/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- get_len
- get_bit
- get_bits
- get_bitmap
- get_uint
- decode_nul
- decode_bool
- decode_oid
- decode_int
- decode_enum
- decode_bitstr
- decode_numstr
- decode_octstr
- decode_bmpstr
- decode_seq
- decode_seqof
- decode_choice
- DecodeRasMessage
- DecodeH323_UserInformation
- DecodeMultimediaSystemControlMessage
- DecodeQ931
/****************************************************************************
* ip_conntrack_helper_h323_asn1.c - BER and PER decoding library for H.323
* conntrack/NAT module.
*
* Copyright (c) 2006 by Jing Min Zhao <zhaojingmin@users.sourceforge.net>
*
* 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;
const struct field_t *fields;
} field_t;
/* Bit Stream */
typedef struct {
unsigned char *buf;
unsigned char *beg;
unsigned char *end;
unsigned char *cur;
unsigned int 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 int get_len(bitstr_t *bs);
static unsigned int get_bit(bitstr_t *bs);
static unsigned int get_bits(bitstr_t *bs, unsigned int b);
static unsigned int get_bitmap(bitstr_t *bs, unsigned int b);
static unsigned int get_uint(bitstr_t *bs, int b);
/* Decoder Functions */
static int decode_nul(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_bool(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_oid(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_int(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_enum(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_bitstr(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_numstr(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_octstr(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_bmpstr(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_seq(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_seqof(bitstr_t *bs, const struct field_t *f, char *base, int level);
static int decode_choice(bitstr_t *bs, const struct field_t *f, char *base, int level);
/* Decoder Functions Vector */
typedef int (*decoder_t)(bitstr_t *, const struct field_t *, char *, int);
static const 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 */
static unsigned int get_len(bitstr_t *bs)
{
unsigned int v;
v = *bs->cur++;
if (v & 0x80) {
v &= 0x3f;
v <<= 8;
v += *bs->cur++;
}
return v;
}
/****************************************************************************/
static unsigned int get_bit(bitstr_t *bs)
{
unsigned int b = (*bs->cur) & (0x80 >> bs->bit);
INC_BIT(bs);
return b;
}
/****************************************************************************/
/* Assume b <= 8 */
static unsigned int get_bits(bitstr_t *bs, unsigned int b)
{
unsigned int 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 */
static unsigned int get_bitmap(bitstr_t *bs, unsigned int b)
{
unsigned int v, l, shift, bytes;
if (!b)
return 0;
l = bs->bit + b;
if (l < 8) {
v = (unsigned int)(*bs->cur) << (bs->bit + 24);
bs->bit = l;
} else if (l == 8) {
v = (unsigned int)(*bs->cur++) << (bs->bit + 24);
bs->bit = 0;
} else {
for (bytes = l >> 3, shift = 24, v = 0; bytes;
bytes--, shift -= 8)
v |= (unsigned int)(*bs->cur++) << shift;
if (l < 32) {
v |= (unsigned int)(*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
****************************************************************************/
static unsigned int get_uint(bitstr_t *bs, int b)
{
unsigned int 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;
}
/****************************************************************************/
static int decode_nul(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);
return H323_ERROR_NONE;
}
/****************************************************************************/
static int decode_bool(bitstr_t *bs, const struct 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;
}
/****************************************************************************/
static int decode_oid(bitstr_t *bs, const struct 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;
}
/****************************************************************************/
static int decode_int(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int 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 int v = get_uint(bs, len) + f->lb;
PRINT(" = %u", v);
*((unsigned int *)(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;
}
/****************************************************************************/
static int decode_enum(bitstr_t *bs, const struct 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;
}
/****************************************************************************/
static int decode_bitstr(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int 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;
}
/****************************************************************************/
static int decode_numstr(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int 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;
}
/****************************************************************************/
static int decode_octstr(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int 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 int *)(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);
CHECK_BOUND(bs, 2);
len = get_len(bs) + f->lb;
break;
default: /* 2 <= Range <= 255 */
len = get_bits(bs, f->sz) + f->lb;
BYTE_ALIGN(bs);
break;
}
bs->cur += len;
PRINT("\n");
CHECK_BOUND(bs, 0);
return H323_ERROR_NONE;
}
/****************************************************************************/
static int decode_bmpstr(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int len;
PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);
switch (f->sz) {
case BYTE: /* Range == 256 */
BYTE_ALIGN(bs);
CHECK_BOUND(bs, 1);
len = (*bs->cur++) + f->lb;
break;
default: /* 2 <= Range <= 255 */
len = get_bits(bs, f->sz) + f->lb;
BYTE_ALIGN(bs);
break;
}
bs->cur += len << 1;
CHECK_BOUND(bs, 0);
return H323_ERROR_NONE;
}
/****************************************************************************/
static int decode_seq(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int ext, bmp, i, opt, len = 0, bmp2, bmp2_len;
int err;
const struct field_t *son;
unsigned char *beg = NULL;
PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);
/* Decode? */
base = (base && (f->attr & DECODE)) ? base + f->offset : NULL;
/* Extensible? */
ext = (f->attr & EXT) ? get_bit(bs) : 0;
/* Get fields bitmap */
bmp = get_bitmap(bs, f->sz);
if (base)
*(unsigned int *)base = bmp;
/* Decode the root components */
for (i = opt = 0, son = f->fields; i < f->lb; i++, son++) {
if (son->attr & STOP) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE, " ",
son->name);
return H323_ERROR_STOP;
}
if (son->attr & OPT) { /* Optional component */
if (!((0x80000000U >> (opt++)) & bmp)) /* Not exist */
continue;
}
/* Decode */
if (son->attr & OPEN) { /* Open field */
CHECK_BOUND(bs, 2);
len = get_len(bs);
CHECK_BOUND(bs, len);
if (!base || !(son->attr & DECODE)) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE,
" ", son->name);
bs->cur += len;
continue;
}
beg = bs->cur;
/* Decode */
if ((err = (Decoders[son->type]) (bs, son, base,
level + 1)) <
H323_ERROR_NONE)
return err;
bs->cur = beg + len;
bs->bit = 0;
} else if ((err = (Decoders[son->type]) (bs, son, base,
level + 1)) <
H323_ERROR_NONE)
return err;
}
/* No extension? */
if (!ext)
return H323_ERROR_NONE;
/* Get the extension bitmap */
bmp2_len = get_bits(bs, 7) + 1;
CHECK_BOUND(bs, (bmp2_len + 7) >> 3);
bmp2 = get_bitmap(bs, bmp2_len);
bmp |= bmp2 >> f->sz;
if (base)
*(unsigned int *)base = bmp;
BYTE_ALIGN(bs);
/* Decode the extension components */
for (opt = 0; opt < bmp2_len; opt++, i++, son++) {
/* Check Range */
if (i >= f->ub) { /* Newer Version? */
CHECK_BOUND(bs, 2);
len = get_len(bs);
CHECK_BOUND(bs, len);
bs->cur += len;
continue;
}
if (son->attr & STOP) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE, " ",
son->name);
return H323_ERROR_STOP;
}
if (!((0x80000000 >> opt) & bmp2)) /* Not present */
continue;
CHECK_BOUND(bs, 2);
len = get_len(bs);
CHECK_BOUND(bs, len);
if (!base || !(son->attr & DECODE)) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE, " ",
son->name);
bs->cur += len;
continue;
}
beg = bs->cur;
if ((err = (Decoders[son->type]) (bs, son, base,
level + 1)) <
H323_ERROR_NONE)
return err;
bs->cur = beg + len;
bs->bit = 0;
}
return H323_ERROR_NONE;
}
/****************************************************************************/
static int decode_seqof(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int count, effective_count = 0, i, len = 0;
int err;
const struct field_t *son;
unsigned char *beg = NULL;
PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);
/* Decode? */
base = (base && (f->attr & DECODE)) ? base + f->offset : NULL;
/* Decode item count */
switch (f->sz) {
case BYTE:
BYTE_ALIGN(bs);
CHECK_BOUND(bs, 1);
count = *bs->cur++;
break;
case WORD:
BYTE_ALIGN(bs);
CHECK_BOUND(bs, 2);
count = *bs->cur++;
count <<= 8;
count = *bs->cur++;
break;
case SEMI:
BYTE_ALIGN(bs);
CHECK_BOUND(bs, 2);
count = get_len(bs);
break;
default:
count = get_bits(bs, f->sz);
break;
}
count += f->lb;
/* Write Count */
if (base) {
effective_count = count > f->ub ? f->ub : count;
*(unsigned int *)base = effective_count;
base += sizeof(unsigned int);
}
/* Decode nested field */
son = f->fields;
if (base)
base -= son->offset;
for (i = 0; i < count; i++) {
if (son->attr & OPEN) {
BYTE_ALIGN(bs);
len = get_len(bs);
CHECK_BOUND(bs, len);
if (!base || !(son->attr & DECODE)) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE,
" ", son->name);
bs->cur += len;
continue;
}
beg = bs->cur;
if ((err = (Decoders[son->type]) (bs, son,
i <
effective_count ?
base : NULL,
level + 1)) <
H323_ERROR_NONE)
return err;
bs->cur = beg + len;
bs->bit = 0;
} else
if ((err = (Decoders[son->type]) (bs, son,
i <
effective_count ?
