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Improve performance of File\ASN1->_decode_ber() for large data

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This removes the use of _string_shift() which copies the (potentially large)
latter part of the input data repeatedly, in favor of maintaining a position var
and using string indexing or substr() to only copy the (relatively small)
current data as it is parsed.
This commit is contained in:
John Sterling 2016-06-19 00:34:49 -04:00 committed by terrafrost
parent c788ec574f
commit a1e16797ca
1 changed files with 34 additions and 29 deletions
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63
phpseclib/File/ASN1.php
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@ -285,14 +285,15 @@ class File_ASN1
* *
* @param string $encoded * @param string $encoded
* @param int $start * @param int $start
* @param int $encoded_pos
* @return array * @return array
* @access private * @access private
*/ */
function _decode_ber($encoded, $start = 0) function _decode_ber($encoded, $start = 0, $encoded_pos = 0)
{ {
$current = array('start' => $start); $current = array('start' => $start);
$type = ord($this->_string_shift($encoded)); $type = ord($encoded[$encoded_pos++]);
$start++; $start++;
$constructed = ($type >> 5) & 1; $constructed = ($type >> 5) & 1;
@ -304,23 +305,24 @@ class File_ASN1
do { do {
$loop = ord($encoded[0]) >> 7; $loop = ord($encoded[0]) >> 7;
$tag <<= 7; $tag <<= 7;
$tag |= ord($this->_string_shift($encoded)) & 0x7F; $tag |= ord($encoded[$encoded_pos++]) & 0x7F;
$start++; $start++;
} while ($loop); } while ($loop);
} }
// Length, as discussed in paragraph 8.1.3 of X.690-0207.pdf#page=13 // Length, as discussed in paragraph 8.1.3 of X.690-0207.pdf#page=13
$length = ord($this->_string_shift($encoded)); $length = ord($encoded[$encoded_pos++]);
$start++; $start++;
if ($length == 0x80) { // indefinite length 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 // "[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 // immediately available." -- paragraph 8.1.3.2.c
$length = strlen($encoded); $length = strlen($encoded) - $encoded_pos;
} elseif ($length & 0x80) { // definite length, long form } 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 // 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. // support it up to four.
$length&= 0x7F; $length&= 0x7F;
$temp = $this->_string_shift($encoded, $length); $temp = substr($encoded, $encoded_pos, $length);
$encoded_pos += $length;
// tags of indefinte 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); $current+= array('headerlength' => $length + 2);
$start+= $length; $start+= $length;
@ -329,11 +331,12 @@ class File_ASN1
$current+= array('headerlength' => 2); $current+= array('headerlength' => 2);
} }
if ($length > strlen($encoded)) { if ($length > (strlen($encoded) - $encoded_pos)) {
return false; return false;
} }
$content = $this->_string_shift($encoded, $length); $content = substr($encoded, $encoded_pos, $length);
$content_pos = 0;
// at this point $length can be overwritten. it's only accurate for definite length things as is // at this point $length can be overwritten. it's only accurate for definite length things as is
@ -366,7 +369,7 @@ class File_ASN1
$temp = $this->_decode_ber($content, $start); $temp = $this->_decode_ber($content, $start);
$length = $temp['length']; $length = $temp['length'];
// end-of-content octets - see paragraph 8.1.5 // end-of-content octets - see paragraph 8.1.5
if (substr($content, $length, 2) == "\0\0") { if (substr($content, $content_pos + $length, 2) == "\0\0") {
$length+= 2; $length+= 2;
$start+= $length; $start+= $length;
$newcontent[] = $temp; $newcontent[] = $temp;
@ -375,7 +378,7 @@ class File_ASN1
$start+= $length; $start+= $length;
$remainingLength-= $length; $remainingLength-= $length;
$newcontent[] = $temp; $newcontent[] = $temp;
$this->_string_shift($content, $length); $content_pos += $length;
} }
return array( return array(
@ -399,11 +402,11 @@ class File_ASN1
//if (strlen($content) != 1) { //if (strlen($content) != 1) {
// return false; // return false;
//} //}
$current['content'] = (bool) ord($content[0]); $current['content'] = (bool) ord($content[$content_pos]);
break; break;
case FILE_ASN1_TYPE_INTEGER: case FILE_ASN1_TYPE_INTEGER:
case FILE_ASN1_TYPE_ENUMERATED: case FILE_ASN1_TYPE_ENUMERATED:
$current['content'] = new Math_BigInteger($content, -256); $current['content'] = new Math_BigInteger(substr($content, $content_pos), -256);
break; break;
case FILE_ASN1_TYPE_REAL: // not currently supported case FILE_ASN1_TYPE_REAL: // not currently supported
return false; return false;
@ -412,10 +415,10 @@ class File_ASN1
// the number of unused bits in the final subsequent octet. The number shall be in the range zero to // the number of unused bits in the final subsequent octet. The number shall be in the range zero to
// seven. // seven.
