linux/net/tls/tls_device_fallback.c
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   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
  37static 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
  48static 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                TLS_1_2_VERSION);
  78
  79        memcpy(iv + TLS_CIPHER_AES_GCM_128_SALT_SIZE, buf + TLS_HEADER_SIZE,
  80               TLS_CIPHER_AES_GCM_128_IV_SIZE);
  81
  82        sg_init_table(sg_in, ARRAY_SIZE(sg_in));
  83        sg_init_table(sg_out, ARRAY_SIZE(sg_out));
  84        sg_set_buf(sg_in, aad, TLS_AAD_SPACE_SIZE);
  85        sg_set_buf(sg_out, aad, TLS_AAD_SPACE_SIZE);
  86        chain_to_walk(sg_in + 1, in);
  87        chain_to_walk(sg_out + 1, out);
  88
  89        *in_len -= len;
  90        if (*in_len < 0) {
  91                *in_len += TLS_CIPHER_AES_GCM_128_TAG_SIZE;
  92                /* the input buffer doesn't contain the entire record.
  93                 * trim len accordingly. The resulting authentication tag
  94                 * will contain garbage, but we don't care, so we won't
  95                 * include any of it in the output skb
  96                 * Note that we assume the output buffer length
  97                 * is larger then input buffer length + tag size
  98                 */
  99                if (*in_len < 0)
 100                        len += *in_len;
 101
 102                *in_len = 0;
 103        }
 104
 105        if (*in_len) {
 106                scatterwalk_copychunks(NULL, in, len, 2);
 107                scatterwalk_pagedone(in, 0, 1);
 108                scatterwalk_copychunks(NULL, out, len, 2);
 109                scatterwalk_pagedone(out, 1, 1);
 110        }
 111
 112        len -= TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 113        aead_request_set_crypt(aead_req, sg_in, sg_out, len, iv);
 114
 115        rc = crypto_aead_encrypt(aead_req);
 116
 117        return rc;
 118}
 119
 120static void tls_init_aead_request(struct aead_request *aead_req,
 121                                  struct crypto_aead *aead)
 122{
 123        aead_request_set_tfm(aead_req, aead);
 124        aead_request_set_ad(aead_req, TLS_AAD_SPACE_SIZE);
 125}
 126
 127static struct aead_request *tls_alloc_aead_request(struct crypto_aead *aead,
 128                                                   gfp_t flags)
 129{
 130        unsigned int req_size = sizeof(struct aead_request) +
 131                crypto_aead_reqsize(aead);
 132        struct aead_request *aead_req;
 133
 134        aead_req = kzalloc(req_size, flags);
 135        if (aead_req)
 136                tls_init_aead_request(aead_req, aead);
 137        return aead_req;
 138}
 139
 140static int tls_enc_records(struct aead_request *aead_req,
 141                           struct crypto_aead *aead, struct scatterlist *sg_in,
 142                           struct scatterlist *sg_out, char *aad, char *iv,
 143                           u64 rcd_sn, int len)
 144{
 145        struct scatter_walk out, in;
 146        int rc;
 147
 148        scatterwalk_start(&in, sg_in);
 149        scatterwalk_start(&out, sg_out);
 150
 151        do {
 152                rc = tls_enc_record(aead_req, aead, aad, iv,
 153                                    cpu_to_be64(rcd_sn), &in, &out, &len);
 154                rcd_sn++;
 155
 156        } while (rc == 0 && len);
 157
 158        scatterwalk_done(&in, 0, 0);
 159        scatterwalk_done(&out, 1, 0);
 160
 161        return rc;
 162}
 163
 164/* Can't use icsk->icsk_af_ops->send_check here because the ip addresses
 165 * might have been changed by NAT.
 166 */
 167static void update_chksum(struct sk_buff *skb, int headln)
 168{
 169        struct tcphdr *th = tcp_hdr(skb);
 170        int datalen = skb->len - headln;
 171        const struct ipv6hdr *ipv6h;
 172        const struct iphdr *iph;
 173
 174        /* We only changed the payload so if we are using partial we don't
 175         * need to update anything.
