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authorCatherine Zhang <cxzhang@watson.ibm.com>2006-03-20 22:41:23 -0800
committerDavid S. Miller <davem@davemloft.net>2006-03-20 22:41:23 -0800
commit2c7946a7bf45ae86736ab3b43d0085e43947945c (patch)
treeb956f301033ebaefe8d2701b257edfd947f537f3 /security/selinux
parentbe33690d8fcf40377f16193c463681170eb6b295 (diff)
downloadlinux-2.6.34-ux500-2c7946a7bf45ae86736ab3b43d0085e43947945c.tar.gz
[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 <cxzhang@watson.ibm.com> Acked-by: James Morris <jmorris@namei.org> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'security/selinux')
-rw-r--r--security/selinux/hooks.c46
-rw-r--r--security/selinux/include/xfrm.h2
-rw-r--r--security/selinux/xfrm.c68
3 files changed, 109 insertions, 7 deletions
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,
diff --git a/security/selinux/include/xfrm.h b/security/selinux/include/xfrm.h
index 8e87996c6dd..a7f388bff3f 100644
--- a/security/selinux/include/xfrm.h
+++ b/security/selinux/include/xfrm.h
@@ -39,6 +39,8 @@ static inline u32 selinux_no_sk_sid(struct flowi *fl)
#ifdef CONFIG_SECURITY_NETWORK_XFRM
int selinux_xfrm_sock_rcv_skb(u32 sid, struct sk_buff *skb);
int selinux_xfrm_postroute_last(u32 isec_sid, struct sk_buff *skb);
+u32 selinux_socket_getpeer_stream(struct sock *sk);
+u32 selinux_socket_getpeer_dgram(struct sk_buff *skb);
#else
static inline int selinux_xfrm_sock_rcv_skb(u32 isec_sid, struct sk_buff *skb)
{
diff --git a/security/selinux/xfrm.c b/security/selinux/xfrm.c
index b2af7ca496c..dfab6c88669 100644
--- a/security/selinux/xfrm.c
+++ b/security/selinux/xfrm.c
@@ -225,6 +225,74 @@ void selinux_xfrm_state_free(struct xfrm_state *x)
}
/*
+ * SELinux internal function to retrieve the context of a connected
+ * (sk->sk_state == TCP_ESTABLISHED) TCP socket based on its security
+ * association used to connect to the remote socket.
+ *
+ * Retrieve via getsockopt SO_PEERSEC.
+ */
+u32 selinux_socket_getpeer_stream(struct sock *sk)
+{
+ struct dst_entry *dst, *dst_test;
+ u32 peer_sid = SECSID_NULL;
+
+ if (sk->sk_state != TCP_ESTABLISHED)
+ goto out;
+
+ dst = sk_dst_get(sk);
+ if (!dst)
+ goto out;
+
+ for (dst_test = dst; dst_test != 0;
+ dst_test = dst_test->child) {
+ struct xfrm_state *x = dst_test->xfrm;
+
+ if (x && selinux_authorizable_xfrm(x)) {
+ struct xfrm_sec_ctx *ctx = x->security;
+ peer_sid = ctx->ctx_sid;
+ break;
+ }
+ }
+ dst_release(dst);
+
+out:
+ return peer_sid;
+}
+
+/*
+ * SELinux internal function to retrieve the context of a UDP packet
+ * based on its security association used to connect to the remote socket.
+ *
+ * Retrieve via setsockopt IP_PASSSEC and recvmsg with control message
+ * type SCM_SECURITY.
+ */
+u32 selinux_socket_getpeer_dgram(struct sk_buff *skb)
+{
+ struct sec_path *sp;
+
+ if (skb == NULL)
+ return SECSID_NULL;
+
+ if (skb->sk->sk_protocol != IPPROTO_UDP)
+ return SECSID_NULL;
+
+ sp = skb->sp;
+ if (sp) {
+ int i;
+
+ for (i = sp->len-1; i >= 0; i--) {
+ struct xfrm_state *x = sp->x[i].xvec;
+ if (selinux_authorizable_xfrm(x)) {
+ struct xfrm_sec_ctx *ctx = x->security;
+ return ctx->ctx_sid;
+ }
+ }
+ }
+
+ return SECSID_NULL;
+}
+
+/*
* LSM hook that controls access to unlabelled packets. If
* a xfrm_state is authorizable (defined by macro) then it was
* already authorized by the IPSec process. If not, then