ah_decrypt.c

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/*
 * ah_decrypt.c : IPSec AH decrypt 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>
#include <vnet/ipsec/ah.h>

#define foreach_ah_decrypt_next \
  _ (DROP, "error-drop")        \
  _ (IP4_INPUT, "ip4-input")    \
  _ (IP6_INPUT, "ip6-input")    \
  _ (IPSEC_GRE_INPUT, "ipsec-gre-input")

#define _(v, s) AH_DECRYPT_NEXT_##v,
typedef enum
{
  foreach_ah_decrypt_next
#undef _
    AH_DECRYPT_N_NEXT,
} ah_decrypt_next_t;

#define foreach_ah_decrypt_error                \
  _ (RX_PKTS, "AH pkts received")               \
  _ (DECRYPTION_FAILED, "AH decryption failed") \
  _ (INTEG_ERROR, "Integrity check failed")     \
  _ (REPLAY, "SA replayed packet")

typedef enum
{
#define _(sym,str) AH_DECRYPT_ERROR_##sym,
  foreach_ah_decrypt_error
#undef _
    AH_DECRYPT_N_ERROR,
} ah_decrypt_error_t;

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

typedef struct
{
  ipsec_integ_alg_t integ_alg;
  u32 seq_num;
} ah_decrypt_trace_t;

/* packet trace format function */
static u8 *
format_ah_decrypt_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 *);
  ah_decrypt_trace_t *t = va_arg (*args, ah_decrypt_trace_t *);

  s = format (s, "ah: integrity %U seq-num %d",
              format_ipsec_integ_alg, t->integ_alg, t->seq_num);
  return s;
}

always_inline uword
ah_decrypt_inline (vlib_main_t * vm,
                   vlib_node_runtime_t * node, vlib_frame_t * from_frame,
                   int is_ip6)
{
  u32 n_left_from, *from, next_index, *to_next;
  ipsec_main_t *im = &ipsec_main;
  ipsec_proto_main_t *em = &ipsec_proto_main;
  from = vlib_frame_vector_args (from_frame);
  n_left_from = from_frame->n_vectors;
  int icv_size = 0;

  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;
          u32 next0;
          vlib_buffer_t *i_b0;
          ah_header_t *ah0;
          ipsec_sa_t *sa0;
          u32 sa_index0 = ~0;
          u32 seq;
          ip4_header_t *ih4 = 0, *oh4 = 0;
          ip6_header_t *ih6 = 0, *oh6 = 0;
          u8 ip_hdr_size = 0;
          u8 tos = 0;
          u8 ttl = 0;
          u32 ip_version_traffic_class_and_flow_label = 0;
          u8 hop_limit = 0;
          u8 nexthdr = 0;
          u8 icv_padding_len = 0;


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

          next0 = AH_DECRYPT_NEXT_DROP;

          i_b0 = vlib_get_buffer (vm, i_bi0);
          to_next[0] = i_bi0;
          to_next += 1;
          ih4 = vlib_buffer_get_current (i_b0);
          ih6 = vlib_buffer_get_current (i_b0);
          sa_index0 = vnet_buffer (i_b0)->ipsec.sad_index;
          sa0 = pool_elt_at_index (im->sad, sa_index0);

          if (is_ip6)
            {
              ip6_ext_header_t *prev = NULL;
              ip6_ext_header_find_t (ih6, prev, ah0, IP_PROTOCOL_IPSEC_AH);
              ip_hdr_size = sizeof (ip6_header_t);
              ASSERT ((u8 *) ah0 - (u8 *) ih6 == ip_hdr_size);
            }
          else
            {
              ip_hdr_size = ip4_header_bytes (ih4);
              ah0 = (ah_header_t *) ((u8 *) ih4 + ip_hdr_size);
            }

          seq = clib_host_to_net_u32 (ah0->seq_no);

          /* anti-replay check */
          if (sa0->use_anti_replay)
            {
              int rv = 0;

              if (PREDICT_TRUE (sa0->use_esn))
                rv = esp_replay_check_esn (sa0, seq);
              else
                rv = esp_replay_check (sa0, seq);

              if (PREDICT_FALSE (rv))
                {
                  vlib_node_increment_counter (vm, node->node_index,
                                               AH_DECRYPT_ERROR_REPLAY, 1);
                  goto trace;
                }
            }


          sa0->total_data_size += i_b0->current_length;
          icv_size =
            em->ipsec_proto_main_integ_algs[sa0->integ_alg].trunc_size;
          if (PREDICT_TRUE (sa0->integ_alg != IPSEC_INTEG_ALG_NONE))
            {
              u8 sig[64];
              u8 digest[64];
              clib_memset (sig, 0, sizeof (sig));
              clib_memset (digest, 0, sizeof (digest));
              u8 *icv = ah0->auth_data;
              memcpy (digest, icv, icv_size);
              clib_memset (icv, 0, icv_size);

              if (is_ip6)
                {
                  ip_version_traffic_class_and_flow_label =
                    ih6->ip_version_traffic_class_and_flow_label;
                  hop_limit = ih6->hop_limit;
                  ih6->ip_version_traffic_class_and_flow_label = 0x60;
                  ih6->hop_limit = 0;
                  nexthdr = ah0->nexthdr;
                  icv_padding_len =
                    ah_calc_icv_padding_len (icv_size, 1 /* is_ipv6 */ );
                }
              else
                {
                  tos = ih4->tos;
                  ttl = ih4->ttl;
                  ih4->tos = 0;
                  ih4->ttl = 0;
                  ih4->checksum = 0;
                  ih4->flags_and_fragment_offset = 0;
                  icv_padding_len =
                    ah_calc_icv_padding_len (icv_size, 0 /* is_ipv6 */ );
                }
              hmac_calc (sa0->integ_alg, sa0->integ_key, sa0->integ_key_len,
                         (u8 *) ih4, i_b0->current_length, sig, sa0->use_esn,
                         sa0->seq_hi);

              if (PREDICT_FALSE (memcmp (digest, sig, icv_size)))
                {
                  vlib_node_increment_counter (vm, node->node_index,
                                               AH_DECRYPT_ERROR_INTEG_ERROR,
                                               1);
                  goto trace;
                }

              if (PREDICT_TRUE (sa0->use_anti_replay))
                {
                  if (PREDICT_TRUE (sa0->use_esn))
                    esp_replay_advance_esn (sa0, seq);
                  else
                    esp_replay_advance (sa0, seq);
                }

