/src/freeradius-server/src/protocols/tacacs/decode.c

Source
/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

/**
 * $Id: 15406fd819d491e2576a2cfe8ec4c21846cf336d $
 *
 * @file protocols/tacacs/decode.c
 * @brief Low-Level TACACS+ decoding functions
 *
 * @copyright 2017 The FreeRADIUS server project
 * @copyright 2017 Network RADIUS SAS (legal@networkradius.com)
 */

#include <freeradius-devel/io/test_point.h>
#include <freeradius-devel/protocol/tacacs/tacacs.h>
#include <freeradius-devel/util/debug.h>
#include <freeradius-devel/util/net.h>
#include <freeradius-devel/util/struct.h>

#include "tacacs.h"
#include "attrs.h"

int fr_tacacs_packet_to_code(fr_tacacs_packet_t const *pkt)
{
  switch (pkt->hdr.type) {
  case FR_TAC_PLUS_AUTHEN:
    if (pkt->hdr.seq_no == 1) return FR_PACKET_TYPE_VALUE_AUTHENTICATION_START;

    if ((pkt->hdr.seq_no & 0x01) == 1) {
      if (pkt->authen_cont.flags == FR_TAC_PLUS_CONTINUE_FLAG_UNSET) return FR_PACKET_TYPE_VALUE_AUTHENTICATION_CONTINUE;

      if (pkt->authen_cont.flags == FR_TAC_PLUS_CONTINUE_FLAG_ABORT) return FR_PACKET_TYPE_VALUE_AUTHENTICATION_CONTINUE_ABORT;

      fr_strerror_printf("Invalid value %d for authentication continue flag", pkt->authen_cont.flags);
      return -1;
    }

    switch (pkt->authen_reply.status) {
    case FR_TAC_PLUS_AUTHEN_STATUS_PASS:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_PASS;

    case FR_TAC_PLUS_AUTHEN_STATUS_FAIL:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_FAIL;

    case FR_TAC_PLUS_AUTHEN_STATUS_GETDATA:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_GETDATA;

    case FR_TAC_PLUS_AUTHEN_STATUS_GETUSER:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_GETUSER;

    case FR_TAC_PLUS_AUTHEN_STATUS_GETPASS:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_GETPASS;

    case FR_TAC_PLUS_AUTHEN_STATUS_RESTART:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_RESTART;

    case FR_TAC_PLUS_AUTHEN_STATUS_ERROR:
      return FR_PACKET_TYPE_VALUE_AUTHENTICATION_ERROR;

    default:
      break;
    }

    fr_strerror_printf("Invalid value %d for authentication reply status", pkt->authen_reply.status);
    return -1;

  case FR_TAC_PLUS_AUTHOR:
    if ((pkt->hdr.seq_no & 0x01) == 1) {
      return FR_PACKET_TYPE_VALUE_AUTHORIZATION_REQUEST;
    }

    switch (pkt->author_reply.status) {
    case FR_TAC_PLUS_AUTHOR_STATUS_PASS_ADD:
      return FR_PACKET_TYPE_VALUE_AUTHORIZATION_PASS_ADD;

    case FR_TAC_PLUS_AUTHOR_STATUS_PASS_REPL:
      return FR_PACKET_TYPE_VALUE_AUTHORIZATION_PASS_REPLACE;

    case FR_TAC_PLUS_AUTHOR_STATUS_FAIL:
      return FR_PACKET_TYPE_VALUE_AUTHORIZATION_FAIL;

    default:
      break;
    }

    fr_strerror_printf("Invalid value %d for authorization reply status", pkt->author_reply.status);
    return -1;

  case FR_TAC_PLUS_ACCT:
    if ((pkt->hdr.seq_no & 0x01) == 1) {
      return FR_PACKET_TYPE_VALUE_ACCOUNTING_REQUEST;
    }

    switch (pkt->acct_reply.status) {
    case FR_TAC_PLUS_ACCT_STATUS_SUCCESS:
      return FR_PACKET_TYPE_VALUE_ACCOUNTING_SUCCESS;

    case FR_TAC_PLUS_ACCT_STATUS_ERROR:
      return FR_PACKET_TYPE_VALUE_ACCOUNTING_ERROR;

    default:
      break;
    }

    fr_strerror_printf("Invalid value %d for accounting reply status", pkt->acct_reply.status);
    return -1;

  default:
    fr_strerror_const("Invalid header type");
    return -1;
  }
}

#define PACKET_HEADER_CHECK(_msg, _hdr) do { \
  p = buffer + FR_HEADER_LENGTH; \
  if (sizeof(_hdr) > (size_t) (end - p)) { \
    fr_strerror_printf("Header for %s is too small (%zu < %zu)", _msg, (size_t) (end - (uint8_t const *) pkt), (size_t) (p - (uint8_t const *) pkt)); \
    goto fail; \
  } \
  body = p + sizeof(_hdr); \
  data_len = sizeof(_hdr); \
} while (0)

