Checking the signature of a p7m document

Consider the case where the signed document is a pdf (document.pdf.p7m).

To verify the signature and extract the content file, we use the openssl command with the smime parameter for signature verification (-verify)

openssl smime -in document.pdf.p7m -inform DER -verify -CAfile CA.pem -out document.pdf

where CA.pem contains the CA certificate (Certificate Authority) that issued the certificate in the p7m.

For more information, see the articol