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author | netblue30 <netblue30@yahoo.com> | 2018-01-02 09:08:12 -0500 |
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committer | netblue30 <netblue30@yahoo.com> | 2018-01-02 09:08:12 -0500 |
commit | e2ff818e3c4414ca19cc8533b1bc3b7afd755758 (patch) | |
tree | 6c07abe14e03926d7508b00c4e6ea882e0889d81 /src/fsec-optimize/optimizer.c | |
parent | Merge pull request #1710 from bitfreak25/master (diff) | |
download | firejail-e2ff818e3c4414ca19cc8533b1bc3b7afd755758.tar.gz firejail-e2ff818e3c4414ca19cc8533b1bc3b7afd755758.tar.zst firejail-e2ff818e3c4414ca19cc8533b1bc3b7afd755758.zip |
optimize default seccomp filters
Diffstat (limited to 'src/fsec-optimize/optimizer.c')
-rw-r--r-- | src/fsec-optimize/optimizer.c | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/src/fsec-optimize/optimizer.c b/src/fsec-optimize/optimizer.c new file mode 100644 index 000000000..8e61935d3 --- /dev/null +++ b/src/fsec-optimize/optimizer.c | |||
@@ -0,0 +1,136 @@ | |||
1 | /* | ||
2 | * Copyright (C) 2014-2017 Firejail Authors | ||
3 | * | ||
4 | * This file is part of firejail project | ||
5 | * | ||
6 | * This program is free software; you can redistribute it and/or modify | ||
7 | * it under the terms of the GNU General Public License as published by | ||
8 | * the Free Software Foundation; either version 2 of the License, or | ||
9 | * (at your option) any later version. | ||
10 | * | ||
11 | * This program is distributed in the hope that it will be useful, | ||
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
14 | * GNU General Public License for more details. | ||
15 | * | ||
16 | * You should have received a copy of the GNU General Public License along | ||
17 | * with this program; if not, write to the Free Software Foundation, Inc., | ||
18 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. | ||
19 | */ | ||
20 | #include "fsec_optimize.h" | ||
21 | |||
22 | // From /usr/include/linux/filter.h | ||
23 | //struct sock_filter { /* Filter block */ | ||
24 | // __u16 code; /* Actual filter code */ | ||
25 | // __u8 jt; /* Jump true */ | ||
26 | // __u8 jf; /* Jump false */ | ||
27 | // __u32 k; /* Generic multiuse field */ | ||
28 | //}; | ||
29 | |||
30 | |||
31 | #define LIMIT_BLACKLISTS 4 // we optimize blacklists only if we have more than | ||
32 | |||
33 | static inline int is_blacklist(struct sock_filter *bpf) { | ||
34 | if (bpf->code == BPF_JMP + BPF_JEQ + BPF_K && | ||
35 | (bpf + 1)->code == BPF_RET + BPF_K && | ||
36 | (bpf + 1)->k == SECCOMP_RET_KILL ) | ||
37 | return 1; | ||
38 | return 0; | ||
39 | } | ||
40 | |||
41 | static int count_blacklists(struct sock_filter *filter, int entries) { | ||
42 | int cnt = 0; | ||
43 | int i; | ||
44 | |||
45 | for (i = 0; i < (entries - 1); i++, filter++) { // is_blacklist works on two consecutive lines; using entries - 1 | ||
46 | if (is_blacklist(filter)) | ||
47 | cnt++; | ||
48 | } | ||
49 | |||
50 | return cnt; | ||
51 | } | ||
52 | |||
53 | typedef struct { | ||
54 | int to_remove; | ||
55 | int to_fix_jumps; | ||
56 | } Action; | ||
57 | |||
58 | static int optimize_blacklists(struct sock_filter *filter, int entries) { | ||
59 | assert(entries); | ||
60 | assert(filter); | ||
61 | int i; | ||
62 | int j; | ||
63 | |||
64 | // step1: extract information | ||
65 | Action action[entries]; | ||
66 | memset(&action[0], 0, sizeof(Action) * entries); | ||
67 | int remove_cnt = 0; | ||
68 | for (i = 0; i < (entries - 1); i++) { // is_blacklist works on two consecutive lines; using entries - 1 | ||
69 | if (is_blacklist(filter + i)) { | ||
70 | action[i]. to_fix_jumps = 1; | ||
71 | i++; | ||
72 | action[i].to_remove = 1; | ||
73 | remove_cnt++; | ||
74 | } | ||
75 | } | ||
76 | |||
77 | // step2: remove lines | ||
78 | struct sock_filter *filter_step2 = duplicate(filter, entries); | ||
79 | Action action_step2[entries]; | ||
80 | memset(&action_step2[0], 0, sizeof(Action) * entries); | ||
81 | for (i = 0, j = 0; i < entries; i++) { | ||
82 | if (!action[i].to_remove) { | ||
83 | memcpy(&filter_step2[j], &filter[i], sizeof(struct sock_filter)); | ||
84 | memcpy(&action_step2[j], &action[i], sizeof(Action)); | ||
85 | j++; | ||
86 | } | ||
87 | else { | ||
88 | // do nothing, we are removing this line | ||
89 | } | ||
90 | } | ||
91 | |||
92 | // step 3: add the new ret KILL, and recalculate entries | ||
93 | filter_step2[j].code = BPF_RET + BPF_K; | ||
94 | filter_step2[j].k == SECCOMP_RET_KILL; | ||
95 | entries = j + 1; | ||
96 | |||
97 | // step 4: recalculate jumps | ||
98 | for (i = 0; i < entries; i++) { | ||
99 | if (action_step2[i].to_fix_jumps) { | ||
100 | filter_step2[i].jt = entries - i - 2; | ||
101 | filter_step2[i].jf = 0; | ||
102 | } | ||
103 | } | ||
104 | |||
105 | // update | ||
106 | memcpy(filter, filter_step2, entries * sizeof(struct sock_filter)); | ||
107 | free(filter_step2); | ||
108 | return entries; | ||
109 | } | ||
110 | |||
111 | int optimize(struct sock_filter *filter, int entries) { | ||
112 | assert(filter); | ||
113 | assert(entries); | ||
114 | |||
115 | //********************************** | ||
116 | // optimize blacklist statements | ||
117 | //********************************** | ||
118 | // count "ret KILL" | ||
119 | int cnt = count_blacklists(filter, entries); | ||
120 | if (cnt > LIMIT_BLACKLISTS) | ||
121 | entries = optimize_blacklists(filter, entries); | ||
122 | return entries; | ||
123 | } | ||
124 | |||
125 | struct sock_filter *duplicate(struct sock_filter *filter, int entries) { | ||
126 | int len = sizeof(struct sock_filter) * entries; | ||
127 | struct sock_filter *rv = malloc(len); | ||
128 | if (!rv) { | ||
129 | errExit("malloc"); | ||
130 | exit(1); | ||
131 | } | ||
132 | |||
133 | memcpy(rv, filter, len); | ||
134 | return rv; | ||
135 | } | ||
136 | |||