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HTML Api: Fix out of bounds string access #5793

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HTML Api: Fix out of bounds string access #5793

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614b220
Add test for oob string lookup
sirreal Dec 19, 2023
8bfb613
Check for in-range index
sirreal Dec 19, 2023
8579278
Fix lints
sirreal Dec 19, 2023
4e01634
Add out of range closer test
sirreal Dec 19, 2023
0aae846
Fix oob check
sirreal Dec 19, 2023
69a7965
Use stored doc_length over strlen() calls
sirreal Dec 19, 2023
8905faf
Fix lints
sirreal Dec 19, 2023
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23 changes: 14 additions & 9 deletions src/wp-includes/html-api/class-wp-html-tag-processor.php
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1113,7 +1113,7 @@ private function parse_next_tag() {

$this->token_starts_at = $at;

if ( '/' === $this->html[ $at + 1 ] ) {
if ( $doc_length > $at + 1 && '/' === $this->html[ $at + 1 ] ) {
$this->is_closing_tag = true;
++$at;
} else {
Expand Down Expand Up @@ -1147,7 +1147,7 @@ private function parse_next_tag() {
* Abort if no tag is found before the end of
* the document. There is nothing left to parse.
*/
if ( $at + 1 >= strlen( $html ) ) {
if ( $at + 1 >= $doc_length ) {
return false;
}

Expand All @@ -1161,13 +1161,13 @@ private function parse_next_tag() {
* https://html.spec.whatwg.org/multipage/parsing.html#tag-open-state
*/
if (
strlen( $html ) > $at + 3 &&
$doc_length > $at + 3 &&
'-' === $html[ $at + 2 ] &&
'-' === $html[ $at + 3 ]
) {
$closer_at = $at + 4;
// If it's not possible to close the comment then there is nothing more to scan.
if ( strlen( $html ) <= $closer_at ) {
if ( $doc_length <= $closer_at ) {
return false;
}

Expand All @@ -1185,18 +1185,18 @@ private function parse_next_tag() {
* See https://html.spec.whatwg.org/#parse-error-incorrectly-closed-comment
*/
--$closer_at; // Pre-increment inside condition below reduces risk of accidental infinite looping.
while ( ++$closer_at < strlen( $html ) ) {
while ( ++$closer_at < $doc_length ) {
$closer_at = strpos( $html, '--', $closer_at );
if ( false === $closer_at ) {
return false;
}

if ( $closer_at + 2 < strlen( $html ) && '>' === $html[ $closer_at + 2 ] ) {
if ( $closer_at + 2 < $doc_length && '>' === $html[ $closer_at + 2 ] ) {
$at = $closer_at + 3;
continue 2;
}

if ( $closer_at + 3 < strlen( $html ) && '!' === $html[ $closer_at + 2 ] && '>' === $html[ $closer_at + 3 ] ) {
if ( $closer_at + 3 < $doc_length && '!' === $html[ $closer_at + 2 ] && '>' === $html[ $closer_at + 3 ] ) {
$at = $closer_at + 4;
continue 2;
}
Expand All @@ -1209,7 +1209,7 @@ private function parse_next_tag() {
* https://html.spec.whatwg.org/multipage/parsing.html#tag-open-state
*/
if (
strlen( $html ) > $at + 8 &&
$doc_length > $at + 8 &&
'[' === $html[ $at + 2 ] &&
'C' === $html[ $at + 3 ] &&
'D' === $html[ $at + 4 ] &&
Expand All @@ -1233,7 +1233,7 @@ private function parse_next_tag() {
* https://html.spec.whatwg.org/multipage/parsing.html#tag-open-state
*/
if (
strlen( $html ) > $at + 8 &&
$doc_length > $at + 8 &&
( 'D' === $html[ $at + 2 ] || 'd' === $html[ $at + 2 ] ) &&
( 'O' === $html[ $at + 3 ] || 'o' === $html[ $at + 3 ] ) &&
( 'C' === $html[ $at + 4 ] || 'c' === $html[ $at + 4 ] ) &&
Expand Down Expand Up @@ -1290,6 +1290,11 @@ private function parse_next_tag() {
* See https://html.spec.whatwg.org/#parse-error-invalid-first-character-of-tag-name
*/
if ( $this->is_closing_tag ) {
// No chance of finding a closer
if ( $at + 3 > $doc_length ) {
return false;
}

$closer_at = strpos( $html, '>', $at + 3 );
if ( false === $closer_at ) {
return false;
Expand Down
18 changes: 18 additions & 0 deletions tests/phpunit/tests/html-api/wpHtmlTagProcessor.php
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Original file line number Diff line number Diff line change
Expand Up @@ -2428,6 +2428,24 @@ public function test_updating_attributes_in_malformed_html( $html, $expected ) {
);
}

/**
* @covers WP_HTML_Tag_Processor::next_tag
*/
public function test_handles_malformed_taglike_open_short_html() {
$p = new WP_HTML_Tag_Processor( '<' );
$result = $p->next_tag();
$this->assertFalse( $result, 'Did not handle "<" html properly.' );
}

/**
* @covers WP_HTML_Tag_Processor::next_tag
*/
public function test_handles_malformed_taglike_close_short_html() {
$p = new WP_HTML_Tag_Processor( '</ ' );
$result = $p->next_tag();
$this->assertFalse( $result, 'Did not handle "</ " html properly.' );
}

/**
* Data provider.
*
Expand Down