1 // SPDX-License-Identifier: GPL-2.0 2 3 /* 4 * Copyright (C) 2022 Huawei Technologies Duesseldorf GmbH 5 * 6 * Author: Roberto Sassu <roberto.sassu@huawei.com> 7 */ 8 9 #include "vmlinux.h" 10 #include <errno.h> 11 #include <bpf/bpf_helpers.h> 12 #include <bpf/bpf_tracing.h> 13 #include "bpf_kfuncs.h" 14 #include "err.h" 15 16 #define MAX_DATA_SIZE (1024 * 1024) 17 #define MAX_SIG_SIZE 1024 18 19 __u32 monitored_pid; 20 __u32 user_keyring_serial; 21 __u64 system_keyring_id; 22 23 struct data { 24 __u8 data[MAX_DATA_SIZE]; 25 __u32 data_len; 26 __u8 sig[MAX_SIG_SIZE]; 27 __u32 sig_len; 28 }; 29 30 struct { 31 __uint(type, BPF_MAP_TYPE_ARRAY); 32 __uint(max_entries, 1); 33 __type(key, __u32); 34 __type(value, struct data); 35 } data_input SEC(".maps"); 36 37 char _license[] SEC("license") = "GPL"; 38 39 SEC("lsm.s/bpf") 40 int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size) 41 { 42 struct bpf_dynptr data_ptr, sig_ptr; 43 struct data *data_val; 44 struct bpf_key *trusted_keyring; 45 __u32 pid; 46 __u64 value; 47 int ret, zero = 0; 48 49 pid = bpf_get_current_pid_tgid() >> 32; 50 if (pid != monitored_pid) 51 return 0; 52 53 data_val = bpf_map_lookup_elem(&data_input, &zero); 54 if (!data_val) 55 return 0; 56 57 ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value); 58 if (ret) 59 goto out; 60 61 ret = bpf_copy_from_user(data_val, sizeof(struct data), 62 (void *)(unsigned long)value); 63 if (ret) 64 goto out; 65 66 if (data_val->data_len > sizeof(data_val->data)) 67 return -EINVAL; 68 69 bpf_dynptr_from_mem(data_val->data, data_val->data_len, 0, &data_ptr); 70 71 if (data_val->sig_len > sizeof(data_val->sig)) 72 return -EINVAL; 73 74 bpf_dynptr_from_mem(data_val->sig, data_val->sig_len, 0, &sig_ptr); 75 76 if (user_keyring_serial) 77 trusted_keyring = bpf_lookup_user_key(user_keyring_serial, 0); 78 else 79 trusted_keyring = bpf_lookup_system_key(system_keyring_id); 80 81 if (!trusted_keyring) 82 return -ENOENT; 83 84 ret = bpf_verify_pkcs7_signature(&data_ptr, &sig_ptr, trusted_keyring); 85 86 bpf_key_put(trusted_keyring); 87 88 out: 89 set_if_not_errno_or_zero(ret, -EFAULT); 90 91 return ret; 92 } 93