* [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start
@ 2021-01-26 16:51 Stanislav Fomichev
2021-01-26 16:51 ` [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works Stanislav Fomichev
2021-01-26 18:01 ` [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Martin KaFai Lau
0 siblings, 2 replies; 6+ messages in thread
From: Stanislav Fomichev @ 2021-01-26 16:51 UTC (permalink / raw)
To: netdev, bpf
Cc: ast, daniel, Stanislav Fomichev, Andrey Ignatov, Martin KaFai Lau
At the moment, BPF_CGROUP_INET{4,6}_BIND hooks can rewrite user_port
to the privileged ones (< ip_unprivileged_port_start), but it will
be rejected later on in the __inet_bind or __inet6_bind.
Let's add another return value to indicate that CAP_NET_BIND_SERVICE
check should be ignored. Use the same idea as we currently use
in cgroup/egress where bit #1 indicates CN. Instead, for
cgroup/bind{4,6}, bit #1 indicates that CAP_NET_BIND_SERVICE should
be bypassed.
v3:
- Update description (Martin KaFai Lau)
- Fix capability restore in selftest (Martin KaFai Lau)
v2:
- Switch to explicit return code (Martin KaFai Lau)
Cc: Andrey Ignatov <rdna@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
include/linux/bpf-cgroup.h | 38 ++++++++++++++++++++++++---------
include/linux/bpf.h | 43 ++++++++++++++++++++++----------------
include/net/inet_common.h | 3 +++
kernel/bpf/cgroup.c | 8 +++++--
kernel/bpf/verifier.c | 3 +++
net/ipv4/af_inet.c | 9 +++++---
net/ipv6/af_inet6.c | 6 ++++--
7 files changed, 75 insertions(+), 35 deletions(-)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 0748fd87969e..6232745bae9b 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -125,7 +125,8 @@ int __cgroup_bpf_run_filter_sk(struct sock *sk,
int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
struct sockaddr *uaddr,
enum bpf_attach_type type,
- void *t_ctx);
+ void *t_ctx,
+ u32 *flags);
int __cgroup_bpf_run_filter_sock_ops(struct sock *sk,
struct bpf_sock_ops_kern *sock_ops,
@@ -231,30 +232,48 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
#define BPF_CGROUP_RUN_SA_PROG(sk, uaddr, type) \
({ \
+ u32 __unused_flags; \
int __ret = 0; \
if (cgroup_bpf_enabled(type)) \
__ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, type, \
- NULL); \
+ NULL, \
+ &__unused_flags); \
__ret; \
})
#define BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, type, t_ctx) \
({ \
+ u32 __unused_flags; \
int __ret = 0; \
if (cgroup_bpf_enabled(type)) { \
lock_sock(sk); \
__ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, type, \
- t_ctx); \
+ t_ctx, \
+ &__unused_flags); \
release_sock(sk); \
} \
__ret; \
})
-#define BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr) \
- BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, BPF_CGROUP_INET4_BIND, NULL)
-
-#define BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr) \
- BPF_CGROUP_RUN_SA_PROG_LOCK(sk, uaddr, BPF_CGROUP_INET6_BIND, NULL)
+/* BPF_CGROUP_INET4_BIND and BPF_CGROUP_INET6_BIND can return extra flags
+ * via upper bits of return code. The only flag that is supported
+ * (at bit position 0) is to indicate CAP_NET_BIND_SERVICE capability check
+ * should be bypassed.
