From: Roberto Sassu <[email protected]>
One of the desirable features in security is the ability to restrict import
of data to a given system based on data authenticity. If data import can be
restricted, it would be possible to enforce a system-wide policy based on
the signing keys the system owner trusts.
This feature is widely used in the kernel. For example, if the restriction
is enabled, kernel modules can be plugged in only if they are signed with a
key whose public part is in the primary or secondary keyring.
For eBPF, it can be useful as well. For example, it might be useful to
authenticate data an eBPF program makes security decisions on.
After a discussion in the eBPF mailing list, it was decided that the stated
goal should be accomplished by introducing four new kfuncs:
bpf_lookup_user_key() and bpf_lookup_system_key(), for retrieving a keyring
with keys trusted for signature verification, respectively from its serial
and from a pre-determined ID; bpf_key_put(), to release the reference
obtained with the former two kfuncs, bpf_verify_pkcs7_signature(), for
verifying PKCS#7 signatures.
Other than the key serial, bpf_lookup_user_key() also accepts key lookup
flags, that influence the behavior of the lookup. bpf_lookup_system_key()
accepts pre-determined IDs defined in include/linux/verification.h.
bpf_key_put() accepts the new bpf_key structure, introduced to tell whether
the other structure member, a key pointer, is valid or not. The reason is
that verify_pkcs7_signature() also accepts invalid pointers, set with the
pre-determined ID, to select a system-defined keyring. key_put() must be
called only for valid key pointers.
Since the two key lookup functions allocate memory and one increments a key
reference count, they must be used in conjunction with bpf_key_put(). The
latter must be called only if the lookup functions returned a non-NULL
pointer. The verifier denies the execution of eBPF programs that don't
respect this rule.
The two key lookup functions should be used in alternative, depending on
the use case. While bpf_lookup_user_key() provides great flexibility, it
seems suboptimal in terms of security guarantees, as even if the eBPF
program is assumed to be trusted, the serial used to obtain the key pointer
might come from untrusted user space not choosing one that the system
administrator approves to enforce a mandatory policy.
bpf_lookup_system_key() instead provides much stronger guarantees,
especially if the pre-determined ID is not passed by user space but is
hardcoded in the eBPF program, and that program is signed. In this case,
bpf_verify_pkcs7_signature() will always perform signature verification
with a key that the system administrator approves, i.e. the primary,
secondary or platform keyring.
Nevertheless, key permission checks need to be done accurately. Since
bpf_lookup_user_key() cannot determine how a key will be used by other
kfuncs, it has to defer the permission check to the actual kfunc using the
key. It does it by calling lookup_user_key() with KEY_DEFER_PERM_CHECK as
needed permission. Later, bpf_verify_pkcs7_signature(), if called,
completes the permission check by calling key_validate(). It does not need
to call key_task_permission() with permission KEY_NEED_SEARCH, as it is
already done elsewhere by the key subsystem. Future kfuncs using the
bpf_key structure need to implement the proper checks as well.
Finally, the last kfunc, bpf_verify_pkcs7_signature(), accepts the data and
signature to verify as eBPF dynamic pointers, to minimize the number of
kfunc parameters, and the keyring with keys for signature verification as a
bpf_key structure, returned by one of the two key lookup functions.
bpf_lookup_user_key() and bpf_verify_pkcs7_signature() can be called only
from sleepable programs, because of memory allocation and crypto
operations. For example, the lsm.s/bpf attach point is suitable,
fexit/array_map_update_elem is not.
The correctness of implementation of the new kfuncs and of their usage is
checked with the introduced tests.
The patch set includes a patch from another author (dependency) for sake of
completeness. It is organized as follows.
Patch 1 from KP Singh allows kfuncs to be used by LSM programs. Patch 2
exports the bpf_dynptr definition through BTF. Patch 3 splits
is_dynptr_reg_valid_init() and introduces is_dynptr_type_expected(), to
know more precisely the cause of a negative result of a dynamic pointer
check. Patch 4 allows dynamic pointers to be used as kfunc parameters.
Patch 5 exports bpf_dynptr_get_size(), to obtain the real size of data
carried by a dynamic pointer. Patch 6 makes available for new eBPF kfuncs
and programs some key-related definitions. Patch 7 introduces the
bpf_lookup_*_key() and bpf_key_put() kfuncs. Patch 8 introduces the
bpf_verify_pkcs7_signature() kfunc. Patch 9 changes the testing kernel
configuration to compile everything as built-in. Finally, patches 10-13
introduce the tests.
Changelog
v17:
- Remove unnecessary typedefs in test_verify_pkcs7_sig.c (suggested by KP)
- Add patch to export bpf_dynptr through BTF (reported by KP)
- Rename u{8,16,32,64} variables to __u{8,16,32,64} in the tests, for
consistency with other eBPF programs (suggested by Yonghong)
v16:
- Remove comments in include/linux/key.h for KEY_LOOKUP_*
- Change kmalloc() flag from GFP_ATOMIC to GFP_KERNEL in
bpf_lookup_user_key(), as the kfunc needs anyway to be sleepable
(suggested by Kumar)
- Test passing a dynamic pointer with NULL data to
bpf_verify_pkcs7_signature() (suggested by Kumar)
v15:
- Add kfunc_dynptr_param test to deny list for s390x
v14:
- Explain that is_dynptr_type_expected() will be useful also for BTF
(suggested by Joanne)
- Rename KEY_LOOKUP_FLAGS_ALL to KEY_LOOKUP_ALL (suggested by Jarkko)
- Swap declaration of spi and dynptr_type in is_dynptr_type_expected()
(suggested by Joanne)
- Reimplement kfunc dynptr tests with a regular eBPF program instead of
executing them with test_verifier (suggested by Joanne)
- Make key lookup flags as enum so that they are automatically exported
through BTF (suggested by Alexei)
v13:
- Split is_dynptr_reg_valid_init() and introduce is_dynptr_type_expected()
to see if the dynamic pointer type passed as argument to a kfunc is
supported (suggested by Kumar)
- Add forward declaration of struct key in include/linux/bpf.h (suggested
by Song)
- Declare mask for key lookup flags, remove key_lookup_flags_check()
(suggested by Jarkko and KP)
- Allow only certain dynamic pointer types (currently, local) to be passed
as argument to kfuncs (suggested by Kumar)
- For each dynamic pointer parameter in kfunc, additionally check if the
passed pointer is to the stack (suggested by Kumar)
- Split the validity/initialization and dynamic pointer type check also in
the verifier, and adjust the expected error message in the test (a test
for an unexpected dynptr type passed to a helper cannot be added due to
missing suitable helpers, but this case has been tested manually)
- Add verifier tests to check the dynamic pointers passed as argument to
kfuncs (suggested by Kumar)
v12:
- Put lookup_key and verify_pkcs7_sig tests in deny list for s390x (JIT
does not support calling kernel function)
v11:
- Move stringify_struct() macro to include/linux/btf.h (suggested by
Daniel)
- Change kernel configuration options in
tools/testing/selftests/bpf/config* from =m to =y
v10:
- Introduce key_lookup_flags_check() and system_keyring_id_check() inline
functions to check parameters (suggested by KP)
- Fix descriptions and comment of key-related kfuncs (suggested by KP)
- Register kfunc set only once (suggested by Alexei)
- Move needed kernel options to the architecture-independent configuration
for testing
v9:
