Implement unix(4) socket options LOCAL_CREDS and LOCAL_CONNWAIT.

- Add unp_addsockcred() (for LOCAL_CREDS).
- Add an argument to unp_connect2() to differentiate between
  PRU_CONNECT and PRU_CONNECT2. (for LOCAL_CONNWAIT)

Obtained from:	 NetBSD (with some changes)

share/man/man4/unix.4

@@ -194,6 +194,56 @@ system call (e.g.,
 or
 .Xr listen 2 )
 under different effective credentials.
+.Pp
+
+.Tn UNIX
+domain sockets support a number of socket options which can be set with
+.Xr setsockopt 2
+and tested with
+.Xr getsockopt 2 :
+.Bl -tag -width ".Dv LOCAL_CONNWAIT"
+.It Dv LOCAL_CREDS
+This option may be enabled on a
+.Dv SOCK_DGRAM
+or a
+.Dv SOCK_STREAM
+socket.  This option provides a mechanism for the receiver to
+receive the credentials of the process as a
+.Xr recvmsg 2
+control message.  The msg_control field in the msghdr structure points
+to a buffer that contains a cmsghdr structure followed by a variable
+length sockcred structure, defined in
+.Pa \*[Lt]sys/socket.h\*[Gt]
+as follows:
+.Bd -literal
+struct sockcred {
+  id_t	sc_uid;		/* real user id */
+  uid_t	sc_euid;	/* effective user id */
+  gid_t	sc_gid;		/* real group id */
+  gid_t	sc_egid;	/* effective group id */
+  int	sc_ngroups;	/* number of supplemental groups */
+  gid_t	sc_groups[1];	/* variable length */
+};
+.Ed
+.Pp
+The
+.Fn SOCKCREDSIZE
+macro computes the size of the sockcred structure for a specified number
+of groups.
+The cmsghdr fields have the following values:
+.Bd -literal
+cmsg_len = sizeof(struct cmsghdr) + SOCKCREDSIZE(ngroups)
+cmsg_level = SOL_SOCKET
+cmsg_type = SCM_CREDS
+.Ed
+.It Dv LOCAL_CONNWAIT
+Used with 
+.Dv SOCK_STREAM
+sockets, this option causes the
+.Xr connect 2
+function to block until
+.Xr accept 2
+has been called on the listening socket.
 .Sh SEE ALSO
 .Xr socket 2 ,
 .Xr intro 4

sys/kern/uipc_usrreq.c

@@ -81,6 +81,7 @@ static	struct unp_head unp_shead, unp_dhead;
  */
 static const struct	sockaddr sun_noname = { sizeof(sun_noname), AF_LOCAL };
 static ino_t	unp_ino;		/* prototype for fake inode numbers */
+struct mbuf *unp_addsockcred(struct thread *, struct mbuf *);
 
