![Harvey Harrison](/assets/img/avatar_default.png)
Base versions handle constant folding now. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1340 lines
30 KiB
C
1340 lines
30 KiB
C
/*
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* nf_nat_snmp_basic.c
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*
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* Basic SNMP Application Layer Gateway
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*
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* This IP NAT module is intended for use with SNMP network
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* discovery and monitoring applications where target networks use
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* conflicting private address realms.
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*
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* Static NAT is used to remap the networks from the view of the network
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* management system at the IP layer, and this module remaps some application
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* layer addresses to match.
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*
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* The simplest form of ALG is performed, where only tagged IP addresses
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* are modified. The module does not need to be MIB aware and only scans
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* messages at the ASN.1/BER level.
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*
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* Currently, only SNMPv1 and SNMPv2 are supported.
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*
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* More information on ALG and associated issues can be found in
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* RFC 2962
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*
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* The ASB.1/BER parsing code is derived from the gxsnmp package by Gregory
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* McLean & Jochen Friedrich, stripped down for use in the kernel.
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*
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* Copyright (c) 2000 RP Internet (www.rpi.net.au).
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* Author: James Morris <jmorris@intercode.com.au>
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*/
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/in.h>
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#include <linux/ip.h>
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#include <linux/udp.h>
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#include <net/checksum.h>
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#include <net/udp.h>
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#include <net/netfilter/nf_nat.h>
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#include <net/netfilter/nf_conntrack_expect.h>
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#include <net/netfilter/nf_conntrack_helper.h>
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#include <net/netfilter/nf_nat_helper.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
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MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
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MODULE_ALIAS("ip_nat_snmp_basic");
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#define SNMP_PORT 161
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#define SNMP_TRAP_PORT 162
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#define NOCT1(n) (*(u8 *)(n))
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static int debug;
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static DEFINE_SPINLOCK(snmp_lock);
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/*
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* Application layer address mapping mimics the NAT mapping, but
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* only for the first octet in this case (a more flexible system
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* can be implemented if needed).
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*/
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struct oct1_map
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{
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u_int8_t from;
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u_int8_t to;
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};
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/*****************************************************************************
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*
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* Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
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*
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*****************************************************************************/
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/* Class */
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#define ASN1_UNI 0 /* Universal */
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#define ASN1_APL 1 /* Application */
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#define ASN1_CTX 2 /* Context */
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#define ASN1_PRV 3 /* Private */
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/* Tag */
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#define ASN1_EOC 0 /* End Of Contents */
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#define ASN1_BOL 1 /* Boolean */
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#define ASN1_INT 2 /* Integer */
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#define ASN1_BTS 3 /* Bit String */
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#define ASN1_OTS 4 /* Octet String */
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#define ASN1_NUL 5 /* Null */
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#define ASN1_OJI 6 /* Object Identifier */
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#define ASN1_OJD 7 /* Object Description */
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#define ASN1_EXT 8 /* External */
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#define ASN1_SEQ 16 /* Sequence */
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#define ASN1_SET 17 /* Set */
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#define ASN1_NUMSTR 18 /* Numerical String */
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#define ASN1_PRNSTR 19 /* Printable String */
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#define ASN1_TEXSTR 20 /* Teletext String */
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#define ASN1_VIDSTR 21 /* Video String */
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#define ASN1_IA5STR 22 /* IA5 String */
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#define ASN1_UNITIM 23 /* Universal Time */
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#define ASN1_GENTIM 24 /* General Time */
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#define ASN1_GRASTR 25 /* Graphical String */
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#define ASN1_VISSTR 26 /* Visible String */
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#define ASN1_GENSTR 27 /* General String */
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/* Primitive / Constructed methods*/
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#define ASN1_PRI 0 /* Primitive */
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#define ASN1_CON 1 /* Constructed */
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/*
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* Error codes.
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*/
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#define ASN1_ERR_NOERROR 0
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#define ASN1_ERR_DEC_EMPTY 2
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#define ASN1_ERR_DEC_EOC_MISMATCH 3
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#define ASN1_ERR_DEC_LENGTH_MISMATCH 4
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#define ASN1_ERR_DEC_BADVALUE 5
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/*
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* ASN.1 context.
