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This makes the logic in UTF16BEToUTF8() match UTF16LEToUTF8().
* encoding.c:
(UTF16LEToUTF8):
- Fix comment to describe what the code does.
(UTF16BEToUTF8):
- Fix undefined behavior which was applied to UTF16LEToUTF8() in
2f9382033e.
- Add bounds check to while() loop which was applied to
UTF16LEToUTF8() in be803967db.
- Do not return -2 when (in >= inend) to fix the bug. This was
applied to UTF16LEToUTF8() in 496a1cf592.
- Inline (<< 8) statements to match UTF16LEToUTF8().
Add the following tests and results:
test/text-4-byte-UTF-16-BE-offset.xml
test/text-4-byte-UTF-16-BE.xml
test/text-4-byte-UTF-16-LE-offset.xml
test/text-4-byte-UTF-16-LE.xml
Readd the XML_ERR_TAG_NOT_FINISHED error on unexpected EOF which was
removed in commit 62150ed2.
This commit also introduced a regression for direct users of
xmlParseContent. Unclosed tags weren't checked.
Commit 62150ed2 introduced a small regression in the error messages for
mismatched tags. This typically only affected messages after the first
mismatch, but with custom SAX handlers all line numbers would be off.
This also fixes line numbers in the SAX push parser which were never
handled correctly.
Implement section "4.6 Predefined Entities" of the XML 1.0 spec and
check whether redeclarations of predefined entities match the original
definitions.
Note that some test cases declared
<!ENTITY lt "<">
But the XML spec clearly states that this is illegal:
> If the entities lt or amp are declared, they MUST be declared as
> internal entities whose replacement text is a character reference to
> the respective character (less-than sign or ampersand) being escaped;
> the double escaping is REQUIRED for these entities so that references
> to them produce a well-formed result.
Also fixes#217 but the connection is only tangential. The integer
overflow discovered by fuzzing was more related to the fact that various
parts of the parser disagreed on whether to prefer predefined entities
over their redeclarations. The whole situation is a mess and even
depends on legacy parser options. But now that redeclarations are
validated, it shouldn't make a difference.
As noted in the added comment, this is also one of the cases where
overly defensive checks can hide interesting logic bugs from fuzzers.
The code wasn't dead after all, but I can see no reason in delaying
the XPointer evaluation. This could lead to nodes included earlier
appearing in XPointer results.
When creating XML_XINCLUDE_START nodes, the children of the original
xi:include node must be freed, otherwise fallback content is copied
twice, doubling runtime and memory consumption for each nested
xi:fallback/xi:include pair.
Found with libFuzzer.
Fix a few remaining cases where the HTML push parser would scan more
content during lookahead than being parsed later.
Make sure that htmlParseDocTypeDecl consumes all content up to the
final '>' in case of errors. The old comment said "We shouldn't try to
resynchronize", but ignoring invalid content is also what the HTML5
spec mandates.
Likewise, make htmlParseEndTag skip to the final '>' in invalid end
tags even if not in recovery mode. This is probably the most visible
change in practice and leads to different output for some tests but is
also more in line with HTML5.
Make sure that htmlParsePI and htmlParseComment don't abort if invalid
characters are encountered but log an error and ignore the character.
Change some other end-of-buffer checks to test for a zero byte instead
of relying on IS_CHAR.
Fix usage of IS_CHAR macro in htmlParseScript.
- Bug 757711: heap-buffer-overflow in xmlFAParsePosCharGroup
<https://bugzilla.gnome.org/show_bug.cgi?id=757711>
- Bug 783015 - Integer-overflow in xmlFAParseQuantExact
<https://bugzilla.gnome.org/show_bug.cgi?id=783015>
(Regexptests): Add support for checking stderr output when
running regexp tests. This makes it possible to check in test
cases that fail and not see false-positive error output when
running the tests. Unlike other libxml2 test suites, if there
is no stderr output, no *.err file needs to be created.
Commit eeb99329 removed an important optimization avoiding quadratic
runtime when repeatedly scanning the input buffer for terminating
characters in the HTML push parser. The related bug is
https://bugzilla.gnome.org/show_bug.cgi?id=444994
Make sure that ctxt->checkIndex is always written and store additional
parser state in ctxt->inSubset which is unused in the HTML parser.
Found by OSS-Fuzz.
Despite the comment, I can't see a reason why external entities must be
loaded in the SAX handler. For external entities, the handler is
typically first invoked via xmlParseReference which will later load the
entity on its own if it wasn't loaded yet.