- Drop patch to introduce KF_SLEEPABLE kfunc flag (already merged)
- Rename valid_ptr member of bpf_key to has_ref (suggested by Daniel)
- Check dynamic pointers in kfunc definition with bpf_dynptr_kern struct
definition instead of string, to detect structure renames (suggested by
Daniel)
- Explicitly say that we permit initialized dynamic pointers in kfunc
definition (suggested by Daniel)
- Remove noinline __weak from kfuncs definition (reported by Daniel)
- Simplify key lookup flags check in bpf_lookup_user_key() (suggested by
Daniel)
- Explain the reason for deferring key permission check (suggested by
Daniel)
- Allocate memory with GFP_ATOMIC in bpf_lookup_system_key(), and remove
KF_SLEEPABLE kfunc flag from kfunc declaration (suggested by Daniel)
- Define only one kfunc set and remove the loop for registration
(suggested by Alexei)
v8:
- Define the new bpf_key structure to carry the key pointer and whether
that pointer is valid or not (suggested by Daniel)
- Drop patch to mark a kfunc parameter with the __maybe_null suffix
- Improve documentation of kfuncs
- Introduce bpf_lookup_system_key() to obtain a key pointer suitable for
verify_pkcs7_signature() (suggested by Daniel)
- Use the new kfunc registration API
- Drop patch to test the __maybe_null suffix
- Add tests for bpf_lookup_system_key()
v7:
- Add support for using dynamic and NULL pointers in kfunc (suggested by
Alexei)
- Add new kfunc-related tests
v6:
- Switch back to key lookup helpers + signature verification (until v5),
and defer permission check from bpf_lookup_user_key() to
bpf_verify_pkcs7_signature()
- Add additional key lookup test to illustrate the usage of the
KEY_LOOKUP_CREATE flag and validate the flags (suggested by Daniel)
- Make description of flags of bpf_lookup_user_key() more user-friendly
(suggested by Daniel)
- Fix validation of flags parameter in bpf_lookup_user_key() (reported by
Daniel)
- Rename bpf_verify_pkcs7_signature() keyring-related parameters to
user_keyring and system_keyring to make their purpose more clear
- Accept keyring-related parameters of bpf_verify_pkcs7_signature() as
alternatives (suggested by KP)
- Replace unsigned long type with u64 in helper declaration (suggested by
Daniel)
- Extend the bpf_verify_pkcs7_signature() test by calling the helper
without data, by ensuring that the helper enforces the keyring-related
parameters as alternatives, by ensuring that the helper rejects
inaccessible and expired keyrings, and by checking all system keyrings
- Move bpf_lookup_user_key() and bpf_key_put() usage tests to
ref_tracking.c (suggested by John)
- Call bpf_lookup_user_key() and bpf_key_put() only in sleepable programs
v5:
- Move KEY_LOOKUP_ to include/linux/key.h
for validation of bpf_verify_pkcs7_signature() parameter
- Remove bpf_lookup_user_key() and bpf_key_put() helpers, and the
corresponding tests
- Replace struct key parameter of bpf_verify_pkcs7_signature() with the
keyring serial and lookup flags
- Call lookup_user_key() and key_put() in bpf_verify_pkcs7_signature()
code, to ensure that the retrieved key is used according to the
permission requested at lookup time
- Clarified keyring precedence in the description of
bpf_verify_pkcs7_signature() (suggested by John)
- Remove newline in the second argument of ASSERT_
- Fix helper prototype regular expression in bpf_doc.py
v4:
- Remove bpf_request_key_by_id(), don't return an invalid pointer that
other helpers can use
- Pass the keyring ID (without ULONG_MAX, suggested by Alexei) to
bpf_verify_pkcs7_signature()
- Introduce bpf_lookup_user_key() and bpf_key_put() helpers (suggested by
Alexei)
- Add lookup_key_norelease test, to ensure that the verifier blocks eBPF
programs which don't decrement the key reference count
- Parse raw PKCS#7 signature instead of module-style signature in the
verify_pkcs7_signature test (suggested by Alexei)
- Parse kernel module in user space and pass raw PKCS#7 signature to the
eBPF program for signature verification
v3:
- Rename bpf_verify_signature() back to bpf_verify_pkcs7_signature() to
avoid managing different parameters for each signature verification
function in one helper (suggested by Daniel)
- Use dynamic pointers and export bpf_dynptr_get_size() (suggested by
Alexei)
- Introduce bpf_request_key_by_id() to give more flexibility to the caller
of bpf_verify_pkcs7_signature() to retrieve the appropriate keyring
(suggested by Alexei)
- Fix test by reordering the gcc command line, always compile sign-file
- Improve helper support check mechanism in the test
v2:
- Rename bpf_verify_pkcs7_signature() to a more generic
bpf_verify_signature() and pass the signature type (suggested by KP)
- Move the helper and prototype declaration under #ifdef so that user
space can probe for support for the helper (suggested by Daniel)
- Describe better the keyring types (suggested by Daniel)
- Include linux/bpf.h instead of vmlinux.h to avoid implicit or
redeclaration
- Make the test selfcontained (suggested by Alexei)
v1:
- Don't define new map flag but introduce simple wrapper of
verify_pkcs7_signature() (suggested by Alexei and KP)
KP Singh (1):
bpf: Allow kfuncs to be used in LSM programs
Roberto Sassu (12):
btf: Export bpf_dynptr definition
bpf: Move dynptr type check to is_dynptr_type_expected()
btf: Allow dynamic pointer parameters in kfuncs
bpf: Export bpf_dynptr_get_size()
KEYS: Move KEY_LOOKUP_ to include/linux/key.h and define
KEY_LOOKUP_ALL
bpf: Add bpf_lookup_*_key() and bpf_key_put() kfuncs
bpf: Add bpf_verify_pkcs7_signature() kfunc
selftests/bpf: Compile kernel with everything as built-in
selftests/bpf: Add verifier tests for bpf_lookup_*_key() and
bpf_key_put()
selftests/bpf: Add additional tests for bpf_lookup_*_key()
selftests/bpf: Add test for bpf_verify_pkcs7_signature() kfunc
selftests/bpf: Add tests for dynamic pointers parameters in kfuncs
include/linux/bpf.h | 9 +
include/linux/bpf_verifier.h | 5 +
include/linux/btf.h | 9 +
include/linux/key.h | 6 +
include/linux/verification.h | 8 +
kernel/bpf/btf.c | 34 ++
kernel/bpf/helpers.c | 4 +-
kernel/bpf/verifier.c | 35 +-
kernel/trace/bpf_trace.c | 180 ++++++++
security/keys/internal.h | 2 -
tools/testing/selftests/bpf/DENYLIST.s390x | 3 +
tools/testing/selftests/bpf/Makefile | 14 +-
tools/testing/selftests/bpf/config | 32 +-
tools/testing/selftests/bpf/config.x86_64 | 7 +-
.../testing/selftests/bpf/prog_tests/dynptr.c | 2 +-
.../bpf/prog_tests/kfunc_dynptr_param.c | 164 +++++++
.../selftests/bpf/prog_tests/lookup_key.c | 112 +++++
.../bpf/prog_tests/verify_pkcs7_sig.c | 399 ++++++++++++++++++
.../bpf/progs/test_kfunc_dynptr_param.c | 94 +++++
.../selftests/bpf/progs/test_lookup_key.c | 46 ++
.../bpf/progs/test_verify_pkcs7_sig.c | 90 ++++
tools/testing/selftests/bpf/test_verifier.c | 3 +-
.../selftests/bpf/verifier/ref_tracking.c | 139 ++++++
.../testing/selftests/bpf/verify_sig_setup.sh | 104 +++++
24 files changed, 1466 insertions(+), 35 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
create mode 100644 tools/testing/selftests/bpf/prog_tests/lookup_key.c
create mode 100644 tools/testing/selftests/bpf/prog_tests/verify_pkcs7_sig.c
create mode 100644 tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
create mode 100644 tools/testing/selftests/bpf/progs/test_lookup_key.c
create mode 100644 tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
create mode 100755 tools/testing/selftests/bpf/verify_sig_setup.sh
--
2.25.1
From: Roberto Sassu <[email protected]>
Add tests to ensure that only supported dynamic pointer types are accepted,
that the passed argument is actually a dynamic pointer, that the passed
argument is a pointer to the stack, and that bpf_verify_pkcs7_signature()
correctly handles dynamic pointers with data set to NULL.
