From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Thu, 14 Aug 1997 21:35:54 -0400
From: presotto@plan9.bell-labs.com presotto@plan9.bell-labs.com
Subject: [9fans] /srv modes
Topicbox-Message-UUID: 5ec732a4-eac8-11e9-9e20-41e7f4b1d025
Message-ID: <19970815013554.ZI_f3cTOUeSdd86Nr_bZG4wEancMf0seOuSxEQKzQEM@z>

It's clear that someone else had a similar idea.  Here's the
code for srvopen/create in our current plan9 (and brazil) sources:

Chan*
srvopen(Chan *c, int omode)
{
	int mode;
	Srv *sp;

	if(c->qid.path == CHDIR){
		if(omode != OREAD)
			error(Eisdir);
		c->mode = omode;
		c->flag |= COPEN;
		c->offset = 0;
		return c;
	}
	qlock(&srvlk);
	if(waserror()){
		qunlock(&srvlk);
		nexterror();
	}

	for(sp = srv; sp; sp = sp->link)
		if(sp->path == c->qid.path)
			break;

	if(sp == 0 || sp->chan == 0)
		error(Eshutdown);

	if(omode&OTRUNC)
		error(Eperm);
	if(omode!=sp->chan->mode && sp->chan->mode!=ORDWR)
		error(Eperm);

	if(strcmp(u->p->user, sp->owner) == 0)	/* User */
		mode = sp->perm;
	else if(strcmp(u->p->user, eve) == 0)	/* eve is group */
		mode = sp->perm<<3;
	else
		mode = sp->perm<<6;		/* Other */
	if((mode & 0600) != 0600)
		error(Eperm);

	close(c);
	incref(sp->chan);
	qunlock(&srvlk);
	poperror();
	return sp->chan;
}

void
srvcreate(Chan *c, char *name, int omode, ulong perm)
{
	Srv *sp;

	if(omode != OWRITE)
		error(Eperm);

	sp = malloc(sizeof(Srv));
	if(sp == 0)
		error(Enomem);

	qlock(&srvlk);
	if(waserror()){
		qunlock(&srvlk);
		nexterror();
	}
	sp->path = path++;
	sp->link = srv;
	c->qid.path = sp->path;
	srv = sp;
	qunlock(&srvlk);
	poperror();

	strncpy(sp->name, name, NAMELEN);
	strncpy(sp->owner, u->p->user, NAMELEN);
	sp->perm = perm&0777;

	c->flag |= COPEN;
	c->mode = OWRITE;
}

It saves and checks the create permissions though it does require
ORDWR on the channel and the open.

------ forwarded message follows ------

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From: ncube.com!beto
Message-Id: <199708141805.OAA11537@cse.psu.edu>
Date: Thu, 14 Aug 97 10:53:35 PDT
To: cse.psu.edu!9fans
Subject: [9fans] /srv modes
Sender: cse.psu.edu!owner-9fans
Reply-To: cse.psu.edu!9fans
Precedence: bulk

Hi,

I got a question about /srv/foo access permision.

When you create a file onto /srv to post a fd, the modes
you specify during the create are not relate to the modes
that are checked during open.
During the open the modes that are check are the modes
on the referenced channel, and it check only for OREAD/OWRITE.

This makes some sense for 9P connection to servers that
provides authentication but it's a problem if you want to
do something else.

For example, it would be nice if I could post a fd for processes
running under the same uid to share. For example I could
create the file with 600, so only processes with my
uid can read/write to it.

Will it brake something if I changed devsrv.c to check first for
permission on the file and then permission on the channel?

Most fd are posted 666 (/srv/nfsserver.chat uses 600) so
they shouldn't be affected????

Any comment would be appreciated?