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radius.c

// L2TPNS Radius Stuff

char const *cvs_id_radius = "$Id: radius.c,v 1.49.2.2 2006/08/02 14:17:20 bodea Exp $";

#include <time.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <malloc.h>
#include <string.h>
#include <fcntl.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <netinet/in.h>
#include <errno.h>
#include "md5.h"
#include "constants.h"
#include "l2tpns.h"
#include "plugin.h"
#include "util.h"
#include "cluster.h"

extern radiust *radius;
extern sessiont *session;
extern tunnelt *tunnel;
extern configt *config;
extern int *radfds;
extern ip_filtert *ip_filters;

static const hasht zero;

static void calc_auth(const void *buf, size_t len, const uint8_t *in, uint8_t *out)
{
      MD5_CTX ctx;

      MD5_Init(&ctx);
      MD5_Update(&ctx, (void *)buf, 4); // code, id, length
      MD5_Update(&ctx, (void *)in, 16); // auth
      MD5_Update(&ctx, (void *)(buf + 20), len - 20);
      MD5_Update(&ctx, config->radiussecret, strlen(config->radiussecret));
      MD5_Final(out, &ctx);
}

// Set up socket for radius requests
void initrad(void)
{
      int i;
      LOG(3, 0, 0, "Creating %d sockets for RADIUS queries\n", RADIUS_FDS);
      radfds = calloc(sizeof(int), RADIUS_FDS);
      for (i = 0; i < RADIUS_FDS; i++)
      {
            int flags;
            radfds[i] = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
            flags = fcntl(radfds[i], F_GETFL, 0);
            fcntl(radfds[i], F_SETFL, flags | O_NONBLOCK);
      }
}

void radiusclear(uint16_t r, sessionidt s)
{
      if (s) sess_local[s].radius = 0;
      memset(&radius[r], 0, sizeof(radius[r])); // radius[r].state = RADIUSNULL;
}

static uint16_t get_free_radius()
{
      int count;
      static uint32_t next_radius_id = 0;

      for (count = MAXRADIUS; count > 0; --count)
      {
            ++next_radius_id;       // Find the next ID to check.
            if (next_radius_id >= MAXRADIUS)
                  next_radius_id = 1;

            if (radius[next_radius_id].state == RADIUSNULL)
            {
                  return next_radius_id;
            }
      }

      LOG(0, 0, 0, "Can't find a free radius session! This is very bad!\n");
      return 0;
}

uint16_t radiusnew(sessionidt s)
{
      uint16_t r = sess_local[s].radius;

      /* re-use */
      if (r)
      {
            LOG(3, s, session[s].tunnel, "Re-used radius %d\n", r);
            return r;
      }

      if (!(r = get_free_radius()))
      {
            LOG(1, s, session[s].tunnel, "No free RADIUS sessions\n");
            STAT(radius_overflow);
            return 0;
      };

      memset(&radius[r], 0, sizeof(radius[r]));
      sess_local[s].radius = r;
      radius[r].session = s;
      radius[r].state = RADIUSWAIT;
      radius[r].retry = TIME + 1200; // Wait at least 120 seconds to re-claim this.

      random_data(radius[r].auth, sizeof(radius[r].auth));

      LOG(3, s, session[s].tunnel, "Allocated radius %d\n", r);
      return r;
}

// Send a RADIUS request
void radiussend(uint16_t r, uint8_t state)
{
      struct sockaddr_in addr;
      uint8_t b[4096];            // RADIUS packet
      char pass[129];
      int pl;
      uint8_t *p;
      sessionidt s;

      CSTAT(radiussend);

      s = radius[r].session;
      if (!config->numradiusservers)
      {
            LOG(0, s, session[s].tunnel, "No RADIUS servers\n");
            return;
      }
      if (!*config->radiussecret)
      {
            LOG(0, s, session[s].tunnel, "No RADIUS secret\n");
            return;
      }

      if (state != RADIUSAUTH && !config->radius_accounting)
      {
            // Radius accounting is turned off
            radiusclear(r, s);
            return;
      }

      if (radius[r].state != state)
            radius[r].try = 0;

      radius[r].state = state;
      radius[r].retry = backoff(radius[r].try++) + 20; // 3s, 4s, 6s, 10s...
      LOG(4, s, session[s].tunnel, "Send RADIUS id %d sock %d state %s try %d\n",
            r >> RADIUS_SHIFT, r & RADIUS_MASK,
            radius_state(radius[r].state), radius[r].try);

