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There were two bugs where parameter-entity references could lead to an
unexpected change of the input buffer in xmlParseNameComplex and
xmlDictLookup being called with an invalid pointer.
Percent sign in DTD Names
=========================
The NEXTL macro used to call xmlParserHandlePEReference. When parsing
"complex" names inside the DTD, this could result in entity expansion
which created a new input buffer. The fix is to simply remove the call
to xmlParserHandlePEReference from the NEXTL macro. This is safe because
no users of the macro require expansion of parameter entities.
- xmlParseNameComplex
- xmlParseNCNameComplex
- xmlParseNmtoken
The percent sign is not allowed in names, which are grammatical tokens.
- xmlParseEntityValue
Parameter-entity references in entity values are expanded but this
happens in a separate step in this function.
- xmlParseSystemLiteral
Parameter-entity references are ignored in the system literal.
- xmlParseAttValueComplex
- xmlParseCharDataComplex
- xmlParseCommentComplex
- xmlParsePI
- xmlParseCDSect
Parameter-entity references are ignored outside the DTD.
- xmlLoadEntityContent
This function is only called from xmlStringLenDecodeEntities and
entities are replaced in a separate step immediately after the function
call.
This bug could also be triggered with an internal subset and double
entity expansion.
This fixes bug 766956 initially reported by Wei Lei and independently by
Chromium's ClusterFuzz, Hanno Böck, and Marco Grassi. Thanks to everyone
involved.
xmlParseNameComplex with XML_PARSE_OLD10
========================================
When parsing Names inside an expanded parameter entity with the
XML_PARSE_OLD10 option, xmlParseNameComplex would call xmlGROW via the
GROW macro if the input buffer was exhausted. At the end of the
parameter entity's replacement text, this function would then call
xmlPopInput which invalidated the input buffer.
There should be no need to invoke GROW in this situation because the
buffer is grown periodically every XML_PARSER_CHUNK_SIZE characters and,
at least for UTF-8, in xmlCurrentChar. This also matches the code path
executed when XML_PARSE_OLD10 is not set.
This fixes bugs 781205 (CVE-2017-9049) and 781361 (CVE-2017-9050).
Thanks to Marcel Böhme and Thuan Pham for the report.
Additional hardening
====================
A separate check was added in xmlParseNameComplex to validate the
buffer size.
The code in xmlParseStartTag2 must handle the case that the input
buffer was grown and reallocated which can invalidate pointers to
attribute values. Before, this was handled by detecting changes of
the input buffer "base" pointer and, in case of a change, jumping
back to the beginning of the function and reparsing the start tag.
The major problem of this approach is that whether an input buffer is
reallocated is nondeterministic, resulting in seemingly random test
failures. See the mailing list thread "runtest mystery bug: name2.xml
error case regression test" from 2012, for example.
If a reallocation was detected, the code also made no attempts to
continue parsing in case of errors which makes a difference in
the lax "recover" mode.
Now we store the current input buffer "base" pointer for each (not
separately allocated) attribute in the namespace URI field, which isn't
used until later. After the whole start tag was parsed, the pointers
to the attribute values are reconstructed using the offset between the
new and the old input buffer. This relies on arithmetic on dangling
pointers which is technically undefined behavior. But it seems like
the easiest and most efficient fix and a similar approach is used in
xmlParserInputGrow.
This changes the error output of several tests, typically making it
more verbose because we try harder to continue parsing in case of
errors.
(Another possible solution is to check not only the "base" pointer
but the size of the input buffer as well. But this would result in
even more reparsing.)
Triggered in mixed content ELEMENT declarations if there's an invalid
name after the first valid name:
<!ELEMENT para (#PCDATA|a|<invalid>)*>
Found with libFuzzer and ASan.
