nf_conntrack_h323_asn1.c

linux 内核源代码

/****************************************************************************
 * ip_conntrack_helper_h323_asn1.c - BER and PER decoding library for H.323
 * 			      	     conntrack/NAT module.
 *
 * Copyright (c) 2006 by Jing Min Zhao <[e-mail]>
 *
 * This source code is licensed under General Public License version 2.
 *
 * See ip_conntrack_helper_h323_asn1.h for details.
 *
 ****************************************************************************/

#ifdef __KERNEL__
#include <linux/kernel.h>
#else
#include <stdio.h>
#endif
#include <linux/netfilter/nf_conntrack_h323_asn1.h>

/* Trace Flag */
#ifndef H323_TRACE
#define H323_TRACE 0
#endif

#if H323_TRACE
#define TAB_SIZE 4
#define IFTHEN(cond, act) if(cond){act;}
#ifdef __KERNEL__
#define PRINT printk
#else
#define PRINT printf
#endif
#define FNAME(name) name,
#else
#define IFTHEN(cond, act)
#define PRINT(fmt, args...)
#define FNAME(name)
#endif

/* ASN.1 Types */
#define NUL 0
#define BOOL 1
#define OID 2
#define INT 3
#define ENUM 4
#define BITSTR 5
#define NUMSTR 6
#define NUMDGT 6
#define TBCDSTR 6
#define OCTSTR 7
#define PRTSTR 7
#define IA5STR 7
#define GENSTR 7
#define BMPSTR 8
#define SEQ 9
#define SET 9
#define SEQOF 10
#define SETOF 10
#define CHOICE 11

/* Constraint Types */
#define FIXD 0
/* #define BITS 1-8 */
#define BYTE 9
#define WORD 10
#define CONS 11
#define SEMI 12
#define UNCO 13

/* ASN.1 Type Attributes */
#define SKIP 0
#define STOP 1
#define DECODE 2
#define EXT 4
#define OPEN 8
#define OPT 16


/* ASN.1 Field Structure */
typedef struct field_t {
#if H323_TRACE
	char *name;
#endif
	unsigned char type;
	unsigned char sz;
	unsigned char lb;
	unsigned char ub;
	unsigned short attr;
	unsigned short offset;
	struct field_t *fields;
} field_t;

/* Bit Stream */
typedef struct {
	unsigned char *buf;
	unsigned char *beg;
	unsigned char *end;
	unsigned char *cur;
	unsigned bit;
} bitstr_t;

/* Tool Functions */
#define INC_BIT(bs) if((++bs->bit)>7){bs->cur++;bs->bit=0;}
#define INC_BITS(bs,b) if((bs->bit+=b)>7){bs->cur+=bs->bit>>3;bs->bit&=7;}
#define BYTE_ALIGN(bs) if(bs->bit){bs->cur++;bs->bit=0;}
#define CHECK_BOUND(bs,n) if(bs->cur+(n)>bs->end)return(H323_ERROR_BOUND)
static unsigned get_len(bitstr_t * bs);
static unsigned get_bit(bitstr_t * bs);
static unsigned get_bits(bitstr_t * bs, unsigned b);
static unsigned get_bitmap(bitstr_t * bs, unsigned b);
static unsigned get_uint(bitstr_t * bs, int b);

/* Decoder Functions */
static int decode_nul(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_bool(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_oid(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_int(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_enum(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_bitstr(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_numstr(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_octstr(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_bmpstr(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_seq(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_seqof(bitstr_t * bs, field_t * f, char *base, int level);
static int decode_choice(bitstr_t * bs, field_t * f, char *base, int level);

/* Decoder Functions Vector */
typedef int (*decoder_t) (bitstr_t *, field_t *, char *, int);
static decoder_t Decoders[] = {
	decode_nul,
	decode_bool,
	decode_oid,
	decode_int,
	decode_enum,
	decode_bitstr,
	decode_numstr,
	decode_octstr,
	decode_bmpstr,
	decode_seq,
	decode_seqof,
	decode_choice,
};

/****************************************************************************
 * H.323 Types
 ****************************************************************************/
#include "nf_conntrack_h323_types.c"

/****************************************************************************
 * Functions
 ****************************************************************************/
/* Assume bs is aligned && v < 16384 */
unsigned get_len(bitstr_t * bs)
{
	unsigned v;

	v = *bs->cur++;

	if (v & 0x80) {
		v &= 0x3f;
		v <<= 8;
		v += *bs->cur++;
	}

	return v;
}

/****************************************************************************/
unsigned get_bit(bitstr_t * bs)
{
	unsigned b = (*bs->cur) & (0x80 >> bs->bit);

	INC_BIT(bs);

	return b;
}

/****************************************************************************/
/* Assume b <= 8 */
unsigned get_bits(bitstr_t * bs, unsigned b)
{
	unsigned v, l;

	v = (*bs->cur) & (0xffU >> bs->bit);
	l = b + bs->bit;

	if (l < 8) {
		v >>= 8 - l;
		bs->bit = l;
	} else if (l == 8) {
		bs->cur++;
		bs->bit = 0;
	} else {		/* l > 8 */

		v <<= 8;
		v += *(++bs->cur);
		v >>= 16 - l;
		bs->bit = l - 8;
	}

	return v;
}

/****************************************************************************/
/* Assume b <= 32 */
unsigned get_bitmap(bitstr_t * bs, unsigned b)
{
	unsigned v, l, shift, bytes;

	if (!b)
		return 0;

	l = bs->bit + b;

