1 /*
2 * COPYRIGHT (c) 2008
3 * The Regents of the University of Michigan
4 * ALL RIGHTS RESERVED
5 *
6 * Permission is granted to use, copy, create derivative works
7 * and redistribute this software and such derivative works
8 * for any purpose, so long as the name of The University of
9 * Michigan is not used in any advertising or publicity
10 * pertaining to the use of distribution of this software
11 * without specific, written prior authorization. If the
12 * above copyright notice or any other identification of the
13 * University of Michigan is included in any copy of any
14 * portion of this software, then the disclaimer below must
15 * also be included.
16 *
17 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
18 * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
19 * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
20 * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
21 * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
22 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
23 * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
24 * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
25 * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
26 * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
27 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGES.
29 */
30
31 /*
32 * Copyright (C) 1998 by the FundsXpress, INC.
33 *
34 * All rights reserved.
35 *
36 * Export of this software from the United States of America may require
37 * a specific license from the United States Government. It is the
38 * responsibility of any person or organization contemplating export to
39 * obtain such a license before exporting.
40 *
41 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
42 * distribute this software and its documentation for any purpose and
43 * without fee is hereby granted, provided that the above copyright
44 * notice appear in all copies and that both that copyright notice and
45 * this permission notice appear in supporting documentation, and that
46 * the name of FundsXpress. not be used in advertising or publicity pertaining
47 * to distribution of the software without specific, written prior
48 * permission. FundsXpress makes no representations about the suitability of
49 * this software for any purpose. It is provided "as is" without express
50 * or implied warranty.
51 *
52 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
53 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
54 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
55 */
56
57 #include <crypto/skcipher.h>
58 #include <linux/err.h>
59 #include <linux/types.h>
60 #include <linux/sunrpc/gss_krb5.h>
61 #include <linux/sunrpc/xdr.h>
62 #include <linux/lcm.h>
63 #include <crypto/hash.h>
64 #include <kunit/visibility.h>
65
66 #include "gss_krb5_internal.h"
67
68 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
69 # define RPCDBG_FACILITY RPCDBG_AUTH
70 #endif
71
72 /**
73 * krb5_nfold - n-fold function
74 * @inbits: number of bits in @in
75 * @in: buffer containing input to fold
76 * @outbits: number of bits in the output buffer
77 * @out: buffer to hold the result
78 *
79 * This is the n-fold function as described in rfc3961, sec 5.1
80 * Taken from MIT Kerberos and modified.
81 */
82 VISIBLE_IF_KUNIT
83 void krb5_nfold(u32 inbits, const u8 *in, u32 outbits, u8 *out)
84 {
85 unsigned long ulcm;
86 int byte, i, msbit;
87
88 /* the code below is more readable if I make these bytes
89 instead of bits */
90
91 inbits >>= 3;
92 outbits >>= 3;
93
94 /* first compute lcm(n,k) */
95 ulcm = lcm(inbits, outbits);
96
97 /* now do the real work */
98
99 memset(out, 0, outbits);
100 byte = 0;
101
102 /* this will end up cycling through k lcm(k,n)/k times, which
103 is correct */
104 for (i = ulcm-1; i >= 0; i--) {
105 /* compute the msbit in k which gets added into this byte */
106 msbit = (
107 /* first, start with the msbit in the first,
108 * unrotated byte */
109 ((inbits << 3) - 1)
110 /* then, for each byte, shift to the right
111 * for each repetition */
112 + (((inbits << 3) + 13) * (i/inbits))
113 /* last, pick out the correct byte within
114 * that shifted repetition */
115 + ((inbits - (i % inbits)) << 3)
116 ) % (inbits << 3);
117
118 /* pull out the byte value itself */
119 byte += (((in[((inbits - 1) - (msbit >> 3)) % inbits] << 8)|
120 (in[((inbits) - (msbit >> 3)) % inbits]))
121 >> ((msbit & 7) + 1)) & 0xff;
122
123 /* do the addition */
124 byte += out[i % outbits];
125 out[i % outbits] = byte & 0xff;
126
127 /* keep around the carry bit, if any */
128 byte >>= 8;
129
130 }
131
132 /* if there's a carry bit left over, add it back in */
133 if (byte) {
134 for (i = outbits - 1; i >= 0; i--) {
135 /* do the addition */
136 byte += out[i];
137 out[i] = byte & 0xff;
138
139 /* keep around the carry bit, if any */
140 byte >>= 8;
141 }
142 }
143 }
144 EXPORT_SYMBOL_IF_KUNIT(krb5_nfold);
145
146 /*
147 * This is the DK (derive_key) function as described in rfc3961, sec 5.1
148 * Taken from MIT Kerberos and modified.
