[xmlsec] A really strange case of failing xpointer(id('...'))

[Max Motovilov]

libxml2 came from the same rpm repo as before. In fact I have what I'm 
pretty sure is an identical VM instance w/CentOS and same versions of 
libxml2 and libxmlsec1. The older version of my software -- which is a 
very simple Node.js binding for libxmlsec1 -- works there just fine. The 
code did not change between the new and old versions at all -- I have 
simply recompiled it against newer versions of Node.js runtime and 
libxml2 binding library (libxmljs). This newer version does work on my 
local Mint instance but, like I said, both the libxml2 and libxmlsec1 
are more recent there as well. My only trail right now is possible 
incompatibility between libxmljs and older libxml2 OR between the 
documents libxmljs creates with libxml2 AND the way libxmlsec1 uses them 
-- the last one sounds rather fishy even to myself :(

...Max...

> Weird indeed. The document and DTD look good to me but apparently ID
> attribute is not recognized. May be there were some changes in LibXML2?
> Or may be LibXML2 was not compiled with XPointer support?
>
> Aleksey
>
> On 8/23/13 9:44 AM, Max Motovilov wrote:
>> Happening to me in the code that's previously been working for quite a
>> while. Here's the document I pass via its <Signature> element into
>> xmlSecDSigCtxSign() :
>>
>> =========
>> <?xml version="1.0" encoding="UTF-8" standalone="no"?>
>> <!DOCTYPE AuthnRequest [
>> <!ELEMENT AuthnRequest (#PCDATA)>
>> <!ATTLIST AuthnRequest ID ID #IMPLIED>
>> ]>
>> <AuthnRequest xmlns="urn:oasis:names:tc:SAML:2.0:protocol" ID="login"
>> Destination="http://10.0.25.17:8080/cosmosDev/web/idp/SSO"
>> IssueInstant="2013-08-23T18:39:25Z" Version="2.0">
>>    <Issuer
>> xmlns="urn:oasis:names:tc:SAML:2.0:assertion">http://10.0.26.16/ssoRequest</Issuer>
>>
>>    <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
>>      <SignedInfo>
>>        <CanonicalizationMethod
>> Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315#WithComments"/>
>>        <SignatureMethod
>> Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"/>
>>        <Reference URI="#login">
>>          <Transforms>
>>            <Transform
>> Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
>>          </Transforms>
>>          <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
>>          <DigestValue/>
>>        </Reference>
>>      </SignedInfo>
>>      <SignatureValue/>
>>    </Signature>
>> </AuthnRequest>
>> =========
>>
>> and here's the traceback I get:
>>
>> =========
>> func=xmlSecXPathDataExecute:file=xpath.c:line=273:obj=unknown:subj=xmlXPtrEval:error=5:libxml2
>>
>> library function failed:expr=xpointer(id('login'))
>> func=xmlSecXPathDataListExecute:file=xpath.c:line=356:obj=unknown:subj=xmlSecXPathDataExecute:error=1:xmlsec
>>
>> library function failed:
>> func=xmlSecTransformXPathExecute:file=xpath.c:line=466:obj=xpointer:subj=xmlSecXPathDataExecute:error=1:xmlsec
>>
>> library function failed:
>> func=xmlSecTransformDefaultPushXml:file=transforms.c:line=2395:obj=xpointer:subj=xmlSecTransformExecute:error=1:xmlsec
>>
>> library function failed:
>> func=xmlSecTransformCtxXmlExecute:file=transforms.c:line=1226:obj=unknown:subj=xmlSecTransformPushXml:error=1:xmlsec
>>
>> library function failed:transform=xpointer
>> func=xmlSecTransformCtxExecute:file=transforms.c:line=1286:obj=unknown:subj=xmlSecTransformCtxXmlExecute:error=1:xmlsec
>>
>> library function failed:
>> func=xmlSecDSigReferenceCtxProcessNode:file=xmldsig.c:line=1571:obj=unknown:subj=xmlSecTransformCtxExecute:error=1:xmlsec
>>
>> library function failed:
>> func=xmlSecDSigCtxProcessSignedInfoNode:file=xmldsig.c:line=804:obj=unknown:subj=xmlSecDSigReferenceCtxProcessNode:error=1:xmlsec
>>
>> library function failed:node=Reference
>> func=xmlSecDSigCtxProcessSignatureNode:file=xmldsig.c:line=547:obj=unknown:subj=xmlSecDSigCtxProcessSignedInfoNode:error=1:xmlsec
>>
>> library function failed:
>> func=xmlSecDSigCtxSign:file=xmldsig.c:line=303:obj=unknown:subj=xmlSecDSigCtxSigantureProcessNode:error=1:xmlsec
>>
>> library function failed:
>> =========
>>
>> The document has an ID attribute declared in DTD, the value has no weird
>> characters in it yet the id() expression fails. To add insult to injury,
>> this is in the code that's been working for a long time on different
>> versions of Linux. The problem I am seeing now is on CentOS
>> (2.6.32-220.23.1.el6.centos.plus.x86_64), libxmlsec1 1.2.16, libxml2
>> 2.7.6, BUT everything has worked with this configuration (just not this
>> particular instance) before! The only difference I can think of is that
>> the XML document is now created by a different (newer) version of the
>> wrapper library for libxml2 (https://github.com/polotek/libxmljs) but
>> what could it possibly impact I don't know. Same version of the library
>> works for me just fine on a different system.
>>
>> Ideas or advice very much appreciated!
>>
>> Thanks in advance,
>> ...Max...
>>
>>
>>
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