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transmission/libtransmission/bencode.c

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/******************************************************************************
* $Id$
*
* Copyright (c) 2005-2008 Transmission authors and contributors
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*****************************************************************************/
#include <assert.h>
#include <ctype.h> /* isdigit, isprint */
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <event.h> /* evbuffer */
#include "transmission.h"
#include "bencode.h"
#include "ptrarray.h"
#include "utils.h" /* tr_new(), tr_free() */
/**
***
**/
static int
isInt( const benc_val_t * val )
{
return val!=NULL && val->type==TYPE_INT;
}
static int
isList( const benc_val_t * val )
{
return val!=NULL && val->type==TYPE_LIST;
}
static int
isDict( const benc_val_t * val )
{
return val!=NULL && val->type==TYPE_DICT;
}
static int
isContainer( const benc_val_t * val )
{
return val!=NULL && ( val->type & ( TYPE_DICT | TYPE_LIST ) );
}
benc_val_t*
tr_bencListGetNthChild( benc_val_t * val, int i )
{
benc_val_t * ret = NULL;
if( isList( val ) && ( i >= 0 ) && ( i < val->val.l.count ) )
ret = val->val.l.vals + i;
return ret;
}
/**
***
**/
/**
* The initial i and trailing e are beginning and ending delimiters.
* You can have negative numbers such as i-3e. You cannot prefix the
* number with a zero such as i04e. However, i0e is valid.
* Example: i3e represents the integer "3"
* NOTE: The maximum number of bit of this integer is unspecified,
* but to handle it as a signed 64bit integer is mandatory to handle
* "large files" aka .torrent for more that 4Gbyte
*/
int
tr_bencParseInt( const uint8_t * buf,
const uint8_t * bufend,
const uint8_t ** setme_end,
int64_t * setme_val )
{
int err = TR_OK;
char * endptr;
const void * begin;
const void * end;
int64_t val;
if( buf >= bufend )
return TR_ERROR;
if( *buf != 'i' )
return TR_ERROR;
begin = buf + 1;
end = memchr( begin, 'e', (bufend-buf)-1 );
if( end == NULL )
return TR_ERROR;
errno = 0;
val = strtoll( begin, &endptr, 10 );
if( errno || ( endptr != end ) ) /* incomplete parse */
err = TR_ERROR;
else if( val && *(const char*)begin=='0' ) /* no leading zeroes! */
err = TR_ERROR;
else {
*setme_end = end + 1;
*setme_val = val;
}
return err;
}
/**
* Byte strings are encoded as follows:
* <string length encoded in base ten ASCII>:<string data>
* Note that there is no constant beginning delimiter, and no ending delimiter.
* Example: 4:spam represents the string "spam"
*/
int
tr_bencParseStr( const uint8_t * buf,
const uint8_t * bufend,
const uint8_t ** setme_end,
uint8_t ** setme_str,
size_t * setme_strlen )
{
size_t len;
const void * end;
char * endptr;
if( buf >= bufend )
return TR_ERROR;
if( !isdigit( *buf ) )
return TR_ERROR;
end = memchr( buf, ':', bufend-buf );
if( end == NULL )
return TR_ERROR;
errno = 0;
len = strtoul( (const char*)buf, &endptr, 10 );
if( errno || endptr!=end )
return TR_ERROR;
if( (const uint8_t*)end + 1 + len > bufend )
return TR_ERROR;
*setme_end = end + 1 + len;
*setme_str = (uint8_t*) tr_strndup( end + 1, len );
*setme_strlen = len;
return TR_OK;
}
/* setting to 1 to help expose bugs with tr_bencListAdd and tr_bencDictAdd */