The old code also lead to duplicated SAX events which makes it
basically impossible to reuse xmlSAX2GetEntity for a custom SAX parser.
See the change to the expected test output.
Note that xmlSAX2GetEntity was loading the entity via
xmlParseCtxtExternalEntity while xmlParseReference uses
xmlParseExternalEntityPrivate. In the previous commit, the two
functions were merged, trying to compensate for some slight differences
between the two mostly identical implementations.
But the more urgent reason for this change is that xmlParseReference
has the facility to abort early when recursive entities are detected,
avoiding what could practically amount to an infinite loop.
If you want to backport this change, note that the previous three
commits are required as well:
f9ea1a24 Fix copying of entities in xmlParseReference
5c7e0a9a Copy some XMLReader option flags to parser context
1a3e584a Merge code paths loading external entities
Found by OSS-Fuzz.
Before, reader mode would end up in a branch that didn't handle
entities with multiple children and failed to update ent->last, so the
hack copying the "extra" reader data wouldn't trigger. Consequently,
some empty nodes in entities are correctly detected now in the test
suite. (The detection of empty nodes in entities is still buggy,
though.)
libxml2 correctly rejects any4_0.xsd as invalid schema. I can't figure
out what the intent behind this test case was. Simply adjust the
expected output to match the current behavior.
Closes#92.
Previously, test/relaxng/ambig_name-class2.xml would fail to validate
against test/relaxng/ambig_name-class2.rng:
> test/relaxng/ambig_name-class2.rng:4:
> element attribute: Relax-NG parser error :
> Found anyName attribute without oneOrMore ancestor
> Relax-NG schema test/relaxng/ambig_name-class2.rng failed to compile
Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
Previously, test/relaxng/ambig_name-class.xml would fail to validate
for a simple reason -- interleave within "open-name-class" context
is supposed to be fine with whatever else is pending the consumption,
since effectively, it's unrelated from a higher parsing perspective.
Signed-off-by: Jan Pokorný <jpokorny@redhat.com>
Consolidate code paths evaluating XPath predicates and filters.
Don't push context node on stack when evaluating predicates. I have no
idea why this was done. It seems completely useless and trying to pop
the context node from a corrupted stack has already caused security
issues.
Filter nodesets in-place and don't create node sets with NULL gaps which
allows to simplify merging a great deal. Simply move matched nodes
backward and create a compact node set.
Merge xmlXPathCompOpEvalPositionalPredicate into
xmlXPathCompOpEvalPredicate.
Rewrite conversion of double to int in xmlXPathSubstringFunction, adding
range checks to avoid undefined behavior. Make sure to add start and
length as floating-point numbers before converting to int. Fix a bug
when rounding negative start indices.
Remove unneeded calls to xmlXPathIs{Inf,NaN} and rely on IEEE math
instead. Avoid computing the string length. xmlUTF8Strsub works as
expected if the length of the requested substring exceeds the input.
Found with libFuzzer and UBSan.
When including a grammar from another grammar, we need to make sure that any
redefines of starts and includes that that grammar does inside any of its
include elements are also removed.
The pattern nameClass allows for nested choice elements, for example
<name>
<choice>
<choice>
<name>a</name>
<name>b</name>
</choice>
<name>c</name>
</choice>
</name>
which is semantically equivalent to
<name>
<choice>
<name>a</name>
<name>b</name>
<name>c</name>
</choice>
</name>
The old code didn’t handle this correctly, as it never expected a choice inside
another choice. This patch fixes this by flattening any nested choices.
This pattern of nested choice elements comes up in RELAX NG simplification,
where all choice elements are rewritten in this nested manner, see section 4.12
of the RELAX NG specification.
RELAX NG allows for div elements inside of include elements. We need to look
inside those div elements for start and define elements that may be redefining
start and define elements in the included grammar.
Fix two bugs in xmlXPathNodeValHash which could lead to errors when
comparing nodesets to strings:
- Only use contents of text nodes to compute the hash for element nodes.
Comments, PIs, and other node types don't affect the string-value and
must be ignored.
- Reset `string` to NULL for node types other than text.
Reported by Aleksei on the mailing list:
https://mail.gnome.org/archives/xml/2017-September/msg00016.html
This reverts commit 79c8a6b which caused a serious regression in
streaming mode.
Also reverts part of commit 52ceced "Fix infinite loops with push
parser in recovery mode".
Fixes bug 786554.
When expanding a parameter entity in a DTD, infinite recursion could
lead to an infinite loop or memory exhaustion.
Thanks to Wei Lei for the first of many reports.
Fixes bug 759579.
Now that replacement of parameter entities goes exclusively through
xmlSkipBlankChars, we can account for the surrounding space characters
there and remove the "blanks wrapper" hack.
Pop all extra input streams before resetting the input. Otherwise,
a call to xmlPopInput could make input available again.
Also set input->end to input->cur.
Changes the test output for some error tests. Unfortunately, some
fuzzed test cases were added to the test suite without manual cleanup.
This makes it almost impossible to review the impact of later changes
on the test output.
Make sure to finish all entities in the internal subset. Nevertheless,
readd a sanity check in xmlParseStartTag2 that was lost in my previous
commit. Also add a sanity check in xmlPopInput. Popping an input
unexpectedly was the source of many recent memory bugs. The check
doesn't mitigate such issues but helps with diagnosis.
Always base entity boundary checks on the input ID, not the input
pointer. The pointer could have been reallocated to the old address.
Always throw a well-formedness error if a boundary check fails. In a
few places, a validity error was thrown.
Fix a few error codes and improve indentation.
- Silence test output.
- Clean up after doc/examples tests.
- Adjust expected output for script tests.
- Add missing results for relaxng/pattern3
There are still two test failures I can't comment on:
- regexp/bug316338
- schemas/any4_0
test/HTML/758518-entity.html exposed a bug in pushParseTest() in
runtest.c which assumed that an input file was at least 4 bytes long.
That test case is only 3 bytes, so we now take the minimum of 4 bytes
or the length of the test input. We also now use 'chunkSize' in place
of the hard-coded value '1024' later in the function.
Before, truncated UTF-8 sequences at the end of a file were treated as
EOF. Create an error message containing the offending bytes.
xmlStringCurrentChar would also print characters from the input stream,
not the string it's working on.
xmlSnprintfElementContent failed to correctly check the available
buffer space in two locations.
Fixes bug 781333 (CVE-2017-9047) and bug 781701 (CVE-2017-9048).
Thanks to Marcel Böhme and Thuan Pham for the report.
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.)
Don't count leading zeros towards the fraction size limit. This allows
to parse numbers like
0.0000000000000000000000000000000000000000000000000000000001
which is the only standard-conformant way to represent such numbers, as
scientific notation isn't allowed in XPath 1.0. (It is allowed in XPath
2.0 and in libxml2 as an extension, though.)
Overall accuracy is still bad, see bug 783238.
Use the C library's floor and ceil functions. The old code was overly
complicated for no apparent reason and could result in undefined
behavior when handling NaNs (found with afl-fuzz and UBSan).
Fix wrong comment in xmlXPathRoundFunction. The implementation was
already following the spec and rounding half up.
When traversing the "preceding" axis from an attribute node, we must
first go up to the attribute's containing element. Otherwise, text
children of other attributes could be returned. This made it possible
to hit a code path in xmlXPathNextAncestor which contained another bug:
The attribute node was initialized with the context node instead of the
current node. Normally, this code path is only hit via
xmlXPathNextAncestorOrSelf in which case the current and context node
are the same.
The combination of the two bugs could result in an infinite loop, found
with libFuzzer.
Traversing the "following" and the "preceding" axis from namespace nodes
should be handled similarly. This wasn't supported at all previously.
The old code would invoke the broken xmlXPtrRangeToFunction. range-to
isn't really a function but a special kind of location step. Remove
this function and always handle range-to in the XPath code.
The old xmlXPtrRangeToFunction could also be abused to trigger a
use-after-free error with the potential for remote code execution.
Found with afl-fuzz.
Fixes CVE-2016-5131.
For https://bugzilla.gnome.org/show_bug.cgi?id=758606
* parserInternals.c:
(xmlNextChar): Add an test to catch other issues on ctxt->input
corruption proactively.
For non-UTF-8 charsets, xmlNextChar() failed to check for the end
of the input buffer and would continuing reading. Fix this by
pulling out the check for the end of the input buffer into common
code, and return if we reach the end of the input buffer
prematurely.
* result/HTML/758606.html: Added.
* result/HTML/758606.html.err: Added.
* result/HTML/758606.html.sax: Added.
* result/HTML/758606_2.html: Added.
* result/HTML/758606_2.html.err: Added.
