1 /*
2  * Copyright (C) 2013 Politecnico di Torino, Italy
3  *                    TORSEC group -- http://security.polito.it
4  *
5  * Author: Roberto Sassu <roberto.sassu@polito.it>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License as
9  * published by the Free Software Foundation, version 2 of the
10  * License.
11  *
12  * File: ima_template_lib.c
13  *      Library of supported template fields.
14  */
15 
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 
18 #include "ima_template_lib.h"
19 
20 static bool ima_template_hash_algo_allowed(u8 algo)
21 {
22 	if (algo == HASH_ALGO_SHA1 || algo == HASH_ALGO_MD5)
23 		return true;
24 
25 	return false;
26 }
27 
28 enum data_formats {
29 	DATA_FMT_DIGEST = 0,
30 	DATA_FMT_DIGEST_WITH_ALGO,
31 	DATA_FMT_STRING,
32 	DATA_FMT_HEX
33 };
34 
35 static int ima_write_template_field_data(const void *data, const u32 datalen,
36 					 enum data_formats datafmt,
37 					 struct ima_field_data *field_data)
38 {
39 	u8 *buf, *buf_ptr;
40 	u32 buflen = datalen;
41 
42 	if (datafmt == DATA_FMT_STRING)
43 		buflen = datalen + 1;
44 
45 	buf = kzalloc(buflen, GFP_KERNEL);
46 	if (!buf)
47 		return -ENOMEM;
48 
49 	memcpy(buf, data, datalen);
50 
51 	/*
52 	 * Replace all space characters with underscore for event names and
53 	 * strings. This avoid that, during the parsing of a measurements list,
54 	 * filenames with spaces or that end with the suffix ' (deleted)' are
55 	 * split into multiple template fields (the space is the delimitator
56 	 * character for measurements lists in ASCII format).
57 	 */
58 	if (datafmt == DATA_FMT_STRING) {
59 		for (buf_ptr = buf; buf_ptr - buf < datalen; buf_ptr++)
60 			if (*buf_ptr == ' ')
61 				*buf_ptr = '_';
62 	}
63 
64 	field_data->data = buf;
65 	field_data->len = buflen;
66 	return 0;
67 }
68 
69 static void ima_show_template_data_ascii(struct seq_file *m,
70 					 enum ima_show_type show,
71 					 enum data_formats datafmt,
72 					 struct ima_field_data *field_data)
73 {
74 	u8 *buf_ptr = field_data->data;
75 	u32 buflen = field_data->len;
76 
77 	switch (datafmt) {
78 	case DATA_FMT_DIGEST_WITH_ALGO:
79 		buf_ptr = strnchr(field_data->data, buflen, ':');
80 		if (buf_ptr != field_data->data)
81 			seq_printf(m, "%s", field_data->data);
82 
83 		/* skip ':' and '\0' */
84 		buf_ptr += 2;
85 		buflen -= buf_ptr - field_data->data;
86 		/* fall through */
87 	case DATA_FMT_DIGEST:
88 	case DATA_FMT_HEX:
89 		if (!buflen)
90 			break;
91 		ima_print_digest(m, buf_ptr, buflen);
92 		break;
93 	case DATA_FMT_STRING:
94 		seq_printf(m, "%s", buf_ptr);
95 		break;
96 	default:
97 		break;
98 	}
99 }
100 
101 static void ima_show_template_data_binary(struct seq_file *m,
102 					  enum ima_show_type show,
103 					  enum data_formats datafmt,
104 					  struct ima_field_data *field_data)
105 {
106 	u32 len = (show == IMA_SHOW_BINARY_OLD_STRING_FMT) ?
