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 #include "ima_template_lib.h"
17 
18 static bool ima_template_hash_algo_allowed(u8 algo)
19 {
20 	if (algo == HASH_ALGO_SHA1 || algo == HASH_ALGO_MD5)
21 		return true;
22 
23 	return false;
24 }
25 
26 enum data_formats {
27 	DATA_FMT_DIGEST = 0,
28 	DATA_FMT_DIGEST_WITH_ALGO,
29 	DATA_FMT_STRING,
30 	DATA_FMT_HEX
31 };
32 
33 static int ima_write_template_field_data(const void *data, const u32 datalen,
34 					 enum data_formats datafmt,
35 					 struct ima_field_data *field_data)
36 {
37 	u8 *buf, *buf_ptr;
38 	u32 buflen = datalen;
39 
40 	if (datafmt == DATA_FMT_STRING)
41 		buflen = datalen + 1;
42 
43 	buf = kzalloc(buflen, GFP_KERNEL);
44 	if (!buf)
45 		return -ENOMEM;
46 
47 	memcpy(buf, data, datalen);
48 
49 	/*
50 	 * Replace all space characters with underscore for event names and
51 	 * strings. This avoid that, during the parsing of a measurements list,
52 	 * filenames with spaces or that end with the suffix ' (deleted)' are
53 	 * split into multiple template fields (the space is the delimitator
54 	 * character for measurements lists in ASCII format).
55 	 */
56 	if (datafmt == DATA_FMT_STRING) {
57 		for (buf_ptr = buf; buf_ptr - buf < datalen; buf_ptr++)
58 			if (*buf_ptr == ' ')
59 				*buf_ptr = '_';
60 	}
61 
62 	field_data->data = buf;
63 	field_data->len = buflen;
64 	return 0;
65 }
66 
67 static void ima_show_template_data_ascii(struct seq_file *m,
68 					 enum ima_show_type show,
69 					 enum data_formats datafmt,
70 					 struct ima_field_data *field_data)
71 {
72 	u8 *buf_ptr = field_data->data;
73 	u32 buflen = field_data->len;
74 
75 	switch (datafmt) {
76 	case DATA_FMT_DIGEST_WITH_ALGO:
77 		buf_ptr = strnchr(field_data->data, buflen, ':');
78 		if (buf_ptr != field_data->data)
79 			seq_printf(m, "%s", field_data->data);
80 
81 		/* skip ':' and '\0' */
82 		buf_ptr += 2;
83 		buflen -= buf_ptr - field_data->data;
84 	case DATA_FMT_DIGEST:
85 	case DATA_FMT_HEX:
86 		if (!buflen)
87 			break;
88 		ima_print_digest(m, buf_ptr, buflen);
89 		break;
90 	case DATA_FMT_STRING:
91 		seq_printf(m, "%s", buf_ptr);
92 		break;
93 	default:
94 		break;
95 	}
96 }
97 
98 static void ima_show_template_data_binary(struct seq_file *m,
99 					  enum ima_show_type show,
100 					  enum data_formats datafmt,
101 					  struct ima_field_data *field_data)
102 {
103 	u32 len = (show == IMA_SHOW_BINARY_OLD_STRING_FMT) ?
104 	    strlen(field_data->data) : field_data->len;
105 
106 	if (show != IMA_SHOW_BINARY_NO_FIELD_LEN) {
107 		u32 field_len = !ima_canonical_fmt ? len : cpu_to_le32(len);
108 
109 		ima_putc(m, &field_len, sizeof(field_len));
110 	}
111 
112 	if (!len)
113 		return;
114 
115 	ima_putc(m, field_data->data, len);
116 }
117 
118 static void ima_show_template_field_data(struct seq_file *m,
119 					 enum ima_show_type show,
120 					 enum data_formats datafmt,
121 					 struct ima_field_data *field_data)
122 {
123 	switch (show) {
124 	case IMA_SHOW_ASCII:
125 		ima_show_template_data_ascii(m, show, datafmt, field_data);
126 		break;
127 	case IMA_SHOW_BINARY:
128 	case IMA_SHOW_BINARY_NO_FIELD_LEN:
129 	case IMA_SHOW_BINARY_OLD_STRING_FMT:
130 		ima_show_template_data_binary(m, show, datafmt, field_data);
131 		break;
132 	default:
133 		break;
134 	}
135 }
136 
137 void ima_show_template_digest(struct seq_file *m, enum ima_show_type show,
138 			      struct ima_field_data *field_data)
139 {
140 	ima_show_template_field_data(m, show, DATA_FMT_DIGEST, field_data);
141 }
142 
143 void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
144 				 struct ima_field_data *field_data)
145 {
146 	ima_show_template_field_data(m, show, DATA_FMT_DIGEST_WITH_ALGO,
147 				     field_data);
148 }
149 
150 void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
151 			      struct ima_field_data *field_data)
152 {
153 	ima_show_template_field_data(m, show, DATA_FMT_STRING, field_data);
154 }
155 
156 void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
157 			   struct ima_field_data *field_data)
158 {
159 	ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
160 }
161 
162 /**
163  * ima_parse_buf() - Parses lengths and data from an input buffer
164  * @bufstartp:       Buffer start address.