For https://bugzilla.gnome.org/show_bug.cgi?id=772726
* include/libxml/parser.h: Add a new parser flag XML_PARSE_NOXXE
* elfgcchack.h, xmlIO.h, xmlIO.c: associated loading routine
* include/libxml/xmlerror.h: new error raised
* xmllint.c: adds --noxxe flag to activate the option
For https://bugzilla.gnome.org/show_bug.cgi?id=762100
When we detect a recusive entity we should really not
build the associated data, moreover if someone bypass
libxml2 fatal errors and still tries to serialize a broken
entity make sure we don't risk to get ito a recursion
* parser.c: xmlParserEntityCheck() don't build if entity loop
were found and remove the associated text content
* tree.c: xmlStringGetNodeList() avoid a potential recursion
For https://bugzilla.gnome.org/show_bug.cgi?id=759573
* parser.c:
(xmlParseElementDecl): Return early on invalid input to fix
non-minimized test case (759573-2.xml). Otherwise the parser
gets into a bad state in SKIP(3) at the end of the function.
(xmlParseConditionalSections): Halt parsing when hitting invalid
input that would otherwise caused xmlParserHandlePEReference()
to recurse unexpectedly. This fixes the minimized test case
(759573.xml).
* result/errors/759573-2.xml: Add.
* result/errors/759573-2.xml.err: Add.
* result/errors/759573-2.xml.str: Add.
* result/errors/759573.xml: Add.
* result/errors/759573.xml.err: Add.
* result/errors/759573.xml.str: Add.
* test/errors/759573-2.xml: Add.
* test/errors/759573.xml: Add.
For https://bugzilla.gnome.org/show_bug.cgi?id=759020
* parser.c:
(xmlParseStartTag2): Attribute strings are only valid if the
base does not change, so add another check where the base may
change. Make sure to set 'attvalue' to NULL after freeing it.
* result/errors/759020.xml: Added.
* result/errors/759020.xml.err: Added.
* result/errors/759020.xml.str: Added.
* test/errors/759020.xml: Added test case.
For https://bugzilla.gnome.org/show_bug.cgi?id=761430
libfuzzer regression testing exposed another case where the parser would
fetch content of an external entity while not in validating mode.
Plug that hole
* parser.c:
(xmlParseNCNameComplex): Store start position instead of a
pointer to the name since the underlying buffer may change,
resulting in a stale pointer being used.
* result/errors/759398.xml: Added.
* result/errors/759398.xml.err: Added.
* result/errors/759398.xml.str: Added.
* test/errors/759398.xml: Added test case.
* parser.c:
(xmlParseEndTag2): Add bounds checks before dereferencing
ctxt->input->cur past the end of the buffer, or incrementing the
pointer past the end of the buffer.
* result/errors/758588.xml: Add test result.
* result/errors/758588.xml.err: Ditto.
* result/errors/758588.xml.str: Ditto.
* test/errors/758588.xml: Add regression test.
For https://bugzilla.gnome.org/show_bug.cgi?id=765207
CVE-2016-3705
The functions xmlParserEntityCheck() and xmlParseAttValueComplex() used to call
xmlStringDecodeEntities() in a recursive context without incrementing the
'depth' counter in the parser context. Because of that omission, the parser
failed to detect attribute recursions in certain documents before running out
of stack space.
* parser.c:
(xmlCheckCdataPush): Add 'complete' argument to describe whether
the buffer passed in is the whole CDATA buffer, or if there is
more data to parse. If there is more data to parse, don't
return a negative value for an invalid multi-byte UTF-8
character that is split between buffers.
(xmlParseTryOrFinish): Pass 'complete' argument to
xmlCheckCdataPush() as appropriate.
* result/cdata-2-byte-UTF-8.xml: Added.
* result/cdata-2-byte-UTF-8.xml.rde: Added.
* result/cdata-2-byte-UTF-8.xml.rdr: Added.
* result/cdata-2-byte-UTF-8.xml.sax: Added.
* result/cdata-2-byte-UTF-8.xml.sax2: Added.