	if (l < 8) {
		v = (unsigned) (*bs->cur) << (bs->bit + 24);
		bs->bit = l;
	} else if (l == 8) {
		v = (unsigned) (*bs->cur++) << (bs->bit + 24);
		bs->bit = 0;
	} else {
		for (bytes = l >> 3, shift = 24, v = 0; bytes;
		     bytes--, shift -= 8)
			v |= (unsigned) (*bs->cur++) << shift;

		if (l < 32) {
			v |= (unsigned) (*bs->cur) << shift;
			v <<= bs->bit;
		} else if (l > 32) {
			v <<= bs->bit;
			v |= (*bs->cur) >> (8 - bs->bit);
		}

		bs->bit = l & 0x7;
	}

	v &= 0xffffffff << (32 - b);

	return v;
}

/****************************************************************************
 * Assume bs is aligned and sizeof(unsigned int) == 4
 ****************************************************************************/
unsigned get_uint(bitstr_t * bs, int b)
{
	unsigned v = 0;

	switch (b) {
	case 4:
		v |= *bs->cur++;
		v <<= 8;
	case 3:
		v |= *bs->cur++;
		v <<= 8;
	case 2:
		v |= *bs->cur++;
		v <<= 8;
	case 1:
		v |= *bs->cur++;
		break;
	}
	return v;
}

/****************************************************************************/
int decode_nul(bitstr_t * bs, field_t * f, char *base, int level)
{
	PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);

	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_bool(bitstr_t * bs, field_t * f, char *base, int level)
{
	PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);

	INC_BIT(bs);

	CHECK_BOUND(bs, 0);
	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_oid(bitstr_t * bs, field_t * f, char *base, int level)
{
	int len;

	PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);

	BYTE_ALIGN(bs);
	CHECK_BOUND(bs, 1);
	len = *bs->cur++;
	bs->cur += len;

	CHECK_BOUND(bs, 0);
	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_int(bitstr_t * bs, field_t * f, char *base, int level)
{
	unsigned len;

	PRINT("%*.s%s", level * TAB_SIZE, " ", f->name);

	switch (f->sz) {
	case BYTE:		/* Range == 256 */
		BYTE_ALIGN(bs);
		bs->cur++;
		break;
	case WORD:		/* 257 <= Range <= 64K */
		BYTE_ALIGN(bs);
		bs->cur += 2;
		break;
	case CONS:		/* 64K < Range < 4G */
		len = get_bits(bs, 2) + 1;
		BYTE_ALIGN(bs);
		if (base && (f->attr & DECODE)) {	/* timeToLive */
			unsigned v = get_uint(bs, len) + f->lb;
			PRINT(" = %u", v);
			*((unsigned *) (base + f->offset)) = v;
		}
		bs->cur += len;
		break;
	case UNCO:
		BYTE_ALIGN(bs);
		CHECK_BOUND(bs, 2);
		len = get_len(bs);
		bs->cur += len;
		break;
	default:		/* 2 <= Range <= 255 */
		INC_BITS(bs, f->sz);
		break;
	}

	PRINT("\n");

	CHECK_BOUND(bs, 0);
	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_enum(bitstr_t * bs, field_t * f, char *base, int level)
{
	PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);

	if ((f->attr & EXT) && get_bit(bs)) {
		INC_BITS(bs, 7);
	} else {
		INC_BITS(bs, f->sz);
	}

	CHECK_BOUND(bs, 0);
	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_bitstr(bitstr_t * bs, field_t * f, char *base, int level)
{
	unsigned len;

	PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);

	BYTE_ALIGN(bs);
	switch (f->sz) {
	case FIXD:		/* fixed length > 16 */
		len = f->lb;
		break;
	case WORD:		/* 2-byte length */
		CHECK_BOUND(bs, 2);
		len = (*bs->cur++) << 8;
		len += (*bs->cur++) + f->lb;
		break;
	case SEMI:
		CHECK_BOUND(bs, 2);
		len = get_len(bs);
		break;
	default:
		len = 0;
		break;
	}

	bs->cur += len >> 3;
	bs->bit = len & 7;

	CHECK_BOUND(bs, 0);
	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_numstr(bitstr_t * bs, field_t * f, char *base, int level)
{
	unsigned len;

	PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);

	/* 2 <= Range <= 255 */
	len = get_bits(bs, f->sz) + f->lb;

	BYTE_ALIGN(bs);
	INC_BITS(bs, (len << 2));

	CHECK_BOUND(bs, 0);
	return H323_ERROR_NONE;
}

/****************************************************************************/
int decode_octstr(bitstr_t * bs, field_t * f, char *base, int level)
{
	unsigned len;

	PRINT("%*.s%s", level * TAB_SIZE, " ", f->name);

	switch (f->sz) {
	case FIXD:		/* Range == 1 */
		if (f->lb > 2) {
			BYTE_ALIGN(bs);
			if (base && (f->attr & DECODE)) {
				/* The IP Address */
				IFTHEN(f->lb == 4,
				       PRINT(" = %d.%d.%d.%d:%d",
					     bs->cur[0], bs->cur[1],
					     bs->cur[2], bs->cur[3],
					     bs->cur[4] * 256 + bs->cur[5]));
				*((unsigned *) (base + f->offset)) =
				    bs->cur - bs->buf;
			}
		}
		len = f->lb;
		break;
	case BYTE:		/* Range == 256 */
		BYTE_ALIGN(bs);
		CHECK_BOUND(bs, 1);
		len = (*bs->cur++) + f->lb;
		break;
	case SEMI:
		BYTE_ALIGN(bs);