From d59b9db031abee37a9aa9776662dd15370faabf4 Mon Sep 17 00:00:00 2001 From: Stefan Tomanek Date: Tue, 8 Mar 2011 22:42:51 +0100 Subject: iptables: add -C to check for existing rules It is often useful to check whether a specific rule is already present in a chain without actually modifying the iptables config. Services like fail2ban usually employ techniques like grepping through the output of "iptables -L" which is quite error prone. This patch adds a new operation -C to the iptables command which mostly works like -D; it can detect and indicate the existence of the specified rule by modifying the exit code. The new operation TC_CHECK_ENTRY uses the same code as the -D operation, whose functions got a dry-run parameter appended. Signed-off-by: Stefan Tomanek Signed-off-by: Jan Engelhardt --- iptables.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 54 insertions(+), 6 deletions(-) (limited to 'iptables.c') diff --git a/iptables.c b/iptables.c index a73df3ea..cff4a7b3 100644 --- a/iptables.c +++ b/iptables.c @@ -79,9 +79,10 @@ #define CMD_RENAME_CHAIN 0x0800U #define CMD_LIST_RULES 0x1000U #define CMD_ZERO_NUM 0x2000U -#define NUMBER_OF_CMD 15 +#define CMD_CHECK 0x4000U +#define NUMBER_OF_CMD 16 static const char cmdflags[] = { 'I', 'D', 'D', 'R', 'A', 'L', 'F', 'Z', - 'Z', 'N', 'X', 'P', 'E', 'S' }; + 'Z', 'N', 'X', 'P', 'E', 'S', 'C' }; #define OPT_FRAGMENT 0x00800U #define NUMBER_OF_OPT ARRAY_SIZE(optflags) @@ -91,6 +92,7 @@ static const char optflags[] static struct option original_opts[] = { {.name = "append", .has_arg = 1, .val = 'A'}, {.name = "delete", .has_arg = 1, .val = 'D'}, + {.name = "check", .has_arg = 1, .val = 'C'}, {.name = "insert", .has_arg = 1, .val = 'I'}, {.name = "replace", .has_arg = 1, .val = 'R'}, {.name = "list", .has_arg = 2, .val = 'L'}, @@ -165,7 +167,8 @@ static const char commands_v_options[NUMBER_OF_CMD][NUMBER_OF_OPT] = /*DEL_CHAIN*/ {'x','x','x','x','x',' ','x','x','x','x','x','x'}, /*SET_POLICY*/{'x','x','x','x','x',' ','x','x','x','x',' ','x'}, /*RENAME*/ {'x','x','x','x','x',' ','x','x','x','x','x','x'}, -/*LIST_RULES*/{'x','x','x','x','x',' ','x','x','x','x','x','x'} +/*LIST_RULES*/{'x','x','x','x','x',' ','x','x','x','x','x','x'}, +/*CHECK*/ {'x',' ',' ',' ',' ',' ','x',' ',' ','x','x',' '}, }; static const int inverse_for_options[NUMBER_OF_OPT] = @@ -221,7 +224,7 @@ static void exit_printhelp(const struct xtables_rule_match *matches) { printf("%s v%s\n\n" -"Usage: %s -[AD] chain rule-specification [options]\n" +"Usage: %s -[ACD] chain rule-specification [options]\n" " %s -I chain [rulenum] rule-specification [options]\n" " %s -R chain rulenum rule-specification [options]\n" " %s -D chain rulenum [options]\n" @@ -239,6 +242,7 @@ exit_printhelp(const struct xtables_rule_match *matches) "Commands:\n" "Either long or short options are allowed.\n" " --append -A chain Append to chain\n" +" --check -C chain Check for the existence of a rule\n" " --delete -D chain Delete matching rule from chain\n" " --delete -D chain rulenum\n" " Delete rule rulenum (1 = first) from chain\n" @@ -827,6 +831,36 @@ delete_entry(const ipt_chainlabel chain, return ret; } +static int +check_entry(const ipt_chainlabel chain, struct ipt_entry *fw, + unsigned int nsaddrs, const struct in_addr *saddrs, + const struct in_addr *smasks, unsigned int ndaddrs, + const struct in_addr *daddrs, const struct in_addr *dmasks, + bool verbose, struct iptc_handle *handle, + struct xtables_rule_match *matches, + const struct xtables_target *target) +{ + unsigned int i, j; + int ret = 1; + unsigned char *mask; + + mask = make_delete_mask(matches, target); + for (i = 0; i < nsaddrs; i++) { + fw->ip.src.s_addr = saddrs[i].s_addr; + fw->ip.smsk.s_addr = smasks[i].s_addr; + for (j = 0; j < ndaddrs; j++) { + fw->ip.dst.s_addr = daddrs[j].s_addr; + fw->ip.dmsk.s_addr = dmasks[j].s_addr; + if (verbose) + print_firewall_line(fw, handle); + ret &= iptc_check_entry(chain, fw, mask, handle); + } + } + + free(mask); + return ret; +} + int for_each_chain(int (*fn)(const ipt_chainlabel, int, struct iptc_handle *), int verbose, int builtinstoo, struct iptc_handle *handle) @@ -1423,7 +1457,7 @@ int do_command(int argc, char *argv[], char **table, struct iptc_handle **handle opts = xt_params->orig_opts; while ((cs.c = getopt_long(argc, argv, - "-:A:D:R:I:L::S::M:F::Z::N:X::E:P:Vh::o:p:s:d:j:i:fbvnt:m:xc:g:", + "-:A:C:D:R:I:L::S::M:F::Z::N:X::E:P:Vh::o:p:s:d:j:i:fbvnt:m:xc:g:", opts, NULL)) != -1) { switch (cs.c) { /* @@ -1435,6 +1469,12 @@ int do_command(int argc, char *argv[], char **table, struct iptc_handle **handle chain = optarg; break; + case 'C': + add_command(&command, CMD_CHECK, CMD_NONE, + cs.invert); + chain = optarg; + break; + case 'D': add_command(&command, CMD_DELETE, CMD_NONE, cs.invert); @@ -1778,7 +1818,7 @@ int do_command(int argc, char *argv[], char **table, struct iptc_handle **handle xtables_error(PARAMETER_PROBLEM, "nothing appropriate following !"); - if (command & (CMD_REPLACE | CMD_INSERT | CMD_DELETE | CMD_APPEND)) { + if (command & (CMD_REPLACE | CMD_INSERT | CMD_DELETE | CMD_APPEND | CMD_CHECK)) { if (!(cs.options & OPT_DESTINATION)) dhostnetworkmask = "0.0.0.0/0"; if (!(cs.options & OPT_SOURCE)) @@ -1824,6 +1864,7 @@ int do_command(int argc, char *argv[], char **table, struct iptc_handle **handle if (command == CMD_APPEND || command == CMD_DELETE + || command == CMD_CHECK || command == CMD_INSERT || command == CMD_REPLACE) { if (strcmp(chain, "PREROUTING") == 0 @@ -1914,6 +1955,13 @@ int do_command(int argc, char *argv[], char **table, struct iptc_handle **handle case CMD_DELETE_NUM: ret = iptc_delete_num_entry(chain, rulenum - 1, *handle); break; + case CMD_CHECK: + ret = check_entry(chain, e, + nsaddrs, saddrs, smasks, + ndaddrs, daddrs, dmasks, + cs.options&OPT_VERBOSE, + *handle, cs.matches, cs.target); + break; case CMD_REPLACE: ret = replace_entry(chain, e, rulenum - 1, saddrs, smasks, daddrs, dmasks, -- cgit v1.2.3