The tests are currently in the deny list for s390x (JIT does not support
calling kernel function).
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
---
tools/testing/selftests/bpf/DENYLIST.s390x | 1 +
.../bpf/prog_tests/kfunc_dynptr_param.c | 164 ++++++++++++++++++
.../bpf/progs/test_kfunc_dynptr_param.c | 94 ++++++++++
3 files changed, 259 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
create mode 100644 tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index 759b2bb53b53..5fc7d0de19f3 100644
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -73,3 +73,4 @@ htab_update # failed to attach: ERROR: strerror_r(-
tracing_struct # failed to auto-attach: -524 (trampoline)
lookup_key # JIT does not support calling kernel function (kfunc)
verify_pkcs7_sig # JIT does not support calling kernel function (kfunc)
+kfunc_dynptr_param # JIT does not support calling kernel function (kfunc)
diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
new file mode 100644
index 000000000000..c210657d4d0a
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/kfunc_dynptr_param.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2022 Facebook
+ * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <[email protected]>
+ */
+
+#include <test_progs.h>
+#include "test_kfunc_dynptr_param.skel.h"
+
+static size_t log_buf_sz = 1048576; /* 1 MB */
+static char obj_log_buf[1048576];
+
+static struct {
+ const char *prog_name;
+ const char *expected_verifier_err_msg;
+ int expected_runtime_err;
+} kfunc_dynptr_tests[] = {
+ {"dynptr_type_not_supp",
+ "arg#0 pointer type STRUCT bpf_dynptr_kern points to unsupported dynamic pointer type", 0},
+ {"not_valid_dynptr",
+ "arg#0 pointer type STRUCT bpf_dynptr_kern must be valid and initialized", 0},
+ {"not_ptr_to_stack", "arg#0 pointer type STRUCT bpf_dynptr_kern not to stack", 0},
+ {"dynptr_data_null", NULL, -EBADMSG},
+};
+
+static bool kfunc_not_supported;
+
+static int libbpf_print_cb(enum libbpf_print_level level, const char *fmt,
+ va_list args)
+{
+ if (strcmp(fmt, "libbpf: extern (func ksym) '%s': not found in kernel or module BTFs\n"))
+ return 0;
+
+ if (strcmp(va_arg(args, char *), "bpf_verify_pkcs7_signature"))
+ return 0;
+
+ kfunc_not_supported = true;
+ return 0;
+}
+
+static void verify_fail(const char *prog_name, const char *expected_err_msg)
+{
+ struct test_kfunc_dynptr_param *skel;
+ LIBBPF_OPTS(bpf_object_open_opts, opts);
+ libbpf_print_fn_t old_print_cb;
+ struct bpf_program *prog;
+ int err;
+
+ opts.kernel_log_buf = obj_log_buf;
+ opts.kernel_log_size = log_buf_sz;
+ opts.kernel_log_level = 1;
+
+ skel = test_kfunc_dynptr_param__open_opts(&opts);
+ if (!ASSERT_OK_PTR(skel, "test_kfunc_dynptr_param__open_opts"))
+ goto cleanup;
+
+ prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+ if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+ goto cleanup;
+
+ bpf_program__set_autoload(prog, true);
+
+ bpf_map__set_max_entries(skel->maps.ringbuf, getpagesize());
+
+ kfunc_not_supported = false;
+
+ old_print_cb = libbpf_set_print(libbpf_print_cb);
+ err = test_kfunc_dynptr_param__load(skel);
+ libbpf_set_print(old_print_cb);
+
+ if (err < 0 && kfunc_not_supported) {
+ fprintf(stderr,
+ "%s:SKIP:bpf_verify_pkcs7_signature() kfunc not supported\n",
+ __func__);
+ test__skip();
+ goto cleanup;
+ }
+
+ if (!ASSERT_ERR(err, "unexpected load success"))
+ goto cleanup;
+
+ if (!ASSERT_OK_PTR(strstr(obj_log_buf, expected_err_msg), "expected_err_msg")) {
+ fprintf(stderr, "Expected err_msg: %s\n", expected_err_msg);
+ fprintf(stderr, "Verifier output: %s\n", obj_log_buf);
+ }
+
+cleanup:
+ test_kfunc_dynptr_param__destroy(skel);
+}
+
+static void verify_success(const char *prog_name, int expected_runtime_err)
+{
+ struct test_kfunc_dynptr_param *skel;
+ libbpf_print_fn_t old_print_cb;
+ struct bpf_program *prog;
+ struct bpf_link *link;
+ __u32 next_id;
+ int err;
+
+ skel = test_kfunc_dynptr_param__open();
+ if (!ASSERT_OK_PTR(skel, "test_kfunc_dynptr_param__open"))
+ return;
+
+ skel->bss->pid = getpid();
+
+ bpf_map__set_max_entries(skel->maps.ringbuf, getpagesize());
+
+ kfunc_not_supported = false;
+
+ old_print_cb = libbpf_set_print(libbpf_print_cb);
+ err = test_kfunc_dynptr_param__load(skel);
+ libbpf_set_print(old_print_cb);
+
+ if (err < 0 && kfunc_not_supported) {
+ fprintf(stderr,
+ "%s:SKIP:bpf_verify_pkcs7_signature() kfunc not supported\n",
+ __func__);
+ test__skip();
+ goto cleanup;
+ }
+
+ if (!ASSERT_OK(err, "test_kfunc_dynptr_param__load"))
+ goto cleanup;
+
+ prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+ if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
+ goto cleanup;
+
+ link = bpf_program__attach(prog);
+ if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
+ goto cleanup;
+
+ err = bpf_prog_get_next_id(0, &next_id);
+
+ bpf_link__destroy(link);
+
+ if (!ASSERT_OK(err, "bpf_prog_get_next_id"))
+ goto cleanup;
+
+ ASSERT_EQ(skel->bss->err, expected_runtime_err, "err");
