diff options
Diffstat (limited to 'src/helpers/tftp.c')
| -rw-r--r-- | src/helpers/tftp.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/src/helpers/tftp.c b/src/helpers/tftp.c new file mode 100644 index 0000000..45591c6 --- /dev/null +++ b/src/helpers/tftp.c @@ -0,0 +1,138 @@ +/* + * (C) 2013 by Pablo Neira Ayuso <pablo@netfilter.org> + * + * Adapted from: + * + * (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu> + * (C) 2006-2012 Patrick McHardy <kaber@trash.net> + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include "conntrackd.h" +#include "helper.h" +#include "myct.h" +#include "log.h" +#include <errno.h> +#include <netinet/ip.h> +#include <netinet/ip6.h> +#include <netinet/udp.h> +#include <libmnl/libmnl.h> +#include <libnetfilter_conntrack/libnetfilter_conntrack.h> +#include <libnetfilter_queue/libnetfilter_queue.h> +#include <libnetfilter_queue/libnetfilter_queue_udp.h> +#include <libnetfilter_queue/pktbuff.h> +#include <linux/netfilter.h> + +struct tftphdr { + uint16_t opcode; +}; + +#define TFTP_OPCODE_READ 1 +#define TFTP_OPCODE_WRITE 2 +#define TFTP_OPCODE_DATA 3 +#define TFTP_OPCODE_ACK 4 +#define TFTP_OPCODE_ERROR 5 + +static unsigned int nat_tftp(struct pkt_buff *pkt, uint32_t ctinfo, + struct nf_conntrack *ct, struct nf_expect *exp) +{ + struct nf_conntrack *nat_tuple; + static uint32_t zero[4] = { 0, 0, 0, 0 }; + + nat_tuple = nfct_new(); + if (nat_tuple == NULL) + return NF_ACCEPT; + + switch (nfct_get_attr_u8(ct, ATTR_L3PROTO)) { + case AF_INET: + nfct_set_attr_u8(nat_tuple, ATTR_L3PROTO, AF_INET); + nfct_set_attr_u32(nat_tuple, ATTR_IPV4_SRC, 0); + nfct_set_attr_u32(nat_tuple, ATTR_IPV4_DST, 0); + break; + case AF_INET6: + nfct_set_attr_u8(nat_tuple, ATTR_L3PROTO, AF_INET6); + nfct_set_attr(nat_tuple, ATTR_IPV6_SRC, &zero); + nfct_set_attr(nat_tuple, ATTR_IPV6_DST, &zero); + break; + } + nfct_set_attr_u8(nat_tuple, ATTR_L4PROTO, IPPROTO_UDP); + nfct_set_attr_u16(nat_tuple, ATTR_PORT_SRC, + nfct_get_attr_u16(ct, ATTR_PORT_SRC)); + nfct_set_attr_u16(nat_tuple, ATTR_PORT_DST, 0); + + nfexp_set_attr_u32(exp, ATTR_EXP_NAT_DIR, MYCT_DIR_REPL); + nfexp_set_attr(exp, ATTR_EXP_FN, "nat-follow-master"); + nfexp_set_attr(exp, ATTR_EXP_NAT_TUPLE, nat_tuple); + + return NF_ACCEPT; +} + +static int +tftp_helper_cb(struct pkt_buff *pkt, uint32_t protoff, + struct myct *myct, uint32_t ctinfo) +{ + const struct tftphdr *tfh; + struct nf_expect *exp; + unsigned int ret = NF_ACCEPT; + union nfct_attr_grp_addr saddr, daddr; + uint16_t dport; + + tfh = (struct tftphdr *)(pktb_network_header(pkt) + protoff + sizeof(struct udphdr)); + + switch (ntohs(tfh->opcode)) { + case TFTP_OPCODE_READ: + case TFTP_OPCODE_WRITE: + /* RRQ and WRQ works the same way */ + exp = nfexp_new(); + if (exp == NULL) { + pr_debug("cannot alloc expectation\n"); + return NF_DROP; + } + + cthelper_get_addr_src(myct->ct, MYCT_DIR_REPL, &saddr); + cthelper_get_addr_dst(myct->ct, MYCT_DIR_REPL, &daddr); + cthelper_get_port_dst(myct->ct, MYCT_DIR_REPL, &dport); + + if (cthelper_expect_init(exp, myct->ct, 0, &saddr, &daddr, + IPPROTO_UDP, NULL, &dport, 0)) { + nfexp_destroy(exp); + return NF_DROP; + } + + if (nfct_get_attr_u32(myct->ct, ATTR_STATUS) & IPS_NAT_MASK) + ret = nat_tftp(pkt, ctinfo, myct->ct, exp); + + myct->exp = exp; + break; + case TFTP_OPCODE_DATA: + case TFTP_OPCODE_ACK: + pr_debug("Data/ACK opcode\n"); + break; + case TFTP_OPCODE_ERROR: + pr_debug("Error opcode\n"); + break; + default: + pr_debug("Unknown opcode\n"); + } + return ret; +} + +static struct ctd_helper tftp_helper = { + .name = "tftp", + .l4proto = IPPROTO_UDP, + .cb = tftp_helper_cb, + .policy = { + [0] = { + .name = "tftp", + .expect_max = 1, + .expect_timeout = 5 * 60, + }, + }, +}; + +static void __attribute__ ((constructor)) tftp_init(void) +{ + helper_register(&tftp_helper); +} |