Re: [PATCH 00/18] Migrate rpcsec_gss_krb5 to the crypto/krb5 library

[Chuck Lever]

On Wed, Apr 29, 2026, at 2:39 AM, Jeff Layton wrote:
> On Mon, 2026-04-27 at 09:50 -0400, Chuck Lever wrote:
>> The rpcsec_gss_krb5 module carries its own Kerberos 5 crypto imple-
>> mentation: key derivation, CBC-CTS encryption, HMAC checksumming,
>> and the encrypt-then-MAC construction from RFC 8009. Keeping
>> cryptographic code inside an RPC module means it receives review
>> only from the SUNRPC maintainers, who lack deep crypto expertise.
>> Vulnerabilities and algorithmic errors can persist unnoticed.
>> 
>> Replacing the private SunRPC Kerberos implementation eliminates
>> this duplicated audit surface. A single implementation of Kerberos
>> 5 key derivation and authenticated encryption is easier to verify
>> than two independent copies. New encryption types and hardware
>> offload added to crypto/krb5 will automatically become available
>> to SunRPC Kerberos consumers.
>> 
>> The crypto/krb5 library handles enctype differences internally, so
>> a single encrypt function and a single decrypt function serve all
>> enctypes, eliminating the per-enctype dispatch table that previously
>> existed in struct gss_krb5_enctype.
>> 
>> RFC 4121 Section 4.2.4 requires MIC checksums to cover the message
>> body followed by the GSS token header. The crypto/krb5 get_mic/
>> verify_mic API hashes optional metadata before the scatterlist
>> data, which is the wrong order for the GSS header. The header is
>> therefore placed at the end of the scatterlist rather than passed
>> as the metadata parameter, and a dedicated gss_krb5_mic_build_sg()
>> helper constructs this three-section layout (checksum area, message
>> body, token header) with proper sg_mark_end() termination.
>> 
>> This implementation was available during the Spring 2026 NFS bake-
>> a-thon, and received testing there.

>
> Love that diffstat. Nice work! 
>
> One comment in general: Do you need to add Assisted-by: tags to any of
> this? You can add this to the set:
>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>

Thanks, applied to nfsd-testing. An Acked-by: from one of the NFS
client maintainers would be great too.


-- 
Chuck Lever