+
+cleanup:
+ test_kfunc_dynptr_param__destroy(skel);
+}
+
+void test_kfunc_dynptr_param(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(kfunc_dynptr_tests); i++) {
+ if (!test__start_subtest(kfunc_dynptr_tests[i].prog_name))
+ continue;
+
+ if (kfunc_dynptr_tests[i].expected_verifier_err_msg)
+ verify_fail(kfunc_dynptr_tests[i].prog_name,
+ kfunc_dynptr_tests[i].expected_verifier_err_msg);
+ else
+ verify_success(kfunc_dynptr_tests[i].prog_name,
+ kfunc_dynptr_tests[i].expected_runtime_err);
+ }
+}
diff --git a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
new file mode 100644
index 000000000000..ce39d096bba3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <[email protected]>
+ */
+
+#include "vmlinux.h"
+#include <errno.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym;
+extern void bpf_key_put(struct bpf_key *key) __ksym;
+extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr,
+ struct bpf_dynptr *sig_ptr,
+ struct bpf_key *trusted_keyring) __ksym;
+
+struct {
+ __uint(type, BPF_MAP_TYPE_RINGBUF);
+} ringbuf SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, __u32);
+} array_map SEC(".maps");
+
+int err, pid;
+
+char _license[] SEC("license") = "GPL";
+
+SEC("?lsm.s/bpf")
+int BPF_PROG(dynptr_type_not_supp, int cmd, union bpf_attr *attr,
+ unsigned int size)
+{
+ char write_data[64] = "hello there, world!!";
+ struct bpf_dynptr ptr;
+
+ bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(write_data), 0, &ptr);
+
+ return bpf_verify_pkcs7_signature(&ptr, &ptr, NULL);
+}
+
+SEC("?lsm.s/bpf")
+int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size)
+{
+ unsigned long val;
+
+ return bpf_verify_pkcs7_signature((struct bpf_dynptr *)&val,
+ (struct bpf_dynptr *)&val, NULL);
+}
+
+SEC("?lsm.s/bpf")
+int BPF_PROG(not_ptr_to_stack, int cmd, union bpf_attr *attr, unsigned int size)
+{
+ unsigned long val;
+
+ return bpf_verify_pkcs7_signature((struct bpf_dynptr *)val,
+ (struct bpf_dynptr *)val, NULL);
+}
+
+SEC("lsm.s/bpf")
+int BPF_PROG(dynptr_data_null, int cmd, union bpf_attr *attr, unsigned int size)
+{
+ struct bpf_key *trusted_keyring;
+ struct bpf_dynptr ptr;
+ __u32 *value;
+ int ret, zero = 0;
+
+ if (bpf_get_current_pid_tgid() >> 32 != pid)
+ return 0;
+
+ value = bpf_map_lookup_elem(&array_map, &zero);
+ if (!value)
+ return 0;
+
+ /* Pass invalid flags. */
+ ret = bpf_dynptr_from_mem(value, sizeof(*value), ((__u64)~0ULL), &ptr);
+ if (ret != -EINVAL)
+ return 0;
+
+ trusted_keyring = bpf_lookup_system_key(0);
+ if (!trusted_keyring)
+ return 0;
+
+ err = bpf_verify_pkcs7_signature(&ptr, &ptr, trusted_keyring);
+
+ bpf_key_put(trusted_keyring);
+
+ return 0;
+}
--
2.25.1
From: Roberto Sassu <[email protected]>
Add the bpf_verify_pkcs7_signature() kfunc, to give eBPF security modules
the ability to check the validity of a signature against supplied data, by
using user-provided or system-provided keys as trust anchor.
The new kfunc makes it possible to enforce mandatory policies, as eBPF
programs might be allowed to make security decisions only based on data
sources the system administrator approves.
The caller should provide the data to be verified and the signature as eBPF
dynamic pointers (to minimize the number of parameters) and a bpf_key
structure containing a reference to the keyring with keys trusted for
signature verification, obtained from bpf_lookup_user_key() or
bpf_lookup_system_key().
For bpf_key structures obtained from the former lookup function,
bpf_verify_pkcs7_signature() completes the permission check deferred by
that function by calling key_validate(). key_task_permission() is already
called by the PKCS#7 code.
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: KP Singh <[email protected]>
Acked-by: Song Liu <[email protected]>
---
kernel/trace/bpf_trace.c | 45 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ab183dbaa8d1..9df53c40cffd 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1294,12 +1294,57 @@ void bpf_key_put(struct bpf_key *bkey)
kfree(bkey);
}
+#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
+/**
+ * bpf_verify_pkcs7_signature - verify a PKCS#7 signature
+ * @data_ptr: data to verify
+ * @sig_ptr: signature of the data
+ * @trusted_keyring: keyring with keys trusted for signature verification
+ *
+ * Verify the PKCS#7 signature *sig_ptr* against the supplied *data_ptr*
+ * with keys in a keyring referenced by *trusted_keyring*.
+ *
+ * Return: 0 on success, a negative value on error.
+ */
+int bpf_verify_pkcs7_signature(struct bpf_dynptr_kern *data_ptr,
+ struct bpf_dynptr_kern *sig_ptr,
+ struct bpf_key *trusted_keyring)
+{
+ int ret;
+
+ if (trusted_keyring->has_ref) {
+ /*
+ * Do the permission check deferred in bpf_lookup_user_key().
+ * See bpf_lookup_user_key() for more details.
+ *
+ * A call to key_task_permission() here would be redundant, as
+ * it is already done by keyring_search() called by
+ * find_asymmetric_key().
