The getsockopt SO_PEERSEC provides the LSM based security
information for a single module, but for reasons of backward
compatibility cannot include the information for multiple
modules. A new option SO_PEERCONTEXT is added to report the
security "context" of multiple modules using a "compound" format
lsm1\0value\0lsm2\0value\0
This is expected to be used by system services, including dbus-daemon.
The exact format of a compound context has been the subject of
considerable debate. This format was suggested by Simon McVittie,
a dbus maintainer with a significant stake in the format being
usable.
Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
cc: netdev@xxxxxxxxxxxxxxx
cc: linux-api@xxxxxxxxxxxxxxx
---
Documentation/security/lsm.rst | 15 ++++
arch/alpha/include/uapi/asm/socket.h | 1 +
arch/mips/include/uapi/asm/socket.h | 1 +
arch/parisc/include/uapi/asm/socket.h | 1 +
arch/sparc/include/uapi/asm/socket.h | 1 +
include/linux/lsm_hooks.h | 9 +-
include/linux/security.h | 10 ++-
include/uapi/asm-generic/socket.h | 1 +
net/core/sock.c | 7 +-
security/apparmor/lsm.c | 20 ++---
security/security.c | 115 +++++++++++++++++++++++---
security/selinux/hooks.c | 20 ++---
security/smack/smack_lsm.c | 31 +++----
13 files changed, 170 insertions(+), 62 deletions(-)
diff --git a/Documentation/security/lsm.rst b/Documentation/security/lsm.rst
index aadf47c808c0..77cc326a52cc 100644
--- a/Documentation/security/lsm.rst
+++ b/Documentation/security/lsm.rst
@@ -199,3 +199,18 @@ capability-related fields:
- ``fs/nfsd/auth.c``::c:func:`nfsd_setuser()`
- ``fs/proc/array.c``::c:func:`task_cap()`
+
+LSM External Interfaces
+=======================
+
+The LSM infrastructure does not generally provide external interfaces.
+The individual security modules provide what external interfaces they
+require. The infrastructure does provide two interfaces for the special
+case where multiple security modules provide a process context. This
+is provided in compound context format.
+
+- `lsm1\0value\0lsm2\0value\0`
+
+The special file ``/proc/pid/attr/context`` provides the security
+context of the identified process. The socket option SO_PEERCONTEXT
+provides the security context of a packet.
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index de6c4df61082..b26fb34e4226 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -123,6 +123,7 @@
#define SO_SNDTIMEO_NEW 67
#define SO_DETACH_REUSEPORT_BPF 68
+#define SO_PEERCONTEXT 69
#if !defined(__KERNEL__)
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index d0a9ed2ca2d6..10e03507b1ed 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -134,6 +134,7 @@
#define SO_SNDTIMEO_NEW 67
#define SO_DETACH_REUSEPORT_BPF 68
+#define SO_PEERCONTEXT 69
#if !defined(__KERNEL__)
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index 10173c32195e..e11df59a84d1 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -115,6 +115,7 @@
#define SO_SNDTIMEO_NEW 0x4041
#define SO_DETACH_REUSEPORT_BPF 0x4042
+#define SO_PEERCONTEXT 0x4043
#if !defined(__KERNEL__)
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index 8029b681fc7c..5b41ef778040 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -116,6 +116,7 @@
#define SO_SNDTIMEO_NEW 0x0045
#define SO_DETACH_REUSEPORT_BPF 0x0047
+#define SO_PEERCONTEXT 0x0048
#if !defined(__KERNEL__)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 2bf82e1cf347..2ae10e7f81a7 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -880,8 +880,8 @@
* SO_GETPEERSEC. For tcp sockets this can be meaningful if the
* socket is associated with an ipsec SA.
* @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
+ * @optval memory where the security state is to be copied.
+ * @optlen 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.
@@ -1724,9 +1724,8 @@ union security_list_options {
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_stream)(struct socket *sock,
- char __user *optval,
- int __user *optlen, unsigned len);
+ int (*socket_getpeersec_stream)(struct socket *sock, char **optval,
+ int *optlen, unsigned len);
int (*socket_getpeersec_dgram)(struct socket *sock,
struct sk_buff *skb, u32 *secid);
int (*sk_alloc_security)(struct sock *sk, int family, gfp_t priority);
diff --git a/include/linux/security.h b/include/linux/security.h
index d7af2bbbc878..26967055a002 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -178,6 +178,7 @@ struct lsmblob {
#define LSMBLOB_NOT_NEEDED -3 /* Slot not requested */
#define LSMBLOB_DISPLAY -4 /* Use the "display" slot */
#define LSMBLOB_FIRST -5 /* Use the default "display" slot */
+#define LSMBLOB_COMPOUND -6 /* A compound "display" */
/**
* lsmblob_init - initialize an lsmblob structure.
