On Fri, Apr 2, 2021 at 4:19 PM Sam Morris <[email protected]> wrote:

> Looking into responder_common.c, the function client_recv logs "Invalid
> data from client, closing connection" if sss_packet_recv returned EINVAL.
>
> Looking into sss_packet_recv, EINVAL is returned if the packet is too
> large.
>
> Decoding the packet, the first four bytes are the packet length which is
> 1905; the second four are the command type which is 0xfb or
> SSS_GSSAPI_SEC_CTX. After the eight status/reserved bytes are the first
> 1520 bytes of the packet body. The rest of the packet body is never read
> because after the first recvfrom call (into a buffer of 1536 bytes), the
> connection is closed.
>
> I can see the definition of SSS_PACKET_MAX_RECV_SIZE is 1024. And I can
> see some code in sss_packet_recv that handles two types of packet known to
> be larger (SSS_NSS_GETNAMEBYCERT and SSS_NSS_GETLISTBYCERT, which are
> allowed to be up to SSS_CERT_PACKET_MAX_RECV_SIZE bytes or 10240 bytes
> long).
>

Please, open a ticket.

CC @Pavel Brezina <[email protected]>


>
> So maybe the SSS_GSSAPI_SEC_CTX command needs similar handling of longer
> packets so that it can deal with large kerberos tickets (which Windows
> users will have if they are in lots of groups; a quick Google suggests the
> PAC may grow up to 48 KiB as of Windows Server 2012).
>
> --
> Sam Morris <https://robots.org.uk/>
> PGP: rsa4096/CAAA AA1A CA69 A83A 892B 1855 D20B 4202 5CDA 27B9
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