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ASN1: rewrite _decode_der

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this rewrite makes phpseclib better able to handle indef lengths,
which had previously been untested.
This commit is contained in:
terrafrost 2014-08-25 10:12:56 -05:00
parent 7696cbf826
commit e258e001fa
1 changed files with 220 additions and 211 deletions
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89
phpseclib/File/ASN1.php
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@ -272,7 +272,8 @@ class File_ASN1
}
$this->encoded = $encoded;
return $this->_decode_ber($encoded);
// encapsulate in an array for BC with the old decodeBER
return array($this->_decode_ber($encoded));
}
/**
@ -287,11 +288,8 @@ class File_ASN1
* @return Array
* @access private
*/
function _decode_ber(&$encoded, $start = 0)
function _decode_ber($encoded, $start = 0)
{
$decoded = array();
while ( strlen($encoded) ) {
$current = array('start' => $start);
$type = ord($this->_string_shift($encoded));
@ -317,16 +315,13 @@ class File_ASN1
if ( $length == 0x80 ) { // indefinite length
// "[A sender shall] use the indefinite form (see 8.1.3.6) if the encoding is constructed and is not all
// immediately available." -- paragraph 8.1.3.2.c
//if ( !$constructed ) {
// return false;
//}
$length = strlen($encoded);
} elseif ( $length & 0x80 ) { // definite length, long form
// technically, the long form of the length can be represented by up to 126 octets (bytes), but we'll only
// support it up to four.
$length&= 0x7F;
$temp = $this->_string_shift($encoded, $length);
// tags of indefinite length don't really have a header length; this length includes the tag
// tags of indefinte length don't really have a header length; this length includes the tag
$current+= array('headerlength' => $length + 2);
$start+= $length;
extract(unpack('Nlength', substr(str_pad($temp, 4, chr(0), STR_PAD_LEFT), -4)));
@ -334,12 +329,10 @@ class File_ASN1
$current+= array('headerlength' => 2);
}
// End-of-content, see paragraphs 8.1.1.3, 8.1.3.2, 8.1.3.6, 8.1.5, and (for an example) 8.6.4.2
if (!$type && !$length) {
return $decoded;
}
$content = $this->_string_shift($encoded, $length);
// at this point $length can be overwritten. it's only accurate for definite length things as is
/* Class is UNIVERSAL, APPLICATION, PRIVATE, or CONTEXT-SPECIFIC. The UNIVERSAL class is restricted to the ASN.1
built-in types. It defines an application-independent data type that must be distinguishable from all other
data types. The other three classes are user defined. The APPLICATION class distinguishes data types that
@ -354,14 +347,24 @@ class File_ASN1
case FILE_ASN1_CLASS_APPLICATION:
case FILE_ASN1_CLASS_PRIVATE:
case FILE_ASN1_CLASS_CONTEXT_SPECIFIC:
$decoded[] = array(
$newcontent = $this->_decode_ber($content, $start);
$length = $newcontent['length'];
if (substr($content, $length, 2) == "\0\0") {
$length+= 2;
}
$start+= $length;
return array(
'type' => $class,
'constant' => $tag,
'content' => $constructed ? $this->_decode_ber($content, $start) : $content,
'length' => $length + $start - $current['start']
// the array encapsulation is for BC with the old format
'content' => array($newcontent),
// the only time when $content['headerlength'] isn't defined is when the length is indefinite.
// the absence of $content['headerlength'] is how we know if something is indefinite or not.
// technically, it could be defined to be 2 and then another indicator could be used but whatever.
'length' => $start - $current['start']
) + $current;
$start+= $length;
continue 2;
}
$current+= array('type' => $tag);
@ -409,16 +412,21 @@ class File_ASN1
if (!$constructed) {
$current['content'] = $content;
} else {
$temp = $this->_decode_ber($content, $start);
$length-= strlen($content);
for ($i = 0, $size = count($temp); $i < $size; $i++) {
$current['content'] = '';
$length = 0;
while (substr($content, 0, 2) != "\0\0") {
$temp = $this->_decode_ber($content, $length + $start);
$this->_string_shift($content, $temp['length']);
// all subtags should be octet strings
//if ($temp[$i]['type'] != FILE_ASN1_TYPE_OCTET_STRING) {
//if ($temp['type'] != FILE_ASN1_TYPE_OCTET_STRING) {
// return false;
//}
$current['content'].= $temp[$i]['content'];
$current['content'].= $temp['content'];
$length+= $temp['length'];
}
if (substr($content, 0, 2) == "\0\0") {
$length+= 2; // +2 for the EOC
}
// $length =
}
break;
case FILE_ASN1_TYPE_NULL:
@ -429,7 +437,20 @@ class File_ASN1
break;
case FILE_ASN1_TYPE_SEQUENCE:
case FILE_ASN1_TYPE_SET:
$current['content'] = $this->_decode_ber($content, $start);
$offset = 0;
$current['content'] = array();
while (strlen($content)) {
// if indefinite length construction was used and we have an end-of-content string next
// see paragraphs 8.1.1.3, 8.1.3.2, 8.1.3.6, 8.1.5, and (for an example) 8.6.4.2
if (!isset($current['headerlength']) && substr($content, 0, 2) == "\0\0") {
$length = $offset + 2; // +2 for the EOC
break 2;
}
$temp = $this->_decode_ber($content, $start + $offset);
$this->_string_shift($content, $temp['length']);
$current['content'][] = $temp;
$offset+= $temp['length'];
}
break;
case FILE_ASN1_TYPE_OBJECT_IDENTIFIER:
$temp = ord($this->_string_shift($content));
@ -484,18 +505,16 @@ class File_ASN1
case FILE_ASN1_TYPE_GENERALIZED_TIME:
$current['content'] = $this->_decodeTime($content, $tag);
default:
}
$start+= $length;
$decoded[] = $current + array('length' => $start - $current['start']);
}
return $decoded;
// ie. length is the length of the full TLV encoding - it's not just the length of the value
return $current + array('length' => $start - $current['start']);
}
/**
* ASN.1 Decode
* ASN.1 Map
*
* Provides an ASN.1 semantic mapping ($mapping) from a parsed BER-encoding to a human readable format.
*
@ -805,16 +824,6 @@ class File_ASN1
return $this->_encode_der($source, $mapping, null, $special);
}
/**
* ASN.1 Encode (Helper function)
*
* @param String $source
* @param Array $mapping
* @param Integer $idx
* @param Array $special
* @return String
* @access private
*/
/**
* ASN.1 Encode (Helper function)
*