[xmlsec] Verify invalid certificate chain
Roman Khlystik
dont.avt at gmail.com
Fri Aug 17 08:18:32 PDT 2012
Thanks, Aleksey.
It's exactly what I wanted.
2012/8/17 Aleksey Sanin <aleksey at aleksey.com>
> That makes sense. If you have KeyValue then xmlsec happily pick it up.
> You can limit the key data used by xmlsec for looking up the key.
> With xmlsec command line tool, try "--enabled-key-data" option
> (use --list-key-data to see the list).
>
> Aleksey
>
> On 8/17/12 5:38 AM, Roman Khlystik wrote:
> > Thanks, Aleksey.
> >
> > Really, I had RSA key in signature file.
> >
> > I made some investigation, I may be wrong, but I don't understand the
> > security guarantee of xml signature.
> > I'll try to explain my view on it, please indicate where I'm wrong.
> >
> > As I've understood during signature verification xmlsec might choose key
> > for verification from KeyValue field or from certificate in X509Data
> > field. There isn't any check that public key from KeyValue is the same
> > as public key from certificate.
> > Key selection algorithm is the next:
> > - Xmlsec is trying to build certificate chain from certificate in the
> > file up to a trusted cert.
> > - if it successed, key from certificate is used
> > - if it failed, xmlsec is looking for the KeyValue field.
> > - if KeyValue field is found, xmlsec uses it for verification.
> > - if KeyValue isn't found xmlsec reports an error.
> >
> > So, lets assume that I'm a bad guy and I want to substitute a signed xml
> > file.
> > All I have to do is just sign a file only with KeyValue field and
> > without any X509Data field.
> > Thus, user of signed document can't be sure that this document was sent
> > by expected sender.
> >
> > I think that there is some misunderstanding in application of xml
> > signature or I've just missed something.
> > Maybe it's possible to force xmlsec perform verification using key only
> > from X509 field? Or maybe I just may ask xmlsec to ignore key from
> > KeyValue field?
> >
> > Thanks.
> >
> > 2012/8/15 Aleksey Sanin <aleksey at aleksey.com <mailto:aleksey at aleksey.com
> >>
> >
> > That shouldn't be the case. The only possibility is that there
> > is a key in the signature file (not in certificate).
> >
> > Run xmlsec with debug output to find out where it finds key
> >
> > Aleksey
> >
> > On 8/15/12 1:21 AM, Roman Khlystik wrote:
> > > Thanks for your answer, Aleksey.
> > >
> > > I think I've understood behaviour of xmlsec in this situation.
> > > And according to this logic I assume (and actually I checked it)
> that
> > > when there isn't any
> > > valid certificate chain result code of signature verification is
> still
> > > succeeded. Why?
> > >
> > > Here is example using command-line tool.
> > > ca.crt isn't related to the certificate
> > > in license-signed-ca1-server1.xml. So, there isn't any valid
> > certificate
> > > chain. Why verification status is OK?
> > >
> > > #xmlsec1 --verify --trusted-pem cas/ca2/ca/certs/ca.crt
> > > license-signed-ca1-server1.xml
> > >
> > >
> > >
> > >
> >
> func=xmlSecOpenSSLX509StoreVerify:file=x509vfy.c:line=360:obj=x509-store:subj=X509_verify_cert:error=4:crypto
> > > library function failed:subj=/C=UA/ST=Kyiv
> > > region/L=Kyiv/O=test/OU=Ukraine
> > > Department/CN=server1/emailAddress=support at test.com
> > <mailto:support at test.com>
> > > <mailto:support at test.com
> > <mailto:support at test.com>>;err=20;msg=unable to get local issuer
> > > certificate
> > >
> >
> func=xmlSecOpenSSLX509StoreVerify:file=x509vfy.c:line=408:obj=x509-store:subj=unknown:error=71:certificate
> > > verification failed:err=20;msg=unable to get local issuer
> > certificate
> > > OK
> > > SignedInfo References (ok/all): 1/1
> > > Manifests References (ok/all): 0/0
> > >
> > >
> > >
> > > So, I have another question: Is it possibe to detect with xmlsec
> that
> > > there is no one valid certificate chain up to the one of the
> trusted
> > > certificates? I want to reject signed xml file if there isn't any
> > valid
> > > vertificate chain.
> > >
> > > Thanks.
> > >
> > > 2012/8/14 Aleksey Sanin <aleksey at aleksey.com
> > <mailto:aleksey at aleksey.com> <mailto:aleksey at aleksey.com
> > <mailto:aleksey at aleksey.com>>>
> > >
> > > Roman,
> > >
> > > During the verification, xmlsec tries to verify the signature
> > using
> > > all possible certificate chains. It is enough to have one of
> them
> > > succeed. The errors you see are from ones that failed. Safe to
> > ignore
> > > as long, just check the result code.
> > >
> > > Aleksey
> > >
> > > On 8/14/12 8:38 AM, Roman Khlystik wrote:
> > > > Hi Aleksey!
> > > >
> > > > I'm trying to develop simple license system using xmlsec
> > library.
> > > > My idea was to build simple private PKI with one CA key pair
> and
> > > > separate key-pair for each customer.
> > > > Then I planned to sign xml license file with client
> certificate
> > > for each
> > > > client.
> > > >
> > > > I decided to embbed CA certificate in our app and verify
> > certificate
> > > > chain from xml file up to CA certificate.
> > > > But I have a problem with xmlsec library. I can't find how
> > to verify
> > > > full certificate chain with it.
> > > > I used example from here
> > > >
> > http://www.aleksey.com/xmlsec/api/xmlsec-verify-with-x509.html·
> > <
> http://www.aleksey.com/xmlsec/api/xmlsec-verify-with-x509.html%C2%B7>
> > >
> > <
> http://www.aleksey.com/xmlsec/api/xmlsec-verify-with-x509.html%C2%B7>
> > > >
> > <
> http://www.aleksey.com/xmlsec/api/xmlsec-verify-with-x509.html%C2%B7>
> > > > and I have a problem when certificate chain is invalid.
> > > > I got error to console:
> > > >
> > > >
> > >
> >
> func=xmlSecOpenSSLX509StoreVerify:file=x509vfy.c:line=360:obj=x509-store:subj=X509_verify_cert:error=4:crypto
> > > > library function failed:subj=/C=UA/ST=Kyiv
> > > > region/L=Kyiv/O=test/OU=test/CN=server1/emailAddress=s
> > > >
> > >
> >
> func=xmlSecOpenSSLX509StoreVerify:file=x509vfy.c:line=408:obj=x509-store:subj=unknown:error=71:certificate
> > > > verification failed:err=20;msg=unable to get local issuer
> > certificate
> > > > OK
> > > > SignedInfo References (ok/all): 1/1·
> > > > Manifests References (ok/all): 0/0·
> > > >
> > > > but verification result dsigCtx->status has
> > > xmlSecDSigStatusSucceeded value.
> > > >
> > > > Can you tell me how can I verify that certificate chain is
> > invalid
> > > with
> > > > xmlsec api?
> > > >
> > > >
> > > > _______________________________________________
> > > > xmlsec mailing list
> > > > xmlsec at aleksey.com <mailto:xmlsec at aleksey.com>
> > <mailto:xmlsec at aleksey.com <mailto:xmlsec at aleksey.com>>
> > > > http://www.aleksey.com/mailman/listinfo/xmlsec
> > > >
> > >
> > >
> >
> >
>
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