[xmlsec] question: *X509VerifyAndExtractKey

Wed, 28 May 2003 18:35:11 -0700

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<blockquote type="cite" cite="mid3ED55A18.40208@netscape.com">
 <pre wrap="">The issue is: why do you add "untrusted certs from x509store.".
I think I know why, but wanted to hear it from you.
 </pre>
</blockquote>
First of all, lets make clear that we are talking here about
xmlSecOpenSSL* functions. 
Nobody said that other crypto&nbsp; libraries should do the same. Because
OpenSSL just 
ignores these certs. This is a workaround for a "todo" in OpenSSL
sources. Probably 
other implementations should not do it. 
 
<blockquote type="cite" cite="mid3ED55A18.40208@netscape.com">
 <pre wrap="">The spec is a bit ambiguous about whether the certs_from_&lt;X509Data&gt;
contains the public key to be used.
 </pre>
</blockquote>
It took some time and few XMLDSig mailing list searches before I
painted the full 
picture myself. My understanding is that: 
 
1) all certs included or pointed to in a single &lt;dsig:X509Data/&gt;
element should 
either contain a signature key or be a part of certificates chain that
points to 
signature key; 
2) one &lt;dsig:X509Data/&gt; element may contain multiple key
certificates or certificates 
chains but all of them (of course) contain *the same* key (for example,
you can put 
multiple certs with the same key signed with different root certs); 
3) all certs for one certificate chain MUST be placed in one 
&lt;dsig:X509Data/&gt; element. 
 
Examples (A0,A1,A2 and B0,B1,B2 are certificates chains with same key
in A0 and 
B0 certs): 
 
1. (good) All in one. 
One &lt;dsig:X509Data/&gt; element contain all 6 certs: A0, A1, A2, B0,
B1 and B2. 
 
2. (good) Two &lt;dsig:X509Data/&gt; elements. 
First &lt;dsig:X509Data/&gt; element contain A0, A1 and A2. Second 
&lt;dsig:X509Data/&gt; 
element contain B0, B1 and B2. 
 
3. (bad) Invalid mix. 
First &lt;dsig:X509Data/&gt; element contain A0 and A1. Second 
&lt;dsig:X509Data/&gt; element 
has A2, B0, B1 and B2. 
 
4. (bad) Unrelated cert. 
One &lt;dsig:X509Data/&gt; element contain all 6 certs plus one
unrelated cert: A0, A1, A2, B0, 
B1, B2 and C (where C is something not related to A's and B's chain and
do not contain 
signature key). 
 
 
 
Aleksey 
 
 
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