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*/
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struct asn1_ctx
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{
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int error; /* Error condition */
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unsigned char *pointer; /* Octet just to be decoded */
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unsigned char *begin; /* First octet */
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unsigned char *end; /* Octet after last octet */
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};
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/*
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* Octet string (not null terminated)
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*/
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struct asn1_octstr
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{
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unsigned char *data;
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unsigned int len;
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};
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static void asn1_open(struct asn1_ctx *ctx,
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unsigned char *buf,
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unsigned int len)
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{
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ctx->begin = buf;
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ctx->end = buf + len;
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ctx->pointer = buf;
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ctx->error = ASN1_ERR_NOERROR;
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}
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static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
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{
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if (ctx->pointer >= ctx->end) {
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ctx->error = ASN1_ERR_DEC_EMPTY;
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return 0;
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}
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*ch = *(ctx->pointer)++;
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return 1;
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}
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static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
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{
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unsigned char ch;
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*tag = 0;
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do
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{
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*tag <<= 7;
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*tag |= ch & 0x7F;
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} while ((ch & 0x80) == 0x80);
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return 1;
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}
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static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
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unsigned int *cls,
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unsigned int *con,
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unsigned int *tag)
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{
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unsigned char ch;
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*cls = (ch & 0xC0) >> 6;
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*con = (ch & 0x20) >> 5;
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*tag = (ch & 0x1F);
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if (*tag == 0x1F) {
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if (!asn1_tag_decode(ctx, tag))
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return 0;
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}
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return 1;
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}
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static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
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unsigned int *def,
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unsigned int *len)
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{
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unsigned char ch, cnt;
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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if (ch == 0x80)
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*def = 0;
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else {
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*def = 1;
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if (ch < 0x80)
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*len = ch;
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else {
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cnt = ch & 0x7F;
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*len = 0;
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while (cnt > 0) {
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*len <<= 8;
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*len |= ch;
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cnt--;
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}
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}
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}
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/* don't trust len bigger than ctx buffer */
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if (*len > ctx->end - ctx->pointer)
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return 0;
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return 1;
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}
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static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
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unsigned char **eoc,
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unsigned int *cls,
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unsigned int *con,
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unsigned int *tag)
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{
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unsigned int def, len;
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if (!asn1_id_decode(ctx, cls, con, tag))
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return 0;
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def = len = 0;
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if (!asn1_length_decode(ctx, &def, &len))
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return 0;
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/* primitive shall be definite, indefinite shall be constructed */
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if (*con == ASN1_PRI && !def)
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return 0;
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if (def)
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*eoc = ctx->pointer + len;
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else
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*eoc = NULL;
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return 1;
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}
