net/tls/tls_device_fallback.c

   1 /* Copyright (c) 2018, Mellanox Technologies All rights reserved.
   2  *
   3  * This software is available to you under a choice of one of two
   4  * licenses.  You may choose to be licensed under the terms of the GNU
   5  * General Public License (GPL) Version 2, available from the file
   6  * COPYING in the main directory of this source tree, or the
   7  * OpenIB.org BSD license below:
   8  *
   9  *     Redistribution and use in source and binary forms, with or
  10  *     without modification, are permitted provided that the following
  11  *     conditions are met:
  12  *
  13  *      - Redistributions of source code must retain the above
  14  *        copyright notice, this list of conditions and the following
  15  *        disclaimer.
  16  *
  17  *      - Redistributions in binary form must reproduce the above
  18  *        copyright notice, this list of conditions and the following
  19  *        disclaimer in the documentation and/or other materials
  20  *        provided with the distribution.
  21  *
  22  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  26  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  27  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  28  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  29  * SOFTWARE.
  30  */
  31
  32 #include <net/tls.h>
  33 #include <crypto/aead.h>
  34 #include <crypto/scatterwalk.h>
  35 #include <net/ip6_checksum.h>
  36
  37 static void chain_to_walk(struct scatterlist *sg, struct scatter_walk *walk)
  38 {
  39         struct scatterlist *src = walk->sg;
  40         int diff = walk->offset - src->offset;
  41
  42         sg_set_page(sg, sg_page(src),
  43                     src->length - diff, walk->offset);
  44
  45         scatterwalk_crypto_chain(sg, sg_next(src), 2);
  46 }
  47
  48 static int tls_enc_record(struct aead_request *aead_req,
  49                           struct crypto_aead *aead, char *aad,
  50                           char *iv, __be64 rcd_sn,
  51                           struct scatter_walk *in,
  52                           struct scatter_walk *out, int *in_len)
  53 {
  54         unsigned char buf[TLS_HEADER_SIZE + TLS_CIPHER_AES_GCM_128_IV_SIZE];
  55         struct scatterlist sg_in[3];
  56         struct scatterlist sg_out[3];
  57         u16 len;
  58         int rc;
  59
  60         len = min_t(int, *in_len, ARRAY_SIZE(buf));
  61
  62         scatterwalk_copychunks(buf, in, len, 0);
  63         scatterwalk_copychunks(buf, out, len, 1);
  64
  65         *in_len -= len;
  66         if (!*in_len)
  67                 return 0;
  68
  69         scatterwalk_pagedone(in, 0, 1);
  70         scatterwalk_pagedone(out, 1, 1);
  71
  72         len = buf[4] | (buf[3] << 8);
  73         len -= TLS_CIPHER_AES_GCM_128_IV_SIZE;
  74
  75         tls_make_aad(aad, len - TLS_CIPHER_AES_GCM_128_TAG_SIZE,
  76                      (char *)&rcd_sn, sizeof(rcd_sn), buf[0]);
  77
  78         memcpy(iv + TLS_CIPHER_AES_GCM_128_SALT_SIZE, buf + TLS_HEADER_SIZE,
  79                TLS_CIPHER_AES_GCM_128_IV_SIZE);
  80
  81         sg_init_table(sg_in, ARRAY_SIZE(sg_in));
  82         sg_init_table(sg_out, ARRAY_SIZE(sg_out));
  83         sg_set_buf(sg_in, aad, TLS_AAD_SPACE_SIZE);
  84         sg_set_buf(sg_out, aad, TLS_AAD_SPACE_SIZE);
  85         chain_to_walk(sg_in + 1, in);
  86         chain_to_walk(sg_out + 1, out);
  87
  88         *in_len -= len;
  89         if (*in_len < 0) {
  90                 *in_len += TLS_CIPHER_AES_GCM_128_TAG_SIZE;
  91                 /* the input buffer doesn't contain the entire record.
