1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2013 Politecnico di Torino, Italy
4  *                    TORSEC group -- http://security.polito.it
5  *
6  * Author: Roberto Sassu <roberto.sassu@polito.it>
7  *
8  * File: ima_template_lib.c
9  *      Library of supported template fields.
10  */
11 
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 
14 #include "ima_template_lib.h"
15 
16 static bool ima_template_hash_algo_allowed(u8 algo)
17 {
18 	if (algo == HASH_ALGO_SHA1 || algo == HASH_ALGO_MD5)
19 		return true;
20 
21 	return false;
22 }
23 
24 enum data_formats {
25 	DATA_FMT_DIGEST = 0,
26 	DATA_FMT_DIGEST_WITH_ALGO,
27 	DATA_FMT_STRING,
28 	DATA_FMT_HEX
29 };
30 
31 static int ima_write_template_field_data(const void *data, const u32 datalen,
32 					 enum data_formats datafmt,
33 					 struct ima_field_data *field_data)
34 {
35 	u8 *buf, *buf_ptr;
36 	u32 buflen = datalen;
37 
38 	if (datafmt == DATA_FMT_STRING)
39 		buflen = datalen + 1;
40 
41 	buf = kzalloc(buflen, GFP_KERNEL);
42 	if (!buf)
43 		return -ENOMEM;
44 
45 	memcpy(buf, data, datalen);
46 
47 	/*
48 	 * Replace all space characters with underscore for event names and
49 	 * strings. This avoid that, during the parsing of a measurements list,
50 	 * filenames with spaces or that end with the suffix ' (deleted)' are
51 	 * split into multiple template fields (the space is the delimitator
52 	 * character for measurements lists in ASCII format).
53 	 */
54 	if (datafmt == DATA_FMT_STRING) {
55 		for (buf_ptr = buf; buf_ptr - buf < datalen; buf_ptr++)
56 			if (*buf_ptr == ' ')
57 				*buf_ptr = '_';
58 	}
59 
60 	field_data->data = buf;
61 	field_data->len = buflen;
62 	return 0;
63 }
64 
65 static void ima_show_template_data_ascii(struct seq_file *m,
66 					 enum ima_show_type show,
67 					 enum data_formats datafmt,
68 					 struct ima_field_data *field_data)
69 {
70 	u8 *buf_ptr = field_data->data;
71 	u32 buflen = field_data->len;
72 
73 	switch (datafmt) {
74 	case DATA_FMT_DIGEST_WITH_ALGO:
75 		buf_ptr = strnchr(field_data->data, buflen, ':');
76 		if (buf_ptr != field_data->data)
77 			seq_printf(m, "%s", field_data->data);
78 
79 		/* skip ':' and '\0' */
80 		buf_ptr += 2;
81 		buflen -= buf_ptr - field_data->data;
82 		/* fall through */
83 	case DATA_FMT_DIGEST:
84 	case DATA_FMT_HEX:
85 		if (!buflen)
86 			break;
87 		ima_print_digest(m, buf_ptr, buflen);
88 		break;
89 	case DATA_FMT_STRING:
90 		seq_printf(m, "%s", buf_ptr);
91 		break;
92 	default:
93 		break;
94 	}
95 }
96 
97 static void ima_show_template_data_binary(struct seq_file *m,
98 					  enum ima_show_type show,
99 					  enum data_formats datafmt,
100 					  struct ima_field_data *field_data)
101 {
102 	u32 len = (show == IMA_SHOW_BINARY_OLD_STRING_FMT) ?
103 	    strlen(field_data->data) : field_data->len;
104 
105 	if (show != IMA_SHOW_BINARY_NO_FIELD_LEN) {
106 		u32 field_len = !ima_canonical_fmt ? len : cpu_to_le32(len);
107 
108 		ima_putc(m, &field_len, sizeof(field_len));
109 	}
110 
111 	if (!len)
112 		return;
113 
114 	ima_putc(m, field_data->data, len);
115 }
116 
117 static void ima_show_template_field_data(struct seq_file *m,
118 					 enum ima_show_type show,
119 					 enum data_formats datafmt,
120 					 struct ima_field_data *field_data)
121 {
122 	switch (show) {
123 	case IMA_SHOW_ASCII:
124 		ima_show_template_data_ascii(m, show, datafmt, field_data);
125 		break;
126 	case IMA_SHOW_BINARY:
127 	case IMA_SHOW_BINARY_NO_FIELD_LEN:
128 	case IMA_SHOW_BINARY_OLD_STRING_FMT:
129 		ima_show_template_data_binary(m, show, datafmt, field_data);
130 		break;
131 	default:
132 		break;
133 	}
134 }
135 
136 void ima_show_template_digest(struct seq_file *m, enum ima_show_type show,
137 			      struct ima_field_data *field_data)
138 {
139 	ima_show_template_field_data(m, show, DATA_FMT_DIGEST, field_data);
140 }
141 
142 void ima_show_template_digest_ng(struct seq_file *m, enum ima_show_type show,
143 				 struct ima_field_data *field_data)
144 {
145 	ima_show_template_field_data(m, show, DATA_FMT_DIGEST_WITH_ALGO,
146 				     field_data);
147 }
148 
149 void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
150 			      struct ima_field_data *field_data)
151 {
152 	ima_show_template_field_data(m, show, DATA_FMT_STRING, field_data);
153 }
154 
155 void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
156 			   struct ima_field_data *field_data)
157 {
158 	ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
159 }
160 
161 /**
162  * ima_parse_buf() - Parses lengths and data from an input buffer
163  * @bufstartp:       Buffer start address.
