import from HEAD:

[freeradius.git] / src / lib / radius.c

/*
 * radius.c     Functions to send/receive radius packets.
 *
 * Version:     $Id$
 *
 *   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
 *
 * Copyright 2000-2003  The FreeRADIUS server project
 */

static const char rcsid[] = "$Id$";

#include        "autoconf.h"
#include        "md5.h"

#include        <stdlib.h>

#ifdef HAVE_UNISTD_H
#include        <unistd.h>
#endif

#include        <fcntl.h>
#include        <string.h>
#include        <ctype.h>

#include        "libradius.h"
#ifdef WITH_UDPFROMTO
#include        "udpfromto.h"
#endif

#ifdef HAVE_NETINET_IN_H
#include        <netinet/in.h>
#endif

#include        <sys/socket.h>

#ifdef HAVE_ARPA_INET_H
#include        <arpa/inet.h>
#endif

#ifdef HAVE_MALLOC_H
#include        <malloc.h>
#endif

#ifdef WIN32
#include        <process.h>
#endif

/*
 *  The RFC says 4096 octets max, and most packets are less than 256.
 */
#define MAX_PACKET_LEN 4096

/*
 *      The maximum number of attributes which we allow in an incoming
 *      request.  If there are more attributes than this, the request
 *      is rejected.
 *
 *      This helps to minimize the potential for a DoS, when an
 *      attacker spoofs Access-Request packets, which don't have a
 *      Message-Authenticator attribute.  This means that the packet
 *      is unsigned, and the attacker can use resources on the server,
 *      even if the end request is rejected.
 */
int librad_max_attributes = 0;

typedef struct radius_packet_t {
  uint8_t       code;
  uint8_t       id;
  uint8_t       length[2];
  uint8_t       vector[AUTH_VECTOR_LEN];
  uint8_t       data[1];
} radius_packet_t;

static lrad_randctx lrad_rand_pool;     /* across multiple calls */
static volatile int lrad_rand_index = -1;
static unsigned int salt_offset = 0;

static const char *packet_codes[] = {
  "",
  "Access-Request",
  "Access-Accept",
  "Access-Reject",
  "Accounting-Request",
  "Accounting-Response",
  "Accounting-Status",
  "Password-Request",
  "Password-Accept",
  "Password-Reject",
  "Accounting-Message",
  "Access-Challenge",
  "Status-Server",
  "Status-Client",
  "14",
  "15",
  "16",
  "17",
  "18",
  "19",
  "20",
  "Resource-Free-Request",
  "Resource-Free-Response",
  "Resource-Query-Request",
  "Resource-Query-Response",
  "Alternate-Resource-Reclaim-Request",
  "NAS-Reboot-Request",
  "NAS-Reboot-Response",
  "28",
  "Next-Passcode",
  "New-Pin",
  "Terminate-Session",
  "Password-Expired",
  "Event-Request",
  "Event-Response",
  "35",
  "36",
  "37",
  "38",
  "39",
  "Disconnect-Request",
  "Disconnect-ACK",
  "Disconnect-NAK",
  "CoA-Request",
  "CoA-ACK",
  "CoA-NAK",
  "46",
  "47",
  "48",
  "49",
  "IP-Address-Allocate",
  "IP-Address-Release"
};


#define AUTH_PASS_LEN (AUTH_VECTOR_LEN)
/*************************************************************************
 *
 *      Function: make_secret
 *
 *      Purpose: Build an encrypted secret value to return in a reply
 *               packet.  The secret is hidden by xoring with a MD5 digest
 *               created from the shared secret and the authentication
 *               vector.  We put them into MD5 in the reverse order from
 *               that used when encrypting passwords to RADIUS.
 *
 *************************************************************************/
static void make_secret(uint8_t *digest, const uint8_t *vector,
                        const char *secret, const uint8_t *value)
{
        MD5_CTX context;
        int             i;

        MD5Init(&context);
        MD5Update(&context, vector, AUTH_VECTOR_LEN);
        MD5Update(&context, secret, strlen(secret));
        MD5Final(digest, &context);

        for ( i = 0; i < AUTH_VECTOR_LEN; i++ ) {
                digest[i] ^= value[i];
        }
}