      if (radius[r].try > config->numradiusservers * 2)
      {
            if (s)
            {
                  if (state == RADIUSAUTH)
                        sessionshutdown(s, "RADIUS timeout.", CDN_ADMIN_DISC, TERM_REAUTHENTICATION_FAILURE);
                  else
                  {
                        LOG(1, s, session[s].tunnel, "RADIUS timeout, but in state %s so don't timeout session\n",
                              radius_state(state));
                        radiusclear(r, s);
                  }
                  STAT(radius_timeout);
            }
            else
            {
                  STAT(radius_retries);
                  radius[r].state = RADIUSWAIT;
                  radius[r].retry = 100;
            }
            return;
      }
      // contruct RADIUS access request
      switch (state)
      {
            case RADIUSAUTH:
                  b[0] = AccessRequest;               // access request
                  break;
            case RADIUSSTART:
            case RADIUSSTOP:
            case RADIUSINTERIM:
                  b[0] = AccountingRequest;               // accounting request
                  break;
            default:
                  LOG(0, 0, 0, "Unknown radius state %d\n", state);
      }
      b[1] = r >> RADIUS_SHIFT;       // identifier
      memcpy(b + 4, radius[r].auth, 16);
      p = b + 20;
      if (s)
      {
            *p = 1;                 // user name
            p[1] = strlen(session[s].user) + 2;
            strcpy((char *) p + 2, session[s].user);
            p += p[1];
      }
      if (state == RADIUSAUTH)
      {
            if (radius[r].chap)
            {
                  *p = 3;            // CHAP password
                  p[1] = 19;         // length
                  p[2] = radius[r].id; // ID
                  memcpy(p + 3, radius[r].pass, 16); // response from CHAP request
                  p += p[1];
                  *p = 60;           // CHAP Challenge
                  p[1] = 18;         // length
                  memcpy(p + 2, radius[r].auth, 16);
                  p += p[1];
            }
            else
            {
                  strcpy(pass, radius[r].pass);
                  pl = strlen(pass);
                  while (pl & 15)
                        pass[pl++] = 0; // pad
                  if (pl)
                  {                // encrypt
                        hasht hash;
                        int p = 0;
                        while (p < pl)
                        {
                              MD5_CTX ctx;
                              MD5_Init(&ctx);
                              MD5_Update(&ctx, config->radiussecret, strlen(config->radiussecret));
                              if (p)
                                    MD5_Update(&ctx, pass + p - 16, 16);
                              else
                                    MD5_Update(&ctx, radius[r].auth, 16);
                              MD5_Final(hash, &ctx);
                              do
                              {
                                    pass[p] ^= hash[p & 15];
                                    p++;
                              }
                              while (p & 15);
                        }
                  }
                  *p = 2;            // password
                  p[1] = pl + 2;
                  if (pl)
                        memcpy(p + 2, pass, pl);
                  p += p[1];
            }
      }
      else // accounting
      {
            *p = 40;    // accounting type
            p[1] = 6;
            *(uint32_t *) (p + 2) = htonl(state - RADIUSSTART + 1); // start=1, stop=2, interim=3
            p += p[1];
            if (s)
            {
                  *p = 44;    // session ID
                  p[1] = 18;
                  sprintf((char *) p + 2, "%08X%08X", session[s].unique_id, session[s].opened);
                  p += p[1];
                  if (state == RADIUSSTART)
                  {                 // start
                        *p = 41;    // delay
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(time(NULL) - session[s].opened);
                        p += p[1];
                        sess_local[s].last_interim = time_now; // Setup "first" Interim
                  }
                  else
                  {                 // stop, interim
                        *p = 42;    // input octets
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(session[s].cin);
                        p += p[1];

                        *p = 43;    // output octets
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(session[s].cout);
                        p += p[1];

                        *p = 46;    // session time
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(time(NULL) - session[s].opened);
                        p += p[1];

                        *p = 47;    // input packets
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(session[s].pin);
                        p += p[1];

                        *p = 48;    // output packets
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(session[s].pout);
                        p += p[1];

                        *p = 52;    // input gigawords
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(session[s].cin_wrap);
                        p += p[1];