/*
 *  Check argv[i] after the user_msg / server_msg / argc lengths have been added to data_len
 */
#define ARG_COUNT_CHECK(_msg, _hdr) do { \
  fr_assert(p == (uint8_t const *) &(_hdr)); \
  if (data_len > (size_t) (end - p)) { \
    fr_strerror_printf("Argument count %u overflows the remaining data (%zu) in the %s packet", _hdr.arg_cnt, (size_t) (end - p), _msg); \
    goto fail; \
  } \
  argv = body; \
  attrs = buffer + FR_HEADER_LENGTH + data_len; \
  body += _hdr.arg_cnt; \
  p = attrs; \
  for (unsigned int i = 0; i < _hdr.arg_cnt; i++) { \
    if (_hdr.arg_len[i] > (size_t) (end - p)) { \
      fr_strerror_printf("Argument %u length %u overflows packet", i, _hdr.arg_len[i]); \
      goto fail; \
    } \
    p += _hdr.arg_len[i]; \
  } \
} while (0)

#define DECODE_FIELD_UINT8(_da, _field) do { \
  vp = fr_pair_afrom_da(ctx, _da); \
  if (!vp) goto fail; \
  PAIR_ALLOCED(vp); \
  vp->vp_uint8 = _field; \
  fr_pair_append(out, vp); \
} while (0)

#define DECODE_FIELD_STRING8(_da, _field) do { \
  if (tacacs_decode_field(ctx, out, _da, &p, \
      _field, end) < 0) goto fail; \
} while (0)

#define DECODE_FIELD_STRING16(_da, _field) do { \
  if (tacacs_decode_field(ctx, out, _da, &p, \
      ntohs(_field), end) < 0) goto fail; \
} while (0)

#define BODY(_x) (((uint8_t const *) pkt) + sizeof(pkt->hdr) + sizeof(pkt->_x))

/** Decode a TACACS+ 'arg_N' fields.
 *
 */
static int tacacs_decode_args(TALLOC_CTX *ctx, fr_pair_list_t *out, fr_dict_attr_t const *parent,
            uint8_t arg_cnt, uint8_t const *argv, uint8_t const *attrs, NDEBUG_UNUSED uint8_t const *end)
{
  uint8_t i;
  bool append = false;
  uint8_t const *p = attrs;
  fr_pair_t *vp;
  fr_pair_t *vendor = NULL;
  fr_dict_attr_t const *root;

  /*
   *  No one? Just get out!
   */
  if (!arg_cnt) return 0;

  /*
   *  Try to decode as nested attributes.  If we can't, everything is
   *
   *    Argument-List = "foo=bar"
   */
  if (parent) {
    vendor = fr_pair_find_by_da(out, NULL, parent);
    if (!vendor) {
      vendor = fr_pair_afrom_da(ctx, parent);
      if (!vendor) return -1;
      PAIR_ALLOCED(vendor);

      append = true;
    }
  }

  root = fr_dict_root(dict_tacacs);

  /*
   *  Then, do the dirty job of creating attributes.
   */
  for (i = 0; i < arg_cnt; i++) {
    uint8_t const *value, *name_end, *arg_end;
    fr_dict_attr_t const *da;
    fr_pair_list_t *dst;
    uint8_t buffer[256];

    fr_assert((p + argv[i]) <= end);

    if (argv[i] < 2) goto next; /* skip malformed */

    memcpy(buffer, p, argv[i]);
    buffer[argv[i]] = '\0';

    arg_end = buffer + argv[i];

    for (value = buffer, name_end = NULL; value < arg_end; value++) {
      /*
       *  RFC 8907 Section 3.7 says control
       *  characters MUST be excluded.
       */
      if (*value < ' ') goto next;

      if ((*value == '=') || (*value == '*')) {
        name_end = value;
        buffer[value - buffer] = '\0';
        value++;
        break;
      }
    }

    /*
     *  Skip fields which aren't in "name=value" or "name*value" format.
     */
    if (!name_end) goto next;

    /*
     *  Prefer to decode from the attribute root, first.
     */
    da = fr_dict_attr_by_name(NULL, root, (char *) buffer);
    if (da) {
      vp = fr_pair_afrom_da(ctx, da);
      if (!vp) goto oom;
      PAIR_ALLOCED(vp);

      dst = out;
      goto decode;
    }

    /*
     *  If the attribute isn't in the main dictionary,
     *  maybe it's in the vendor dictionary?
     */
    if (vendor) {
      da = fr_dict_attr_by_name(NULL, parent, (char *) buffer);
      if (!da) goto raw;

      vp = fr_pair_afrom_da(vendor, da);
      if (!vp) goto oom;
      PAIR_ALLOCED(vp);

      dst = &vendor->vp_group;

    decode:
      /*
       *      If it's OCTETS or STRING type, then just copy the value verbatim, as the
       *      contents are (should be?) binary-safe.  But if it's zero length, then don't need to
       *      copy anything.
       *
       *      Note that we copy things manually here because
       *      we don't want the OCTETS type to be parsed as
       *      hex.  And, we don't want the string type to be
       *      unescaped.
       */
      if (da->type == FR_TYPE_OCTETS) {
        if ((arg_end > value) &&
            (fr_pair_value_memdup(vp, value, arg_end - value, true) < 0)) {
          goto fail;
        }

