1 /*
2  * Copyright (c) 2015 Dmitry V. Levin <ldv@altlinux.org>
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. The name of the author may not be used to endorse or promote products
14  *    derived from this software without specific prior written permission.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26  */
27 
28 #include "defs.h"
29 
30 #ifdef HAVE_LINUX_SECCOMP_H
31 # include <linux/seccomp.h>
32 #endif
33 #include "xlat/seccomp_ops.h"
34 #include "xlat/seccomp_filter_flags.h"
35 
36 #ifdef HAVE_LINUX_FILTER_H
37 # include <linux/filter.h>
38 # include "xlat/bpf_class.h"
39 # include "xlat/bpf_miscop.h"
40 # include "xlat/bpf_mode.h"
41 # include "xlat/bpf_op_alu.h"
42 # include "xlat/bpf_op_jmp.h"
43 # include "xlat/bpf_rval.h"
44 # include "xlat/bpf_size.h"
45 # include "xlat/bpf_src.h"
46 
47 # ifndef SECCOMP_RET_ACTION
48 #  define SECCOMP_RET_ACTION 0x7fff0000U
49 # endif
50 # include "xlat/seccomp_ret_action.h"
51 #endif
52 
53 struct bpf_filter {
54 	uint16_t code;
55 	uint8_t jt;
56 	uint8_t jf;
57 	uint32_t k;
58 };
59 
60 #ifdef HAVE_LINUX_FILTER_H
61 
62 static void
decode_bpf_code(uint16_t code)63 decode_bpf_code(uint16_t code)
64 {
65 	uint16_t i = code & ~BPF_CLASS(code);
66 
67 	printxval(bpf_class, BPF_CLASS(code), "BPF_???");
68 	switch (BPF_CLASS(code)) {
69 		case BPF_LD:
70 		case BPF_LDX:
71 			tprints(" | ");
72 			printxval(bpf_size, BPF_SIZE(code), "BPF_???");
73 			tprints(" | ");
74 			printxval(bpf_mode, BPF_MODE(code), "BPF_???");
75 			break;
76 		case BPF_ST:
77 		case BPF_STX:
78 			if (i)
79 				tprintf(" | %#x /* %s */", i, "BPF_???");
80 			break;
81 		case BPF_ALU:
82 			tprints(" | ");
83 			printxval(bpf_src, BPF_SRC(code), "BPF_???");
84 			tprints(" | ");
85 			printxval(bpf_op_alu, BPF_OP(code), "BPF_???");
86 			break;
87 		case BPF_JMP:
88 			tprints(" | ");
89 			printxval(bpf_src, BPF_SRC(code), "BPF_???");
90 			tprints(" | ");
91 			printxval(bpf_op_jmp, BPF_OP(code), "BPF_???");
92 			break;
93 		case BPF_RET:
94 			tprints(" | ");
95 			printxval(bpf_rval, BPF_RVAL(code), "BPF_???");
96 			i &= ~BPF_RVAL(code);
97 			if (i)
98 				tprintf(" | %#x /* %s */", i, "BPF_???");
99 			break;
100 		case BPF_MISC:
101 			tprints(" | ");
102 			printxval(bpf_miscop, BPF_MISCOP(code), "BPF_???");
103 			i &= ~BPF_MISCOP(code);
104 			if (i)
105 				tprintf(" | %#x /* %s */", i, "BPF_???");
106 			break;
107 	}
108 
109 }
110 
111 static void
decode_bpf_stmt(const struct bpf_filter * filter)112 decode_bpf_stmt(const struct bpf_filter *filter)
113 {
114 #ifdef HAVE_LINUX_FILTER_H
115 	tprints("BPF_STMT(");
116 	decode_bpf_code(filter->code);
117 	tprints(", ");
118 	if (BPF_CLASS(filter->code) == BPF_RET) {
119 		unsigned int action = SECCOMP_RET_ACTION & filter->k;
120 		unsigned int data = filter->k & ~action;
121 
122 		printxval(seccomp_ret_action, action, "SECCOMP_RET_???");
123 		if (data)
124 			tprintf(" | %#x)", data);
125 		else
126 			tprints(")");
127 	} else {
128 		tprintf("%#x)", filter->k);
129 	}
130 #else
131 	tprintf("BPF_STMT(%#x, %#x)", filter->code, filter->k);
132 #endif /* HAVE_LINUX_FILTER_H */
133 }
134 
