xmlsec fails to verify signature

Question

I am trying to verify XML (attached on the bottom of the question) signature with xmlsec1 utility. However, when executing a command

xmlsec1 --verify test.xml

I am getting following stack trace:

func=xmlSecXPathDataExecute:file=xpath.c:line=273:obj=unknown:subj=xmlXPtrEval:error=5:libxml2 library function failed:expr=xpointer(id('uuid-73c06e86-88d2-4204-91f4-3d484bc782cc')) func=xmlSecXPathDataListExecute:file=xpath.c:line=373:obj=unknown:subj=xmlSecXPathDataExecute:error=1:xmlsec library function failed: func=xmlSecTransformXPathExecute:file=xpath.c:line=483:obj=xpointer:subj=xmlSecXPathDataExecute:error=1:xmlsec library function failed: func=xmlSecTransformDefaultPushXml:file=transforms.c:line=2411:obj=xpointer:subj=xmlSecTransformExecute:error=1:xmlsec library function failed: func=xmlSecTransformCtxXmlExecute:file=transforms.c:line=1242:obj=unknown:subj=xmlSecTransformPushXml:error=1:xmlsec library function failed:transform=xpointer func=xmlSecTransformCtxExecute:file=transforms.c:line=1302:obj=unknown:subj=xmlSecTransformCtxXmlExecute:error=1:xmlsec library function failed: func=xmlSecDSigReferenceCtxProcessNode:file=xmldsig.c:line=1589:obj=unknown:subj=xmlSecTransformCtxExecute:error=1:xmlsec library function failed: func=xmlSecDSigCtxProcessSignedInfoNode:file=xmldsig.c:line=822:obj=unknown:subj=xmlSecDSigReferenceCtxProcessNode:error=1:xmlsec library function failed:node=Reference func=xmlSecDSigCtxProcessSignatureNode:file=xmldsig.c:line=563:obj=unknown:subj=xmlSecDSigCtxProcessSignedInfoNode:error=1:xmlsec library function failed: func=xmlSecDSigCtxVerify:file=xmldsig.c:line=382:obj=unknown:subj=xmlSecDSigCtxSignatureProcessNode:error=1:xmlsec library function failed: Error: signature failed ERROR SignedInfo References (ok/all): 0/1 Manifests References (ok/all): 0/0 Error: failed to verify file "test.xml" ```

Based on stack trace, I presume something is wrong with ID. After some digging, I found that executing

xmlsec1 --verify --id-attr:ID 
"urn:oasis:names:tc:SAML:2.0:protocol:Response" test.xml

produces following stack trace

func=xmlSecOpenSSLEvpDigestVerify:file=digests.c:line=249:obj=sha1:subj=unknown:error=12:invalid data:data and digest do not match FAIL SignedInfo References (ok/all): 0/1 Manifests References (ok/all): 0/0 Error: failed to verify file "test.xml"

Here's trimmed content of test.xml file:

<saml2p:Response xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol" Destination="http://localhost/login" ID="uuid-73c06e86-88d2-4204-91f4-3d484bc782cc" InResponseTo="_bbaf45ef713be7a8c8701e41118ec2278cbf32828f" IssueInstant="2016-02-29T14:16:31.142Z" Version="2.0">
    <saml2:Issuer xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">idp-name</saml2:Issuer>
    <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
        <ds:SignedInfo>
            <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
            <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
            <ds:Reference URI="#uuid-73c06e86-88d2-4204-91f4-3d484bc782cc">
                <ds:Transforms>
                    <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
                    <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
                </ds:Transforms>
                <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
                <ds:DigestValue>H9ffPJ6/jq25p13BcziR0hNLkGg=</ds:DigestValue>
            </ds:Reference>
        </ds:SignedInfo>
        <ds:SignatureValue>FegjeG..pJEQ==</ds:SignatureValue>
        <ds:KeyInfo>
            <ds:X509Data>
                <ds:X509Certificate>MIIFIj..mV7A==</ds:X509Certificate>
            </ds:X509Data>
            <ds:X509Data>
                <ds:X509Certificate>MIIFDj..5uLcw=</ds:X509Certificate>
            </ds:X509Data>
            <ds:X509Data>
                <ds:X509Certificate>MIIE/z..3IDhA=</ds:X509Certificate>
            </ds:X509Data>
            <ds:X509Data>
                <ds:X509Certificate>MIIEkT..h5/WrQ8</ds:X509Certificate>
            </ds:X509Data>
        </ds:KeyInfo>
    </ds:Signature>
    <saml2:Assertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" ID="uuid-201bfc86-e7d7-4dca-bdb5-2263b2d27c22" IssueInstant="2016-02-29T14:16:01.175Z" Version="2.0">
        <saml2:Issuer>idp-name</saml2:Issuer>
        <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
            <ds:SignedInfo>
                <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
                <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
                <ds:Reference URI="#uuid-201bfc86-e7d7-4dca-bdb5-2263b2d27c22">
                    <ds:Transforms>
                        <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
                        <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
                    </ds:Transforms>
                    <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
                    <ds:DigestValue>EJzD3pVZwkvFkh8IX0xyF7tmP2k=</ds:DigestValue>
                </ds:Reference>
            </ds:SignedInfo>
            <ds:SignatureValue>b3ONeh..zOEw==</ds:SignatureValue>
            <ds:KeyInfo>
                <ds:X509Data>
                    <ds:X509Certificate>MIIFIj..mV7A==</ds:X509Certificate>
                </ds:X509Data>
                <ds:X509Data>
                    <ds:X509Certificate>MIIFDj..5uLcw=</ds:X509Certificate>
                </ds:X509Data>
                <ds:X509Data>
                    <ds:X509Certificate>MIIE/z..3IDhA=</ds:X509Certificate>
                </ds:X509Data>
                <ds:X509Data>
                    <ds:X509Certificate>MIIEkT..5/WrQ8</ds:X509Certificate>
                </ds:X509Data>
            </ds:KeyInfo>
        </ds:Signature>
    </saml2:Assertion>
</saml2p:Response>

Can you please explain me what am I doing wrong here? How to validate signed XML file with xmlsec?

Mandal

Answer 1

I have found a correct way to validate this, so here's how:

First, ID attribute must be specified:

xmlsec1 --verify --id-attr:ID "urn:oasis:names:tc:SAML:2.0:protocol:Response" test.xml

Executing this command against my XML file resulted in error invalid data:data and digest do not match.

I've been invoking this command against output returned by SAML Tracer (Firefox addon) which formats XML - this changes the signature so xmlsec1 prints error.

Invoking xmlsec1 against original (decrypted) content works fine.

Mandal

Was struggling with the same problem and this saved my day. It's really not obvious that xmlsec requires non formatted base64 decoded input to do it's work. – Debidebilitate

For the record: formatted XML is canonically different from unformatted XML, assuming that formatting inserts whitespace between tags -- xmlsec1 is working to spec, however surprising it is – Tonsil