[RFC PATCH security-next 4/4] selftests/hornet: Add a selftest for the hornet LSM

[Blaise Boscaccy <bboscaccy@linux.microsoft.com>]

This selftest tests contains a simple testcase that utilizes an lskel
loader. One version of the lskel is signed with the autogenerated
module signing key, another is not. A test driver attempts to load the
lskels. With hornet enabled, the signed version should successfully be
loaded, and the unsigned version should fail.

Signed-off-by: Blaise Boscaccy <bboscaccy@linux.microsoft.com>
---
 tools/testing/selftests/Makefile             |  1 +
 tools/testing/selftests/hornet/Makefile      | 51 ++++++++++++++++++++
 tools/testing/selftests/hornet/loader.c      | 21 ++++++++
 tools/testing/selftests/hornet/trivial.bpf.c | 33 +++++++++++++
 4 files changed, 106 insertions(+)
 create mode 100644 tools/testing/selftests/hornet/Makefile
 create mode 100644 tools/testing/selftests/hornet/loader.c
 create mode 100644 tools/testing/selftests/hornet/trivial.bpf.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 8daac70c2f9d2..fce32ee4de328 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -41,6 +41,7 @@ TARGETS += ftrace
 TARGETS += futex
 TARGETS += gpio
 TARGETS += hid
+TARGETS += hornet
 TARGETS += intel_pstate
 TARGETS += iommu
 TARGETS += ipc
diff --git a/tools/testing/selftests/hornet/Makefile b/tools/testing/selftests/hornet/Makefile
new file mode 100644
index 0000000000000..93da70f41d40c
--- /dev/null
+++ b/tools/testing/selftests/hornet/Makefile
@@ -0,0 +1,51 @@
+# SPDX-License-Identifier: GPL-2.0
+include ../../../build/Build.include
+include ../../../scripts/Makefile.arch
+include ../../../scripts/Makefile.include
+
+CLANG ?= clang
+CFLAGS := -g -O2 -Wall
+BPFTOOL ?= bpftool
+SCRIPTSDIR := $(abspath ../../../../scripts/hornet)
+TOOLSDIR := $(abspath ../../..)
+LIBDIR := $(TOOLSDIR)/lib
+BPFDIR := $(LIBDIR)/bpf
+TOOLSINCDIR := $(TOOLSDIR)/include
+APIDIR := $(TOOLSINCDIR)/uapi
+CERTDIR := $(abspath ../../../../certs)
+
+TEST_GEN_PROGS_EXTENDED := loader
+TEST_GEN_PROGS := signed_loader
+TEST_PROGS := fail_loader
+TEST_GEN_FILES := vmlinux.h loader.h trivial.bin trivial.bpf.o
+$(TEST_GEN_PROGS): LDLIBS += -lbpf
+$(TEST_GEN_PROGS): $(TEST_GEN_FILES)
+
+include ../lib.mk
+
+BPF_CFLAGS := -target bpf \
+              -D__TARGET_ARCH_$(ARCH) \
+              -I/usr/include/$(shell uname -m)-linux-gnu \
+               $(KHDR_INCLUDES)
+vmlinux.h:
+	$(BPFTOOL) btf dump file /sys/kernel/btf/vmlinux format c > vmlinux.h
+
+trivial.bpf.o: trivial.bpf.c vmlinux.h
+	$(CLANG) $(CFLAGS) $(BPF_CFLAGS) -c $< -o $@
+
+loader.h: trivial.bpf.o
+	$(BPFTOOL) gen skeleton -L $< name trivial > $@
+
+trivial.bin: loader.h
+	$(SCRIPTSDIR)/extract-skel.sh $< $@
+
+loader: loader.c loader.h
+	$(CC) $(CFLAGS) -I$(LIBDIR) -I$(APIDIR) $< -o $@ -lbpf
+
+fail_loader: fail_loader.c loader.h
+	$(CC) $(CFLAGS) -I$(LIBDIR) -I$(APIDIR) $< -o $@ -lbpf
+
+signed_loader: trivial.bin loader fail_loader
+	$(SCRIPTSDIR)/sign-ebpf sha256 $(CERTDIR)/signing_key.pem  $(CERTDIR)/signing_key.x509 \
+		trivial.bin loader signed_loader
+	chmod u+x $@
diff --git a/tools/testing/selftests/hornet/loader.c b/tools/testing/selftests/hornet/loader.c
new file mode 100644
index 0000000000000..9a43bb012d1b2
--- /dev/null
+++ b/tools/testing/selftests/hornet/loader.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stddef.h>
+#include <sys/resource.h>
+#include <bpf/libbpf.h>
+#include <errno.h>
+#include  "loader.h"
+
+int main(int argc, char **argv)
+{
+	struct trivial *skel;
+
+	skel = trivial__open_and_load();
+	if (!skel)
+		return -1;
+
+	trivial__destroy(skel);
+	return 0;
+}
diff --git a/tools/testing/selftests/hornet/trivial.bpf.c b/tools/testing/selftests/hornet/trivial.bpf.c
new file mode 100644
index 0000000000000..d38c5b53ff932
--- /dev/null
+++ b/tools/testing/selftests/hornet/trivial.bpf.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+char LICENSE[] SEC("license") = "Dual BSD/GPL";
+
+int monitored_pid = 0;
+
+SEC("tracepoint/syscalls/sys_enter_unlinkat")
+int handle_enter_unlink(struct trace_event_raw_sys_enter *ctx)
+{
+	char filename[128] = { 0 };
+	struct task_struct *task;
+	unsigned long start_time = 0;
+	int pid = bpf_get_current_pid_tgid() >> 32;
+	char *pathname_ptr = (char *) BPF_CORE_READ(ctx, args[1]);
+
+	bpf_probe_read_str(filename, sizeof(filename), pathname_ptr);
+	task = (struct task_struct *)bpf_get_current_task();
+	start_time = BPF_CORE_READ(task, start_time);
+
+	bpf_printk("BPF triggered unlinkat by PID: %d, start_time %ld. pathname = %s",
+		   pid, start_time, filename);
+
+	if (monitored_pid == pid)
+		bpf_printk("target pid found");
+
+	return 0;
+}
-- 
2.48.1