No, it's secure. Login process using certificate is following:
1. Server send random challenge to client
2. Client sign server's challenge with his certificate's private key and send signed challenge along with public part of certificate to server
3. Server validates certificate using CA certificate
4. If certificate is valid, server validates challenge signature using certificate's public key
5. If signature is valid, server compares certificate subject with mapping data from user record
6. If mapping data match with certificate subject, access is granted
So, to login successfully, user must posses valid certificate with private key. Having just public part of certificate is not enough. Authentication by certificate also allows smart card login - you just need to store certificate used for login on smart card instead of local certificate store.
Best regards,
Victor
1. Server send random challenge to client
2. Client sign server's challenge with his certificate's private key and send signed challenge along with public part of certificate to server
3. Server validates certificate using CA certificate
4. If certificate is valid, server validates challenge signature using certificate's public key
5. If signature is valid, server compares certificate subject with mapping data from user record
6. If mapping data match with certificate subject, access is granted
So, to login successfully, user must posses valid certificate with private key. Having just public part of certificate is not enough. Authentication by certificate also allows smart card login - you just need to store certificate used for login on smart card instead of local certificate store.
Best regards,
Victor
Now I have added this as feature request to bugtracker (issue 309), and hopefully it will be included in 1.0.7 release.