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2023-12-11 6778948f9de86c3cfaf36725a7c87dcff9ba247f 
 kernel/security/integrity/ima/ima_appraise.c
....@@ -1,32 +1,47 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * Copyright (C) 2011 IBM Corporation
34  *
45  * Author:
56  * Mimi Zohar <zohar@us.ibm.com>
6
- *
7
- * This program is free software; you can redistribute it and/or modify
8
- * it under the terms of the GNU General Public License as published by
9
- * the Free Software Foundation, version 2 of the License.
107  */
11
-#include <linux/module.h>
8
+#include <linux/init.h>
129 #include <linux/file.h>
1310 #include <linux/fs.h>
1411 #include <linux/xattr.h>
1512 #include <linux/magic.h>
1613 #include <linux/ima.h>
1714 #include <linux/evm.h>
15
+#include <keys/system_keyring.h>
1816 
1917 #include "ima.h"
2018 
2119 static int __init default_appraise_setup(char *str)
2220 {
2321 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
22
+	bool sb_state = arch_ima_get_secureboot();
23
+	int appraisal_state = ima_appraise;
24
+
2425 	if (strncmp(str, "off", 3) == 0)
25
-		ima_appraise = 0;
26
+		appraisal_state = 0;
2627 	else if (strncmp(str, "log", 3) == 0)
27
-		ima_appraise = IMA_APPRAISE_LOG;
28
+		appraisal_state = IMA_APPRAISE_LOG;
2829 	else if (strncmp(str, "fix", 3) == 0)
29
-		ima_appraise = IMA_APPRAISE_FIX;
30
+		appraisal_state = IMA_APPRAISE_FIX;
31
+	else if (strncmp(str, "enforce", 7) == 0)
32
+		appraisal_state = IMA_APPRAISE_ENFORCE;
33
+	else
34
+		pr_err("invalid \"%s\" appraise option", str);
35
+
36
+	/* If appraisal state was changed, but secure boot is enabled,
37
+	 * keep its default */
38
+	if (sb_state) {
39
+		if (!(appraisal_state & IMA_APPRAISE_ENFORCE))
40
+			pr_info("Secure boot enabled: ignoring ima_appraise=%s option",
41
+				str);
42
+	} else {
43
+		ima_appraise = appraisal_state;
44
+	}
3045 #endif
3146 	return 1;
3247 }
....@@ -57,7 +72,7 @@
5772 
5873 	security_task_getsecid(current, &secid);
5974 	return ima_match_policy(inode, current_cred(), secid, func, mask,
60
-				IMA_APPRAISE | IMA_HASH, NULL);
75
+				IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL);
6176 }
6277 
6378 static int ima_fix_xattr(struct dentry *dentry,
....@@ -114,6 +129,7 @@
114129 		break;
115130 	case CREDS_CHECK:
116131 		iint->ima_creds_status = status;
132
+		break;
117133 	case FILE_CHECK:
118134 	case POST_SETATTR:
119135 		iint->ima_file_status = status;
....@@ -167,7 +183,8 @@
167183 		return sig->hash_algo;
168184 		break;
169185 	case IMA_XATTR_DIGEST_NG:
170
-		ret = xattr_value->digest[0];
186
+		/* first byte contains algorithm id */
187
+		ret = xattr_value->data[0];
171188 		if (ret < HASH_ALGO__LAST)
172189 			return ret;
173190 		break;
....@@ -175,7 +192,7 @@
175192 		/* this is for backward compatibility */
176193 		if (xattr_len == 21) {
177194 			unsigned int zero = 0;
178
-			if (!memcmp(&xattr_value->digest[16], &zero, 4))
195
+			if (!memcmp(&xattr_value->data[16], &zero, 4))
179196 				return HASH_ALGO_MD5;
180197 			else
181198 				return HASH_ALGO_SHA1;
....@@ -201,6 +218,142 @@
201218 }
202219 
203220 /*
221
+ * xattr_verify - verify xattr digest or signature
222
+ *
223
+ * Verify whether the hash or signature matches the file contents.
224
+ *
225
+ * Return 0 on success, error code otherwise.