+ */
+ ret = key_validate(trusted_keyring->key);
+ if (ret < 0)
+ return ret;
+ }
+
+ return verify_pkcs7_signature(data_ptr->data,
+ bpf_dynptr_get_size(data_ptr),
+ sig_ptr->data,
+ bpf_dynptr_get_size(sig_ptr),
+ trusted_keyring->key,
+ VERIFYING_UNSPECIFIED_SIGNATURE, NULL,
+ NULL);
+}
+#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
+
__diag_pop();
BTF_SET8_START(key_sig_kfunc_set)
BTF_ID_FLAGS(func, bpf_lookup_user_key, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)
BTF_ID_FLAGS(func, bpf_lookup_system_key, KF_ACQUIRE | KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_key_put, KF_RELEASE)
+#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
+BTF_ID_FLAGS(func, bpf_verify_pkcs7_signature, KF_SLEEPABLE)
+#endif
BTF_SET8_END(key_sig_kfunc_set)
static const struct btf_kfunc_id_set bpf_key_sig_kfunc_set = {
--
2.25.1
From: Roberto Sassu <[email protected]>
Add verifier tests for bpf_lookup_*_key() and bpf_key_put(), to ensure that
acquired key references stored in the bpf_key structure are released, that
a non-NULL bpf_key pointer is passed to bpf_key_put(), and that key
references are not leaked.
Also, slightly modify test_verifier.c, to find the BTF ID of the attach
point for the LSM program type (currently, it is done only for TRACING).
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
---
tools/testing/selftests/bpf/config | 1 +
tools/testing/selftests/bpf/test_verifier.c | 3 +-
.../selftests/bpf/verifier/ref_tracking.c | 139 ++++++++++++++++++
3 files changed, 142 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 0fdd11e6b742..add5a5a919b4 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -30,6 +30,7 @@ CONFIG_IPV6_GRE=y
CONFIG_IPV6_SEG6_BPF=y
CONFIG_IPV6_SIT=y
CONFIG_IPV6_TUNNEL=y
+CONFIG_KEYS=y
CONFIG_LIRC=y
CONFIG_LWTUNNEL=y
CONFIG_MPLS=y
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index f9d553fbf68a..2dbcbf363c18 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -1498,7 +1498,8 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
opts.log_level = DEFAULT_LIBBPF_LOG_LEVEL;
opts.prog_flags = pflags;
- if (prog_type == BPF_PROG_TYPE_TRACING && test->kfunc) {
+ if ((prog_type == BPF_PROG_TYPE_TRACING ||
+ prog_type == BPF_PROG_TYPE_LSM) && test->kfunc) {
int attach_btf_id;
attach_btf_id = libbpf_find_vmlinux_btf_id(test->kfunc,
diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
index 57a83d763ec1..f18ce867271f 100644
--- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
+++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
@@ -84,6 +84,145 @@
.errstr = "Unreleased reference",
.result = REJECT,
},
+{
+ "reference tracking: acquire/release user key reference",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, -3),
+ BPF_MOV64_IMM(BPF_REG_2, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .fixup_kfunc_btf_id = {
+ { "bpf_lookup_user_key", 2 },
+ { "bpf_key_put", 5 },
+ },
+ .result = ACCEPT,
+},
+{
+ "reference tracking: acquire/release system key reference",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, 1),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .fixup_kfunc_btf_id = {
+ { "bpf_lookup_system_key", 1 },
+ { "bpf_key_put", 4 },
+ },
+ .result = ACCEPT,
+},
+{
+ "reference tracking: release user key reference without check",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, -3),
+ BPF_MOV64_IMM(BPF_REG_2, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+ .fixup_kfunc_btf_id = {
+ { "bpf_lookup_user_key", 2 },
+ { "bpf_key_put", 4 },
+ },
+ .result = REJECT,
+},
+{
+ "reference tracking: release system key reference without check",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, 1),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+ .fixup_kfunc_btf_id = {
+ { "bpf_lookup_system_key", 1 },
+ { "bpf_key_put", 3 },
+ },
+ .result = REJECT,
+},
+{
+ "reference tracking: release with NULL key pointer",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
+ .fixup_kfunc_btf_id = {
+ { "bpf_key_put", 1 },
+ },
+ .result = REJECT,
+},
+{
+ "reference tracking: leak potential reference to user key",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, -3),
+ BPF_MOV64_IMM(BPF_REG_2, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .errstr = "Unreleased reference",
+ .fixup_kfunc_btf_id = {
+ { "bpf_lookup_user_key", 2 },
+ },
+ .result = REJECT,
+},
+{
+ "reference tracking: leak potential reference to system key",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, 1),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_LSM,
+ .kfunc = "bpf",
+ .expected_attach_type = BPF_LSM_MAC,
+ .flags = BPF_F_SLEEPABLE,
+ .errstr = "Unreleased reference",
+ .fixup_kfunc_btf_id = {
+ { "bpf_lookup_system_key", 1 },
+ },
+ .result = REJECT,
+},
{
"reference tracking: release reference without check",
.insns = {
--
2.25.1
From: KP Singh <[email protected]>
In preparation for the addition of new kfuncs, allow kfuncs defined in the
tracing subsystem to be used in LSM programs by mapping the LSM program
type to the TRACING hook.
Signed-off-by: KP Singh <[email protected]>
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
---
kernel/bpf/btf.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index b3940c605aac..dd60cd0efcf8 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7381,6 +7381,7 @@ static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
case BPF_PROG_TYPE_STRUCT_OPS:
return BTF_KFUNC_HOOK_STRUCT_OPS;
case BPF_PROG_TYPE_TRACING:
+ case BPF_PROG_TYPE_LSM:
return BTF_KFUNC_HOOK_TRACING;
case BPF_PROG_TYPE_SYSCALL:
return BTF_KFUNC_HOOK_SYSCALL;
--
2.25.1
From: Roberto Sassu <[email protected]>
Since the eBPF CI does not support kernel modules, change the kernel config
to compile everything as built-in.