#define MAX_PASS_LEN (128)
static void make_passwd(uint8_t *output, int *outlen,
                        const uint8_t *input, int inlen,
                        const char *secret, const uint8_t *vector)
{
        MD5_CTX context, old;
        uint8_t digest[AUTH_VECTOR_LEN];
        uint8_t passwd[MAX_PASS_LEN];
        int     i, n;
        int     len;

        /*
         *      If the length is zero, round it up.
         */
        len = inlen;
        if (len == 0) {
                len = AUTH_PASS_LEN;
        }
        else if (len > MAX_PASS_LEN) len = MAX_PASS_LEN;

        else if ((len & 0x0f) != 0) {
                len += 0x0f;
                len &= ~0x0f;
        }
        *outlen = len;

        memcpy(passwd, input, len);
        memset(passwd + len, 0, sizeof(passwd) - len);

        MD5Init(&context);
        MD5Update(&context, secret, strlen(secret));
        old = context;

        /*
         *      Do first pass.
         */
        MD5Update(&context, vector, AUTH_PASS_LEN);

        for (n = 0; n < len; n += AUTH_PASS_LEN) {
                if (n > 0) {
                        context = old;
                        MD5Update(&context,
                                       passwd + n - AUTH_PASS_LEN,
                                       AUTH_PASS_LEN);
                }

                MD5Final(digest, &context);
                for (i = 0; i < AUTH_PASS_LEN; i++) {
                        passwd[i + n] ^= digest[i];
                }
        }

        memcpy(output, passwd, len);
}

static void make_tunnel_passwd(uint8_t *output, int *outlen,
                               const uint8_t *input, int inlen, int room,
                               const char *secret, const uint8_t *vector)
{
        MD5_CTX context, old;
        uint8_t digest[AUTH_VECTOR_LEN];
        uint8_t passwd[MAX_STRING_LEN + AUTH_VECTOR_LEN];
        int     i, n;
        int     len;

        /*
         *      Account for 2 bytes of the salt, and round the room
         *      available down to the nearest multiple of 16.  Then,
         *      subtract one from that to account for the length byte,
         *      and the resulting number is the upper bound on the data
         *      to copy.
         *
         *      We could short-cut this calculation just be forcing
         *      inlen to be no more than 239.  It would work for all
         *      VSA's, as we don't pack multiple VSA's into one
         *      attribute.
         *
         *      However, this calculation is more general, if a little
         *      complex.  And it will work in the future for all possible
         *      kinds of weird attribute packing.
         */
        room -= 2;
        room -= (room & 0x0f);
        room--;

        if (inlen > room) inlen = room;

        /*
         *      Length of the encrypted data is password length plus
         *      one byte for the length of the password.
         */
        len = inlen + 1;
        if ((len & 0x0f) != 0) {
                len += 0x0f;
                len &= ~0x0f;
        }
        *outlen = len + 2;      /* account for the salt */

        /*
         *      Copy the password over.
         */
        memcpy(passwd + 3, input, inlen);
        memset(passwd + 3 + inlen, 0, sizeof(passwd) - 3 - inlen);

        /*
         *      Generate salt.  The RFC's say:
         *
         *      The high bit of salt[0] must be set, each salt in a
         *      packet should be unique, and they should be random
         *
         *      So, we set the high bit, add in a counter, and then
         *      add in some CSPRNG data.  should be OK..
         */
        passwd[0] = (0x80 | ( ((salt_offset++) & 0x0f) << 3) |
                     (lrad_rand() & 0x07));
        passwd[1] = lrad_rand();
        passwd[2] = inlen;      /* length of the password string */

        MD5Init(&context);
        MD5Update(&context, secret, strlen(secret));
        old = context;

        MD5Update(&context, vector, AUTH_VECTOR_LEN);
        MD5Update(&context, &passwd[0], 2);

        for (n = 0; n < len; n += AUTH_PASS_LEN) {
                if (n > 0) {
                        context = old;
                        MD5Update(&context,
                                       passwd + 2 + n - AUTH_PASS_LEN,
                                       AUTH_PASS_LEN);
                }

                MD5Final(digest, &context);
                for (i = 0; i < AUTH_PASS_LEN; i++) {
                        passwd[i + 2 + n] ^= digest[i];
                }
        }
        memcpy(output, passwd, len + 2);
}