                        *p = 53;    // output gigawords
                        p[1] = 6;
                        *(uint32_t *) (p + 2) = htonl(session[s].cout_wrap);
                        p += p[1];

                        if (state == RADIUSSTOP && radius[r].term_cause)
                        {
                              *p = 49; // acct-terminate-cause
                              p[1] = 6;
                              *(uint32_t *) (p + 2) = htonl(radius[r].term_cause);
                              p += p[1];

                              if (radius[r].term_msg)
                              {
                                    *p = 26;                      // vendor-specific
                                    *(uint32_t *) (p + 2) = htonl(9);   // Cisco
                                    p[6] = 1;                     // Cisco-AVPair
                                    p[7] = 2 + sprintf((char *) p + 8, "disc-cause-ext=%s", radius[r].term_msg);
                                    p[1] = p[7] + 6;
                                    p += p[1];
                              }
                        }
                  }

                  {
                        struct param_radius_account acct = { &tunnel[session[s].tunnel], &session[s], &p };
                        run_plugins(PLUGIN_RADIUS_ACCOUNT, &acct);
                  }
            }
      }
      if (s)
      {
            *p = 5;           // NAS-Port
            p[1] = 6;
            *(uint32_t *) (p + 2) = htonl(s);
            p += p[1];

              *p = 6;         // Service-Type
            p[1] = 6;
            *(uint32_t *) (p + 2) = htonl(2); // Framed-User
            p += p[1];
               
              *p = 7;         // Framed-Protocol
            p[1] = 6;
            *(uint32_t *) (p + 2) = htonl(1); // PPP
            p += p[1];
      }
      if (s && session[s].ip)
      {
            *p = 8;                 // Framed-IP-Address
            p[1] = 6;
            *(uint32_t *) (p + 2) = htonl(session[s].ip);
            p += p[1];
      }
      if (s && session[s].route[0].ip)
      {
            int r;
            for (r = 0; s && r < MAXROUTE && session[s].route[r].ip; r++)
            {
                  int width = 32;
                  if (session[s].route[r].mask)
                  {
                      int mask = session[s].route[r].mask;
                      while (!(mask & 1))
                      {
                        width--;
                        mask >>= 1;
                      }
                  }

                  *p = 22;    // Framed-Route
                  p[1] = sprintf((char *) p + 2, "%s/%d %s 1",
                        fmtaddr(htonl(session[s].route[r].ip), 0),
                        width, fmtaddr(htonl(session[s].ip), 1)) + 2;

                  p += p[1];
            }
      }
      if (*session[s].called)
      {
            *p = 30;                // called
            p[1] = strlen(session[s].called) + 2;
            strcpy((char *) p + 2, session[s].called);
            p += p[1];
      }
      if (*session[s].calling)
      {
            *p = 31;                // calling
            p[1] = strlen(session[s].calling) + 2;
            strcpy((char *) p + 2, session[s].calling);
            p += p[1];
      }
      // NAS-IP-Address
      *p = 4;
      p[1] = 6;
      *(uint32_t *)(p + 2) = config->bind_address;
      p += p[1];

      // All AVpairs added
      *(uint16_t *) (b + 2) = htons(p - b);
      if (state != RADIUSAUTH)
      {
            // Build auth for accounting packet
            calc_auth(b, p - b, zero, b + 4);
            memcpy(radius[r].auth, b + 4, 16);
      }
      memset(&addr, 0, sizeof(addr));
      addr.sin_family = AF_INET;
      *(uint32_t *) & addr.sin_addr = config->radiusserver[(radius[r].try - 1) % config->numradiusservers];
      {
            // get radius port
            uint16_t port = config->radiusport[(radius[r].try - 1) % config->numradiusservers];
            // assume RADIUS accounting port is the authentication port +1
            addr.sin_port = htons((state == RADIUSAUTH) ? port : port+1);
      }

      LOG_HEX(5, "RADIUS Send", b, (p - b));
      sendto(radfds[r & RADIUS_MASK], b, p - b, 0, (void *) &addr, sizeof(addr));
}

static void handle_avpair(sessionidt s, uint8_t *avp, int len)
{
      uint8_t *key = avp;
      uint8_t *value = memchr(avp, '=', len);
      uint8_t tmp[2048] = "";

      if (value)
      {
            *value++ = 0;
            len -= value - key;
      }
      else
      {
            value = tmp;
            len = 0;
      }

