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 15 #define MAX_DATA_SIZE (1024 * 1024) 16 #define MAX_SIG_SIZE 1024 17 18 __u32 monitored_pid; 19 __u32 user_keyring_serial; 20 __u64 system_keyring_id; 21 22 struct data { 23 __u8 data[MAX_DATA_SIZE]; 24 __u32 data_len; 25 __u8 sig[MAX_SIG_SIZE]; 26 __u32 sig_len; 27 }; 28 29 struct { 30 __uint(type, BPF_MAP_TYPE_ARRAY); 31 __uint(max_entries, 1); 32 __type(key, __u32); 33 __type(value, struct data); 34 } data_input SEC(".maps"); 35 36 char _license[] SEC("license") = "GPL"; 37 38 SEC("lsm.s/bpf") 39 int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size) 40 { 41 struct bpf_dynptr data_ptr, sig_ptr; 42 struct data *data_val; 43 struct bpf_key *trusted_keyring; 44 __u32 pid; 45 __u64 value; 46 int ret, zero = 0; 47 48 pid = bpf_get_current_pid_tgid() >> 32; 49 if (pid != monitored_pid) 50 return 0; 51 52 data_val = bpf_map_lookup_elem(&data_input, &zero); 53 if (!data_val) 54 return 0; 55 56 ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value); 57 if (ret) 58 return ret; 59 60 ret = bpf_copy_from_user(data_val, sizeof(struct data), 61 (void *)(unsigned long)value); 62 if (ret) 63 return ret; 64 65 if (data_val->data_len > sizeof(data_val->data)) 66 return -EINVAL; 67 68 bpf_dynptr_from_mem(data_val->data, data_val->data_len, 0, &data_ptr); 69 70 if (data_val->sig_len > sizeof(data_val->sig)) 71 return -EINVAL; 72 73 bpf_dynptr_from_mem(data_val->sig, data_val->sig_len, 0, &sig_ptr); 74 75 if (user_keyring_serial) 76 trusted_keyring = bpf_lookup_user_key(user_keyring_serial, 0); 77 else 78 trusted_keyring = bpf_lookup_system_key(system_keyring_id); 79 80 if (!trusted_keyring) 81 return -ENOENT; 82 83 ret = bpf_verify_pkcs7_signature(&data_ptr, &sig_ptr, trusted_keyring); 84 85 bpf_key_put(trusted_keyring); 86 87 return ret; 88 } 89