104 lines · c
1// SPDX-License-Identifier: GPL-2.02 3/*4 * Copyright 2020 Google LLC.5 */6 7#include "vmlinux.h"8#include <errno.h>9#include <bpf/bpf_helpers.h>10#include <bpf/bpf_tracing.h>11 12u32 monitored_pid = 0;13 14struct {15 __uint(type, BPF_MAP_TYPE_RINGBUF);16 __uint(max_entries, 1 << 12);17} ringbuf SEC(".maps");18 19char _license[] SEC("license") = "GPL";20 21bool use_ima_file_hash;22bool enable_bprm_creds_for_exec;23bool enable_kernel_read_file;24bool test_deny;25 26static void ima_test_common(struct file *file)27{28 u64 ima_hash = 0;29 u64 *sample;30 int ret;31 u32 pid;32 33 pid = bpf_get_current_pid_tgid() >> 32;34 if (pid == monitored_pid) {35 if (!use_ima_file_hash)36 ret = bpf_ima_inode_hash(file->f_inode, &ima_hash,37 sizeof(ima_hash));38 else39 ret = bpf_ima_file_hash(file, &ima_hash,40 sizeof(ima_hash));41 if (ret < 0 || ima_hash == 0)42 return;43 44 sample = bpf_ringbuf_reserve(&ringbuf, sizeof(u64), 0);45 if (!sample)46 return;47 48 *sample = ima_hash;49 bpf_ringbuf_submit(sample, 0);50 }51 52 return;53}54 55static int ima_test_deny(void)56{57 u32 pid;58 59 pid = bpf_get_current_pid_tgid() >> 32;60 if (pid == monitored_pid && test_deny)61 return -EPERM;62 63 return 0;64}65 66SEC("lsm.s/bprm_committed_creds")67void BPF_PROG(bprm_committed_creds, struct linux_binprm *bprm)68{69 ima_test_common(bprm->file);70}71 72SEC("lsm.s/bprm_creds_for_exec")73int BPF_PROG(bprm_creds_for_exec, struct linux_binprm *bprm)74{75 if (!enable_bprm_creds_for_exec)76 return 0;77 78 ima_test_common(bprm->file);79 return 0;80}81 82SEC("lsm.s/kernel_read_file")83int BPF_PROG(kernel_read_file, struct file *file, enum kernel_read_file_id id,84 bool contents)85{86 int ret;87 88 if (!enable_kernel_read_file)89 return 0;90 91 if (!contents)92 return 0;93 94 if (id != READING_POLICY)95 return 0;96 97 ret = ima_test_deny();98 if (ret < 0)99 return ret;100 101 ima_test_common(file);102 return 0;103}104