+ */
+#define BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr, type, flags) \
+({ \
+ u32 __flags = 0; \
+ int __ret = 0; \
+ if (cgroup_bpf_enabled(type)) { \
+ lock_sock(sk); \
+ __ret = __cgroup_bpf_run_filter_sock_addr(sk, uaddr, type, \
+ NULL, &__flags); \
+ release_sock(sk); \
+ if (__flags & 1) \
+ *flags |= BIND_NO_CAP_NET_BIND_SERVICE; \
+ } \
+ __ret; \
+})
#define BPF_CGROUP_PRE_CONNECT_ENABLED(sk) \
((cgroup_bpf_enabled(BPF_CGROUP_INET4_CONNECT) || \
@@ -453,8 +472,7 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map,
#define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET_SOCK(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET_SOCK_RELEASE(sk) ({ 0; })
-#define BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr) ({ 0; })
-#define BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr) ({ 0; })
+#define BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr, type, flags) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET6_POST_BIND(sk) ({ 0; })
#define BPF_CGROUP_RUN_PROG_INET4_CONNECT(sk, uaddr) ({ 0; })
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1aac2af12fed..08eee284d251 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1073,6 +1073,29 @@ int bpf_prog_array_copy(struct bpf_prog_array *old_array,
struct bpf_prog *include_prog,
struct bpf_prog_array **new_array);
+#define BPF_PROG_RUN_ARRAY_FLAGS(array, ctx, func, flags) \
+ ({ \
+ struct bpf_prog_array_item *_item; \
+ struct bpf_prog *_prog; \
+ struct bpf_prog_array *_array; \
+ u32 _ret = 1; \
+ u32 ret; \
+ migrate_disable(); \
+ rcu_read_lock(); \
+ _array = rcu_dereference(array); \
+ _item = &_array->items[0]; \
+ while ((_prog = READ_ONCE(_item->prog))) { \
+ bpf_cgroup_storage_set(_item->cgroup_storage); \
+ ret = func(_prog, ctx); \
+ _ret &= (ret & 1); \
+ *(flags) |= (ret >> 1); \
+ _item++; \
+ } \
+ rcu_read_unlock(); \
+ migrate_enable(); \
+ _ret; \
+ })
+
#define __BPF_PROG_RUN_ARRAY(array, ctx, func, check_non_null) \
({ \
struct bpf_prog_array_item *_item; \
@@ -1120,25 +1143,9 @@ _out: \
*/
#define BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY(array, ctx, func) \
({ \
- struct bpf_prog_array_item *_item; \
- struct bpf_prog *_prog; \
- struct bpf_prog_array *_array; \
- u32 ret; \
- u32 _ret = 1; \
u32 _cn = 0; \
- migrate_disable(); \
- rcu_read_lock(); \
- _array = rcu_dereference(array); \
- _item = &_array->items[0]; \
- while ((_prog = READ_ONCE(_item->prog))) { \
- bpf_cgroup_storage_set(_item->cgroup_storage); \
- ret = func(_prog, ctx); \
- _ret &= (ret & 1); \
- _cn |= (ret & 2); \
- _item++; \
- } \
- rcu_read_unlock(); \
- migrate_enable(); \
+ u32 _ret; \
+ _ret = BPF_PROG_RUN_ARRAY_FLAGS(array, ctx, func, &_cn); \
if (_ret) \
_ret = (_cn ? NET_XMIT_CN : NET_XMIT_SUCCESS); \
else \
diff --git a/include/net/inet_common.h b/include/net/inet_common.h
index cb2818862919..9ba935c15869 100644
--- a/include/net/inet_common.h
+++ b/include/net/inet_common.h
@@ -41,6 +41,9 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len);
#define BIND_WITH_LOCK (1 << 1)
/* Called from BPF program. */
#define BIND_FROM_BPF (1 << 2)
+/* Skip CAP_NET_BIND_SERVICE check. */
+#define BIND_NO_CAP_NET_BIND_SERVICE (1 << 3)
+
int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
u32 flags);
int inet_getname(struct socket *sock, struct sockaddr *uaddr,
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index da649f20d6b2..cdf3c7e611d9 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -1055,6 +1055,8 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
* @uaddr: sockaddr struct provided by user
* @type: The type of program to be exectuted
* @t_ctx: Pointer to attach type specific context
+ * @flags: Pointer to u32 which contains higher bits of BPF program
+ * return value (OR'ed together).
*
* socket is expected to be of type INET or INET6.
