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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [net/] [ipv4/] [netfilter/] [ip_nat_snmp_basic.c] - Blame information for rev 1765

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/*
 * ip_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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * Author: James Morris <jmorris@intercode.com.au>
 *
 * Updates:
 * 2000-08-06: Convert to new helper API (Harald Welte).
 *
 */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_nat.h>
#include <linux/netfilter_ipv4/ip_nat_helper.h>
#include <linux/brlock.h>
#include <linux/types.h>
#include <linux/ip.h>
#include <net/checksum.h>
#include <net/udp.h>
#include <asm/uaccess.h>
 
 
 
#define SNMP_PORT 161
#define SNMP_TRAP_PORT 162
#define NOCT1(n) (u_int8_t )((n) & 0xff)
 
static int debug = 0;
static spinlock_t snmp_lock = SPIN_LOCK_UNLOCKED;
 
/*
 * 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;
}
 
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;
}
 
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;
}
 
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;
}
 
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 = (unsigned char) (ch & 0x7F);
                        *len = 0;
 
                        while (cnt > 0) {
                                if (!asn1_octet_decode(ctx, &ch))
                                        return 0;
                                *len <<= 8;
                                *len |= ch;
                                cnt--;
                        }
                }
        }
        return 1;
}
 
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;
 
        if (!asn1_length_decode(ctx, &def, &len))
                return 0;
 
        if (def)
                *eoc = ctx->pointer + len;
        else
                *eoc = 0;
        return 1;
}
 
static unsigned char asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
{
        unsigned char ch;
 
        if (eoc == 0) {
                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;
        }
}
 
static unsigned char asn1_null_decode(struct asn1_ctx *ctx, unsigned char *eoc)
{
        ctx->pointer = eoc;
        return 1;
}
 
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;
}
 
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;
}
 
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;
}
 
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) {
                if (net_ratelimit())
                        printk("OOM in bsalg (%d)\n", __LINE__);
                return 0;
        }
 
        ptr = *octets;
        while (ctx->pointer < eoc) {
                if (!asn1_octet_decode(ctx, (unsigned char *)ptr++)) {
                        kfree(*octets);
                        *octets = NULL;
                        return 0;
                }
                (*len)++;
        }
        return 1;
}
 
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;
}
 
static unsigned char asn1_oid_decode(struct asn1_ctx *ctx,
                                     unsigned char *eoc,
                                     unsigned long **oid,
                                     unsigned int *len)
{
        unsigned long subid;
        unsigned int  size;
        unsigned long *optr;
 
        size = eoc - ctx->pointer + 1;
        *oid = kmalloc(size * sizeof(unsigned long), GFP_ATOMIC);
        if (*oid == NULL) {
                if (net_ratelimit())
                        printk("OOM in bsalg (%d)\n", __LINE__);
                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;
}
 
/*****************************************************************************
 *
 * 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 void inline mangle_address(unsigned char *begin,
                                  unsigned char *addr,
                                  const struct oct1_map *map,
                                  u_int16_t *check);
struct snmp_cnv
{
        unsigned int class;
        unsigned int tag;
        int syntax;
};
 
static 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)
{
        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;
        }
 
        if (!snmp_tag_cls2syntax(tag, cls, &type)) {
                kfree(id);
                return 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(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(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;
}
 
static unsigned char snmp_trap_decode(struct asn1_ctx *ctx,
                                      struct snmp_v1_trap *trap,
                                      const struct oct1_map *map,
                                      u_int16_t *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_id_free:
        kfree(trap->id);
 
err_addr_free:
        kfree((unsigned long *)trap->ip_address);
 
        return 0;
}
 
/*****************************************************************************
 *
 * Misc. routines
 *
 *****************************************************************************/
 
static void hex_dump(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");
}
 
/*
 * Fast checksum update for possibly oddly-aligned UDP byte, from the
 * code example in the draft.
 */
static void fast_csum(unsigned char *csum,
                      const unsigned char *optr,
                      const unsigned char *nptr,
                      int odd)
{
        long x, old, new;
 
        x = csum[0] * 256 + csum[1];
 
        x =~ x & 0xFFFF;
 
        if (odd) old = optr[0] * 256;
        else old = optr[0];
 
        x -= old & 0xFFFF;
        if (x <= 0) {
                x--;
                x &= 0xFFFF;
        }
 
