[xmlsec] Can't decrypt GCM based algorithms

Wed Mar 30 00:23:03 UTC 2022

I read https://www.w3.org/TR/xmlenc-core/#sec-AES-GCM as requiring no padding.

No padding should be used during encryption

but if I read 5.2.4 AES-GCM in the context of section 5.2 Block
Encryption Algorithms then I guess the padding is required.

Great things these standards :-)

Tim

Timothy Legge
timlegge at gmail.com
timlegge at cpan.org

On Tue, Mar 29, 2022 at 9:12 PM Aleksey Sanin <aleksey at aleksey.com> wrote:
>
> Sorry forgot to add a pointer:
>
> https://www.w3.org/TR/2002/REC-xmlenc-core-20021210/Overview.html#sec-Alg-Block
>
> This is not the standard RFC 1423 padding that most of the software is
> using these days.
>
> Aleksey
>
> On 3/29/22 8:10 PM, Aleksey Sanin wrote:
> > I would check what kind of padding is used by the encryption software.
> > That's one of the most common reasons for EVP_CipherFinal failure like
> > that.
> >
> > Aleksey
> >
> > On 3/29/22 6:35 PM, Timothy Legge wrote:
> >> That likely answers that particular issue.  My module issue looks like
> >> this:
> >>
> >> xmlsec1 --decrypt --privkey-pem
> >> ~/perl-Net-SAML2/xt/testapp/sign-private.pem tmp.xml
> >> func=xmlSecOpenSSLEvpBlockCipherCtxUpdateBlock:file=ciphers.c:line=250:obj=aes256-gcm:subj=EVP_CipherFinal:error=4:crypto
> >>
> >> library function failed:openssl error: 0: NULL: NULL NULL
> >> func=xmlSecOpenSSLEvpBlockCipherGCMCtxFinal:file=ciphers.c:line=557:obj=aes256-gcm:subj=xmlSecOpenSSLEvpBlockCipherCtxUpdateBlock:error=1:xmlsec
> >>
> >> library function failed:
> >> func=xmlSecOpenSSLEvpBlockCipherExecute:file=ciphers.c:line=843:obj=aes256-gcm:subj=xmlSecOpenSSLEvpBlockCipherCtxFinal:error=1:xmlsec
> >>
> >> library function failed:
> >> func=xmlSecTransformDefaultPushBin:file=transforms.c:line=1927:obj=aes256-gcm:subj=xmlSecTransformExecute:error=1:xmlsec
> >>
> >> library function failed:final=1
> >> func=xmlSecTransformDefaultPushBin:file=transforms.c:line=1952:obj=aes256-gcm:subj=xmlSecTransformPushBin:error=1:xmlsec
> >>
> >> library function failed:final=1;outSize=74
> >> func=xmlSecTransformCtxBinaryExecute:file=transforms.c:line=941:obj=unknown:subj=xmlSecTransformPushBin:error=1:xmlsec
> >>
> >> library function failed:dataSize=102
> >> func=xmlSecEncCtxDecryptToBuffer:file=xmlenc.c:line=614:obj=unknown:subj=xmlSecTransformCtxBinaryExecute:error=1:xmlsec
> >>
> >> library function failed:
> >> func=xmlSecEncCtxDecrypt:file=xmlenc.c:line=524:obj=unknown:subj=xmlSecEncCtxDecryptToBuffer:error=1:xmlsec
> >>
> >> library function failed:
> >> Error: failed to decrypt file
> >> Error: failed to decrypt file "tmp.xml"
> >>
> >>
> >>
> >> Timothy Legge
> >> timlegge at gmail.com
> >> timlegge at cpan.org
> >>
> >> On Tue, Mar 29, 2022 at 6:57 PM Aleksey Sanin <aleksey at aleksey.com>
> >> wrote:
> >>>
> >>> Yes, basically you need to tell XML parser about ID attributes.
> >>> As I said, section 3.2 in FAQ:
> >>>
