selftests/bpf: Verify that rebinding to port < 1024 from BPF works

Return 3 to indicate that permission check for port 111
should be skipped.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210127193140.3170382-2-sdf@google.com

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 (file)
index 0000000..d0f06e4
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bind_perm.c
@@ -0,0 +1,109 @@
+// 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 family, int port, int expected_errno)
+{
+       struct sockaddr_storage addr = {};
+       struct sockaddr_in6 *sin6;
+       struct sockaddr_in *sin;
+       int fd = -1;
+
+       fd = socket(family, SOCK_STREAM, 0);
+       if (CHECK(fd < 0, "fd", "errno %d", errno))
+               goto close_socket;
+
+       if (family == AF_INET) {
+               sin = (struct sockaddr_in *)&addr;
+               sin->sin_family = family;
+               sin->sin_port = htons(port);
+       } else {
+               sin6 = (struct sockaddr_in6 *)&addr;
+               sin6->sin6_family = family;
+               sin6->sin6_port = htons(port);
+       }
+
+       errno = 0;
+       bind(fd, (struct sockaddr *)&addr, sizeof(addr));
+       ASSERT_EQ(errno, expected_errno, "bind");
+
+close_socket:
+       if (fd >= 0)
+               close(fd);
+}
+
+bool cap_net_bind_service(cap_flag_value_t flag)
+{
+       const cap_value_t cap_net_bind_service = CAP_NET_BIND_SERVICE;
+       cap_flag_value_t original_value;
+       bool was_effective = false;
+       cap_t caps;
+
+       caps = cap_get_proc();
+       if (CHECK(!caps, "cap_get_proc", "errno %d", errno))
+               goto free_caps;
+
+       if (CHECK(cap_get_flag(caps, CAP_NET_BIND_SERVICE, CAP_EFFECTIVE,
+                              &original_value),
+                 "cap_get_flag", "errno %d", errno))
+               goto free_caps;
+
+       was_effective = (original_value == CAP_SET);
+
+       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:
+       CHECK(cap_free(caps), "cap_free", "errno %d", errno);
+       return was_effective;
+}
+
+void test_bind_perm(void)
+{
+       bool cap_was_effective;
+       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;
+
+       skel->links.bind_v6_prog = bpf_program__attach_cgroup(skel->progs.bind_v6_prog, cgroup_fd);
+       if (!ASSERT_OK_PTR(skel, "bind_v6_prog"))
+               goto close_skeleton;
+
+       cap_was_effective = cap_net_bind_service(CAP_CLEAR);
+
+       try_bind(AF_INET, 110, EACCES);
+       try_bind(AF_INET6, 110, EACCES);
+
+       try_bind(AF_INET, 111, 0);
+       try_bind(AF_INET6, 111, 0);
+
+       if (cap_was_effective)
+               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 (file)
index 0000000..7bd2a02
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bind_perm.c
@@ -0,0 +1,45 @@
+// 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>
+
+static __always_inline int bind_prog(struct bpf_sock_addr *ctx, int family)
+{
+       struct bpf_sock *sk;
+
+       sk = ctx->sk;
+       if (!sk)
+               return 0;
+
+       if (sk->family != family)
+               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;
+}
+
+SEC("cgroup/bind4")
+int bind_v4_prog(struct bpf_sock_addr *ctx)
+{
+       return bind_prog(ctx, AF_INET);
+}
+
+SEC("cgroup/bind6")
+int bind_v6_prog(struct bpf_sock_addr *ctx)
+{
+       return bind_prog(ctx, AF_INET6);
+}
+
+char _license[] SEC("license") = "GPL";