security/keys/dh.c

   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
  21 static 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);
  59 error:
  60         return ret;
  61 }
  62
  63 static void dh_free_data(struct dh *dh)
  64 {
  65         kzfree(dh->key);
  66         kzfree(dh->p);
  67         kzfree(dh->g);
  68 }
  69
  70 struct dh_completion {
  71         struct completion completion;
  72         int err;
  73 };
  74
  75 static 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
  86 struct kdf_sdesc {
  87         struct shash_desc shash;
  88         char ctx[];
  89 };
  90
  91 static 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
 116         *sdesc_ret = sdesc;
 117
 118         return 0;
 119
 120 out_free_tfm:
 121         crypto_free_shash(tfm);
 122         return err;
 123 }
 124
 125 static void kdf_dealloc(struct kdf_sdesc *sdesc)
 126 {
 127         if (!sdesc)
 128                 return;
 129
 130         if (sdesc->shash.tfm)
 131                 crypto_free_shash(sdesc->shash.tfm);
 132
 133         kzfree(sdesc);
 134 }
 135
 136 /*
 137  * Implementation of the KDF in counter mode according to SP800-108 section 5.1
 138  * as well as SP800-56A section 5.8.1 (Single-step KDF).
 139  *
 140  * SP800-56A:
 141  * The src pointer is defined as Z || other info where Z is the shared secret
 142  * from DH and other info is an arbitrary string (see SP800-56A section
 143  * 5.8.1.2).
 144  *
 145  * 'dlen' must be a multiple of the digest size.
 146  */
 147 static int kdf_ctr(struct kdf_sdesc *sdesc, const u8 *src, unsigned int slen,
 148                    u8 *dst, unsigned int dlen, unsigned int zlen)
 149 {
 150         struct shash_desc *desc = &sdesc->shash;
 151         unsigned int h = crypto_shash_digestsize(desc->tfm);
 152         int err = 0;
 153         u8 *dst_orig = dst;
 154         __be32 counter = cpu_to_be32(1);
 155
 156         while (dlen) {
 157                 err = crypto_shash_init(desc);
 158                 if (err)
 159                         goto err;
 160
 161                 err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32));
 162                 if (err)
 163                         goto err;
 164
 165                 if (zlen && h) {
 166                         u8 tmpbuffer[32];
 167                         size_t chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
 168                         memset(tmpbuffer, 0, chunk);
 169
 170                         do {
 171                                 err = crypto_shash_update(desc, tmpbuffer,
 172                                                           chunk);
 173                                 if (err)
 174                                         goto err;
 175
 176                                 zlen -= chunk;
 177                                 chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
 178                         } while (zlen);
 179                 }
 180
 181                 if (src && slen) {
 182                         err = crypto_shash_update(desc, src, slen);
 183                         if (err)
 184                                 goto err;
 185                 }
 186
 187                 err = crypto_shash_final(desc, dst);
 188                 if (err)
 189                         goto err;
 190
 191                 dlen -= h;
 192                 dst += h;
 193                 counter = cpu_to_be32(be32_to_cpu(counter) + 1);
 194         }
 195
 196         return 0;
 197
 198 err:
 199         memzero_explicit(dst_orig, dlen);
 200         return err;
 201 }
 202
 203 static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
 204                                  char __user *buffer, size_t buflen,
 205                                  uint8_t *kbuf, size_t kbuflen, size_t lzero)
 206 {
 207         uint8_t *outbuf = NULL;
 208         int ret;
 209         size_t outbuf_len = roundup(buflen,
 210                                     crypto_shash_digestsize(sdesc->shash.tfm));
 211
 212         outbuf = kmalloc(outbuf_len, GFP_KERNEL);
 213         if (!outbuf) {
 214                 ret = -ENOMEM;
 215                 goto err;
 216         }
 217
 218         ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero);
 219         if (ret)
 220                 goto err;
 221
 222         ret = buflen;
 223         if (copy_to_user(buffer, outbuf, buflen) != 0)
 224                 ret = -EFAULT;
 225
 226 err:
 227         kzfree(outbuf);
 228         return ret;
 229 }
 230
 231 long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
 232                          char __user *buffer, size_t buflen,
 233                          struct keyctl_kdf_params *kdfcopy)
 234 {
 235         long ret;
 236         ssize_t dlen;
 237         int secretlen;
 238         int outlen;
 239         struct keyctl_dh_params pcopy;
 240         struct dh dh_inputs;
 241         struct scatterlist outsg;
 242         struct dh_completion compl;
 243         struct crypto_kpp *tfm;
 244         struct kpp_request *req;
 245         uint8_t *secret;
 246         uint8_t *outbuf;
 247         struct kdf_sdesc *sdesc = NULL;
 248
 249         if (!params || (!buffer && buflen)) {
 250                 ret = -EINVAL;
 251                 goto out1;
 252         }
 253         if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
 254                 ret = -EFAULT;
 255                 goto out1;
 256         }
 257
 258         if (kdfcopy) {
 259                 char *hashname;
 260
 261                 if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) {
 262                         ret = -EINVAL;
 263                         goto out1;
 264                 }
 265