      // strip quotes
      if (len > 2 && (*value == '"' || *value == '\'') && value[len - 1] == *value)
      {
            value++;
            len--;
            value[len - 1] = 0;
      }
      // copy and null terminate
      else if (len < sizeof(tmp) - 1)
      {
            memcpy(tmp, value, len);
            tmp[len] = 0;
            value = tmp;
      }
      else
            return;
      
      // Run hooks
      {
            struct param_radius_response p = { &tunnel[session[s].tunnel], &session[s], (char *) key, (char *) value };
            run_plugins(PLUGIN_RADIUS_RESPONSE, &p);
      }
}

// process RADIUS response
void processrad(uint8_t *buf, int len, char socket_index)
{
      uint8_t b[MAXETHER];
      uint16_t r;
      sessionidt s;
      tunnelidt t = 0;
      hasht hash;
      uint8_t routes = 0;
      int r_code;
      int r_id;

      CSTAT(processrad);

      LOG_HEX(5, "RADIUS Response", buf, len);
      if (len < 20 || len < ntohs(*(uint16_t *) (buf + 2)))
      {
            LOG(1, 0, 0, "Duff RADIUS response length %d\n", len);
            return ;
      }

      r_code = buf[0]; // response type
      r_id = buf[1]; // radius reply indentifier.

      len = ntohs(*(uint16_t *) (buf + 2));
      r = socket_index | (r_id << RADIUS_SHIFT);
      s = radius[r].session;
      LOG(3, s, session[s].tunnel, "Received %s, radius %d response for session %u (%s, id %d)\n",
                  radius_state(radius[r].state), r, s, radius_code(r_code), r_id);

      if (!s && radius[r].state != RADIUSSTOP)
      {
            LOG(1, s, session[s].tunnel, "   Unexpected RADIUS response\n");
            return;
      }
      if (radius[r].state != RADIUSAUTH && radius[r].state != RADIUSSTART
          && radius[r].state != RADIUSSTOP && radius[r].state != RADIUSINTERIM)
      {
            LOG(1, s, session[s].tunnel, "   Unexpected RADIUS response\n");
            return;
      }
      t = session[s].tunnel;
      calc_auth(buf, len, radius[r].auth, hash);
      do {
            if (memcmp(hash, buf + 4, 16))
            {
                  LOG(0, s, session[s].tunnel, "   Incorrect auth on RADIUS response!! (wrong secret in radius config?)\n");
                  return; // Do nothing. On timeout, it will try the next radius server.
            }

            if ((radius[r].state == RADIUSAUTH && r_code != AccessAccept && r_code != AccessReject) ||
                  ((radius[r].state == RADIUSSTART || radius[r].state == RADIUSSTOP || radius[r].state == RADIUSINTERIM) && r_code != AccountingResponse))
            {
                  LOG(1, s, session[s].tunnel, "   Unexpected RADIUS response %s\n", radius_code(r_code));
                  return; // We got something we didn't expect. Let the timeouts take
                        // care off finishing the radius session if that's really correct.
            }

            if (radius[r].state == RADIUSAUTH)
            {
                  // run post-auth plugin
                  struct param_post_auth packet = {
                        &tunnel[t],
                        &session[s],
                        session[s].user,
                        (r_code == AccessAccept),
                        radius[r].chap ? PPPCHAP : PPPPAP
                  };

                  run_plugins(PLUGIN_POST_AUTH, &packet);
                  r_code = packet.auth_allowed ? AccessAccept : AccessReject;

                  // process auth response
                  if (radius[r].chap)
                  {
                        // CHAP
                        uint8_t *p = makeppp(b, sizeof(b), 0, 0, s, t, PPPCHAP);
                        if (!p) return;   // Abort!

                        *p = (r_code == AccessAccept) ? 3 : 4;     // ack/nak
                        p[1] = radius[r].id;
                        *(uint16_t *) (p + 2) = ntohs(4); // no message
                        tunnelsend(b, (p - b) + 4, t); // send it

                        LOG(3, s, session[s].tunnel, "   CHAP User %s authentication %s.\n", session[s].user,
                                    (r_code == AccessAccept) ? "allowed" : "denied");
                  }
                  else
                  {
                        // PAP
                        uint8_t *p = makeppp(b, sizeof(b), 0, 0, s, t, PPPPAP);
                        if (!p) return;         // Abort!

