[PATCH] selinux: Add SO_PEERSEC socket option and getpeersec LSM hook.

From: James Morris <jmorris@redhat.com>

This patch adds a new option for Unix sockets, SO_PEERSEC, and an
associated LSM hook, getpeersec.  The SELinux handler is also included.

The purpose of this is to allow applications to obtain each others security
credentials, analagously to the existing SO_PEERCRED option.

Examples of use are Security Enhanced D-BUS and Security Enhanced X.

This patch was previously approved in principle by David, and has been
updated with feedback from Chris Wright and extended to cover all
architectures.

include/asm-alpha/socket.h

@@ -48,6 +48,8 @@
 #define SO_TIMESTAMP		29
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
+#define SO_PEERSEC		30
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		19
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	20

include/asm-arm/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-arm26/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-cris/socket.h

@@ -47,6 +47,8 @@
 
 #define SO_ACCEPTCONN          30
 
+#define SO_PEERSEC             31
+
 #if defined(__KERNEL__)
 /* Socket types. */
 #define SOCK_STREAM     1               /* stream (connection) socket   */

include/asm-h8300/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-i386/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nasty libc5 fixup - bletch */
 #if defined(__KERNEL__) || !defined(__GLIBC__) || (__GLIBC__ < 2)
 /* Socket types. */

include/asm-ia64/socket.h

@@ -52,6 +52,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC             31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-m68k/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC             31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-mips/socket.h

@@ -66,6 +66,8 @@ To add: #define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
 #define SO_TIMESTAMP		29
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
+#define SO_PEERSEC             30
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-parisc/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		0x401c
 
+#define SO_PEERSEC		0x401d
+
 #if defined(__KERNEL__)
 #define SOCK_STREAM	1	/* stream (connection) socket	*/
 #define SOCK_DGRAM	2	/* datagram (conn.less) socket	*/

include/asm-ppc/socket.h

@@ -51,6 +51,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-ppc64/socket.h

@@ -52,6 +52,8 @@
 
 #define SO_ACCEPTCONN           30
 
+#define SO_PEERSEC             31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-s390/socket.h

@@ -53,6 +53,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-sh/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-sparc/socket.h

@@ -45,6 +45,8 @@
 #define SO_TIMESTAMP		0x001d
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
+#define SO_PEERSEC		0x100e
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	0x5002

include/asm-sparc64/socket.h

@@ -45,6 +45,8 @@
 #define SO_TIMESTAMP		0x001d
 #define SCM_TIMESTAMP		SO_TIMESTAMP
 
+#define SO_PEERSEC		0x001e
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	0x5002

include/asm-v850/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC		31
+
 /* Nast libc5 fixup - bletch */
 #if defined(__KERNEL__)
 /* Socket types. */

include/asm-x86_64/socket.h

@@ -45,6 +45,8 @@
 
 #define SO_ACCEPTCONN		30
 
+#define SO_PEERSEC             31
+
 /* Nasty libc5 fixup - bletch */
 #if defined(__KERNEL__) || !defined(__GLIBC__) || (__GLIBC__ < 2)
 /* Socket types. */

include/linux/security.h

@@ -757,6 +757,22 @@ struct swap_info_struct;
  *	incoming sk_buff @skb has been associated with a particular socket, @sk.
  *	@sk contains the sock (not socket) associated with the incoming sk_buff.
  *	@skb contains the incoming network data.
+ * @socket_getpeersec:
+ *	This hook allows the security module to provide peer socket security
+ *	state to userspace via getsockopt SO_GETPEERSEC.
+ *	@sock is the local socket.
+ *	@optval userspace memory where the security state is to be copied.
+ *	@optlen userspace int where the module should copy the actual length
+ *	of the security state.
+ *	@len as input is the maximum length to copy to userspace provided
+ *	by the caller.
+ *	Return 0 if all is well, otherwise, typical getsockopt return
+ *	values.
+ * @sk_alloc_security:
+ *      Allocate and attach a security structure to the sk->sk_security field,
+ *      which is used to copy security attributes between local stream sockets.
+ * @sk_free_security:
+ *	Deallocate security structure.
  *
  * Security hooks affecting all System V IPC operations.
  *
@@ -1183,6 +1199,9 @@ struct security_operations {
 	int (*socket_setsockopt) (struct socket * sock, int level, int optname);
 	int (*socket_shutdown) (struct socket * sock, int how);
 	int (*socket_sock_rcv_skb) (struct sock * sk, struct sk_buff * skb);
+	int (*socket_getpeersec) (struct socket *sock, char __user *optval, int __user *optlen, unsigned len);
+	int (*sk_alloc_security) (struct sock *sk, int family, int priority);
+	void (*sk_free_security) (struct sock *sk);
 #endif	/* CONFIG_SECURITY_NETWORK */
 };
 