            }

          vlib_buffer_advance (i_b0,
                               ip_hdr_size + sizeof (ah_header_t) + icv_size +
                               icv_padding_len);
          i_b0->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;

          if (PREDICT_TRUE (sa0->is_tunnel))
            {                   /* tunnel mode */
              if (PREDICT_TRUE (ah0->nexthdr == IP_PROTOCOL_IP_IN_IP))
                next0 = AH_DECRYPT_NEXT_IP4_INPUT;
              else if (ah0->nexthdr == IP_PROTOCOL_IPV6)
                next0 = AH_DECRYPT_NEXT_IP6_INPUT;
              else
                {
                  vlib_node_increment_counter (vm, node->node_index,
                                               AH_DECRYPT_ERROR_DECRYPTION_FAILED,
                                               1);
                  goto trace;
                }
            }
          else
            {                   /* transport mode */
              if (is_ip6)
                {
                  vlib_buffer_advance (i_b0, -sizeof (ip6_header_t));
                  oh6 = vlib_buffer_get_current (i_b0);
                  memmove (oh6, ih6, sizeof (ip6_header_t));

                  next0 = AH_DECRYPT_NEXT_IP6_INPUT;
                  oh6->protocol = nexthdr;
                  oh6->hop_limit = hop_limit;
                  oh6->ip_version_traffic_class_and_flow_label =
                    ip_version_traffic_class_and_flow_label;
                  oh6->payload_length =
                    clib_host_to_net_u16 (vlib_buffer_length_in_chain
                                          (vm, i_b0) - sizeof (ip6_header_t));
                }
              else
                {
                  vlib_buffer_advance (i_b0, -sizeof (ip4_header_t));
                  oh4 = vlib_buffer_get_current (i_b0);
                  memmove (oh4, ih4, sizeof (ip4_header_t));

                  next0 = AH_DECRYPT_NEXT_IP4_INPUT;
                  oh4->ip_version_and_header_length = 0x45;
                  oh4->fragment_id = 0;
                  oh4->flags_and_fragment_offset = 0;
                  oh4->protocol = ah0->nexthdr;
                  oh4->length =
                    clib_host_to_net_u16 (vlib_buffer_length_in_chain
                                          (vm, i_b0));
                  oh4->ttl = ttl;
                  oh4->tos = tos;
                  oh4->checksum = ip4_header_checksum (oh4);
                }
            }

          /* for IPSec-GRE tunnel next node is ipsec-gre-input */
          if (PREDICT_FALSE
              ((vnet_buffer (i_b0)->ipsec.flags) &
               IPSEC_FLAG_IPSEC_GRE_TUNNEL))
            next0 = AH_DECRYPT_NEXT_IPSEC_GRE_INPUT;


          vnet_buffer (i_b0)->sw_if_index[VLIB_TX] = (u32) ~ 0;
        trace:
          if (PREDICT_FALSE (i_b0->flags & VLIB_BUFFER_IS_TRACED))
            {
              i_b0->flags |= VLIB_BUFFER_IS_TRACED;
              ah_decrypt_trace_t *tr =
                vlib_add_trace (vm, node, i_b0, sizeof (*tr));
              tr->integ_alg = sa0->integ_alg;
              tr->seq_num = seq;
            }
          vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
                                           n_left_to_next, i_bi0, next0);
        }
      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
    }
  vlib_node_increment_counter (vm, node->node_index, AH_DECRYPT_ERROR_RX_PKTS,
                               from_frame->n_vectors);

  return from_frame->n_vectors;
}

VLIB_NODE_FN (ah4_decrypt_node) (vlib_main_t * vm,
                                 vlib_node_runtime_t * node,
                                 vlib_frame_t * from_frame)
{
  return ah_decrypt_inline (vm, node, from_frame, 0 /* is_ip6 */ );
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (ah4_decrypt_node) = {
  .name = "ah4-decrypt",
  .vector_size = sizeof (u32),
  .format_trace = format_ah_decrypt_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,

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

  .n_next_nodes = AH_DECRYPT_N_NEXT,
  .next_nodes = {
#define _(s,n) [AH_DECRYPT_NEXT_##s] = n,
    foreach_ah_decrypt_next
#undef _
  },
};
/* *INDENT-ON* */

VLIB_NODE_FN (ah6_decrypt_node) (vlib_main_t * vm,
                                 vlib_node_runtime_t * node,
                                 vlib_frame_t * from_frame)
{
  return ah_decrypt_inline (vm, node, from_frame, 1 /* is_ip6 */ );
}

/* *INDENT-OFF* */
VLIB_REGISTER_NODE (ah6_decrypt_node) = {
  .name = "ah6-decrypt",
  .vector_size = sizeof (u32),
  .format_trace = format_ah_decrypt_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,

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

  .n_next_nodes = AH_DECRYPT_N_NEXT,
  .next_nodes = {
#define _(s,n) [AH_DECRYPT_NEXT_##s] = n,
    foreach_ah_decrypt_next
#undef _
  },
};
/* *INDENT-ON* */

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */