('!', stdout);
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+ printf("%s ", s);
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+}
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+
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+/* Prints out the matchinfo. */
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+static void print(const void *ip,
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+ const struct xt_entry_match *match,
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+ int numeric)
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+{
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+ printf("LAYER7 ");
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+ print_protocol(((struct xt_layer7_info *)match->data)->protocol,
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+ ((struct xt_layer7_info *)match->data)->invert, numeric);
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+}
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+/* Saves the union ipt_matchinfo in parsable form to stdout. */
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+static void save(const void *ip, const struct xt_entry_match *match)
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+{
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+ const struct xt_layer7_info *info =
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+ (const struct xt_layer7_info*) match->data;
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+
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+ printf("--l7proto %s%s ", (info->invert)? "! ":"", info->protocol);
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+}
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+
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+static struct xtables_match layer7 = {
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+ .family = AF_INET,
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+ .name = "layer7",
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+ .version = XTABLES_VERSION,
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+ .size = XT_ALIGN(sizeof(struct xt_layer7_info)),
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+ .userspacesize = XT_ALIGN(sizeof(struct xt_layer7_info)),
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+ .help = &help,
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+ .parse = &parse,
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+ .final_check = &final_check,
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+ .print = &print,
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+ .save = &save,
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+ .extra_opts = opts
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+};
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+
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+void _init(void)
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+{
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+ xtables_register_match(&layer7);
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+}
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