226
+ */
227
+static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
228
+			struct evm_ima_xattr_data *xattr_value, int xattr_len,
229
+			enum integrity_status *status, const char **cause)
230
+{
231
+	int rc = -EINVAL, hash_start = 0;
232
+
233
+	switch (xattr_value->type) {
234
+	case IMA_XATTR_DIGEST_NG:
235
+		/* first byte contains algorithm id */
236
+		hash_start = 1;
237
+		fallthrough;
238
+	case IMA_XATTR_DIGEST:
239
+		if (iint->flags & IMA_DIGSIG_REQUIRED) {
240
+			*cause = "IMA-signature-required";
241
+			*status = INTEGRITY_FAIL;
242
+			break;
243
+		}
244
+		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
245
+		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
246
+				iint->ima_hash->length)
247
+			/*
248
+			 * xattr length may be longer. md5 hash in previous
249
+			 * version occupied 20 bytes in xattr, instead of 16
250
+			 */
251
+			rc = memcmp(&xattr_value->data[hash_start],
252
+				    iint->ima_hash->digest,
253
+				    iint->ima_hash->length);
254
+		else
255
+			rc = -EINVAL;
256
+		if (rc) {
257
+			*cause = "invalid-hash";
258
+			*status = INTEGRITY_FAIL;
259
+			break;
260
+		}
261
+		*status = INTEGRITY_PASS;
262
+		break;
263
+	case EVM_IMA_XATTR_DIGSIG:
264
+		set_bit(IMA_DIGSIG, &iint->atomic_flags);
265
+		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
266
+					     (const char *)xattr_value,
267
+					     xattr_len,
268
+					     iint->ima_hash->digest,
269
+					     iint->ima_hash->length);
270
+		if (rc == -EOPNOTSUPP) {
271
+			*status = INTEGRITY_UNKNOWN;
272
+			break;
273
+		}
274
+		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
275
+		    func == KEXEC_KERNEL_CHECK)
276
+			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
277
+						     (const char *)xattr_value,
278
+						     xattr_len,
279
+						     iint->ima_hash->digest,
280
+						     iint->ima_hash->length);
281
+		if (rc) {
282
+			*cause = "invalid-signature";
283
+			*status = INTEGRITY_FAIL;
284
+		} else {
285
+			*status = INTEGRITY_PASS;
286
+		}
287
+		break;
288
+	default:
289
+		*status = INTEGRITY_UNKNOWN;
290
+		*cause = "unknown-ima-data";
291
+		break;
292
+	}
293
+
294
+	return rc;
295
+}
296
+
297
+/*
298
+ * modsig_verify - verify modsig signature
299
+ *
300
+ * Verify whether the signature matches the file contents.
301
+ *
302
+ * Return 0 on success, error code otherwise.
303
+ */
304
+static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
305
+			 enum integrity_status *status, const char **cause)
306
+{
307
+	int rc;
308
+
309
+	rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
310
+	if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
311
+	    func == KEXEC_KERNEL_CHECK)
312
+		rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
313
+					     modsig);
314
+	if (rc) {
315
+		*cause = "invalid-signature";
316
+		*status = INTEGRITY_FAIL;
317
+	} else {
318
+		*status = INTEGRITY_PASS;
319
+	}
320
+
321
+	return rc;
322
+}
323
+
324
+/*
325
+ * ima_check_blacklist - determine if the binary is blacklisted.
326
+ *
327
+ * Add the hash of the blacklisted binary to the measurement list, based
328
+ * on policy.
329
+ *
330
+ * Returns -EPERM if the hash is blacklisted.
331
+ */
332
+int ima_check_blacklist(struct integrity_iint_cache *iint,
333
+			const struct modsig *modsig, int pcr)
334
+{
335
+	enum hash_algo hash_algo;
336
+	const u8 *digest = NULL;
337
+	u32 digestsize = 0;
338
+	int rc = 0;
339
+
340
+	if (!(iint->flags & IMA_CHECK_BLACKLIST))
341
+		return 0;
342
+
343
+	if (iint->flags & IMA_MODSIG_ALLOWED && modsig) {
344
+		ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);
345
+
346
+		rc = is_binary_blacklisted(digest, digestsize);
347
+		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
348
+			process_buffer_measurement(NULL, digest, digestsize,
349
+						   "blacklisted-hash", NONE,
350
+						   pcr, NULL);
351
+	}
352
+
353
+	return rc;
354
+}
355
+
356
+/*
204357  * ima_appraise_measurement - appraise file measurement
205358  *
206359  * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
....@@ -212,19 +365,22 @@
212365 			     struct integrity_iint_cache *iint,
213366 			     struct file *file, const unsigned char *filename,
214367 			     struct evm_ima_xattr_data *xattr_value,
215
-			     int xattr_len)
368