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Daniel Müller <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
---
tools/testing/selftests/bpf/config | 26 +++++++++++------------
tools/testing/selftests/bpf/config.x86_64 | 2 +-
2 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index 3fc46f9cfb22..0fdd11e6b742 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -7,9 +7,9 @@ CONFIG_BPF_LSM=y
CONFIG_BPF_STREAM_PARSER=y
CONFIG_BPF_SYSCALL=y
CONFIG_CGROUP_BPF=y
-CONFIG_CRYPTO_HMAC=m
-CONFIG_CRYPTO_SHA256=m
-CONFIG_CRYPTO_USER_API_HASH=m
+CONFIG_CRYPTO_HMAC=y
+CONFIG_CRYPTO_SHA256=y
+CONFIG_CRYPTO_USER_API_HASH=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_FPROBE=y
CONFIG_FTRACE_SYSCALLS=y
@@ -24,30 +24,30 @@ CONFIG_IP_NF_FILTER=y
CONFIG_IP_NF_RAW=y
CONFIG_IP_NF_TARGET_SYNPROXY=y
CONFIG_IPV6=y
-CONFIG_IPV6_FOU=m
-CONFIG_IPV6_FOU_TUNNEL=m
+CONFIG_IPV6_FOU=y
+CONFIG_IPV6_FOU_TUNNEL=y
CONFIG_IPV6_GRE=y
CONFIG_IPV6_SEG6_BPF=y
-CONFIG_IPV6_SIT=m
+CONFIG_IPV6_SIT=y
CONFIG_IPV6_TUNNEL=y
CONFIG_LIRC=y
CONFIG_LWTUNNEL=y
CONFIG_MPLS=y
-CONFIG_MPLS_IPTUNNEL=m
-CONFIG_MPLS_ROUTING=m
+CONFIG_MPLS_IPTUNNEL=y
+CONFIG_MPLS_ROUTING=y
CONFIG_MPTCP=y
CONFIG_NET_CLS_ACT=y
CONFIG_NET_CLS_BPF=y
-CONFIG_NET_CLS_FLOWER=m
-CONFIG_NET_FOU=m
+CONFIG_NET_CLS_FLOWER=y
+CONFIG_NET_FOU=y
CONFIG_NET_FOU_IP_TUNNELS=y
CONFIG_NET_IPGRE=y
CONFIG_NET_IPGRE_DEMUX=y
CONFIG_NET_IPIP=y
-CONFIG_NET_MPLS_GSO=m
+CONFIG_NET_MPLS_GSO=y
CONFIG_NET_SCH_INGRESS=y
CONFIG_NET_SCHED=y
-CONFIG_NETDEVSIM=m
+CONFIG_NETDEVSIM=y
CONFIG_NETFILTER=y
CONFIG_NETFILTER_SYNPROXY=y
CONFIG_NETFILTER_XT_CONNMARK=y
@@ -60,7 +60,7 @@ CONFIG_NF_DEFRAG_IPV6=y
CONFIG_RC_CORE=y
CONFIG_SECURITY=y
CONFIG_SECURITYFS=y
-CONFIG_TEST_BPF=m
+CONFIG_TEST_BPF=y
CONFIG_USERFAULTFD=y
CONFIG_VXLAN=y
CONFIG_XDP_SOCKETS=y
diff --git a/tools/testing/selftests/bpf/config.x86_64 b/tools/testing/selftests/bpf/config.x86_64
index f0859a1d37ab..ce70c9509204 100644
--- a/tools/testing/selftests/bpf/config.x86_64
+++ b/tools/testing/selftests/bpf/config.x86_64
@@ -47,7 +47,7 @@ CONFIG_CPU_IDLE_GOV_LADDER=y
CONFIG_CPUSETS=y
CONFIG_CRC_T10DIF=y
CONFIG_CRYPTO_BLAKE2B=y
-CONFIG_CRYPTO_DEV_VIRTIO=m
+CONFIG_CRYPTO_DEV_VIRTIO=y
CONFIG_CRYPTO_SEQIV=y
CONFIG_CRYPTO_XXHASH=y
CONFIG_DCB=y
--
2.25.1
From: Roberto Sassu <[email protected]>
Allow dynamic pointers (struct bpf_dynptr_kern *) to be specified as
parameters in kfuncs. Also, ensure that dynamic pointers passed as argument
are valid and initialized, are a pointer to the stack, and of the type
local. More dynamic pointer types can be supported in the future.
To properly detect whether a parameter is of the desired type, introduce
the stringify_struct() macro to compare the returned structure name with
the desired name. In addition, protect against structure renames, by
halting the build with BUILD_BUG_ON(), so that developers have to revisit
the code.
To check if a dynamic pointer passed to the kfunc is valid and initialized,
and if its type is local, export the existing functions
is_dynptr_reg_valid_init() and is_dynptr_type_expected().
Cc: Joanne Koong <[email protected]>
Cc: Kumar Kartikeya Dwivedi <[email protected]>
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
---
include/linux/bpf_verifier.h | 5 +++++
include/linux/btf.h | 9 +++++++++
kernel/bpf/btf.c | 33 +++++++++++++++++++++++++++++++++
kernel/bpf/verifier.c | 10 +++++-----
4 files changed, 52 insertions(+), 5 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index e197f8fb27e2..9e1e6965f407 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -593,6 +593,11 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state
u32 regno);
int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
u32 regno, u32 mem_size);
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg);
+bool is_dynptr_type_expected(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type);
/* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 1fcc833a8690..f9aababc5d78 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -52,6 +52,15 @@
#define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
#define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */
+/*
+ * Return the name of the passed struct, if exists, or halt the build if for
+ * example the structure gets renamed. In this way, developers have to revisit
+ * the code using that structure name, and update it accordingly.
+ */
+#define stringify_struct(x) \
+ ({ BUILD_BUG_ON(sizeof(struct x) < 0); \
+ __stringify(x); })
+
struct btf;
struct btf_member;
struct btf_type;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index dd60cd0efcf8..dcdb9251752a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6454,15 +6454,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
if (is_kfunc) {
bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]);
+ bool arg_dynptr = btf_type_is_struct(ref_t) &&
+ !strcmp(ref_tname,
+ stringify_struct(bpf_dynptr_kern));
/* Permit pointer to mem, but only when argument
* type is pointer to scalar, or struct composed
* (recursively) of scalars.
* When arg_mem_size is true, the pointer can be
* void *.
+ * Also permit initialized local dynamic pointers.
*/
if (!btf_type_is_scalar(ref_t) &&
!__btf_type_is_scalar_struct(log, btf, ref_t, 0) &&
+ !arg_dynptr &&
(arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
bpf_log(log,
"arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
@@ -6470,6 +6475,34 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
return -EINVAL;
}
+ if (arg_dynptr) {
+ if (reg->type != PTR_TO_STACK) {
+ bpf_log(log, "arg#%d pointer type %s %s not to stack\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ if (!is_dynptr_reg_valid_init(env, reg)) {
+ bpf_log(log,
+ "arg#%d pointer type %s %s must be valid and initialized\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ if (!is_dynptr_type_expected(env, reg,
+ ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) {
+ bpf_log(log,
+ "arg#%d pointer type %s %s points to unsupported dynamic pointer type\n",
+ i, btf_type_str(ref_t),
+ ref_tname);
+ return -EINVAL;
+ }
+
+ continue;
+ }
+
/* Check for mem, len pair */
if (arg_mem_size) {
if (check_kfunc_mem_size_reg(env, ®s[regno + 1], regno + 1)) {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 53dad321ac0b..04241423d469 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -781,8 +781,8 @@ static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_
return true;
}
-static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
- struct bpf_reg_state *reg)
+bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg)
{
struct bpf_func_state *state = func(env, reg);
int spi = get_spi(reg->off);
@@ -801,9 +801,9 @@ static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
return true;
}
-static bool is_dynptr_type_expected(struct bpf_verifier_env *env,
- struct bpf_reg_state *reg,
- enum bpf_arg_type arg_type)
+bool is_dynptr_type_expected(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type)
{
struct bpf_func_state *state = func(env, reg);
enum bpf_dynptr_type dynptr_type;
--
2.25.1
From: Roberto Sassu <[email protected]>
Add the bpf_lookup_user_key(), bpf_lookup_system_key() and bpf_key_put()
kfuncs, to respectively search a key with a given key handle serial number
and flags, obtain a key from a pre-determined ID defined in
include/linux/verification.h, and cleanup.