149 */
150 static int krb5_DK(const struct gss_krb5_enctype *gk5e,
151 const struct xdr_netobj *inkey, u8 *rawkey,
152 const struct xdr_netobj *in_constant, gfp_t gfp_mask)
153 {
154 size_t blocksize, keybytes, keylength, n;
155 unsigned char *inblockdata, *outblockdata;
156 struct xdr_netobj inblock, outblock;
157 struct crypto_sync_skcipher *cipher;
158 int ret = -EINVAL;
159
160 keybytes = gk5e->keybytes;
161 keylength = gk5e->keylength;
162
163 if (inkey->len != keylength)
164 goto err_return;
165
166 cipher = crypto_alloc_sync_skcipher(gk5e->encrypt_name, 0, 0);
167 if (IS_ERR(cipher))
168 goto err_return;
169 blocksize = crypto_sync_skcipher_blocksize(cipher);
170 if (crypto_sync_skcipher_setkey(cipher, inkey->data, inkey->len))
171 goto err_free_cipher;
172
173 ret = -ENOMEM;
174 inblockdata = kmalloc(blocksize, gfp_mask);
175 if (inblockdata == NULL)
176 goto err_free_cipher;
177
178 outblockdata = kmalloc(blocksize, gfp_mask);
179 if (outblockdata == NULL)
180 goto err_free_in;
181
182 inblock.data = (char *) inblockdata;
183 inblock.len = blocksize;
184
185 outblock.data = (char *) outblockdata;
186 outblock.len = blocksize;
187
188 /* initialize the input block */
189
190 if (in_constant->len == inblock.len) {
191 memcpy(inblock.data, in_constant->data, inblock.len);
192 } else {
193 krb5_nfold(in_constant->len * 8, in_constant->data,
194 inblock.len * 8, inblock.data);
195 }
196
197 /* loop encrypting the blocks until enough key bytes are generated */
198
199 n = 0;
200 while (n < keybytes) {
201 krb5_encrypt(cipher, NULL, inblock.data, outblock.data,
202 inblock.len);
203
204 if ((keybytes - n) <= outblock.len) {
205 memcpy(rawkey + n, outblock.data, (keybytes - n));
206 break;
207 }
208
209 memcpy(rawkey + n, outblock.data, outblock.len);
210 memcpy(inblock.data, outblock.data, outblock.len);
211 n += outblock.len;
212 }
213
214 ret = 0;
215
216 kfree_sensitive(outblockdata);
217 err_free_in:
218 kfree_sensitive(inblockdata);
219 err_free_cipher:
220 crypto_free_sync_skcipher(cipher);
221 err_return:
222 return ret;
223 }
224
225 /*
226 * This is the identity function, with some sanity checking.
227 */
228 static int krb5_random_to_key_v2(const struct gss_krb5_enctype *gk5e,
229 struct xdr_netobj *randombits,
230 struct xdr_netobj *key)
231 {
232 int ret = -EINVAL;
233
234 if (key->len != 16 && key->len != 32) {
235 dprintk("%s: key->len is %d\n", __func__, key->len);
236 goto err_out;
237 }
238 if (randombits->len != 16 && randombits->len != 32) {
239 dprintk("%s: randombits->len is %d\n",
240 __func__, randombits->len);
241 goto err_out;
242 }
243 if (randombits->len != key->len) {
244 dprintk("%s: randombits->len is %d, key->len is %d\n",
245 __func__, randombits->len, key->len);
246 goto err_out;
247 }
248 memcpy(key->data, randombits->data, key->len);
249 ret = 0;
250 err_out:
251 return ret;
252 }
253
254 /**
255 * krb5_derive_key_v2 - Derive a subkey for an RFC 3962 enctype
256 * @gk5e: Kerberos 5 enctype profile
257 * @inkey: base protocol key
258 * @outkey: OUT: derived key
259 * @label: subkey usage label
260 * @gfp_mask: memory allocation control flags
261 *
262 * Caller sets @outkey->len to the desired length of the derived key.
263 *
264 * On success, returns 0 and fills in @outkey. A negative errno value
265 * is returned on failure.
266 */
267 int krb5_derive_key_v2(const struct gss_krb5_enctype *gk5e,
268 const struct xdr_netobj *inkey,
269 struct xdr_netobj *outkey,
270 const struct xdr_netobj *label,
271 gfp_t gfp_mask)
272 {
273 struct xdr_netobj inblock;
274 int ret;
275
276 inblock.len = gk5e->keybytes;
277 inblock.data = kmalloc(inblock.len, gfp_mask);
278 if (!inblock.data)
279 return -ENOMEM;
280
281 ret = krb5_DK(gk5e, inkey, inblock.data, label, gfp_mask);
282 if (!ret)
283 ret = krb5_random_to_key_v2(gk5e, &inblock, outkey);
284
285 kfree_sensitive(inblock.data);
286 return ret;
287 }
288
289 /*
290 * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k)
291 *
292 * i: A block counter is used with a length of 4 bytes, represented
293 * in big-endian order.
