[PATCH net-next] crypto/krb5: Fix change to use SG miter to use offset

[Herbert Xu]

On Mon, Apr 28, 2025 at 11:22:06AM +0100, David Howells wrote:
> [Note: Nothing in linus/master uses the krb5lib, though the bug is there,
>  but it is used by AF_RXRPC's RxGK implementation in net-next, so can it go
>  through the net-next tree rather than directly to Linus or through
>  crypto?]

Sure I'm happy for this to go through net-next.

> The recent patch to make the rfc3961 simplified code use sg_miter rather
> than manually walking the scatterlist to hash the contents of a buffer
> described by that scatterlist failed to take the starting offset into
> account.
> 
> This is indicated by the selftests reporting:
> 
>     krb5: Running aes128-cts-hmac-sha256-128 mic
>     krb5: !!! TESTFAIL crypto/krb5/selftest.c:446
>     krb5: MIC mismatch
> 
> Fix this by calling sg_miter_skip() before doing the loop to advance by the
> offset.
> 
> This only affects packet signing modes and not full encryption in RxGK
> because, for full encryption, the message digest is handled inside the
> authenc and krb5enc drivers.
> 
> Fixes: da6f9bf40ac2 ("crypto: krb5 - Use SG miter instead of doing it by hand")
> Reported-by: Marc Dionne <marc.dionne at auristor.com>
> Signed-off-by: David Howells <dhowells at redhat.com>
> cc: Herbert Xu <herbert at gondor.apana.org.au>
> cc: "David S. Miller" <davem at davemloft.net>
> cc: Chuck Lever <chuck.lever at oracle.com>
> cc: Eric Dumazet <edumazet at google.com>
> cc: Jakub Kicinski <kuba at kernel.org>
> cc: Paolo Abeni <pabeni at redhat.com>
> cc: Simon Horman <horms at kernel.org>
> cc: linux-afs at lists.infradead.org
> cc: linux-nfs at vger.kernel.org
> cc: linux-crypto at vger.kernel.org
> cc: netdev at vger.kernel.org
> ---
>  crypto/krb5/rfc3961_simplified.c |    1 +
>  1 file changed, 1 insertion(+)

Acked-by: Herbert Xu <herbert at gondor.apana.org.au>

Thanks,
-- 
Email: Herbert Xu <herbert at gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt