1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* Crypto operations using stored keys
  3 *
  4 * Copyright (c) 2016, Intel Corporation
  5 */
  6
  7#include <linux/slab.h>
  8#include <linux/uaccess.h>
  9#include <linux/scatterlist.h>
 10#include <linux/crypto.h>
 11#include <crypto/hash.h>
 12#include <crypto/kpp.h>
 13#include <crypto/dh.h>
 14#include <keys/user-type.h>
 15#include "internal.h"
 16
 17static ssize_t dh_data_from_key(key_serial_t keyid, void **data)
 18{
 19	struct key *key;
 20	key_ref_t key_ref;
 21	long status;
 22	ssize_t ret;
 23
 24	key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
 25	if (IS_ERR(key_ref)) {
 26		ret = -ENOKEY;
 27		goto error;
 28	}
 29
 30	key = key_ref_to_ptr(key_ref);
 31
 32	ret = -EOPNOTSUPP;
 33	if (key->type == &key_type_user) {
 34		down_read(&key->sem);
 35		status = key_validate(key);
 36		if (status == 0) {
 37			const struct user_key_payload *payload;
 38			uint8_t *duplicate;
 39
 40			payload = user_key_payload_locked(key);
 41
 42			duplicate = kmemdup(payload->data, payload->datalen,
 43					    GFP_KERNEL);
 44			if (duplicate) {
 45				*data = duplicate;
 46				ret = payload->datalen;
 47			} else {
 48				ret = -ENOMEM;
 49			}
 50		}
 51		up_read(&key->sem);
 52	}
 53
 54	key_put(key);
 55error:
 56	return ret;
 57}
 58
 59static void dh_free_data(struct dh *dh)
 60{
 61	kfree_sensitive(dh->key);
 62	kfree_sensitive(dh->p);
 63	kfree_sensitive(dh->g);
 64}
 65
 66struct dh_completion {
 67	struct completion completion;
 68	int err;
 69};
 70
 71static void dh_crypto_done(struct crypto_async_request *req, int err)
 72{
 73	struct dh_completion *compl = req->data;
 74
 75	if (err == -EINPROGRESS)
 76		return;
 77
 78	compl->err = err;
 79	complete(&compl->completion);
 80}
 81
 82struct kdf_sdesc {
 83	struct shash_desc shash;
 84	char ctx[];
 85};
 86
 87static int kdf_alloc(struct kdf_sdesc **sdesc_ret, char *hashname)
 88{
 89	struct crypto_shash *tfm;
 90	struct kdf_sdesc *sdesc;
 91	int size;
 92	int err;
 93
 94	/* allocate synchronous hash */
 95	tfm = crypto_alloc_shash(hashname, 0, 0);
 96	if (IS_ERR(tfm)) {
 97		pr_info("could not allocate digest TFM handle %s\n", hashname);
 98		return PTR_ERR(tfm);
 99	}
100
101	err = -EINVAL;
102	if (crypto_shash_digestsize(tfm) == 0)
103		goto out_free_tfm;
104
105	err = -ENOMEM;
106	size = sizeof(struct shash_desc) + crypto_shash_descsize(tfm);
107	sdesc = kmalloc(size, GFP_KERNEL);
108	if (!sdesc)
109		goto out_free_tfm;
110	sdesc->shash.tfm = tfm;
111
112	*sdesc_ret = sdesc;
113
114	return 0;
115
116out_free_tfm:
117	crypto_free_shash(tfm);
118	return err;
119}
120
121static void kdf_dealloc(struct kdf_sdesc *sdesc)
122{
123	if (!sdesc)
124		return;
125
126	if (sdesc->shash.tfm)
127		crypto_free_shash(sdesc->shash.tfm);
128
129	kfree_sensitive(sdesc);
130}
131
132/*
133 * Implementation of the KDF in counter mode according to SP800-108 section 5.1
134 * as well as SP800-56A section 5.8.1 (Single-step KDF).