base : NULL,
level + 1)) <
H323_ERROR_NONE)
return err;
if (base)
base += son->offset;
}
return H323_ERROR_NONE;
}
/****************************************************************************/
static int decode_choice(bitstr_t *bs, const struct field_t *f,
char *base, int level)
{
unsigned int type, ext, len = 0;
int err;
const struct field_t *son;
unsigned char *beg = NULL;
PRINT("%*.s%s\n", level * TAB_SIZE, " ", f->name);
/* Decode? */
base = (base && (f->attr & DECODE)) ? base + f->offset : NULL;
/* Decode the choice index number */
if ((f->attr & EXT) && get_bit(bs)) {
ext = 1;
type = get_bits(bs, 7) + f->lb;
} else {
ext = 0;
type = get_bits(bs, f->sz);
if (type >= f->lb)
return H323_ERROR_RANGE;
}
/* Write Type */
if (base)
*(unsigned int *)base = type;
/* Check Range */
if (type >= f->ub) { /* Newer version? */
BYTE_ALIGN(bs);
len = get_len(bs);
CHECK_BOUND(bs, len);
bs->cur += len;
return H323_ERROR_NONE;
}
/* Transfer to son level */
son = &f->fields[type];
if (son->attr & STOP) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE, " ", son->name);
return H323_ERROR_STOP;
}
if (ext || (son->attr & OPEN)) {
BYTE_ALIGN(bs);
len = get_len(bs);
CHECK_BOUND(bs, len);
if (!base || !(son->attr & DECODE)) {
PRINT("%*.s%s\n", (level + 1) * TAB_SIZE, " ",
son->name);
bs->cur += len;
return H323_ERROR_NONE;
}
beg = bs->cur;
if ((err = (Decoders[son->type]) (bs, son, base, level + 1)) <
H323_ERROR_NONE)
return err;
bs->cur = beg + len;
bs->bit = 0;
} else if ((err = (Decoders[son->type]) (bs, son, base, level + 1)) <
H323_ERROR_NONE)
return err;
return H323_ERROR_NONE;
}
/****************************************************************************/
int DecodeRasMessage(unsigned char *buf, size_t sz, RasMessage *ras)
{
static const struct field_t ras_message = {
FNAME("RasMessage") CHOICE, 5, 24, 32, DECODE | EXT,
0, _RasMessage
};
bitstr_t bs;
bs.buf = bs.beg = bs.cur = buf;
bs.end = buf + sz;
bs.bit = 0;
return decode_choice(&bs, &ras_message, (char *) ras, 0);
}
/****************************************************************************/
static int DecodeH323_UserInformation(unsigned char *buf, unsigned char *beg,
size_t sz, H323_UserInformation *uuie)
{
static const struct field_t h323_userinformation = {
FNAME("H323-UserInformation") SEQ, 1, 2, 2, DECODE | EXT,
0, _H323_UserInformation
};
bitstr_t bs;
bs.buf = buf;
bs.beg = bs.cur = beg;
bs.end = beg + sz;
bs.bit = 0;
return decode_seq(&bs, &h323_userinformation, (char *) uuie, 0);
}
/****************************************************************************/
int DecodeMultimediaSystemControlMessage(unsigned char *buf, size_t sz,
MultimediaSystemControlMessage *
mscm)
{
static const struct field_t multimediasystemcontrolmessage = {
FNAME("MultimediaSystemControlMessage") CHOICE, 2, 4, 4,
DECODE | EXT, 0, _MultimediaSystemControlMessage
};
bitstr_t bs;
bs.buf = bs.beg = bs.cur = buf;
bs.end = buf + sz;
bs.bit = 0;
return decode_choice(&bs, &multimediasystemcontrolmessage,
(char *) mscm, 0);
}
/****************************************************************************/
int DecodeQ931(unsigned char *buf, size_t sz, Q931 *q931)
{
unsigned char *p = buf;
int len;
if (!p || sz < 1)
return H323_ERROR_BOUND;
/* Protocol Discriminator */
if (*p != 0x08) {
PRINT("Unknown Protocol Discriminator\n");
return H323_ERROR_RANGE;
}
p++;
sz--;
/* CallReferenceValue */
if (sz < 1)
return H323_ERROR_BOUND;
len = *p++;
sz--;
if (sz < len)
return H323_ERROR_BOUND;
p += len;
sz -= len;
/* Message Type */
if (sz < 1)
return H323_ERROR_BOUND;
q931->MessageType = *p++;
PRINT("MessageType = %02X\n", q931->MessageType);
if (*p & 0x80) {
p++;
sz--;
}
/* Decode Information Elements */
while (sz > 0) {
if (*p == 0x7e) { /* UserUserIE */
if (sz < 3)
break;
p++;
len = *p++ << 8;
len |= *p++;
sz -= 3;
if (sz < len)
break;
p++;
len--;
return DecodeH323_UserInformation(buf, p, len,
&q931->UUIE);
}
p++;
sz--;
if (sz < 1)
break;
len = *p++;
if (sz < len)
break;
p += len;
sz -= len;
}
PRINT("Q.931 UUIE not found\n");
return H323_ERROR_BOUND;
}