--- /dev/null
+/*
+ * 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, 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/module.h>
+#include <linux/moduleparam.h>
+#include <linux/types.h>
+#include <linux/kernel.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_helper.h>
+#include <net/netfilter/nf_nat_helper.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;
+}
+
+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;
+
+ def = len = 0;
+ if (!asn1_length_decode(ctx, &def, &len))
+ return 0;
+
+ if (def)
+ *eoc = ctx->pointer + len;
+ else
+ *eoc = NULL;
+ 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 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 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;
+ }
+
+ 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(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, (unsigned char *)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 %u.%u.%u.%u to "
+ "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*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(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) {
+ 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);
+
+ 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 **pskb)
+{
+ struct iphdr *iph = (*pskb)->nh.iph;
+ 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 **pskb, unsigned int protoff,
+ struct nf_conn *ct,
+ enum ip_conntrack_info ctinfo)
+{
+ int dir = CTINFO2DIR(ctinfo);
+ unsigned int ret;
+ struct iphdr *iph = (*pskb)->nh.iph;
+ struct udphdr *udph = (struct udphdr *)((u_int32_t *)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) != (*pskb)->len - (iph->ihl << 2)) {
+ if (net_ratelimit())
+ printk(KERN_WARNING "SNMP: dropping malformed packet "
+ "src=%u.%u.%u.%u dst=%u.%u.%u.%u\n",
+ NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));
+ return NF_DROP;
+ }
+
+ if (!skb_make_writable(pskb, (*pskb)->len))
+ return NF_DROP;
+
+ spin_lock_bh(&snmp_lock);
+ ret = snmp_translate(ct, ctinfo, pskb);
+ spin_unlock_bh(&snmp_lock);
+ return ret;
+}
+
+static struct nf_conntrack_helper snmp_helper __read_mostly = {
+ .max_expected = 0,
+ .timeout = 180,
+ .me = THIS_MODULE,
+ .help = help,
+ .name = "snmp",
+ .tuple.src.l3num = AF_INET,
+ .tuple.src.u.udp.port = __constant_htons(SNMP_PORT),
+ .tuple.dst.protonum = IPPROTO_UDP,
+ .mask.src.l3num = 0xFFFF,
+ .mask.src.u.udp.port = __constant_htons(0xFFFF),
+ .mask.dst.protonum = 0xFF,
+};
+
+static struct nf_conntrack_helper snmp_trap_helper __read_mostly = {
+ .max_expected = 0,
+ .timeout = 180,
+ .me = THIS_MODULE,
+ .help = help,
+ .name = "snmp_trap",
+ .tuple.src.l3num = AF_INET,
+ .tuple.src.u.udp.port = __constant_htons(SNMP_TRAP_PORT),
+ .tuple.dst.protonum = IPPROTO_UDP,
+ .mask.src.l3num = 0xFFFF,
+ .mask.src.u.udp.port = __constant_htons(0xFFFF),
+ .mask.dst.protonum = 0xFF,
+};
+
+/*****************************************************************************
+ *
+ * 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);
projects / linux-2.6 / commitdiff