165  * @bufendp:         Buffer end address.
166  * @bufcurp:         Pointer to remaining (non-parsed) data.
167  * @maxfields:       Length of fields array.
168  * @fields:          Array containing lengths and pointers of parsed data.
169  * @curfields:       Number of array items containing parsed data.
170  * @len_mask:        Bitmap (if bit is set, data length should not be parsed).
171  * @enforce_mask:    Check if curfields == maxfields and/or bufcurp == bufendp.
172  * @bufname:         String identifier of the input buffer.
173  *
174  * Return: 0 on success, -EINVAL on error.
175  */
176 int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
177 		  int maxfields, struct ima_field_data *fields, int *curfields,
178 		  unsigned long *len_mask, int enforce_mask, char *bufname)
179 {
180 	void *bufp = bufstartp;
181 	int i;
182 
183 	for (i = 0; i < maxfields; i++) {
184 		if (len_mask == NULL || !test_bit(i, len_mask)) {
185 			if (bufp > (bufendp - sizeof(u32)))
186 				break;
187 
188 			fields[i].len = *(u32 *)bufp;
189 			if (ima_canonical_fmt)
190 				fields[i].len = le32_to_cpu(fields[i].len);
191 
192 			bufp += sizeof(u32);
193 		}
194 
195 		if (bufp > (bufendp - fields[i].len))
196 			break;
197 
198 		fields[i].data = bufp;
199 		bufp += fields[i].len;
200 	}
201 
202 	if ((enforce_mask & ENFORCE_FIELDS) && i != maxfields) {
203 		pr_err("%s: nr of fields mismatch: expected: %d, current: %d\n",
204 		       bufname, maxfields, i);
205 		return -EINVAL;
206 	}
207 
208 	if ((enforce_mask & ENFORCE_BUFEND) && bufp != bufendp) {
209 		pr_err("%s: buf end mismatch: expected: %p, current: %p\n",
210 		       bufname, bufendp, bufp);
211 		return -EINVAL;
212 	}
213 
214 	if (curfields)
215 		*curfields = i;
216 
217 	if (bufcurp)
218 		*bufcurp = bufp;
219 
220 	return 0;
221 }
222 
223 static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
224 				       struct ima_field_data *field_data)
225 {
226 	/*
227 	 * digest formats:
228 	 *  - DATA_FMT_DIGEST: digest
229 	 *  - DATA_FMT_DIGEST_WITH_ALGO: [<hash algo>] + ':' + '\0' + digest,
230 	 *    where <hash algo> is provided if the hash algoritm is not
231 	 *    SHA1 or MD5
232 	 */
233 	u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
234 	enum data_formats fmt = DATA_FMT_DIGEST;
235 	u32 offset = 0;
236 
237 	if (hash_algo < HASH_ALGO__LAST) {
238 		fmt = DATA_FMT_DIGEST_WITH_ALGO;
239 		offset += snprintf(buffer, CRYPTO_MAX_ALG_NAME + 1, "%s",
240 				   hash_algo_name[hash_algo]);
241 		buffer[offset] = ':';
242 		offset += 2;
243 	}
244 
245 	if (digest)
246 		memcpy(buffer + offset, digest, digestsize);
247 	else
248 		/*
249 		 * If digest is NULL, the event being recorded is a violation.
250 		 * Make room for the digest by increasing the offset of
251 		 * IMA_DIGEST_SIZE.
252 		 */
253 		offset += IMA_DIGEST_SIZE;
254 
255 	return ima_write_template_field_data(buffer, offset + digestsize,
256 					     fmt, field_data);
257 }
258 
259 /*
260  * This function writes the digest of an event (with size limit).