@@ -1396,7 +1397,8 @@ int security_socket_setsockopt(struct socket *sock, int level, int optname);
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 __user *optlen, unsigned len,
+ int display);
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);
@@ -1530,8 +1532,10 @@ static inline int security_sock_rcv_skb(struct sock *sk,
return 0;
}
-static inline int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
- int __user *optlen, unsigned len)
+static inline int security_socket_getpeersec_stream(struct socket *sock,
+ char __user *optval,
+ int __user *optlen,
+ unsigned len, int display)
{
return -ENOPROTOOPT;
}
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 77f7c1638eb1..e3a853d53705 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -118,6 +118,7 @@
#define SO_SNDTIMEO_NEW 67
#define SO_DETACH_REUSEPORT_BPF 68
+#define SO_PEERCONTEXT 69
#if !defined(__KERNEL__)
diff --git a/net/core/sock.c b/net/core/sock.c
index 043db3ce023e..63b7eda81a90 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1411,7 +1411,12 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
break;
case SO_PEERSEC:
- return security_socket_getpeersec_stream(sock, optval, optlen, len);
+ return security_socket_getpeersec_stream(sock, optval, optlen,
+ len, LSMBLOB_DISPLAY);
+
+ case SO_PEERCONTEXT:
+ return security_socket_getpeersec_stream(sock, optval, optlen,
+ len, LSMBLOB_COMPOUND);
case SO_MARK:
v.val = sk->sk_mark;
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 16b992235c11..34edfd29c32f 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -1078,10 +1078,8 @@ static struct aa_label *sk_peer_label(struct sock *sk)
*
* Note: for tcp only valid if using ipsec or cipso on lan
*/
-static int apparmor_socket_getpeersec_stream(struct socket *sock,
- char __user *optval,
- int __user *optlen,
- unsigned int len)
+static int apparmor_socket_getpeersec_stream(struct socket *sock, char **optval,
+ int *optlen, unsigned int len)
{
char *name;
int slen, error = 0;
@@ -1101,17 +1099,11 @@ static int apparmor_socket_getpeersec_stream(struct socket *sock,
if (slen < 0) {
error = -ENOMEM;
} else {
- if (slen > len) {
+ if (slen > len)
error = -ERANGE;
- } else if (copy_to_user(optval, name, slen)) {
- error = -EFAULT;
- goto out;
- }
- if (put_user(slen, optlen))
- error = -EFAULT;
-out:
- kfree(name);
-
+ else
+ *optval = name;
+ *optlen = slen;
}
done:
diff --git a/security/security.c b/security/security.c
index 6d05222aac9c..80539dfd0245 100644
--- a/security/security.c
+++ b/security/security.c
@@ -723,6 +723,42 @@ static void __init lsm_early_task(struct task_struct *task)
panic("%s: Early task alloc failed.\n", __func__);
}
+/**
+ * append_ctx - append a lsm/context pair to a compound context
+ * @ctx: the existing compound context
+ * @ctxlen: size of the old context, including terminating nul byte
+ * @lsm: new lsm name, nul terminated
+ * @new: new context, possibly nul terminated
+ * @newlen: maximum size of @new
+ *
+ * replace @ctx with a new compound context, appending @newlsm and @new
+ * to @ctx. On exit the new data replaces the old, which is freed.
+ * @ctxlen is set to the new size, which includes a trailing nul byte.
+ *
+ * Returns 0 on success, -ENOMEM if no memory is available.
+ */
+static int append_ctx(char **ctx, int *ctxlen, const char *lsm, char *new,
+ int newlen)
+{
+ char *final;
+ int llen;
+
+ llen = strlen(lsm) + 1;
+ newlen = strnlen(new, newlen) + 1;
+
+ final = kzalloc(*ctxlen + llen + newlen, GFP_KERNEL);
+ if (final == NULL)
+ return -ENOMEM;
+ if (*ctxlen)
+ memcpy(final, *ctx, *ctxlen);
+ memcpy(final + *ctxlen, lsm, llen);
+ memcpy(final + *ctxlen + llen, new, newlen);
+ kfree(*ctx);
+ *ctx = final;
+ *ctxlen = *ctxlen + llen + newlen;
+ return 0;
+}
+
/*
* Hook list operation macros.
