[xmlsec] [Fwd: HMACOutputLength and xmlsec]

[Jonathan Wenocur]

  Forgot to copy the list.  Hope this helps, Aleksy.  (Note I'm not on 
the xmlsec mailing list.)

-- Jonathan

-------- Original Message --------
Subject: HMACOutputLength and xmlsec
Date: Fri, 24 Jan 2003 13:15:08 -0500
From: Jonathan Wenocur <jwenocur at datapower.com>
To: Rich Salz <rsalz at datapower.com>, Jonathan Wenocur 
<jwenocur at datapower.com>



The file simple-91.xml.signed is a version of simple-91.xml which we 
signed with secret1.  xmlsec doesn't verify the sig because 
HMACOutputLength is 91, which is not evenly divisible by 8 (see 
xmlsec/src/hmac.c:xmlSecMacHmacReadNode() where res=atoi((char 
*)content) / 8).

I tried feeding the same input file into xmlsec to see how it signs it, 
the file is simple-91.xml.templ is the file I fed into xmlsec, and the 
signed output is simple-91.xml.templ.signed

You'll note that the difference between the two files is only in the 
last couple of characters of the base64 encoded SignatureValue.  The 
base64 decoded value we output is:

0000000: d8 77 9e d9 ca 91 3a 6b 61 08 82 20              .w....:ka.. 

The base64 decoded value from xmlsec is:

0000000: d8 77 9e d9 ca 91 3a 6b 61 08 82

Which is the same signature but truncated down to 88 bits instead of 91 bits (assuming of course that the last few bits we add are correct).

-- Jonathan







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<?xml version="1.0" encoding="UTF-8"?>
<SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/07/secext"><SOAP:Header><wsse:Security><Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
  <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
  <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1">
    <HMACOutputLength>91</HMACOutputLength>
  </SignatureMethod>
  <Reference URI="#Body">
    <Transforms>
      <Transform Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
    </Transforms>
    <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
    <DigestValue>KlK8TF9wnLYvXz008MJV4umoHhE=</DigestValue>
  </Reference>
</SignedInfo>
    <SignatureValue>gmtoF50KWNUTGQCg</SignatureValue><KeyInfo><KeyName>name:KEY</KeyName></KeyInfo></Signature></wsse:Security></SOAP:Header><SOAP:Body id="Body">
<echo xmlns="http://www.example.org">
this
is
a
test
of
echoing
simple-91
</echo>
</SOAP:Body></SOAP:Envelope>
-------------- next part --------------
secret
-------------- next part --------------
<?xml version="1.0" encoding="UTF-8"?>
<SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/07/secext"><SOAP:Header><wsse:Security><Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
  <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
  <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1">
    <HMACOutputLength>91</HMACOutputLength>
  </SignatureMethod>
  <Reference URI="#Body">
    <Transforms>
      <Transform Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
    </Transforms>
    <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
    <DigestValue></DigestValue>
  </Reference>
</SignedInfo>
    <SignatureValue></SignatureValue><KeyInfo><KeyName>name:KEY</KeyName></KeyInfo></Signature></wsse:Security></SOAP:Header><SOAP:Body id="Body">
<echo xmlns="http://www.example.org">
this
is
a
test
of
echoing
simple-91
</echo>
</SOAP:Body></SOAP:Envelope>
-------------- next part --------------
<?xml version="1.0" encoding="UTF-8"?>
<SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/07/secext"><SOAP:Header><wsse:Security><Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
  <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
  <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-sha1">
    <HMACOutputLength>91</HMACOutputLength>
  </SignatureMethod>
  <Reference URI="#Body">
    <Transforms>
      <Transform Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
    </Transforms>
    <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
    <DigestValue>KlK8TF9wnLYvXz008MJV4umoHhE=</DigestValue>
  </Reference>
</SignedInfo>
    <SignatureValue>gmtoF50KWNUTGQA=</SignatureValue><KeyInfo><KeyName>name:KEY</KeyName></KeyInfo></Signature></wsse:Security></SOAP:Header><SOAP:Body id="Body">
<echo xmlns="http://www.example.org">
this
is
a
test
of
echoing
simple-91
</echo>
</SOAP:Body></SOAP:Envelope>