#define LIST_SIZE 8 /* number of items to increment list/dict buffer by */
static int
makeroom( benc_val_t * val, int count )
{
assert( TYPE_LIST == val->type || TYPE_DICT == val->type );
if( val->val.l.count + count > val->val.l.alloc )
{
/* We need a bigger boat */
const int len = val->val.l.alloc + count +
( count % LIST_SIZE ? LIST_SIZE - ( count % LIST_SIZE ) : 0 );
void * new = realloc( val->val.l.vals, len * sizeof( benc_val_t ) );
if( NULL == new )
return 1;
val->val.l.alloc = len;
val->val.l.vals = new;
}
return 0;
}
static benc_val_t*
getNode( benc_val_t * top, tr_ptrArray * parentStack, int type )
{
benc_val_t * parent;
assert( top != NULL );
assert( parentStack != NULL );
if( tr_ptrArrayEmpty( parentStack ) )
return top;
parent = tr_ptrArrayBack( parentStack );
assert( parent != NULL );
/* dictionary keys must be strings */
if( ( parent->type == TYPE_DICT )
&& ( type != TYPE_STR )
&& ( ! ( parent->val.l.count % 2 ) ) )
return NULL;
makeroom( parent, 1 );
return parent->val.l.vals + parent->val.l.count++;
}
/**
* This function's previous recursive implementation was
* easier to read, but was vulnerable to a smash-stacking
* attack via maliciously-crafted bencoded data. (#667)
*/
int
tr_bencParse( const void * buf_in,
const void * bufend_in,
benc_val_t * top,
const uint8_t ** setme_end )
{
int err;
const uint8_t * buf = buf_in;
const uint8_t * bufend = bufend_in;
tr_ptrArray * parentStack = tr_ptrArrayNew( );
while( buf != bufend )
{
if( buf > bufend ) /* no more text to parse... */
return 1;
if( *buf=='i' ) /* int */
{
int64_t val;
const uint8_t * end;
int err;
benc_val_t * node;
if(( err = tr_bencParseInt( buf, bufend, &end, &val )))
return err;
node = getNode( top, parentStack, TYPE_INT );
if( !node )
return TR_ERROR;
tr_bencInitInt( node, val );
buf = end;
if( tr_ptrArrayEmpty( parentStack ) )
break;
}
else if( *buf=='l' ) /* list */
{
benc_val_t * node = getNode( top, parentStack, TYPE_LIST );
if( !node )
return TR_ERROR;
tr_bencInit( node, TYPE_LIST );
tr_ptrArrayAppend( parentStack, node );
++buf;
}
else if( *buf=='d' ) /* dict */
{
benc_val_t * node = getNode( top, parentStack, TYPE_DICT );
if( !node )
return TR_ERROR;
tr_bencInit( node, TYPE_DICT );
tr_ptrArrayAppend( parentStack, node );
++buf;
}
else if( *buf=='e' ) /* end of list or dict */
{
++buf;
if( tr_ptrArrayEmpty( parentStack ) )
return TR_ERROR;
tr_ptrArrayPop( parentStack );
if( tr_ptrArrayEmpty( parentStack ) )
break;
}
else if( isdigit(*buf) ) /* string? */
{
const uint8_t * end;
uint8_t * str;
size_t str_len;
int err;
benc_val_t * node;
if(( err = tr_bencParseStr( buf, bufend, &end, &str, &str_len )))
return err;
node = getNode( top, parentStack, TYPE_STR );
if( !node )
return TR_ERROR;
tr_bencInitStr( node, str, str_len, 0 );
buf = end;
if( tr_ptrArrayEmpty( parentStack ) )
break;
}
else /* invalid bencoded text... march past it */
{
++buf;
}
}
err = tr_ptrArrayEmpty( parentStack ) ? 0 : 1;
if( !err && ( setme_end != NULL ) )
*setme_end = buf;
tr_ptrArrayFree( parentStack, NULL );
return err;
}
int
tr_bencLoad( const void * buf_in,
int buflen,
benc_val_t * setme_benc,
char ** setme_end )
{
const uint8_t * buf = buf_in;
const uint8_t * end;
const int ret = tr_bencParse( buf, buf+buflen, setme_benc, &end );
if( !ret && setme_end )
*setme_end = (char*) end;
return ret;
}
benc_val_t *