107 	    strlen(field_data->data) : field_data->len;
108 
109 	if (show != IMA_SHOW_BINARY_NO_FIELD_LEN) {
110 		u32 field_len = !ima_canonical_fmt ? len : cpu_to_le32(len);
111 
112 		ima_putc(m, &field_len, sizeof(field_len));
113 	}
114 
115 	if (!len)
116 		return;
117 
118 	ima_putc(m, field_data->data, len);
119 }
120 
121 static void ima_show_template_field_data(struct seq_file *m,
122 					 enum ima_show_type show,
123 					 enum data_formats datafmt,
124 					 struct ima_field_data *field_data)
125 {
126 	switch (show) {
127 	case IMA_SHOW_ASCII:
128 		ima_show_template_data_ascii(m, show, datafmt, field_data);
129 		break;
130 	case IMA_SHOW_BINARY:
131 	case IMA_SHOW_BINARY_NO_FIELD_LEN:
132 	case IMA_SHOW_BINARY_OLD_STRING_FMT:
133 		ima_show_template_data_binary(m, show, datafmt, field_data);
134 		break;
135 	default:
136 		break;
137 	}
138 }
139 
140 void ima_show_template_digest(struct seq_file *m, enum ima_show_type show,
141 			      struct ima_field_data *field_data)
142 {
143 	ima_show_template_field_data(m, show, DATA_FMT_DIGEST, field_data);
144 }
145 
146 void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
147 				 struct ima_field_data *field_data)
148 {
149 	ima_show_template_field_data(m, show, DATA_FMT_DIGEST_WITH_ALGO,
150 				     field_data);
151 }
152 
153 void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
154 			      struct ima_field_data *field_data)
155 {
156 	ima_show_template_field_data(m, show, DATA_FMT_STRING, field_data);
157 }
158 
159 void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
160 			   struct ima_field_data *field_data)
161 {
162 	ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
163 }
164 
165 /**
166  * ima_parse_buf() - Parses lengths and data from an input buffer
167  * @bufstartp:       Buffer start address.
168  * @bufendp:         Buffer end address.
169  * @bufcurp:         Pointer to remaining (non-parsed) data.
170  * @maxfields:       Length of fields array.
171  * @fields:          Array containing lengths and pointers of parsed data.
172  * @curfields:       Number of array items containing parsed data.
173  * @len_mask:        Bitmap (if bit is set, data length should not be parsed).
174  * @enforce_mask:    Check if curfields == maxfields and/or bufcurp == bufendp.
175  * @bufname:         String identifier of the input buffer.
176  *
177  * Return: 0 on success, -EINVAL on error.
178  */
179 int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
180 		  int maxfields, struct ima_field_data *fields, int *curfields,
181 		  unsigned long *len_mask, int enforce_mask, char *bufname)
182 {
183 	void *bufp = bufstartp;
184 	int i;
185 
186 	for (i = 0; i < maxfields; i++) {
187 		if (len_mask == NULL || !test_bit(i, len_mask)) {
188 			if (bufp > (bufendp - sizeof(u32)))
189 				break;
190 
191 			fields[i].len = *(u32 *)bufp;
192 			if (ima_canonical_fmt)
193 				fields[i].len = le32_to_cpu(fields[i].len);
194 
195 			bufp += sizeof(u32);
196 		}
197 
198 		if (bufp > (bufendp - fields[i].len))
199 			break;
200 
201 		fields[i].data = bufp;
202 		bufp += fields[i].len;
203 	}
204 
205 	if ((enforce_mask & ENFORCE_FIELDS) && i != maxfields) {
206 		pr_err("%s: nr of fields mismatch: expected: %d, current: %d\n",
207 		       bufname, maxfields, i);
208 		return -EINVAL;
209 	}
210 
211 	if ((enforce_mask & ENFORCE_BUFEND) && bufp != bufendp) {
212 		pr_err("%s: buf end mismatch: expected: %p, current: %p\n",
213 		       bufname, bufendp, bufp);
214 		return -EINVAL;
215 	}
216 
217 	if (curfields)
218 		*curfields = i;
219 
220 	if (bufcurp)
221 		*bufcurp = bufp;
222 
223 	return 0;
224 }
225 
226 static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
227 				       struct ima_field_data *field_data)
228 {
229 	/*
230 	 * digest formats:
231 	 *  - DATA_FMT_DIGEST: digest
232 	 *  - DATA_FMT_DIGEST_WITH_ALGO: [<hash algo>] + ':' + '\0' + digest,
233 	 *    where <hash algo> is provided if the hash algoritm is not
234 	 *    SHA1 or MD5
235 	 */
236 	u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
237 	enum data_formats fmt = DATA_FMT_DIGEST;
238 	u32 offset = 0;
239 
240 	if (hash_algo < HASH_ALGO__LAST) {
241 		fmt = DATA_FMT_DIGEST_WITH_ALGO;
242 		offset += snprintf(buffer, CRYPTO_MAX_ALG_NAME + 1, "%s",
243 				   hash_algo_name[hash_algo]);
244 		buffer[offset] = ':';
245 		offset += 2;
246 	}
247 
248 	if (digest)
249 		memcpy(buffer + offset, digest, digestsize);
250 	else
251 		/*
252 		 * If digest is NULL, the event being recorded is a violation.
253 		 * Make room for the digest by increasing the offset of
254 		 * IMA_DIGEST_SIZE.
