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