261  */
262 int ima_eventdigest_init(struct ima_event_data *event_data,
263 			 struct ima_field_data *field_data)
264 {
265 	struct {
266 		struct ima_digest_data hdr;
267 		char digest[IMA_MAX_DIGEST_SIZE];
268 	} hash;
269 	u8 *cur_digest = NULL;
270 	u32 cur_digestsize = 0;
271 	struct inode *inode;
272 	int result;
273 
274 	memset(&hash, 0, sizeof(hash));
275 
276 	if (event_data->violation)	/* recording a violation. */
277 		goto out;
278 
279 	if (ima_template_hash_algo_allowed(event_data->iint->ima_hash->algo)) {
280 		cur_digest = event_data->iint->ima_hash->digest;
281 		cur_digestsize = event_data->iint->ima_hash->length;
282 		goto out;
283 	}
284 
285 	if (!event_data->file)	/* missing info to re-calculate the digest */
286 		return -EINVAL;
287 
288 	inode = file_inode(event_data->file);
289 	hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
290 	    ima_hash_algo : HASH_ALGO_SHA1;
291 	result = ima_calc_file_hash(event_data->file, &hash.hdr);
292 	if (result) {
293 		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
294 				    event_data->filename, "collect_data",
295 				    "failed", result, 0);
296 		return result;
297 	}
298 	cur_digest = hash.hdr.digest;
299 	cur_digestsize = hash.hdr.length;
300 out:
301 	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
302 					   HASH_ALGO__LAST, field_data);
303 }
304 
305 /*
306  * This function writes the digest of an event (without size limit).
307  */
308 int ima_eventdigest_ng_init(struct ima_event_data *event_data,
309 			    struct ima_field_data *field_data)
310 {
311 	u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
312 	u32 cur_digestsize = 0;
313 
314 	if (event_data->violation)	/* recording a violation. */
315 		goto out;
316 
317 	cur_digest = event_data->iint->ima_hash->digest;
318 	cur_digestsize = event_data->iint->ima_hash->length;
319 
320 	hash_algo = event_data->iint->ima_hash->algo;
321 out:
322 	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
323 					   hash_algo, field_data);
324 }
325 
326 static int ima_eventname_init_common(struct ima_event_data *event_data,
327 				     struct ima_field_data *field_data,
328 				     bool size_limit)
329 {
330 	const char *cur_filename = NULL;
331 	u32 cur_filename_len = 0;
332 
333 	BUG_ON(event_data->filename == NULL && event_data->file == NULL);
334 
335 	if (event_data->filename) {
336 		cur_filename = event_data->filename;
337 		cur_filename_len = strlen(event_data->filename);
338 
339 		if (!size_limit || cur_filename_len <= IMA_EVENT_NAME_LEN_MAX)
340 			goto out;
341 	}
342 
343 	if (event_data->file) {
344 		cur_filename = event_data->file->f_path.dentry->d_name.name;
345 		cur_filename_len = strlen(cur_filename);
346 	} else
347 		/*
348 		 * Truncate filename if the latter is too long and
349 		 * the file descriptor is not available.
350 		 */
351 		cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
352 out:
353 	return ima_write_template_field_data(cur_filename, cur_filename_len,
354 					     DATA_FMT_STRING, field_data);
355 }
356 
357 /*
358  * This function writes the name of an event (with size limit).
359  */
360 int ima_eventname_init(struct ima_event_data *event_data,
361 		       struct ima_field_data *field_data)
362 {
363 	return ima_eventname_init_common(event_data, field_data, true);
364 }
365 
366 /*
367  * This function writes the name of an event (without size limit).
368  */
369 int ima_eventname_ng_init(struct ima_event_data *event_data,
370 			  struct ima_field_data *field_data)
371 {
372 	return ima_eventname_init_common(event_data, field_data, false);
373 }
374 
375 /*
376  *  ima_eventsig_init - include the file signature as part of the template data
377  */
378 int ima_eventsig_init(struct ima_event_data *event_data,
379 		      struct ima_field_data *field_data)
380 {
381 	enum data_formats fmt = DATA_FMT_HEX;
382 	struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
383 	int xattr_len = event_data->xattr_len;
384 	int rc = 0;
385 
386 	if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
387 		goto out;
388 
389 	rc = ima_write_template_field_data(xattr_value, xattr_len, fmt,
390 					   field_data);
391 out:
392 	return rc;
393 }
394