135 *
136 * SP800-56A:
137 * The src pointer is defined as Z || other info where Z is the shared secret
138 * from DH and other info is an arbitrary string (see SP800-56A section
139 * 5.8.1.2).
140 *
141 * 'dlen' must be a multiple of the digest size.
142 */
143static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
144		   u8 *dst, unsigned int dlen, unsigned int zlen)
145{
146	struct shash_desc *desc = &sdesc->shash;
147	unsigned int h = crypto_shash_digestsize(desc->tfm);
148	int err = 0;
149	u8 *dst_orig = dst;
150	__be32 counter = cpu_to_be32(1);
151
152	while (dlen) {
153		err = crypto_shash_init(desc);
154		if (err)
155			goto err;
156
157		err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32));
158		if (err)
159			goto err;
160
161		if (zlen && h) {
162			u8 tmpbuffer[32];
163			size_t chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
164			memset(tmpbuffer, 0, chunk);
165
166			do {
167				err = crypto_shash_update(desc, tmpbuffer,
168							  chunk);
169				if (err)
170					goto err;
171
172				zlen -= chunk;
173				chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
174			} while (zlen);
175		}
176
177		if (src && slen) {
178			err = crypto_shash_update(desc, src, slen);
179			if (err)
180				goto err;
181		}
182
183		err = crypto_shash_final(desc, dst);
184		if (err)
185			goto err;
186
187		dlen -= h;
188		dst += h;
189		counter = cpu_to_be32(be32_to_cpu(counter) + 1);
190	}
191
192	return 0;
193
194err:
195	memzero_explicit(dst_orig, dlen);
196	return err;
197}
198
199static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
200				 char __user *buffer, size_t buflen,
201				 uint8_t *kbuf, size_t kbuflen, size_t lzero)
202{
203	uint8_t *outbuf = NULL;
204	int ret;
205	size_t outbuf_len = roundup(buflen,
206				    crypto_shash_digestsize(sdesc->shash.tfm));
207
208	outbuf = kmalloc(outbuf_len, GFP_KERNEL);
209	if (!outbuf) {
210		ret = -ENOMEM;
211		goto err;
212	}
213
214	ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero);
215	if (ret)
216		goto err;
217
218	ret = buflen;
219	if (copy_to_user(buffer, outbuf, buflen) != 0)
220		ret = -EFAULT;
221
222err:
223	kfree_sensitive(outbuf);
224	return ret;
225}
226
227long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
228			 char __user *buffer, size_t buflen,
229			 struct keyctl_kdf_params *kdfcopy)
230{
231	long ret;
232	ssize_t dlen;
233	int secretlen;
234	int outlen;
235	struct keyctl_dh_params pcopy;
236	struct dh dh_inputs;
237	struct scatterlist outsg;
238	struct dh_completion compl;
239	struct crypto_kpp *tfm;
240	struct kpp_request *req;
241	uint8_t *secret;
242	uint8_t *outbuf;
243	struct kdf_sdesc *sdesc = NULL;
244
245	if (!params || (!buffer && buflen)) {
246		ret = -EINVAL;
247		goto out1;
248	}
249	if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
250		ret = -EFAULT;
251		goto out1;
252	}
253
254	if (kdfcopy) {
255		char *hashname;
256
257		if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) {
258			ret = -EINVAL;
259			goto out1;
260		}
261
262		if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
263		    kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
264			ret = -EMSGSIZE;
265			goto out1;
266		}
267
268		/* get KDF name string */
269		hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
270		if (IS_ERR(hashname)) {
271			ret = PTR_ERR(hashname);
272			goto out1;
273		}
274
275		/* allocate KDF from the kernel crypto API */
276		ret = kdf_alloc(&sdesc, hashname);
