diff options
Diffstat (limited to 'net/netfilter/nf_conntrack_irc.c')
-rw-r--r-- | net/netfilter/nf_conntrack_irc.c | 314 |
1 files changed, 314 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_irc.c b/net/netfilter/nf_conntrack_irc.c new file mode 100644 index 000000000..5703846be --- /dev/null +++ b/net/netfilter/nf_conntrack_irc.c @@ -0,0 +1,314 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* IRC extension for IP connection tracking, Version 1.21 + * (C) 2000-2002 by Harald Welte <laforge@gnumonks.org> + * based on RR's ip_conntrack_ftp.c + * (C) 2006-2012 Patrick McHardy <kaber@trash.net> + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/moduleparam.h> +#include <linux/skbuff.h> +#include <linux/in.h> +#include <linux/ip.h> +#include <linux/tcp.h> +#include <linux/netfilter.h> +#include <linux/slab.h> + +#include <net/netfilter/nf_conntrack.h> +#include <net/netfilter/nf_conntrack_expect.h> +#include <net/netfilter/nf_conntrack_helper.h> +#include <linux/netfilter/nf_conntrack_irc.h> + +#define MAX_PORTS 8 +static unsigned short ports[MAX_PORTS]; +static unsigned int ports_c; +static unsigned int max_dcc_channels = 8; +static unsigned int dcc_timeout __read_mostly = 300; +/* This is slow, but it's simple. --RR */ +static char *irc_buffer; +static DEFINE_SPINLOCK(irc_buffer_lock); + +unsigned int (*nf_nat_irc_hook)(struct sk_buff *skb, + enum ip_conntrack_info ctinfo, + unsigned int protoff, + unsigned int matchoff, + unsigned int matchlen, + struct nf_conntrack_expect *exp) __read_mostly; +EXPORT_SYMBOL_GPL(nf_nat_irc_hook); + +#define HELPER_NAME "irc" +#define MAX_SEARCH_SIZE 4095 + +MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); +MODULE_DESCRIPTION("IRC (DCC) connection tracking helper"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("ip_conntrack_irc"); +MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); + +module_param_array(ports, ushort, &ports_c, 0400); +MODULE_PARM_DESC(ports, "port numbers of IRC servers"); +module_param(max_dcc_channels, uint, 0400); +MODULE_PARM_DESC(max_dcc_channels, "max number of expected DCC channels per " + "IRC session"); +module_param(dcc_timeout, uint, 0400); +MODULE_PARM_DESC(dcc_timeout, "timeout on for unestablished DCC channels"); + +static const char *const dccprotos[] = { + "SEND ", "CHAT ", "MOVE ", "TSEND ", "SCHAT " +}; + +#define MINMATCHLEN 5 + +/* tries to get the ip_addr and port out of a dcc command + * return value: -1 on failure, 0 on success + * data pointer to first byte of DCC command data + * data_end pointer to last byte of dcc command data + * ip returns parsed ip of dcc command + * port returns parsed port of dcc command + * ad_beg_p returns pointer to first byte of addr data + * ad_end_p returns pointer to last byte of addr data + */ +static int parse_dcc(char *data, const char *data_end, __be32 *ip, + u_int16_t *port, char **ad_beg_p, char **ad_end_p) +{ + char *tmp; + + /* at least 12: "AAAAAAAA P\1\n" */ + while (*data++ != ' ') + if (data > data_end - 12) + return -1; + + /* Make sure we have a newline character within the packet boundaries + * because simple_strtoul parses until the first invalid character. */ + for (tmp = data; tmp <= data_end; tmp++) + if (*tmp == '\n') + break; + if (tmp > data_end || *tmp != '\n') + return -1; + + *ad_beg_p = data; + *ip = cpu_to_be32(simple_strtoul(data, &data, 10)); + + /* skip blanks between ip and port */ + while (*data == ' ') { + if (data >= data_end) + return -1; + data++; + } + + *port = simple_strtoul(data, &data, 10); + *ad_end_p = data; + + return 0; +} + +static int help(struct sk_buff *skb, unsigned int protoff, + struct nf_conn *ct, enum ip_conntrack_info ctinfo) +{ + unsigned int dataoff; + const struct iphdr *iph; + const struct tcphdr *th; + struct tcphdr _tcph; + const char *data_limit; + char *data, *ib_ptr; + int dir = CTINFO2DIR(ctinfo); + struct nf_conntrack_expect *exp; + struct nf_conntrack_tuple *tuple; + __be32 dcc_ip; + u_int16_t dcc_port; + __be16 port; + int i, ret = NF_ACCEPT; + char *addr_beg_p, *addr_end_p; + typeof(nf_nat_irc_hook) nf_nat_irc; + unsigned int datalen; + + /* If packet is coming from IRC server */ + if (dir == IP_CT_DIR_REPLY) + return NF_ACCEPT; + + /* Until there's been traffic both ways, don't look in packets. */ + if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) + return NF_ACCEPT; + + /* Not