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static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
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{
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unsigned char ch;
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if (eoc == NULL) {
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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if (ch != 0x00) {
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ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
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return 0;
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}
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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if (ch != 0x00) {
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ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
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return 0;
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}
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return 1;
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} else {
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if (ctx->pointer != eoc) {
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ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
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return 0;
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}
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return 1;
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}
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}
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static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
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{
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ctx->pointer = eoc;
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return 1;
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}
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static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
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unsigned char *eoc,
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long *integer)
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{
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unsigned char ch;
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unsigned int len;
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*integer = (signed char) ch;
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len = 1;
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while (ctx->pointer < eoc) {
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if (++len > sizeof (long)) {
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ctx->error = ASN1_ERR_DEC_BADVALUE;
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return 0;
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}
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*integer <<= 8;
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*integer |= ch;
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}
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return 1;
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}
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static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
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unsigned char *eoc,
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unsigned int *integer)
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{
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unsigned char ch;
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unsigned int len;
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*integer = ch;
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if (ch == 0) len = 0;
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else len = 1;
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while (ctx->pointer < eoc) {
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if (++len > sizeof (unsigned int)) {
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ctx->error = ASN1_ERR_DEC_BADVALUE;
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return 0;
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}
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*integer <<= 8;
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*integer |= ch;
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}
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return 1;
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}
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static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
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unsigned char *eoc,
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unsigned long *integer)
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{
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unsigned char ch;
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unsigned int len;
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*integer = ch;
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if (ch == 0) len = 0;
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else len = 1;
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while (ctx->pointer < eoc) {
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if (++len > sizeof (unsigned long)) {
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ctx->error = ASN1_ERR_DEC_BADVALUE;
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return 0;
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}
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*integer <<= 8;
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*integer |= ch;
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}
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return 1;
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}
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static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
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unsigned char *eoc,
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unsigned char **octets,
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unsigned int *len)
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{
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unsigned char *ptr;
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*len = 0;
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*octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
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if (*octets == NULL) {
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if (net_ratelimit())
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printk("OOM in bsalg (%d)\n", __LINE__);
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return 0;
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}
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ptr = *octets;
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while (ctx->pointer < eoc) {
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if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
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kfree(*octets);
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*octets = NULL;
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return 0;
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}
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(*len)++;
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}
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return 1;
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}