      } else if (da->type == FR_TYPE_STRING) {
        if ((arg_end > value) &&
            (fr_pair_value_bstrndup(vp, (char const *) value, arg_end - value, true) < 0)) {
          goto fail;
        }

      } else if (arg_end == value) {
        /*
         *  Any other leaf type MUST have non-zero contents.
         */
        talloc_free(vp);
        goto raw;

      } else {
        /*
         *      Parse the string, and try to convert it to the
         *      underlying data type.  If it can't be
         *      converted as a data type, just convert it as
         *      Argument-List.
         *
         *      And if that fails, just ignore it completely.
         */
        if (fr_pair_value_from_str(vp, (char const *) value, arg_end - value, NULL, true) < 0) {
          talloc_free(vp);
          goto raw;
        }

        /*
         *  Else it parsed fine, append it to the output vendor list.
         */
      }

      fr_pair_append(dst, vp);

    } else {
    raw:
      vp = fr_pair_afrom_da(ctx, attr_tacacs_argument_list);
      if (!vp) {
      oom:
        fr_strerror_const("Out of Memory");
      fail:
        if (append) {
          talloc_free(vendor);
        } else {
          talloc_free(vp);
        }
        return -1;
      }
      PAIR_ALLOCED(vp);

      value = p;
      arg_end = p + argv[i];

      if ((arg_end > value) &&
          (fr_pair_value_bstrndup(vp, (char const *) value, arg_end - value, true) < 0)) {
        goto fail;
      }

      fr_pair_append(out, vp);
    }

  next:
    p += argv[i];
  }

  if (append) {
    if (fr_pair_list_num_elements(&vendor->vp_group) > 0) {
      fr_pair_append(out, vendor);
    } else {
      talloc_free(vendor);
    }
  }

  return 0;
}

/**
 *  Decode a TACACS+ field.
 */
static int tacacs_decode_field(TALLOC_CTX *ctx, fr_pair_list_t *out, fr_dict_attr_t const *da,
        uint8_t const **field_data, uint16_t field_len, uint8_t const *end)
{
  uint8_t const *p = *field_data;
  fr_pair_t *vp;

  if (field_len > (end - p)) {
    fr_strerror_printf("'%s' length %u overflows the remaining data (%zu) in the packet",
           da->name, field_len, (size_t) (end - p));
    return -1;
  }

  vp = fr_pair_afrom_da(ctx, da);
  if (!vp) {
    fr_strerror_const("Out of Memory");
    return -1;
  }
  PAIR_ALLOCED(vp);

  if (field_len) {
    if (da->type == FR_TYPE_STRING) {
      fr_pair_value_bstrndup(vp, (char const *)p, field_len, true);
    } else if (da->type == FR_TYPE_OCTETS) {
      fr_pair_value_memdup(vp, p, field_len, true);
    } else {
      fr_assert(0);
    }
    p += field_len;
    *field_data = p;
  }

  fr_pair_append(out, vp);

  return 0;
}

/**
 *  Decode a TACACS+ packet
 */
ssize_t fr_tacacs_decode(TALLOC_CTX *ctx, fr_pair_list_t *out, fr_dict_attr_t const *vendor,
       uint8_t const *buffer, size_t buffer_len,
       const uint8_t *original, char const * const secret, size_t secret_len, int *code)
{
  fr_tacacs_packet_t const *pkt;
  fr_pair_t   *vp;
  size_t      data_len;
  uint8_t const     *p, *body, *argv, *attrs, *end;
  uint8_t     *decrypted = NULL;

  /*
   * 3.4. The TACACS+ Packet Header
   *
   * 1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
   * +----------------+----------------+----------------+----------------+
   * |major  | minor  |                |                |                |
   * |version| version|      type      |     seq_no     |   flags        |
   * +----------------+----------------+----------------+----------------+
   * |                                                                   |
   * |                            session_id                             |
   * +----------------+----------------+----------------+----------------+
   * |                                                                   |
   * |                              length                               |
   * +----------------+----------------+----------------+----------------+
   */
  pkt = (fr_tacacs_packet_t const *) buffer;

  /*
   *  p miscellaneous pointer for decoding things
   *  body  points to just past the (randomly sized) per-packet header,
   *    where the various user / server messages are.
   *    sometimes this is after "argv".
   *  argv  points to the array of argv[i] length entries
   *  attrs points to the attributes we need to decode as "foo=bar".
   */
  argv = attrs = NULL;
  end = buffer + buffer_len;