/*
 *      Parse a data structure into a RADIUS attribute.
 */
int rad_vp2attr(const RADIUS_PACKET *packet, const RADIUS_PACKET *original,
                const char *secret, const VALUE_PAIR *vp, uint8_t *ptr)
{
        int             vendorcode;
        int             offset, len, total_length;
        uint32_t        lvalue;
        uint8_t         *length_ptr, *vsa_length_ptr;
        const uint8_t   *data = NULL;
        uint8_t         array[4];

        vendorcode = total_length = 0;
        length_ptr = vsa_length_ptr = NULL;
        
        /*
         *      For interoperability, always put vendor attributes
         *      into their own VSA.
         */
        if ((vendorcode = VENDOR(vp->attribute)) != 0) {
                /*
                 *      Build a VSA header.
                 */
                *ptr++ = PW_VENDOR_SPECIFIC;
                vsa_length_ptr = ptr;
                *ptr++ = 6;
                lvalue = htonl(vendorcode);
                memcpy(ptr, &lvalue, 4);
                ptr += 4;
                total_length += 6;
                
                if (vendorcode == VENDORPEC_USR) {
                        lvalue = htonl(vp->attribute & 0xFFFF);
                        memcpy(ptr, &lvalue, 4);
                        
                        length_ptr = vsa_length_ptr;
                        
                        total_length += 4;
                        *length_ptr  += 4;
                        ptr          += 4;
                        
                        /*
                         *      We don't have two different lengths.
                         */
                        vsa_length_ptr = NULL;
                        
                } else if (vendorcode == VENDORPEC_LUCENT) {
                        /*
                         *      16-bit attribute, 8-bit length
                         */
                        *ptr++ = ((vp->attribute >> 8) & 0xFF);
                        *ptr++ = (vp->attribute & 0xFF);
                        length_ptr = ptr;
                        *vsa_length_ptr += 3;
                        *ptr++ = 3;
                        total_length += 3;

                } else if (vendorcode == VENDORPEC_STARENT) {
                        /*
                         *      16-bit attribute, 16-bit length
                         *      with the upper 8 bits of the length
                         *      always zero!
                         */
                        *ptr++ = ((vp->attribute >> 8) & 0xFF);
                        *ptr++ = (vp->attribute & 0xFF);
                        *ptr++ = 0;
                        length_ptr = ptr;
                        *vsa_length_ptr += 4;
                        *ptr++ = 4;
                        total_length += 4;
                } else {
                        /*
                         *      All other VSA's are encoded the same
                         *      as RFC attributes.
                         */
                        *vsa_length_ptr += 2;
                        goto rfc;
                }
        } else {
        rfc:
                /*
                 *      All other attributes are encoded as
                 *      per the RFC.
                 */
                *ptr++ = (vp->attribute & 0xFF);
                length_ptr = ptr;
                *ptr++ = 2;
                total_length += 2;
        }

        offset = 0;
        if (vp->flags.has_tag) {
                if (TAG_VALID(vp->flags.tag)) {
                        ptr[0] = vp->flags.tag & 0xff;
                        offset = 1;
            
                } else if (vp->flags.encrypt == FLAG_ENCRYPT_TUNNEL_PASSWORD) {
                        /*
                         *      Tunnel passwords REQUIRE a tag, even
                         *      if don't have a valid tag.
                         */
                        ptr[0] = 0;
                        offset = 1;
                } /* else don't write a tag */
        } /* else the attribute doesn't have a tag */
        
        /*
         *      Set up the default sources for the data.
         */
        data = vp->strvalue;
        len = vp->length;

        /*
         *      Encrypted passwords can't be very long.
         *      This check also ensures that the hashed version
         *      of the password + attribute header fits into one
         *      attribute.
         *
         *      FIXME: Print a warning message if it's too long?
         */
        if (vp->flags.encrypt && (len > MAX_PASS_LEN)) {
                len = MAX_PASS_LEN;
        }

        switch(vp->type) {
        case PW_TYPE_STRING:
        case PW_TYPE_OCTETS:
        case PW_TYPE_IFID:
        case PW_TYPE_IPV6ADDR:
        case PW_TYPE_IPV6PREFIX:
        case PW_TYPE_ABINARY:
                /* nothing more to do */
                break;
                        
        case PW_TYPE_INTEGER:
                len = 4;        /* just in case */
                lvalue = htonl(vp->lvalue);
                memcpy(array, &lvalue, sizeof(lvalue));

                /*
                 *      Perhaps discard the first octet.
                 */
                data = &array[offset];
                len -= offset;
                break;
                        
        case PW_TYPE_IPADDR:
                data = (const uint8_t *) &vp->lvalue;
                len = 4;        /* just in case */
                break;

                /*
                 *  There are no tagged date attributes.
                 */
        case PW_TYPE_DATE:
                lvalue = htonl(vp->lvalue);
                data = (const uint8_t *) &lvalue;
                len = 4;        /* just in case */
                break;

        default:                /* unknown type: ignore it */
                librad_log("ERROR: Unknown attribute type %d", vp->type);
                return -1;
        }

        /*
         *      Bound the data to 255 bytes.
         */
        if (len + offset + total_length > 255) {
                len = 255 - offset - total_length;
        }       

        /*
         *      Encrypt the various password styles
         *
         *      Attributes with encrypted values MUST be less than
         *      128 bytes long.
         */
        switch (vp->flags.encrypt) {
        case FLAG_ENCRYPT_USER_PASSWORD:
                make_passwd(ptr + offset, &len,
                            data, len,
                            secret, packet->vector);
                break;
                
        case FLAG_ENCRYPT_TUNNEL_PASSWORD:
                if (!original) {
                        librad_log("ERROR: No request packet, cannot encrypt %s attribute in the vp.", vp->name);
                        return -1;
                }

                /*
                 *      Check if 255 - offset - total_length is less
                 *      than 18.  If so, we can't fit the data into
                 *      the available space, and we discard the
                 *      attribute.
                 *
                 *      This is ONLY a problem if we have multiple VSA's
                 *      in one Vendor-Specific, though.
                 */
                if ((255 - offset - total_length) < 18) return 0;

                /*
                 *      Can't make the password, suppress it.
                 */
                make_tunnel_passwd(ptr + offset, &len,
                                   data, len, 255 - offset - total_length,
                                   secret, original->vector);
                break;

                /*
                 *      The code above ensures that this attribute
                 *      always fits.
                 */
        case FLAG_ENCRYPT_ASCEND_SECRET:
                make_secret(ptr + offset, packet->vector,
                            secret, data);
                len = AUTH_VECTOR_LEN;
                break;

                
        default:
                /*
                 *      Just copy the data over
                 */
                memcpy(ptr + offset, data, len);
                break;
        } /* switch over encryption flags */

        /*
         *      Account for the tag (if any).
         */
        len += offset;

        /*
         *      RFC 2865 section 5 says that zero-length attributes
         *      MUST NOT be sent.
         */
        if (len == 0) return 0;

        /*
         *      Update the various lengths.
         */
        *length_ptr += len;
        if (vsa_length_ptr) *vsa_length_ptr += len;
        ptr += len;
        total_length += len;

        return total_length;    /* of attribute */
}


/*
 *      Encode a packet.
 */
int rad_encode(RADIUS_PACKET *packet, const RADIUS_PACKET *original,
               const char *secret)
{
        radius_packet_t *hdr;
        uint8_t         *ptr;
        uint16_t        total_length;
        int             len;
        VALUE_PAIR      *reply;
        
        /*
         *      For simplicity in the following logic, we allow
         *      the attributes to "overflow" the 4k maximum
         *      RADIUS packet size, by one attribute.
         *
         *      It's uint32_t, for alignment purposes.
         */
        uint32_t        data[(MAX_PACKET_LEN + 256) / 4];

        /*
         *      Double-check some things based on packet code.
         */
        switch (packet->code) {
        case PW_AUTHENTICATION_ACK:
        case PW_AUTHENTICATION_REJECT:
        case PW_ACCESS_CHALLENGE:
                if (!original) {
                        librad_log("ERROR: Cannot sign response packet without a request packet.");
                        return -1;
                }
                break;
                
                /*
                 *      These packet vectors start off as all zero.
                 */
        case PW_ACCOUNTING_REQUEST:
        case PW_DISCONNECT_REQUEST:
        case PW_COA_REQUEST:
                memset(packet->vector, 0, sizeof(packet->vector));
                break;
                
        default:
                break;
        }
                
        /*
         *      Use memory on the stack, until we know how
         *      large the packet will be.
         */
        hdr = (radius_packet_t *) data;
        