277		kfree(hashname);
278		if (ret)
279			goto out1;
280	}
281
282	memset(&dh_inputs, 0, sizeof(dh_inputs));
283
284	dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
285	if (dlen < 0) {
286		ret = dlen;
287		goto out1;
288	}
289	dh_inputs.p_size = dlen;
290
291	dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
292	if (dlen < 0) {
293		ret = dlen;
294		goto out2;
295	}
296	dh_inputs.g_size = dlen;
297
298	dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
299	if (dlen < 0) {
300		ret = dlen;
301		goto out2;
302	}
303	dh_inputs.key_size = dlen;
304
305	secretlen = crypto_dh_key_len(&dh_inputs);
306	secret = kmalloc(secretlen, GFP_KERNEL);
307	if (!secret) {
308		ret = -ENOMEM;
309		goto out2;
310	}
311	ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
312	if (ret)
313		goto out3;
314
315	tfm = crypto_alloc_kpp("dh", 0, 0);
316	if (IS_ERR(tfm)) {
317		ret = PTR_ERR(tfm);
318		goto out3;
319	}
320
321	ret = crypto_kpp_set_secret(tfm, secret, secretlen);
322	if (ret)
323		goto out4;
324
325	outlen = crypto_kpp_maxsize(tfm);
326
327	if (!kdfcopy) {
328		/*
329		 * When not using a KDF, buflen 0 is used to read the
330		 * required buffer length
331		 */
332		if (buflen == 0) {
333			ret = outlen;
334			goto out4;
335		} else if (outlen > buflen) {
336			ret = -EOVERFLOW;
337			goto out4;
338		}
339	}
340
341	outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
342			 GFP_KERNEL);
343	if (!outbuf) {
344		ret = -ENOMEM;
345		goto out4;
346	}
347
348	sg_init_one(&outsg, outbuf, outlen);
349
350	req = kpp_request_alloc(tfm, GFP_KERNEL);
351	if (!req) {
352		ret = -ENOMEM;
353		goto out5;
354	}
355
356	kpp_request_set_input(req, NULL, 0);
357	kpp_request_set_output(req, &outsg, outlen);
358	init_completion(&compl.completion);
359	kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
360				 CRYPTO_TFM_REQ_MAY_SLEEP,
361				 dh_crypto_done, &compl);
362
363	/*
364	 * For DH, generate_public_key and generate_shared_secret are
365	 * the same calculation
366	 */
367	ret = crypto_kpp_generate_public_key(req);
368	if (ret == -EINPROGRESS) {
369		wait_for_completion(&compl.completion);
370		ret = compl.err;
371		if (ret)
372			goto out6;
373	}
374
375	if (kdfcopy) {
376		/*
377		 * Concatenate SP800-56A otherinfo past DH shared secret -- the
378		 * input to the KDF is (DH shared secret || otherinfo)
379		 */
380		if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
381				   kdfcopy->otherinfolen) != 0) {
382			ret = -EFAULT;
383			goto out6;
384		}
385
386		ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
387					    req->dst_len + kdfcopy->otherinfolen,
388					    outlen - req->dst_len);
389	} else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
390		ret = req->dst_len;
391	} else {
392		ret = -EFAULT;
393	}
394
395out6:
396	kpp_request_free(req);
397out5:
398	kfree_sensitive(outbuf);
399out4:
400	crypto_free_kpp(tfm);
401out3:
402	kfree_sensitive(secret);
403out2:
404	dh_free_data(&dh_inputs);
405out1:
406	kdf_dealloc(sdesc);
407	return ret;
408}
409
410long keyctl_dh_compute(struct keyctl_dh_params __user *params,
411		       char __user *buffer, size_t buflen,
412		       struct keyctl_kdf_params __user *kdf)
413{
414	struct keyctl_kdf_params kdfcopy;
415
416	if (!kdf)
417		return __keyctl_dh_compute(params, buffer, buflen, NULL);
418
419	if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
420		return -EFAULT;
421
422	return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
423}