                        // ack/nak
                        *p = r_code;
                        p[1] = radius[r].id;
                        *(uint16_t *) (p + 2) = ntohs(5);
                        p[4] = 0; // no message
                        tunnelsend(b, (p - b) + 5, t); // send it

                        LOG(3, s, session[s].tunnel, "   PAP User %s authentication %s.\n", session[s].user,
                                    (r_code == AccessAccept) ? "allowed" : "denied");
                  }

                  if (r_code == AccessAccept)
                  {
                        // Login successful
                        // Extract IP, routes, etc
                        uint8_t *p = buf + 20;
                        uint8_t *e = buf + len;
                        for (; p + 2 <= e && p[1] && p + p[1] <= e; p += p[1])
                        {
                              if (*p == 26 && p[1] >= 7)
                              {
                                    // Vendor-Specific Attribute
                                    uint32_t vendor = ntohl(*(int *)(p + 2));
                                    uint8_t attrib = *(p + 6);
                                    int attrib_length = *(p + 7) - 2;

                                    LOG(4, s, session[s].tunnel, "   Radius reply contains Vendor-Specific.  Vendor=%u Attrib=%u Length=%d\n", vendor, attrib, attrib_length);
                                    if (vendor == 9 && attrib == 1) // Cisco-AVPair
                                    {
                                          if (attrib_length < 0) continue;
                                          LOG(3, s, session[s].tunnel, "      Cisco-AVPair value: %.*s\n",
                                                attrib_length, p + 8);

                                          handle_avpair(s, p + 8, attrib_length);
                                          continue;
                                    }
                                    else if (vendor == 529 && attrib >= 135 && attrib <= 136) // Ascend
                                    {
                                          // handle old-format ascend DNS attributes below
                                          p += 6;
                                    }
                                    else
                                    {
                                          LOG(3, s, session[s].tunnel, "      Unknown vendor-specific\n");
                                          continue;
                                    }
                              }

                              if (*p == 8)
                              {
                                    // Framed-IP-Address
                                    if (p[1] < 6) continue;
                                    session[s].ip = ntohl(*(uint32_t *) (p + 2));
                                    session[s].ip_pool_index = -1;
                                    LOG(3, s, session[s].tunnel, "   Radius reply contains IP address %s\n",
                                          fmtaddr(htonl(session[s].ip), 0));

                                    if (session[s].ip == 0xFFFFFFFE)
                                          session[s].ip = 0; // assign from pool
                              }
                              else if (*p == 135)
                              {
                                    // DNS address
                                    if (p[1] < 6) continue;
                                    session[s].dns1 = ntohl(*(uint32_t *) (p + 2));
                                    LOG(3, s, session[s].tunnel, "   Radius reply contains primary DNS address %s\n",
                                          fmtaddr(htonl(session[s].dns1), 0));
                              }
                              else if (*p == 136)
                              {
                                    // DNS address
                                    if (p[1] < 6) continue;
                                    session[s].dns2 = ntohl(*(uint32_t *) (p + 2));
                                    LOG(3, s, session[s].tunnel, "   Radius reply contains secondary DNS address %s\n",
                                          fmtaddr(htonl(session[s].dns2), 0));
                              }
                              else if (*p == 22)
                              {
                                    // Framed-Route
                                    in_addr_t ip = 0, mask = 0;
                                    uint8_t u = 0;
                                    uint8_t bits = 0;
                                    uint8_t *n = p + 2;
                                    uint8_t *e = p + p[1];
                                    while (n < e && (isdigit(*n) || *n == '.'))
                                    {
                                          if (*n == '.')
                                          {
                                                ip = (ip << 8) + u;
                                                u = 0;
                                          }
                                          else
                                                u = u * 10 + *n - '0';
                                          n++;
                                    }
                                    ip = (ip << 8) + u;
                                    if (*n == '/')
                                    {
                                          n++;
                                          while (n < e && isdigit(*n))
                                                bits = bits * 10 + *n++ - '0';
                                          mask = (( -1) << (32 - bits));
                                    }
                                    else if ((ip >> 24) < 128)
                                          mask = 0xFF0000;
                                    else if ((ip >> 24) < 192)
                                          mask = 0xFFFF0000;
                                    else
                                          mask = 0xFFFFFF00;

