esp_encrypt.c

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/*
 * esp_encrypt.c : IPSec ESP encrypt node
 *
 * Copyright (c) 2015 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <vnet/vnet.h>
#include <vnet/api_errno.h>
#include <vnet/ip/ip.h>

#include <vnet/ipsec/ipsec.h>
#include <vnet/ipsec/esp.h>

#define ESP_SEQ_MAX (4294967295UL)

#define foreach_esp_encrypt_next                   \
_(DROP, "error-drop")                              \
_(IP4_INPUT, "ip4-input")                          \
_(IP6_INPUT, "ip6-input")                          \
_(INTERFACE_OUTPUT, "interface-output")

#define _(v, s) ESP_ENCRYPT_NEXT_##v,
typedef enum {
  foreach_esp_encrypt_next
#undef _
  ESP_ENCRYPT_N_NEXT,
} esp_encrypt_next_t;

#define foreach_esp_encrypt_error                   \
 _(RX_PKTS, "ESP pkts received")                    \
 _(NO_BUFFER, "No buffer (packet dropped)")         \
 _(DECRYPTION_FAILED, "ESP encryption failed")      \
 _(SEQ_CYCLED, "sequence number cycled")


typedef enum {
#define _(sym,str) ESP_ENCRYPT_ERROR_##sym,
  foreach_esp_encrypt_error
#undef _
  ESP_ENCRYPT_N_ERROR,
} esp_encrypt_error_t;

static char * esp_encrypt_error_strings[] = {
#define _(sym,string) string,
  foreach_esp_encrypt_error
#undef _
};

vlib_node_registration_t esp_encrypt_node;

typedef struct {
  u32 spi;
  u32 seq;
  ipsec_crypto_alg_t crypto_alg;
  ipsec_integ_alg_t integ_alg;
} esp_encrypt_trace_t;

/* packet trace format function */
static u8 * format_esp_encrypt_trace (u8 * s, va_list * args)
{
  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
  esp_encrypt_trace_t * t = va_arg (*args, esp_encrypt_trace_t *);

  s = format (s, "esp: spi %u seq %u crypto %U integrity %U",
              t->spi, t->seq,
              format_ipsec_crypto_alg, t->crypto_alg,
              format_ipsec_integ_alg, t->integ_alg);
  return s;
}

always_inline void
esp_encrypt_aes_cbc(ipsec_crypto_alg_t alg,
                    u8 * in,
                    u8 * out,
                    size_t in_len,
                    u8 * key,
                    u8 * iv)
{
  esp_main_t * em = &esp_main;
  u32 cpu_index = os_get_cpu_number();
  EVP_CIPHER_CTX * ctx = &(em->per_thread_data[cpu_index].encrypt_ctx);
  const EVP_CIPHER * cipher = NULL;
  int out_len;

  ASSERT(alg < IPSEC_CRYPTO_N_ALG);

  if (PREDICT_FALSE(em->esp_crypto_algs[alg].type == IPSEC_CRYPTO_ALG_NONE))
    return;

  if (PREDICT_FALSE(alg != em->per_thread_data[cpu_index].last_encrypt_alg)) {
    cipher = em->esp_crypto_algs[alg].type;
    em->per_thread_data[cpu_index].last_encrypt_alg = alg;
  }

  EVP_EncryptInit_ex(ctx, cipher, NULL, key, iv);

  EVP_EncryptUpdate(ctx, out, &out_len, in, in_len);
  EVP_EncryptFinal_ex(ctx, out + out_len, &out_len);
}

always_inline int
esp_seq_advance (ipsec_sa_t * sa)
{
  if (PREDICT_TRUE(sa->use_esn))
    {
      if (PREDICT_FALSE(sa->seq == ESP_SEQ_MAX))
        {
          if (PREDICT_FALSE(sa->use_anti_replay && sa->seq_hi == ESP_SEQ_MAX))
            return 1;
          sa->seq_hi++;
        }
      sa->seq++;
    }
  else
    {
      if (PREDICT_FALSE(sa->use_anti_replay && sa->seq == ESP_SEQ_MAX))
        return 1;
      sa->seq++;
    }

  return 0;
}

static uword
esp_encrypt_node_fn (vlib_main_t * vm,
                     vlib_node_runtime_t * node,
                     vlib_frame_t * from_frame)
{
  u32 n_left_from, *from, * to_next = 0, next_index;
  from = vlib_frame_vector_args (from_frame);
  n_left_from = from_frame->n_vectors;
  ipsec_main_t *im = &ipsec_main;
  u32 * recycle = 0;
  u32 cpu_index = os_get_cpu_number();
  u32 * empty_buffers = im->empty_buffers[cpu_index];

  ipsec_alloc_empty_buffers(vm, im);

  if (PREDICT_FALSE(vec_len (empty_buffers) < n_left_from)){
    vlib_node_increment_counter (vm, esp_encrypt_node.index,
                                 ESP_ENCRYPT_ERROR_NO_BUFFER, n_left_from);
    clib_warning("no enough empty buffers. discarding frame");
    goto free_buffers_and_exit;
  }

  next_index = node->cached_next_index;

  while (n_left_from > 0)
    {
      u32 n_left_to_next;