*
@@ -2164,8 +2200,8 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm))
continue;
- if (lsm == NULL && *display != LSMBLOB_INVALID &&
- *display != hp->lsmid->slot)
+ if (lsm == NULL && display != NULL &&
+ *display != LSMBLOB_INVALID && *display != hp->lsmid->slot)
continue;
return hp->hook.setprocattr(name, value, size);
}
@@ -2245,12 +2281,21 @@ void security_release_secctx(struct lsmcontext *cp)
{
struct security_hook_list *hp;
+ if (cp->slot == LSMBLOB_INVALID)
+ return;
+
+ if (cp->slot == LSMBLOB_COMPOUND) {
+ kfree(cp->context);
+ goto clear_out;
+ }
+
hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list)
if (cp->slot == hp->lsmid->slot) {
hp->hook.release_secctx(cp->context, cp->len);
break;
}
+clear_out:
memset(cp, 0, sizeof(*cp));
}
EXPORT_SYMBOL(security_release_secctx);
@@ -2383,17 +2428,67 @@ int security_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
EXPORT_SYMBOL(security_sock_rcv_skb);
int security_socket_getpeersec_stream(struct socket *sock, char __user *optval,
- int __user *optlen, unsigned len)
+ int __user *optlen, unsigned len,
+ int display)
{
- int display = lsm_task_display(current);
struct security_hook_list *hp;
+ char *final = NULL;
+ char *cp;
+ int rc = 0;
+ unsigned finallen = 0;
+ unsigned clen = 0;
- hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_stream,
- list)
- if (display == LSMBLOB_INVALID || display == hp->lsmid->slot)
- return hp->hook.socket_getpeersec_stream(sock, optval,
- optlen, len);
- return -ENOPROTOOPT;
+ switch (display) {
+ case LSMBLOB_DISPLAY:
+ rc = -ENOPROTOOPT;
+ display = lsm_task_display(current);
+ hlist_for_each_entry(hp,
+ &security_hook_heads.socket_getpeersec_stream,
+ list)
+ if (display == LSMBLOB_INVALID ||
+ display == hp->lsmid->slot) {
+ rc = hp->hook.socket_getpeersec_stream(sock,
+ &final, &finallen, len);
+ break;
+ }
+ break;
+ case LSMBLOB_COMPOUND:
+ /*
+ * A compound context, in the form [lsm\0value\0]...
+ */
+ hlist_for_each_entry(hp,
+ &security_hook_heads.socket_getpeersec_stream,
+ list) {
+ rc = hp->hook.socket_getpeersec_stream(sock, &cp, &clen,
+ len);
+ if (rc == -EINVAL || rc == -ENOPROTOOPT) {
+ rc = 0;
+ continue;
+ }
+ if (rc) {
+ kfree(final);
+ return rc;
+ }
+ rc = append_ctx(&final, &finallen, hp->lsmid->lsm,
+ cp, clen);
+ }
+ if (final == NULL)
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (finallen > len)
+ rc = -ERANGE;
+ else if (copy_to_user(optval, final, finallen))
+ rc = -EFAULT;
+
+ if (put_user(finallen, optlen))
+ rc = -EFAULT;
+
+ kfree(final);
+ return rc;
}
int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *skb,
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index cd4743331800..c3e6fd3f8c56 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5056,10 +5056,8 @@ static int selinux_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
return err;
}
-static int selinux_socket_getpeersec_stream(struct socket *sock,
- char __user *optval,
- int __user *optlen,
- unsigned int len)
+static int selinux_socket_getpeersec_stream(struct socket *sock, char **optval,
+ int *optlen, unsigned int len)
{
int err = 0;
char *scontext;
@@ -5079,18 +5077,12 @@ static int selinux_socket_getpeersec_stream(struct socket *sock,
if (err)
return err;
- if (scontext_len > len) {
+ if (scontext_len > len)
err = -ERANGE;
- goto out_len;
- }
-
- if (copy_to_user(optval, scontext, scontext_len))
- err = -EFAULT;
+ else
+ *optval = scontext;
-out_len:
- if (put_user(scontext_len, optlen))
- err = -EFAULT;
- kfree(scontext);
+ *optlen = scontext_len;
return err;
}
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 9ce67e03ac49..316c5faf9053 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3957,28 +3957,29 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
*
* returns zero on success, an error code otherwise
*/
-static int smack_socket_getpeersec_stream(struct socket *sock,
- char __user *optval,
- int __user *optlen, unsigned len)
+static int smack_socket_getpeersec_stream(struct socket *sock, char **optval,
+ int *optlen, unsigned len)
{
- struct socket_smack *ssp;
- char *rcp = "";
- int slen = 1;
+ struct socket_smack *ssp = smack_sock(sock->sk);
+ char *rcp;
+ int slen;
int rc = 0;
- ssp = smack_sock(sock->sk);
- if (ssp->smk_packet != NULL) {
- rcp = ssp->smk_packet->smk_known;
- slen = strlen(rcp) + 1;
+ if (ssp->smk_packet == NULL) {
+ *optlen = 0;
+ return -EINVAL;
}
+ rcp = ssp->smk_packet->smk_known;
+ slen = strlen(rcp) + 1;
if (slen > len)
rc = -ERANGE;
- else if (copy_to_user(optval, rcp, slen) != 0)
- rc = -EFAULT;
-
- if (put_user(slen, optlen) != 0)
- rc = -EFAULT;
+ else {
+ *optval = kstrdup(rcp, GFP_KERNEL);
+ if (*optval == NULL)
+ rc = -ENOMEM;
+ }
+ *optlen = slen;
return rc;
}
--
2.20.1