        if (odd) new = nptr[0] * 256;
        else new = nptr[0];
 
        x += new & 0xFFFF;
        if (x & 0x10000) {
                x++;
                x &= 0xFFFF;
        }
 
        x =~ x & 0xFFFF;
        csum[0] = x / 256;
        csum[1] = x & 0xFF;
}
 
/*
 * Mangle IP address.
 *      - begin points to the start of the snmp messgae
 *      - addr points to the start of the address
 */
static void inline mangle_address(unsigned char *begin,
                                  unsigned char *addr,
                                  const struct oct1_map *map,
                                  u_int16_t *check)
{
        if (map->from == NOCT1(*addr)) {
                u_int32_t old;
 
                if (debug)
                        memcpy(&old, (unsigned char *)addr, sizeof(old));
 
                *addr = map->to;
 
                /* Update UDP checksum if being used */
                if (*check) {
                        unsigned char odd = !((addr - begin) % 2);
 
                        fast_csum((unsigned char *)check,
                                  &map->from, &map->to, odd);
 
                }
 
                if (debug)
                        printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
                               "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
        }
}
 
/*
 * 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,
                             u_int16_t *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) {
                unsigned char *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);
 
                /* Discard trap allocations regardless */
                kfree(trap.id);
                kfree((unsigned long *)trap.ip_address);
 
                if (!ret)
                        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) {
                                if ((*obj)->id)
                                        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 ip_conntrack *ct,
                          struct ip_nat_info *info,
                          enum ip_conntrack_info ctinfo,
                          unsigned int hooknum,
                          struct sk_buff **pskb)
{
        struct iphdr *iph = (*pskb)->nh.iph;
        struct udphdr *udph = (struct udphdr *)((u_int32_t *)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[IP_CT_DIR_ORIGINAL].tuple.src.ip);
                map.to = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip);
        } else {
                /* DNAT replies */
                map.from = NOCT1(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
                map.to = NOCT1(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip);
        }
 
        if (map.from == map.to)
                return NF_ACCEPT;
 
        if (!snmp_parse_mangle((unsigned char *)udph + sizeof(struct udphdr),
                               paylen, &map, &udph->check)) {
                printk(KERN_WARNING "bsalg: parser failed\n");
                return NF_DROP;
        }
        return NF_ACCEPT;
}
 
/*
 * NAT helper function, packets arrive here from NAT code.
 */
static unsigned int nat_help(struct ip_conntrack *ct,
                             struct ip_conntrack_expect *exp,
                             struct ip_nat_info *info,
                             enum ip_conntrack_info ctinfo,
                             unsigned int hooknum,
                             struct sk_buff **pskb)
{
        int dir = CTINFO2DIR(ctinfo);
        struct iphdr *iph = (*pskb)->nh.iph;
        struct udphdr *udph = (struct udphdr *)((u_int32_t *)iph + iph->ihl);
 
        spin_lock_bh(&snmp_lock);
 
        /*
         * Translate snmp replies on pre-routing (DNAT) and snmp traps
         * on post routing (SNAT).
         */
        if (!((dir == IP_CT_DIR_REPLY && hooknum == NF_IP_PRE_ROUTING &&
                        udph->source == ntohs(SNMP_PORT)) ||
              (dir == IP_CT_DIR_ORIGINAL && hooknum == NF_IP_POST_ROUTING &&
                        udph->dest == ntohs(SNMP_TRAP_PORT)))) {
                spin_unlock_bh(&snmp_lock);
                return NF_ACCEPT;
        }
 
        if (debug > 1) {
                printk(KERN_DEBUG "bsalg: dir=%s hook=%d manip=%s len=%d "
                       "src=%u.%u.%u.%u:%u dst=%u.%u.%u.%u:%u "
                       "osrc=%u.%u.%u.%u odst=%u.%u.%u.%u "
                       "rsrc=%u.%u.%u.%u rdst=%u.%u.%u.%u "
                       "\n",
                       dir == IP_CT_DIR_REPLY ? "reply" : "orig", hooknum,
                       HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC ? "snat" :
                       "dnat", (*pskb)->len,
                       NIPQUAD(iph->saddr), ntohs(udph->source),
                       NIPQUAD(iph->daddr), ntohs(udph->dest),
                       NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip),
                       NIPQUAD(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip),
                       NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip),
                       NIPQUAD(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip));
        }
 