  /*
   *  Check that we have a full TACACS+ header before
   *  decoding anything.
   */
  if (buffer_len < sizeof(pkt->hdr)) {
    fr_strerror_printf("Packet is too small (%zu < 12) to be TACACS+.", buffer_len);
    return -1;
  }

  /*
   *  TACACS major / minor version MUST be 12.0 or 12.1
   */
  if (!(pkt->hdr.ver.major == 12 && (pkt->hdr.ver.minor == 0 || pkt->hdr.ver.minor == 1))) {
    fr_strerror_printf("Unsupported TACACS+ version %d.%d (%02x)", pkt->hdr.ver.major, pkt->hdr.ver.minor, buffer[0]);
    return -1;
  }

  /*
   *  There's no reason to accept 64K TACACS+ packets.
   *
   *  In any case, the largest possible packet has the
   *  header, plus 2 16-bit fields, plus 255 8-bit fields,
   *  which is a bit under 2^18.
   */
  if ((buffer[8] != 0) || (buffer[9] != 0)) {
    fr_strerror_const("Packet is too large.  Our limit is 64K");
    return -1;
  }

  /*
   *  As a stream protocol, the TACACS+ packet MUST fit
   *  exactly into however many bytes we read.
   */
  if ((buffer + sizeof(pkt->hdr) + ntohl(pkt->hdr.length)) != end) {
    fr_strerror_const("Packet does not exactly fill buffer");
    return -1;
  }

  /*
   *  There are only 3 types of packets which are supported.
   */
  if (!((pkt->hdr.type == FR_TAC_PLUS_AUTHEN) ||
        (pkt->hdr.type == FR_TAC_PLUS_AUTHOR) ||
        (pkt->hdr.type == FR_TAC_PLUS_ACCT))) {
    fr_strerror_printf("Unknown packet type %d", pkt->hdr.type);
    return -1;
  }

  /*
   *  Check that the session IDs are correct.
   */
  if (original && (memcmp(original + 4, buffer + 4, 4) != 0)) {
    fr_strerror_printf("Session ID %08x does not match expected number %08x",
           fr_nbo_to_uint32(buffer + 4), fr_nbo_to_uint32(original + 4));
    return -1;
  }

  if (!secret && packet_is_encrypted(pkt)) {
    fr_strerror_const("Packet is encrypted, but there is no secret to decrypt it");
    return -1;
  }

  /*
   *  Call the struct encoder to do the actual work.
   */
  if (fr_struct_from_network(ctx, out, attr_tacacs_packet, buffer, buffer_len, NULL, NULL, NULL) < 0) {
    fr_strerror_printf("Failed decoding TACACS header - %s", fr_strerror());
    return -1;
  }

  /*
   *  3.6. Encryption
   *
   *  If there's a secret, we always decrypt the packets.
   */
  if (secret && packet_is_encrypted(pkt)) {
    size_t length;

    if (!secret_len) {
      fr_strerror_const("Packet should be encrypted, but the secret has zero length");
      return -1;
    }

    length = ntohl(pkt->hdr.length);

    /*
     *  We need that to decrypt the body content.
     *
     *  @todo - use thread-local storage to avoid allocations?
     */
    decrypted = talloc_memdup(ctx, buffer, buffer_len);
    if (!decrypted) {
      fr_strerror_const("Out of Memory");
      return -1;
    }

    pkt = (fr_tacacs_packet_t const *) decrypted;
    end = decrypted + buffer_len;

    if (fr_tacacs_body_xor(pkt, decrypted + sizeof(pkt->hdr), length, secret, secret_len) < 0) {
    fail:
      talloc_free(decrypted);
      return -1;
    }

    decrypted[3] |= FR_TAC_PLUS_UNENCRYPTED_FLAG;

    FR_PROTO_HEX_DUMP(decrypted, buffer_len, "fr_tacacs_packet_t (unencrypted)");

    buffer = decrypted;
  }

#ifndef NDEBUG
  if (fr_debug_lvl >= L_DBG_LVL_4) fr_tacacs_packet_log_hex(&default_log, pkt, (end - buffer));
#endif

  if (code) {
    *code = fr_tacacs_packet_to_code((fr_tacacs_packet_t const *) buffer);
    if (*code < 0) goto fail;
  }

  switch (pkt->hdr.type) {
  case FR_TAC_PLUS_AUTHEN:
    if (packet_is_authen_start_request(pkt)) {
      uint8_t want;
      bool raw;
      fr_dict_attr_t const *da, *challenge;

