Release 4.11 net/ipv4/netfilter/nf_nat_snmp_basic.c
/*
* nf_nat_snmp_basic.c
*
* Basic SNMP Application Layer Gateway
*
* This IP NAT module is intended for use with SNMP network
* discovery and monitoring applications where target networks use
* conflicting private address realms.
*
* Static NAT is used to remap the networks from the view of the network
* management system at the IP layer, and this module remaps some application
* layer addresses to match.
*
* The simplest form of ALG is performed, where only tagged IP addresses
* are modified. The module does not need to be MIB aware and only scans
* messages at the ASN.1/BER level.
*
* Currently, only SNMPv1 and SNMPv2 are supported.
*
* More information on ALG and associated issues can be found in
* RFC 2962
*
* The ASB.1/BER parsing code is derived from the gxsnmp package by Gregory
* McLean & Jochen Friedrich, stripped down for use in the kernel.
*
* Copyright (c) 2000 RP Internet (www.rpi.net.au).
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*
* Author: James Morris <jmorris@intercode.com.au>
*
* Copyright (c) 2006-2010 Patrick McHardy <kaber@trash.net>
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_conntrack_expect.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_nat_helper.h>
#include <linux/netfilter/nf_conntrack_snmp.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
MODULE_ALIAS("ip_nat_snmp_basic");
#define SNMP_PORT 161
#define SNMP_TRAP_PORT 162
#define NOCT1(n) (*(u8 *)(n))
static int debug;
static DEFINE_SPINLOCK(snmp_lock);
/*
* Application layer address mapping mimics the NAT mapping, but
* only for the first octet in this case (a more flexible system
* can be implemented if needed).
*/
struct oct1_map
{
u_int8_t from;
u_int8_t to;
};
/*****************************************************************************
*
* Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
*
*****************************************************************************/
/* Class */
#define ASN1_UNI 0
/* Universal */
#define ASN1_APL 1
/* Application */
#define ASN1_CTX 2
/* Context */
#define ASN1_PRV 3
/* Private */
/* Tag */
#define ASN1_EOC 0
/* End Of Contents */
#define ASN1_BOL 1
/* Boolean */
#define ASN1_INT 2
/* Integer */
#define ASN1_BTS 3
/* Bit String */
#define ASN1_OTS 4
/* Octet String */
#define ASN1_NUL 5
/* Null */
#define ASN1_OJI 6
/* Object Identifier */
#define ASN1_OJD 7
/* Object Description */
#define ASN1_EXT 8
/* External */
#define ASN1_SEQ 16
/* Sequence */
#define ASN1_SET 17
/* Set */
#define ASN1_NUMSTR 18
/* Numerical String */
#define ASN1_PRNSTR 19
/* Printable String */
#define ASN1_TEXSTR 20
/* Teletext String */
#define ASN1_VIDSTR 21
/* Video String */
#define ASN1_IA5STR 22
/* IA5 String */
#define ASN1_UNITIM 23
/* Universal Time */
#define ASN1_GENTIM 24
/* General Time */
#define ASN1_GRASTR 25
/* Graphical String */
#define ASN1_VISSTR 26
/* Visible String */
#define ASN1_GENSTR 27
/* General String */
/* Primitive / Constructed methods*/
#define ASN1_PRI 0
/* Primitive */
#define ASN1_CON 1
/* Constructed */
/*
* Error codes.
*/
#define ASN1_ERR_NOERROR 0
#define ASN1_ERR_DEC_EMPTY 2
#define ASN1_ERR_DEC_EOC_MISMATCH 3
#define ASN1_ERR_DEC_LENGTH_MISMATCH 4
#define ASN1_ERR_DEC_BADVALUE 5
/*
* ASN.1 context.