tr_bencDictFind( benc_val_t * val, const char * key )
{
int len, ii;
if( val->type != TYPE_DICT )
{
return NULL;
}
len = strlen( key );
for( ii = 0; ii + 1 < val->val.l.count; ii += 2 )
{
if( TYPE_STR != val->val.l.vals[ii].type ||
len != val->val.l.vals[ii].val.s.i ||
0 != memcmp( val->val.l.vals[ii].val.s.s, key, len ) )
{
continue;
}
return &val->val.l.vals[ii+1];
}
return NULL;
}
benc_val_t*
tr_bencDictFindType( benc_val_t * val, const char * key, int type )
{
benc_val_t * ret = tr_bencDictFind( val, key );
return ret && ret->type == type ? ret : NULL;
}
int64_t
tr_bencGetInt ( const benc_val_t * val )
{
assert( isInt( val ) );
return val->val.i;
}
benc_val_t *
tr_bencDictFindFirst( benc_val_t * val, ... )
{
const char * key;
benc_val_t * ret;
va_list ap;
ret = NULL;
va_start( ap, val );
while( ( key = va_arg( ap, const char * ) ) )
{
ret = tr_bencDictFind( val, key );
if( NULL != ret )
{
break;
}
}
va_end( ap );
return ret;
}
char *
tr_bencStealStr( benc_val_t * val )
{
assert( TYPE_STR == val->type );
val->val.s.nofree = 1;
return val->val.s.s;
}
void
_tr_bencInitStr( benc_val_t * val, char * str, int len, int nofree )
{
tr_bencInit( val, TYPE_STR );
val->val.s.s = str;
val->val.s.nofree = nofree;
if( 0 >= len )
{
len = ( NULL == str ? 0 : strlen( str ) );
}
val->val.s.i = len;
}
int
tr_bencInitStrDup( benc_val_t * val, const char * str )
{
char * newStr = tr_strdup( str );
if( newStr == NULL )
return 1;
_tr_bencInitStr( val, newStr, 0, 0 );
return 0;
}
void
tr_bencInitInt( benc_val_t * val, int64_t num )
{
tr_bencInit( val, TYPE_INT );
val->val.i = num;
}
int
tr_bencListReserve( benc_val_t * val, int count )
{
assert( TYPE_LIST == val->type );
return makeroom( val, count );
}
int
tr_bencDictReserve( benc_val_t * val, int count )
{
assert( TYPE_DICT == val->type );
return makeroom( val, count * 2 );
}
benc_val_t *
tr_bencListAdd( benc_val_t * list )
{
benc_val_t * item;
assert( isList( list ) );
assert( list->val.l.count < list->val.l.alloc );
item = &list->val.l.vals[list->val.l.count];
list->val.l.count++;
tr_bencInit( item, TYPE_INT );
return item;
}
benc_val_t *
tr_bencDictAdd( benc_val_t * dict, const char * key )
{
benc_val_t * keyval, * itemval;
assert( isDict( dict ) );
assert( dict->val.l.count + 2 <= dict->val.l.alloc );
keyval = dict->val.l.vals + dict->val.l.count++;
tr_bencInitStr( keyval, (char*)key, -1, 1 );
itemval = dict->val.l.vals + dict->val.l.count++;
tr_bencInit( itemval, TYPE_INT );
return itemval;
}
/***
**** BENC WALKING
***/
struct KeyIndex
{
const char * key;
int index;
};
static int
compareKeyIndex( const void * va, const void * vb )
{
const struct KeyIndex * a = va;
const struct KeyIndex * b = vb;
return strcmp( a->key, b->key );
}
struct SaveNode
{
const benc_val_t * val;
int valIsVisited;
int childCount;
int childIndex;
int * children;
};
static struct SaveNode*
nodeNewDict( const benc_val_t * val )
{
int i, j, n;
struct SaveNode * node;
struct KeyIndex * indices;
assert( isDict( val ) );
n = val->val.l.count;
node = tr_new0( struct SaveNode, 1 );
node->val = val;
node->children = tr_new0( int, n );
/* ugh, a dictionary's children have to be sorted by key... */
indices = tr_new( struct KeyIndex, n );
for( i=j=0; i<n; i+=2, ++j ) {
indices[j].key = val->val.l.vals[i].val.s.s;
indices[j].index = i;
}
qsort( indices, j, sizeof(struct KeyIndex), compareKeyIndex );
