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?

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.