1 /* Copyright (c) 2015 PLUMgrid, http://plumgrid.com
2 *
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
6 */
7 #include <linux/ptrace.h>
8 #include <linux/version.h>
9 #include <uapi/linux/bpf.h>
10 #include <uapi/linux/seccomp.h>
11 #include "bpf_helpers.h"
12
13 #define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
14
15 struct bpf_map_def SEC("maps") progs = {
16 .type = BPF_MAP_TYPE_PROG_ARRAY,
17 .key_size = sizeof(u32),
18 .value_size = sizeof(u32),
19 .max_entries = 1024,
20 };
21
22 SEC("kprobe/seccomp_phase1")
bpf_prog1(struct pt_regs * ctx)23 int bpf_prog1(struct pt_regs *ctx)
24 {
25 struct seccomp_data sd = {};
26
27 bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
28
29 /* dispatch into next BPF program depending on syscall number */
30 bpf_tail_call(ctx, &progs, sd.nr);
31
32 /* fall through -> unknown syscall */
33 if (sd.nr >= __NR_getuid && sd.nr <= __NR_getsid) {
34 char fmt[] = "syscall=%d (one of get/set uid/pid/gid)\n";
35 bpf_trace_printk(fmt, sizeof(fmt), sd.nr);
36 }
37 return 0;
38 }
39
40 /* we jump here when syscall number == __NR_write */
PROG(__NR_write)41 PROG(__NR_write)(struct pt_regs *ctx)
42 {
43 struct seccomp_data sd = {};
44
45 bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
46 if (sd.args[2] == 512) {
47 char fmt[] = "write(fd=%d, buf=%p, size=%d)\n";
48 bpf_trace_printk(fmt, sizeof(fmt),
49 sd.args[0], sd.args[1], sd.args[2]);
50 }
51 return 0;
52 }
53
PROG(__NR_read)54 PROG(__NR_read)(struct pt_regs *ctx)
55 {
56 struct seccomp_data sd = {};
57
58 bpf_probe_read(&sd, sizeof(sd), (void *)PT_REGS_PARM1(ctx));
59 if (sd.args[2] > 128 && sd.args[2] <= 1024) {
60 char fmt[] = "read(fd=%d, buf=%p, size=%d)\n";
61 bpf_trace_printk(fmt, sizeof(fmt),
62 sd.args[0], sd.args[1], sd.args[2]);
63 }
64 return 0;
65 }
66
PROG(__NR_mmap)67 PROG(__NR_mmap)(struct pt_regs *ctx)
68 {
69 char fmt[] = "mmap\n";
70 bpf_trace_printk(fmt, sizeof(fmt));
71 return 0;
72 }
73
74 char _license[] SEC("license") = "GPL";
75 u32 _version SEC("version") = LINUX_VERSION_CODE;
76