 176         */
 177        if (likely(skb->ip_summed == CHECKSUM_PARTIAL))
 178                return;
 179
 180        skb->ip_summed = CHECKSUM_PARTIAL;
 181        skb->csum_start = skb_transport_header(skb) - skb->head;
 182        skb->csum_offset = offsetof(struct tcphdr, check);
 183
 184        if (skb->sk->sk_family == AF_INET6) {
 185                ipv6h = ipv6_hdr(skb);
 186                th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
 187                                             datalen, IPPROTO_TCP, 0);
 188        } else {
 189                iph = ip_hdr(skb);
 190                th->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, datalen,
 191                                               IPPROTO_TCP, 0);
 192        }
 193}
 194
 195static void complete_skb(struct sk_buff *nskb, struct sk_buff *skb, int headln)
 196{
 197        struct sock *sk = skb->sk;
 198        int delta;
 199
 200        skb_copy_header(nskb, skb);
 201
 202        skb_put(nskb, skb->len);
 203        memcpy(nskb->data, skb->data, headln);
 204
 205        nskb->destructor = skb->destructor;
 206        nskb->sk = sk;
 207        skb->destructor = NULL;
 208        skb->sk = NULL;
 209
 210        update_chksum(nskb, headln);
 211
 212        /* sock_efree means skb must gone through skb_orphan_partial() */
 213        if (nskb->destructor == sock_efree)
 214                return;
 215
 216        delta = nskb->truesize - skb->truesize;
 217        if (likely(delta < 0))
 218                WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
 219        else if (delta)
 220                refcount_add(delta, &sk->sk_wmem_alloc);
 221}
 222
 223/* This function may be called after the user socket is already
 224 * closed so make sure we don't use anything freed during
 225 * tls_sk_proto_close here
 226 */
 227
 228static int fill_sg_in(struct scatterlist *sg_in,
 229                      struct sk_buff *skb,
 230                      struct tls_offload_context_tx *ctx,
 231                      u64 *rcd_sn,
 232                      s32 *sync_size,
 233                      int *resync_sgs)
 234{
 235        int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 236        int payload_len = skb->len - tcp_payload_offset;
 237        u32 tcp_seq = ntohl(tcp_hdr(skb)->seq);
 238        struct tls_record_info *record;
 239        unsigned long flags;
 240        int remaining;
 241        int i;
 242
 243        spin_lock_irqsave(&ctx->lock, flags);
 244        record = tls_get_record(ctx, tcp_seq, rcd_sn);
 245        if (!record) {
 246                spin_unlock_irqrestore(&ctx->lock, flags);
 247                return -EINVAL;
 248        }
 249
 250        *sync_size = tcp_seq - tls_record_start_seq(record);
 251        if (*sync_size < 0) {
 252                int is_start_marker = tls_record_is_start_marker(record);
 253
 254                spin_unlock_irqrestore(&ctx->lock, flags);
 255                /* This should only occur if the relevant record was
 256                 * already acked. In that case it should be ok
 257                 * to drop the packet and avoid retransmission.
 258                 *
 259                 * There is a corner case where the packet contains
 260                 * both an acked and a non-acked record.
 261                 * We currently don't handle that case and rely
 262                 * on TCP to retranmit a packet that doesn't contain
 263                 * already acked payload.