  92                  * trim len accordingly. The resulting authentication tag
  93                  * will contain garbage, but we don't care, so we won't
  94                  * include any of it in the output skb
  95                  * Note that we assume the output buffer length
  96                  * is larger then input buffer length + tag size
  97                  */
  98                 if (*in_len < 0)
  99                         len += *in_len;
 100
 101                 *in_len = 0;
 102         }
 103
 104         if (*in_len) {
 105                 scatterwalk_copychunks(NULL, in, len, 2);
 106                 scatterwalk_pagedone(in, 0, 1);
 107                 scatterwalk_copychunks(NULL, out, len, 2);
 108                 scatterwalk_pagedone(out, 1, 1);
 109         }
 110
 111         len -= TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 112         aead_request_set_crypt(aead_req, sg_in, sg_out, len, iv);
 113
 114         rc = crypto_aead_encrypt(aead_req);
 115
 116         return rc;
 117 }
 118
 119 static void tls_init_aead_request(struct aead_request *aead_req,
 120                                   struct crypto_aead *aead)
 121 {
 122         aead_request_set_tfm(aead_req, aead);
 123         aead_request_set_ad(aead_req, TLS_AAD_SPACE_SIZE);
 124 }
 125
 126 static struct aead_request *tls_alloc_aead_request(struct crypto_aead *aead,
 127                                                    gfp_t flags)
 128 {
 129         unsigned int req_size = sizeof(struct aead_request) +
 130                 crypto_aead_reqsize(aead);
 131         struct aead_request *aead_req;
 132
 133         aead_req = kzalloc(req_size, flags);
 134         if (aead_req)
 135                 tls_init_aead_request(aead_req, aead);
 136         return aead_req;
 137 }
 138
 139 static int tls_enc_records(struct aead_request *aead_req,
 140                            struct crypto_aead *aead, struct scatterlist *sg_in,
 141                            struct scatterlist *sg_out, char *aad, char *iv,
 142                            u64 rcd_sn, int len)
 143 {
 144         struct scatter_walk out, in;
 145         int rc;
 146
 147         scatterwalk_start(&in, sg_in);
 148         scatterwalk_start(&out, sg_out);
 149
 150         do {
 151                 rc = tls_enc_record(aead_req, aead, aad, iv,
 152                                     cpu_to_be64(rcd_sn), &in, &out, &len);
 153                 rcd_sn++;
 154
 155         } while (rc == 0 && len);
 156
 157         scatterwalk_done(&in, 0, 0);
 158         scatterwalk_done(&out, 1, 0);
 159
 160         return rc;
 161 }
 162
 163 /* Can't use icsk->icsk_af_ops->send_check here because the ip addresses
 164  * might have been changed by NAT.
 165  */
 166 static void update_chksum(struct sk_buff *skb, int headln)
 167 {
 168         struct tcphdr *th = tcp_hdr(skb);
 169         int datalen = skb->len - headln;
 170         const struct ipv6hdr *ipv6h;
 171         const struct iphdr *iph;
 172
 173         /* We only changed the payload so if we are using partial we don't
 174          * need to update anything.
 175          */
 176         if (likely(skb->ip_summed == CHECKSUM_PARTIAL))
 177                 return;
 178
 179         skb->ip_summed = CHECKSUM_PARTIAL;
 180         skb->csum_start = skb_transport_header(skb) - skb->head;
 181         skb->csum_offset = offsetof(struct tcphdr, check);
 182
 183         if (skb->sk->sk_family == AF_INET6) {
 184                 ipv6h = ipv6_hdr(skb);
 185                 th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 186                                              datalen, IPPROTO_TCP, 0);
 187         } else {
 188                 iph = ip_hdr(skb);
 189                 th->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
 190                                                IPPROTO_TCP, 0);
 191         }
 192 }
 193
 194 static void complete_skb(struct sk_buff *nskb, struct sk_buff *skb, int headln)
 195 {
 196         skb_copy_header(nskb, skb);
 197
 198         skb_put(nskb, skb->len);
 199         memcpy(nskb->data, skb->data, headln);
 200         update_chksum(nskb, headln);
 201
 202         nskb->destructor = skb->destructor;
 203         nskb->sk = skb->sk;
 204         skb->destructor = NULL;
 205         skb->sk = NULL;
 206         refcount_add(nskb->truesize - skb->truesize,
 207                      &nskb->sk->sk_wmem_alloc);
 208 }
 209
 210 /* This function may be called after the user socket is already
 211  * closed so make sure we don't use anything freed during
 212  * tls_sk_proto_close here
 213  */
 214
 215 static int fill_sg_in(struct scatterlist *sg_in,
 216                       struct sk_buff *skb,
 217                       struct tls_offload_context_tx *ctx,
 218                       u64 *rcd_sn,
 219                       s32 *sync_size,
 220                       int *resync_sgs)
 221 {
 222         int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 223         int payload_len = skb->len - tcp_payload_offset;
 224         u32 tcp_seq = ntohl(tcp_hdr(skb)->seq);
 225         struct tls_record_info *record;
 226         unsigned long flags;
 227         int remaining;
 228         int i;
 229
 230         spin_lock_irqsave(&ctx->lock, flags);
 231         record = tls_get_record(ctx, tcp_seq, rcd_sn);
 232         if (!record) {
 233                 spin_unlock_irqrestore(&ctx->lock, flags);
 234                 WARN(1, "Record not found for seq %u\n", tcp_seq);
 235                 return -EINVAL;
 236         }
 237
 238         *sync_size = tcp_seq - tls_record_start_seq(record);
 239         if (*sync_size < 0) {
 240                 int is_start_marker = tls_record_is_start_marker(record);
 241
 242                 spin_unlock_irqrestore(&ctx->lock, flags);
 243                 /* This should only occur if the relevant record was
 244                  * already acked. In that case it should be ok
 245                  * to drop the packet and avoid retransmission.