> >>> https://www.aleksey.com/xmlsec/faq.html
> >>>
> >>> Aleksey
> >>>
> >>> On 3/29/22 5:52 PM, Timothy Legge wrote:
> >>>> Hi
> >>>>
> >>>> I am missing the reference I think.  Is it related to the --id-attr?
> >>>>
> >>>> Timothy Legge
> >>>> timlegge at gmail.com
> >>>> timlegge at cpan.org
> >>>>
> >>>> On Tue, Mar 29, 2022 at 6:36 PM Aleksey Sanin <aleksey at aleksey.com>
> >>>> wrote:
> >>>>>
> >>>>> FAQ section 3.2 if I recall (or somewhere close by).
> >>>>>
> >>>>> Aleksey
> >>>>>
> >>>>> On 3/29/22 5:34 PM, Timothy Legge wrote:
> >>>>>> Hi
> >>>>>>
> >>>>>> It also seems to be an issue with a IdP SAMLResponse from okta:
> >>>>>>
> >>>>>> I have attached the xml as test xml and the base64 version as well as
> >>>>>> the private key (that private key is from perl-Net-SAML2 and is
> >>>>>> already public so it is fine to post).  My perl XML::Enc module
> >>>>>> decrypts this file without any issues.
> >>>>>>
> >>>>>> I am continuing to review.
> >>>>>>
> >>>>>> Tim
> >>>>>>
> >>>>>> xmlsec1 --decrypt --privkey-pem sign-private-rsa.pem test.xml
> >>>>>> func=xmlSecXPathDataExecute:file=xpath.c:line=246:obj=unknown:subj=xmlXPtrEval:error=5:libxml2
> >>>>>>
> >>>>>> library function
> >>>>>> failed:expr=xpointer(id('_040a0aae3380dc9275ae08c24a8ddd72')); xml
> >>>>>> error: 0: NULL
> >>>>>> func=xmlSecXPathDataListExecute:file=xpath.c:line=330:obj=unknown:subj=xmlSecXPathDataExecute:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecTransformXPathExecute:file=xpath.c:line=430:obj=xpointer:subj=xmlSecXPathDataListExecute:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecTransformDefaultPushXml:file=transforms.c:line=2108:obj=xpointer:subj=xmlSecTransformExecute:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecTransformCtxXmlExecute:file=transforms.c:line=1044:obj=xpointer:subj=xmlSecTransformPushXml:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecTransformCtxExecute:file=transforms.c:line=1092:obj=unknown:subj=xmlSecTransformCtxXmlExecute:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecKeyDataRetrievalMethodXmlRead:file=keyinfo.c:line=1108:obj=retrieval-method:subj=xmlSecTransformCtxExecute:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecKeyInfoNodeRead:file=keyinfo.c:line=121:obj=retrieval-method:subj=xmlSecKeyDataXmlRead:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:node=RetrievalMethod
> >>>>>> func=xmlSecKeysMngrGetKey:file=keys.c:line=1234:obj=unknown:subj=xmlSecKeyInfoNodeRead:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:node=KeyInfo
> >>>>>> func=xmlSecEncCtxEncDataNodeRead:file=xmlenc.c:line=779:obj=unknown:subj=unknown:error=45:key
> >>>>>>
> >>>>>> is not found:encMethod=aes256-gcm
> >>>>>> func=xmlSecEncCtxDecryptToBuffer:file=xmlenc.c:line=596:obj=unknown:subj=xmlSecEncCtxEncDataNodeRead:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> func=xmlSecEncCtxDecrypt:file=xmlenc.c:line=524:obj=unknown:subj=xmlSecEncCtxDecryptToBuffer:error=1:xmlsec
> >>>>>>
