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I've signed and issued some client certificates with my CA. I can now revoke them like so:

openssl ca -name ${CA_NAME} -revoke ${USERS_DIR}/${USERNAME}.crt -keyfile $SSL_PRIVATE_DIR/ca.key -cert $SSL_CERTS_DIR/ca.crt

(from here)

However this requires access to the *.pems in the new_certs_dir folder (e.g. 01.pem, 02.pem). I can use these but it feels like the only information I need to revoke a client cert is its serial number. However the man page for the revoke flag says it has to be the crt/pem file:

-revoke filename
       a filename containing a certificate to revoke.

I've also noticed I can manually edit the database file, changing the V (valid, presumably) to an R (revoked, presumably) and providing a timestamp for the second timestamp column, like so:

V       180408071318Z           01      unknown /C=AU/ST=NSW/O=Blah/OU=Blah/CN=CA
V       180408071319Z           02      unknown /C=AU/ST=NSW/O=Blah/OU=Blah/CN=CA

to

V       180408071318Z           01      unknown /C=AU/ST=NSW/O=Blah/OU=Blah/CN=CA
R       180408071319Z    180408081319Z       02      unknown /C=AU/ST=NSW/O=Blah/OU=Blah/CN=CA

If I then generate the crl after editing,

openssl ca -name ${CA_NAME} -gencrl -keyfile $SSL_PRIVATE_DIR/ca.key -cert $SSL_CERTS_DIR/ca.crt -out $SSL_PRIVATE_DIR/ca.crl -crldays 1095

the certificate corresponding to that serial is no longer valid. So it seems like all I needed was the serial, despite openssl not providing that option.

So my question is, is there a kosher way to revoke a certificate using only it's serial number? Or are there important reasons why this isn't done? Will I encounter problems if I manually edit the database file like above?

2

In X509 the fields making a certificate unique is the combination of issuer and serial number. Only the serial number is not guaranteed to be unique since two CAs may use the same serial. This is the reason both are typically needed for revocation. In practice, if you only have one CA, the serial will be enough of course. But it's not generic. There should be no problem manually editing the database, as this will be the same thing as the command will do

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