 246                  *
 247                  * There is a corner case where the packet contains
 248                  * both an acked and a non-acked record.
 249                  * We currently don't handle that case and rely
 250                  * on TCP to retranmit a packet that doesn't contain
 251                  * already acked payload.
 252                  */
 253                 if (!is_start_marker)
 254                         *sync_size = 0;
 255                 return -EINVAL;
 256         }
 257
 258         remaining = *sync_size;
 259         for (i = 0; remaining > 0; i++) {
 260                 skb_frag_t *frag = &record->frags[i];
 261
 262                 __skb_frag_ref(frag);
 263                 sg_set_page(sg_in + i, skb_frag_page(frag),
 264                             skb_frag_size(frag), frag->page_offset);
 265
 266                 remaining -= skb_frag_size(frag);
 267
 268                 if (remaining < 0)
 269                         sg_in[i].length += remaining;
 270         }
 271         *resync_sgs = i;
 272
 273         spin_unlock_irqrestore(&ctx->lock, flags);
 274         if (skb_to_sgvec(skb, &sg_in[i], tcp_payload_offset, payload_len) < 0)
 275                 return -EINVAL;
 276
 277         return 0;
 278 }
 279
 280 static void fill_sg_out(struct scatterlist sg_out[3], void *buf,
 281                         struct tls_context *tls_ctx,
 282                         struct sk_buff *nskb,
 283                         int tcp_payload_offset,
 284                         int payload_len,
 285                         int sync_size,
 286                         void *dummy_buf)
 287 {
 288         sg_set_buf(&sg_out[0], dummy_buf, sync_size);
 289         sg_set_buf(&sg_out[1], nskb->data + tcp_payload_offset, payload_len);
 290         /* Add room for authentication tag produced by crypto */
 291         dummy_buf += sync_size;
 292         sg_set_buf(&sg_out[2], dummy_buf, TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 293 }
 294
 295 static struct sk_buff *tls_enc_skb(struct tls_context *tls_ctx,
 296                                    struct scatterlist sg_out[3],
 297                                    struct scatterlist *sg_in,
 298                                    struct sk_buff *skb,
 299                                    s32 sync_size, u64 rcd_sn)
 300 {
 301         int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 302         struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 303         int payload_len = skb->len - tcp_payload_offset;
 304         void *buf, *iv, *aad, *dummy_buf;
 305         struct aead_request *aead_req;
 306         struct sk_buff *nskb = NULL;
 307         int buf_len;
 308
 309         aead_req = tls_alloc_aead_request(ctx->aead_send, GFP_ATOMIC);
 310         if (!aead_req)
 311                 return NULL;
 312
 313         buf_len = TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 314                   TLS_CIPHER_AES_GCM_128_IV_SIZE +
 315                   TLS_AAD_SPACE_SIZE +
 316                   sync_size +
 317                   TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 318         buf = kmalloc(buf_len, GFP_ATOMIC);
 319         if (!buf)
 320                 goto free_req;
 321
 322         iv = buf;
 323         memcpy(iv, tls_ctx->crypto_send.aes_gcm_128.salt,
 324                TLS_CIPHER_AES_GCM_128_SALT_SIZE);
 325         aad = buf + TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 326               TLS_CIPHER_AES_GCM_128_IV_SIZE;
 327         dummy_buf = aad + TLS_AAD_SPACE_SIZE;
 328
 329         nskb = alloc_skb(skb_headroom(skb) + skb->len, GFP_ATOMIC);
 330         if (!nskb)
 331                 goto free_buf;
 332
 333         skb_reserve(nskb, skb_headroom(skb));
 334
 335         fill_sg_out(sg_out, buf, tls_ctx, nskb, tcp_payload_offset,
 336                     payload_len, sync_size, dummy_buf);
 337
 338         if (tls_enc_records(aead_req, ctx->aead_send, sg_in, sg_out, aad, iv,
