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Fixes in HTML Lexer to support HTML empty comment statements #327

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Fixes in HTML Lexer to support HTML empty comment statements #327

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9b25635
Fixes in parser to address bypass of the library and XSS attacks
jfbyers Dec 15, 2023
1ae3478
Fixes suggested by Mike Samuel
Mar 22, 2024
e8b68ef
Spacing
Mar 22, 2024
0d2f071
Merge remote-tracking branch 'origin' into bugfix/lexerHtmlComments
Sep 24, 2024
ce28bc9
Added new test
Sep 24, 2024
7408e06
Implemented change suggested by mikesamuel
Sep 24, 2024
ee341c9
Spacing
Sep 24, 2024
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31 changes: 30 additions & 1 deletion owasp-java-html-sanitizer/src/main/java/org/owasp/html/HtmlLexer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -476,6 +476,8 @@ private static enum State {
COMMENT,
COMMENT_DASH,
COMMENT_DASH_DASH,
COMMENT_DASH_DASH_BANG,
COMMENT_DASH_AFTER_BANG,
DIRECTIVE,
DONE,
BOGUS_COMMENT,
Expand Down Expand Up @@ -640,20 +642,35 @@ && canonicalElementName(start + 2, end)
case BANG:
if ('-' == ch) {
state = State.BANG_DASH;
} else if('>' == ch) { // <!> is a valid html comment
state = State.DONE;
type = HtmlTokenType.COMMENT;
} else {
state = State.DIRECTIVE;
}
break;
case BANG_DASH:
if ('-' == ch) {
state = State.COMMENT;
state = State.COMMENT_DASH_AFTER_BANG;
} else {
state = State.DIRECTIVE;
}
break;
case COMMENT_DASH_AFTER_BANG:
if ('>' == ch) { // <!--> is a valid html comment
state = State.DONE;
type = HtmlTokenType.COMMENT;
} else if ('-' == ch) { // <!---> is a valid html comment
state = State.COMMENT_DASH_AFTER_BANG;
} else {
state = State.COMMENT;
}
break;
case COMMENT:
if ('-' == ch) {
state = State.COMMENT_DASH;
} else {
state = State.COMMENT;
}
break;
case COMMENT_DASH:
Expand All @@ -665,12 +682,24 @@ && canonicalElementName(start + 2, end)
if ('>' == ch) {
state = State.DONE;
type = HtmlTokenType.COMMENT;
} else if ('!' == ch) { // --!> is also valid closing sequence
state = State.COMMENT_DASH_DASH_BANG;
} else if ('-' == ch) {
state = State.COMMENT_DASH_DASH;
} else {
state = State.COMMENT_DASH;
}
break;
case COMMENT_DASH_DASH_BANG:
if ('>' == ch) {
state = State.DONE;
type = HtmlTokenType.COMMENT;
}else if ('-' == ch) {
state = State.COMMENT_DASH;
}else {
state = State.COMMENT;
}
break;
case DIRECTIVE:
if ('>' == ch) {
type = HtmlTokenType.DIRECTIVE;
Expand Down
59 changes: 59 additions & 0 deletions owasp-java-html-sanitizer/src/test/java/org/owasp/html/HtmlLexerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,65 @@ public static final void testShortTags() {
"TAGEND: >");
}

@Test
public static final void testCommentDeclarationWith0CommentsAndXss() throws Exception
{
//check https://datatracker.ietf.org/doc/html/rfc1866#section-3.2.5
assertTokens("<!><img src=1 onError=alert(\"nice\")>",
"COMMENT: <!>",
"TAGBEGIN: <img",
"ATTRNAME: src",
"ATTRVALUE: 1",
"ATTRNAME: onError",
"ATTRVALUE: alert(\"nice\")",
"TAGEND: >"
);
}

@Test
public static final void testTextEndingWithTagOpenAndBang() throws Exception
{
//taken from https://html.spec.whatwg.org/#comments
assertTokens("<!--My favorite operators are > and <!--><a></a>",
"COMMENT: <!--My favorite operators are > and <!-->",
"TAGBEGIN: <a",
"TAGEND: >",
"TAGBEGIN: </a",
"TAGEND: >"
);
}


public static final void testDashDashBangComment() throws Exception
{
assertTokens("<!-- --!-->",
"COMMENT: <!-- --!-->"
);
}
@Test
public static final void testAbruptClosingOfEmptyComment() throws Exception
{
assertTokens("<!--><img>a<!--->b<!->c",
"COMMENT: <!-->",
"TAGBEGIN: <img",
"TAGEND: >",
"TEXT: a",
"COMMENT: <!--->",
"TEXT: b",
"SERVERCODE: <!->c"
);
}

@Test
public static final void testIncorrectlyClosedComment() throws Exception
{
assertTokens("<!-- Comment --!><img>",
"COMMENT: <!-- Comment --!>",
"TAGBEGIN: <img",
"TAGEND: >"
);
}

private static void lex(String input, Appendable out) throws Exception {
HtmlLexer lexer = new HtmlLexer(input);
int maxTypeLength = 0;
Expand Down