 266                 if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
 267                     kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
 268                         ret = -EMSGSIZE;
 269                         goto out1;
 270                 }
 271
 272                 /* get KDF name string */
 273                 hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
 274                 if (IS_ERR(hashname)) {
 275                         ret = PTR_ERR(hashname);
 276                         goto out1;
 277                 }
 278
 279                 /* allocate KDF from the kernel crypto API */
 280                 ret = kdf_alloc(&sdesc, hashname);
 281                 kfree(hashname);
 282                 if (ret)
 283                         goto out1;
 284         }
 285
 286         memset(&dh_inputs, 0, sizeof(dh_inputs));
 287
 288         dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
 289         if (dlen < 0) {
 290                 ret = dlen;
 291                 goto out1;
 292         }
 293         dh_inputs.p_size = dlen;
 294
 295         dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
 296         if (dlen < 0) {
 297                 ret = dlen;
 298                 goto out2;
 299         }
 300         dh_inputs.g_size = dlen;
 301
 302         dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
 303         if (dlen < 0) {
 304                 ret = dlen;
 305                 goto out2;
 306         }
 307         dh_inputs.key_size = dlen;
 308
 309         secretlen = crypto_dh_key_len(&dh_inputs);
 310         secret = kmalloc(secretlen, GFP_KERNEL);
 311         if (!secret) {
 312                 ret = -ENOMEM;
 313                 goto out2;
 314         }
 315         ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
 316         if (ret)
 317                 goto out3;
 318
 319         tfm = crypto_alloc_kpp("dh", 0, 0);
 320         if (IS_ERR(tfm)) {
 321                 ret = PTR_ERR(tfm);
 322                 goto out3;
 323         }
 324
 325         ret = crypto_kpp_set_secret(tfm, secret, secretlen);
 326         if (ret)
 327                 goto out4;
 328
 329         outlen = crypto_kpp_maxsize(tfm);
 330
 331         if (!kdfcopy) {
 332                 /*
 333                  * When not using a KDF, buflen 0 is used to read the
 334                  * required buffer length
 335                  */
 336                 if (buflen == 0) {
 337                         ret = outlen;
 338                         goto out4;
 339                 } else if (outlen > buflen) {
 340                         ret = -EOVERFLOW;
 341                         goto out4;
 342                 }
 343         }
 344
 345         outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
 346                          GFP_KERNEL);
 347         if (!outbuf) {
 348                 ret = -ENOMEM;
 349                 goto out4;
 350         }
 351
 352         sg_init_one(&outsg, outbuf, outlen);
 353
 354         req = kpp_request_alloc(tfm, GFP_KERNEL);
 355         if (!req) {
 356                 ret = -ENOMEM;
 357                 goto out5;
 358         }
 359
 360         kpp_request_set_input(req, NULL, 0);
 361         kpp_request_set_output(req, &outsg, outlen);
 362         init_completion(&compl.completion);
 363         kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 364                                  CRYPTO_TFM_REQ_MAY_SLEEP,
 365                                  dh_crypto_done, &compl);
 366
 367         /*
 368          * For DH, generate_public_key and generate_shared_secret are
 369          * the same calculation
 370          */
 371         ret = crypto_kpp_generate_public_key(req);
 372         if (ret == -EINPROGRESS) {
 373                 wait_for_completion(&compl.completion);
 374                 ret = compl.err;
 375                 if (ret)
 376                         goto out6;
 377         }
 378
 379         if (kdfcopy) {
 380                 /*
 381                  * Concatenate SP800-56A otherinfo past DH shared secret -- the
 382                  * input to the KDF is (DH shared secret || otherinfo)
 383                  */
 384                 if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
 385                                    kdfcopy->otherinfolen) != 0) {
 386                         ret = -EFAULT;
 387                         goto out6;
 388                 }
 389
 390                 ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
 391                                             req->dst_len + kdfcopy->otherinfolen,
 392                                             outlen - req->dst_len);
 393         } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
 394                 ret = req->dst_len;
 395         } else {
 396                 ret = -EFAULT;
 397         }
 398
 399 out6:
 400         kpp_request_free(req);
 401 out5:
 402         kzfree(outbuf);
 403 out4:
 404         crypto_free_kpp(tfm);
 405 out3:
 406         kzfree(secret);
 407 out2:
 408         dh_free_data(&dh_inputs);
 409 out1:
 410         kdf_dealloc(sdesc);
 411         return ret;
 412 }
 413
 414 long keyctl_dh_compute(struct keyctl_dh_params __user *params,
 415                        char __user *buffer, size_t buflen,
 416                        struct keyctl_kdf_params __user *kdf)
 417 {
 418         struct keyctl_kdf_params kdfcopy;
 419
 420         if (!kdf)
 421                 return __keyctl_dh_compute(params, buffer, buflen, NULL);
 422
 423         if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
 424                 return -EFAULT;
 425
 426         return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
 427 }