1/* Crypto operations using stored keys
  2 *
  3 * Copyright (c) 2016, Intel Corporation
  4 *
  5 * This program is free software; you can redistribute it and/or
  6 * modify it under the terms of the GNU General Public License
  7 * as published by the Free Software Foundation; either version
  8 * 2 of the License, or (at your option) any later version.
  9 */
 10
 11#include <linux/slab.h>
 12#include <linux/uaccess.h>
 13#include <linux/scatterlist.h>
 14#include <linux/crypto.h>
 15#include <crypto/hash.h>
 16#include <crypto/kpp.h>
 17#include <crypto/dh.h>
 18#include <keys/user-type.h>
 19#include "internal.h"
 20
 21static ssize_t dh_data_from_key(key_serial_t keyid, void **data)
 22{
 23	struct key *key;
 24	key_ref_t key_ref;
 25	long status;
 26	ssize_t ret;
 27
 28	key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
 29	if (IS_ERR(key_ref)) {
 30		ret = -ENOKEY;
 31		goto error;
 32	}
 33
 34	key = key_ref_to_ptr(key_ref);
 35
 36	ret = -EOPNOTSUPP;
 37	if (key->type == &key_type_user) {
 38		down_read(&key->sem);
 39		status = key_validate(key);
 40		if (status == 0) {
 41			const struct user_key_payload *payload;
 42			uint8_t *duplicate;
 43
 44			payload = user_key_payload_locked(key);
 45
 46			duplicate = kmemdup(payload->data, payload->datalen,
 47					    GFP_KERNEL);
 48			if (duplicate) {
 49				*data = duplicate;
 50				ret = payload->datalen;
 51			} else {
 52				ret = -ENOMEM;
 53			}
 54		}
 55		up_read(&key->sem);
 56	}
 57
 58	key_put(key);
 59error:
 60	return ret;
 61}
 62
 63static void dh_free_data(struct dh *dh)
 64{
 65	kzfree(dh->key);
 66	kzfree(dh->p);
 67	kzfree(dh->g);
 68}
 69
 70struct dh_completion {
 71	struct completion completion;
 72	int err;
 73};
 74
 75static void dh_crypto_done(struct crypto_async_request *req, int err)
 76{
 77	struct dh_completion *compl = req->data;
 78
 79	if (err == -EINPROGRESS)
 80		return;
 81
 82	compl->err = err;
 83	complete(&compl->completion);
 84}
 85
 86struct kdf_sdesc {
 87	struct shash_desc shash;
 88	char ctx[];
 89};
 90
 91static int kdf_alloc(struct kdf_sdesc **sdesc_ret, char *hashname)
 92{
 93	struct crypto_shash *tfm;
 94	struct kdf_sdesc *sdesc;
 95	int size;
 96	int err;
 97
 98	/* allocate synchronous hash */
 99	tfm = crypto_alloc_shash(hashname, 0, 0);
100	if (IS_ERR(tfm)) {
101		pr_info("could not allocate digest TFM handle %s\n", hashname);
102		return PTR_ERR(tfm);
103	}
104
105	err = -EINVAL;
106	if (crypto_shash_digestsize(tfm) == 0)
107		goto out_free_tfm;
108
109	err = -ENOMEM;
110	size = sizeof(struct shash_desc) + crypto_shash_descsize(tfm);
111	sdesc = kmalloc(size, GFP_KERNEL);
112	if (!sdesc)
113		goto out_free_tfm;
114	sdesc->shash.tfm = tfm;
115	sdesc->shash.flags = 0x0;
116
117	*sdesc_ret = sdesc;
118
119	return 0;
120
121out_free_tfm:
122	crypto_free_shash(tfm);
123	return err;
124}
125
126static void kdf_dealloc(struct kdf_sdesc *sdesc)
127{
128	if (!sdesc)
129		return;
130
131	if (sdesc->shash.tfm)
132		crypto_free_shash(sdesc->shash.tfm);
133
134	kzfree(sdesc);
135}
136
137/*
138 * Implementation of the KDF in counter mode according to SP800-108 section 5.1
139 * as well as SP800-56A section 5.8.1 (Single-step KDF).