164  * @bufendp:         Buffer end address.
165  * @bufcurp:         Pointer to remaining (non-parsed) data.
166  * @maxfields:       Length of fields array.
167  * @fields:          Array containing lengths and pointers of parsed data.
168  * @curfields:       Number of array items containing parsed data.
169  * @len_mask:        Bitmap (if bit is set, data length should not be parsed).
170  * @enforce_mask:    Check if curfields == maxfields and/or bufcurp == bufendp.
171  * @bufname:         String identifier of the input buffer.
172  *
173  * Return: 0 on success, -EINVAL on error.
174  */
175 int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
176 		  int maxfields, struct ima_field_data *fields, int *curfields,
177 		  unsigned long *len_mask, int enforce_mask, char *bufname)
178 {
179 	void *bufp = bufstartp;
180 	int i;
181 
182 	for (i = 0; i < maxfields; i++) {
183 		if (len_mask == NULL || !test_bit(i, len_mask)) {
184 			if (bufp > (bufendp - sizeof(u32)))
185 				break;
186 
187 			fields[i].len = *(u32 *)bufp;
188 			if (ima_canonical_fmt)
189 				fields[i].len = le32_to_cpu(fields[i].len);
190 
191 			bufp += sizeof(u32);
192 		}
193 
194 		if (bufp > (bufendp - fields[i].len))
195 			break;
196 
197 		fields[i].data = bufp;
198 		bufp += fields[i].len;
199 	}
200 
201 	if ((enforce_mask & ENFORCE_FIELDS) && i != maxfields) {
202 		pr_err("%s: nr of fields mismatch: expected: %d, current: %d\n",
203 		       bufname, maxfields, i);
204 		return -EINVAL;
205 	}
206 
207 	if ((enforce_mask & ENFORCE_BUFEND) && bufp != bufendp) {
208 		pr_err("%s: buf end mismatch: expected: %p, current: %p\n",
209 		       bufname, bufendp, bufp);
210 		return -EINVAL;
211 	}
212 
213 	if (curfields)
214 		*curfields = i;
215 
216 	if (bufcurp)
217 		*bufcurp = bufp;
218 
219 	return 0;
220 }
221 
222 static int ima_eventdigest_init_common(u8 *digest, u32 digestsize, u8 hash_algo,
223 				       struct ima_field_data *field_data)
224 {
225 	/*
226 	 * digest formats:
227 	 *  - DATA_FMT_DIGEST: digest
228 	 *  - DATA_FMT_DIGEST_WITH_ALGO: [<hash algo>] + ':' + '\0' + digest,
229 	 *    where <hash algo> is provided if the hash algoritm is not
230 	 *    SHA1 or MD5
231 	 */
232 	u8 buffer[CRYPTO_MAX_ALG_NAME + 2 + IMA_MAX_DIGEST_SIZE] = { 0 };
233 	enum data_formats fmt = DATA_FMT_DIGEST;
234 	u32 offset = 0;
235 
236 	if (hash_algo < HASH_ALGO__LAST) {
237 		fmt = DATA_FMT_DIGEST_WITH_ALGO;
238 		offset += snprintf(buffer, CRYPTO_MAX_ALG_NAME + 1, "%s",
239 				   hash_algo_name[hash_algo]);
240 		buffer[offset] = ':';
241 		offset += 2;
242 	}
243 
244 	if (digest)
245 		memcpy(buffer + offset, digest, digestsize);
246 	else
247 		/*
248 		 * If digest is NULL, the event being recorded is a violation.
249 		 * Make room for the digest by increasing the offset of
250 		 * IMA_DIGEST_SIZE.