 264                 */
 265                if (!is_start_marker)
 266                        *sync_size = 0;
 267                return -EINVAL;
 268        }
 269
 270        remaining = *sync_size;
 271        for (i = 0; remaining > 0; i++) {
 272                skb_frag_t *frag = &record->frags[i];
 273
 274                __skb_frag_ref(frag);
 275                sg_set_page(sg_in + i, skb_frag_page(frag),
 276                            skb_frag_size(frag), skb_frag_off(frag));
 277
 278                remaining -= skb_frag_size(frag);
 279
 280                if (remaining < 0)
 281                        sg_in[i].length += remaining;
 282        }
 283        *resync_sgs = i;
 284
 285        spin_unlock_irqrestore(&ctx->lock, flags);
 286        if (skb_to_sgvec(skb, &sg_in[i], tcp_payload_offset, payload_len) < 0)
 287                return -EINVAL;
 288
 289        return 0;
 290}
 291
 292static void fill_sg_out(struct scatterlist sg_out[3], void *buf,
 293                        struct tls_context *tls_ctx,
 294                        struct sk_buff *nskb,
 295                        int tcp_payload_offset,
 296                        int payload_len,
 297                        int sync_size,
 298                        void *dummy_buf)
 299{
 300        sg_set_buf(&sg_out[0], dummy_buf, sync_size);
 301        sg_set_buf(&sg_out[1], nskb->data + tcp_payload_offset, payload_len);
 302        /* Add room for authentication tag produced by crypto */
 303        dummy_buf += sync_size;
 304        sg_set_buf(&sg_out[2], dummy_buf, TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 305}
 306
 307static struct sk_buff *tls_enc_skb(struct tls_context *tls_ctx,
 308                                   struct scatterlist sg_out[3],
 309                                   struct scatterlist *sg_in,
 310                                   struct sk_buff *skb,
 311                                   s32 sync_size, u64 rcd_sn)
 312{
 313        int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 314        struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 315        int payload_len = skb->len - tcp_payload_offset;
 316        void *buf, *iv, *aad, *dummy_buf;
 317        struct aead_request *aead_req;
 318        struct sk_buff *nskb = NULL;
 319        int buf_len;
 320
 321        aead_req = tls_alloc_aead_request(ctx->aead_send, GFP_ATOMIC);
 322        if (!aead_req)
 323                return NULL;
 324
 325        buf_len = TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 326                  TLS_CIPHER_AES_GCM_128_IV_SIZE +
 327                  TLS_AAD_SPACE_SIZE +
 328                  sync_size +
 329                  TLS_CIPHER_AES_GCM_128_TAG_SIZE;
 330        buf = kmalloc(buf_len, GFP_ATOMIC);
 331        if (!buf)
 332                goto free_req;
 333
 334        iv = buf;
 335        memcpy(iv, tls_ctx->crypto_send.aes_gcm_128.salt,
 336               TLS_CIPHER_AES_GCM_128_SALT_SIZE);
 337        aad = buf + TLS_CIPHER_AES_GCM_128_SALT_SIZE +
 338              TLS_CIPHER_AES_GCM_128_IV_SIZE;
 339        dummy_buf = aad + TLS_AAD_SPACE_SIZE;
 340
 341        nskb = alloc_skb(skb_headroom(skb) + skb->len, GFP_ATOMIC);
 342        if (!nskb)
 343                goto free_buf;
 344
 345        skb_reserve(nskb, skb_headroom(skb));
 346
 347        fill_sg_out(sg_out, buf, tls_ctx, nskb, tcp_payload_offset,
 348                    payload_len, sync_size, dummy_buf);
 349
 350        if (tls_enc_records(aead_req, ctx->aead_send, sg_in, sg_out, aad, iv,
 351                            rcd_sn, sync_size + payload_len) < 0)
 352                goto free_nskb;
 353
 354        complete_skb(nskb, skb, tcp_payload_offset);
 355
 356        /* validate_xmit_skb_list assumes that if the skb wasn't segmented
 357         * nskb->prev will point to the skb itself
 358         */
 359        nskb->prev = nskb;
 360
 361free_buf:
 362        kfree(buf);
 363free_req:
 364        kfree(aead_req);
 365        return nskb;
 366free_nskb:
 367        kfree_skb(nskb);
 368        nskb = NULL;
 369        goto free_buf;
 370}
 371
 372static struct sk_buff *tls_sw_fallback(struct sock *sk, struct sk_buff *skb)
 373{
 374        int tcp_payload_offset = skb_transport_offset(skb) + tcp_hdrlen(skb);
 375        struct tls_context *tls_ctx = tls_get_ctx(sk);
 376        struct tls_offload_context_tx *ctx = tls_offload_ctx_tx(tls_ctx);
 377        int payload_len = skb->len - tcp_payload_offset;
 378        struct scatterlist *sg_in, sg_out[3];
 379        struct sk_buff *nskb = NULL;
 380        int sg_in_max_elements;
 381        int resync_sgs = 0;
 382        s32 sync_size = 0;
 383        u64 rcd_sn;
 384
 385        /* worst case is:
 386         * MAX_SKB_FRAGS in tls_record_info
 387         * MAX_SKB_FRAGS + 1 in SKB head and frags.