        /*
         *      Build standard header
         */
        hdr->code = packet->code;
        hdr->id = packet->id;
        
        memcpy(hdr->vector, packet->vector, sizeof(hdr->vector));

        total_length = AUTH_HDR_LEN;
        packet->verified = 0;
        
        /*
         *      Load up the configuration values for the user
         */
        ptr = hdr->data;

        /*
         *      FIXME: Loop twice over the reply list.  The first time,
         *      calculate the total length of data.  The second time,
         *      allocate the memory, and fill in the VP's.
         *
         *      Hmm... this may be slower than just doing a small
         *      memcpy.
         */
        
        /*
         *      Loop over the reply attributes for the packet.
         */
        for (reply = packet->vps; reply; reply = reply->next) {
                /*
                 *      Ignore non-wire attributes
                 */
                if ((VENDOR(reply->attribute) == 0) &&
                    ((reply->attribute & 0xFFFF) > 0xff)) {
                        continue;
                }
                
                /*
                 *      Set the Message-Authenticator to the correct
                 *      length and initial value.
                 */
                if (reply->attribute == PW_MESSAGE_AUTHENTICATOR) {
                        reply->length = AUTH_VECTOR_LEN;
                        memset(reply->strvalue, 0, AUTH_VECTOR_LEN);
                        packet->verified = total_length; /* HACK! */
                }
                
                /*
                 *      Print out ONLY the attributes which
                 *      we're sending over the wire, and print
                 *      them out BEFORE they're encrypted.
                 */
                debug_pair(reply);

                len = rad_vp2attr(packet, original, secret, reply, ptr);
                if (len < 0) return -1;

                /*
                 *      Check that the packet is no more than 4k in
                 *      size, AFTER writing the attribute past the 4k
                 *      boundary, but BEFORE deciding to increase the
                 *      size of the packet. Note that the 'data'
                 *      buffer, above, is one attribute longer than
                 *      necessary, in order to permit this overflow.
                 */
                if ((total_length + len) > MAX_PACKET_LEN) {
                        break;
                }

                ptr += len;
                total_length += len;
        } /* done looping over all attributes */
        
        /*
         *      Fill in the rest of the fields, and copy the data over
         *      from the local stack to the newly allocated memory.
         *
         *      Yes, all this 'memcpy' is slow, but it means
         *      that we only allocate the minimum amount of
         *      memory for a request.
         */
        packet->data_len = total_length;
        packet->data = (uint8_t *) malloc(packet->data_len);
        if (!packet->data) {
                librad_log("Out of memory");
                return -1;
        }

        memcpy(packet->data, data, packet->data_len);
        hdr = (radius_packet_t *) packet->data;
        
        total_length = htons(total_length);
        memcpy(hdr->length, &total_length, sizeof(total_length));

        return 0;
}


/*
 *      Sign a previously encoded packet.
 */
int rad_sign(RADIUS_PACKET *packet, const RADIUS_PACKET *original,
             const char *secret)
{
        radius_packet_t *hdr = (radius_packet_t *)packet->data;

        /*
         *      It wasn't assigned an Id, this is bad!
         */
        if (packet->id < 0) {
                librad_log("ERROR: RADIUS packets must be assigned an Id.");
                return -1;
        }

        if (!packet->data || (packet->data_len < AUTH_HDR_LEN) ||
            (packet->verified < 0)) {
                librad_log("ERROR: You must call rad_encode() before rad_sign()");
                return -1;
        }

        /*
         *      If there's a Message-Authenticator, update it
         *      now, BEFORE updating the authentication vector.
         *
         *      This is a hack...
         */
        if (packet->verified > 0) {
                uint8_t calc_auth_vector[AUTH_VECTOR_LEN];
                
                switch (packet->code) {
                case PW_ACCOUNTING_REQUEST:
                case PW_ACCOUNTING_RESPONSE:
                case PW_DISCONNECT_REQUEST:
                case PW_DISCONNECT_ACK:
                case PW_DISCONNECT_NAK:
                case PW_COA_REQUEST:
                case PW_COA_ACK:
                case PW_COA_NAK:
                        memset(hdr->vector, 0, AUTH_VECTOR_LEN);
                        break;

                case PW_AUTHENTICATION_ACK:
                case PW_AUTHENTICATION_REJECT:
                case PW_ACCESS_CHALLENGE:
                        if (!original) {
                                librad_log("ERROR: Cannot sign response packet without a request packet.");
                                return -1;
                        }
                        memcpy(hdr->vector, original->vector,
                               AUTH_VECTOR_LEN);
                        break;

                default:        /* others have vector already set to zero */
                        break;
                        