if (!$constructed) { if (!$constructed) {
$current['content'] = $content; $current['content'] = substr($content, $content_pos);
} else { } else {
$temp = $this->_decode_ber($content, $start); $temp = $this->_decode_ber($content, $start, $content_pos);
$length-= strlen($content); $length-= (strlen($content) - $content_pos);
$last = count($temp) - 1; $last = count($temp) - 1;
for ($i = 0; $i < $last; $i++) { for ($i = 0; $i < $last; $i++) {
// all subtags should be bit strings // all subtags should be bit strings
@ -433,13 +436,13 @@ class File_ASN1
break; break;
case FILE_ASN1_TYPE_OCTET_STRING: case FILE_ASN1_TYPE_OCTET_STRING:
if (!$constructed) { if (!$constructed) {
$current['content'] = $content; $current['content'] = substr($content, $content_pos);
} else { } else {
$current['content'] = ''; $current['content'] = '';
$length = 0; $length = 0;
while (substr($content, 0, 2) != "\0\0") { while (substr($content, $content_pos, 2) != "\0\0") {
$temp = $this->_decode_ber($content, $length + $start); $temp = $this->_decode_ber($content, $length + $start, $content_pos);
$this->_string_shift($content, $temp['length']); $content_pos += $temp['length'];
// all subtags should be octet strings // all subtags should be octet strings
//if ($temp['type'] != FILE_ASN1_TYPE_OCTET_STRING) { //if ($temp['type'] != FILE_ASN1_TYPE_OCTET_STRING) {
// return false; // return false;
@ -447,7 +450,7 @@ class File_ASN1
$current['content'].= $temp['content']; $current['content'].= $temp['content'];
$length+= $temp['length']; $length+= $temp['length'];
} }
if (substr($content, 0, 2) == "\0\0") { if (substr($content, $content_pos, 2) == "\0\0") {
$length+= 2; // +2 for the EOC $length+= 2; // +2 for the EOC
} }
} }
@ -462,26 +465,28 @@ class File_ASN1
case FILE_ASN1_TYPE_SET: case FILE_ASN1_TYPE_SET:
$offset = 0; $offset = 0;
$current['content'] = array(); $current['content'] = array();
while (strlen($content)) { $content_len = strlen($content);
while ($content_pos < $content_len) {
// if indefinite length construction was used and we have an end-of-content string next // if indefinite length construction was used and we have an end-of-content string next
// see paragraphs 8.1.1.3, 8.1.3.2, 8.1.3.6, 8.1.5, and (for an example) 8.6.4.2 // see paragraphs 8.1.1.3, 8.1.3.2, 8.1.3.6, 8.1.5, and (for an example) 8.6.4.2
if (!isset($current['headerlength']) && substr($content, 0, 2) == "\0\0") { if (!isset($current['headerlength']) && substr($content, $content_pos, 2) == "\0\0") {
$length = $offset + 2; // +2 for the EOC $length = $offset + 2; // +2 for the EOC
break 2; break 2;
} }
$temp = $this->_decode_ber($content, $start + $offset); $temp = $this->_decode_ber($content, $start + $offset, $content_pos);
$this->_string_shift($content, $temp['length']); $content_pos += $temp['length'];
$current['content'][] = $temp; $current['content'][] = $temp;
$offset+= $temp['length']; $offset+= $temp['length'];
} }
break; break;
case FILE_ASN1_TYPE_OBJECT_IDENTIFIER: case FILE_ASN1_TYPE_OBJECT_IDENTIFIER:
$temp = ord($this->_string_shift($content)); $temp = ord($content[$content_pos++]);
$current['content'] = sprintf('%d.%d', floor($temp / 40), $temp % 40); $current['content'] = sprintf('%d.%d', floor($temp / 40), $temp % 40);
$valuen = 0; $valuen = 0;
// process septets // process septets
while (strlen($content)) { $content_len = strlen($content);
$temp = ord($this->_string_shift($content)); while ($content_pos < $content_len) {
$temp = ord($content[$content_pos++]);
$valuen <<= 7; $valuen <<= 7;
$valuen |= $temp & 0x7F; $valuen |= $temp & 0x7F;
if (~$temp & 0x80) { if (~$temp & 0x80) {
@ -522,11 +527,11 @@ class File_ASN1
case FILE_ASN1_TYPE_UTF8_STRING: case FILE_ASN1_TYPE_UTF8_STRING:
// ???? // ????
case FILE_ASN1_TYPE_BMP_STRING: case FILE_ASN1_TYPE_BMP_STRING:
$current['content'] = $content; $current['content'] = substr($content, $content_pos);
break; break;
case FILE_ASN1_TYPE_UTC_TIME: case FILE_ASN1_TYPE_UTC_TIME:
case FILE_ASN1_TYPE_GENERALIZED_TIME: case FILE_ASN1_TYPE_GENERALIZED_TIME:
$current['content'] = $this->_decodeTime($content, $tag); $current['content'] = $this->_decodeTime(substr($content, $content_pos), $tag);
default: default:
} }