*
@@ -1064,7 +1066,8 @@ EXPORT_SYMBOL(__cgroup_bpf_run_filter_sk);
int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
struct sockaddr *uaddr,
enum bpf_attach_type type,
- void *t_ctx)
+ void *t_ctx,
+ u32 *flags)
{
struct bpf_sock_addr_kern ctx = {
.sk = sk,
@@ -1087,7 +1090,8 @@ int __cgroup_bpf_run_filter_sock_addr(struct sock *sk,
}
cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
- ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], &ctx, BPF_PROG_RUN);
+ ret = BPF_PROG_RUN_ARRAY_FLAGS(cgrp->bpf.effective[type], &ctx,
+ BPF_PROG_RUN, flags);
return ret == 1 ? 0 : -EPERM;
}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d0eae51b31e4..972fc38eb62d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7986,6 +7986,9 @@ static int check_return_code(struct bpf_verifier_env *env)
env->prog->expected_attach_type == BPF_CGROUP_INET4_GETSOCKNAME ||
env->prog->expected_attach_type == BPF_CGROUP_INET6_GETSOCKNAME)
range = tnum_range(1, 1);
+ if (env->prog->expected_attach_type == BPF_CGROUP_INET4_BIND ||
+ env->prog->expected_attach_type == BPF_CGROUP_INET6_BIND)
+ range = tnum_range(0, 3);
break;
case BPF_PROG_TYPE_CGROUP_SKB:
if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 6ba2930ff49b..aaa94bea19c3 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -438,6 +438,7 @@ EXPORT_SYMBOL(inet_release);
int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sock *sk = sock->sk;
+ u32 flags = BIND_WITH_LOCK;
int err;
/* If the socket has its own bind function then use it. (RAW) */
@@ -450,11 +451,12 @@ int inet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
/* BPF prog is run before any checks are done so that if the prog
* changes context in a wrong way it will be caught.
*/
- err = BPF_CGROUP_RUN_PROG_INET4_BIND_LOCK(sk, uaddr);
+ err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
+ BPF_CGROUP_INET4_BIND, &flags);
if (err)
return err;
- return __inet_bind(sk, uaddr, addr_len, BIND_WITH_LOCK);
+ return __inet_bind(sk, uaddr, addr_len, flags);
}
EXPORT_SYMBOL(inet_bind);
@@ -499,7 +501,8 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
snum = ntohs(addr->sin_port);
err = -EACCES;
- if (snum && inet_port_requires_bind_service(net, snum) &&
+ if (!(flags & BIND_NO_CAP_NET_BIND_SERVICE) &&
+ snum && inet_port_requires_bind_service(net, snum) &&
!ns_capable(net->user_ns, CAP_NET_BIND_SERVICE))
goto out;
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index b9c654836b72..3e523c4f5226 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -439,6 +439,7 @@ static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
struct sock *sk = sock->sk;
+ u32 flags = BIND_WITH_LOCK;
int err = 0;
/* If the socket has its own bind function then use it. */
@@ -451,11 +452,12 @@ int inet6_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
/* BPF prog is run before any checks are done so that if the prog
* changes context in a wrong way it will be caught.
*/
- err = BPF_CGROUP_RUN_PROG_INET6_BIND_LOCK(sk, uaddr);
+ err = BPF_CGROUP_RUN_PROG_INET_BIND_LOCK(sk, uaddr,
+ BPF_CGROUP_INET6_BIND, &flags);
if (err)
return err;
- return __inet6_bind(sk, uaddr, addr_len, BIND_WITH_LOCK);
+ return __inet6_bind(sk, uaddr, addr_len, flags);
}
EXPORT_SYMBOL(inet6_bind);
--
2.30.0.280.ga3ce27912f-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works
2021-01-26 16:51 [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Stanislav Fomichev
@ 2021-01-26 16:51 ` Stanislav Fomichev
2021-01-26 18:18 ` Martin KaFai Lau
2021-01-26 18:01 ` [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Martin KaFai Lau
1 sibling, 1 reply; 6+ messages in thread
From: Stanislav Fomichev @ 2021-01-26 16:51 UTC (permalink / raw)
To: netdev, bpf
Cc: ast, daniel, Stanislav Fomichev, Andrey Ignatov, Martin KaFai Lau
Return 3 to indicate that permission check for port 111
should be skipped.