*/
struct asn1_ctx
{
int error; /* Error condition */
unsigned char *pointer; /* Octet just to be decoded */
unsigned char *begin; /* First octet */
unsigned char *end; /* Octet after last octet */
};
/*
* Octet string (not null terminated)
*/
struct asn1_octstr
{
unsigned char *data;
unsigned int len;
};
static void asn1_open(struct asn1_ctx *ctx,
unsigned char *buf,
unsigned int len)
{
ctx->begin = buf;
ctx->end = buf + len;
ctx->pointer = buf;
ctx->error = ASN1_ERR_NOERROR;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 46 | 100.00% | 1 | 100.00% |
Total | 46 | 100.00% | 1 | 100.00% |
static unsigned char asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
{
if (ctx->pointer >= ctx->end) {
ctx->error = ASN1_ERR_DEC_EMPTY;
return 0;
}
*ch = *(ctx->pointer)++;
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 52 | 100.00% | 1 | 100.00% |
Total | 52 | 100.00% | 1 | 100.00% |
static unsigned char asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
{
unsigned char ch;
*tag = 0;
do
{
if (!asn1_octet_decode(ctx, &ch))
return 0;
*tag <<= 7;
*tag |= ch & 0x7F;
} while ((ch & 0x80) == 0x80);
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 69 | 100.00% | 1 | 100.00% |
Total | 69 | 100.00% | 1 | 100.00% |
static unsigned char asn1_id_decode(struct asn1_ctx *ctx,
unsigned int *cls,
unsigned int *con,
unsigned int *tag)
{
unsigned char ch;
if (!asn1_octet_decode(ctx, &ch))
return 0;
*cls = (ch & 0xC0) >> 6;
*con = (ch & 0x20) >> 5;
*tag = (ch & 0x1F);
if (*tag == 0x1F) {
if (!asn1_tag_decode(ctx, tag))
return 0;
}
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 101 | 100.00% | 1 | 100.00% |
Total | 101 | 100.00% | 1 | 100.00% |
static unsigned char asn1_length_decode(struct asn1_ctx *ctx,
unsigned int *def,
unsigned int *len)
{
unsigned char ch, cnt;
if (!asn1_octet_decode(ctx, &ch))
return 0;
if (ch == 0x80)
*def = 0;
else {
*def = 1;
if (ch < 0x80)
*len = ch;
else {
cnt = ch & 0x7F;
*len = 0;
while (cnt > 0) {
if (!asn1_octet_decode(ctx, &ch))
return 0;
*len <<= 8;
*len |= ch;
cnt--;
}
}
}
/* don't trust len bigger than ctx buffer */
if (*len > ctx->end - ctx->pointer)
return 0;
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 124 | 87.94% | 1 | 50.00% |
Chris Wright | 17 | 12.06% | 1 | 50.00% |
Total | 141 | 100.00% | 2 | 100.00% |
static unsigned char asn1_header_decode(struct asn1_ctx *ctx,
unsigned char **eoc,
unsigned int *cls,
unsigned int *con,
unsigned int *tag)
{
unsigned int def, len;
if (!asn1_id_decode(ctx, cls, con, tag))
return 0;
def = len = 0;
if (!asn1_length_decode(ctx, &def, &len))
return 0;
/* primitive shall be definite, indefinite shall be constructed */
if (*con == ASN1_PRI && !def)
return 0;
if (def)
*eoc = ctx->pointer + len;
else
*eoc = NULL;
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 101 | 87.83% | 1 | 50.00% |
Chris Wright | 14 | 12.17% | 1 | 50.00% |
Total | 115 | 100.00% | 2 | 100.00% |
static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
{
unsigned char ch;
if (eoc == NULL) {
if (!asn1_octet_decode(ctx, &ch))
return 0;
if (ch != 0x00) {
ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
return 0;
}
if (!asn1_octet_decode(ctx, &ch))
return 0;
if (ch != 0x00) {
ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
return 0;
}
return 1;
} else {
if (ctx->pointer != eoc) {
ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
return 0;
}
return 1;
}
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 118 | 99.16% | 1 | 50.00% |
Stephen Hemminger | 1 | 0.84% | 1 | 50.00% |
Total | 119 | 100.00% | 2 | 100.00% |
static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
{
ctx->pointer = eoc;
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 26 | 100.00% | 1 | 100.00% |
Total | 26 | 100.00% | 1 | 100.00% |
static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
unsigned char *eoc,
long *integer)
{
unsigned char ch;
unsigned int len;
if (!asn1_octet_decode(ctx, &ch))
return 0;
*integer = (signed char) ch;
len = 1;
while (ctx->pointer < eoc) {
if (++len > sizeof (long)) {
ctx->error = ASN1_ERR_DEC_BADVALUE;
return 0;
}
if (!asn1_octet_decode(ctx, &ch))
return 0;
*integer <<= 8;
*integer |= ch;
}
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 114 | 100.00% | 1 | 100.00% |
Total | 114 | 100.00% | 1 | 100.00% |
static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
unsigned char *eoc,
unsigned int *integer)
{
unsigned char ch;