for( i=0; i<j; ++i ) {
const int index = indices[i].index;
node->children[ node->childCount++ ] = index;
node->children[ node->childCount++ ] = index + 1;
}
assert( node->childCount == n );
tr_free( indices );
return node;
}
static struct SaveNode*
nodeNewList( const benc_val_t * val )
{
int i, n;
struct SaveNode * node;
assert( isList( val ) );
n = val->val.l.count;
node = tr_new0( struct SaveNode, 1 );
node->val = val;
node->childCount = n;
node->children = tr_new0( int, n );
for( i=0; i<n; ++i ) /* a list's children don't need to be reordered */
node->children[i] = i;
return node;
}
static struct SaveNode*
nodeNewLeaf( const benc_val_t * val )
{
struct SaveNode * node;
assert( !isContainer( val ) );
node = tr_new0( struct SaveNode, 1 );
node->val = val;
return node;
}
static struct SaveNode*
nodeNew( const benc_val_t * val )
{
struct SaveNode * node;
if( val->type == TYPE_LIST )
node = nodeNewList( val );
else if( val->type == TYPE_DICT )
node = nodeNewDict( val );
else
node = nodeNewLeaf( val );
return node;
}
typedef void (*BencWalkFunc)( const benc_val_t * val, void * user_data );
struct WalkFuncs
{
BencWalkFunc intFunc;
BencWalkFunc stringFunc;
BencWalkFunc dictBeginFunc;
BencWalkFunc listBeginFunc;
BencWalkFunc containerEndFunc;
};
/**
* This function's previous recursive implementation was
* easier to read, but was vulnerable to a smash-stacking
* attack via maliciously-crafted bencoded data. (#667)
*/
static void
bencWalk( const benc_val_t * top,
struct WalkFuncs * walkFuncs,
void * user_data )
{
tr_ptrArray * stack = tr_ptrArrayNew( );
tr_ptrArrayAppend( stack, nodeNew( top ) );
while( !tr_ptrArrayEmpty( stack ) )
{
struct SaveNode * node = tr_ptrArrayBack( stack );
const benc_val_t * val;
if( !node->valIsVisited )
{
val = node->val;
node->valIsVisited = TRUE;
}
else if( node->childIndex < node->childCount )
{
const int index = node->children[ node->childIndex++ ];
val = node->val->val.l.vals + index;
}
else /* done with this node */
{
if( isContainer( node->val ) )
walkFuncs->containerEndFunc( node->val, user_data );
tr_ptrArrayPop( stack );
tr_free( node->children );
tr_free( node );
continue;
}
switch( val->type )
{
case TYPE_INT:
walkFuncs->intFunc( val, user_data );
break;
case TYPE_STR:
walkFuncs->stringFunc( val, user_data );
break;
case TYPE_LIST:
if( val != node->val )
tr_ptrArrayAppend( stack, nodeNew( val ) );
else
walkFuncs->listBeginFunc( val, user_data );
break;
case TYPE_DICT:
if( val != node->val )
tr_ptrArrayAppend( stack, nodeNew( val ) );
else
walkFuncs->dictBeginFunc( val, user_data );
break;
default:
/* did caller give us an uninitialized val? */
tr_err( "Invalid benc type %d", val->type );
break;
}
}
tr_ptrArrayFree( stack, NULL );
}
/****
*****
****/
static void
saveIntFunc( const benc_val_t * val, void * evbuf )
{
evbuffer_add_printf( evbuf, "i%"PRId64"e", tr_bencGetInt(val) );
}
static void
saveStringFunc( const benc_val_t * val, void * vevbuf )
{
struct evbuffer * evbuf = vevbuf;
evbuffer_add_printf( evbuf, "%i:", val->val.s.i );
evbuffer_add( evbuf, val->val.s.s, val->val.s.i );
}
static void
saveDictBeginFunc( const benc_val_t * val UNUSED, void * evbuf )
{
evbuffer_add_printf( evbuf, "d" );
}
static void
saveListBeginFunc( const benc_val_t * val UNUSED, void * evbuf )
{