Introduce system_keyring_id_check() to validate the keyring ID parameter of
bpf_lookup_system_key().
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
Acked-by: Song Liu <[email protected]>
---
include/linux/bpf.h | 8 +++
include/linux/verification.h | 8 +++
kernel/trace/bpf_trace.c | 135 +++++++++++++++++++++++++++++++++++
3 files changed, 151 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1a877e9a06db..45c5faa062d3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2657,4 +2657,12 @@ static inline void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype) {}
static inline void bpf_cgroup_atype_put(int cgroup_atype) {}
#endif /* CONFIG_BPF_LSM */
+struct key;
+
+#ifdef CONFIG_KEYS
+struct bpf_key {
+ struct key *key;
+ bool has_ref;
+};
+#endif /* CONFIG_KEYS */
#endif /* _LINUX_BPF_H */
diff --git a/include/linux/verification.h b/include/linux/verification.h
index a655923335ae..f34e50ebcf60 100644
--- a/include/linux/verification.h
+++ b/include/linux/verification.h
@@ -17,6 +17,14 @@
#define VERIFY_USE_SECONDARY_KEYRING ((struct key *)1UL)
#define VERIFY_USE_PLATFORM_KEYRING ((struct key *)2UL)
+static inline int system_keyring_id_check(u64 id)
+{
+ if (id > (unsigned long)VERIFY_USE_PLATFORM_KEYRING)
+ return -EINVAL;
+
+ return 0;
+}
+
/*
* The use to which an asymmetric key is being put.
*/
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 68e5cdd24cef..ab183dbaa8d1 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -20,6 +20,8 @@
#include <linux/fprobe.h>
#include <linux/bsearch.h>
#include <linux/sort.h>
+#include <linux/key.h>
+#include <linux/verification.h>
#include <net/bpf_sk_storage.h>
@@ -1181,6 +1183,139 @@ static const struct bpf_func_proto bpf_get_func_arg_cnt_proto = {
.arg1_type = ARG_PTR_TO_CTX,
};
+#ifdef CONFIG_KEYS
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+ "kfuncs which will be used in BPF programs");
+
+/**
+ * bpf_lookup_user_key - lookup a key by its serial
+ * @serial: key handle serial number
+ * @flags: lookup-specific flags
+ *
+ * Search a key with a given *serial* and the provided *flags*.
+ * If found, increment the reference count of the key by one, and
+ * return it in the bpf_key structure.
+ *
+ * The bpf_key structure must be passed to bpf_key_put() when done
+ * with it, so that the key reference count is decremented and the
+ * bpf_key structure is freed.
+ *
+ * Permission checks are deferred to the time the key is used by
+ * one of the available key-specific kfuncs.
+ *
+ * Set *flags* with KEY_LOOKUP_CREATE, to attempt creating a requested
+ * special keyring (e.g. session keyring), if it doesn't yet exist.
+ * Set *flags* with KEY_LOOKUP_PARTIAL, to lookup a key without waiting
+ * for the key construction, and to retrieve uninstantiated keys (keys
+ * without data attached to them).
+ *
+ * Return: a bpf_key pointer with a valid key pointer if the key is found, a
+ * NULL pointer otherwise.
+ */
+struct bpf_key *bpf_lookup_user_key(u32 serial, u64 flags)
+{
+ key_ref_t key_ref;
+ struct bpf_key *bkey;
+
+ if (flags & ~KEY_LOOKUP_ALL)
+ return NULL;
+
+ /*
+ * Permission check is deferred until the key is used, as the
+ * intent of the caller is unknown here.
+ */
+ key_ref = lookup_user_key(serial, flags, KEY_DEFER_PERM_CHECK);
+ if (IS_ERR(key_ref))
+ return NULL;
+
+ bkey = kmalloc(sizeof(*bkey), GFP_KERNEL);
+ if (!bkey) {
+ key_put(key_ref_to_ptr(key_ref));
+ return NULL;
+ }
+
+ bkey->key = key_ref_to_ptr(key_ref);
+ bkey->has_ref = true;
+
+ return bkey;
+}
+
+/**
+ * bpf_lookup_system_key - lookup a key by a system-defined ID
+ * @id: key ID
+ *
+ * Obtain a bpf_key structure with a key pointer set to the passed key ID.
+ * The key pointer is marked as invalid, to prevent bpf_key_put() from
+ * attempting to decrement the key reference count on that pointer. The key
+ * pointer set in such way is currently understood only by
+ * verify_pkcs7_signature().
+ *
+ * Set *id* to one of the values defined in include/linux/verification.h:
+ * 0 for the primary keyring (immutable keyring of system keys);
+ * VERIFY_USE_SECONDARY_KEYRING for both the primary and secondary keyring
+ * (where keys can be added only if they are vouched for by existing keys
+ * in those keyrings); VERIFY_USE_PLATFORM_KEYRING for the platform
+ * keyring (primarily used by the integrity subsystem to verify a kexec'ed
+ * kerned image and, possibly, the initramfs signature).
+ *
+ * Return: a bpf_key pointer with an invalid key pointer set from the
+ * pre-determined ID on success, a NULL pointer otherwise
+ */
+struct bpf_key *bpf_lookup_system_key(u64 id)
+{
+ struct bpf_key *bkey;
+
+ if (system_keyring_id_check(id) < 0)
+ return NULL;
+
+ bkey = kmalloc(sizeof(*bkey), GFP_ATOMIC);
+ if (!bkey)
+ return NULL;
+
+ bkey->key = (struct key *)(unsigned long)id;
+ bkey->has_ref = false;
+
+ return bkey;
+}
+
+/**
+ * bpf_key_put - decrement key reference count if key is valid and free bpf_key
+ * @bkey: bpf_key structure
+ *
+ * Decrement the reference count of the key inside *bkey*, if the pointer
+ * is valid, and free *bkey*.
+ */
+void bpf_key_put(struct bpf_key *bkey)
+{
+ if (bkey->has_ref)
+ key_put(bkey->key);
+
+ kfree(bkey);
+}
+
+__diag_pop();
+
+BTF_SET8_START(key_sig_kfunc_set)
+BTF_ID_FLAGS(func, bpf_lookup_user_key, KF_ACQUIRE | KF_RET_NULL | KF_SLEEPABLE)
+BTF_ID_FLAGS(func, bpf_lookup_system_key, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_key_put, KF_RELEASE)
+BTF_SET8_END(key_sig_kfunc_set)
+
+static const struct btf_kfunc_id_set bpf_key_sig_kfunc_set = {
+ .owner = THIS_MODULE,
+ .set = &key_sig_kfunc_set,
+};
+
+static int __init bpf_key_sig_kfuncs_init(void)
+{
+ return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
+ &bpf_key_sig_kfunc_set);
+}
+
+late_initcall(bpf_key_sig_kfuncs_init);
+#endif /* CONFIG_KEYS */
+
static const struct bpf_func_proto *
bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
--
2.25.1
From: Roberto Sassu <[email protected]>
Move dynptr type check to is_dynptr_type_expected() from
is_dynptr_reg_valid_init(), so that callers can better determine the cause
of a negative result (dynamic pointer not valid/initialized, dynamic
pointer of the wrong type). It will be useful for example for BTF, to
restrict which dynamic pointer types can be passed to kfuncs, as initially
only the local type will be supported.