      /**
       * 4.1. The Authentication START Packet Body
       *
       *  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |    action      |    priv_lvl    |  authen_type   | authen_service |
       * +----------------+----------------+----------------+----------------+
       * |    user_len    |    port_len    |  rem_addr_len  |    data_len    |
       * +----------------+----------------+----------------+----------------+
       * |    user ...
       * +----------------+----------------+----------------+----------------+
       * |    port ...
       * +----------------+----------------+----------------+----------------+
       * |    rem_addr ...
       * +----------------+----------------+----------------+----------------+
       * |    data...
       * +----------------+----------------+----------------+----------------+
       */
      PACKET_HEADER_CHECK("Authentication-Start", pkt->authen_start);

      data_len += p[4] + p[5] + p[6] + p[7];
      if (data_len > (size_t) (end - p)) {
      overflow:
        if ((buffer[3] & FR_TAC_PLUS_UNENCRYPTED_FLAG) == 0) {
        bad_secret:
          fr_strerror_const("Invalid packet after decryption - is the secret key incorrect?");
          goto fail;
        }

        fr_strerror_const("Data overflows the packet");
        goto fail;
      }
      if (data_len < (size_t) (end - p)) {
      underflow:
        if ((buffer[3] & FR_TAC_PLUS_UNENCRYPTED_FLAG) == 0) goto bad_secret;

        fr_strerror_const("Data underflows the packet");
        goto fail;
      }

      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_START);

      /*
       *  Decode 4 octets of various flags.
       */
      DECODE_FIELD_UINT8(attr_tacacs_action, pkt->authen_start.action);
      DECODE_FIELD_UINT8(attr_tacacs_privilege_level, pkt->authen_start.priv_lvl);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_type, pkt->authen_start.authen_type);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_service, pkt->authen_start.authen_service);

      /*
       *  Decode 3 fields, based on their "length"
       *  user and rem_addr are optional - indicated by zero length
       */
      p = body;
      if (pkt->authen_start.user_len > 0) DECODE_FIELD_STRING8(attr_tacacs_user_name,
                     pkt->authen_start.user_len);
      DECODE_FIELD_STRING8(attr_tacacs_client_port, pkt->authen_start.port_len);
      if (pkt->authen_start.rem_addr_len > 0) DECODE_FIELD_STRING8(attr_tacacs_remote_address,
                         pkt->authen_start.rem_addr_len);

      /*
       *  Check the length on the various
       *  authentication types.
       */
      raw = false;
      challenge = NULL;

      switch (pkt->authen_start.authen_type) {
      default:
        raw = true;
        want = pkt->authen_start.data_len;
        da = attr_tacacs_data;
        break;

      case FR_AUTHENTICATION_TYPE_VALUE_PAP:
        want = pkt->authen_start.data_len;
        da = attr_tacacs_user_password;
        break;

      case FR_AUTHENTICATION_TYPE_VALUE_CHAP:
        want = 1 + 16; /* id + HOPEFULLY 8 octets of challenge + 16 hash */
        da = attr_tacacs_chap_password;
        challenge = attr_tacacs_chap_challenge;
        break;

      case FR_AUTHENTICATION_TYPE_VALUE_MSCHAP:
        want = 1 + 49; /* id + HOPEFULLY 8 octets of challenge + 49 MS-CHAP stuff */
        da = attr_tacacs_mschap_response;
        challenge = attr_tacacs_mschap_challenge;
        break;

      case FR_AUTHENTICATION_TYPE_VALUE_MSCHAPV2:
        want = 1 + 49; /* id + HOPEFULLY 16 octets of challenge + 49 MS-CHAP stuff */
        da = attr_tacacs_mschap2_response;
        challenge = attr_tacacs_mschap_challenge;
        break;
      }

      /*
       *  If we have enough data, decode it as
       *  the claimed authentication type.
       *
       *  Otherwise, decode the entire field as an unknown
       *  attribute.
       */
      if (raw || (pkt->authen_start.data_len < want)) {
        fr_dict_attr_t *da_unknown;

        da_unknown = fr_dict_attr_unknown_raw_afrom_num(ctx, fr_dict_root(dict_tacacs),
                    attr_tacacs_data->attr);
        if (!da_unknown) goto fail;

        want = pkt->authen_start.data_len;

        DECODE_FIELD_STRING8(da_unknown, want);
        talloc_free(da_unknown);

      } else if (!challenge) {
        DECODE_FIELD_STRING8(da, want);

      } else if (pkt->authen_start.data_len == want)  {
        fr_strerror_printf("%s has zero length", challenge->name);
        goto fail;

      } else { /* 1 of ID + ??? of challenge + (want-1) of data */
        uint8_t challenge_len = pkt->authen_start.data_len - want;
        uint8_t hash[50];