 339                             rcd_sn, sync_size + payload_len) < 0)
 340                 goto free_nskb;
 341
 342         complete_skb(nskb, skb, tcp_payload_offset);
 343
 344         /* validate_xmit_skb_list assumes that if the skb wasn't segmented
 345          * nskb->prev will point to the skb itself
 346          */
 347         nskb->prev = nskb;
 348
 349 free_buf:
 350         kfree(buf);
 351 free_req:
 352         kfree(aead_req);
 353         return nskb;
 354 free_nskb:
 355         kfree_skb(nskb);
 356         nskb = NULL;
 357         goto free_buf;
 358 }
 359
 360 static struct sk_buff *tls_sw_fallback(struct sock *sk, struct sk_buff *skb)
 361 {
 362         int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 363         struct tls_context *tls_ctx = tls_get_ctx(sk);
 364         struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 365         int payload_len = skb->len - tcp_payload_offset;
 366         struct scatterlist *sg_in, sg_out[3];
 367         struct sk_buff *nskb = NULL;
 368         int sg_in_max_elements;
 369         int resync_sgs = 0;
 370         s32 sync_size = 0;
 371         u64 rcd_sn;
 372
 373         /* worst case is:
 374          * MAX_SKB_FRAGS in tls_record_info
 375          * MAX_SKB_FRAGS + 1 in SKB head and frags.
 376          */
 377         sg_in_max_elements = 2 * MAX_SKB_FRAGS + 1;
 378
 379         if (!payload_len)
 380                 return skb;
 381
 382         sg_in = kmalloc_array(sg_in_max_elements, sizeof(*sg_in), GFP_ATOMIC);
 383         if (!sg_in)
 384                 goto free_orig;
 385
 386         sg_init_table(sg_in, sg_in_max_elements);
 387         sg_init_table(sg_out, ARRAY_SIZE(sg_out));
 388
 389         if (fill_sg_in(sg_in, skb, ctx, &rcd_sn, &sync_size, &resync_sgs)) {
 390                 /* bypass packets before kernel TLS socket option was set */
 391                 if (sync_size < 0 && payload_len <= -sync_size)
 392                         nskb = skb_get(skb);
 393                 goto put_sg;
 394         }
 395
 396         nskb = tls_enc_skb(tls_ctx, sg_out, sg_in, skb, sync_size, rcd_sn);
 397
 398 put_sg:
 399         while (resync_sgs)
 400                 put_page(sg_page(&sg_in[--resync_sgs]));
 401         kfree(sg_in);
 402 free_orig:
 403         kfree_skb(skb);
 404         return nskb;
 405 }
 406
 407 struct sk_buff *tls_validate_xmit_skb(struct sock *sk,
 408                                       struct net_device *dev,
 409                                       struct sk_buff *skb)
 410 {
 411         if (dev == tls_get_ctx(sk)->netdev)
 412                 return skb;
 413
 414         return tls_sw_fallback(sk, skb);
 415 }
 416 EXPORT_SYMBOL_GPL(tls_validate_xmit_skb);
 417
 418 int tls_sw_fallback_init(struct sock *sk,
 419                          struct tls_offload_context_tx *offload_ctx,
 420                          struct tls_crypto_info *crypto_info)
 421 {
 422         const u8 *key;
 423         int rc;
 424
 425         offload_ctx->aead_send =
 426             crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
 427         if (IS_ERR(offload_ctx->aead_send)) {
 428                 rc = PTR_ERR(offload_ctx->aead_send);
 429                 pr_err_ratelimited("crypto_alloc_aead failed rc=%d\n", rc);
 430                 offload_ctx->aead_send = NULL;
 431                 goto err_out;
 432         }
 433
 434         key = ((struct tls12_crypto_info_aes_gcm_128 *)crypto_info)->key;
 435
 436         rc = crypto_aead_setkey(offload_ctx->aead_send, key,
 437                                 TLS_CIPHER_AES_GCM_128_KEY_SIZE);
 438         if (rc)
 439                 goto free_aead;
 440
 441         rc = crypto_aead_setauthsize(offload_ctx->aead_send,
 442                                      TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 443         if (rc)
 444                 goto free_aead;
 445
 446         return 0;
 447 free_aead:
 448         crypto_free_aead(offload_ctx->aead_send);
 449 err_out:
 450         return rc;
 451 }