+			     int xattr_len, const struct modsig *modsig)
216369 {
217370 	static const char op[] = "appraise_data";
218371 	const char *cause = "unknown";
219372 	struct dentry *dentry = file_dentry(file);
220373 	struct inode *inode = d_backing_inode(dentry);
221374 	enum integrity_status status = INTEGRITY_UNKNOWN;
222
-	int rc = xattr_len, hash_start = 0;
375
+	int rc = xattr_len;
376
+	bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
223377 
224
-	if (!(inode->i_opflags & IOP_XATTR))
378
+	/* If not appraising a modsig, we need an xattr. */
379
+	if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
225380 		return INTEGRITY_UNKNOWN;
226381 
227
-	if (rc <= 0) {
382
+	/* If reading the xattr failed and there's no modsig, error out. */
383
+	if (rc <= 0 && !try_modsig) {
228384 		if (rc && rc != -ENODATA)
229385 			goto out;
230386 
....@@ -240,13 +396,18 @@
240396 		goto out;
241397 	}
242398 
243
-	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint);
399
+	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value,
400
+				 rc < 0 ? 0 : rc, iint);
244401 	switch (status) {
245402 	case INTEGRITY_PASS:
246403 	case INTEGRITY_PASS_IMMUTABLE:
247404 	case INTEGRITY_UNKNOWN:
248405 		break;
249406 	case INTEGRITY_NOXATTRS:	/* No EVM protected xattrs. */
407
+		/* It's fine not to have xattrs when using a modsig. */
408
+		if (try_modsig)
409
+			break;
410
+		fallthrough;
250411 	case INTEGRITY_NOLABEL:		/* No security.evm xattr. */
251412 		cause = "missing-HMAC";
252413 		goto out;
....@@ -257,55 +418,18 @@
257418 		WARN_ONCE(true, "Unexpected integrity status %d\n", status);
258419 	}
259420 
260
-	switch (xattr_value->type) {
261
-	case IMA_XATTR_DIGEST_NG:
262
-		/* first byte contains algorithm id */
263
-		hash_start = 1;
264
-		/* fall through */
265
-	case IMA_XATTR_DIGEST:
266
-		if (iint->flags & IMA_DIGSIG_REQUIRED) {
267
-			cause = "IMA-signature-required";
268
-			status = INTEGRITY_FAIL;
269
-			break;
270
-		}
271
-		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
272
-		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
273
-				iint->ima_hash->length)
274
-			/* xattr length may be longer. md5 hash in previous
275
-			   version occupied 20 bytes in xattr, instead of 16
276
-			 */
277
-			rc = memcmp(&xattr_value->digest[hash_start],
278
-				    iint->ima_hash->digest,
279
-				    iint->ima_hash->length);
280
-		else
281
-			rc = -EINVAL;
282
-		if (rc) {
283
-			cause = "invalid-hash";
284
-			status = INTEGRITY_FAIL;
285
-			break;
286
-		}
287
-		status = INTEGRITY_PASS;
288
-		break;
289
-	case EVM_IMA_XATTR_DIGSIG:
290
-		set_bit(IMA_DIGSIG, &iint->atomic_flags);
291
-		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
292
-					     (const char *)xattr_value, rc,
293
-					     iint->ima_hash->digest,
294
-					     iint->ima_hash->length);
295
-		if (rc == -EOPNOTSUPP) {
296
-			status = INTEGRITY_UNKNOWN;
297
-		} else if (rc) {
298
-			cause = "invalid-signature";
299
-			status = INTEGRITY_FAIL;
300
-		} else {
301
-			status = INTEGRITY_PASS;
302
-		}
303
-		break;
304
-	default:
305
-		status = INTEGRITY_UNKNOWN;
306
-		cause = "unknown-ima-data";
307
-		break;
308
-	}
421
+	if (xattr_value)
422
+		rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
423
+				  &cause);
424
+
425
+	/*
426
+	 * If we have a modsig and either no imasig or the imasig's key isn't
427
+	 * known, then try verifying the modsig.
428
+	 */
429
+	if (try_modsig &&
430
+	    (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
431
+	     rc == -ENOKEY))
432
+		rc = modsig_verify(func, modsig, &status, &cause);
309433 
310434 out:
311435 	/*
....@@ -323,7 +447,7 @@
323447 				    op, cause, rc, 0);
324448 	} else if (status != INTEGRITY_PASS) {
325449 		/* Fix mode, but don't replace file signatures. */
326
-		if ((ima_appraise & IMA_APPRAISE_FIX) &&
450
+		if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig &&
327451 		    (!xattr_value ||
328452 		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
329453 			if (!ima_fix_xattr(dentry, iint))
....@@ -362,7 +486,7 @@
362486 	    !(iint->flags & IMA_HASH))
363487 		return;
364488 
365
-	rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
489
+	rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL);
366490 	if (rc < 0)
367491 		return;
368492