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static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
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unsigned long *subid)
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{
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unsigned char ch;
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*subid = 0;
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do {
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if (!asn1_octet_decode(ctx, &ch))
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return 0;
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*subid <<= 7;
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*subid |= ch & 0x7F;
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} while ((ch & 0x80) == 0x80);
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return 1;
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}
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static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
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unsigned char *eoc,
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unsigned long **oid,
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unsigned int *len)
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{
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unsigned long subid;
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unsigned long *optr;
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size_t size;
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size = eoc - ctx->pointer + 1;
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/* first subid actually encodes first two subids */
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if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
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return 0;
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*oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
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if (*oid == NULL) {
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if (net_ratelimit())
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printk("OOM in bsalg (%d)\n", __LINE__);
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return 0;
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}
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optr = *oid;
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if (!asn1_subid_decode(ctx, &subid)) {
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kfree(*oid);
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*oid = NULL;
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return 0;
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}
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if (subid < 40) {
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optr [0] = 0;
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optr [1] = subid;
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} else if (subid < 80) {
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optr [0] = 1;
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optr [1] = subid - 40;
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} else {
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optr [0] = 2;
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optr [1] = subid - 80;
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}
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*len = 2;
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optr += 2;
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while (ctx->pointer < eoc) {
|
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if (++(*len) > size) {
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ctx->error = ASN1_ERR_DEC_BADVALUE;
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kfree(*oid);
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*oid = NULL;
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return 0;
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}
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|
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if (!asn1_subid_decode(ctx, optr++)) {
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kfree(*oid);
|
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*oid = NULL;
|
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return 0;
|
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}
|
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}
|
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return 1;
|
|
}
|
|
|
|
/*****************************************************************************
|
|
*
|
|
* SNMP decoding routines (gxsnmp author Dirk Wisse)
|
|
*
|
|
*****************************************************************************/
|
|
|
|
/* SNMP Versions */
|
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#define SNMP_V1 0
|
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#define SNMP_V2C 1
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#define SNMP_V2 2
|
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#define SNMP_V3 3
|
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|
|
/* Default Sizes */
|
|
#define SNMP_SIZE_COMM 256
|
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#define SNMP_SIZE_OBJECTID 128
|
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#define SNMP_SIZE_BUFCHR 256
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#define SNMP_SIZE_BUFINT 128
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#define SNMP_SIZE_SMALLOBJECTID 16
|
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|
|
/* Requests */
|
|
#define SNMP_PDU_GET 0
|
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#define SNMP_PDU_NEXT 1
|
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#define SNMP_PDU_RESPONSE 2
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#define SNMP_PDU_SET 3
|
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#define SNMP_PDU_TRAP1 4
|
|
#define SNMP_PDU_BULK 5
|
|
#define SNMP_PDU_INFORM 6
|
|
#define SNMP_PDU_TRAP2 7
|
|
|
|
/* Errors */
|
|
#define SNMP_NOERROR 0
|
|
#define SNMP_TOOBIG 1
|
|
#define SNMP_NOSUCHNAME 2
|
|
#define SNMP_BADVALUE 3
|
|
#define SNMP_READONLY 4
|
|
#define SNMP_GENERROR 5
|
|
#define SNMP_NOACCESS 6
|
|
#define SNMP_WRONGTYPE 7
|
|
#define SNMP_WRONGLENGTH 8
|
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#define SNMP_WRONGENCODING 9
|
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#define SNMP_WRONGVALUE 10
|
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#define SNMP_NOCREATION 11
|
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#define SNMP_INCONSISTENTVALUE 12
|
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#define SNMP_RESOURCEUNAVAILABLE 13
|
|
#define SNMP_COMMITFAILED 14
|
|
#define SNMP_UNDOFAILED 15
|
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#define SNMP_AUTHORIZATIONERROR 16
|
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#define SNMP_NOTWRITABLE 17
|
|
#define SNMP_INCONSISTENTNAME 18
|
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|
|
/* General SNMP V1 Traps */
|
|
#define SNMP_TRAP_COLDSTART 0
|
|
#define SNMP_TRAP_WARMSTART 1
|
|
#define SNMP_TRAP_LINKDOWN 2
|
|
#define SNMP_TRAP_LINKUP 3
|
|
#define SNMP_TRAP_AUTFAILURE 4
|
|
#define SNMP_TRAP_EQPNEIGHBORLOSS 5
|
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#define SNMP_TRAP_ENTSPECIFIC 6
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|
|
/* SNMPv1 Types */
|
|
#define SNMP_NULL 0
|
|
#define SNMP_INTEGER 1 /* l */
|
|
#define SNMP_OCTETSTR 2 /* c */
|
|
#define SNMP_DISPLAYSTR 2 /* c */
|
|
#define SNMP_OBJECTID 3 /* ul */
|
|