 388         */
 389        sg_in_max_elements = 2 * MAX_SKB_FRAGS + 1;
 390
 391        if (!payload_len)
 392                return skb;
 393
 394        sg_in = kmalloc_array(sg_in_max_elements, sizeof(*sg_in), GFP_ATOMIC);
 395        if (!sg_in)
 396                goto free_orig;
 397
 398        sg_init_table(sg_in, sg_in_max_elements);
 399        sg_init_table(sg_out, ARRAY_SIZE(sg_out));
 400
 401        if (fill_sg_in(sg_in, skb, ctx, &rcd_sn, &sync_size, &resync_sgs)) {
 402                /* bypass packets before kernel TLS socket option was set */
 403                if (sync_size < 0 && payload_len <= -sync_size)
 404                        nskb = skb_get(skb);
 405                goto put_sg;
 406        }
 407
 408        nskb = tls_enc_skb(tls_ctx, sg_out, sg_in, skb, sync_size, rcd_sn);
 409
 410put_sg:
 411        while (resync_sgs)
 412                put_page(sg_page(&sg_in[--resync_sgs]));
 413        kfree(sg_in);
 414free_orig:
 415        if (nskb)
 416                consume_skb(skb);
 417        else
 418                kfree_skb(skb);
 419        return nskb;
 420}
 421
 422struct sk_buff *tls_validate_xmit_skb(struct sock *sk,
 423                                      struct net_device *dev,
 424                                      struct sk_buff *skb)
 425{
 426        if (dev == tls_get_ctx(sk)->netdev)
 427                return skb;
 428
 429        return tls_sw_fallback(sk, skb);
 430}
 431EXPORT_SYMBOL_GPL(tls_validate_xmit_skb);
 432
 433struct sk_buff *tls_encrypt_skb(struct sk_buff *skb)
 434{
 435        return tls_sw_fallback(skb->sk, skb);
 436}
 437EXPORT_SYMBOL_GPL(tls_encrypt_skb);
 438
 439int tls_sw_fallback_init(struct sock *sk,
 440                         struct tls_offload_context_tx *offload_ctx,
 441                         struct tls_crypto_info *crypto_info)
 442{
 443        const u8 *key;
 444        int rc;
 445
 446        offload_ctx->aead_send =
 447            crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
 448        if (IS_ERR(offload_ctx->aead_send)) {
 449                rc = PTR_ERR(offload_ctx->aead_send);
 450                pr_err_ratelimited("crypto_alloc_aead failed rc=%d\n", rc);
 451                offload_ctx->aead_send = NULL;
 452                goto err_out;
 453        }
 454
 455        key = ((struct tls12_crypto_info_aes_gcm_128 *)crypto_info)->key;
 456
 457        rc = crypto_aead_setkey(offload_ctx->aead_send, key,
 458                                TLS_CIPHER_AES_GCM_128_KEY_SIZE);
 459        if (rc)
 460                goto free_aead;
 461
 462        rc = crypto_aead_setauthsize(offload_ctx->aead_send,
 463                                     TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 464        if (rc)
 465                goto free_aead;
 466
 467        return 0;
 468free_aead:
 469        crypto_free_aead(offload_ctx->aead_send);
 470err_out:
 471        return rc;
 472}
 473