S/MIME find the signer email

[Aumont - Comite Reseaux des Universites]

Hi

I'am using openssl 0.95 for a perl product that must verify S/MIME
messages. Here are some question :

First i check the signature, tahat's easy, but I need also to check that
the message sender and message signer are the same. So I need to extract
fromthe message signature the signer email. That's not so easy because :
if the CA is not a root CA, the output of openssl pckcs7 contain a chain
with both the signer certificate DN and the CA certificate DN. Is there
a way to extract just the signer subject ?

Here is an exemple of how i use openssl in this step and the its output.


$ /usr/local/ssl/bin/openssl smime -nochain -pk7out -in /tmp/msg |  \
  /usr/local/ssl/bin/openssl pkcs7 -print_certs -noout

subject=/CN=Thawte Freemail [EMAIL PROTECTED]
issuer= /C=ZA/ST=Western Cape/L=Durbanville/O=Thawte Consulting/OU=Thawte PF R....

subject=/C=ZA/ST=Western Cape/L=Durbanville/O=Thawte Consulting/OU=Thawte PF R....
issuer= /C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting/OU=Certification ....


Thanks for your help.
-----------------------------------------------------------------------

Serge Aumont      CRU  campus Beaulieu             Tel : 02 99 84 71 47
                  35042 Rennes Cedex               fax : 02 99 84 71 11


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