Cc: Andrey Ignatov <rdna@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
.../selftests/bpf/prog_tests/bind_perm.c | 80 +++++++++++++++++++
tools/testing/selftests/bpf/progs/bind_perm.c | 36 +++++++++
2 files changed, 116 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/bind_perm.c
create mode 100644 tools/testing/selftests/bpf/progs/bind_perm.c
diff --git a/tools/testing/selftests/bpf/prog_tests/bind_perm.c b/tools/testing/selftests/bpf/prog_tests/bind_perm.c
new file mode 100644
index 000000000000..763de148e511
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bind_perm.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "bind_perm.skel.h"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/capability.h>
+
+static int duration;
+
+void try_bind(int port, int expected_errno)
+{
+ struct sockaddr_in sin = {};
+ int fd = -1;
+
+ fd = socket(AF_INET, SOCK_STREAM, 0);
+ if (CHECK(fd < 0, "fd", "errno %d", errno))
+ goto close_socket;
+
+ sin.sin_family = AF_INET;
+ sin.sin_port = htons(port);
+
+ errno = 0;
+ bind(fd, (struct sockaddr *)&sin, sizeof(sin));
+ ASSERT_EQ(errno, expected_errno, "bind");
+
+close_socket:
+ if (fd >= 0)
+ close(fd);
+}
+
+void cap_net_bind_service(cap_flag_value_t flag)
+{
+ const cap_value_t cap_net_bind_service = CAP_NET_BIND_SERVICE;
+ cap_t caps;
+
+ caps = cap_get_proc();
+ if (CHECK(!caps, "cap_get_proc", "errno %d", errno))
+ goto free_caps;
+
+ if (CHECK(cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_net_bind_service,
+ flag),
+ "cap_set_flag", "errno %d", errno))
+ goto free_caps;
+
+ if (CHECK(cap_set_proc(caps), "cap_set_proc", "errno %d", errno))
+ goto free_caps;
+
+free_caps:
+ if (CHECK(cap_free(caps), "cap_free", "errno %d", errno))
+ goto free_caps;
+}
+
+void test_bind_perm(void)
+{
+ struct bind_perm *skel;
+ int cgroup_fd;
+
+ cgroup_fd = test__join_cgroup("/bind_perm");
+ if (CHECK(cgroup_fd < 0, "cg-join", "errno %d", errno))
+ return;
+
+ skel = bind_perm__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel"))
+ goto close_cgroup_fd;
+
+ skel->links.bind_v4_prog = bpf_program__attach_cgroup(skel->progs.bind_v4_prog, cgroup_fd);
+ if (!ASSERT_OK_PTR(skel, "bind_v4_prog"))
+ goto close_skeleton;
+
+ cap_net_bind_service(CAP_CLEAR);
+ try_bind(110, EACCES);
+ try_bind(111, 0);
+ cap_net_bind_service(CAP_SET);
+
+close_skeleton:
+ bind_perm__destroy(skel);
+close_cgroup_fd:
+ close(cgroup_fd);
+}
diff --git a/tools/testing/selftests/bpf/progs/bind_perm.c b/tools/testing/selftests/bpf/progs/bind_perm.c
new file mode 100644
index 000000000000..e89bd264ed26
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bind_perm.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+SEC("cgroup/bind4")
+int bind_v4_prog(struct bpf_sock_addr *ctx)
+{
+ struct bpf_sock *sk;
+ __u32 user_ip4;
+ __u16 user_port;
+
+ sk = ctx->sk;
+ if (!sk)
+ return 0;
+
+ if (sk->family != AF_INET)
+ return 0;
+
+ if (ctx->type != SOCK_STREAM)
+ return 0;
+
+ /* Return 1 OR'ed with the first bit set to indicate
+ * that CAP_NET_BIND_SERVICE should be bypassed.
+ */
+ if (ctx->user_port == bpf_htons(111))
+ return (1 | 2);
+
+ return 1;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.30.0.280.ga3ce27912f-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start
2021-01-26 16:51 [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Stanislav Fomichev
2021-01-26 16:51 ` [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works Stanislav Fomichev
@ 2021-01-26 18:01 ` Martin KaFai Lau
2021-01-26 18:05 ` Stanislav Fomichev
1 sibling, 1 reply; 6+ messages in thread
From: Martin KaFai Lau @ 2021-01-26 18:01 UTC (permalink / raw)
To: Stanislav Fomichev; +Cc: netdev, bpf, ast, daniel, Andrey Ignatov
On Tue, Jan 26, 2021 at 08:51:03AM -0800, Stanislav Fomichev wrote:
> At the moment, BPF_CGROUP_INET{4,6}_BIND hooks can rewrite user_port
> to the privileged ones (< ip_unprivileged_port_start), but it will
> be rejected later on in the __inet_bind or __inet6_bind.
>
> Let's add another return value to indicate that CAP_NET_BIND_SERVICE
> check should be ignored. Use the same idea as we currently use
> in cgroup/egress where bit #1 indicates CN. Instead, for
> cgroup/bind{4,6}, bit #1 indicates that CAP_NET_BIND_SERVICE should
> be bypassed.