                                    if (routes == MAXROUTE)
                                    {
                                          LOG(1, s, session[s].tunnel, "   Too many routes\n");
                                    }
                                    else if (ip)
                                    {
                                          LOG(3, s, session[s].tunnel, "   Radius reply contains route for %s/%s\n",
                                                fmtaddr(htonl(ip), 0), fmtaddr(htonl(mask), 1));
                                          
                                          session[s].route[routes].ip = ip;
                                          session[s].route[routes].mask = mask;
                                          routes++;
                                    }
                              }
                              else if (*p == 11)
                              {
                                    // Filter-Id
                                    char *filter = (char *) p + 2;
                                    int l = p[1] - 2;
                                    char *suffix;
                                    int f;
                                    uint8_t *fp = 0;

                                    LOG(3, s, session[s].tunnel, "   Radius reply contains Filter-Id \"%.*s\"\n", l, filter);
                                    if ((suffix = memchr(filter, '.', l)))
                                    {
                                          int b = suffix - filter;
                                          if (l - b == 3 && !memcmp("in", suffix+1, 2))
                                                fp = &session[s].filter_in;
                                          else if (l - b == 4 && !memcmp("out", suffix+1, 3))
                                                fp = &session[s].filter_out;

                                          l = b;
                                    }

                                    if (!fp)
                                    {
                                          LOG(3, s, session[s].tunnel, "    Invalid filter\n");
                                          continue;
                                    }

                                    if ((f = find_filter(filter, l)) < 0 || !*ip_filters[f].name)
                                    {
                                          LOG(3, s, session[s].tunnel, "    Unknown filter\n");
                                    }
                                    else
                                    {
                                          *fp = f + 1;
                                          ip_filters[f].used++;
                                    }
                              }
                              else if (*p == 99)
                              {
                                    // Framed-IPv6-Route
                                    struct in6_addr r6;
                                    int prefixlen;
                                    uint8_t *n = p + 2;
                                    uint8_t *e = p + p[1];
                                    uint8_t *m = memchr(n, '/', e - p);

                                    *m++ = 0;
                                    inet_pton(AF_INET6, (char *) n, &r6);

                                    prefixlen = 0;
                                    while (m < e && isdigit(*m)) {
                                          prefixlen = prefixlen * 10 + *m++ - '0';
                                    }

                                    if (prefixlen)
                                    {
                                          LOG(3, s, session[s].tunnel,
                                                "   Radius reply contains route for %s/%d\n",
                                                n, prefixlen);
                                          session[s].ipv6route = r6;
                                          session[s].ipv6prefixlen = prefixlen;
                                    }
                              }
                        }
                  }
                  else if (r_code == AccessReject)
                  {
                        LOG(2, s, session[s].tunnel, "   Authentication rejected for %s\n", session[s].user);
                        sessionkill(s, "Authentication rejected");
                        break;
                  }

                  if (!session[s].dns1 && config->default_dns1)
                  {
                        session[s].dns1 = ntohl(config->default_dns1);
                        LOG(3, s, t, "   Sending dns1 = %s\n", fmtaddr(config->default_dns1, 0));
                  }
                  if (!session[s].dns2 && config->default_dns2)
                  {
                        session[s].dns2 = ntohl(config->default_dns2);
                        LOG(3, s, t, "   Sending dns2 = %s\n", fmtaddr(config->default_dns2, 0));
                  }

                  // Valid Session, set it up
                  session[s].unique_id = 0;
                  sessionsetup(s, t);
            }
            else
            {
                        // An ack for a stop or start record.
                  LOG(3, s, t, "   RADIUS accounting ack recv in state %s\n", radius_state(radius[r].state));
                  break;
            }
      } while (0);

      // finished with RADIUS
      radiusclear(r, s);
}

// Send a retry for RADIUS/CHAP message
void radiusretry(uint16_t r)
{
      sessionidt s = radius[r].session;
      tunnelidt t = 0;

