[v17,05/23] net: Prepare UDS for security module stacking
diff mbox series

Message ID 20200514221142.11857-6-casey@schaufler-ca.com
State Superseded
Headers show
Series
  • LSM: Module stacking for AppArmor
Related show

Commit Message

Casey Schaufler May 14, 2020, 10:11 p.m. UTC
Change the data used in UDS SO_PEERSEC processing from a
secid to a more general struct lsmblob. Update the
security_socket_getpeersec_dgram() interface to use the
lsmblob. There is a small amount of scaffolding code
that will come out when the security_secid_to_secctx()
code is brought in line with the lsmblob.

The secid field of the unix_skb_parms structure has been
replaced with a pointer to an lsmblob structure, and the
lsmblob is allocated as needed. This is similar to how the
list of passed files is managed. While an lsmblob structure
will fit in the available space today, there is no guarantee
that the addition of other data to the unix_skb_parms or
support for additional security modules wouldn't exceed what
is available.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
cc: netdev@vger.kernel.org
---
 include/linux/security.h |  7 +++++--
 include/net/af_unix.h    |  2 +-
 include/net/scm.h        |  8 +++++---
 net/ipv4/ip_sockglue.c   |  8 +++++---
 net/unix/af_unix.c       |  7 ++++---
 net/unix/scm.c           |  6 ++++++
 security/security.c      | 18 +++++++++++++++---
 7 files changed, 41 insertions(+), 15 deletions(-)

Comments

Stephen Smalley May 18, 2020, 5:02 p.m. UTC | #1
On Thu, May 14, 2020 at 7:25 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
>
> Change the data used in UDS SO_PEERSEC processing from a
> secid to a more general struct lsmblob. Update the
> security_socket_getpeersec_dgram() interface to use the
> lsmblob. There is a small amount of scaffolding code
> that will come out when the security_secid_to_secctx()
> code is brought in line with the lsmblob.
>
> The secid field of the unix_skb_parms structure has been
> replaced with a pointer to an lsmblob structure, and the
> lsmblob is allocated as needed. This is similar to how the
> list of passed files is managed. While an lsmblob structure
> will fit in the available space today, there is no guarantee
> that the addition of other data to the unix_skb_parms or
> support for additional security modules wouldn't exceed what
> is available.

I preferred the previous approach (in v15 and earlier) but I see that
this was suggested by Paul.  Lifecycle management of lsmdata seems
rather tenuous. I guess the real question is what does netdev prefer.
Regardless, you need to check for memory allocation failure below if
this approach stands.

> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> cc: netdev@vger.kernel.org
> ---

> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 3385a7a0b231..a5c1a029095d 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -138,17 +138,18 @@ static struct hlist_head *unix_sockets_unbound(void *addr)
>  #ifdef CONFIG_SECURITY_NETWORK
>  static void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
>  {
> -       UNIXCB(skb).secid = scm->secid;
> +       UNIXCB(skb).lsmdata = kmemdup(&scm->lsmblob, sizeof(scm->lsmblob),
> +                                     GFP_KERNEL);
>  }

Somewhere you need to check for and handle kmemdup() failure here.

>
>  static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
>  {
> -       scm->secid = UNIXCB(skb).secid;
> +       scm->lsmblob = *(UNIXCB(skb).lsmdata);
>  }

Lest we have a bad day here.

>
>  static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
>  {
> -       return (scm->secid == UNIXCB(skb).secid);
> +       return lsmblob_equal(&scm->lsmblob, UNIXCB(skb).lsmdata);
>  }

Or here.

> diff --git a/net/unix/scm.c b/net/unix/scm.c
> index 8c40f2b32392..3094323935a4 100644
> --- a/net/unix/scm.c
> +++ b/net/unix/scm.c
> @@ -142,6 +142,12 @@ void unix_destruct_scm(struct sk_buff *skb)
>         scm.pid  = UNIXCB(skb).pid;
>         if (UNIXCB(skb).fp)
>                 unix_detach_fds(&scm, skb);
> +#ifdef CONFIG_SECURITY_NETWORK
> +       if (UNIXCB(skb).lsmdata) {
> +               kfree(UNIXCB(skb).lsmdata);
> +               UNIXCB(skb).lsmdata = NULL;
> +       }
> +#endif

Does this suffice to ensure that lsmdata is always freed?  Seems
weakly connected to the allocation.

Patch
diff mbox series

diff --git a/include/linux/security.h b/include/linux/security.h
index 453737cefe09..2715b8dd115e 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1357,7 +1357,8 @@  int security_socket_shutdown(struct socket *sock, int how);
 int security_sock_rcv_skb(struct sock *sk, struct sk_buff *skb);
 int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
 				      int __user *optlen, unsigned len);
-int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid);
+int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
+				     struct lsmblob *blob);
 int security_sk_alloc(struct sock *sk, int family, gfp_t priority);
 void security_sk_free(struct sock *sk);
 void security_sk_clone(const struct sock *sk, struct sock *newsk);
@@ -1495,7 +1496,9 @@  static inline int security_socket_getpeersec_stream(struct socket *sock, char __
 	return -ENOPROTOOPT;
 }
 