evbuffer_add_printf( evbuf, "l" );
}
static void
saveContainerEndFunc( const benc_val_t * val UNUSED, void * evbuf )
{
evbuffer_add_printf( evbuf, "e" );
}
char*
tr_bencSave( const benc_val_t * top, int * len )
{
char * ret;
struct WalkFuncs walkFuncs;
struct evbuffer * out = evbuffer_new( );
walkFuncs.intFunc = saveIntFunc;
walkFuncs.stringFunc = saveStringFunc;
walkFuncs.dictBeginFunc = saveDictBeginFunc;
walkFuncs.listBeginFunc = saveListBeginFunc;
walkFuncs.containerEndFunc = saveContainerEndFunc;
bencWalk( top, &walkFuncs, out );
if( len != NULL )
*len = EVBUFFER_LENGTH( out );
ret = tr_strndup( (char*) EVBUFFER_DATA( out ), EVBUFFER_LENGTH( out ) );
evbuffer_free( out );
return ret;
}
/***
****
***/
static void
freeDummyFunc( const benc_val_t * val UNUSED, void * buf UNUSED )
{
}
static void
freeStringFunc( const benc_val_t * val, void * freeme )
{
if( !val->val.s.nofree )
tr_ptrArrayAppend( freeme, val->val.s.s );
}
static void
freeContainerBeginFunc( const benc_val_t * val, void * freeme )
{
tr_ptrArrayAppend( freeme, val->val.l.vals );
}
void
tr_bencFree( benc_val_t * val )
{
if( val != NULL )
{
tr_ptrArray * freeme = tr_ptrArrayNew( );
struct WalkFuncs walkFuncs;
walkFuncs.intFunc = freeDummyFunc;
walkFuncs.stringFunc = freeStringFunc;
walkFuncs.dictBeginFunc = freeContainerBeginFunc;
walkFuncs.listBeginFunc = freeContainerBeginFunc;
walkFuncs.containerEndFunc = freeDummyFunc;
bencWalk( val, &walkFuncs, freeme );
tr_ptrArrayFree( freeme, tr_free );
}
}
/***
****
***/
struct WalkPrint
{
int depth;
FILE * out;
};
static void
printLeadingSpaces( struct WalkPrint * data )
{
const int width = data->depth * 2;
fprintf( data->out, "%*.*s", width, width, " " );
}
static void
printIntFunc( const benc_val_t * val, void * vdata )
{
struct WalkPrint * data = vdata;
printLeadingSpaces( data );
fprintf( data->out, "int: %"PRId64"\n", tr_bencGetInt(val) );
}
static void
printStringFunc( const benc_val_t * val, void * vdata )
{
int ii;
struct WalkPrint * data = vdata;
printLeadingSpaces( data );
fprintf( data->out, "string: " );
for( ii = 0; val->val.s.i > ii; ii++ )
{
if( '\\' == val->val.s.s[ii] ) {
putc( '\\', data->out );
putc( '\\', data->out );
} else if( isprint( val->val.s.s[ii] ) ) {
putc( val->val.s.s[ii], data->out );
} else {
fprintf( data->out, "\\x%02x", val->val.s.s[ii] );
}
}
fprintf( data->out, "\n" );
}
static void
printListBeginFunc( const benc_val_t * val UNUSED, void * vdata )
{
struct WalkPrint * data = vdata;
printLeadingSpaces( data );
fprintf( data->out, "list\n" );
++data->depth;
}
static void
printDictBeginFunc( const benc_val_t * val UNUSED, void * vdata )
{
struct WalkPrint * data = vdata;
printLeadingSpaces( data );
fprintf( data->out, "dict\n" );
++data->depth;
}
static void
printContainerEndFunc( const benc_val_t * val UNUSED, void * vdata )
{
struct WalkPrint * data = vdata;
--data->depth;
}
void
tr_bencPrint( benc_val_t * val )
{
struct WalkFuncs walkFuncs;
struct WalkPrint walkPrint;
walkFuncs.intFunc = printIntFunc;
walkFuncs.stringFunc = printStringFunc;
walkFuncs.dictBeginFunc = printDictBeginFunc;
walkFuncs.listBeginFunc = printListBeginFunc;
walkFuncs.containerEndFunc = printContainerEndFunc;
walkPrint.out = stderr;
walkPrint.depth = 0;
bencWalk( val, &walkFuncs, &walkPrint );
}
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