1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* (C) 2001-2002 Magnus Boden <mb@ozaba.mine.nu> |
3 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
4 | */ |
5 | |
6 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
7 | |
8 | #include <linux/module.h> |
9 | #include <linux/moduleparam.h> |
10 | #include <linux/in.h> |
11 | #include <linux/udp.h> |
12 | #include <linux/netfilter.h> |
13 | |
14 | #include <net/netfilter/nf_conntrack.h> |
15 | #include <net/netfilter/nf_conntrack_tuple.h> |
16 | #include <net/netfilter/nf_conntrack_expect.h> |
17 | #include <net/netfilter/nf_conntrack_ecache.h> |
18 | #include <net/netfilter/nf_conntrack_helper.h> |
19 | #include <linux/netfilter/nf_conntrack_tftp.h> |
20 | |
21 | #define HELPER_NAME "tftp" |
22 | |
23 | MODULE_AUTHOR("Magnus Boden <mb@ozaba.mine.nu>" ); |
24 | MODULE_DESCRIPTION("TFTP connection tracking helper" ); |
25 | MODULE_LICENSE("GPL" ); |
26 | MODULE_ALIAS("ip_conntrack_tftp" ); |
27 | MODULE_ALIAS_NFCT_HELPER(HELPER_NAME); |
28 | |
29 | #define MAX_PORTS 8 |
30 | static unsigned short ports[MAX_PORTS]; |
31 | static unsigned int ports_c; |
32 | module_param_array(ports, ushort, &ports_c, 0400); |
33 | MODULE_PARM_DESC(ports, "Port numbers of TFTP servers" ); |
34 | |
35 | unsigned int (*nf_nat_tftp_hook)(struct sk_buff *skb, |
36 | enum ip_conntrack_info ctinfo, |
37 | struct nf_conntrack_expect *exp) __read_mostly; |
38 | EXPORT_SYMBOL_GPL(nf_nat_tftp_hook); |
39 | |
40 | static int tftp_help(struct sk_buff *skb, |
41 | unsigned int protoff, |
42 | struct nf_conn *ct, |
43 | enum ip_conntrack_info ctinfo) |
44 | { |
45 | const struct tftphdr *tfh; |
46 | struct tftphdr _tftph; |
47 | struct nf_conntrack_expect *exp; |
48 | struct nf_conntrack_tuple *tuple; |
49 | unsigned int ret = NF_ACCEPT; |
50 | typeof(nf_nat_tftp_hook) nf_nat_tftp; |
51 | |
52 | tfh = skb_header_pointer(skb, offset: protoff + sizeof(struct udphdr), |
53 | len: sizeof(_tftph), buffer: &_tftph); |
54 | if (tfh == NULL) |
55 | return NF_ACCEPT; |
56 | |
57 | switch (ntohs(tfh->opcode)) { |
58 | case TFTP_OPCODE_READ: |
59 | case TFTP_OPCODE_WRITE: |
60 | /* RRQ and WRQ works the same way */ |
61 | nf_ct_dump_tuple(t: &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple); |
62 | nf_ct_dump_tuple(t: &ct->tuplehash[IP_CT_DIR_REPLY].tuple); |
63 | |
64 | exp = nf_ct_expect_alloc(me: ct); |
65 | if (exp == NULL) { |
66 | nf_ct_helper_log(skb, ct, fmt: "cannot alloc expectation" ); |
67 | return NF_DROP; |
68 | } |
69 | tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple; |
70 | nf_ct_expect_init(exp, NF_CT_EXPECT_CLASS_DEFAULT, |
71 | nf_ct_l3num(ct), |
72 | &tuple->src.u3, &tuple->dst.u3, |
73 | IPPROTO_UDP, NULL, &tuple->dst.u.udp.port); |
74 | |
75 | pr_debug("expect: " ); |
76 | nf_ct_dump_tuple(t: &exp->tuple); |
77 | |
78 | nf_nat_tftp = rcu_dereference(nf_nat_tftp_hook); |
79 | if (nf_nat_tftp && ct->status & IPS_NAT_MASK) |
80 | ret = nf_nat_tftp(skb, ctinfo, exp); |
81 | else if (nf_ct_expect_related(expect: exp, flags: 0) != 0) { |
82 | nf_ct_helper_log(skb, ct, fmt: "cannot add expectation" ); |
83 | ret = NF_DROP; |
84 | } |
85 | nf_ct_expect_put(exp); |
86 | break; |
87 | case TFTP_OPCODE_DATA: |
88 | case TFTP_OPCODE_ACK: |
89 | pr_debug("Data/ACK opcode\n" ); |
90 | break; |
91 | case TFTP_OPCODE_ERROR: |
92 | pr_debug("Error opcode\n" ); |
93 | break; |
94 | default: |
95 | pr_debug("Unknown opcode\n" ); |
96 | } |
97 | return ret; |
98 | } |
99 | |
100 | static struct nf_conntrack_helper tftp[MAX_PORTS * 2] __read_mostly; |
101 | |
102 | static const struct nf_conntrack_expect_policy tftp_exp_policy = { |
103 | .max_expected = 1, |
104 | .timeout = 5 * 60, |
105 | }; |
106 | |
107 | static void __exit nf_conntrack_tftp_fini(void) |
108 | { |
109 | nf_conntrack_helpers_unregister(tftp, ports_c * 2); |
110 | } |
111 | |
112 | static int __init nf_conntrack_tftp_init(void) |
113 | { |
114 | int i, ret; |
115 | |
116 | NF_CT_HELPER_BUILD_BUG_ON(0); |
117 | |
118 | if (ports_c == 0) |
119 | ports[ports_c++] = TFTP_PORT; |
120 | |
121 | for (i = 0; i < ports_c; i++) { |
122 | nf_ct_helper_init(helper: &tftp[2 * i], AF_INET, IPPROTO_UDP, |
123 | HELPER_NAME, TFTP_PORT, spec_port: ports[i], id: i, |
124 | exp_pol: &tftp_exp_policy, expect_class_max: 0, help: tftp_help, NULL, |
125 | THIS_MODULE); |
126 | nf_ct_helper_init(helper: &tftp[2 * i + 1], AF_INET6, IPPROTO_UDP, |
127 | HELPER_NAME, TFTP_PORT, spec_port: ports[i], id: i, |
128 | exp_pol: &tftp_exp_policy, expect_class_max: 0, help: tftp_help, NULL, |
129 | THIS_MODULE); |
130 | } |
131 | |
132 | ret = nf_conntrack_helpers_register(tftp, ports_c * 2); |
133 | if (ret < 0) { |
134 | pr_err("failed to register helpers\n" ); |
135 | return ret; |
136 | } |
137 | return 0; |
138 | } |
139 | |
140 | module_init(nf_conntrack_tftp_init); |
141 | module_exit(nf_conntrack_tftp_fini); |
142 | |