        /*
         *  Rework things to make sense.
         *  RFC 8079 says that MS-CHAP responses should follow RFC 2433 and 2759
         *  which have "Flags" at the end.
         *  RADIUS attributes expect "Flags" after the ID as per RFC 2548.
         *  Re-arrange to make things consistent.
         */
        hash[0] = p[0];
        switch (pkt->authen_start.authen_type) {
        case FR_AUTHENTICATION_TYPE_VALUE_MSCHAP:
        case FR_AUTHENTICATION_TYPE_VALUE_MSCHAPV2:
          hash[1] = p[want - 1];
          memcpy(hash + 2, p + 1 + challenge_len, want - 2);
          break;

        default:
          memcpy(hash + 1, p + 1 + challenge_len, want - 1);
          break;
        }

        vp = fr_pair_afrom_da(ctx, da);
        if (!vp) goto fail;
        PAIR_ALLOCED(vp);

        fr_pair_append(out, vp);

        /*
         *  ID + hash
         */
        if (fr_pair_value_memdup(vp, hash, want, true) < 0) goto fail;

        /*
         *  And then the challenge.
         */
        vp = fr_pair_afrom_da(ctx, challenge);
        if (!vp) goto fail;
        PAIR_ALLOCED(vp);

        fr_pair_append(out, vp);

        if (fr_pair_value_memdup(vp, p + 1, challenge_len, true) < 0) goto fail;

        p += pkt->authen_start.data_len;
      }

    } else if (packet_is_authen_continue(pkt)) {
      /*
       * 4.3. The Authentication CONTINUE Packet Body
       *
       * This packet is sent from the client to the server following the receipt of
       * a REPLY packet.
       *
       *  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |          user_msg len           |            data_len             |
       * +----------------+----------------+----------------+----------------+
       * |     flags      |  user_msg ...
       * +----------------+----------------+----------------+----------------+
       * |    data ...
       * +----------------+
       */

      /*
       *  Version 1 is ONLY used for PAP / CHAP
       *  / MS-CHAP start and reply packets.
       */
      if (pkt->hdr.ver.minor != 0) {
      invalid_version:
        fr_strerror_const("Invalid TACACS+ version");
        goto fail;
      }

      PACKET_HEADER_CHECK("Authentication-Continue", pkt->authen_cont);
      data_len += fr_nbo_to_uint16(p) + fr_nbo_to_uint16(p + 2);
      if (data_len > (size_t) (end - p)) goto overflow;
      if (data_len < (size_t) (end - p)) goto underflow;

      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_CONTINUE);

      /*
       *  Decode 2 fields, based on their "length"
       */
      p = body;
      DECODE_FIELD_STRING16(attr_tacacs_user_message, pkt->authen_cont.user_msg_len);
      DECODE_FIELD_STRING16(attr_tacacs_data, pkt->authen_cont.data_len);

      /*
       *  And finally the flags.
       */
      DECODE_FIELD_UINT8(attr_tacacs_authentication_continue_flags, pkt->authen_cont.flags);

    } else if (packet_is_authen_reply(pkt)) {
      /*
       * 4.2. The Authentication REPLY Packet Body
       *
       * 1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |     status     |      flags     |        server_msg_len           |
       * +----------------+----------------+----------------+----------------+
       * |           data_len              |        server_msg ...
       * +----------------+----------------+----------------+----------------+
       * |           data ...
       * +----------------+----------------+
       */

      /*
       *  We don't care about versions for replies.
       *  We just echo whatever was sent in the request.
       */
      PACKET_HEADER_CHECK("Authentication-Reply", pkt->authen_reply);
      data_len += fr_nbo_to_uint16(p + 2) + fr_nbo_to_uint16(p + 4);
      if (data_len > (size_t) (end - p)) goto overflow;
      if (data_len < (size_t) (end - p)) goto underflow;

      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_REPLY);

      DECODE_FIELD_UINT8(attr_tacacs_authentication_status, pkt->authen_reply.status);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_flags, pkt->authen_reply.flags);

      /*
       *  Decode 2 fields, based on their "length"
       */
      p = body;
      DECODE_FIELD_STRING16(attr_tacacs_server_message, pkt->authen_reply.server_msg_len);
      DECODE_FIELD_STRING16(attr_tacacs_data, pkt->authen_reply.data_len);

    } else {
      fr_strerror_const("Unknown authentication packet");
      goto fail;
    }
    break;

  case FR_TAC_PLUS_AUTHOR:
    if (packet_is_author_request(pkt)) {
      /*
       * 5.1. The Authorization REQUEST Packet Body
       *
       *  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |  authen_method |    priv_lvl    |  authen_type   | authen_service |
       * +----------------+----------------+----------------+----------------+
       * |    user_len    |    port_len    |  rem_addr_len  |    arg_cnt     |
       * +----------------+----------------+----------------+----------------+
       * |   arg_1_len    |   arg_2_len    |      ...       |   arg_N_len    |
       * +----------------+----------------+----------------+----------------+
       * |   user ...
       * +----------------+----------------+----------------+----------------+
       * |   port ...
       * +----------------+----------------+----------------+----------------+
       * |   rem_addr ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_1 ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_2 ...
       * +----------------+----------------+----------------+----------------+
       * |   ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_N ...
       * +----------------+----------------+----------------+----------------+
       */

      if (pkt->hdr.ver.minor != 0) goto invalid_version;

