[AF_UNIX]: Datagram getpeersec

This patch implements an API whereby an application can determine the
label of its peer's Unix datagram sockets via the auxiliary data mechanism of
recvmsg.

Patch purpose:

This patch enables a security-aware application to retrieve the
security context of the peer of a Unix datagram socket.  The application
can then use this security context to determine the security context for
processing on behalf of the peer who sent the packet.

Patch design and implementation:

The design and implementation is very similar to the UDP case for INET
sockets.  Basically we build upon the existing Unix domain socket API for
retrieving user credentials.  Linux offers the API for obtaining user
credentials via ancillary messages (i.e., out of band/control messages
that are bundled together with a normal message).  To retrieve the security
context, the application first indicates to the kernel such desire by
setting the SO_PASSSEC option via getsockopt.  Then the application
retrieves the security context using the auxiliary data mechanism.

An example server application for Unix datagram socket should look like this:

toggle = 1;
toggle_len = sizeof(toggle);

setsockopt(sockfd, SOL_SOCKET, SO_PASSSEC, &toggle, &toggle_len);
recvmsg(sockfd, &msg_hdr, 0);
if (msg_hdr.msg_controllen > sizeof(struct cmsghdr)) {
    cmsg_hdr = CMSG_FIRSTHDR(&msg_hdr);
    if (cmsg_hdr->cmsg_len <= CMSG_LEN(sizeof(scontext)) &&
        cmsg_hdr->cmsg_level == SOL_SOCKET &&
        cmsg_hdr->cmsg_type == SCM_SECURITY) {
        memcpy(&scontext, CMSG_DATA(cmsg_hdr), sizeof(scontext));
    }
}

sock_setsockopt is enhanced with a new socket option SOCK_PASSSEC to allow
a server socket to receive security context of the peer.

Testing:

We have tested the patch by setting up Unix datagram client and server
applications.  We verified that the server can retrieve the security context
using the auxiliary data mechanism of recvmsg.

Signed-off-by: Catherine Zhang <cxzhang@watson.ibm.com>
Acked-by: Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

23 files changed, 44 insertions, 0 deletions

diff --git a/include/asm-alpha/socket.h b/include/asm-alpha/socket.h
index b519322..d22ab97 100644
--- a/include/asm-alpha/socket.h
+++ b/include/asm-alpha/socket.h
@@ -51,6 +51,7 @@
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
 #define SO_PEERSEC		30
+#define SO_PASSSEC		34
 
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		19
diff --git a/include/asm-arm/socket.h b/include/asm-arm/socket.h
index 3c51da6..19f7df7 100644
--- a/include/asm-arm/socket.h
+++ b/include/asm-arm/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-arm26/socket.h b/include/asm-arm26/socket.h
index 3c51da6..19f7df7 100644
--- a/include/asm-arm26/socket.h
+++ b/include/asm-arm26/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-cris/socket.h b/include/asm-cris/socket.h
index 8b1da3e..01cfdf1 100644
--- a/include/asm-cris/socket.h
+++ b/include/asm-cris/socket.h
@@ -50,6 +50,7 @@
 #define SO_ACCEPTCONN          30
 
 #define SO_PEERSEC             31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
 
diff --git a/include/asm-frv/socket.h b/include/asm-frv/socket.h
index 7177f8b..31db18f 100644
--- a/include/asm-frv/socket.h
+++ b/include/asm-frv/socket.h
@@ -48,6 +48,7 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
 
diff --git a/include/asm-h8300/socket.h b/include/asm-h8300/socket.h
index d98cf85..ebc830f 100644
--- a/include/asm-h8300/socket.h
+++ b/include/asm-h8300/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-i386/socket.h b/include/asm-i386/socket.h
index 802ae76..5755d57 100644
--- a/include/asm-i386/socket.h
+++ b/include/asm-i386/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-ia64/socket.h b/include/asm-ia64/socket.h
index a255006..d638ef3 100644
--- a/include/asm-ia64/socket.h
+++ b/include/asm-ia64/socket.h
@@ -57,5 +57,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC             31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_IA64_SOCKET_H */
diff --git a/include/asm-m32r/socket.h b/include/asm-m32r/socket.h
index 8b6680f..acdf748 100644
--- a/include/asm-m32r/socket.h
+++ b/include/asm-m32r/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_M32R_SOCKET_H */
diff --git a/include/asm-m68k/socket.h b/include/asm-m68k/socket.h
index f578ca4..a5966ec 100644
--- a/include/asm-m68k/socket.h
+++ b/include/asm-m68k/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC             31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-mips/socket.h b/include/asm-mips/socket.h
index 0bb31e5..36ebe4e 100644
--- a/include/asm-mips/socket.h
+++ b/include/asm-mips/socket.h
@@ -69,6 +69,7 @@ To add: #define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
 #define SO_PEERSEC		30
 #define SO_SNDBUFFORCE		31
 #define SO_RCVBUFFORCE		33
+#define SO_PASSSEC		34
 
 #ifdef __KERNEL__
 
diff --git a/include/asm-parisc/socket.h b/include/asm-parisc/socket.h
index 1bf54dc..ce2eae1 100644
--- a/include/asm-parisc/socket.h
+++ b/include/asm-parisc/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		0x401c
 