-static inline int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
+static inline int security_socket_getpeersec_dgram(struct socket *sock,
+						   struct sk_buff *skb,
+						   struct lsmblob *blob)
 {
 	return -ENOPROTOOPT;
 }
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index f42fdddecd41..e99c84677e14 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -36,7 +36,7 @@  struct unix_skb_parms {
 	kgid_t			gid;
 	struct scm_fp_list	*fp;		/* Passed files		*/
 #ifdef CONFIG_SECURITY_NETWORK
-	u32			secid;		/* Security ID		*/
+	struct lsmblob		*lsmdata;	/* Security LSM data	*/
 #endif
 	u32			consumed;
 } __randomize_layout;
diff --git a/include/net/scm.h b/include/net/scm.h
index 1ce365f4c256..e2e71c4bf9d0 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -33,7 +33,7 @@  struct scm_cookie {
 	struct scm_fp_list	*fp;		/* Passed files		*/
 	struct scm_creds	creds;		/* Skb credentials	*/
 #ifdef CONFIG_SECURITY_NETWORK
-	u32			secid;		/* Passed security ID 	*/
+	struct lsmblob		lsmblob;	/* Passed LSM data	*/
 #endif
 };
 
@@ -46,7 +46,7 @@  struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl);
 #ifdef CONFIG_SECURITY_NETWORK
 static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
 {
-	security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
+	security_socket_getpeersec_dgram(sock, NULL, &scm->lsmblob);
 }
 #else
 static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
@@ -97,7 +97,9 @@  static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc
 	int err;
 
 	if (test_bit(SOCK_PASSSEC, &sock->flags)) {
-		err = security_secid_to_secctx(scm->secid, &secdata, &seclen);
+		/* Scaffolding - it has to be element 0 for now */
+		err = security_secid_to_secctx(scm->lsmblob.secid[0],
+					       &secdata, &seclen);
 
 		if (!err) {
 			put_cmsg(msg, SOL_SOCKET, SCM_SECURITY, seclen, secdata);
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index aa3fd61818c4..6cf57d5ac899 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -130,15 +130,17 @@  static void ip_cmsg_recv_checksum(struct msghdr *msg, struct sk_buff *skb,
 
 static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb)
 {
+	struct lsmblob lb;
 	char *secdata;
-	u32 seclen, secid;
+	u32 seclen;
 	int err;
 
-	err = security_socket_getpeersec_dgram(NULL, skb, &secid);
+	err = security_socket_getpeersec_dgram(NULL, skb, &lb);
 	if (err)
 		return;
 
-	err = security_secid_to_secctx(secid, &secdata, &seclen);
+	/* Scaffolding - it has to be element 0 */
+	err = security_secid_to_secctx(lb.secid[0], &secdata, &seclen);
 	if (err)
 		return;
 
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 3385a7a0b231..a5c1a029095d 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -138,17 +138,18 @@  static struct hlist_head *unix_sockets_unbound(void *addr)
 #ifdef CONFIG_SECURITY_NETWORK
 static void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
 {
-	UNIXCB(skb).secid = scm->secid;
+	UNIXCB(skb).lsmdata = kmemdup(&scm->lsmblob, sizeof(scm->lsmblob),
+				      GFP_KERNEL);
 }
 
 static inline void unix_set_secdata(struct scm_cookie *scm, struct sk_buff *skb)
 {
-	scm->secid = UNIXCB(skb).secid;
+	scm->lsmblob = *(UNIXCB(skb).lsmdata);
 }
 
 static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
 {
-	return (scm->secid == UNIXCB(skb).secid);
+	return lsmblob_equal(&scm->lsmblob, UNIXCB(skb).lsmdata);
 }
 #else
 static inline void unix_get_secdata(struct scm_cookie *scm, struct sk_buff *skb)
diff --git a/net/unix/scm.c b/net/unix/scm.c
index 8c40f2b32392..3094323935a4 100644
--- a/net/unix/scm.c
+++ b/net/unix/scm.c
@@ -142,6 +142,12 @@  void unix_destruct_scm(struct sk_buff *skb)
 	scm.pid  = UNIXCB(skb).pid;
 	if (UNIXCB(skb).fp)
 		unix_detach_fds(&scm, skb);
+#ifdef CONFIG_SECURITY_NETWORK
+	if (UNIXCB(skb).lsmdata) {
+		kfree(UNIXCB(skb).lsmdata);
+		UNIXCB(skb).lsmdata = NULL;
+	}
+#endif
 
 	/* Alas, it calls VFS */
 	/* So fscking what? fput() had been SMP-safe since the last Summer */
diff --git a/security/security.c b/security/security.c
index 0a13e98ec6fc..fb003806807b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2159,10 +2159,22 @@  int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
 				optval, optlen, len);
 }
 
-int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb, u32 *secid)
+int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
+				     struct lsmblob *blob)
 {
-	return call_int_hook(socket_getpeersec_dgram, -ENOPROTOOPT, sock,
-			     skb, secid);
+	struct security_hook_list *hp;
+	int rc = -ENOPROTOOPT;
+
+	hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_dgram,
+			     list) {
+		if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot))
+			continue;
+		rc = hp->hook.socket_getpeersec_dgram(sock, skb,
+						&blob->secid[hp->lsmid->slot]);
+		if (rc != 0)
+			break;
+	}
+	return rc;
 }
 EXPORT_SYMBOL(security_socket_getpeersec_dgram);