#define SNMP_IPADDR 4 /* uc */
|
|
#define SNMP_COUNTER 5 /* ul */
|
|
#define SNMP_GAUGE 6 /* ul */
|
|
#define SNMP_TIMETICKS 7 /* ul */
|
|
#define SNMP_OPAQUE 8 /* c */
|
|
|
|
/* Additional SNMPv2 Types */
|
|
#define SNMP_UINTEGER 5 /* ul */
|
|
#define SNMP_BITSTR 9 /* uc */
|
|
#define SNMP_NSAP 10 /* uc */
|
|
#define SNMP_COUNTER64 11 /* ul */
|
|
#define SNMP_NOSUCHOBJECT 12
|
|
#define SNMP_NOSUCHINSTANCE 13
|
|
#define SNMP_ENDOFMIBVIEW 14
|
|
|
|
union snmp_syntax
|
|
{
|
|
unsigned char uc[0]; /* 8 bit unsigned */
|
|
char c[0]; /* 8 bit signed */
|
|
unsigned long ul[0]; /* 32 bit unsigned */
|
|
long l[0]; /* 32 bit signed */
|
|
};
|
|
|
|
struct snmp_object
|
|
{
|
|
unsigned long *id;
|
|
unsigned int id_len;
|
|
unsigned short type;
|
|
unsigned int syntax_len;
|
|
union snmp_syntax syntax;
|
|
};
|
|
|
|
struct snmp_request
|
|
{
|
|
unsigned long id;
|
|
unsigned int error_status;
|
|
unsigned int error_index;
|
|
};
|
|
|
|
struct snmp_v1_trap
|
|
{
|
|
unsigned long *id;
|
|
unsigned int id_len;
|
|
unsigned long ip_address; /* pointer */
|
|
unsigned int general;
|
|
unsigned int specific;
|
|
unsigned long time;
|
|
};
|
|
|
|
/* SNMP types */
|
|
#define SNMP_IPA 0
|
|
#define SNMP_CNT 1
|
|
#define SNMP_GGE 2
|
|
#define SNMP_TIT 3
|
|
#define SNMP_OPQ 4
|
|
#define SNMP_C64 6
|
|
|
|
/* SNMP errors */
|
|
#define SERR_NSO 0
|
|
#define SERR_NSI 1
|
|
#define SERR_EOM 2
|
|
|
|
static inline void mangle_address(unsigned char *begin,
|
|
unsigned char *addr,
|
|
const struct oct1_map *map,
|
|
__sum16 *check);
|
|
struct snmp_cnv
|
|
{
|
|
unsigned int class;
|
|
unsigned int tag;
|
|
int syntax;
|
|
};
|
|
|
|
static const struct snmp_cnv snmp_conv[] = {
|
|
{ASN1_UNI, ASN1_NUL, SNMP_NULL},
|
|
{ASN1_UNI, ASN1_INT, SNMP_INTEGER},
|
|
{ASN1_UNI, ASN1_OTS, SNMP_OCTETSTR},
|
|
{ASN1_UNI, ASN1_OTS, SNMP_DISPLAYSTR},
|
|
{ASN1_UNI, ASN1_OJI, SNMP_OBJECTID},
|
|
{ASN1_APL, SNMP_IPA, SNMP_IPADDR},
|
|
{ASN1_APL, SNMP_CNT, SNMP_COUNTER}, /* Counter32 */
|
|
{ASN1_APL, SNMP_GGE, SNMP_GAUGE}, /* Gauge32 == Unsigned32 */
|
|
{ASN1_APL, SNMP_TIT, SNMP_TIMETICKS},
|
|
{ASN1_APL, SNMP_OPQ, SNMP_OPAQUE},
|
|
|
|
/* SNMPv2 data types and errors */
|
|
{ASN1_UNI, ASN1_BTS, SNMP_BITSTR},
|
|
{ASN1_APL, SNMP_C64, SNMP_COUNTER64},
|
|
{ASN1_CTX, SERR_NSO, SNMP_NOSUCHOBJECT},
|
|
{ASN1_CTX, SERR_NSI, SNMP_NOSUCHINSTANCE},
|
|
{ASN1_CTX, SERR_EOM, SNMP_ENDOFMIBVIEW},
|
|
{0, 0, -1}
|
|
};
|
|
|
|
static unsigned char snmp_tag_cls2syntax(unsigned int tag,
|
|
unsigned int cls,
|
|
unsigned short *syntax)
|
|
{
|
|
const struct snmp_cnv *cnv;
|
|
|
|
cnv = snmp_conv;
|
|
|
|
while (cnv->syntax != -1) {
|
|
if (cnv->tag == tag && cnv->class == cls) {
|
|
*syntax = cnv->syntax;
|
|
return 1;
|
|
}
|
|
cnv++;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static unsigned char snmp_object_decode(struct asn1_ctx *ctx,
|
|
struct snmp_object **obj)
|
|
{
|
|
unsigned int cls, con, tag, len, idlen;
|
|
unsigned short type;
|
|
unsigned char *eoc, *end, *p;
|
|
unsigned long *lp, *id;
|
|
unsigned long ul;
|
|
long l;
|
|
|
|
*obj = NULL;
|
|
id = NULL;
|
|
|
|
if (!asn1_header_decode(ctx, &eoc, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
|
|
return 0;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
|
|
return 0;
|
|
|
|
if (!asn1_oid_decode(ctx, end, &id, &idlen))
|
|
return 0;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
|
|
if (con != ASN1_PRI) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
|
|
type = 0;
|
|
if (!snmp_tag_cls2syntax(tag, cls, &type)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
|
|
l = 0;
|
|
switch (type) {
|
|
case SNMP_INTEGER:
|
|
len = sizeof(long);
|
|
if (!asn1_long_decode(ctx, end, &l)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
*obj = kmalloc(sizeof(struct snmp_object) + len,
|
|
GFP_ATOMIC);
|
|
if (*obj == NULL) {
|
|
kfree(id);
|
|
if (net_ratelimit())
|
|
printk("OOM in bsalg (%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
(*obj)->syntax.l[0] = l;
|
|
break;
|
|
case SNMP_OCTETSTR:
|
|
case SNMP_OPAQUE:
|
|
if (!asn1_octets_decode(ctx, end, &p, &len)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
*obj = kmalloc(sizeof(struct snmp_object) + len,
|
|
GFP_ATOMIC);
|
|
if (*obj == NULL) {
|
|
kfree(p);
|
|
kfree(id);
|
|
if (net_ratelimit())
|
|
printk("OOM in bsalg (%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
memcpy((*obj)->syntax.c, p, len);
|
|
kfree(p);
|
|
break;
|
|
case SNMP_NULL:
|
|
case SNMP_NOSUCHOBJECT:
|
|
case SNMP_NOSUCHINSTANCE:
|
|
case SNMP_ENDOFMIBVIEW:
|
|
len = 0;
|
|
*obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
|
|
if (*obj == NULL) {
|
|
kfree(id);
|
|
if (net_ratelimit())
|
|
printk("OOM in bsalg (%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
if (!asn1_null_decode(ctx, end)) {
|
|
kfree(id);
|
|
kfree(*obj);
|
|
*obj = NULL;
|
|
return 0;
|
|
}
|
|
break;
|
|
case SNMP_OBJECTID:
|
|
if (!asn1_oid_decode(ctx, end, (unsigned long **)&lp, &len)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
len *= sizeof(unsigned long);
|
|
*obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
|
|
if (*obj == NULL) {
|
|
kfree(lp);
|
|
kfree(id);
|
|
if (net_ratelimit())
|
|
printk("OOM in bsalg (%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
memcpy((*obj)->syntax.ul, lp, len);
|
|
kfree(lp);
|
|
break;
|
|
case SNMP_IPADDR:
|
|
if (!asn1_octets_decode(ctx, end, &p, &len)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
if (len != 4) {
|
|
kfree(p);
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
*obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
|
|
if (*obj == NULL) {
|
|
kfree(p);
|
|
kfree(id);
|
|
if (net_ratelimit())
|
|
printk("OOM in bsalg (%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
memcpy((*obj)->syntax.uc, p, len);
|
|
kfree(p);
|
|
break;
|
|
case SNMP_COUNTER:
|
|
case SNMP_GAUGE:
|
|
case SNMP_TIMETICKS:
|
|
len = sizeof(unsigned long);
|
|
if (!asn1_ulong_decode(ctx, end, &ul)) {
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
*obj = kmalloc(sizeof(struct snmp_object) + len, GFP_ATOMIC);
|
|
if (*obj == NULL) {
|
|
kfree(id);
|
|
if (net_ratelimit())
|
|
printk("OOM in bsalg (%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
(*obj)->syntax.ul[0] = ul;
|
|
break;
|
|
default:
|
|
kfree(id);
|
|
return 0;
|
|
}
|
|
|
|
(*obj)->syntax_len = len;
|
|
(*obj)->type = type;
|
|
(*obj)->id = id;
|
|
(*obj)->id_len = idlen;
|
|
|
|
if (!asn1_eoc_decode(ctx, eoc)) {
|
|
kfree(id);
|
|
kfree(*obj);
|
|
*obj = NULL;
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
static unsigned char snmp_request_decode(struct asn1_ctx *ctx,
|
|
struct snmp_request *request)
|
|
{
|
|
unsigned int cls, con, tag;
|
|
unsigned char *end;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
|
|
return 0;
|
|
|
|
if (!asn1_ulong_decode(ctx, end, &request->id))
|
|
return 0;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
|
|
return 0;
|
|
|
|
if (!asn1_uint_decode(ctx, end, &request->error_status))
|
|
return 0;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
|
|
return 0;
|
|
|
|
if (!asn1_uint_decode(ctx, end, &request->error_index))
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Fast checksum update for possibly oddly-aligned UDP byte, from the
|
|
* code example in the draft.
|
|
*/
|
|
static void fast_csum(__sum16 *csum,
|
|
const unsigned char *optr,
|
|
const unsigned char *nptr,
|
|
int offset)
|
|
{
|
|
unsigned char s[4];
|
|
|
|
if (offset & 1) {
|
|
s[0] = s[2] = 0;
|
|
s[1] = ~*optr;
|
|
s[3] = *nptr;
|
|
} else {
|
|
s[1] = s[3] = 0;
|
|
s[0] = ~*optr;
|
|
s[2] = *nptr;
|
|
}
|
|
|
|
*csum = csum_fold(csum_partial(s, 4, ~csum_unfold(*csum)));
|
|
}
|
|
|
|
/*
|
|
* Mangle IP address.