      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);

      while (n_left_from > 0 && n_left_to_next > 0)
        {
          u32 i_bi0, o_bi0, next0;
          vlib_buffer_t * i_b0, *o_b0 = 0;
          u32 sa_index0;
          ipsec_sa_t * sa0;
          ip4_and_esp_header_t * ih0, * oh0 = 0;
          ip6_and_esp_header_t * ih6_0, * oh6_0 = 0;
          uword last_empty_buffer;
          esp_header_t * o_esp0;
          esp_footer_t *f0;
          u8 is_ipv6;
          u8 ip_hdr_size;
          u8 next_hdr_type;

          i_bi0 = from[0];
          from += 1;
          n_left_from -= 1;
          n_left_to_next -= 1;

          next0 = ESP_ENCRYPT_NEXT_DROP;

          i_b0 = vlib_get_buffer (vm, i_bi0);
          sa_index0 = vnet_buffer(i_b0)->output_features.ipsec_sad_index;
          sa0 = pool_elt_at_index(im->sad, sa_index0);

          if (PREDICT_FALSE(esp_seq_advance(sa0)))
            {
              clib_warning("sequence number counter has cycled SPI %u", sa0->spi);
              vlib_node_increment_counter (vm, esp_encrypt_node.index,
                                           ESP_ENCRYPT_ERROR_SEQ_CYCLED, 1);
              //TODO: rekey SA
              o_bi0 = i_bi0;
              goto trace;
            }

          /* grab free buffer */
          last_empty_buffer = vec_len (empty_buffers) - 1;
          o_bi0 = empty_buffers[last_empty_buffer];
          o_b0 = vlib_get_buffer (vm, o_bi0);
          o_b0->current_data = sizeof(ethernet_header_t);
          ih0 = vlib_buffer_get_current (i_b0);
          vlib_prefetch_buffer_with_index (vm, empty_buffers[last_empty_buffer-1], STORE);
          _vec_len (empty_buffers) = last_empty_buffer;
          to_next[0] = o_bi0;
          to_next += 1;

          /* add old buffer to the recycle list */
          vec_add1(recycle, i_bi0);

          /* is ipv6 */
          if (PREDICT_FALSE((ih0->ip4.ip_version_and_header_length & 0xF0 ) == 0x60))
            {
              is_ipv6 = 1;
              ih6_0 = vlib_buffer_get_current (i_b0);
              ip_hdr_size = sizeof(ip6_header_t);
              next_hdr_type = IP_PROTOCOL_IPV6;
              oh6_0 = vlib_buffer_get_current (o_b0);
              o_esp0 = vlib_buffer_get_current (o_b0) + sizeof(ip6_header_t);

              oh6_0->ip6.ip_version_traffic_class_and_flow_label =
                  ih6_0->ip6.ip_version_traffic_class_and_flow_label;
              oh6_0->ip6.protocol = IP_PROTOCOL_IPSEC_ESP;
              oh6_0->ip6.hop_limit = 254;
              oh6_0->esp.spi = clib_net_to_host_u32(sa0->spi);
              oh6_0->esp.seq = clib_net_to_host_u32(sa0->seq);
            }
          else
            {
              is_ipv6 = 0;
              ip_hdr_size = sizeof(ip4_header_t);
              next_hdr_type = IP_PROTOCOL_IP_IN_IP;
              oh0 = vlib_buffer_get_current (o_b0);
              o_esp0 = vlib_buffer_get_current (o_b0) + sizeof(ip4_header_t);

              oh0->ip4.ip_version_and_header_length = 0x45;
              oh0->ip4.tos = ih0->ip4.tos;
              oh0->ip4.fragment_id = 0;
              oh0->ip4.flags_and_fragment_offset = 0;
              oh0->ip4.ttl = 254;
              oh0->ip4.protocol = IP_PROTOCOL_IPSEC_ESP;
              oh0->esp.spi = clib_net_to_host_u32(sa0->spi);
              oh0->esp.seq = clib_net_to_host_u32(sa0->seq);
            }

          if (PREDICT_TRUE(sa0->is_tunnel && !sa0->is_tunnel_ip6))
            {
              oh0->ip4.src_address.as_u32 = sa0->tunnel_src_addr.ip4.as_u32;
              oh0->ip4.dst_address.as_u32 = sa0->tunnel_dst_addr.ip4.as_u32;

              /* in tunnel mode send it back to FIB */
              next0 = ESP_ENCRYPT_NEXT_IP4_INPUT;
              vnet_buffer (o_b0)->sw_if_index[VLIB_TX] = (u32)~0;
            }
          else if(sa0->is_tunnel && sa0->is_tunnel_ip6)
            {
              oh6_0->ip6.src_address.as_u64[0] = sa0->tunnel_src_addr.ip6.as_u64[0];
              oh6_0->ip6.src_address.as_u64[1] = sa0->tunnel_src_addr.ip6.as_u64[1];
              oh6_0->ip6.dst_address.as_u64[0] = sa0->tunnel_dst_addr.ip6.as_u64[0];
              oh6_0->ip6.dst_address.as_u64[1] = sa0->tunnel_dst_addr.ip6.as_u64[1];