294 *
295 * constant: The label input to the KDF is the usage constant supplied
296 * to the key derivation function
297 *
298 * k: The length of the output key in bits, represented as a 4-byte
299 * string in big-endian order.
300 *
301 * Caller fills in K(i-1) in @step, and receives the result K(i)
302 * in the same buffer.
303 */
304 static int
305 krb5_cmac_Ki(struct crypto_shash *tfm, const struct xdr_netobj *constant,
306 u32 outlen, u32 count, struct xdr_netobj *step)
307 {
308 __be32 k = cpu_to_be32(outlen * 8);
309 SHASH_DESC_ON_STACK(desc, tfm);
310 __be32 i = cpu_to_be32(count);
311 u8 zero = 0;
312 int ret;
313
314 desc->tfm = tfm;
315 ret = crypto_shash_init(desc);
316 if (ret)
317 goto out_err;
318
319 ret = crypto_shash_update(desc, step->data, step->len);
320 if (ret)
321 goto out_err;
322 ret = crypto_shash_update(desc, (u8 *)&i, sizeof(i));
323 if (ret)
324 goto out_err;
325 ret = crypto_shash_update(desc, constant->data, constant->len);
326 if (ret)
327 goto out_err;
328 ret = crypto_shash_update(desc, &zero, sizeof(zero));
329 if (ret)
330 goto out_err;
331 ret = crypto_shash_update(desc, (u8 *)&k, sizeof(k));
332 if (ret)
333 goto out_err;
334 ret = crypto_shash_final(desc, step->data);
335 if (ret)
336 goto out_err;
337
338 out_err:
339 shash_desc_zero(desc);
340 return ret;
341 }
342
343 /**
344 * krb5_kdf_feedback_cmac - Derive a subkey for a Camellia/CMAC-based enctype
345 * @gk5e: Kerberos 5 enctype parameters
346 * @inkey: base protocol key
347 * @outkey: OUT: derived key
348 * @constant: subkey usage label
349 * @gfp_mask: memory allocation control flags
350 *
351 * RFC 6803 Section 3:
352 *
353 * "We use a key derivation function from the family specified in
354 * [SP800-108], Section 5.2, 'KDF in Feedback Mode'."
355 *
356 * n = ceiling(k / 128)
357 * K(0) = zeros
358 * K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k)
359 * DR(key, constant) = k-truncate(K(1) | K(2) | ... | K(n))
360 * KDF-FEEDBACK-CMAC(key, constant) = random-to-key(DR(key, constant))
361 *
362 * Caller sets @outkey->len to the desired length of the derived key (k).
363 *
364 * On success, returns 0 and fills in @outkey. A negative errno value
365 * is returned on failure.
366 */
367 int
368 krb5_kdf_feedback_cmac(const struct gss_krb5_enctype *gk5e,
369 const struct xdr_netobj *inkey,
370 struct xdr_netobj *outkey,
371 const struct xdr_netobj *constant,
372 gfp_t gfp_mask)
373 {
374 struct xdr_netobj step = { .data = NULL };
375 struct xdr_netobj DR = { .data = NULL };
376 unsigned int blocksize, offset;
377 struct crypto_shash *tfm;
378 int n, count, ret;
379
380 /*
381 * This implementation assumes the CMAC used for an enctype's
382 * key derivation is the same as the CMAC used for its
383 * checksumming. This happens to be true for enctypes that
384 * are currently supported by this implementation.
385 */
386 tfm = crypto_alloc_shash(gk5e->cksum_name, 0, 0);
387 if (IS_ERR(tfm)) {
388 ret = PTR_ERR(tfm);
389 goto out;
390 }
391 ret = crypto_shash_setkey(tfm, inkey->data, inkey->len);
392 if (ret)
393 goto out_free_tfm;
394
395 blocksize = crypto_shash_digestsize(tfm);
396 n = (outkey->len + blocksize - 1) / blocksize;
397
398 /* K(0) is all zeroes */
399 ret = -ENOMEM;
400 step.len = blocksize;
401 step.data = kzalloc(step.len, gfp_mask);
402 if (!step.data)
403 goto out_free_tfm;
404
405 DR.len = blocksize * n;
406 DR.data = kmalloc(DR.len, gfp_mask);
407 if (!DR.data)
408 goto out_free_tfm;
409
410 /* XXX: Does not handle partial-block key sizes */
411 for (offset = 0, count = 1; count <= n; count++) {
412 ret = krb5_cmac_Ki(tfm, constant, outkey->len, count, &step);
413 if (ret)
414 goto out_free_tfm;
415
416 memcpy(DR.data + offset, step.data, blocksize);
417 offset += blocksize;
418 }
419
420 /* k-truncate and random-to-key */
421 memcpy(outkey->data, DR.data, outkey->len);
422 ret = 0;
423
424 out_free_tfm:
425 crypto_free_shash(tfm);
426 out:
427 kfree_sensitive(step.data);
428 kfree_sensitive(DR.data);
429 return ret;
430 }
431
432 /*
433 * K1 = HMAC-SHA(key, 0x00000001 | label | 0x00 | k)
434 *
435 * key: The source of entropy from which subsequent keys are derived.