* result/cdata-3-byte-UTF-8.xml: Added.
* result/cdata-3-byte-UTF-8.xml.rde: Added.
* result/cdata-3-byte-UTF-8.xml.rdr: Added.
* result/cdata-3-byte-UTF-8.xml.sax: Added.
* result/cdata-3-byte-UTF-8.xml.sax2: Added.
* result/cdata-4-byte-UTF-8.xml: Added.
* result/cdata-4-byte-UTF-8.xml.rde: Added.
* result/cdata-4-byte-UTF-8.xml.rdr: Added.
* result/cdata-4-byte-UTF-8.xml.sax: Added.
* result/cdata-4-byte-UTF-8.xml.sax2: Added.
* result/noent/cdata-2-byte-UTF-8.xml: Added.
* result/noent/cdata-3-byte-UTF-8.xml: Added.
* result/noent/cdata-4-byte-UTF-8.xml: Added.
* test/cdata-2-byte-UTF-8.xml: Added.
* test/cdata-3-byte-UTF-8.xml: Added.
* test/cdata-4-byte-UTF-8.xml: Added.
- Add tests and results. Only 'make Readertests XMLPushtests'
fails prior to the fix.
For https://bugzilla.gnome.org/show_bug.cgi?id=759671
when the end of the internal subset isn't properly detected
xmlParseInternalSubset should just return instead of trying
to process input further.
For https://bugzilla.gnome.org/show_bug.cgi?id=756525
handle properly the case where we popped out of the current entity
while processing a start tag
Reported by Kostya Serebryany @ Google
This slightly modifies the output of 754946 in regression tests
Unify the various place where either xmlStopParser was called
(which resets the error as a side effect) and places where we
used ctxt->instate = XML_PARSER_EOF to stop further processing
The problem is doing it in a consistent and safe fashion
It's more complex than just setting ctxt->instate = XML_PARSER_EOF
Update the public function to reuse that new internal routine
For https://bugzilla.gnome.org/show_bug.cgi?id=756733
It is one case where the code in place to detect entities expansions
failed to exit when the situation was detected, leading to DoS
Problem reported by Kostya Serebryany @ Google
Patch provided by David Drysdale @ Google
For https://bugzilla.gnome.org/show_bug.cgi?id=756527
and was also raised by Chromium team in the past
When we hit a convwersion failure when switching encoding
it is bestter to stop parsing there, this was treated as a
fatal error but the parser was continuing to process to extract
more errors, unfortunately that makes little sense as the data
is obviously corrupt and can potentially lead to unexpected behaviour.
an off by one mistake in the change, led to error on correct
document where the end of the included entity was exactly
the end of the conditional section, leading to regtest failure
Which happen after the previous fix to
https://bugzilla.gnome.org/show_bug.cgi?id=756456
But stopping the parser and exiting we didn't pop the intermediary entities
and doing the SKIP there applies on an input which may be too small
For https://bugzilla.gnome.org/show_bug.cgi?id=754946
When hitting the end of the current input buffer while parsing
a name we could end up loosing the beginning of the name, which
led to various issues.
For https://bugzilla.gnome.org/show_bug.cgi?id=751631
If we fail conversing the current input stream while
processing the encoding declaration of the XMLDecl
then it's safer to just abort there and not try to
report further errors.
For https://bugzilla.gnome.org/show_bug.cgi?id=744980
The error handling of Conditional Section also need to be
straightened as the structure of the document can't be
guessed on a failure there and it's better to stop parsing
as further errors are likely to be irrelevant.
For https://bugzilla.gnome.org/show_bug.cgi?id=744980
There are times, like on unterminated entities that it's preferable to
stop parsing, even if that means less error reporting. Entities are
feeding the parser on further processing, and if they are ill defined
then it's possible to get the parser to bug. Also do the same on
Conditional Sections if the input is broken, as the structure of
the document can't be guessed.
