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[32];
 166                         size_t chunk = min_t(size_t, zlen, sizeof(tmpbuffer));
 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, sizeof(tmpbuffer));
 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                 err = crypto_shash_final(desc, dst);
 187                 if (err)
 188                         goto err;
 189
 190                 dlen -= h;
 191                 dst += h;
 192                 counter = cpu_to_be32(be32_to_cpu(counter) + 1);
 193         }
 194
 195         return 0;
 196
 197 err:
 198         memzero_explicit(dst_orig, dlen);
 199         return err;
 200 }
 201
 202 static int keyctl_dh_compute_kdf(struct kdf_sdesc *sdesc,
 203                                  char __user *buffer, size_t buflen,
 204                                  uint8_t *kbuf, size_t kbuflen, size_t lzero)
 205 {
 206         uint8_t *outbuf = NULL;
 207         int ret;
 208         size_t outbuf_len = round_up(buflen,
 209                                      crypto_shash_digestsize(sdesc->shash.tfm));
 210
 211         outbuf = kmalloc(outbuf_len, GFP_KERNEL);
 212         if (!outbuf) {
 213                 ret = -ENOMEM;
 214                 goto err;
 215         }
 216
 217         ret = kdf_ctr(sdesc, kbuf, kbuflen, outbuf, outbuf_len, lzero);
 218         if (ret)
 219                 goto err;
 220
 221         ret = buflen;
 222         if (copy_to_user(buffer, outbuf, buflen) != 0)
 223                 ret = -EFAULT;
 224
 225 err:
 226         kzfree(outbuf);
 227         return ret;
 228 }
 229
 230 long __keyctl_dh_compute(struct keyctl_dh_params __user *params,
 231                          char __user *buffer, size_t buflen,
 232                          struct keyctl_kdf_params *kdfcopy)
 233 {
 234         long ret;
 235         ssize_t dlen;
 236         int secretlen;
 237         int outlen;
 238         struct keyctl_dh_params pcopy;
 239         struct dh dh_inputs;
 240         struct scatterlist outsg;
 241         struct dh_completion compl;
 242         struct crypto_kpp *tfm;
 243         struct kpp_request *req;
 244         uint8_t *secret;
 245         uint8_t *outbuf;
 246         struct kdf_sdesc *sdesc = NULL;
 247
 248         if (!params || (!buffer && buflen)) {
 249                 ret = -EINVAL;
 250                 goto out1;
 251         }
 252         if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
 253                 ret = -EFAULT;
 254                 goto out1;
 255         }
 256
 257         if (kdfcopy) {
 258                 char *hashname;
 259
 260                 if (memchr_inv(kdfcopy->__spare, 0, sizeof(kdfcopy->__spare))) {
 261                         ret = -EINVAL;
 262                         goto out1;
 263                 }
 264
 265                 if (buflen > KEYCTL_KDF_MAX_OUTPUT_LEN ||
 266                     kdfcopy->otherinfolen > KEYCTL_KDF_MAX_OI_LEN) {
 267                         ret = -EMSGSIZE;
 268                         goto out1;
 269                 }
 270
 271                 /* get KDF name string */
 272                 hashname = strndup_user(kdfcopy->hashname, CRYPTO_MAX_ALG_NAME);
 273                 if (IS_ERR(hashname)) {
 274                         ret = PTR_ERR(hashname);
 275                         goto out1;
 276                 }
 277
 278                 /* allocate KDF from the kernel crypto API */
 279                 ret = kdf_alloc(&sdesc, hashname);
 280                 kfree(hashname);
 281                 if (ret)
 282                         goto out1;
 283         }
 284
 285         memset(&dh_inputs, 0, sizeof(dh_inputs));
 286
 287         dlen = dh_data_from_key(pcopy.prime, &dh_inputs.p);
 288         if (dlen < 0) {
 289                 ret = dlen;
 290                 goto out1;
 291         }
 292         dh_inputs.p_size = dlen;
 293
 294         dlen = dh_data_from_key(pcopy.base, &dh_inputs.g);
 295         if (dlen < 0) {
 296                 ret = dlen;
 297                 goto out2;
 298         }
 299         dh_inputs.g_size = dlen;
 300
 301         dlen = dh_data_from_key(pcopy.private, &dh_inputs.key);
 302         if (dlen < 0) {
 303                 ret = dlen;
 304                 goto out2;
 305         }
