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o There are two methods to get a process credentials over the unix

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sockets:

1) A sender sends SCM_CREDS message to a reciever, struct cmsgcred;
2) A reciever sets LOCAL_CREDS socket option and gets sender
credentials in control message, struct sockcred.

Both methods use the same control message type SCM_CREDS with the
same control message level SOL_SOCKET, so they are indistinguishable
for the receiver.  A difference in struct cmsgcred and struct sockcred
layouts may lead to unwanted effects.

Now for sockets with LOCAL_CREDS option remove all previous linked
SCM_CREDS control messages and then add a control message with
struct sockcred so the process specifically asked for the peer
credentials by LOCAL_CREDS option always gets struct sockcred.

PR:		kern/90800
Submitted by:	Andrey Simonenko
Regres. tests:	tools/regression/sockets/unix_cmsg/
MFC after:	1 month
This commit is contained in:
Maxim Konovalov 2006-06-13 14:33:35 +00:00
parent c3a252361a
commit 70df31f4de
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=159575
1 changed files with 24 additions and 10 deletions
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34
sys/kern/uipc_usrreq.c
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@ -1498,8 +1498,9 @@ unp_internalize(struct mbuf **controlp, struct thread *td)
struct mbuf *
unp_addsockcred(struct thread *td, struct mbuf *control)
{
struct mbuf *m, *n;
struct mbuf *m, *n, *n_prev;
struct sockcred *sc;
const struct cmsghdr *cm;
int ngroups;
int i;
@ -1508,7 +1509,6 @@ unp_addsockcred(struct thread *td, struct mbuf *control)
m = sbcreatecontrol(NULL, SOCKCREDSIZE(ngroups), SCM_CREDS, SOL_SOCKET);
if (m == NULL)
return (control);
m->m_next = NULL;
sc = (struct sockcred *) CMSG_DATA(mtod(m, struct cmsghdr *));
sc->sc_uid = td->td_ucred->cr_ruid;
@ -1520,16 +1520,30 @@ unp_addsockcred(struct thread *td, struct mbuf *control)
sc->sc_groups[i] = td->td_ucred->cr_groups[i];
/*
* If a control message already exists, append us to the end.
* Unlink SCM_CREDS control messages (struct cmsgcred), since
* just created SCM_CREDS control message (struct sockcred) has
* another format.
*/
if (control != NULL) {
for (n = control; n->m_next != NULL; n = n->m_next)
;
n->m_next = m;
} else
control = m;
if (control != NULL)
for (n = control, n_prev = NULL; n != NULL;) {
cm = mtod(n, struct cmsghdr *);
if (cm->cmsg_level == SOL_SOCKET &&
cm->cmsg_type == SCM_CREDS) {
if (n_prev == NULL)
control = n->m_next;
else
n_prev->m_next = n->m_next;
n = m_free(n);
} else {
n_prev = n;
n = n->m_next;
}
}
return (control);
/* Prepend it to the head. */
m->m_next = control;
return (m);
}
/*