|
|
* - begin points to the start of the snmp messgae
|
|
* - addr points to the start of the address
|
|
*/
|
|
static inline void mangle_address(unsigned char *begin,
|
|
unsigned char *addr,
|
|
const struct oct1_map *map,
|
|
__sum16 *check)
|
|
{
|
|
if (map->from == NOCT1(addr)) {
|
|
u_int32_t old;
|
|
|
|
if (debug)
|
|
memcpy(&old, addr, sizeof(old));
|
|
|
|
*addr = map->to;
|
|
|
|
/* Update UDP checksum if being used */
|
|
if (*check) {
|
|
fast_csum(check,
|
|
&map->from, &map->to, addr - begin);
|
|
|
|
}
|
|
|
|
if (debug)
|
|
printk(KERN_DEBUG "bsalg: mapped %pI4 to %pI4\n",
|
|
&old, addr);
|
|
}
|
|
}
|
|
|
|
static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
|
|
struct snmp_v1_trap *trap,
|
|
const struct oct1_map *map,
|
|
__sum16 *check)
|
|
{
|
|
unsigned int cls, con, tag, len;
|
|
unsigned char *end;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OJI)
|
|
return 0;
|
|
|
|
if (!asn1_oid_decode(ctx, end, &trap->id, &trap->id_len))
|
|
return 0;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
goto err_id_free;
|
|
|
|
if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_IPA) ||
|
|
(cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_OTS)))
|
|
goto err_id_free;
|
|
|
|
if (!asn1_octets_decode(ctx, end, (unsigned char **)&trap->ip_address, &len))
|
|
goto err_id_free;
|
|
|
|
/* IPv4 only */
|
|
if (len != 4)
|
|
goto err_addr_free;
|
|
|
|
mangle_address(ctx->begin, ctx->pointer - 4, map, check);
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
goto err_addr_free;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
|
|
goto err_addr_free;
|
|
|
|
if (!asn1_uint_decode(ctx, end, &trap->general))
|
|
goto err_addr_free;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
goto err_addr_free;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
|
|
goto err_addr_free;
|
|
|
|
if (!asn1_uint_decode(ctx, end, &trap->specific))
|
|
goto err_addr_free;
|
|
|
|
if (!asn1_header_decode(ctx, &end, &cls, &con, &tag))
|
|
goto err_addr_free;
|
|
|
|
if (!((cls == ASN1_APL && con == ASN1_PRI && tag == SNMP_TIT) ||
|
|
(cls == ASN1_UNI && con == ASN1_PRI && tag == ASN1_INT)))
|
|
goto err_addr_free;
|
|
|
|
if (!asn1_ulong_decode(ctx, end, &trap->time))
|
|
goto err_addr_free;
|
|
|
|
return 1;
|
|
|
|
err_addr_free:
|
|
kfree((unsigned long *)trap->ip_address);
|
|
|
|
err_id_free:
|
|
kfree(trap->id);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*****************************************************************************
|
|
*
|
|
* Misc. routines
|
|
*
|
|
*****************************************************************************/
|
|
|
|
static void hex_dump(const unsigned char *buf, size_t len)
|
|
{
|
|
size_t i;
|
|
|
|
for (i = 0; i < len; i++) {
|
|
if (i && !(i % 16))
|
|
printk("\n");
|
|
printk("%02x ", *(buf + i));
|
|
}
|
|
printk("\n");
|
|
}
|
|
|
|
/*
|
|
* Parse and mangle SNMP message according to mapping.
|
|
* (And this is the fucking 'basic' method).
|
|
*/
|
|
static int snmp_parse_mangle(unsigned char *msg,
|
|
u_int16_t len,
|
|
const struct oct1_map *map,
|
|
__sum16 *check)
|
|
{
|
|
unsigned char *eoc, *end;
|
|
unsigned int cls, con, tag, vers, pdutype;
|
|
struct asn1_ctx ctx;
|
|
struct asn1_octstr comm;
|
|
struct snmp_object **obj;
|
|
|
|
if (debug > 1)
|
|
hex_dump(msg, len);
|
|
|
|
asn1_open(&ctx, msg, len);
|
|
|
|
/*
|
|
* Start of SNMP message.
|
|
*/
|
|
if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
|
|
return 0;
|
|
if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
|
|
return 0;
|
|
|
|
/*
|
|
* Version 1 or 2 handled.
|
|
*/
|
|
if (!asn1_header_decode(&ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_INT)
|
|
return 0;
|
|
if (!asn1_uint_decode (&ctx, end, &vers))
|
|
return 0;
|
|
if (debug > 1)
|
|
printk(KERN_DEBUG "bsalg: snmp version: %u\n", vers + 1);
|
|
if (vers > 1)
|
|
return 1;
|
|
|
|
/*
|
|
* Community.
