[PATCH 2/3] Security: Implement prctl(PR_SET_NETWORK, PR_NETWORK_OFF) semantics. (v2)

Michael Stone
2009-12-18T03:29:32Z

Return -EPERM any time we try to __sock_create(), sys_connect(), sys_bind(),
sys_sendmsg(), or __ptrace_may_access() from a process with PR_NETWORK_OFF set
in current->network unless we're working on a socket which is already connected
or on a non-abstract AF_UNIX socket.

Signed-off-by: Michael Stone <michael@laptop.org>
---
kernel/fork.c | 2 ++
kernel/ptrace.c | 3 +++
kernel/sys.c | 2 +-
net/socket.c | 51 ++++++++++++++++++++++++++++++++++++++-------------
net/unix/af_unix.c | 19 +++++++++++++++++++
5 files changed, 63 insertions(+), 14 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 9bd9144..01a7644 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1130,6 +1130,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,

p->bts = NULL;

+ p->network = current->network;
+
p->stack_start = stack_start;

/* Perform scheduler related setup. Assign this task to a CPU. */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 23bd09c..bcf87ba 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -151,6 +151,9 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
dumpable = get_dumpable(task->mm);
if (!dumpable && !capable(CAP_SYS_PTRACE))
return -EPERM;
+ /* does current have networking restrictions not shared by task? */
+ if (current->network & ~task->network)
+ return -EPERM;

return security_ptrace_access_check(task, mode);
}
diff --git a/kernel/sys.c b/kernel/sys.c
index 411a2ff..481fa9c 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1601,7 +1601,7 @@ long prctl_set_network(unsigned long network_flags)

/* only dropping access is permitted */
ret = -EPERM;
- if (current->network & ~network_flags)
+ if (current->network & ~network_flags)
goto out;

ret = -EINVAL;
diff --git a/net/socket.c b/net/socket.c
index b94c3dd..e59f906 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -87,6 +87,7 @@
#include <linux/wireless.h>
#include <linux/nsproxy.h>
#include <linux/magic.h>
+#include <linux/sched.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -576,6 +577,12 @@ static inline int __sock_sendmsg(struct kiocb *iocb, struct socket *sock,
if (err)
return err;

+ err = -EPERM;
+ if (sock->sk->sk_family != AF_UNIX &&
+ current->network &&
+ (msg->msg_name != NULL || msg->msg_namelen != 0))
+ return err;
+
return sock->ops->sendmsg(iocb, sock, msg, size);
}

@@ -1227,6 +1234,9 @@ static int __sock_create(struct net *net, int family, int type, int protocol,
if (err)
return err;

+ if (family != AF_UNIX && current->network)
+ return -EPERM;
+
/*
* Allocate the socket and allow the family to set things up. if
* the protocol is 0, the family is instructed to select an appropriate
@@ -1465,19 +1475,29 @@ SYSCALL_DEFINE3(bind, int, fd, struct sockaddr __user *, umyaddr, int, addrlen)
int err, fput_needed;

sock = sockfd_lookup_light(fd, &err, &fput_needed);
- if (sock) {
- err = move_addr_to_kernel(umyaddr, addrlen, (struct sockaddr *)&address);
- if (err >= 0) {
- err = security_socket_bind(sock,
- (struct sockaddr *)&address,
- addrlen);
- if (!err)
- err = sock->ops->bind(sock,
- (struct sockaddr *)
- &address, addrlen);
- }
- fput_light(sock->file, fput_needed);
- }
+ if (!sock)
+ goto out;
+
+ err = move_addr_to_kernel(umyaddr, addrlen, (struct sockaddr *)&address);
+ if (err < 0)
+ goto out_fput;
+
+ err = security_socket_bind(sock,
+ (struct sockaddr *)&address,
+ addrlen);
+ if (err)
+ goto out_fput;
+
+ err = (((struct sockaddr *)&address)->sa_family != AF_UNIX &&
+ current->network) ? -EPERM : 0;
+ if (err)
+ goto out_fput;
+
+ err = sock->ops->bind(sock, (struct sockaddr *) &address, addrlen);
+
+out_fput:
+ fput_light(sock->file, fput_needed);
+out:
return err;
}

@@ -1639,6 +1659,11 @@ SYSCALL_DEFINE3(connect, int, fd, struct sockaddr __user *, uservaddr,
if (err)
goto out_put;

+ err = (((struct sockaddr *)&address)->sa_family != AF_UNIX &&
+ current->network) ? -EPERM : 0;
+ if (err)
+ goto out_put;
+
err = sock->ops->connect(sock, (struct sockaddr *)&address, addrlen,
sock->file->f_flags);
out_put:
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f255119..5087ae3 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -797,6 +797,10 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
goto out;
addr_len = err;

+ err = (current->network && !sunaddr->sun_path[0]) ? -EPERM : 0;
+ if (err)
+ goto out;
+
mutex_lock(&u->readlock);

err = -EINVAL;
@@ -934,6 +938,10 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
goto out;
alen = err;

+ err = (current->network && !sunaddr->sun_path[0]) ? -EPERM : 0;
+ if (err)
+ goto out;
+
if (test_bit(SOCK_PASSCRED, &sock->flags) &&
!unix_sk(sk)->addr && (err = unix_autobind(sock)) != 0)
goto out;
@@ -1033,6 +1041,10 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
goto out;
addr_len = err;

+ err = (current->network && !sunaddr->sun_path[0]) ? -EPERM : 0;
+ if (err)
+ goto out;
+
if (test_bit(SOCK_PASSCRED, &sock->flags) && !u->addr &&
(err = unix_autobind(sock)) != 0)
goto out;
@@ -1370,6 +1382,10 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (err < 0)
goto out;
namelen = err;
+
+ err = -EPERM;
+ if (current->network && !sunaddr->sun_path[0])
+ goto out;
} else {
sunaddr = NULL;
err = -ENOTCONN;
@@ -1520,6 +1536,9 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (msg->msg_namelen) {
err = sk->sk_state == TCP_ESTABLISHED ? -EISCONN : -EOPNOTSUPP;
goto out_err;
+ /* prctl(PR_SET_NETWORK) requires no change here since
+ * connection-less unix stream sockets are not supported.
+ * See Documentation/prctl/network.txt for details. */
} else {
sunaddr = NULL;
err = -ENOTCONN;
--
1.6.6.rc1