@@ -2564,6 +2583,22 @@ static inline int security_sock_rcv_skb (struct sock * sk,
 {
 	return security_ops->socket_sock_rcv_skb (sk, skb);
 }
+
+static inline int security_socket_getpeersec(struct socket *sock, char __user *optval,
+					     int __user *optlen, unsigned len)
+{
+	return security_ops->socket_getpeersec(sock, optval, optlen, len);
+}
+
+static inline int security_sk_alloc(struct sock *sk, int family, int priority)
+{
+	return security_ops->sk_alloc_security(sk, family, priority);
+}
+
+static inline void security_sk_free(struct sock *sk)
+{
+	return security_ops->sk_free_security(sk);
+}
 #else	/* CONFIG_SECURITY_NETWORK */
 static inline int security_unix_stream_connect(struct socket * sock,
 					       struct socket * other, 
@@ -2664,6 +2699,21 @@ static inline int security_sock_rcv_skb (struct sock * sk,
 {
 	return 0;
 }
+
+static inline int security_socket_getpeersec(struct socket *sock, char __user *optval,
+					     int __user *optlen, unsigned len)
+{
+	return -ENOPROTOOPT;
+}
+
+static inline int security_sk_alloc(struct sock *sk, int family, int priority)
+{
+	return 0;
+}
+
+static inline void security_sk_free(struct sock *sk)
+{
+}
 #endif	/* CONFIG_SECURITY_NETWORK */
 
 #endif /* ! __LINUX_SECURITY_H */

include/net/sock.h

@@ -246,6 +246,7 @@ struct sock {
 	struct socket		*sk_socket;
 	void			*sk_user_data;
 	struct module		*sk_owner;
+	void			*sk_security;
 	void			(*sk_state_change)(struct sock *sk);
 	void			(*sk_data_ready)(struct sock *sk, int bytes);
 	void			(*sk_write_space)(struct sock *sk);

net/core/sock.c

@@ -564,6 +564,9 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 			v.val = sk->sk_state == TCP_LISTEN;
 			break;
 
+		case SO_PEERSEC:
+			return security_socket_getpeersec(sock, optval, optlen, len);
+
 		default:
 			return(-ENOPROTOOPT);
 	}
@@ -606,6 +609,11 @@ struct sock *sk_alloc(int family, int priority, int zero_it, kmem_cache_t *slab)
 			sock_lock_init(sk);
 		}
 		sk->sk_slab = slab;
+		
+		if (security_sk_alloc(sk, family, priority)) {
+			kmem_cache_free(slab, sk);
+			sk = NULL;
+		}
 	}
 	return sk;
 }
@@ -628,6 +636,7 @@ void sk_free(struct sock *sk)
 		printk(KERN_DEBUG "%s: optmem leakage (%d bytes) detected.\n",
 		       __FUNCTION__, atomic_read(&sk->sk_omem_alloc));
 
+	security_sk_free(sk);
 	kmem_cache_free(sk->sk_slab, sk);
 	module_put(owner);
 }

security/dummy.c

@@ -793,6 +793,21 @@ static int dummy_socket_sock_rcv_skb (struct sock *sk, struct sk_buff *skb)
 {
 	return 0;
 }
+
+static int dummy_socket_getpeersec(struct socket *sock, char __user *optval,
+				   int __user *optlen, unsigned len)
+{
+	return -ENOPROTOOPT;
+}
+
+static inline int dummy_sk_alloc_security (struct sock *sk, int family, int priority)
+{
+	return 0;
+}
+
+static inline void dummy_sk_free_security (struct sock *sk)
+{
+}
 #endif	/* CONFIG_SECURITY_NETWORK */
 
 static int dummy_register_security (const char *name, struct security_operations *ops)
@@ -969,6 +984,9 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, socket_getsockopt);
 	set_to_dummy_if_null(ops, socket_shutdown);
 	set_to_dummy_if_null(ops, socket_sock_rcv_skb);
+	set_to_dummy_if_null(ops, socket_getpeersec);
+	set_to_dummy_if_null(ops, sk_alloc_security);
+	set_to_dummy_if_null(ops, sk_free_security);
 #endif	/* CONFIG_SECURITY_NETWORK */
 }
 

security/selinux/hooks.c

@@ -244,6 +244,39 @@ static void superblock_free_security(struct super_block *sb)
 	kfree(sbsec);
 }
 