 /*
  * Currently, UNIX domain sockets are protected by a single subsystem lock,
@@ -114,7 +115,7 @@ static int     unp_attach(struct socket *);
 static void    unp_detach(struct unpcb *);
 static int     unp_bind(struct unpcb *,struct sockaddr *, struct thread *);
 static int     unp_connect(struct socket *,struct sockaddr *, struct thread *);
-static int     unp_connect2(struct socket *so, struct socket *so2);
+static int     unp_connect2(struct socket *so, struct socket *so2, int);
 static void    unp_disconnect(struct unpcb *);
 static void    unp_shutdown(struct unpcb *);
 static void    unp_drop(struct unpcb *, int);
@@ -233,7 +234,7 @@ uipc_connect2(struct socket *so1, struct socket *so2)
 		UNP_UNLOCK();
 		return (EINVAL);
 	}
-	error = unp_connect2(so1, so2);
+	error = unp_connect2(so1, so2, PRU_CONNECT2);
 	UNP_UNLOCK();
 	return (error);
 }
@@ -421,6 +422,8 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 			from = (struct sockaddr *)unp->unp_addr;
 		else
 			from = &sun_noname;
+		if (unp->unp_conn->unp_flags & UNP_WANTCRED)
+			control = unp_addsockcred(td, control);
 		SOCKBUF_LOCK(&so2->so_rcv);
 		if (sbappendaddr_locked(&so2->so_rcv, from, m, control)) {
 			sorwakeup_locked(so2);
@@ -462,6 +465,14 @@ uipc_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *nam,
 			panic("uipc_send connected but no connection?");
 		so2 = unp->unp_conn->unp_socket;
 		SOCKBUF_LOCK(&so2->so_rcv);
+		if (unp->unp_conn->unp_flags & UNP_WANTCRED) {
+			/*
+			 * Credentials are passed only once on
+			 * SOCK_STREAM.
+			 */
+			unp->unp_conn->unp_flags &= ~UNP_WANTCRED;
+			control = unp_addsockcred(td, control);
+		}
 		/*
 		 * Send to paired receive port, and then reduce
 		 * send buffer hiwater marks to maintain backpressure.
@@ -604,20 +615,20 @@ uipc_ctloutput(struct socket *so, struct sockopt *sopt)
 {
 	struct unpcb *unp;
 	struct xucred xu;
-	int error;
+	int error, optval;
+
+	UNP_LOCK();
+	unp = sotounpcb(so);
+	if (unp == NULL) {
+		UNP_UNLOCK();
+		return (EINVAL);
+	}
+	error = 0;
 
 	switch (sopt->sopt_dir) {
 	case SOPT_GET:
 		switch (sopt->sopt_name) {
 		case LOCAL_PEERCRED:
-			error = 0;
-			UNP_LOCK();
-			unp = sotounpcb(so);
-			if (unp == NULL) {
-				UNP_UNLOCK();
-				error = EINVAL;
-				break;
-			}
 			if (unp->unp_flags & UNP_HAVEPC)
 				xu = unp->unp_peercred;
 			else {
@@ -626,20 +637,58 @@ uipc_ctloutput(struct socket *so, struct sockopt *sopt)
 				else
 					error = EINVAL;
 			}
-			UNP_UNLOCK();
 			if (error == 0)
 				error = sooptcopyout(sopt, &xu, sizeof(xu));
 			break;
+		case LOCAL_CREDS:
+			optval = unp->unp_flags & UNP_WANTCRED ? 1 : 0;
+			error = sooptcopyout(sopt, &optval, sizeof(optval));
+			break;
+		case LOCAL_CONNWAIT:
+			optval = unp->unp_flags & UNP_CONNWAIT ? 1 : 0;
+			error = sooptcopyout(sopt, &optval, sizeof(optval));
+			break;
 		default:
 			error = EOPNOTSUPP;
 			break;
 		}
 		break;
 	case SOPT_SET:
+		switch (sopt->sopt_name) {
+		case LOCAL_CREDS:
+		case LOCAL_CONNWAIT:
+			error = sooptcopyin(sopt, &optval, sizeof(optval),
+					    sizeof(optval));
+			if (error)
+				break;
+
+#define	OPTSET(bit) \
+	if (optval) \
+		unp->unp_flags |= bit; \
+	else \
+		unp->unp_flags &= ~bit;
+
+			switch (sopt->sopt_name) {
+			case LOCAL_CREDS:
+				OPTSET(UNP_WANTCRED);
+				break;
+			case LOCAL_CONNWAIT:
+				OPTSET(UNP_CONNWAIT);
+				break;
+			default:
+				break;
+			}
+			break;
+#undef	OPTSET
+		default:
+			error = ENOPROTOOPT;
+			break;
+		}
 	default:
 		error = EOPNOTSUPP;
 		break;
 	}
+	UNP_UNLOCK();
 	return (error);
 }
 