436 *
437 * label: An octet string describing the intended usage of the
438 * derived key.
439 *
440 * k: Length in bits of the key to be outputted, expressed in
441 * big-endian binary representation in 4 bytes.
442 */
443 static int
444 krb5_hmac_K1(struct crypto_shash *tfm, const struct xdr_netobj *label,
445 u32 outlen, struct xdr_netobj *K1)
446 {
447 __be32 k = cpu_to_be32(outlen * 8);
448 SHASH_DESC_ON_STACK(desc, tfm);
449 __be32 one = cpu_to_be32(1);
450 u8 zero = 0;
451 int ret;
452
453 desc->tfm = tfm;
454 ret = crypto_shash_init(desc);
455 if (ret)
456 goto out_err;
457 ret = crypto_shash_update(desc, (u8 *)&one, sizeof(one));
458 if (ret)
459 goto out_err;
460 ret = crypto_shash_update(desc, label->data, label->len);
461 if (ret)
462 goto out_err;
463 ret = crypto_shash_update(desc, &zero, sizeof(zero));
464 if (ret)
465 goto out_err;
466 ret = crypto_shash_update(desc, (u8 *)&k, sizeof(k));
467 if (ret)
468 goto out_err;
469 ret = crypto_shash_final(desc, K1->data);
470 if (ret)
471 goto out_err;
472
473 out_err:
474 shash_desc_zero(desc);
475 return ret;
476 }
477
478 /**
479 * krb5_kdf_hmac_sha2 - Derive a subkey for an AES/SHA2-based enctype
480 * @gk5e: Kerberos 5 enctype policy parameters
481 * @inkey: base protocol key
482 * @outkey: OUT: derived key
483 * @label: subkey usage label
484 * @gfp_mask: memory allocation control flags
485 *
486 * RFC 8009 Section 3:
487 *
488 * "We use a key derivation function from Section 5.1 of [SP800-108],
489 * which uses the HMAC algorithm as the PRF."
490 *
491 * function KDF-HMAC-SHA2(key, label, [context,] k):
492 * k-truncate(K1)
493 *
494 * Caller sets @outkey->len to the desired length of the derived key.
495 *
496 * On success, returns 0 and fills in @outkey. A negative errno value
497 * is returned on failure.
498 */
499 int
500 krb5_kdf_hmac_sha2(const struct gss_krb5_enctype *gk5e,
501 const struct xdr_netobj *inkey,
502 struct xdr_netobj *outkey,
503 const struct xdr_netobj *label,
504 gfp_t gfp_mask)
505 {
506 struct crypto_shash *tfm;
507 struct xdr_netobj K1 = {
508 .data = NULL,
509 };
510 int ret;
511
512 /*
513 * This implementation assumes the HMAC used for an enctype's
514 * key derivation is the same as the HMAC used for its
515 * checksumming. This happens to be true for enctypes that
516 * are currently supported by this implementation.
517 */
518 tfm = crypto_alloc_shash(gk5e->cksum_name, 0, 0);
519 if (IS_ERR(tfm)) {
520 ret = PTR_ERR(tfm);
521 goto out;
522 }
523 ret = crypto_shash_setkey(tfm, inkey->data, inkey->len);
524 if (ret)
525 goto out_free_tfm;
526
527 K1.len = crypto_shash_digestsize(tfm);
528 K1.data = kmalloc(K1.len, gfp_mask);
529 if (!K1.data) {
530 ret = -ENOMEM;
531 goto out_free_tfm;
532 }
533
534 ret = krb5_hmac_K1(tfm, label, outkey->len, &K1);
535 if (ret)
536 goto out_free_tfm;
537
538 /* k-truncate and random-to-key */
539 memcpy(outkey->data, K1.data, outkey->len);
540
541 out_free_tfm:
542 kfree_sensitive(K1.data);
543 crypto_free_shash(tfm);
544 out:
545 return ret;
546 }
547
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