* result/HTML/758606_2.html.sax: Added.
* test/HTML/758606.html: Added test case.
* test/HTML/758606_2.html: Added test case.
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.
From https://bugzilla.gnome.org/show_bug.cgi?id=758518
Happens when a file has a name getting parsed, but no valid encoding
set, so libxml has to guess what the encoding is. This patch detects
when the buffer location changes, and if it does, restarts the parsing
of the name.
This slightly change a couple of regression tests output
* 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.
Reviewed by David Kilzer.
* HTMLparser.c:
(htmlParseName): Add bounds check.
(htmlParseNameComplex): Ditto.
* result/HTML/758605.html: Added.
* result/HTML/758605.html.err: Added.
* result/HTML/758605.html.sax: Added.
* runtest.c:
(pushParseTest): The input for the new test case was so small
(4 bytes) that htmlParseChunk() was never called after
htmlCreatePushParserCtxt(), thereby creating a false positive
test failure. Fixed by using a do-while loop so we always call
htmlParseChunk() at least once.
* test/HTML/758605.html: Added.
* 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.
Make sure that xmlXPathNodeSetAddNs is called for namespace nodes when
matched with a namespace::node() step. This correctly sets the parent
of namespace nodes. Note that xmlXPathNodeSetAddNs must only be called
if working on the namespace axis. Otherwise, the context node is not
the parent of the namespace node and the standard XP_TEST_HIT macro
must be invoked. This explains the errors in the C14N tests that the
old TODO comment mentioned.
The NCName parser would allow any NameChar as start character. For
example, the following XPath expressions would compile:
self::-abc
self::0abc
self::.abc
Add missing test results to fix the following errors when
running "make Schemastests":
## Schemas regression tests
diff: ./result/schemas/regexp-char-ref_0_0.err: No such file or directory
diff: ./result/schemas/regexp-char-ref_1_0.err: No such file or directory
* result/schemas/regexp-char-ref_0_0.err: Added.
* result/schemas/regexp-char-ref_1_0.err: Added.
* 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
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=737840
the fix for 724903 introduced a regression on external entities carrying
IDs, revert that patch in part and add a specific test to avoid readding it
If the context node is an attribute, the attribute itself is on the
descendant-or-self axis. The principal node type of this axis is element,
so the only node test that can return the attribute is "node()". In other
words, "@attr/descendant-or-self::node()" is equivalent to "@attr".
This matches the behavior of Saxon-CE.
https://bugzilla.gnome.org/show_bug.cgi?id=698550
Somehow the behaviour of the internal parser routine changed
slightly when encountering CR/LF, which led to a bug when
parsing document with non-ascii Names
For https://bugzilla.gnome.org/show_bug.cgi?id=681822
Regardless if the option HTML_PARSE_NOBLANKS is set or not, blank nodes
are removed from a HTML document, for example:
<html>
<head>
<title>This is a test.</title>
</head>
<body>
<p>This is a test.</p>
</body>
</html>
is read as:
<html><head><title>This is a test.</title></head><body>
<p>This is a test.</p>
</body></html>
This changes the default behaviour but the old behaviour is available
as expected when using the parser flag HTML_PARSE_NOBLANKS
Based on original patch from Igor Ignatyuk <igor_ignatiouk@hotmail.com>
* HTMLparser.c: change various places in the parser where ignorable_space
SAX callback was called without checking for the parser flag preference
* xmllint.c: make sure we use the new flag even for HTML parsing
* result/HTML/*: this modifies the output of a number of tests
Unless explicietely asked for when validating or replacing entities
with their value. Problem pointed out by Tom Lane <tgl@redhat.com>
* parser.c: do not load external parsed entities unless needed
* test/errors/extparsedent.xml result/errors/extparsedent.xml*:
add a regression test to avoid change of the behaviour in the future
For https://bugzilla.gnome.org/show_bug.cgi?id=615785
When the <noscript> is found, <head> is closed and a <body> element is created.
The real <body id="xxx"> gets skipped over, so I can't see any of the
body's attributes.
Just don't close <head> when encountering a <noscript>
Add a regression test too
For https://bugzilla.gnome.org/show_bug.cgi?id=609796
Libxml2 fails to validate an instance document against a schema if an element
whose type is a complex extension of some base type with an optional child
element and that child element is not specified in the instance document. For
example, suppose I have some complex type BaseType that is defined to have one
child element in a sequence group that has minOccurs set to 0