      PACKET_HEADER_CHECK("Authorization-Request", pkt->author_req);
      data_len += p[4] + p[5] + p[6] + p[7];

      ARG_COUNT_CHECK("Authorization-Request", pkt->author_req);

      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_REQUEST);

      /*
       *  Decode 4 octets of various flags.
       */
      DECODE_FIELD_UINT8(attr_tacacs_authentication_method, pkt->author_req.authen_method);
      DECODE_FIELD_UINT8(attr_tacacs_privilege_level, pkt->author_req.priv_lvl);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_type, pkt->author_req.authen_type);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_service, pkt->author_req.authen_service);

      /*
       *  Decode 3 fields, based on their "length"
       *  rem_addr is optional - indicated by zero length
       */
      p = body;
      DECODE_FIELD_STRING8(attr_tacacs_user_name, pkt->author_req.user_len);
      DECODE_FIELD_STRING8(attr_tacacs_client_port, pkt->author_req.port_len);
      if (pkt->author_req.rem_addr_len > 0) DECODE_FIELD_STRING8(attr_tacacs_remote_address,
                       pkt->author_req.rem_addr_len);

      /*
       *  Decode 'arg_N' arguments (horrible format)
       */
      if (tacacs_decode_args(ctx, out, vendor,
                 pkt->author_req.arg_cnt, argv, attrs, end) < 0) goto fail;

    } else if (packet_is_author_reply(pkt)) {
      /*
       * 5.2. The Authorization RESPONSE Packet Body
       *
       *  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |    status      |     arg_cnt    |         server_msg len          |
       * +----------------+----------------+----------------+----------------+
       * +            data_len             |    arg_1_len   |    arg_2_len   |
       * +----------------+----------------+----------------+----------------+
       * |      ...       |   arg_N_len    |         server_msg ...
       * +----------------+----------------+----------------+----------------+
       * |   data ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_1 ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_2 ...
       * +----------------+----------------+----------------+----------------+
       * |   ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_N ...
       * +----------------+----------------+----------------+----------------+
       */

      /*
       *  We don't care about versions for replies.
       *  We just echo whatever was sent in the request.
       */

      PACKET_HEADER_CHECK("Authorization-Reply", pkt->author_reply);
      data_len += p[1] + fr_nbo_to_uint16(p + 2) + fr_nbo_to_uint16(p + 4);

      ARG_COUNT_CHECK("Authorization-Reply", pkt->author_reply);
      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_RESPONSE);

      /*
       *  Decode 1 octets
       */
      DECODE_FIELD_UINT8(attr_tacacs_authorization_status, pkt->author_reply.status);

      /*
       *  Decode 2 fields, based on their "length"
       */
      p = body;
      DECODE_FIELD_STRING16(attr_tacacs_server_message, pkt->author_reply.server_msg_len);
      DECODE_FIELD_STRING16(attr_tacacs_data, pkt->author_reply.data_len);

      /*
       *  Decode 'arg_N' arguments (horrible format)
       */
      if (tacacs_decode_args(ctx, out, vendor,
                 pkt->author_reply.arg_cnt, argv, attrs, end) < 0) goto fail;

    } else {
      fr_strerror_const("Unknown authorization packet");
      goto fail;
    }
    break;

  case FR_TAC_PLUS_ACCT:
    if (packet_is_acct_request(pkt)) {
      /**
       * 6.1. The Account REQUEST Packet Body
       *
       1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |      flags     |  authen_method |    priv_lvl    |  authen_type   |
       * +----------------+----------------+----------------+----------------+
       * | authen_service |    user_len    |    port_len    |  rem_addr_len  |
       * +----------------+----------------+----------------+----------------+
       * |    arg_cnt     |   arg_1_len    |   arg_2_len    |      ...       |
       * +----------------+----------------+----------------+----------------+
       * |   arg_N_len    |    user ...
       * +----------------+----------------+----------------+----------------+
       * |   port ...
       * +----------------+----------------+----------------+----------------+
       * |   rem_addr ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_1 ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_2 ...
       * +----------------+----------------+----------------+----------------+
       * |   ...
       * +----------------+----------------+----------------+----------------+
       * |   arg_N ...
       * +----------------+----------------+----------------+----------------+
       */

      if (pkt->hdr.ver.minor != 0) goto invalid_version;

      PACKET_HEADER_CHECK("Accounting-Request", pkt->acct_req);
      data_len += p[5] + p[6] + p[7] + p[8];
      if (data_len > (size_t) (end - p)) goto overflow;
      /* can't check for underflow, as we have argv[argc] */

      ARG_COUNT_CHECK("Accounting-Request", pkt->acct_req);