                }
                
                /*
                 *      Set the authentication vector to zero,
                 *      calculate the signature, and put it
                 *      into the Message-Authenticator
                 *      attribute.
                 */
                lrad_hmac_md5(packet->data, packet->data_len,
                              secret, strlen(secret),
                              calc_auth_vector);
                memcpy(packet->data + packet->verified + 2,
                       calc_auth_vector, AUTH_VECTOR_LEN);
                
                /*
                 *      Copy the original request vector back
                 *      to the raw packet.
                 */
                memcpy(hdr->vector, packet->vector, AUTH_VECTOR_LEN);
        }
        
        /*
         *      Switch over the packet code, deciding how to
         *      sign the packet.
         */
        switch (packet->code) {
                /*
                 *      Request packets are not signed, bur
                 *      have a random authentication vector.
                 */
        case PW_AUTHENTICATION_REQUEST:
        case PW_STATUS_SERVER:
                break;
                
                /*
                 *      Reply packets are signed with the
                 *      authentication vector of the request.
                 */
        default:
                {
                        uint8_t digest[16];
                        
                        MD5_CTX context;
                        MD5Init(&context);
                        MD5Update(&context, packet->data, packet->data_len);
                        MD5Update(&context, secret, strlen(secret));
                        MD5Final(digest, &context);
                        
                        memcpy(hdr->vector, digest, AUTH_VECTOR_LEN);
                        memcpy(packet->vector, digest, AUTH_VECTOR_LEN);
                        break;
                }
        }/* switch over packet codes */

        return 0;
}

/*
 *      Reply to the request.  Also attach
 *      reply attribute value pairs and any user message provided.
 */
int rad_send(RADIUS_PACKET *packet, const RADIUS_PACKET *original,
             const char *secret)
{
        VALUE_PAIR              *reply;
        const char              *what;
        char                    ip_buffer[128];
        struct  sockaddr_in     saremote;
        struct  sockaddr_in     *sa;

        /*
         *      Maybe it's a fake packet.  Don't send it.
         */
        if (!packet || (packet->sockfd < 0)) {
                return 0;
        }

        if ((packet->code > 0) && (packet->code < 52)) {
                what = packet_codes[packet->code];
        } else {
                what = "Reply";
        }

        /*
         *  First time through, allocate room for the packet
         */
        if (!packet->data) {
                DEBUG("Sending %s of id %d to %s port %d\n",
                      what, packet->id,
                      ip_ntoa(ip_buffer, packet->dst_ipaddr),
                      packet->dst_port);
                
                /*
                 *      Encode the packet.
                 */
                if (rad_encode(packet, original, secret) < 0) {
                        return -1;
                }
                
                /*
                 *      Re-sign it, including updating the
                 *      Message-Authenticator.
                 */
                if (rad_sign(packet, original, secret) < 0) {
                        return -1;
                }

                /*
                 *      If packet->data points to data, then we print out
                 *      the VP list again only for debugging.
                 */
        } else if (librad_debug) {
                DEBUG("Re-sending %s of id %d to %s port %d\n", what, packet->id,
                      ip_ntoa(ip_buffer, packet->dst_ipaddr),
                      packet->dst_port);

                for (reply = packet->vps; reply; reply = reply->next) {
                        /* FIXME: ignore attributes > 0xff */
                        debug_pair(reply);
                }
        }