@@ -965,7 +1014,7 @@ unp_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
 
 		so2 = so3;
 	}
-	error = unp_connect2(so, so2);
+	error = unp_connect2(so, so2, PRU_CONNECT);
 bad2:
 	UNP_UNLOCK();
 	mtx_lock(&Giant);
@@ -980,7 +1029,7 @@ unp_connect(struct socket *so, struct sockaddr *nam, struct thread *td)
 }
 
 static int
-unp_connect2(struct socket *so, struct socket *so2)
+unp_connect2(struct socket *so, struct socket *so2, int req)
 {
 	struct unpcb *unp = sotounpcb(so);
 	struct unpcb *unp2;
@@ -1000,7 +1049,11 @@ unp_connect2(struct socket *so, struct socket *so2)
 
 	case SOCK_STREAM:
 		unp2->unp_conn = unp;
-		soisconnected(so);
+		if (req == PRU_CONNECT &&
+		    ((unp->unp_flags | unp2->unp_flags) & UNP_CONNWAIT))
+			soisconnecting(so);
+		else
+			soisconnected(so);
 		soisconnected(so2);
 		break;
 
@@ -1484,6 +1537,43 @@ unp_internalize(struct mbuf **controlp, struct thread *td)
 	return (error);
 }
 
+struct mbuf *
+unp_addsockcred(struct thread *td, struct mbuf *control)
+{
+	struct mbuf *m, *n;
+	struct sockcred *sc;
+	int ngroups;
+	int i;
+
+	ngroups = MIN(td->td_ucred->cr_ngroups, CMGROUP_MAX);
+
+	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;
+	sc->sc_euid = td->td_ucred->cr_uid;
+	sc->sc_gid = td->td_ucred->cr_rgid;
+	sc->sc_egid = td->td_ucred->cr_gid;
+	sc->sc_ngroups = ngroups;
+	for (i = 0; i < sc->sc_ngroups; i++)
+		sc->sc_groups[i] = td->td_ucred->cr_groups[i];
+
+	/*
+	 * If a control message already exists, append us to the end.
+	 */
+	if (control != NULL) {
+		for (n = control; n->m_next != NULL; n = n->m_next)
+			;
+		n->m_next = m;
+	} else
+		control = m;
+
+	return (control);
+}
+
 /*
  * unp_defer is thread-local during garbage collection, and does not require
  * explicit synchronization.  unp_gcing prevents other threads from entering

sys/sys/socket.h

@@ -439,6 +439,25 @@ struct cmsgcred {
 	short	cmcred_ngroups;		/* number or groups */
 	gid_t	cmcred_groups[CMGROUP_MAX];	/* groups */
 };
+
+/*
+ * Socket credentials.
+ */
+struct sockcred {
+	uid_t	sc_uid;			/* real user id */
+	uid_t	sc_euid;		/* effective user id */
+	gid_t	sc_gid;			/* real group id */
+	gid_t	sc_egid;		/* effective group id */
+	int	sc_ngroups;		/* number of supplemental groups */
+	gid_t	sc_groups[1];		/* variable length */
+};
+
+/*
+ * Compute size of a sockcred structure with groups.
+ */
+#define	SOCKCREDSIZE(ngrps) \
+	(sizeof(struct sockcred) + (sizeof(gid_t) * ((ngrps) - 1)))
+
 #endif /* __BSD_VISIBLE */
 
 /* given pointer to struct cmsghdr, return pointer to data */

sys/sys/un.h

@@ -53,7 +53,9 @@ struct sockaddr_un {
 #if __BSD_VISIBLE
 
 /* Socket options. */
-#define LOCAL_PEERCRED		0x001		/* retrieve peer credentails */
+#define	LOCAL_PEERCRED		0x001	/* retrieve peer credentials */
+#define	LOCAL_CREDS		0x002	/* pass credentials to receiver */
+#define	LOCAL_CONNWAIT		0x004	/* connects block until accepted */
 
 #ifdef _KERNEL
 struct mbuf;

sys/sys/unpcb.h

@@ -95,6 +95,8 @@ struct unpcb {
  */
 #define UNP_HAVEPC			0x001
 #define UNP_HAVEPCCACHED		0x002
+#define	UNP_WANTCRED			0x004	/* credentials wanted */
+#define	UNP_CONNWAIT			0x008	/* connect blocks until accepted */
 
 #define	sotounpcb(so)	((struct unpcb *)((so)->so_pcb))