      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_REQUEST);

      /*
       *  Decode 5 octets of various flags.
       */
      DECODE_FIELD_UINT8(attr_tacacs_accounting_flags, pkt->acct_req.flags);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_method, pkt->acct_req.authen_method);
      DECODE_FIELD_UINT8(attr_tacacs_privilege_level, pkt->acct_req.priv_lvl);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_type, pkt->acct_req.authen_type);
      DECODE_FIELD_UINT8(attr_tacacs_authentication_service, pkt->acct_req.authen_service);

      /*
       *  Decode 3 fields, based on their "length"
       */
      p = body;
      DECODE_FIELD_STRING8(attr_tacacs_user_name, pkt->acct_req.user_len);
      DECODE_FIELD_STRING8(attr_tacacs_client_port, pkt->acct_req.port_len);
      DECODE_FIELD_STRING8(attr_tacacs_remote_address, pkt->acct_req.rem_addr_len);

      /*
       *  Decode 'arg_N' arguments (horrible format)
       */
      if (tacacs_decode_args(ctx, out, vendor,
                 pkt->acct_req.arg_cnt, argv, attrs, end) < 0) goto fail;

    } else if (packet_is_acct_reply(pkt)) {
      /**
       * 6.2. The Accounting REPLY Packet Body
       *
       * 1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
       * +----------------+----------------+----------------+----------------+
       * |         server_msg len          |            data_len             |
       * +----------------+----------------+----------------+----------------+
       * |     status     |         server_msg ...
       * +----------------+----------------+----------------+----------------+
       * |     data ...
       * +----------------+
       */

      /*
       *  We don't care about versions for replies.
       *  We just echo whatever was sent in the request.
       */

      PACKET_HEADER_CHECK("Accounting-Reply", pkt->acct_reply);
      data_len += fr_nbo_to_uint16(p) + fr_nbo_to_uint16(p + 2);
      if (data_len > (size_t) (end - p)) goto overflow;
      if (data_len < (size_t) (end - p)) goto underflow;

      p = BODY(acct_reply);
      DECODE_FIELD_UINT8(attr_tacacs_packet_body_type, FR_PACKET_BODY_TYPE_REPLY);

      /*
       *  Decode 2 fields, based on their "length"
       */
      DECODE_FIELD_STRING16(attr_tacacs_server_message, pkt->acct_reply.server_msg_len);
      DECODE_FIELD_STRING16(attr_tacacs_data, pkt->acct_reply.data_len);

      /* Decode 1 octet */
      DECODE_FIELD_UINT8(attr_tacacs_accounting_status, pkt->acct_reply.status);
    } else {
      fr_strerror_const("Unknown accounting packet");
      goto fail;
    }
    break;
  default:
    fr_strerror_printf("decode: Unsupported packet type %d", pkt->hdr.type);
    goto fail;
  }

  talloc_free(decrypted);
  return buffer_len;
}

/*
 *  Test points for protocol decode
 */
static ssize_t fr_tacacs_decode_proto(TALLOC_CTX *ctx, fr_pair_list_t *out, uint8_t const *data, size_t data_len, void *proto_ctx)
{
  fr_tacacs_ctx_t *test_ctx = talloc_get_type_abort(proto_ctx, fr_tacacs_ctx_t);
  fr_dict_attr_t const *dv;

  dv = fr_dict_attr_by_name(NULL, fr_dict_root(dict_tacacs), "Test");
  fr_assert(!dv || (dv->type == FR_TYPE_VENDOR));

  return fr_tacacs_decode(ctx, out, dv, data, data_len, NULL, test_ctx->secret,
        test_ctx->secret ? talloc_strlen(test_ctx->secret) : 0, NULL);
}

static int _encode_test_ctx(fr_tacacs_ctx_t *test_ctx)
{
  talloc_const_free(test_ctx->secret);

  fr_tacacs_global_free();

  return 0;
}

static int decode_test_ctx(void **out, TALLOC_CTX *ctx, UNUSED fr_dict_t const *dict,
         UNUSED fr_dict_attr_t const *root_da)
{
  fr_tacacs_ctx_t *test_ctx;

  if (fr_tacacs_global_init() < 0) return -1;

  test_ctx = talloc_zero(ctx, fr_tacacs_ctx_t);
  if (!test_ctx) return -1;

  test_ctx->secret = talloc_strdup(test_ctx, "testing123");
  test_ctx->root = fr_dict_root(dict_tacacs);
  talloc_set_destructor(test_ctx, _encode_test_ctx);

  *out = test_ctx;

  return 0;
}

extern fr_test_point_proto_decode_t tacacs_tp_decode_proto;
fr_test_point_proto_decode_t tacacs_tp_decode_proto = {
  .test_ctx = decode_test_ctx,
  .func   = fr_tacacs_decode_proto
};

Coverage Report

Created: 2026-04-12 06:36