+#ifdef CONFIG_SECURITY_NETWORK
+static int sk_alloc_security(struct sock *sk, int family, int priority)
+{
+	struct sk_security_struct *ssec;
+
+	if (family != PF_UNIX)
+		return 0;
+
+	ssec = kmalloc(sizeof(*ssec), priority);
+	if (!ssec)
+		return -ENOMEM;
+
+	memset(ssec, 0, sizeof(*ssec));
+	ssec->magic = SELINUX_MAGIC;
+	ssec->sk = sk;
+	ssec->peer_sid = SECINITSID_UNLABELED;
+	sk->sk_security = ssec;
+
+	return 0;
+}
+
+static void sk_free_security(struct sock *sk)
+{
+	struct task_security_struct *ssec = sk->sk_security;
+
+	if (sk->sk_family != PF_UNIX || ssec->magic != SELINUX_MAGIC)
+		return;
+
+	sk->sk_security = NULL;
+	kfree(ssec);
+}
+#endif	/* CONFIG_SECURITY_NETWORK */
+
 /* The security server must be initialized before
    any labeling or access decisions can be provided. */
 extern int ss_initialized;
@@ -2540,6 +2573,7 @@ static int selinux_socket_unix_stream_connect(struct socket *sock,
 					      struct socket *other,
 					      struct sock *newsk)
 {
+	struct sk_security_struct *ssec;
 	struct inode_security_struct *isec;
 	struct inode_security_struct *other_isec;
 	struct avc_audit_data ad;
@@ -2558,6 +2592,14 @@ static int selinux_socket_unix_stream_connect(struct socket *sock,
 	if (err)
 		return err;
 
+	/* connecting socket */
+	ssec = sock->sk->sk_security;
+	ssec->peer_sid = other_isec->sid;
+	
+	/* server child socket */
+	ssec = newsk->sk_security;
+	ssec->peer_sid = isec->sid;
+	
 	return 0;
 }
 
@@ -2664,6 +2706,54 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	return err;
 }
 
+static int selinux_socket_getpeersec(struct socket *sock, char __user *optval,
+				     int __user *optlen, unsigned len)
+{
+	int err = 0;
+	char *scontext;
+	u32 scontext_len;
+	struct sk_security_struct *ssec;
+	struct inode_security_struct *isec;
+
+	isec = SOCK_INODE(sock)->i_security;
+	if (isec->sclass != SECCLASS_UNIX_STREAM_SOCKET) {
+		err = -ENOPROTOOPT;
+		goto out;
+	}
+
+	ssec = sock->sk->sk_security;
+	
+	err = security_sid_to_context(ssec->peer_sid, &scontext, &scontext_len);
+	if (err)
+		goto out;
+
+	if (scontext_len > len) {
+		err = -ERANGE;
+		goto out_len;
+	}
+
+	if (copy_to_user(optval, scontext, scontext_len))
+		err = -EFAULT;
+
+out_len:
+	if (put_user(scontext_len, optlen))
+		err = -EFAULT;
+
+	kfree(scontext);
+out:	
+	return err;
+}
+
+static int selinux_sk_alloc_security(struct sock *sk, int family, int priority)
+{
+	return sk_alloc_security(sk, family, priority);
+}
+
+static void selinux_sk_free_security(struct sock *sk)
+{
+	sk_free_security(sk);
+}
+
 #ifdef CONFIG_NETFILTER
 static unsigned int selinux_ip_postroute_last(unsigned int hooknum,
                                               struct sk_buff **pskb,
@@ -2741,6 +2831,7 @@ static unsigned int selinux_ip_postroute_last(unsigned int hooknum,
 out:
 	return err;
 }
+
 #endif	/* CONFIG_NETFILTER */
 
 #endif	/* CONFIG_SECURITY_NETWORK */
@@ -3479,6 +3570,9 @@ struct security_operations selinux_ops = {
 	.socket_setsockopt =		selinux_socket_setsockopt,
 	.socket_shutdown =		selinux_socket_shutdown,
 	.socket_sock_rcv_skb =		selinux_socket_sock_rcv_skb,
+	.socket_getpeersec =		selinux_socket_getpeersec,
+	.sk_alloc_security =		selinux_sk_alloc_security,
+	.sk_free_security =		selinux_sk_free_security,
 #endif
 };
 

security/selinux/include/objsec.h

@@ -100,6 +100,12 @@ struct netif_security_struct {
 	struct avc_entry_ref avcr;	/* reference to permissions */
 };
 
+struct sk_security_struct {
+	unsigned long magic;		/* magic number for this module */
+	struct sock *sk;		/* back pointer to sk object */
+	u32 peer_sid;			/* SID of peer */
+};
+
 extern int inode_security_set_sid(struct inode *inode, u32 sid);
 
 #endif /* _SELINUX_OBJSEC_H_ */