Also, splitting makes the code more readable, since checking the dynamic
pointer type is not necessarily related to validity and initialization.
Split the validity/initialization and dynamic pointer type check also in
the verifier, and adjust the expected error message in the test (a test for
an unexpected dynptr type passed to a helper cannot be added due to missing
suitable helpers, but this case has been tested manually).
Cc: Joanne Koong <[email protected]>
Cc: Kumar Kartikeya Dwivedi <[email protected]>
Signed-off-by: Roberto Sassu <[email protected]>
Acked-by: Kumar Kartikeya Dwivedi <[email protected]>
---
kernel/bpf/verifier.c | 35 ++++++++++++++-----
.../testing/selftests/bpf/prog_tests/dynptr.c | 2 +-
2 files changed, 28 insertions(+), 9 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8c6fbcd0afaf..53dad321ac0b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -781,8 +781,8 @@ static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_
return true;
}
-static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
- enum bpf_arg_type arg_type)
+static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg)
{
struct bpf_func_state *state = func(env, reg);
int spi = get_spi(reg->off);
@@ -798,11 +798,24 @@ static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_re
return false;
}
+ return true;
+}
+
+static bool is_dynptr_type_expected(struct bpf_verifier_env *env,
+ struct bpf_reg_state *reg,
+ enum bpf_arg_type arg_type)
+{
+ struct bpf_func_state *state = func(env, reg);
+ enum bpf_dynptr_type dynptr_type;
+ int spi = get_spi(reg->off);
+
/* ARG_PTR_TO_DYNPTR takes any type of dynptr */
if (arg_type == ARG_PTR_TO_DYNPTR)
return true;
- return state->stack[spi].spilled_ptr.dynptr.type == arg_to_dynptr_type(arg_type);
+ dynptr_type = arg_to_dynptr_type(arg_type);
+
+ return state->stack[spi].spilled_ptr.dynptr.type == dynptr_type;
}
/* The reg state of a pointer or a bounded scalar was saved when
@@ -6081,21 +6094,27 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
}
meta->uninit_dynptr_regno = regno;
- } else if (!is_dynptr_reg_valid_init(env, reg, arg_type)) {
+ } else if (!is_dynptr_reg_valid_init(env, reg)) {
+ verbose(env,
+ "Expected an initialized dynptr as arg #%d\n",
+ arg + 1);
+ return -EINVAL;
+ } else if (!is_dynptr_type_expected(env, reg, arg_type)) {
const char *err_extra = "";
switch (arg_type & DYNPTR_TYPE_FLAG_MASK) {
case DYNPTR_TYPE_LOCAL:
- err_extra = "local ";
+ err_extra = "local";
break;
case DYNPTR_TYPE_RINGBUF:
- err_extra = "ringbuf ";
+ err_extra = "ringbuf";
break;
default:
+ err_extra = "<unknown>";
break;
}
-
- verbose(env, "Expected an initialized %sdynptr as arg #%d\n",
+ verbose(env,
+ "Expected a dynptr of type %s as arg #%d\n",
err_extra, arg + 1);
return -EINVAL;
}
diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index bcf80b9f7c27..8fc4e6c02bfd 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -30,7 +30,7 @@ static struct {
{"invalid_helper2", "Expected an initialized dynptr as arg #3"},
{"invalid_write1", "Expected an initialized dynptr as arg #1"},
{"invalid_write2", "Expected an initialized dynptr as arg #3"},
- {"invalid_write3", "Expected an initialized ringbuf dynptr as arg #1"},
+ {"invalid_write3", "Expected an initialized dynptr as arg #1"},
{"invalid_write4", "arg 1 is an unacquired reference"},
{"invalid_read1", "invalid read from stack"},
{"invalid_read2", "cannot pass in dynptr at an offset"},
--
2.25.1
Hello:
This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <[email protected]>:
On Tue, 20 Sep 2022 09:59:38 +0200 you wrote:
> From: Roberto Sassu <[email protected]>
>
> One of the desirable features in security is the ability to restrict import
> of data to a given system based on data authenticity. If data import can be
> restricted, it would be possible to enforce a system-wide policy based on
> the signing keys the system owner trusts.
>
> [...]
Here is the summary with links:
- [v18,01/13] bpf: Allow kfuncs to be used in LSM programs
https://git.kernel.org/bpf/bpf-next/c/d15bf1501c75
- [v18,02/13] btf: Export bpf_dynptr definition
https://git.kernel.org/bpf/bpf-next/c/00f146413ccb
- [v18,03/13] bpf: Move dynptr type check to is_dynptr_type_expected()
https://git.kernel.org/bpf/bpf-next/c/e9e315b4a5de
- [v18,04/13] btf: Allow dynamic pointer parameters in kfuncs
https://git.kernel.org/bpf/bpf-next/c/b8d31762a0ae
- [v18,05/13] bpf: Export bpf_dynptr_get_size()
https://git.kernel.org/bpf/bpf-next/c/51df48657185
- [v18,06/13] KEYS: Move KEY_LOOKUP_ to include/linux/key.h and define KEY_LOOKUP_ALL
https://git.kernel.org/bpf/bpf-next/c/90fd8f26edd4
- [v18,07/13] bpf: Add bpf_lookup_*_key() and bpf_key_put() kfuncs
https://git.kernel.org/bpf/bpf-next/c/f3cf4134c5c6
- [v18,08/13] bpf: Add bpf_verify_pkcs7_signature() kfunc
https://git.kernel.org/bpf/bpf-next/c/865b0566d8f1
- [v18,09/13] selftests/bpf: Compile kernel with everything as built-in
https://git.kernel.org/bpf/bpf-next/c/94fd7420faa0
- [v18,10/13] selftests/bpf: Add verifier tests for bpf_lookup_*_key() and bpf_key_put()
https://git.kernel.org/bpf/bpf-next/c/7c036ed9e006
- [v18,11/13] selftests/bpf: Add additional tests for bpf_lookup_*_key()
https://git.kernel.org/bpf/bpf-next/c/ecce368d6e6d
- [v18,12/13] selftests/bpf: Add test for bpf_verify_pkcs7_signature() kfunc
https://git.kernel.org/bpf/bpf-next/c/fc97590668ae
- [v18,13/13] selftests/bpf: Add tests for dynamic pointers parameters in kfuncs
https://git.kernel.org/bpf/bpf-next/c/b94fa9f9dcf9
You are awesome, thank you!
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