1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * AppArmor security module
4  *
5  * This file contains AppArmor policy dfa matching engine definitions.
6  *
7  * Copyright (C) 1998-2008 Novell/SUSE
8  * Copyright 2009-2012 Canonical Ltd.
9  */
10 
11 #ifndef __AA_MATCH_H
12 #define __AA_MATCH_H
13 
14 #include <linux/kref.h>
15 
16 #define DFA_NOMATCH			0
17 #define DFA_START			1
18 
19 
20 /**
21  * The format used for transition tables is based on the GNU flex table
22  * file format (--tables-file option; see Table File Format in the flex
23  * info pages and the flex sources for documentation). The magic number
24  * used in the header is 0x1B5E783D instead of 0xF13C57B1 though, because
25  * new tables have been defined and others YY_ID_CHK (check) and YY_ID_DEF
26  * (default) tables are used slightly differently (see the apparmor-parser
27  * package).
28  *
29  *
30  * The data in the packed dfa is stored in network byte order, and the tables
31  * are arranged for flexibility.  We convert the table data to host native
32  * byte order.
33  *
34  * The dfa begins with a table set header, and is followed by the actual
35  * tables.
36  */
37 
38 #define YYTH_MAGIC	0x1B5E783D
39 #define YYTH_FLAG_DIFF_ENCODE	1
40 
41 struct table_set_header {
42 	u32 th_magic;		/* YYTH_MAGIC */
43 	u32 th_hsize;
44 	u32 th_ssize;
45 	u16 th_flags;
46 	char th_version[];
47 };
48 
49 /* The YYTD_ID are one less than flex table mappings.  The flex id
50  * has 1 subtracted at table load time, this allows us to directly use the
51  * ID's as indexes.
52  */
53 #define	YYTD_ID_ACCEPT	0
54 #define YYTD_ID_BASE	1
55 #define YYTD_ID_CHK	2
56 #define YYTD_ID_DEF	3
57 #define YYTD_ID_EC	4
58 #define YYTD_ID_META	5
59 #define YYTD_ID_ACCEPT2 6
60 #define YYTD_ID_NXT	7
61 #define YYTD_ID_TSIZE	8
62 #define YYTD_ID_MAX	8
63 
64 #define YYTD_DATA8	1
65 #define YYTD_DATA16	2
66 #define YYTD_DATA32	4
67 #define YYTD_DATA64	8
68 
69 /* ACCEPT & ACCEPT2 tables gets 6 dedicated flags, YYTD_DATAX define the
70  * first flags
71  */
72 #define ACCEPT1_FLAGS(X) ((X) & 0x3f)
73 #define ACCEPT2_FLAGS(X) ACCEPT1_FLAGS((X) >> YYTD_ID_ACCEPT2)
74 #define TO_ACCEPT1_FLAG(X) ACCEPT1_FLAGS(X)
75 #define TO_ACCEPT2_FLAG(X) (ACCEPT1_FLAGS(X) << YYTD_ID_ACCEPT2)
76 #define DFA_FLAG_VERIFY_STATES 0x1000
77 
78 struct table_header {
79 	u16 td_id;
80 	u16 td_flags;
81 	u32 td_hilen;
82 	u32 td_lolen;
83 	char td_data[];
84 };
85 
86 #define DEFAULT_TABLE(DFA) ((u16 *)((DFA)->tables[YYTD_ID_DEF]->td_data))
87 #define BASE_TABLE(DFA) ((u32 *)((DFA)->tables[YYTD_ID_BASE]->td_data))
88 #define NEXT_TABLE(DFA) ((u16 *)((DFA)->tables[YYTD_ID_NXT]->td_data))
89 #define CHECK_TABLE(DFA) ((u16 *)((DFA)->tables[YYTD_ID_CHK]->td_data))
90 #define EQUIV_TABLE(DFA) ((u8 *)((DFA)->tables[YYTD_ID_EC]->td_data))
91 #define ACCEPT_TABLE(DFA) ((u32 *)((DFA)->tables[YYTD_ID_ACCEPT]->td_data))
92 #define ACCEPT_TABLE2(DFA) ((u32 *)((DFA)->tables[YYTD_ID_ACCEPT2]->td_data))
93 
94 struct aa_dfa {
95 	struct kref count;
96 	u16 flags;
97 	struct table_header *tables[YYTD_ID_TSIZE];
98 };
99 
100 extern struct aa_dfa *nulldfa;
101 extern struct aa_dfa *stacksplitdfa;
102 
103 #define byte_to_byte(X) (X)
104 
105 #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX)	\
106 	do { \
107 		typeof(LEN) __i; \
108 		TTYPE *__t = (TTYPE *) TABLE; \
109 		BTYPE *__b = (BTYPE *) BLOB; \
110 		for (__i = 0; __i < LEN; __i++) { \
111 			__t[__i] = NTOHX(__b[__i]); \
112 		} \
113 	} while (0)
114 
115 static inline size_t table_size(size_t len, size_t el_size)
116 {
117 	return ALIGN(sizeof(struct table_header) + len * el_size, 8);
118 }
119 
120 int aa_setup_dfa_engine(void);
121 void aa_teardown_dfa_engine(void);
122 
123 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags);
124 unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
125 			      const char *str, int len);
126 unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
127 			  const char *str);
128 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
129 			 const char c);
130 unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int start,
131 				const char *str, const char **retpos);
132 unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start,
133 				 const char *str, int n, const char **retpos);
134 
135 void aa_dfa_free_kref(struct kref *kref);
136 
137 #define WB_HISTORY_SIZE 24
138 struct match_workbuf {
139 	unsigned int count;
140 	unsigned int pos;
141 	unsigned int len;
142 	unsigned int size;	/* power of 2, same as history size */
143 	unsigned int history[WB_HISTORY_SIZE];
144 };
145 #define DEFINE_MATCH_WB(N)		\
146 struct match_workbuf N = {		\
147 	.count = 0,			\
148 	.pos = 0,			\
149 	.len = 0,			\
150 }
151 
152 unsigned int aa_dfa_leftmatch(struct aa_dfa *dfa, unsigned int start,
153 			      const char *str, unsigned int *count);
154 
155 /**
156  * aa_get_dfa - increment refcount on dfa @p
157  * @dfa: dfa  (MAYBE NULL)
158  *
159  * Returns: pointer to @dfa if @dfa is NULL will return NULL
160  * Requires: @dfa must be held with valid refcount when called
161  */
162 static inline struct aa_dfa *aa_get_dfa(struct aa_dfa *dfa)
163 {
164 	if (dfa)
165 		kref_get(&(dfa->count));
166 
167 	return dfa;
168 }
169 
170 /**
171  * aa_put_dfa - put a dfa refcount
172  * @dfa: dfa to put refcount   (MAYBE NULL)
173  *
174  * Requires: if @dfa != NULL that a valid refcount be held
175  */
176 static inline void aa_put_dfa(struct aa_dfa *dfa)
177 {
178 	if (dfa)
179 		kref_put(&dfa->count, aa_dfa_free_kref);
180 }
181 
182 #define MATCH_FLAG_DIFF_ENCODE 0x80000000
183 #define MARK_DIFF_ENCODE 0x40000000
184 
185 #endif /* __AA_MATCH_H */
186