        /*
         *      And send it on it's way.
         */
        sa = (struct sockaddr_in *) &saremote;
        memset ((char *) sa, '\0', sizeof (saremote));
        sa->sin_family = AF_INET;
        sa->sin_addr.s_addr = packet->dst_ipaddr;
        sa->sin_port = htons(packet->dst_port);
#ifndef WITH_UDPFROMTO
        return sendto(packet->sockfd, packet->data, (int)packet->data_len, 0,
                      (struct sockaddr *)&saremote, sizeof(struct sockaddr_in));
#else
        {
                struct sockaddr_in salocal;
                memset ((char *) &salocal, '\0', sizeof (salocal));
                salocal.sin_family = AF_INET;
                salocal.sin_addr.s_addr = packet->src_ipaddr;
                
                return sendfromto(packet->sockfd, packet->data, (int)packet->data_len, 0,
                                  (struct sockaddr *)&salocal,  sizeof(struct sockaddr_in),
                                  (struct sockaddr *)&saremote, sizeof(struct sockaddr_in));
        }
#endif
}


/*
 *      Validates the requesting client NAS.  Calculates the
 *      signature based on the clients private key.
 */
static int calc_acctdigest(RADIUS_PACKET *packet, const char *secret)
{
        u_char          digest[AUTH_VECTOR_LEN];
        MD5_CTX         context;

        /*
         *      Older clients have the authentication vector set to
         *      all zeros. Return `1' in that case.
         */
        memset(digest, 0, sizeof(digest));
        if (memcmp(packet->vector, digest, AUTH_VECTOR_LEN) == 0) {
                packet->verified = 1;
                return 1;
        }

        /*
         *      Zero out the auth_vector in the received packet.
         *      Then append the shared secret to the received packet,
         *      and calculate the MD5 sum. This must be the same
         *      as the original MD5 sum (packet->vector).
         */
        memset(packet->data + 4, 0, AUTH_VECTOR_LEN);

        /*
         *  MD5(packet + secret);
         */
        MD5Init(&context);
        MD5Update(&context, packet->data, packet->data_len);
        MD5Update(&context, secret, strlen(secret));
        MD5Final(digest, &context);

        /*
         *      Return 0 if OK, 2 if not OK.
         */
        packet->verified =
        memcmp(digest, packet->vector, AUTH_VECTOR_LEN) ? 2 : 0;

        return packet->verified;
}

/*
 *      Validates the requesting client NAS.  Calculates the
 *      signature based on the clients private key.
 */
static int calc_replydigest(RADIUS_PACKET *packet, RADIUS_PACKET *original,
                            const char *secret)
{
        uint8_t         calc_digest[AUTH_VECTOR_LEN];
        MD5_CTX         context;

        /*
         *      Very bad!
         */
        if (original == NULL) {
                return 3;
        }

        /*
         *  Copy the original vector in place.
         */
        memcpy(packet->data + 4, original->vector, AUTH_VECTOR_LEN);

        /*
         *  MD5(packet + secret);
         */
        MD5Init(&context);
        MD5Update(&context, packet->data, packet->data_len);
        MD5Update(&context, secret, strlen(secret));
        MD5Final(calc_digest, &context);

        /*
         *  Copy the packet's vector back to the packet.
         */
        memcpy(packet->data + 4, packet->vector, AUTH_VECTOR_LEN);

        /*
         *      Return 0 if OK, 2 if not OK.
         */
        packet->verified =
                memcmp(packet->vector, calc_digest, AUTH_VECTOR_LEN) ? 2 : 0;
        return packet->verified;
}

/*
 *      Receive UDP client requests, and fill in
 *      the basics of a RADIUS_PACKET structure.
 */
RADIUS_PACKET *rad_recv(int fd)
{
        RADIUS_PACKET           *packet;
        struct sockaddr_in      saremote;
        int                     totallen;
        socklen_t               salen;
        uint8_t                 *attr;
        int                     count;
        radius_packet_t         *hdr;
        char                    host_ipaddr[16];
        int                     require_ma = 0;
        int                     seen_ma = 0;
        uint8_t                 data[MAX_PACKET_LEN];
        int                     num_attributes;

        /*
         *      Allocate the new request data structure
         */
        if ((packet = malloc(sizeof(RADIUS_PACKET))) == NULL) {
                librad_log("out of memory");
                return NULL;
        }
        memset(packet, 0, sizeof(RADIUS_PACKET));

