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         sdesc->shash.flags = 0x0;
 116
 117         *sdesc_ret = sdesc;
 118
 119         return 0;
 120
 121 out_free_tfm:
 122         crypto_free_shash(tfm);
 123         return err;
 124 }
 125
 126 static 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  */
 146 static 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
 208 err:
 209         memzero_explicit(dst_orig, dlen);
 210         return err;
 211 }
 212
 213 static 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
 234 err:
 235         kzfree(outbuf);
 236         return ret;
 237 }
 238
 239 long __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 (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
 270                     kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
 271                         ret = -EMSGSIZE;
 272                         goto out1;
 273                 }
 274
 275                 /* get KDF name string */
 276                 hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
 277                 if (IS_ERR(hashname)) {
 278                         ret = PTR_ERR(hashname);
 279                         goto out1;
 280                 }
 281
 282                 /* allocate KDF from the kernel crypto API */
 283                 ret = kdf_alloc(&sdesc, hashname);
 284                 kfree(hashname);
 285                 if (ret)
 286                         goto out1;
 287         }
 288
 289         memset(&dh_inputs, 0, sizeof(dh_inputs));
 290
 291         dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
 292         if (dlen < 0) {
 293                 ret = dlen;
 294                 goto out1;
 295         }
 296         dh_inputs.p_size = dlen;
 297
 298         dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
 299         if (dlen < 0) {
 300                 ret = dlen;
 301                 goto out2;
 302         }
 303         dh_inputs.g_size = dlen;
 304
 305         dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
 306         if (dlen < 0) {
 307                 ret = dlen;
 308                 goto out2;
 309         }
 310         dh_inputs.key_size = dlen;
 311
 312         secretlen = crypto_dh_key_len(&dh_inputs);
 313         secret = kmalloc(secretlen, GFP_KERNEL);
 314         if (!secret) {
 315                 ret = -ENOMEM;
 316                 goto out2;
 317         }
 318         ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
 319         if (ret)
 320                 goto out3;
 321
 322         tfm = crypto_alloc_kpp("dh", CRYPTO_ALG_TYPE_KPP, 0);
 323         if (IS_ERR(tfm)) {
 324                 ret = PTR_ERR(tfm);
 325                 goto out3;
 326         }
 327
 328         ret = crypto_kpp_set_secret(tfm, secret, secretlen);
 329         if (ret)
 330                 goto out4;
 331
 332         outlen = crypto_kpp_maxsize(tfm);
 333
 334         if (!kdfcopy) {
 335                 /*
 336                  * When not using a KDF, buflen 0 is used to read the
 337                  * required buffer length
 338                  */
 339                 if (buflen == 0) {
 340                         ret = outlen;
 341                         goto out4;
 342                 } else if (outlen > buflen) {
 343                         ret = -EOVERFLOW;
 344                         goto out4;
 345                 }
 346         }
 347
 348         outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
 349                          GFP_KERNEL);
 350         if (!outbuf) {
 351                 ret = -ENOMEM;
 352                 goto out4;
 353         }
 354
 355         sg_init_one(&outsg, outbuf, outlen);
 356
 357         req = kpp_request_alloc(tfm, GFP_KERNEL);
 358         if (!req) {
 359                 ret = -ENOMEM;
 360                 goto out5;
 361         }
 362
 363         kpp_request_set_input(req, NULL, 0);
 364         kpp_request_set_output(req, &outsg, outlen);
 365         init_completion(&compl.completion);
 366         kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 367                                  CRYPTO_TFM_REQ_MAY_SLEEP,
 368                                  dh_crypto_done, &compl);
 369
 370         /*
 371          * For DH, generate_public_key and generate_shared_secret are
 372          * the same calculation
 373          */
 374         ret = crypto_kpp_generate_public_key(req);
 375         if (ret == -EINPROGRESS) {
 376                 wait_for_completion(&compl.completion);
 377                 ret = compl.err;
 378                 if (ret)
 379                         goto out6;
 380         }
 381
 382         if (kdfcopy) {
 383                 /*
 384                  * Concatenate SP800-56A otherinfo past DH shared secret -- the
 385                  * input to the KDF is (DH shared secret || otherinfo)
 386                  */
 387                 if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
 388                                    kdfcopy->otherinfolen) != 0) {
 389                         ret = -EFAULT;
 390                         goto out6;
 391                 }
 392
 393                 ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
 394                                             req->dst_len + kdfcopy->otherinfolen,
 395                                             outlen - req->dst_len);
 396         } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
 397                 ret = req->dst_len;
 398         } else {
 399                 ret = -EFAULT;
 400         }
 401
 402 out6:
 403         kpp_request_free(req);
 404 out5:
 405         kzfree(outbuf);
 406 out4:
 407         crypto_free_kpp(tfm);
 408 out3:
 409         kzfree(secret);
 410 out2:
 411         dh_free_data(&dh_inputs);
 412 out1:
 413         kdf_dealloc(sdesc);
 414         return ret;
 415 }
 416
 417 long keyctl_dh_compute(struct keyctl_dh_params __user *params,
 418                        char __user *buffer, size_t buflen,
 419                        struct keyctl_kdf_params __user *kdf)
 420 {
 421         struct keyctl_kdf_params kdfcopy;
 422
 423         if (!kdf)
 424                 return __keyctl_dh_compute(params, buffer, buflen, NULL);
 425
 426         if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
 427                 return -EFAULT;
 428
 429         return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
 430 }