summaryrefslogtreecommitdiff
path: root/src/libstrongswan/utils/integrity_checker.c
blob: d39b587a9b0431049f89604d743d710d5e8ed10c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
/*
 * Copyright (C) 2009 Martin Willi
 * HSR Hochschule fuer Technik Rapperswil
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 */

#define _GNU_SOURCE

#include "integrity_checker.h"

#include <dlfcn.h>
#include <link.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

#include "debug.h"
#include "library.h"

typedef struct private_integrity_checker_t private_integrity_checker_t;

/**
 * Private data of an integrity_checker_t object.
 */
struct private_integrity_checker_t {

	/**
	 * Public integrity_checker_t interface.
	 */
	integrity_checker_t public;

	/**
	 * dlopen handle to checksum library
	 */
	void *handle;

	/**
	 * checksum array
	 */
	integrity_checksum_t *checksums;

	/**
	 * number of checksums in array
	 */
	int checksum_count;
};

METHOD(integrity_checker_t, build_file, uint32_t,
	private_integrity_checker_t *this, char *file, size_t *len)
{
	uint32_t checksum;
	chunk_t *contents;

	contents = chunk_map(file, FALSE);
	if (!contents)
	{
		DBG1(DBG_LIB, "  opening '%s' failed: %s", file, strerror(errno));
		return 0;
	}
	*len = contents->len;
	checksum = chunk_hash_static(*contents);
	chunk_unmap(contents);

	return checksum;
}

/**
 * dl_iterate_phdr callback function
 */
static int callback(struct dl_phdr_info *dlpi, size_t size, Dl_info *dli)
{
	/* We are looking for the dlpi_addr matching the address of our dladdr().
	 * dl_iterate_phdr() returns such an address for other (unknown) objects
	 * in very rare cases (e.g. in a chrooted gentoo, but only if
	 * the checksum_builder is invoked by 'make'). As a workaround, we filter
	 * objects by dlpi_name; valid objects have a library name.
	 */
	if (dli->dli_fbase == (void*)dlpi->dlpi_addr &&
		dlpi->dlpi_name && *dlpi->dlpi_name)
	{
		int i;

		for (i = 0; i < dlpi->dlpi_phnum; i++)
		{
			const ElfW(Phdr) *sgmt = &dlpi->dlpi_phdr[i];

			/* we are interested in the executable LOAD segment */
			if (sgmt->p_type == PT_LOAD && (sgmt->p_flags & PF_X))
			{
				/* safe begin of segment in dli_fbase */
				dli->dli_fbase = (void*)sgmt->p_vaddr + dlpi->dlpi_addr;
				/* safe end of segment in dli_saddr */
				dli->dli_saddr = dli->dli_fbase + sgmt->p_memsz;
				return 1;
			}
		}
	}
	return 0;
}

METHOD(integrity_checker_t, build_segment, uint32_t,
	private_integrity_checker_t *this, void *sym, size_t *len)
{
	chunk_t segment;
	Dl_info dli;

	if (dladdr(sym, &dli) == 0)
	{
		DBG1(DBG_LIB, "  unable to locate symbol: %s", dlerror());
		return 0;
	}
	/* we reuse the Dl_info struct as in/out parameter */
	if (!dl_iterate_phdr((void*)callback, &dli))
	{
		DBG1(DBG_LIB, "  executable section not found");
		return 0;
	}

	segment = chunk_create(dli.dli_fbase, dli.dli_saddr - dli.dli_fbase);
	*len = segment.len;
	return chunk_hash_static(segment);
}

/**
 * Find a checksum by its name
 */
static integrity_checksum_t *find_checksum(private_integrity_checker_t *this,
										   char *name)
{
	int i;

	for (i = 0; i < this->checksum_count; i++)
	{
		if (streq(this->checksums[i].name, name))
		{
			return &this->checksums[i];
		}
	}
	return NULL;
}

METHOD(integrity_checker_t, check_file, bool,
	private_integrity_checker_t *this, char *name, char *file)
{
	integrity_checksum_t *cs;
	uint32_t sum;
	size_t len = 0;

	cs = find_checksum(this, name);
	if (!cs)
	{
		DBG1(DBG_LIB, "  '%s' file checksum not found", name);
		return FALSE;
	}
	sum = build_file(this, file, &len);
	if (!sum)
	{
		return FALSE;
	}
	if (cs->file_len != len)
	{
		DBG1(DBG_LIB, "  invalid '%s' file size: %u bytes, expected %u bytes",
			 name, len, cs->file_len);
		return FALSE;
	}
	if (cs->file != sum)
	{
		DBG1(DBG_LIB, "  invalid '%s' file checksum: %08x, expected %08x",
			 name, sum, cs->file);
		return FALSE;
	}
	DBG2(DBG_LIB, "  valid '%s' file checksum: %08x", name, sum);
	return TRUE;
}

METHOD(integrity_checker_t, check_segment, bool,
	private_integrity_checker_t *this, char *name, void *sym)
{
	integrity_checksum_t *cs;
	uint32_t sum;
	size_t len = 0;

	cs = find_checksum(this, name);
	if (!cs)
	{
		DBG1(DBG_LIB, "  '%s' segment checksum not found", name);
		return FALSE;
	}
	sum = build_segment(this, sym, &len);
	if (!sum)
	{
		return FALSE;
	}
	if (cs->segment_len != len)
	{
		DBG1(DBG_LIB, "  invalid '%s' segment size: %u bytes,"
			 " expected %u bytes", name, len, cs->segment_len);
		return FALSE;
	}
	if (cs->segment != sum)
	{
		DBG1(DBG_LIB, "  invalid '%s' segment checksum: %08x, expected %08x",
			 name, sum, cs->segment);
		return FALSE;
	}
	DBG2(DBG_LIB, "  valid '%s' segment checksum: %08x", name, sum);
	return TRUE;
}

METHOD(integrity_checker_t, check, bool,
	private_integrity_checker_t *this, char *name, void *sym)
{
	Dl_info dli;

	if (dladdr(sym, &dli) == 0)
	{
		DBG1(DBG_LIB, "unable to locate symbol: %s", dlerror());
		return FALSE;
	}
	if (!check_file(this, name, (char*)dli.dli_fname))
	{
		return FALSE;
	}
	if (!check_segment(this, name, sym))
	{
		return FALSE;
	}
	return TRUE;
}

METHOD(integrity_checker_t, destroy, void,
	private_integrity_checker_t *this)
{
	if (this->handle)
	{
		dlclose(this->handle);
	}
	free(this);
}

/**
 * See header
 */
integrity_checker_t *integrity_checker_create(char *checksum_library)
{
	private_integrity_checker_t *this;

	INIT(this,
		.public = {
			.check_file = _check_file,
			.build_file = _build_file,
			.check_segment = _check_segment,
			.build_segment = _build_segment,
			.check = _check,
			.destroy = _destroy,
		},
	);

	if (checksum_library)
	{
		this->handle = dlopen(checksum_library, RTLD_LAZY);
		if (this->handle)
		{
			int *checksum_count;

			this->checksums = dlsym(this->handle, "checksums");
			checksum_count = dlsym(this->handle, "checksum_count");
			if (this->checksums && checksum_count)
			{
				this->checksum_count = *checksum_count;
			}
			else
			{
				DBG1(DBG_LIB, "checksum library '%s' invalid",
					 checksum_library);
			}
		}
		else
		{
			DBG1(DBG_LIB, "loading checksum library '%s' failed",
				 checksum_library);
		}
	}
	return &this->public;
}