|
|
*/
|
|
if (!asn1_header_decode (&ctx, &end, &cls, &con, &tag))
|
|
return 0;
|
|
if (cls != ASN1_UNI || con != ASN1_PRI || tag != ASN1_OTS)
|
|
return 0;
|
|
if (!asn1_octets_decode(&ctx, end, &comm.data, &comm.len))
|
|
return 0;
|
|
if (debug > 1) {
|
|
unsigned int i;
|
|
|
|
printk(KERN_DEBUG "bsalg: community: ");
|
|
for (i = 0; i < comm.len; i++)
|
|
printk("%c", comm.data[i]);
|
|
printk("\n");
|
|
}
|
|
kfree(comm.data);
|
|
|
|
/*
|
|
* PDU type
|
|
*/
|
|
if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &pdutype))
|
|
return 0;
|
|
if (cls != ASN1_CTX || con != ASN1_CON)
|
|
return 0;
|
|
if (debug > 1) {
|
|
static const unsigned char *const pdus[] = {
|
|
[SNMP_PDU_GET] = "get",
|
|
[SNMP_PDU_NEXT] = "get-next",
|
|
[SNMP_PDU_RESPONSE] = "response",
|
|
[SNMP_PDU_SET] = "set",
|
|
[SNMP_PDU_TRAP1] = "trapv1",
|
|
[SNMP_PDU_BULK] = "bulk",
|
|
[SNMP_PDU_INFORM] = "inform",
|
|
[SNMP_PDU_TRAP2] = "trapv2"
|
|
};
|
|
|
|
if (pdutype > SNMP_PDU_TRAP2)
|
|
printk(KERN_DEBUG "bsalg: bad pdu type %u\n", pdutype);
|
|
else
|
|
printk(KERN_DEBUG "bsalg: pdu: %s\n", pdus[pdutype]);
|
|
}
|
|
if (pdutype != SNMP_PDU_RESPONSE &&
|
|
pdutype != SNMP_PDU_TRAP1 && pdutype != SNMP_PDU_TRAP2)
|
|
return 1;
|
|
|
|
/*
|
|
* Request header or v1 trap
|
|
*/
|
|
if (pdutype == SNMP_PDU_TRAP1) {
|
|
struct snmp_v1_trap trap;
|
|
unsigned char ret = snmp_trap_decode(&ctx, &trap, map, check);
|
|
|
|
if (ret) {
|
|
kfree(trap.id);
|
|
kfree((unsigned long *)trap.ip_address);
|
|
} else
|
|
return ret;
|
|
|
|
} else {
|
|
struct snmp_request req;
|
|
|
|
if (!snmp_request_decode(&ctx, &req))
|
|
return 0;
|
|
|
|
if (debug > 1)
|
|
printk(KERN_DEBUG "bsalg: request: id=0x%lx error_status=%u "
|
|
"error_index=%u\n", req.id, req.error_status,
|
|
req.error_index);
|
|
}
|
|
|
|
/*
|
|
* Loop through objects, look for IP addresses to mangle.
|
|
*/
|
|
if (!asn1_header_decode(&ctx, &eoc, &cls, &con, &tag))
|
|
return 0;
|
|
|
|
if (cls != ASN1_UNI || con != ASN1_CON || tag != ASN1_SEQ)
|
|
return 0;
|
|
|
|
obj = kmalloc(sizeof(struct snmp_object), GFP_ATOMIC);
|
|
if (obj == NULL) {
|
|
if (net_ratelimit())
|
|
printk(KERN_WARNING "OOM in bsalg(%d)\n", __LINE__);
|
|
return 0;
|
|
}
|
|
|
|
while (!asn1_eoc_decode(&ctx, eoc)) {
|
|
unsigned int i;
|
|
|
|
if (!snmp_object_decode(&ctx, obj)) {
|
|
if (*obj) {
|
|
kfree((*obj)->id);
|
|
kfree(*obj);
|
|
}
|
|
kfree(obj);
|
|
return 0;
|
|
}
|
|
|
|
if (debug > 1) {
|
|
printk(KERN_DEBUG "bsalg: object: ");
|
|
for (i = 0; i < (*obj)->id_len; i++) {
|
|
if (i > 0)
|
|
printk(".");
|
|
printk("%lu", (*obj)->id[i]);
|
|
}
|
|
printk(": type=%u\n", (*obj)->type);
|
|
|
|
}
|
|
|
|
if ((*obj)->type == SNMP_IPADDR)
|
|
mangle_address(ctx.begin, ctx.pointer - 4 , map, check);
|
|
|
|
kfree((*obj)->id);
|
|
kfree(*obj);
|
|
}
|
|
kfree(obj);
|
|
|
|
if (!asn1_eoc_decode(&ctx, eoc))
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*****************************************************************************
|
|
*
|
|
* NAT routines.
|
|
*
|
|
*****************************************************************************/
|
|
|
|
/*
|
|
* SNMP translation routine.
|
|
*/
|
|
static int snmp_translate(struct nf_conn *ct,
|
|
enum ip_conntrack_info ctinfo,
|
|
struct sk_buff *skb)
|
|
{
|
|
struct iphdr *iph = ip_hdr(skb);
|
|
struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
|
|
u_int16_t udplen = ntohs(udph->len);
|
|
u_int16_t paylen = udplen - sizeof(struct udphdr);
|
|
int dir = CTINFO2DIR(ctinfo);
|
|
struct oct1_map map;
|
|
|
|
/*
|
|
* Determine mappping for application layer addresses based
|
|
* on NAT manipulations for the packet.
