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 14 #define MAX_DATA_SIZE (1024 * 1024) 15 #define MAX_SIG_SIZE 1024 16 17 extern struct bpf_key *bpf_lookup_user_key(__u32 serial, __u64 flags) __ksym; 18 extern struct bpf_key *bpf_lookup_system_key(__u64 id) __ksym; 19 extern void bpf_key_put(struct bpf_key *key) __ksym; 20 extern int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_ptr, 21 struct bpf_dynptr *sig_ptr, 22 struct bpf_key *trusted_keyring) __ksym; 23 24 __u32 monitored_pid; 25 __u32 user_keyring_serial; 26 __u64 system_keyring_id; 27 28 struct data { 29 __u8 data[MAX_DATA_SIZE]; 30 __u32 data_len; 31 __u8 sig[MAX_SIG_SIZE]; 32 __u32 sig_len; 33 }; 34 35 struct { 36 __uint(type, BPF_MAP_TYPE_ARRAY); 37 __uint(max_entries, 1); 38 __type(key, __u32); 39 __type(value, struct data); 40 } data_input SEC(".maps"); 41 42 char _license[] SEC("license") = "GPL"; 43 44 SEC("lsm.s/bpf") 45 int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size) 46 { 47 struct bpf_dynptr data_ptr, sig_ptr; 48 struct data *data_val; 49 struct bpf_key *trusted_keyring; 50 __u32 pid; 51 __u64 value; 52 int ret, zero = 0; 53 54 pid = bpf_get_current_pid_tgid() >> 32; 55 if (pid != monitored_pid) 56 return 0; 57 58 data_val = bpf_map_lookup_elem(&data_input, &zero); 59 if (!data_val) 60 return 0; 61 62 bpf_probe_read(&value, sizeof(value), &attr->value); 63 64 bpf_copy_from_user(data_val, sizeof(struct data), 65 (void *)(unsigned long)value); 66 67 if (data_val->data_len > sizeof(data_val->data)) 68 return -EINVAL; 69 70 bpf_dynptr_from_mem(data_val->data, data_val->data_len, 0, &data_ptr); 71 72 if (data_val->sig_len > sizeof(data_val->sig)) 73 return -EINVAL; 74 75 bpf_dynptr_from_mem(data_val->sig, data_val->sig_len, 0, &sig_ptr); 76 77 if (user_keyring_serial) 78 trusted_keyring = bpf_lookup_user_key(user_keyring_serial, 0); 79 else 80 trusted_keyring = bpf_lookup_system_key(system_keyring_id); 81 82 if (!trusted_keyring) 83 return -ENOENT; 84 85 ret = bpf_verify_pkcs7_signature(&data_ptr, &sig_ptr, trusted_keyring); 86 87 bpf_key_put(trusted_keyring); 88 89 return ret; 90 } 91