unsigned int len;
if (!asn1_octet_decode(ctx, &ch))
return 0;
*integer = ch;
if (ch == 0) len = 0;
else len = 1;
while (ctx->pointer < eoc) {
if (++len > sizeof (unsigned int)) {
ctx->error = ASN1_ERR_DEC_BADVALUE;
return 0;
}
if (!asn1_octet_decode(ctx, &ch))
return 0;
*integer <<= 8;
*integer |= ch;
}
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 123 | 100.00% | 1 | 100.00% |
Total | 123 | 100.00% | 1 | 100.00% |
static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
unsigned char *eoc,
unsigned long *integer)
{
unsigned char ch;
unsigned int len;
if (!asn1_octet_decode(ctx, &ch))
return 0;
*integer = ch;
if (ch == 0) len = 0;
else len = 1;
while (ctx->pointer < eoc) {
if (++len > sizeof (unsigned long)) {
ctx->error = ASN1_ERR_DEC_BADVALUE;
return 0;
}
if (!asn1_octet_decode(ctx, &ch))
return 0;
*integer <<= 8;
*integer |= ch;
}
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 123 | 100.00% | 1 | 100.00% |
Total | 123 | 100.00% | 1 | 100.00% |
static unsigned char asn1_octets_decode(struct asn1_ctx *ctx,
unsigned char *eoc,
unsigned char **octets,
unsigned int *len)
{
unsigned char *ptr;
*len = 0;
*octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
if (*octets == NULL)
return 0;
ptr = *octets;
while (ctx->pointer < eoc) {
if (!asn1_octet_decode(ctx, ptr++)) {
kfree(*octets);
*octets = NULL;
return 0;
}
(*len)++;
}
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 113 | 100.00% | 1 | 100.00% |
Total | 113 | 100.00% | 1 | 100.00% |
static unsigned char asn1_subid_decode(struct asn1_ctx *ctx,
unsigned long *subid)
{
unsigned char ch;
*subid = 0;
do {
if (!asn1_octet_decode(ctx, &ch))
return 0;
*subid <<= 7;
*subid |= ch & 0x7F;
} while ((ch & 0x80) == 0x80);
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 69 | 100.00% | 1 | 100.00% |
Total | 69 | 100.00% | 1 | 100.00% |
static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
unsigned char *eoc,
unsigned long **oid,
unsigned int *len)
{
unsigned long subid;
unsigned long *optr;
size_t size;
size = eoc - ctx->pointer + 1;
/* first subid actually encodes first two subids */
if (size < 2 || size > ULONG_MAX/sizeof(unsigned long))
return 0;
*oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
if (*oid == NULL)
return 0;
optr = *oid;
if (!asn1_subid_decode(ctx, &subid)) {
kfree(*oid);
*oid = NULL;
return 0;
}
if (subid < 40) {
optr[0] = 0;
optr[1] = subid;
} else if (subid < 80) {
optr[0] = 1;
optr[1] = subid - 40;
} else {
optr[0] = 2;
optr[1] = subid - 80;
}
*len = 2;
optr += 2;
while (ctx->pointer < eoc) {
if (++(*len) > size) {
ctx->error = ASN1_ERR_DEC_BADVALUE;
kfree(*oid);
*oid = NULL;
return 0;
}
if (!asn1_subid_decode(ctx, optr++)) {
kfree(*oid);
*oid = NULL;
return 0;
}
}
return 1;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 252 | 91.64% | 1 | 33.33% |
Chris Wright | 20 | 7.27% | 1 | 33.33% |
David Howells | 3 | 1.09% | 1 | 33.33% |
Total | 275 | 100.00% | 3 | 100.00% |
/*****************************************************************************
*
* SNMP decoding routines (gxsnmp author Dirk Wisse)
*
*****************************************************************************/
/* SNMP Versions */
#define SNMP_V1 0
#define SNMP_V2C 1
#define SNMP_V2 2
#define SNMP_V3 3
/* Default Sizes */
#define SNMP_SIZE_COMM 256
#define SNMP_SIZE_OBJECTID 128
#define SNMP_SIZE_BUFCHR 256
#define SNMP_SIZE_BUFINT 128
#define SNMP_SIZE_SMALLOBJECTID 16
/* Requests */
#define SNMP_PDU_GET 0
#define SNMP_PDU_NEXT 1
#define SNMP_PDU_RESPONSE 2
#define SNMP_PDU_SET 3
#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
#define SNMP_WRONGENCODING 9
#define SNMP_WRONGVALUE 10
#define SNMP_NOCREATION 11
#define SNMP_INCONSISTENTVALUE 12
#define SNMP_RESOURCEUNAVAILABLE 13
#define SNMP_COMMITFAILED 14
#define SNMP_UNDOFAILED 15
#define SNMP_AUTHORIZATIONERROR 16
#define SNMP_NOTWRITABLE 17
#define SNMP_INCONSISTENTNAME 18
/* 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
#define SNMP_TRAP_ENTSPECIFIC 6
/* 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;
}
Contributors
Person | Tokens | Prop | Commits | CommitProp |
Patrick McHardy | 72 | 98.63% | 1 | 50.00% |
Jan Engelhardt | 1 | 1.37% | 1 | 50.00% |
Total | 73 | 100.00% | 2 | 100.00% |
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);
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);
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 (*