        /*
         * 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) == (*pskb)->len - (iph->ihl << 2)) {
                int ret = snmp_translate(ct, info, ctinfo, hooknum, pskb);
                spin_unlock_bh(&snmp_lock);
                return ret;
        }
 
        if (net_ratelimit())
                printk(KERN_WARNING "bsalg: dropping malformed packet "
                       "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
                       NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
        spin_unlock_bh(&snmp_lock);
        return NF_DROP;
}
 
static struct ip_nat_helper snmp = {
        { NULL, NULL },
        "snmp",
        IP_NAT_HELPER_F_STANDALONE,
        THIS_MODULE,
        { { 0, { .udp = { __constant_htons(SNMP_PORT) } } },
          { 0, { 0 }, IPPROTO_UDP } },
        { { 0, { .udp = { 0xFFFF } } },
          { 0, { 0 }, 0xFFFF } },
        nat_help, NULL };
 
static struct ip_nat_helper snmp_trap = {
        { NULL, NULL },
        "snmp_trap",
        IP_NAT_HELPER_F_STANDALONE,
        THIS_MODULE,
        { { 0, { .udp = { __constant_htons(SNMP_TRAP_PORT) } } },
          { 0, { 0 }, IPPROTO_UDP } },
        { { 0, { .udp = { 0xFFFF } } },
          { 0, { 0 }, 0xFFFF } },
        nat_help, NULL };
 
/*****************************************************************************
 *
 * Module stuff.
 *
 *****************************************************************************/
 
static int __init init(void)
{
        int ret = 0;
 
        ret = ip_nat_helper_register(&snmp);
        if (ret < 0)
                return ret;
        ret = ip_nat_helper_register(&snmp_trap);
        if (ret < 0) {
                ip_nat_helper_unregister(&snmp);
                return ret;
        }
        return ret;
}
 
static void __exit fini(void)
{
        ip_nat_helper_unregister(&snmp);
        ip_nat_helper_unregister(&snmp_trap);
        br_write_lock_bh(BR_NETPROTO_LOCK);
        br_write_unlock_bh(BR_NETPROTO_LOCK);
}
 
module_init(init);
module_exit(fini);
 
MODULE_PARM(debug, "i");
MODULE_DESCRIPTION("Basic SNMP Application Layer Gateway");
MODULE_LICENSE("GPL");
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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [net/] [ipv4/] [netfilter/] [ip_nat_snmp_basic.c] - Blame information for rev 1765

Line No.	Rev	Author	Line
1	1275	phoenix	`/*`
2			`* ip_nat_snmp_basic.c`
3			`*`
4			`* Basic SNMP Application Layer Gateway`
5			`*`
6			`* This IP NAT module is intended for use with SNMP network`
7			`* discovery and monitoring applications where target networks use`
8			`* conflicting private address realms.`
9			`*`
10			`* Static NAT is used to remap the networks from the view of the network`
11			`* management system at the IP layer, and this module remaps some application`
12			`* layer addresses to match.`
13			`*`
14			`* The simplest form of ALG is performed, where only tagged IP addresses`
15			`* are modified. The module does not need to be MIB aware and only scans`
16			`* messages at the ASN.1/BER level.`
17			`*`
18			`* Currently, only SNMPv1 and SNMPv2 are supported.`
19			`*`
20			`* More information on ALG and associated issues can be found in`
21			`* RFC 2962`
22			`*`
23			`* The ASB.1/BER parsing code is derived from the gxsnmp package by Gregory`
24			`* McLean & Jochen Friedrich, stripped down for use in the kernel.`
25			`*`
26			`* Copyright (c) 2000 RP Internet (www.rpi.net.au).`
27			`*`
28			`* This program is free software; you can redistribute it and/or modify`
29			`* it under the terms of the GNU General Public License as published by`
30			`* the Free Software Foundation; either version 2 of the License, or`
31			`* (at your option) any later version.`
32			`* This program is distributed in the hope that it will be useful,`
33			`* but WITHOUT ANY WARRANTY; without even the implied warranty of`
34			`* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the`
35			`* GNU General Public License for more details.`
36			`* You should have received a copy of the GNU General Public License`
37			`* along with this program; if not, write to the Free Software`
38			`* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA`
39			`*`
40			`* Author: James Morris <jmorris@intercode.com.au>`