              /* in tunnel mode send it back to FIB */
              next0 = ESP_ENCRYPT_NEXT_IP6_INPUT;
              vnet_buffer (o_b0)->sw_if_index[VLIB_TX] = (u32)~0;
            }
          else
            {
              next0 = ESP_ENCRYPT_NEXT_INTERFACE_OUTPUT;
              vnet_buffer (o_b0)->sw_if_index[VLIB_TX] =
                vnet_buffer (i_b0)->sw_if_index[VLIB_TX];
            }

          ASSERT(sa0->crypto_alg < IPSEC_CRYPTO_N_ALG);

          if (PREDICT_TRUE(sa0->crypto_alg != IPSEC_CRYPTO_ALG_NONE)) {

            const int BLOCK_SIZE = 16;
            const int IV_SIZE = 16;
            int blocks = 1 + (i_b0->current_length + 1) / BLOCK_SIZE;

            /* pad packet in input buffer */
            u8 pad_bytes = BLOCK_SIZE * blocks - 2 - i_b0->current_length;
            u8 i;
            u8 * padding = vlib_buffer_get_current (i_b0) + i_b0->current_length;
            i_b0->current_length = BLOCK_SIZE * blocks;
            for (i = 0; i < pad_bytes; ++i)
              {
                padding[i] = i + 1;
              }
            f0 = vlib_buffer_get_current (i_b0) + i_b0->current_length - 2;
            f0->pad_length = pad_bytes;
            f0->next_header = next_hdr_type;

            o_b0->current_length = ip_hdr_size + sizeof(esp_header_t) +
                  BLOCK_SIZE * blocks + IV_SIZE;

            vnet_buffer (o_b0)->sw_if_index[VLIB_RX] =
              vnet_buffer (i_b0)->sw_if_index[VLIB_RX];
            o_b0->flags = VLIB_BUFFER_TOTAL_LENGTH_VALID;

            u8 iv[16];
            RAND_bytes(iv, sizeof(iv));

            clib_memcpy((u8 *) vlib_buffer_get_current (o_b0) + ip_hdr_size +
                   sizeof(esp_header_t), iv, 16 );

            esp_encrypt_aes_cbc(sa0->crypto_alg,
                                (u8 *) vlib_buffer_get_current (i_b0),
                                (u8 *) vlib_buffer_get_current (o_b0) +
                                  ip_hdr_size + sizeof(esp_header_t) + IV_SIZE,
                                BLOCK_SIZE * blocks,
                                sa0->crypto_key,
                                iv);
          }

          o_b0->current_length += hmac_calc(sa0->integ_alg, sa0->integ_key,
                                            sa0->integ_key_len,
                                            (u8 *) o_esp0,
                                            o_b0->current_length - ip_hdr_size,
                                            vlib_buffer_get_current (o_b0) +
                                            o_b0->current_length,
                                            sa0->use_esn,
                                            sa0->seq_hi);


          if (PREDICT_FALSE(is_ipv6))
            {
              oh6_0->ip6.payload_length = clib_host_to_net_u16 (
                  vlib_buffer_length_in_chain (vm, o_b0) - sizeof(ip6_header_t));
            }
          else
            {
              oh0->ip4.length = clib_host_to_net_u16 (
                  vlib_buffer_length_in_chain (vm, o_b0));
              oh0->ip4.checksum = ip4_header_checksum (&oh0->ip4);
            }

trace:
          if (PREDICT_FALSE(i_b0->flags & VLIB_BUFFER_IS_TRACED)) {
            if (o_b0) {
              o_b0->flags |= VLIB_BUFFER_IS_TRACED;
              o_b0->trace_index = i_b0->trace_index;
            }
            esp_encrypt_trace_t *tr = vlib_add_trace (vm, node, o_b0, sizeof (*tr));
            tr->spi = sa0->spi;
            tr->seq = sa0->seq - 1;
            tr->crypto_alg = sa0->crypto_alg;
            tr->integ_alg = sa0->integ_alg;
          }

          vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
              to_next, n_left_to_next, o_bi0, next0);
        }
      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }
  vlib_node_increment_counter (vm, esp_encrypt_node.index,
                               ESP_ENCRYPT_ERROR_RX_PKTS,
                               from_frame->n_vectors);

free_buffers_and_exit:
  vlib_buffer_free (vm, recycle, vec_len(recycle));
  vec_free(recycle);
  return from_frame->n_vectors;
}


VLIB_REGISTER_NODE (esp_encrypt_node) = {
  .function = esp_encrypt_node_fn,
  .name = "esp-encrypt",
  .vector_size = sizeof (u32),
  .format_trace = format_esp_encrypt_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,

  .n_errors = ARRAY_LEN(esp_encrypt_error_strings),
  .error_strings = esp_encrypt_error_strings,

  .n_next_nodes = ESP_ENCRYPT_N_NEXT,
  .next_nodes = {
#define _(s,n) [ESP_ENCRYPT_NEXT_##s] = n,
    foreach_esp_encrypt_next
#undef _
  },
};