140 *
141 * SP800-56A:
142 * The src pointer is defined as Z || other info where Z is the shared secret
143 * from DH and other info is an arbitrary string (see SP800-56A section
144 * 5.8.1.2).
145 */
146static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
147		   u8 *dst, unsigned int dlen, unsigned int zlen)
148{
149	struct shash_desc *desc = &sdesc->shash;
150	unsigned int h = crypto_shash_digestsize(desc->tfm);
151	int err = 0;
152	u8 *dst_orig = dst;
153	__be32 counter = cpu_to_be32(1);
154
155	while (dlen) {
156		err = crypto_shash_init(desc);
157		if (err)
158			goto err;
159
160		err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32));
161		if (err)
162			goto err;
163
164		if (zlen && h) {
165			u8 tmpbuffer[h];
166			size_t chunk = min_t(size_t, zlen, h);
167			memset(tmpbuffer, 0, chunk);
168
169			do {
170				err = crypto_shash_update(desc, tmpbuffer,
171							  chunk);
172				if (err)
173					goto err;
174
175				zlen -= chunk;
176				chunk = min_t(size_t, zlen, h);
177			} while (zlen);
178		}
179
180		if (src && slen) {
181			err = crypto_shash_update(desc, src, slen);
182			if (err)
183				goto err;
184		}
185
186		if (dlen < h) {
187			u8 tmpbuffer[h];
188
189			err = crypto_shash_final(desc, tmpbuffer);
190			if (err)
191				goto err;
192			memcpy(dst, tmpbuffer, dlen);
193			memzero_explicit(tmpbuffer, h);
194			return 0;
195		} else {
196			err = crypto_shash_final(desc, dst);
197			if (err)
198				goto err;
199
200			dlen -= h;
201			dst += h;
202			counter = cpu_to_be32(be32_to_cpu(counter) + 1);
203		}
204	}
205
206	return 0;
207
208err:
209	memzero_explicit(dst_orig, dlen);
210	return err;
211}
212
213static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
214				 char __user *buffer, size_t buflen,
215				 uint8_t *kbuf, size_t kbuflen, size_t lzero)
216{
217	uint8_t *outbuf = NULL;
218	int ret;
219
220	outbuf = kmalloc(buflen, GFP_KERNEL);
221	if (!outbuf) {
222		ret = -ENOMEM;
223		goto err;
224	}
225
226	ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, buflen, lzero);
227	if (ret)
228		goto err;
229
230	ret = buflen;
231	if (copy_to_user(buffer, outbuf, buflen) != 0)
232		ret = -EFAULT;
233
234err:
235	kzfree(outbuf);
236	return ret;
237}
238
239long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
240			 char __user *buffer, size_t buflen,
241			 struct keyctl_kdf_params *kdfcopy)
242{
243	long ret;
244	ssize_t dlen;
245	int secretlen;
246	int outlen;
247	struct keyctl_dh_params pcopy;
248	struct dh dh_inputs;
249	struct scatterlist outsg;
250	struct dh_completion compl;
251	struct crypto_kpp *tfm;
252	struct kpp_request *req;
253	uint8_t *secret;
254	uint8_t *outbuf;
255	struct kdf_sdesc *sdesc = NULL;
256
257	if (!params || (!buffer && buflen)) {
258		ret = -EINVAL;
259		goto out1;
260	}
261	if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
262		ret = -EFAULT;
263		goto out1;
264	}
265
266	if (kdfcopy) {
267		char *hashname;
268
269		if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) {
270			ret = -EINVAL;
271			goto out1;
272		}
273
274		if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
275		    kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
276			ret = -EMSGSIZE;
277			goto out1;
278		}
279
280		/* get KDF name string */
281		hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
282		if (IS_ERR(hashname)) {
283			ret = PTR_ERR(hashname);
284			goto out1;
285		}
286
287		/* allocate KDF from the kernel crypto API */
288		ret = kdf_alloc(&sdesc, hashname);