255 		 */
256 		offset += IMA_DIGEST_SIZE;
257 
258 	return ima_write_template_field_data(buffer, offset + digestsize,
259 					     fmt, field_data);
260 }
261 
262 /*
263  * This function writes the digest of an event (with size limit).
264  */
265 int ima_eventdigest_init(struct ima_event_data *event_data,
266 			 struct ima_field_data *field_data)
267 {
268 	struct {
269 		struct ima_digest_data hdr;
270 		char digest[IMA_MAX_DIGEST_SIZE];
271 	} hash;
272 	u8 *cur_digest = NULL;
273 	u32 cur_digestsize = 0;
274 	struct inode *inode;
275 	int result;
276 
277 	memset(&hash, 0, sizeof(hash));
278 
279 	if (event_data->violation)	/* recording a violation. */
280 		goto out;
281 
282 	if (ima_template_hash_algo_allowed(event_data->iint->ima_hash->algo)) {
283 		cur_digest = event_data->iint->ima_hash->digest;
284 		cur_digestsize = event_data->iint->ima_hash->length;
285 		goto out;
286 	}
287 
288 	if (!event_data->file)	/* missing info to re-calculate the digest */
289 		return -EINVAL;
290 
291 	inode = file_inode(event_data->file);
292 	hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
293 	    ima_hash_algo : HASH_ALGO_SHA1;
294 	result = ima_calc_file_hash(event_data->file, &hash.hdr);
295 	if (result) {
296 		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
297 				    event_data->filename, "collect_data",
298 				    "failed", result, 0);
299 		return result;
300 	}
301 	cur_digest = hash.hdr.digest;
302 	cur_digestsize = hash.hdr.length;
303 out:
304 	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
305 					   HASH_ALGO__LAST, field_data);
306 }
307 
308 /*
309  * This function writes the digest of an event (without size limit).
310  */
311 int ima_eventdigest_ng_init(struct ima_event_data *event_data,
312 			    struct ima_field_data *field_data)
313 {
314 	u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
315 	u32 cur_digestsize = 0;
316 
317 	if (event_data->violation)	/* recording a violation. */
318 		goto out;
319 
320 	cur_digest = event_data->iint->ima_hash->digest;
321 	cur_digestsize = event_data->iint->ima_hash->length;
322 
323 	hash_algo = event_data->iint->ima_hash->algo;
324 out:
325 	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
326 					   hash_algo, field_data);
327 }
328 
329 static int ima_eventname_init_common(struct ima_event_data *event_data,
330 				     struct ima_field_data *field_data,
331 				     bool size_limit)
332 {
333 	const char *cur_filename = NULL;
334 	u32 cur_filename_len = 0;
335 
336 	BUG_ON(event_data->filename == NULL && event_data->file == NULL);
337 
338 	if (event_data->filename) {
339 		cur_filename = event_data->filename;
340 		cur_filename_len = strlen(event_data->filename);
341 
342 		if (!size_limit || cur_filename_len <= IMA_EVENT_NAME_LEN_MAX)
343 			goto out;
344 	}
345 
346 	if (event_data->file) {
347 		cur_filename = event_data->file->f_path.dentry->d_name.name;
348 		cur_filename_len = strlen(cur_filename);
349 	} else
350 		/*
351 		 * Truncate filename if the latter is too long and
352 		 * the file descriptor is not available.
353 		 */
354 		cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
355 out:
356 	return ima_write_template_field_data(cur_filename, cur_filename_len,
357 					     DATA_FMT_STRING, field_data);
358 }
359 
360 /*
361  * This function writes the name of an event (with size limit).
362  */
363 int ima_eventname_init(struct ima_event_data *event_data,
364 		       struct ima_field_data *field_data)
365 {
366 	return ima_eventname_init_common(event_data, field_data, true);
367 }
368 
369 /*
370  * This function writes the name of an event (without size limit).
371  */
372 int ima_eventname_ng_init(struct ima_event_data *event_data,
373 			  struct ima_field_data *field_data)
374 {
375 	return ima_eventname_init_common(event_data, field_data, false);
376 }
377 
378 /*
379  *  ima_eventsig_init - include the file signature as part of the template data
380  */
381 int ima_eventsig_init(struct ima_event_data *event_data,
382 		      struct ima_field_data *field_data)
383 {
384 	struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
385 
386 	if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
387 		return 0;
388 
389 	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
390 					     DATA_FMT_HEX, field_data);
391 }
392