 306         dh_inputs.key_size = dlen;
 307
 308         secretlen = crypto_dh_key_len(&dh_inputs);
 309         secret = kmalloc(secretlen, GFP_KERNEL);
 310         if (!secret) {
 311                 ret = -ENOMEM;
 312                 goto out2;
 313         }
 314         ret = crypto_dh_encode_key(secret, secretlen, &dh_inputs);
 315         if (ret)
 316                 goto out3;
 317
 318         tfm = crypto_alloc_kpp("dh", CRYPTO_ALG_TYPE_KPP, 0);
 319         if (IS_ERR(tfm)) {
 320                 ret = PTR_ERR(tfm);
 321                 goto out3;
 322         }
 323
 324         ret = crypto_kpp_set_secret(tfm, secret, secretlen);
 325         if (ret)
 326                 goto out4;
 327
 328         outlen = crypto_kpp_maxsize(tfm);
 329
 330         if (!kdfcopy) {
 331                 /*
 332                  * When not using a KDF, buflen 0 is used to read the
 333                  * required buffer length
 334                  */
 335                 if (buflen == 0) {
 336                         ret = outlen;
 337                         goto out4;
 338                 } else if (outlen > buflen) {
 339                         ret = -EOVERFLOW;
 340                         goto out4;
 341                 }
 342         }
 343
 344         outbuf = kzalloc(kdfcopy ? (outlen + kdfcopy->otherinfolen) : outlen,
 345                          GFP_KERNEL);
 346         if (!outbuf) {
 347                 ret = -ENOMEM;
 348                 goto out4;
 349         }
 350
 351         sg_init_one(&outsg, outbuf, outlen);
 352
 353         req = kpp_request_alloc(tfm, GFP_KERNEL);
 354         if (!req) {
 355                 ret = -ENOMEM;
 356                 goto out5;
 357         }
 358
 359         kpp_request_set_input(req, NULL, 0);
 360         kpp_request_set_output(req, &outsg, outlen);
 361         init_completion(&compl.completion);
 362         kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 363                                  CRYPTO_TFM_REQ_MAY_SLEEP,
 364                                  dh_crypto_done, &compl);
 365
 366         /*
 367          * For DH, generate_public_key and generate_shared_secret are
 368          * the same calculation
 369          */
 370         ret = crypto_kpp_generate_public_key(req);
 371         if (ret == -EINPROGRESS) {
 372                 wait_for_completion(&compl.completion);
 373                 ret = compl.err;
 374                 if (ret)
 375                         goto out6;
 376         }
 377
 378         if (kdfcopy) {
 379                 /*
 380                  * Concatenate SP800-56A otherinfo past DH shared secret -- the
 381                  * input to the KDF is (DH shared secret || otherinfo)
 382                  */
 383                 if (copy_from_user(outbuf + req->dst_len, kdfcopy->otherinfo,
 384                                    kdfcopy->otherinfolen) != 0) {
 385                         ret = -EFAULT;
 386                         goto out6;
 387                 }
 388
 389                 ret = keyctl_dh_compute_kdf(sdesc, buffer, buflen, outbuf,
 390                                             req->dst_len + kdfcopy->otherinfolen,
 391                                             outlen - req->dst_len);
 392         } else if (copy_to_user(buffer, outbuf, req->dst_len) == 0) {
 393                 ret = req->dst_len;
 394         } else {
 395                 ret = -EFAULT;
 396         }
 397
 398 out6:
 399         kpp_request_free(req);
 400 out5:
 401         kzfree(outbuf);
 402 out4:
 403         crypto_free_kpp(tfm);
 404 out3:
 405         kzfree(secret);
 406 out2:
 407         dh_free_data(&dh_inputs);
 408 out1:
 409         kdf_dealloc(sdesc);
 410         return ret;
 411 }
 412
 413 long keyctl_dh_compute(struct keyctl_dh_params __user *params,
 414                        char __user *buffer, size_t buflen,
 415                        struct keyctl_kdf_params __user *kdf)
 416 {
 417         struct keyctl_kdf_params kdfcopy;
 418
 419         if (!kdf)
 420                 return __keyctl_dh_compute(params, buffer, buflen, NULL);
 421
 422         if (copy_from_user(&kdfcopy, kdf, sizeof(kdfcopy)) != 0)
 423                 return -EFAULT;
 424
 425         return __keyctl_dh_compute(params, buffer, buflen, &kdfcopy);
 426 }