From 2c7946a7bf45ae86736ab3b43d0085e43947945c Mon Sep 17 00:00:00 2001 From: Catherine Zhang Date: Mon, 20 Mar 2006 22:41:23 -0800 Subject: [SECURITY]: TCP/UDP getpeersec This patch implements an application of the LSM-IPSec networking controls whereby an application can determine the label of the security association its TCP or UDP sockets are currently connected to via getsockopt and the auxiliary data mechanism of recvmsg. Patch purpose: This patch enables a security-aware application to retrieve the security context of an IPSec security association a particular TCP or UDP socket is using. The application can then use this security context to determine the security context for processing on behalf of the peer at the other end of this connection. In the case of UDP, the security context is for each individual packet. An example application is the inetd daemon, which could be modified to start daemons running at security contexts dependent on the remote client. Patch design approach: - Design for TCP The patch enables the SELinux LSM to set the peer security context for a socket based on the security context of the IPSec security association. The application may retrieve this context using getsockopt. When called, the kernel determines if the socket is a connected (TCP_ESTABLISHED) TCP socket and, if so, uses the dst_entry cache on the socket to retrieve the security associations. If a security association has a security context, the context string is returned, as for UNIX domain sockets. - Design for UDP Unlike TCP, UDP is connectionless. This requires a somewhat different API to retrieve the peer security context. With TCP, the peer security context stays the same throughout the connection, thus it can be retrieved at any time between when the connection is established and when it is torn down. With UDP, each read/write can have different peer and thus the security context might change every time. As a result the security context retrieval must be done TOGETHER with the packet retrieval. The solution is to 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). Patch implementation details: - Implementation for TCP The security context can be retrieved by applications using getsockopt with the existing SO_PEERSEC flag. As an example (ignoring error checking): getsockopt(sockfd, SOL_SOCKET, SO_PEERSEC, optbuf, &optlen); printf("Socket peer context is: %s\n", optbuf); The SELinux function, selinux_socket_getpeersec, is extended to check for labeled security associations for connected (TCP_ESTABLISHED == sk->sk_state) TCP sockets only. If so, the socket has a dst_cache of struct dst_entry values that may refer to security associations. If these have security associations with security contexts, the security context is returned. getsockopt returns a buffer that contains a security context string or the buffer is unmodified. - Implementation for UDP To retrieve the security context, the application first indicates to the kernel such desire by setting the IP_PASSSEC option via getsockopt. Then the application retrieves the security context using the auxiliary data mechanism. An example server application for UDP should look like this: toggle = 1; toggle_len = sizeof(toggle); setsockopt(sockfd, SOL_IP, IP_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_IP && cmsg_hdr->cmsg_type == SCM_SECURITY) { memcpy(&scontext, CMSG_DATA(cmsg_hdr), sizeof(scontext)); } } ip_setsockopt is enhanced with a new socket option IP_PASSSEC to allow a server socket to receive security context of the peer. A new ancillary message type SCM_SECURITY. When the packet is received we get the security context from the sec_path pointer which is contained in the sk_buff, and copy it to the ancillary message space. An additional LSM hook, selinux_socket_getpeersec_udp, is defined to retrieve the security context from the SELinux space. The existing function, selinux_socket_getpeersec does not suit our purpose, because the security context is copied directly to user space, rather than to kernel space. Testing: We have tested the patch by setting up TCP and UDP connections between applications on two machines using the IPSec policies that result in labeled security associations being built. For TCP, we can then extract the peer security context using getsockopt on either end. For UDP, the receiving end can retrieve the security context using the auxiliary data mechanism of recvmsg. Signed-off-by: Catherine Zhang Acked-by: James Morris Acked-by: Herbert Xu Signed-off-by: David S. Miller --- security/selinux/hooks.c | 46 +++++++++++++++++++++++++++++++++++++++------- 1 file changed, 39 insertions(+), 7 deletions(-) (limited to 'security/selinux/hooks.c') diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index b65c201e9ff..5b16196f282 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3318,24 +3318,38 @@ out: return err; } -static int selinux_socket_getpeersec(struct socket *sock, char __user *optval, - int __user *optlen, unsigned len) +static int selinux_socket_getpeersec_stream(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; + u32 peer_sid = 0; isec = SOCK_INODE(sock)->i_security; - if (isec->sclass != SECCLASS_UNIX_STREAM_SOCKET) { + + /* if UNIX_STREAM check peer_sid, if TCP check dst for labelled sa */ + if (isec->sclass == SECCLASS_UNIX_STREAM_SOCKET) { + ssec = sock->sk->sk_security; + peer_sid = ssec->peer_sid; + } + else if (isec->sclass == SECCLASS_TCP_SOCKET) { + peer_sid = selinux_socket_getpeer_stream(sock->sk); + + if (peer_sid == SECSID_NULL) { + err = -ENOPROTOOPT; + goto out; + } + } + else { err = -ENOPROTOOPT; goto out; } - ssec = sock->sk->sk_security; - - err = security_sid_to_context(ssec->peer_sid, &scontext, &scontext_len); + err = security_sid_to_context(peer_sid, &scontext, &scontext_len); + if (err) goto out; @@ -3356,6 +3370,23 @@ out: return err; } +static int selinux_socket_getpeersec_dgram(struct sk_buff *skb, char **secdata, u32 *seclen) +{ + int err = 0; + u32 peer_sid = selinux_socket_getpeer_dgram(skb); + + if (peer_sid == SECSID_NULL) + return -EINVAL; + + err = security_sid_to_context(peer_sid, secdata, seclen); + if (err) + return err; + + return 0; +} + + + static int selinux_sk_alloc_security(struct sock *sk, int family, gfp_t priority) { return sk_alloc_security(sk, family, priority); @@ -4344,7 +4375,8 @@ static 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, + .socket_getpeersec_stream = selinux_socket_getpeersec_stream, + .socket_getpeersec_dgram = selinux_socket_getpeersec_dgram, .sk_alloc_security = selinux_sk_alloc_security, .sk_free_security = selinux_sk_free_security, .sk_getsid = selinux_sk_getsid_security, -- cgit v1.2.3-70-g09d2 From 8aad38752e81d1d4de67e3d8e2524618ce7c9276 Mon Sep 17 00:00:00 2001 From: Stephen Smalley Date: Wed, 22 Mar 2006 00:09:13 -0800 Subject: [PATCH] selinux: Disable automatic labeling of new inodes when no policy is loaded This patch disables the automatic labeling of new inodes on disk when no policy is loaded. Discussion is here: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=180296 In short, we're changing the behavior so that when no policy is loaded, SELinux does not label files at all. Currently it does add an 'unlabeled' label in this case, which we've found causes problems later. SELinux always maintains a safe internal label if there is none, so with this patch, we just stick with that and wait until a policy is loaded before adding a persistent label on disk. The effect is simply that if you boot with SELinux enabled but no policy loaded and create a file in that state, SELinux won't try to set a security extended attribute on the new inode on the disk. This is the only sane behavior for SELinux in that state, as it cannot determine the right label to assign in the absence of a policy. That state usually doesn't occur, but the rawhide installer seemed to be misbehaving temporarily so it happened to show up on a test install. Signed-off-by: Stephen Smalley Acked-by: James Morris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/selinux/hooks.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'security/selinux/hooks.c') diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 5b16196f282..9ff51c668f0 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1957,7 +1957,7 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, inode_security_set_sid(inode, newsid); - if (sbsec->behavior == SECURITY_FS_USE_MNTPOINT) + if (!ss_initialized || sbsec->behavior == SECURITY_FS_USE_MNTPOINT) return -EOPNOTSUPP; if (name) { -- cgit v1.2.3-70-g09d2 From cf01efd098597f7ee88a61e645afacba987c4531 Mon Sep 17 00:00:00 2001 From: James Morris Date: Wed, 22 Mar 2006 00:09:21 -0800 Subject: [PATCH] SELinux: cleanup stray variable in selinux_inode_init_security() Remove an unneded pointer variable in selinux_inode_init_security(). Signed-off-by: James Morris Acked-by: Stephen Smalley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/selinux/hooks.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'security/selinux/hooks.c') diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 9ff51c668f0..bdd0b32f010 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1929,7 +1929,6 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, struct task_security_struct *tsec; struct inode_security_struct *dsec; struct superblock_security_struct *sbsec; - struct inode_security_struct *isec; u32 newsid, clen; int rc; char *namep = NULL, *context; @@ -1937,7 +1936,6 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, tsec = current->security; dsec = dir->i_security; sbsec = dir->i_sb->s_security; - isec = inode->i_security; if (tsec->create_sid && sbsec->behavior != SECURITY_FS_USE_MNTPOINT) { newsid = tsec->create_sid; -- cgit v1.2.3-70-g09d2 From 7cae7e26f245151b9ccad868bf2edf8c8048d307 Mon Sep 17 00:00:00 2001 From: James Morris Date: Wed, 22 Mar 2006 00:09:22 -0800 Subject: [PATCH] SELinux: add slab cache for inode security struct Add a slab cache for the SELinux inode security struct, one of which is allocated for every inode instantiated by the system. The memory savings are considerable. On 64-bit, instead of the size-128 cache, we have a slab object of 96 bytes, saving 32 bytes per object. After booting, I see about 4000 of these and then about 17,000 after a kernel compile. With this patch, we save around 530KB of kernel memory in the latter case. On 32-bit, the savings are about half of this. Signed-off-by: James Morris Acked-by: Stephen Smalley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/selinux/hooks.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'security/selinux/hooks.c') diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index bdd0b32f010..ccaf988f372 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -117,6 +117,8 @@ static struct security_operations *secondary_ops = NULL; static LIST_HEAD(superblock_security_head); static DEFINE_SPINLOCK(sb_security_lock); +static kmem_cache_t *sel_inode_cache; + /* Allocate and free functions for each kind of security blob. */ static int task_alloc_security(struct task_struct *task) @@ -146,10 +148,11 @@ static int inode_alloc_security(struct inode *inode) struct task_security_struct *tsec = current->security; struct inode_security_struct *isec; - isec = kzalloc(sizeof(struct inode_security_struct), GFP_KERNEL); + isec = kmem_cache_alloc(sel_inode_cache, SLAB_KERNEL); if (!isec) return -ENOMEM; + memset(isec, 0, sizeof(*isec)); init_MUTEX(&isec->sem); INIT_LIST_HEAD(&isec->list); isec->inode = inode; @@ -172,7 +175,7 @@ static void inode_free_security(struct inode *inode) spin_unlock(&sbsec->isec_lock); inode->i_security = NULL; - kfree(isec); + kmem_cache_free(sel_inode_cache, isec); } static int file_alloc_security(struct file *file) @@ -4406,6 +4409,9 @@ static __init int selinux_init(void) tsec = current->security; tsec->osid = tsec->sid = SECINITSID_KERNEL; + sel_inode_cache = kmem_cache_create("selinux_inode_security", + sizeof(struct inode_security_struct), + 0, SLAB_PANIC, NULL, NULL); avc_init(); original_ops = secondary_ops = security_ops; -- cgit v1.2.3-70-g09d2