      CSTAT(radiusretry);

      if (s) t = session[s].tunnel;

      switch (radius[r].state)
      {
            case RADIUSCHAP:  // sending CHAP down PPP
                  sendchap(s, t);
                  break;
            case RADIUSAUTH:  // sending auth to RADIUS server
            case RADIUSSTART: // sending start accounting to RADIUS server
            case RADIUSSTOP:  // sending stop accounting to RADIUS server
            case RADIUSINTERIM:     // sending interim accounting to RADIUS server
                  radiussend(r, radius[r].state);
                  break;
            default:
            case RADIUSNULL:  // Not in use
            case RADIUSWAIT:  // waiting timeout before available, in case delayed reply from RADIUS server
                  // free up RADIUS task
                  radiusclear(r, s);
                  LOG(3, s, session[s].tunnel, "Freeing up radius session %d\n", r);
                  break;
      }
}

extern int daefd;

void processdae(uint8_t *buf, int len, struct sockaddr_in *addr, int alen, struct in_addr *local)
{
      int i, r_code, r_id, length, attribute_length;
      uint8_t *packet, attribute;
      hasht hash;
      char username[MAXUSER] = "";
      in_addr_t nas = 0;
      in_addr_t ip = 0;
      uint32_t port = 0;
      uint32_t error = 0;
      sessionidt s = 0;
      tunnelidt t;
      int fin = -1;
      int fout = -1;
      uint8_t *avpair[64];
      int avpair_len[sizeof(avpair)/sizeof(*avpair)];
      int avp = 0;
      int auth_only = 0;
      uint8_t *p;

      LOG(3, 0, 0, "DAE request from %s\n", fmtaddr(addr->sin_addr.s_addr, 0));
      LOG_HEX(5, "DAE Request", buf, len);

      if (len < 20 || len < ntohs(*(uint16_t *) (buf + 2)))
      {
            LOG(1, 0, 0, "Duff DAE request length %d\n", len);
            return;
      }

      r_code = buf[0]; // request type
      r_id = buf[1]; // radius indentifier.

      if (r_code != DisconnectRequest && r_code != CoARequest)
      {
            LOG(1, 0, 0, "Unrecognised DAE request %s\n", radius_code(r_code));
            return;
      }

      if (!config->cluster_iam_master)
      {
            master_forward_dae_packet(buf, len, addr->sin_addr.s_addr, addr->sin_port);
            return;
      }

      len = ntohs(*(uint16_t *) (buf + 2));

      LOG(3, 0, 0, "Received DAE %s, id %d\n", radius_code(r_code), r_id);

      // check authenticator
      calc_auth(buf, len, zero, hash);
      if (memcmp(hash, buf + 4, 16) != 0)
      {
            LOG(1, 0, 0, "Incorrect vector in DAE request (wrong secret in radius config?)\n");
            return;
      }

      // unpack attributes
      packet = buf + 20;
      length = len - 20;

      while (length > 0)
      {
            attribute = *packet++;
            attribute_length = *packet++;
            if (attribute_length < 2)
                  break;

            length -= attribute_length;
            attribute_length -= 2;
            switch (attribute)
            {
            case 1: /* username */
                  len = attribute_length < MAXUSER ? attribute_length : MAXUSER - 1;
                  memcpy(username, packet, len);
                  username[len] = 0;
                  LOG(4, 0, 0, "    Received DAE User-Name: %s\n", username);
                  break;

            case 4: /* nas ip address */
                  nas = *(uint32_t *) packet; // net order
                  if (nas != config->bind_address)
                        error = 403; // NAS identification mismatch

                  LOG(4, 0, 0, "    Received DAE NAS-IP-Address: %s\n", fmtaddr(nas, 0));
                  break;

            case 5: /* nas port */
                  port = ntohl(*(uint32_t *) packet);
                  if (port < 1 || port > MAXSESSION)
                        error = 404;

                  LOG(4, 0, 0, "    Received DAE NAS-Port: %u\n", port);
                  break;

            case 6: /* service type */
                  {
                        uint32_t service_type = ntohl(*(uint32_t *) packet);
                        auth_only = service_type == 8; // Authenticate only

                        LOG(4, 0, 0, "    Received DAE Service-Type: %u\n", service_type);
                  }
                  break;

            case 8: /* ip address */
                  ip = *(uint32_t *) packet; // net order
                  LOG(4, 0, 0, "    Received DAE Framed-IP-Address: %s\n", fmtaddr(ip, 0));
                  break;

            case 11: /* filter id */
                  LOG(4, 0, 0, "    Received DAE Filter-Id: %.*s\n", attribute_length, packet);
                  if (!(p = memchr(packet, '.', attribute_length)))
                  {
                        error = 404; // invalid request
                        break;
                  }

                  len = p - packet;
                  i = find_filter((char *) packet, len);
                  if (i < 0 || !*ip_filters[i].name)
                  {
                        error = 404;
                        break;
                  }

                  if (!memcmp(p, ".in", attribute_length - len))
                        fin = i + 1;
                  else if (!memcmp(p, ".out", attribute_length - len))
                        fout = i + 1;
                  else
                        error = 404;

                  break;

            case 26: /* vendor specific */
                  if (attribute_length >= 6
                      && ntohl(*(uint32_t *) packet) == 9   // Cisco
                      && *(packet + 4) == 1           // Cisco-AVPair
                      && *(packet + 5) >= 2)          // length
                  {
                        int len = *(packet + 5) - 2;
                        uint8_t *a = packet + 6;