a full tcp header? */ + th = skb_header_pointer(skb, protoff, sizeof(_tcph), &_tcph); + if (th == NULL) + return NF_ACCEPT; + + /* No data? */ + dataoff = protoff + th->doff*4; + if (dataoff >= skb->len) + return NF_ACCEPT; + + datalen = skb->len - dataoff; + if (datalen > MAX_SEARCH_SIZE) + datalen = MAX_SEARCH_SIZE; + + spin_lock_bh(&irc_buffer_lock); + ib_ptr = skb_header_pointer(skb, dataoff, datalen, + irc_buffer); + if (!ib_ptr) { + spin_unlock_bh(&irc_buffer_lock); + return NF_ACCEPT; + } + + data = ib_ptr; + data_limit = ib_ptr + datalen; + + /* Skip any whitespace */ + while (data < data_limit - 10) { + if (*data == ' ' || *data == '\r' || *data == '\n') + data++; + else + break; + } + + /* strlen("PRIVMSG x ")=10 */ + if (data < data_limit - 10) { + if (strncasecmp("PRIVMSG ", data, 8)) + goto out; + data += 8; + } + + /* strlen(" :\1DCC SENT t AAAAAAAA P\1\n")=26 + * 7+MINMATCHLEN+strlen("t AAAAAAAA P\1\n")=26 + */ + while (data < data_limit - (21 + MINMATCHLEN)) { + /* Find first " :", the start of message */ + if (memcmp(data, " :", 2)) { + data++; + continue; + } + data += 2; + + /* then check that place only for the DCC command */ + if (memcmp(data, "\1DCC ", 5)) + goto out; + data += 5; + /* we have at least (21+MINMATCHLEN)-(2+5) bytes valid data left */ + + iph = ip_hdr(skb); + pr_debug("DCC found in master %pI4:%u %pI4:%u\n", + &iph->saddr, ntohs(th->source), + &iph->daddr, ntohs(th->dest)); + + for (i = 0; i < ARRAY_SIZE(dccprotos); i++) { + if (memcmp(data, dccprotos[i], strlen(dccprotos[i]))) { + /* no match */ + continue; + } + data += strlen(dccprotos[i]); + pr_debug("DCC %s detected\n", dccprotos[i]); + + /* we have at least + * (21+MINMATCHLEN)-7-dccprotos[i].matchlen bytes valid + * data left (== 14/13 bytes) */ + if (parse_dcc(data, data_limit, &dcc_ip, + &dcc_port, &addr_beg_p, &addr_end_p)) { + pr_debug("unable to parse dcc command\n"); + continue; + } + + pr_debug("DCC bound ip/port: %pI4:%u\n", + &dcc_ip, dcc_port); + + /* dcc_ip can be the internal OR external (NAT'ed) IP */ + tuple = &ct->tuplehash[dir].tuple; + if ((tuple->src.u3.ip != dcc_ip && + ct->tuplehash[!dir].tuple.dst.u3.ip != dcc_ip) || + dcc_port == 0) { + net_warn_ratelimited("Forged DCC command from %pI4: %pI4:%u\n", + &tuple->src.u3.ip, + &dcc_ip, dcc_port); + continue; + } + + exp = nf_ct_expect_alloc(ct); + if (exp == NULL) { + nf_ct_helper_log(skb, ct, + "cannot alloc expectation"); + ret = NF_DROP; + goto out; + } + tuple = &ct->tuplehash[!dir].tuple; + port = htons(dcc_port); + nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, + tuple->src.l3num, + NULL, &tuple->dst.u3, + IPPROTO_TCP, NULL, &port); + + nf_nat_irc = rcu_dereference(nf_nat_irc_hook); + if (nf_nat_irc && ct->status & IPS_NAT_MASK) + ret = nf_nat_irc(skb, ctinfo, protoff, + addr_beg_p - ib_ptr, + addr_end_p - addr_beg_p, + exp); + else if (nf_ct_expect_related(exp, 0) != 0) { + nf_ct_helper_log(skb, ct, + "cannot add expectation"); + ret = NF_DROP; + } + nf_ct_expect_put(exp); + goto out; + } + } + out: + spin_unlock_bh(&irc_buffer_lock); + return ret; +} + +static struct nf_conntrack_helper irc[MAX_PORTS] __read_mostly; +static struct nf_conntrack_expect_policy irc_exp_policy; + +static int __init nf_conntrack_irc_init(void) +{ + int i, ret; + + if (max_dcc_channels < 1) { + pr_err("max_dcc_channels must not be zero\n"); + return -EINVAL; + } + + if (max_dcc_channels > NF_CT_EXPECT_MAX_CNT) { + pr_err("max_dcc_channels must not be more than %u\n", + NF_CT_EXPECT_MAX_CNT); + return -EINVAL; + } + + irc_exp_policy.max_expected = max_dcc_channels; + irc_exp_policy.timeout = dcc_timeout; + + irc_buffer = kmalloc(MAX_SEARCH_SIZE + 1, GFP_KERNEL); + if (!irc_buffer) + return -ENOMEM; + + /* If no port given, default to standard irc port */ + if (ports_c == 0) + ports[ports_c++] = IRC_PORT; + + for (i = 0; i < ports_c; i++) { + nf_ct_helper_init(&irc[i], AF_INET, IPPROTO_TCP, HELPER_NAME, + IRC_PORT, ports[i], i, &irc_exp_policy, + 0, help, NULL, THIS_MODULE); + } + + ret = nf_conntrack_helpers_register(&irc[0], ports_c); + if (ret) { + pr_err("failed to register helpers\n"); + kfree(irc_buffer); + return ret; + } + + return 0; +} + +static void __exit nf_conntrack_irc_fini(void) +{ + nf_conntrack_helpers_unregister(irc, ports_c); + kfree(irc_buffer); +} + +module_init(nf_conntrack_irc_init); +module_exit(nf_conntrack_irc_fini); |