[PATCH] smb3.1.1: allow dumping GCM256 keys to improve debugging of encrypted shares

[Aurélien Aptel]

Steve French <smfrench at gmail.com> writes:
>> > Or as an alternative, dump an array of ALL user sessions with
>> > information about which user and which part of a multi-channel
>> > connection that the keys belong to.
>> > And let userspace sort out "which keys do I need for my wireshark session".

All channels for 1 session share the same keys (except signing).

I like Shyam's idea of having extra uid arg but it's more tricky
to get (have to walk the tlink RB tree and find matching uid) compared
to an extra session id arg.

> +static int cifs_dump_full_key(struct cifs_tcon *tcon, unsigned long arg)
> +{
> +	struct smb3_full_key_debug_info pfull_key_inf;
> +	__u64 suid;
> +	struct list_head *tmp;
> +	struct cifs_ses *ses;
> +	bool found = false;
> +
> +	if (!smb3_encryption_required(tcon))
> +		return -EOPNOTSUPP;
> +
> +	ses = tcon->ses; /* default to user id for current user */
> +	if (get_user(suid, (__u32 __user *)arg))
> +		suid = 0;
> +	if (suid) {
> +		/* search to see if there is a session with a matching SMB UID */
> +		spin_lock(&cifs_tcp_ses_lock);
> +		list_for_each(tmp, &tcon->ses->server->smb_ses_list) {
> +			ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
> +			if (ses->Suid == suid) {
> +				found = true;
> +				break;
> +			}
> +		}
> +		spin_unlock(&cifs_tcp_ses_lock);

Btw, if we go with this we need to bump the session refcount if access
it outside of the locked section (and decrement before returning).

Cheers,
-- 
Aurélien Aptel / SUSE Labs Samba Team
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