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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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431
phpseclib/File/ASN1.php
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@ -272,7 +272,8 @@ class File_ASN1
} }
$this->encoded = $encoded; $this->encoded = $encoded;
return $this->_decode_ber($encoded); // encapsulate in an array for BC with the old decodeBER
return array($this->_decode_ber($encoded));
} }
/** /**
@ -287,215 +288,233 @@ class File_ASN1
* @return Array * @return Array
* @access private * @access private
*/ */
function _decode_ber(&$encoded, $start = 0) function _decode_ber($encoded, $start = 0)
{ {
$decoded = array(); $current = array('start' => $start);
while ( strlen($encoded) ) { $type = ord($this->_string_shift($encoded));
$current = array('start' => $start); $start++;
$type = ord($this->_string_shift($encoded)); $constructed = ($type >> 5) & 1;
$start++;
$constructed = ($type >> 5) & 1; $tag = $type & 0x1F;
if ($tag == 0x1F) {
$tag = $type & 0x1F; $tag = 0;
if ($tag == 0x1F) { // process septets (since the eighth bit is ignored, it's not an octet)
$tag = 0; do {
// process septets (since the eighth bit is ignored, it's not an octet) $loop = ord($encoded[0]) >> 7;
do { $tag <<= 7;
$loop = ord($encoded[0]) >> 7; $tag |= ord($this->_string_shift($encoded)) & 0x7F;
$tag <<= 7; $start++;
$tag |= ord($this->_string_shift($encoded)) & 0x7F; } while ( $loop );
$start++;
} while ( $loop );
}
// Length, as discussed in paragraph 8.1.3 of X.690-0207.pdf#page=13
$length = ord($this->_string_shift($encoded));
$start++;
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
$current+= array('headerlength' => $length + 2);
$start+= $length;
extract(unpack('Nlength', substr(str_pad($temp, 4, chr(0), STR_PAD_LEFT), -4)));
} else {
$current+= array('headerlength' => 2);
}
// End-of-content, see paragraphs 8.1.1.3, 8.1.3.2, 8.1.3.6, 8.1.5, and (for an example) 8.6.4.2
if (!$type && !$length) {
return $decoded;
}
$content = $this->_string_shift($encoded, $length);
/* 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
have a wide, scattered use within a particular presentation context. PRIVATE distinguishes data types within
a particular organization or country. CONTEXT-SPECIFIC distinguishes members of a sequence or set, the
alternatives of a CHOICE, or universally tagged set members. Only the class number appears in braces for this
data type; the term CONTEXT-SPECIFIC does not appear.
-- http://www.obj-sys.com/asn1tutorial/node12.html */
$class = ($type >> 6) & 3;
switch ($class) {
case FILE_ASN1_CLASS_APPLICATION:
case FILE_ASN1_CLASS_PRIVATE:
case FILE_ASN1_CLASS_CONTEXT_SPECIFIC:
$decoded[] = array(
'type' => $class,
'constant' => $tag,
'content' => $constructed ? $this->_decode_ber($content, $start) : $content,
'length' => $length + $start - $current['start']
) + $current;
$start+= $length;
continue 2;
}
$current+= array('type' => $tag);
// decode UNIVERSAL tags
switch ($tag) {
case FILE_ASN1_TYPE_BOOLEAN:
// "The contents octets shall consist of a single octet." -- paragraph 8.2.1
//if (strlen($content) != 1) {
// return false;
//}
$current['content'] = (bool) ord($content[0]);
break;
case FILE_ASN1_TYPE_INTEGER:
case FILE_ASN1_TYPE_ENUMERATED:
$current['content'] = new Math_BigInteger($content, -256);
break;
case FILE_ASN1_TYPE_REAL: // not currently supported
return false;
case FILE_ASN1_TYPE_BIT_STRING:
// The initial octet shall encode, as an unsigned binary integer with bit 1 as the least significant bit,
// the number of unused bits in the final subsequent octet. The number shall be in the range zero to
// seven.