                        LOG(4, 0, 0, "    Received DAE Cisco-AVPair: %.*s\n", len, a);
                        if (avp < sizeof(avpair)/sizeof(*avpair) - 1)
                        {
                              avpair[avp] = a;
                              avpair_len[avp++] = len;
                        }
                  }
                  break;
            }

            packet += attribute_length;
      }

      if (!error && auth_only)
      {
            if (fin != -1 || fout != -1 || avp)
                  error = 401; // unsupported attribute
            else
                  error = 405; // unsupported service
      }

      if (!error && !(port || ip || *username))
            error = 402; // missing attribute

      // exact match for SID if given
      if (!error && port)
      {
            s = port;
            if (!session[s].opened)
                  error = 503; // not found
      }

      if (!error && ip)
      {
            // find/check session by IP
            i = sessionbyip(ip);
            if (!i || (s && s != i)) // not found or mismatching port
                  error = 503;
            else
                  s = i;
      }

      if (!error && *username)
      {
            if (s)
            {
                  if (strcmp(session[s].user, username))
                        error = 503;
            }
            else if (!(s = sessionbyuser(username)))
                  error = 503;
      }

      t = session[s].tunnel;

      switch (r_code)
      {
      case DisconnectRequest: // Packet of Disconnect/Death
            if (error)
            {
                  r_code = DisconnectNAK;
                  break;
            }

            LOG(3, s, t, "    DAE Disconnect %d (%s)\n", s, session[s].user);
            r_code = DisconnectACK;

            sessionshutdown(s, "Requested by PoD", CDN_ADMIN_DISC, TERM_ADMIN_RESET); // disconnect session
            break;

      case CoARequest: // Change of Authorization
            if (error)
            {
                  r_code = CoANAK;
                  break;
            }

            LOG(3, s, t, "    DAE Change %d (%s)\n", s, session[s].user);
            r_code = CoAACK;
      
            // reset
            {
                  struct param_radius_reset p = { &tunnel[session[s].tunnel], &session[s] };
                  run_plugins(PLUGIN_RADIUS_RESET, &p);
            }

            // apply filters
            if (fin == -1)
                  fin = 0;
            else
                  LOG(3, s, t, "        Filter in %d (%s)\n", fin, ip_filters[fin - 1].name);

            if (fout == -1)
                  fout = 0;
            else
                  LOG(3, s, t, "        Filter out %d (%s)\n", fout, ip_filters[fout - 1].name);

            filter_session(s, fin, fout);

            // process cisco av-pair(s)
            for (i = 0; i < avp; i++)
            {
                  LOG(3, s, t, "        Cisco-AVPair: %.*s\n", avpair_len[i], avpair[i]);
                  handle_avpair(s, avpair[i], avpair_len[i]);
            }

            cluster_send_session(s);
            break;
      }

      // send response
      packet = buf;
      *packet++ = r_code;
      *packet++ = r_id;
      // skip len + auth
      packet += 2 + 16;
      len = packet - buf;

      // add attributes
      if (error)
      {
            // add error cause
            *packet++ = 101;
            *packet++ = 6;
            *(uint32_t *) packet = htonl(error);
            len += 6;
      }

      *((uint16_t *)(buf + 2)) = htons(len);

      // make vector
      calc_auth(buf, len, hash, buf + 4);

      LOG(3, 0, 0, "Sending DAE %s, id=%d\n", radius_code(r_code), r_id);

      // send DAE response
      if (sendtofrom(daefd, buf, len, MSG_DONTWAIT | MSG_NOSIGNAL, (struct sockaddr *) addr, alen, local) < 0)
            LOG(0, 0, 0, "Error sending DAE response packet: %s\n", strerror(errno));
}

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