Restrict Weak Signature Algorithms (7.6.4)

FortiWeb 7.6.4 introduces a CLI-only setting that allows administrators to reject TLS handshakes using weak signature algorithms, specifically SHA-1 and SHA-224. These algorithms are deprecated and pose known risks, including collision and downgrade attacks.

The option is configured in the server policy settings:

config server-policy setting
    set restrict-weak-sign-algo {enable | disable}
end

When enabled, FortiWeb blocks the use of SHA-1 and SHA-224 in certificate-based digital signatures negotiated during TLS handshakes. This setting is intended for use in non-FIPS environments only. In FIPS-CC mode, these algorithms are already prohibited and this option has no additional effect.

This setting is disabled by default and must be enabled explicitly. Note that changing its value will restart the proxy daemon (proxyd), as it affects TLS signature compatibility, similar to changes made using tls12-compatible-sigalg.

By enabling this setting, administrators can harden FortiWeb’s TLS configuration to enforce stronger cryptographic standards even outside of FIPS-CC deployments.