135 static void
decode_bpf_jump(const struct bpf_filter * filter)136 decode_bpf_jump(const struct bpf_filter *filter)
137 {
138 #ifdef HAVE_LINUX_FILTER_H
139 	tprints("BPF_JUMP(");
140 	decode_bpf_code(filter->code);
141 	tprintf(", %#x, %#x, %#x)",
142 		filter->k, filter->jt, filter->jf);
143 #else
144 	tprintf("BPF_JUMP(%#x, %#x, %#x, %#x)",
145 		filter->code, filter->k, filter->jt, filter->jf);
146 #endif /* HAVE_LINUX_FILTER_H */
147 }
148 
149 static void
decode_filter(const struct bpf_filter * filter)150 decode_filter(const struct bpf_filter *filter)
151 {
152 	if (filter->jt || filter->jf)
153 		decode_bpf_jump(filter);
154 	else
155 		decode_bpf_stmt(filter);
156 }
157 
158 #endif /* HAVE_LINUX_FILTER_H */
159 
160 #ifndef BPF_MAXINSNS
161 # define BPF_MAXINSNS 4096
162 #endif
163 
164 static void
decode_fprog(struct tcb * tcp,unsigned short len,unsigned long addr)165 decode_fprog(struct tcb *tcp, unsigned short len, unsigned long addr)
166 {
167 	if (!len || abbrev(tcp)) {
168 		tprintf("{len = %u, filter = %#lx}", len, addr);
169 	} else {
170 		unsigned int i = 0;
171 
172 		tprints("[");
173 		while (i < len && i < BPF_MAXINSNS) {
174 			struct bpf_filter filter;
175 
176 			if (umove(tcp, addr, &filter) < 0)
177 				break;
178 			if (i)
179 				tprints(", ");
180 			decode_filter(&filter);
181 
182 			addr += sizeof(filter);
183 			++i;
184 		}
185 		if (i < len)
186 			tprints("...");
187 		tprints("]");
188 	}
189 }
190 
191 void
print_seccomp_filter(struct tcb * tcp,unsigned long addr)192 print_seccomp_filter(struct tcb *tcp, unsigned long addr)
193 {
194 	if (addr) {
195 #if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
196 		if (current_wordsize == 4) {
197 			struct {
198 				unsigned short len;
199 				uint32_t filter;
200 			} fprog;
201 			if (umove(tcp, addr, &fprog) < 0)
202 				tprintf("%#lx", addr);
203 			else
204 				decode_fprog(tcp, fprog.len, fprog.filter);
205 		} else {
206 #endif
207 			struct {
208 				unsigned short len;
209 				unsigned long filter;
210 			} fprog;
211 			if (umove(tcp, addr, &fprog) < 0)
212 				tprintf("%#lx", addr);
213 			else
214 				decode_fprog(tcp, fprog.len, fprog.filter);
215 #if SUPPORTED_PERSONALITIES > 1 && SIZEOF_LONG > 4
216 		}
217 #endif
218 	} else {
219 		tprints("NULL");
220 	}
221 }
222 
223 static void
decode_seccomp_set_mode_strict(unsigned int flags,unsigned long addr)224 decode_seccomp_set_mode_strict(unsigned int flags, unsigned long addr)
225 {
226 	tprintf("%u, ", flags);
227 	if (addr)
228 		tprintf("%#lx", addr);
229 	else
230 		tprints("NULL");
231 }
232 
SYS_FUNC(seccomp)233 SYS_FUNC(seccomp)
234 {
235 	if (entering(tcp)) {
236 		unsigned int op = tcp->u_arg[0];
237 
238 		printxval(seccomp_ops, op, "SECCOMP_SET_MODE_???");
239 		tprints(", ");
240 
241 		if (op == SECCOMP_SET_MODE_FILTER) {
242 			printflags(seccomp_filter_flags, tcp->u_arg[1],
243 				   "SECCOMP_FILTER_FLAG_???");
244 			tprints(", ");
245 			print_seccomp_filter(tcp, tcp->u_arg[2]);
246 		} else {
247 			decode_seccomp_set_mode_strict(tcp->u_arg[1],
248 						       tcp->u_arg[2]);
249 		}
250 	}
251 	return 0;
252 }
253