[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 b5193229132..d22ab97ea72 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 3c51da6438c..19f7df702b0 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 3c51da6438c..19f7df702b0 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 8b1da3e58c5..01cfdf1d6d3 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 7177f8b9817..31db18fc871 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 d98cf85bafc..ebc830fee0d 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 802ae76195b..5755d57c4e9 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 a255006fb7b..d638ef3d50c 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 8b6680f223c..acdf748fcdc 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 f578ca4b776..a5966ec005a 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 0bb31e5aaca..36ebe4e186a 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 1bf54dc53c1..ce2eae1708b 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 e4b8177d4ac..c8b1da50e72 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 15a5298c874..1778a49a74c 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 553904ff933..ca70362eb56 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 4e0ce3a35ea..f6c4e5baf3f 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 59987dad335..754d46a50af 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 0240d366a0a..0dfe55ac2ef 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 f2cdbeae5d5..b4670260793 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 00f83f3a6d7..971d231be60 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 385e68f5bd9..b20c53c7441 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 795f81f9ec7..5ba72d95280 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 540619cb716..02daa097cdc 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;