>
> v3:
> - Update description (Martin KaFai Lau)
> - Fix capability restore in selftest (Martin KaFai Lau)
>
> v2:
> - Switch to explicit return code (Martin KaFai Lau)
>
[ ... ]
> @@ -499,7 +501,8 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
>
> snum = ntohs(addr->sin_port);
> err = -EACCES;
> - if (snum && inet_port_requires_bind_service(net, snum) &&
> + if (!(flags & BIND_NO_CAP_NET_BIND_SERVICE) &&
> + snum && inet_port_requires_bind_service(net, snum) &&
The same change needs to be done on __inet6_bind()
and also adds a test for IPv6 in patch 2.
> !ns_capable(net->user_ns, CAP_NET_BIND_SERVICE))
> goto out;
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start
2021-01-26 18:01 ` [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Martin KaFai Lau
@ 2021-01-26 18:05 ` Stanislav Fomichev
0 siblings, 0 replies; 6+ messages in thread
From: Stanislav Fomichev @ 2021-01-26 18:05 UTC (permalink / raw)
To: Martin KaFai Lau
Cc: Netdev, bpf, Alexei Starovoitov, Daniel Borkmann, Andrey Ignatov
On Tue, Jan 26, 2021 at 10:01 AM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Tue, Jan 26, 2021 at 08:51:03AM -0800, Stanislav Fomichev wrote:
> > At the moment, BPF_CGROUP_INET{4,6}_BIND hooks can rewrite user_port
> > to the privileged ones (< ip_unprivileged_port_start), but it will
> > be rejected later on in the __inet_bind or __inet6_bind.
> >
> > Let's add another return value to indicate that CAP_NET_BIND_SERVICE
> > check should be ignored. Use the same idea as we currently use
> > in cgroup/egress where bit #1 indicates CN. Instead, for
> > cgroup/bind{4,6}, bit #1 indicates that CAP_NET_BIND_SERVICE should
> > be bypassed.
> >
> > v3:
> > - Update description (Martin KaFai Lau)
> > - Fix capability restore in selftest (Martin KaFai Lau)
> >
> > v2:
> > - Switch to explicit return code (Martin KaFai Lau)
> >
>
> [ ... ]
>
> > @@ -499,7 +501,8 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
> >
> > snum = ntohs(addr->sin_port);
> > err = -EACCES;
> > - if (snum && inet_port_requires_bind_service(net, snum) &&
> > + if (!(flags & BIND_NO_CAP_NET_BIND_SERVICE) &&
> > + snum && inet_port_requires_bind_service(net, snum) &&
> The same change needs to be done on __inet6_bind()
> and also adds a test for IPv6 in patch 2.
Oh, damn, I did add the flag but forgot to handle it. Thanks for
catching this, will do!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works
2021-01-26 16:51 ` [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works Stanislav Fomichev
@ 2021-01-26 18:18 ` Martin KaFai Lau
2021-01-26 19:04 ` Stanislav Fomichev
0 siblings, 1 reply; 6+ messages in thread
From: Martin KaFai Lau @ 2021-01-26 18:18 UTC (permalink / raw)
To: Stanislav Fomichev; +Cc: netdev, bpf, ast, daniel, Andrey Ignatov
On Tue, Jan 26, 2021 at 08:51:04AM -0800, Stanislav Fomichev wrote:
> Return 3 to indicate that permission check for port 111
> should be skipped.
>
[ ... ]
> +void cap_net_bind_service(cap_flag_value_t flag)
> +{
> + const cap_value_t cap_net_bind_service = CAP_NET_BIND_SERVICE;
> + cap_t caps;
> +
> + caps = cap_get_proc();
> + if (CHECK(!caps, "cap_get_proc", "errno %d", errno))
> + goto free_caps;
> +
> + if (CHECK(cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_net_bind_service,
> + flag),
> + "cap_set_flag", "errno %d", errno))
> + goto free_caps;
> +
> + if (CHECK(cap_set_proc(caps), "cap_set_proc", "errno %d", errno))
> + goto free_caps;
> +
> +free_caps:
> + if (CHECK(cap_free(caps), "cap_free", "errno %d", errno))
> + goto free_caps;
Also mentioned in v2, there is a loop.