 #define SO_PEERSEC		0x401d
+#define SO_PASSSEC		0x401e
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-powerpc/socket.h b/include/asm-powerpc/socket.h
index e4b8177..c8b1da5 100644
--- a/include/asm-powerpc/socket.h
+++ b/include/asm-powerpc/socket.h
@@ -55,5 +55,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif	/* _ASM_POWERPC_SOCKET_H */
diff --git a/include/asm-s390/socket.h b/include/asm-s390/socket.h
index 15a5298..1778a49 100644
--- a/include/asm-s390/socket.h
+++ b/include/asm-s390/socket.h
@@ -56,5 +56,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-sh/socket.h b/include/asm-sh/socket.h
index 553904f..ca70362 100644
--- a/include/asm-sh/socket.h
+++ b/include/asm-sh/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* __ASM_SH_SOCKET_H */
diff --git a/include/asm-sparc/socket.h b/include/asm-sparc/socket.h
index 4e0ce3a..f6c4e5b 100644
--- a/include/asm-sparc/socket.h
+++ b/include/asm-sparc/socket.h
@@ -48,6 +48,7 @@
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
 #define SO_PEERSEC		0x001e
+#define SO_PASSSEC		0x001f
 
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
diff --git a/include/asm-sparc64/socket.h b/include/asm-sparc64/socket.h
index 59987da..754d46a 100644
--- a/include/asm-sparc64/socket.h
+++ b/include/asm-sparc64/socket.h
@@ -48,6 +48,7 @@
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
 #define SO_PEERSEC		0x001e
+#define SO_PASSSEC		0x001f
 
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
diff --git a/include/asm-v850/socket.h b/include/asm-v850/socket.h
index 0240d36..0dfe55a 100644
--- a/include/asm-v850/socket.h
+++ b/include/asm-v850/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif /* __V850_SOCKET_H__ */
diff --git a/include/asm-x86_64/socket.h b/include/asm-x86_64/socket.h
index f2cdbea..b467026 100644
--- a/include/asm-x86_64/socket.h
+++ b/include/asm-x86_64/socket.h
@@ -48,5 +48,6 @@
 #define SO_ACCEPTCONN		30
 
 #define SO_PEERSEC             31
+#define SO_PASSSEC		34
 
 #endif /* _ASM_SOCKET_H */
diff --git a/include/asm-xtensa/socket.h b/include/asm-xtensa/socket.h
index 00f83f3..971d231 100644
--- a/include/asm-xtensa/socket.h
+++ b/include/asm-xtensa/socket.h
@@ -59,5 +59,6 @@
 
 #define SO_ACCEPTCONN		30
 #define SO_PEERSEC		31
+#define SO_PASSSEC		34
 
 #endif	/* _XTENSA_SOCKET_H */
diff --git a/include/linux/net.h b/include/linux/net.h
index 385e68f..b20c53c 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -61,6 +61,7 @@ typedef enum {
 #define SOCK_ASYNC_WAITDATA	1
 #define SOCK_NOSPACE		2
 #define SOCK_PASSCRED		3
+#define SOCK_PASSSEC		4
 
 #ifndef ARCH_HAS_SOCKET_TYPES
 /**
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 795f81f..5ba72d9 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -53,10 +53,16 @@ struct unix_address {
 struct unix_skb_parms {
 	struct ucred		creds;		/* Skb credentials	*/
 	struct scm_fp_list	*fp;		/* Passed files		*/
+#ifdef CONFIG_SECURITY_NETWORK
+	char			*secdata;	/* Security context	*/
+	u32			seclen;		/* Security length	*/
+#endif
 };
 
 #define UNIXCB(skb) 	(*(struct unix_skb_parms*)&((skb)->cb))
 #define UNIXCREDS(skb)	(&UNIXCB((skb)).creds)
+#define UNIXSECDATA(skb)	(&UNIXCB((skb)).secdata)
+#define UNIXSECLEN(skb)		(&UNIXCB((skb)).seclen)
 
 #define unix_state_rlock(s)	spin_lock(&unix_sk(s)->lock)
 #define unix_state_runlock(s)	spin_unlock(&unix_sk(s)->lock)
diff --git a/include/net/scm.h b/include/net/scm.h
index 540619c..02daa09 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -19,6 +19,10 @@ struct scm_cookie
 {
 	struct ucred		creds;		/* Skb credentials	*/
 	struct scm_fp_list	*fp;		/* Passed files		*/
+#ifdef CONFIG_SECURITY_NETWORK
+	char			*secdata;	/* Security context	*/
+	u32			seclen;		/* Security length	*/
+#endif
 	unsigned long		seq;		/* Connection seqno	*/
 };
 
@@ -48,6 +52,17 @@ static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
 	return __scm_send(sock, msg, scm);
 }
 
+#ifdef CONFIG_SECURITY_NETWORK
+static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
+{
+	if (test_bit(SOCK_PASSSEC, &sock->flags) && scm->secdata != NULL)
+		put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, scm->seclen, scm->secdata);
+}
+#else
+static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
+{ }
+#endif /* CONFIG_SECURITY_NETWORK */
+
 static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
 				struct scm_cookie *scm, int flags)
 {
@@ -62,6 +77,8 @@ static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
 	if (test_bit(SOCK_PASSCRED, &sock->flags))
 		put_cmsg(msg, SOL_SOCKET, SCM_CREDENTIALS, sizeof(scm->creds), &scm->creds);
 
+	scm_passec(sock, msg, scm);
+
 	if (!scm->fp)
 		return;