For https://bugzilla.gnome.org/show_bug.cgi?id=738805
The fix for CVE-2014-3660 introduced a regression in some case
where entity substitution is required and the entity is used
first in anotther entity referenced from an attribute value
When the xml parser encounters an xml encoding in an xml header while
configured with option XML_PARSE_IGNORE_ENC, it fails to free memory
allocated for storing the encoding.
The patch below fixes this.
How to reproduce:
1. Change doc/examples/parse4.c to add xmlCtxtUseOptions(ctxt,
XML_PARSE_IGNORE_ENC); after the call to xmlCreatePushParserCtxt.
2. Rebuild
3. run the following command from the top libxml2 directory:
LD_LIBRARY_PATH=.libs/ valgrind --leak-check=full
./doc/examples/.libs/parse4 ./test.xml , where test.xml contains
following
input:
<?xml version="1.0" encoding="UTF-81" ?><hi/>
valgrind will report:
==1964== 10 bytes in 1 blocks are definitely lost in loss record 1 of 1
==1964== at 0x4C272DB: malloc (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1964== by 0x4E88497: xmlParseEncName (parser.c:10224)
==1964== by 0x4E888FE: xmlParseEncodingDecl (parser.c:10295)
==1964== by 0x4E89630: xmlParseXMLDecl (parser.c:10534)
==1964== by 0x4E8B737: xmlParseTryOrFinish (parser.c:11293)
==1964== by 0x4E8E775: xmlParseChunk (parser.c:12283)
Signed-off-by: Bart De Schuymer <bart at amplidata com>
For https://bugzilla.gnome.org/show_bug.cgi?id=672539
Reported by Axel Miller <axel.miller@ppi.de>
Consider the following start-tag:
<x xmlns=""version="">
The start-tag does not conform to the rule
[40] STag ::= '<' Name (S Attribute)* S? '>'
since there is no whitespace in front of the attribute "version".
Thus, libxml2 should reject the start-tag.
But it doesn't:
$ echo '<x xmlns=""version=""/>' | xmllint -
<?xml version="1.0"?>
<x xmlns="" version=""/>
The error seems to happen only if there is a namespace declaration in
front of
the attribute. A missing whitespace between other attributes is handled
correctly:
$ echo '<x someattr=""version=""/>' | xmllint -
-:1: parser error : attributes construct error
<x someattr=""version=""/>
^
[...]
For https://bugzilla.gnome.org/show_bug.cgi?id=734280
libxml2 reports wrong error column numbers (field int2 in xmlError)
in structured error handler, after parsing XML attribute values.
Example XML:
<?xml version="1.0" encoding="UTF-8"?>
<root
xmlns="urn:colbug">&</root>
<!--
1 2 3 4
1234567890123456789012345678901234567890
-->
Expected location of the error would be line 3, column 21.
The actual location of the error is line 3, column 9:
$ ./xmlparse colbug2.xml
colbug2.xml:3:9: xmlParseEntityRef: no name
The 12 characters of the xmlns attribute value "urn:colbug" are
not accounted for in the error column value.
For https://bugzilla.gnome.org/show_bug.cgi?id=734276
libxml2 reports wrong error column numbers (field int2 in xmlError)
in structured error handler, after an XML declaration containing
whitespace.
Example XML:
<?xml version="1.0" encoding="UTF-8" ?><root>&</root>
<!--
1 2 3 4 5 6
123456789012345678901234567890123456789012345678901234567890
-->
Expected location of the error would be line 1, column 53.
The actual location of the error is line 1, column 44:
$ ./xmlparse colbug1.xml
colbug1.xml:1:44: xmlParseEntityRef: no name
A number of issues have been raised after the fix, and this patch
tries to correct all of them, though most were related to
postvalidation.
https://bugzilla.gnome.org/show_bug.cgi?id=730290
and other reports on list, off-list and on Red Hat bugzilla