251 		 */
252 		offset += IMA_DIGEST_SIZE;
253 
254 	return ima_write_template_field_data(buffer, offset + digestsize,
255 					     fmt, field_data);
256 }
257 
258 /*
259  * This function writes the digest of an event (with size limit).
260  */
261 int ima_eventdigest_init(struct ima_event_data *event_data,
262 			 struct ima_field_data *field_data)
263 {
264 	struct {
265 		struct ima_digest_data hdr;
266 		char digest[IMA_MAX_DIGEST_SIZE];
267 	} hash;
268 	u8 *cur_digest = NULL;
269 	u32 cur_digestsize = 0;
270 	struct inode *inode;
271 	int result;
272 
273 	memset(&hash, 0, sizeof(hash));
274 
275 	if (event_data->violation)	/* recording a violation. */
276 		goto out;
277 
278 	if (ima_template_hash_algo_allowed(event_data->iint->ima_hash->algo)) {
279 		cur_digest = event_data->iint->ima_hash->digest;
280 		cur_digestsize = event_data->iint->ima_hash->length;
281 		goto out;
282 	}
283 
284 	if (!event_data->file)	/* missing info to re-calculate the digest */
285 		return -EINVAL;
286 
287 	inode = file_inode(event_data->file);
288 	hash.hdr.algo = ima_template_hash_algo_allowed(ima_hash_algo) ?
289 	    ima_hash_algo : HASH_ALGO_SHA1;
290 	result = ima_calc_file_hash(event_data->file, &hash.hdr);
291 	if (result) {
292 		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
293 				    event_data->filename, "collect_data",
294 				    "failed", result, 0);
295 		return result;
296 	}
297 	cur_digest = hash.hdr.digest;
298 	cur_digestsize = hash.hdr.length;
299 out:
300 	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
301 					   HASH_ALGO__LAST, field_data);
302 }
303 
304 /*
305  * This function writes the digest of an event (without size limit).
306  */
307 int ima_eventdigest_ng_init(struct ima_event_data *event_data,
308 			    struct ima_field_data *field_data)
309 {
310 	u8 *cur_digest = NULL, hash_algo = HASH_ALGO_SHA1;
311 	u32 cur_digestsize = 0;
312 
313 	if (event_data->violation)	/* recording a violation. */
314 		goto out;
315 
316 	cur_digest = event_data->iint->ima_hash->digest;
317 	cur_digestsize = event_data->iint->ima_hash->length;
318 
319 	hash_algo = event_data->iint->ima_hash->algo;
320 out:
321 	return ima_eventdigest_init_common(cur_digest, cur_digestsize,
322 					   hash_algo, field_data);
323 }
324 
325 static int ima_eventname_init_common(struct ima_event_data *event_data,
326 				     struct ima_field_data *field_data,
327 				     bool size_limit)
328 {
329 	const char *cur_filename = NULL;
330 	u32 cur_filename_len = 0;
331 
332 	BUG_ON(event_data->filename == NULL && event_data->file == NULL);
333 
334 	if (event_data->filename) {
335 		cur_filename = event_data->filename;
336 		cur_filename_len = strlen(event_data->filename);
337 
338 		if (!size_limit || cur_filename_len <= IMA_EVENT_NAME_LEN_MAX)
339 			goto out;
340 	}
341 
342 	if (event_data->file) {
343 		cur_filename = event_data->file->f_path.dentry->d_name.name;
344 		cur_filename_len = strlen(cur_filename);
345 	} else
346 		/*
347 		 * Truncate filename if the latter is too long and
348 		 * the file descriptor is not available.
349 		 */
350 		cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
351 out:
352 	return ima_write_template_field_data(cur_filename, cur_filename_len,
353 					     DATA_FMT_STRING, field_data);
354 }
355 
356 /*
357  * This function writes the name of an event (with size limit).
358  */
359 int ima_eventname_init(struct ima_event_data *event_data,
360 		       struct ima_field_data *field_data)
361 {
362 	return ima_eventname_init_common(event_data, field_data, true);
363 }
364 
365 /*
366  * This function writes the name of an event (without size limit).
367  */
368 int ima_eventname_ng_init(struct ima_event_data *event_data,
369 			  struct ima_field_data *field_data)
370 {
371 	return ima_eventname_init_common(event_data, field_data, false);
372 }
373 
374 /*
375  *  ima_eventsig_init - include the file signature as part of the template data
376  */
377 int ima_eventsig_init(struct ima_event_data *event_data,
378 		      struct ima_field_data *field_data)
379 {
380 	struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
381 
382 	if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
383 		return 0;
384 
385 	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
386 					     DATA_FMT_HEX, field_data);
387 }
388