1 /*
2  * AppArmor security module
3  *
4  * This file contains AppArmor policy dfa matching engine definitions.
5  *
6  * Copyright (C) 1998-2008 Novell/SUSE
7  * Copyright 2009-2012 Canonical Ltd.
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License as
11  * published by the Free Software Foundation, version 2 of the
12  * License.
13  */
14 
15 #ifndef __AA_MATCH_H
16 #define __AA_MATCH_H
17 
18 #include <linux/kref.h>
19 
20 #define DFA_NOMATCH			0
21 #define DFA_START			1
22 
23 
24 /**
25  * The format used for transition tables is based on the GNU flex table
26  * file format (--tables-file option; see Table File Format in the flex
27  * info pages and the flex sources for documentation). The magic number
28  * used in the header is 0x1B5E783D instead of 0xF13C57B1 though, because
29  * new tables have been defined and others YY_ID_CHK (check) and YY_ID_DEF
30  * (default) tables are used slightly differently (see the apparmor-parser
31  * package).
32  *
33  *
34  * The data in the packed dfa is stored in network byte order, and the tables
35  * are arranged for flexibility.  We convert the table data to host native
36  * byte order.
37  *
38  * The dfa begins with a table set header, and is followed by the actual
39  * tables.
40  */
41 
42 #define YYTH_MAGIC	0x1B5E783D
43 #define YYTH_FLAG_DIFF_ENCODE	1
44 
45 struct table_set_header {
46 	u32 th_magic;		/* YYTH_MAGIC */
47 	u32 th_hsize;
48 	u32 th_ssize;
49 	u16 th_flags;
50 	char th_version[];
51 };
52 
53 /* The YYTD_ID are one less than flex table mappings.  The flex id
54  * has 1 subtracted at table load time, this allows us to directly use the
55  * ID's as indexes.
56  */
57 #define	YYTD_ID_ACCEPT	0
58 #define YYTD_ID_BASE	1
59 #define YYTD_ID_CHK	2
60 #define YYTD_ID_DEF	3
61 #define YYTD_ID_EC	4
62 #define YYTD_ID_META	5
63 #define YYTD_ID_ACCEPT2 6
64 #define YYTD_ID_NXT	7
65 #define YYTD_ID_TSIZE	8
66 #define YYTD_ID_MAX	8
67 
68 #define YYTD_DATA8	1
69 #define YYTD_DATA16	2
70 #define YYTD_DATA32	4
71 #define YYTD_DATA64	8
72 
73 /* ACCEPT & ACCEPT2 tables gets 6 dedicated flags, YYTD_DATAX define the
74  * first flags
75  */
76 #define ACCEPT1_FLAGS(X) ((X) & 0x3f)
77 #define ACCEPT2_FLAGS(X) ACCEPT1_FLAGS((X) >> YYTD_ID_ACCEPT2)
78 #define TO_ACCEPT1_FLAG(X) ACCEPT1_FLAGS(X)
79 #define TO_ACCEPT2_FLAG(X) (ACCEPT1_FLAGS(X) << YYTD_ID_ACCEPT2)
80 #define DFA_FLAG_VERIFY_STATES 0x1000
81 
82 struct table_header {
83 	u16 td_id;
84 	u16 td_flags;
85 	u32 td_hilen;
86 	u32 td_lolen;
87 	char td_data[];
88 };
89 
90 #define DEFAULT_TABLE(DFA) ((u16 *)((DFA)->tables[YYTD_ID_DEF]->td_data))
91 #define BASE_TABLE(DFA) ((u32 *)((DFA)->tables[YYTD_ID_BASE]->td_data))
92 #define NEXT_TABLE(DFA) ((u16 *)((DFA)->tables[YYTD_ID_NXT]->td_data))
93 #define CHECK_TABLE(DFA) ((u16 *)((DFA)->tables[YYTD_ID_CHK]->td_data))
94 #define EQUIV_TABLE(DFA) ((u8 *)((DFA)->tables[YYTD_ID_EC]->td_data))
95 #define ACCEPT_TABLE(DFA) ((u32 *)((DFA)->tables[YYTD_ID_ACCEPT]->td_data))
96 #define ACCEPT_TABLE2(DFA) ((u32 *)((DFA)->tables[YYTD_ID_ACCEPT2]->td_data))
97 
98 struct aa_dfa {
99 	struct kref count;
100 	u16 flags;
101 	struct table_header *tables[YYTD_ID_TSIZE];
102 };
103 
104 extern struct aa_dfa *nulldfa;
105 extern struct aa_dfa *stacksplitdfa;
106 
107 #define byte_to_byte(X) (X)
108 
109 #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX)	\
110 	do { \
111 		typeof(LEN) __i; \
112 		TTYPE *__t = (TTYPE *) TABLE; \
113 		BTYPE *__b = (BTYPE *) BLOB; \
114 		for (__i = 0; __i < LEN; __i++) { \
115 			__t[__i] = NTOHX(__b[__i]); \
116 		} \
117 	} while (0)
118 
119 static inline size_t table_size(size_t len, size_t el_size)
120 {
121 	return ALIGN(sizeof(struct table_header) + len * el_size, 8);
122 }
123 
124 int aa_setup_dfa_engine(void);
125 void aa_teardown_dfa_engine(void);
126 
127 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags);
128 unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
129 			      const char *str, int len);
130 unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
131 			  const char *str);
132 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
133 			 const char c);
134 unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int start,
135 				const char *str, const char **retpos);
136 unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start,
137 				 const char *str, int n, const char **retpos);
138 
139 void aa_dfa_free_kref(struct kref *kref);
140 
141 #define WB_HISTORY_SIZE 8
142 struct match_workbuf {
143 	unsigned int count;
144 	unsigned int pos;
145 	unsigned int len;
146 	unsigned int size;	/* power of 2, same as history size */
147 	unsigned int history[WB_HISTORY_SIZE];
148 };
149 #define DEFINE_MATCH_WB(N)		\
150 struct match_workbuf N = {		\
151 	.count = 0,			\
152 	.pos = 0,			\
153 	.len = 0,			\
154 	.size = WB_HISTORY_SIZE,			\
155 }
156 
157 unsigned int aa_dfa_leftmatch(struct aa_dfa *dfa, unsigned int start,
158 			      const char *str, unsigned int *count);
159 
160 /**
161  * aa_get_dfa - increment refcount on dfa @p
162  * @dfa: dfa  (MAYBE NULL)
163  *
164  * Returns: pointer to @dfa if @dfa is NULL will return NULL
165  * Requires: @dfa must be held with valid refcount when called
166  */
167 static inline struct aa_dfa *aa_get_dfa(struct aa_dfa *dfa)
168 {
169 	if (dfa)
170 		kref_get(&(dfa->count));
171 
172 	return dfa;
173 }
174 
175 /**
176  * aa_put_dfa - put a dfa refcount
177  * @dfa: dfa to put refcount   (MAYBE NULL)
178  *
179  * Requires: if @dfa != NULL that a valid refcount be held
180  */
181 static inline void aa_put_dfa(struct aa_dfa *dfa)
182 {
183 	if (dfa)
184 		kref_put(&dfa->count, aa_dfa_free_kref);
185 }
186 
187 #define MATCH_FLAG_DIFF_ENCODE 0x80000000
188 #define MARK_DIFF_ENCODE 0x40000000
189 
190 #endif /* __AA_MATCH_H */
191