> +}
> +
> +void test_bind_perm(void)
> +{
> + struct bind_perm *skel;
> + int cgroup_fd;
> +
> + cgroup_fd = test__join_cgroup("/bind_perm");
> + if (CHECK(cgroup_fd < 0, "cg-join", "errno %d", errno))
> + return;
> +
> + skel = bind_perm__open_and_load();
> + if (!ASSERT_OK_PTR(skel, "skel"))
> + goto close_cgroup_fd;
> +
> + skel->links.bind_v4_prog = bpf_program__attach_cgroup(skel->progs.bind_v4_prog, cgroup_fd);
> + if (!ASSERT_OK_PTR(skel, "bind_v4_prog"))
> + goto close_skeleton;
> +
> + cap_net_bind_service(CAP_CLEAR);
> + try_bind(110, EACCES);
> + try_bind(111, 0);
> + cap_net_bind_service(CAP_SET);
Instead of always CAP_SET at the end of the test,
it is better to do a cap_get_flag() to save the original value
at the beginning of the test and restore it at the end
of the test.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works
2021-01-26 18:18 ` Martin KaFai Lau
@ 2021-01-26 19:04 ` Stanislav Fomichev
0 siblings, 0 replies; 6+ messages in thread
From: Stanislav Fomichev @ 2021-01-26 19:04 UTC (permalink / raw)
To: Martin KaFai Lau
Cc: Netdev, bpf, Alexei Starovoitov, Daniel Borkmann, Andrey Ignatov
On Tue, Jan 26, 2021 at 10:18 AM Martin KaFai Lau <kafai@fb.com> wrote:
>
> On Tue, Jan 26, 2021 at 08:51:04AM -0800, Stanislav Fomichev wrote:
> > Return 3 to indicate that permission check for port 111
> > should be skipped.
> >
>
> [ ... ]
>
> > +void cap_net_bind_service(cap_flag_value_t flag)
> > +{
> > + const cap_value_t cap_net_bind_service = CAP_NET_BIND_SERVICE;
> > + cap_t caps;
> > +
> > + caps = cap_get_proc();
> > + if (CHECK(!caps, "cap_get_proc", "errno %d", errno))
> > + goto free_caps;
> > +
> > + if (CHECK(cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap_net_bind_service,
> > + flag),
> > + "cap_set_flag", "errno %d", errno))
> > + goto free_caps;
> > +
> > + if (CHECK(cap_set_proc(caps), "cap_set_proc", "errno %d", errno))
> > + goto free_caps;
> > +
> > +free_caps:
> > + if (CHECK(cap_free(caps), "cap_free", "errno %d", errno))
> > + goto free_caps;
> Also mentioned in v2, there is a loop.
Oops, missed that one, sorry.
> > +}
> > +
> > +void test_bind_perm(void)
> > +{
> > + struct bind_perm *skel;
> > + int cgroup_fd;
> > +
> > + cgroup_fd = test__join_cgroup("/bind_perm");
> > + if (CHECK(cgroup_fd < 0, "cg-join", "errno %d", errno))
> > + return;
> > +
> > + skel = bind_perm__open_and_load();
> > + if (!ASSERT_OK_PTR(skel, "skel"))
> > + goto close_cgroup_fd;
> > +
> > + skel->links.bind_v4_prog = bpf_program__attach_cgroup(skel->progs.bind_v4_prog, cgroup_fd);
> > + if (!ASSERT_OK_PTR(skel, "bind_v4_prog"))
> > + goto close_skeleton;
> > +
> > + cap_net_bind_service(CAP_CLEAR);
> > + try_bind(110, EACCES);
> > + try_bind(111, 0);
> > + cap_net_bind_service(CAP_SET);
> Instead of always CAP_SET at the end of the test,
> it is better to do a cap_get_flag() to save the original value
> at the beginning of the test and restore it at the end
> of the test.
It might be easier to change cap_net_bind_service() to return a bool
which indicates that the flag was originally set.
If it wasn't, we can bypass cap_net_bind_service(CAP_SET).
Let me know if you strongly disagree, I'll try to play with this idea
and will send a v4 if it plays out nicely.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-01-27 12:49 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-01-26 16:51 [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Stanislav Fomichev
2021-01-26 16:51 ` [PATCH bpf-next v3 2/2] selftests/bpf: verify that rebinding to port < 1024 from BPF works Stanislav Fomichev
2021-01-26 18:18 ` Martin KaFai Lau
2021-01-26 19:04 ` Stanislav Fomichev
2021-01-26 18:01 ` [PATCH bpf-next v3 1/2] bpf: allow rewriting to ports under ip_unprivileged_port_start Martin KaFai Lau
2021-01-26 18:05 ` Stanislav Fomichev
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