|
|
*/
|
|
if (dir == IP_CT_DIR_ORIGINAL) {
|
|
/* SNAT traps */
|
|
map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
|
|
map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
|
|
} else {
|
|
/* DNAT replies */
|
|
map.from = NOCT1(&ct->tuplehash[dir].tuple.src.u3.ip);
|
|
map.to = NOCT1(&ct->tuplehash[!dir].tuple.dst.u3.ip);
|
|
}
|
|
|
|
if (map.from == map.to)
|
|
return NF_ACCEPT;
|
|
|
|
if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
|
|
paylen, &map, &udph->check)) {
|
|
if (net_ratelimit())
|
|
printk(KERN_WARNING "bsalg: parser failed\n");
|
|
return NF_DROP;
|
|
}
|
|
return NF_ACCEPT;
|
|
}
|
|
|
|
/* We don't actually set up expectations, just adjust internal IP
|
|
* addresses if this is being NATted */
|
|
static int help(struct sk_buff *skb, unsigned int protoff,
|
|
struct nf_conn *ct,
|
|
enum ip_conntrack_info ctinfo)
|
|
{
|
|
int dir = CTINFO2DIR(ctinfo);
|
|
unsigned int ret;
|
|
const struct iphdr *iph = ip_hdr(skb);
|
|
const struct udphdr *udph = (struct udphdr *)((__be32 *)iph + iph->ihl);
|
|
|
|
/* SNMP replies and originating SNMP traps get mangled */
|
|
if (udph->source == htons(SNMP_PORT) && dir != IP_CT_DIR_REPLY)
|
|
return NF_ACCEPT;
|
|
if (udph->dest == htons(SNMP_TRAP_PORT) && dir != IP_CT_DIR_ORIGINAL)
|
|
return NF_ACCEPT;
|
|
|
|
/* No NAT? */
|
|
if (!(ct->status & IPS_NAT_MASK))
|
|
return NF_ACCEPT;
|
|
|
|
/*
|
|
* Make sure the packet length is ok. So far, we were only guaranteed
|
|
* to have a valid length IP header plus 8 bytes, which means we have
|
|
* enough room for a UDP header. Just verify the UDP length field so we
|
|
* can mess around with the payload.
|
|
*/
|
|
if (ntohs(udph->len) != skb->len - (iph->ihl << 2)) {
|
|
if (net_ratelimit())
|
|
printk(KERN_WARNING "SNMP: dropping malformed packet src=%pI4 dst=%pI4\n",
|
|
&iph->saddr, &iph->daddr);
|
|
return NF_DROP;
|
|
}
|
|
|
|
if (!skb_make_writable(skb, skb->len))
|
|
return NF_DROP;
|
|
|
|
spin_lock_bh(&snmp_lock);
|
|
ret = snmp_translate(ct, ctinfo, skb);
|
|
spin_unlock_bh(&snmp_lock);
|
|
return ret;
|
|
}
|
|
|
|
static const struct nf_conntrack_expect_policy snmp_exp_policy = {
|
|
.max_expected = 0,
|
|
.timeout = 180,
|
|
};
|
|
|
|
static struct nf_conntrack_helper snmp_helper __read_mostly = {
|
|
.me = THIS_MODULE,
|
|
.help = help,
|
|
.expect_policy = &snmp_exp_policy,
|
|
.name = "snmp",
|
|
.tuple.src.l3num = AF_INET,
|
|
.tuple.src.u.udp.port = cpu_to_be16(SNMP_PORT),
|
|
.tuple.dst.protonum = IPPROTO_UDP,
|
|
};
|
|
|
|
static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
|
|
.me = THIS_MODULE,
|
|
.help = help,
|
|
.expect_policy = &snmp_exp_policy,
|
|
.name = "snmp_trap",
|
|
.tuple.src.l3num = AF_INET,
|
|
.tuple.src.u.udp.port = cpu_to_be16(SNMP_TRAP_PORT),
|
|
.tuple.dst.protonum = IPPROTO_UDP,
|
|
};
|
|
|
|
/*****************************************************************************
|
|
*
|
|
* Module stuff.
|
|
*
|
|
*****************************************************************************/
|
|
|
|
static int __init nf_nat_snmp_basic_init(void)
|
|
{
|
|
int ret = 0;
|
|
|
|
ret = nf_conntrack_helper_register(&snmp_helper);
|
|
if (ret < 0)
|
|
return ret;
|
|
ret = nf_conntrack_helper_register(&snmp_trap_helper);
|
|
if (ret < 0) {
|
|
nf_conntrack_helper_unregister(&snmp_helper);
|
|
return ret;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
static void __exit nf_nat_snmp_basic_fini(void)
|
|
{
|
|
nf_conntrack_helper_unregister(&snmp_helper);
|
|
nf_conntrack_helper_unregister(&snmp_trap_helper);
|
|
}
|
|
|
|
module_init(nf_nat_snmp_basic_init);
|
|
module_exit(nf_nat_snmp_basic_fini);
|
|
|
|
module_param(debug, int, 0600);
|