289		kfree(hashname);
290		if (ret)
291			goto out1;
292	}
293
294	memset(&dh_inputs, 0, sizeof(dh_inputs));
295
296	dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
297	if (dlen < 0) {
298		ret = dlen;
299		goto out1;
300	}
301	dh_inputs.p_size = dlen;
302
303	dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
304	if (dlen < 0) {
305		ret = dlen;
306		goto out2;
307	}
308	dh_inputs.g_size = dlen;
309
310	dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
311	if (dlen < 0) {
312		ret = dlen;
313		goto out2;
314	}
315	dh_inputs.key_size = dlen;
316
317	secretlen = crypto_dh_key_len(&dh_inputs);
318	secret = kmalloc(secretlen, GFP_KERNEL);
319	if (!secret) {
320		ret = -ENOMEM;
321		goto out2;
322	}
323	ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
324	if (ret)
325		goto out3;
326
327	tfm = crypto_alloc_kpp("dh", CRYPTO_ALG_TYPE_KPP, 0);
328	if (IS_ERR(tfm)) {
329		ret = PTR_ERR(tfm);
330		goto out3;
331	}
332
333	ret = crypto_kpp_set_secret(tfm, secret, secretlen);
334	if (ret)
335		goto out4;
336
337	outlen = crypto_kpp_maxsize(tfm);
338
339	if (!kdfcopy) {
340		/*
341		 * When not using a KDF, buflen 0 is used to read the
342		 * required buffer length
343		 */
344		if (buflen == 0) {
345			ret = outlen;
346			goto out4;
347		} else if (outlen > buflen) {
348			ret = -EOVERFLOW;
349			goto out4;
350		}
351	}
352
353	outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
354			 GFP_KERNEL);
355	if (!outbuf) {
356		ret = -ENOMEM;
357		goto out4;
358	}
359
360	sg_init_one(&outsg, outbuf, outlen);
361
362	req = kpp_request_alloc(tfm, GFP_KERNEL);
363	if (!req) {
364		ret = -ENOMEM;
365		goto out5;
366	}
367
368	kpp_request_set_input(req, NULL, 0);
369	kpp_request_set_output(req, &outsg, outlen);
370	init_completion(&compl.completion);
371	kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
372				 CRYPTO_TFM_REQ_MAY_SLEEP,
373				 dh_crypto_done, &compl);
374
375	/*
376	 * For DH, generate_public_key and generate_shared_secret are
377	 * the same calculation
378	 */
379	ret = crypto_kpp_generate_public_key(req);
380	if (ret == -EINPROGRESS) {
381		wait_for_completion(&compl.completion);
382		ret = compl.err;
383		if (ret)
384			goto out6;
385	}
386
387	if (kdfcopy) {
388		/*
389		 * Concatenate SP800-56A otherinfo past DH shared secret -- the
390		 * input to the KDF is (DH shared secret || otherinfo)
391		 */
392		if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
393				   kdfcopy->otherinfolen) != 0) {
394			ret = -EFAULT;
395			goto out6;
396		}
397
398		ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
399					    req->dst_len + kdfcopy->otherinfolen,
400					    outlen - req->dst_len);
401	} else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
402		ret = req->dst_len;
403	} else {
404		ret = -EFAULT;
405	}
406
407out6:
408	kpp_request_free(req);
409out5:
410	kzfree(outbuf);
411out4:
412	crypto_free_kpp(tfm);
413out3:
414	kzfree(secret);
415out2:
416	dh_free_data(&dh_inputs);
417out1:
418	kdf_dealloc(sdesc);
419	return ret;
420}
421
422long keyctl_dh_compute(struct keyctl_dh_params __user *params,
423		       char __user *buffer, size_t buflen,
424		       struct keyctl_kdf_params __user *kdf)
425{
426	struct keyctl_kdf_params kdfcopy;
427
428	if (!kdf)
429		return __keyctl_dh_compute(params, buffer, buflen, NULL);
430
431	if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
432		return -EFAULT;
433
434	return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
435}