Luke Howard 85756bd228 krb5: make keyed checksums mandatory where possible ...

Make keyed checksums mandatory when generating and verifying checksums, with
the following exceptions:

* the checksum is being generated or verified as part of encrypting data for
  a legacy (DES) encryption type

* the KRB5_CRYPTO_FLAG_ALLOW_UNKEYED_CHECKSUM flag was set on the crypto
  context, used to allow unkeyed checksums in krb5 authenticators

By making unkeyed checksums opt-in, we eliminate a class of potential
vulnerabilities where callers could pass unkeyed checksums.

Any code that uses the mandatory checksum type for a given non-legacy
encryption type should not be affected by this change. It could potentially
break, say, a client trying to do FAST with DES keys but, that should not be
supported (because FAST KDCs also support AES).

Closes: #835

2021-09-21 18:02:25 +10:00

4.5 KiB

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