if (!$constructed) {
$current['content'] = $content;
} else {
$temp = $this->_decode_ber($content, $start);
$length-= strlen($content);
$last = count($temp) - 1;
for ($i = 0; $i < $last; $i++) {
// all subtags should be bit strings
//if ($temp[$i]['type'] != FILE_ASN1_TYPE_BIT_STRING) {
// return false;
//}
$current['content'].= substr($temp[$i]['content'], 1);
}
// all subtags should be bit strings
//if ($temp[$last]['type'] != FILE_ASN1_TYPE_BIT_STRING) {
// return false;
//}
$current['content'] = $temp[$last]['content'][0] . $current['content'] . substr($temp[$i]['content'], 1);
}
break;
case FILE_ASN1_TYPE_OCTET_STRING:
if (!$constructed) {
$current['content'] = $content;
} else {
$temp = $this->_decode_ber($content, $start);
$length-= strlen($content);
for ($i = 0, $size = count($temp); $i < $size; $i++) {
// all subtags should be octet strings
//if ($temp[$i]['type'] != FILE_ASN1_TYPE_OCTET_STRING) {
// return false;
//}
$current['content'].= $temp[$i]['content'];
}
// $length =
}
break;
case FILE_ASN1_TYPE_NULL:
// "The contents octets shall not contain any octets." -- paragraph 8.8.2
//if (strlen($content)) {
// return false;
//}
break;
case FILE_ASN1_TYPE_SEQUENCE:
case FILE_ASN1_TYPE_SET:
$current['content'] = $this->_decode_ber($content, $start);
break;
case FILE_ASN1_TYPE_OBJECT_IDENTIFIER:
$temp = ord($this->_string_shift($content));
$current['content'] = sprintf('%d.%d', floor($temp / 40), $temp % 40);
$valuen = 0;
// process septets
while (strlen($content)) {
$temp = ord($this->_string_shift($content));
$valuen <<= 7;
$valuen |= $temp & 0x7F;
if (~$temp & 0x80) {
$current['content'].= ".$valuen";
$valuen = 0;
}
}
// the eighth bit of the last byte should not be 1
//if ($temp >> 7) {
// return false;
//}
break;
/* Each character string type shall be encoded as if it had been declared:
[UNIVERSAL x] IMPLICIT OCTET STRING
-- X.690-0207.pdf#page=23 (paragraph 8.21.3)
Per that, we're not going to do any validation. If there are any illegal characters in the string,
we don't really care */
case FILE_ASN1_TYPE_NUMERIC_STRING:
// 0,1,2,3,4,5,6,7,8,9, and space
case FILE_ASN1_TYPE_PRINTABLE_STRING:
// Upper and lower case letters, digits, space, apostrophe, left/right parenthesis, plus sign, comma,
// hyphen, full stop, solidus, colon, equal sign, question mark
case FILE_ASN1_TYPE_TELETEX_STRING:
// The Teletex character set in CCITT's T61, space, and delete
// see http://en.wikipedia.org/wiki/Teletex#Character_sets
case FILE_ASN1_TYPE_VIDEOTEX_STRING:
// The Videotex character set in CCITT's T.100 and T.101, space, and delete
case FILE_ASN1_TYPE_VISIBLE_STRING:
// Printing character sets of international ASCII, and space
case FILE_ASN1_TYPE_IA5_STRING:
// International Alphabet 5 (International ASCII)
case FILE_ASN1_TYPE_GRAPHIC_STRING:
// All registered G sets, and space
case FILE_ASN1_TYPE_GENERAL_STRING:
// All registered C and G sets, space and delete
case FILE_ASN1_TYPE_UTF8_STRING:
// ????
case FILE_ASN1_TYPE_BMP_STRING:
$current['content'] = $content;
break;
case FILE_ASN1_TYPE_UTC_TIME:
case FILE_ASN1_TYPE_GENERALIZED_TIME:
$current['content'] = $this->_decodeTime($content, $tag);
default:
}
$start+= $length;
$decoded[] = $current + array('length' => $start - $current['start']);
} }
return $decoded; // Length, as discussed in paragraph 8.1.3 of X.690-0207.pdf#page=13
$length = ord($this->_string_shift($encoded));
$start++;
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
$length = strlen($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 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)));
} else {
$current+= array('headerlength' => 2);
}
$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
have a wide, scattered use within a particular presentation context. PRIVATE distinguishes data types within
a particular organization or country. CONTEXT-SPECIFIC distinguishes members of a sequence or set, the
alternatives of a CHOICE, or universally tagged set members. Only the class number appears in braces for this
data type; the term CONTEXT-SPECIFIC does not appear.
-- http://www.obj-sys.com/asn1tutorial/node12.html */
$class = ($type >> 6) & 3;
switch ($class) {
case FILE_ASN1_CLASS_APPLICATION:
case FILE_ASN1_CLASS_PRIVATE:
case FILE_ASN1_CLASS_CONTEXT_SPECIFIC:
$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' => $tag,
// the array encapsulation is for BC with the old format
'content' => array($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;
}
$current+= array('type' => $tag);
// decode UNIVERSAL tags
switch ($tag) {
case FILE_ASN1_TYPE_BOOLEAN:
// "The contents octets shall consist of a single octet." -- paragraph 8.2.1
//if (strlen($content) != 1) {
// return false;
//}
$current['content'] = (bool) ord($content[0]);
break;
case FILE_ASN1_TYPE_INTEGER:
case FILE_ASN1_TYPE_ENUMERATED:
$current['content'] = new Math_BigInteger($content, -256);
break;
case FILE_ASN1_TYPE_REAL: // not currently supported
return false;
case FILE_ASN1_TYPE_BIT_STRING:
// The initial octet shall encode, as an unsigned binary integer with bit 1 as the least significant bit,
// the number of unused bits in the final subsequent octet. The number shall be in the range zero to
// seven.
if (!$constructed) {
$current['content'] = $content;
} else {
$temp = $this->_decode_ber($content, $start);
$length-= strlen($content);
$last = count($temp) - 1;
for ($i = 0; $i < $last; $i++) {
// all subtags should be bit strings
//if ($temp[$i]['type'] != FILE_ASN1_TYPE_BIT_STRING) {
// return false;
//}
$current['content'].= substr($temp[$i]['content'], 1);
}
// all subtags should be bit strings
//if ($temp[$last]['type'] != FILE_ASN1_TYPE_BIT_STRING) {
// return false;
//}
$current['content'] = $temp[$last]['content'][0] . $current['content'] . substr($temp[$i]['content'], 1);
}
break;
case FILE_ASN1_TYPE_OCTET_STRING:
if (!$constructed) {
$current['content'] = $content;
} else {
$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['type'] != FILE_ASN1_TYPE_OCTET_STRING) {
// return false;
//}
$current['content'].= $temp['content'];
$length+= $temp['length'];
}
if (substr($content, 0, 2) == "\0\0") {
$length+= 2; // +2 for the EOC
}
}
break;
case FILE_ASN1_TYPE_NULL:
// "The contents octets shall not contain any octets." -- paragraph 8.8.2
//if (strlen($content)) {
// return false;
//}
break;
case FILE_ASN1_TYPE_SEQUENCE:
case FILE_ASN1_TYPE_SET:
$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));
$current['content'] = sprintf('%d.%d', floor($temp / 40), $temp % 40);
$valuen = 0;
// process septets
while (strlen($content)) {
$temp = ord($this->_string_shift($content));
$valuen <<= 7;
$valuen |= $temp & 0x7F;
if (~$temp & 0x80) {
$current['content'].= ".$valuen";
$valuen = 0;
}
}
// the eighth bit of the last byte should not be 1
//if ($temp >> 7) {
// return false;
//}
break;
/* Each character string type shall be encoded as if it had been declared:
[UNIVERSAL x] IMPLICIT OCTET STRING
-- X.690-0207.pdf#page=23 (paragraph 8.21.3)
Per that, we're not going to do any validation. If there are any illegal characters in the string,
we don't really care */
case FILE_ASN1_TYPE_NUMERIC_STRING:
// 0,1,2,3,4,5,6,7,8,9, and space
case FILE_ASN1_TYPE_PRINTABLE_STRING:
// Upper and lower case letters, digits, space, apostrophe, left/right parenthesis, plus sign, comma,
// hyphen, full stop, solidus, colon, equal sign, question mark
case FILE_ASN1_TYPE_TELETEX_STRING:
// The Teletex character set in CCITT's T61, space, and delete
// see http://en.wikipedia.org/wiki/Teletex#Character_sets
case FILE_ASN1_TYPE_VIDEOTEX_STRING:
// The Videotex character set in CCITT's T.100 and T.101, space, and delete
case FILE_ASN1_TYPE_VISIBLE_STRING:
// Printing character sets of international ASCII, and space
case FILE_ASN1_TYPE_IA5_STRING:
// International Alphabet 5 (International ASCII)
case FILE_ASN1_TYPE_GRAPHIC_STRING:
// All registered G sets, and space
case FILE_ASN1_TYPE_GENERAL_STRING:
// All registered C and G sets, space and delete
case FILE_ASN1_TYPE_UTF8_STRING:
// ????
case FILE_ASN1_TYPE_BMP_STRING:
$current['content'] = $content;
break;
case FILE_ASN1_TYPE_UTC_TIME:
case FILE_ASN1_TYPE_GENERALIZED_TIME:
$current['content'] = $this->_decodeTime($content, $tag);
default:
}
$start+= $length;
// 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. * 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); 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) * ASN.1 Encode (Helper function)
* *