> >>>>>> library function failed:
> >>>>>> Error: failed to decrypt file
> >>>>>> Error: failed to decrypt file "test.xml"
> >>>>>>
> >>>>>> Timothy Legge
> >>>>>> timlegge at gmail.com
> >>>>>> timlegge at cpan.org
> >>>>>>
> >>>>>> On Tue, Mar 29, 2022 at 1:25 PM Timothy Legge <timlegge at gmail.com>
> >>>>>> wrote:
> >>>>>>>
> >>>>>>> perfect.  I do get errors but my laptop is home at the moment.  I
> >>>>>>> will test again tonight and let you know.
> >>>>>>>
> >>>>>>> Tim
> >>>>>>>
> >>>>>>> On Tue., Mar. 29, 2022, 12:57 p.m. Aleksey Sanin,
> >>>>>>> <aleksey at aleksey.com> wrote:
> >>>>>>>>
> >>>>>>>> Well, the gcm code for openssl is here:
> >>>>>>>>
> >>>>>>>> https://github.com/lsh123/xmlsec/blob/4b6ab2d86b71f8642f19ab3b7a0777984b6bce9a/src/openssl/ciphers.c#L80
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> so adding printfs in these functions would help.
> >>>>>>>>
> >>>>>>>> Do you get any errors?
> >>>>>>>>
> >>>>>>>> Aleksey
> >>>>>>>>
> >>>>>>>> On 3/29/22 11:51 AM, Timothy Legge wrote:
> >>>>>>>>> Hi
> >>>>>>>>>
> >>>>>>>>> I am working on adding support for aes*-gcm to perl's
> >>>>>>>>> XML::Enc.  I can:
> >>>>>>>>>
> >>>>>>>>> 1. Decrypt SAML responses encrypted with aes*-gcm using XML::Enc
> >>>>>>>>> 2. Decrypt xmlsec encrypted aes*-gcm XML using XML::Enc
> >>>>>>>>> 3. Encrypt XML using aes*-gcm with XML::Sec
> >>>>>>>>> 4. Decrypt XML that was encrypted with XML::Sec using ases*-gcm
> >>>>>>>>>
> >>>>>>>>> However, I cannot use xmlsec to decrypt XML::Sec encrypted XML
> >>>>>>>>> that
> >>>>>>>>> uses aes*-gcm.
> >>>>>>>>>
> >>>>>>>>> I can't think of any issues that would allow me to encrypt and
> >>>>>>>>> decrypt
> >>>>>>>>> XML successfully with XML::Enc but not allow xmlsec to decrypt
> >>>>>>>>> those
> >>>>>>>>> files.
> >>>>>>>>>
> >>>>>>>>> I was wondering if there is a debug flag for XML sec that would
> >>>>>>>>> allow
> >>>>>>>>> me to output the following:
> >>>>>>>>>
> >>>>>>>>> 1. base64 of the CipherValue it reads from the XML file
> >>>>>>>>> 2. base 64 of IV
> >>>>>>>>> 3 base64 of encrypted data
> >>>>>>>>> 4 base 64 of the tag
> >>>>>>>>> 5 base 64 of the key
> >>>>>>>>>
> >>>>>>>>> I don't mind adding some print debugging and recompiling if you
> >>>>>>>>> can
> >>>>>>>>> point me to a starting place.  It has been a while since I
> >>>>>>>>> wrote much
> >>>>>>>>> C but I have no issues.  Finding the correct spot though...
> >>>>>>>>>
> >>>>>>>>> Tim
> >>>>>>>>>
> >>>>>>>>> Timothy Legge
> >>>>>>>>> timlegge at gmail.com
> >>>>>>>>> timlegge at cpan.org
> >>>>>>>>> _______________________________________________
> >>>>>>>>> xmlsec mailing list
> >>>>>>>>> xmlsec at aleksey.com
> >>>>>>>>> http://www.aleksey.com/mailman/listinfo/xmlsec
> >>>> _______________________________________________
> >>>> xmlsec mailing list
> >>>> xmlsec at aleksey.com
> >>>> http://www.aleksey.com/mailman/listinfo/xmlsec
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