        /*
         *      Receive the packet.
         */
        salen = sizeof(saremote);
        memset(&saremote, 0, sizeof(saremote));
#ifndef WITH_UDPFROMTO
        packet->data_len = recvfrom(fd, data, sizeof(data),
                                    0, (struct sockaddr *)&saremote, &salen);
        packet->dst_ipaddr = htonl(INADDR_ANY); /* i.e. unknown */
#else
        {
                socklen_t               salen_local;
                struct sockaddr_in      salocal;
                salen_local = sizeof(salocal);
                memset(&salocal, 0, sizeof(salocal));
                packet->data_len = recvfromto(fd, data, sizeof(data), 0,
                                              (struct sockaddr *)&saremote, &salen,
                                              (struct sockaddr *)&salocal, &salen_local);
                packet->dst_ipaddr = salocal.sin_addr.s_addr;
        }
#endif

        /*
         *      Check for socket errors.
         */
        if (packet->data_len < 0) {
                librad_log("Error receiving packet: %s", strerror(errno));
                free(packet);
                return NULL;
        }

        /*
         *      Fill IP header fields.  We need these for the error
         *      messages which may come later.
         */
        packet->sockfd = fd;
        packet->src_ipaddr = saremote.sin_addr.s_addr;
        packet->src_port = ntohs(saremote.sin_port);

        /*
         *      FIXME: Do even more filtering by only permitting
         *      certain IP's.  The problem is that we don't know
         *      how to do this properly for all possible clients...
         */

        /*
         *      Explicitely set the VP list to empty.
         */
        packet->vps = NULL;

        /*
         *      Check for packets smaller than the packet header.
         *
         *      RFC 2865, Section 3., subsection 'length' says:
         *
         *      "The minimum length is 20 ..."
         */
        if (packet->data_len < AUTH_HDR_LEN) {
                librad_log("WARNING: Malformed RADIUS packet from host %s: too short (received %d < minimum %d)",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           packet->data_len, AUTH_HDR_LEN);
                free(packet);
                return NULL;
        }

        /*
         *      RFC 2865, Section 3., subsection 'length' says:
         *
         *      " ... and maximum length is 4096."
         */
        if (packet->data_len > MAX_PACKET_LEN) {
                librad_log("WARNING: Malformed RADIUS packet from host %s: too long (received %d > maximum %d)",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           packet->data_len, MAX_PACKET_LEN);
                free(packet);
                return NULL;
        }

        /*
         *      Check for packets with mismatched size.
         *      i.e. We've received 128 bytes, and the packet header
         *      says it's 256 bytes long.
         */
        totallen = (data[2] << 8) | data[3];
        hdr = (radius_packet_t *)data;

        /*
         *      Code of 0 is not understood.
         *      Code of 16 or greate is not understood.
         */
        if ((hdr->code == 0) ||
            (hdr->code >= 52)) {
                librad_log("WARNING: Bad RADIUS packet from host %s: unknown packet code %d",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           hdr->code);
                free(packet);
                return NULL;
        }

        /*
         *      Message-Authenticator is required in Status-Server
         *      packets, otherwise they can be trivially forged.
         */
        if (hdr->code == PW_STATUS_SERVER) require_ma = 1;

        /*
         *      Repeat the length checks.  This time, instead of
         *      looking at the data we received, look at the value
         *      of the 'length' field inside of the packet.
         *
         *      Check for packets smaller than the packet header.
         *
         *      RFC 2865, Section 3., subsection 'length' says:
         *
         *      "The minimum length is 20 ..."
         */
        if (totallen < AUTH_HDR_LEN) {
                librad_log("WARNING: Malformed RADIUS packet from host %s: too short (length %d < minimum %d)",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           totallen, AUTH_HDR_LEN);
                free(packet);
                return NULL;
        }

        /*
         *      And again, for the value of the 'length' field.
         *
         *      RFC 2865, Section 3., subsection 'length' says:
         *
         *      " ... and maximum length is 4096."
         */
        if (totallen > MAX_PACKET_LEN) {
                librad_log("WARNING: Malformed RADIUS packet from host %s: too long (length %d > maximum %d)",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           totallen, MAX_PACKET_LEN);
                free(packet);
                return NULL;
        }

        /*
         *      RFC 2865, Section 3., subsection 'length' says:
         *
         *      "If the packet is shorter than the Length field
         *      indicates, it MUST be silently discarded."
         *
         *      i.e. No response to the NAS.
         */
        if (packet->data_len < totallen) {
                librad_log("WARNING: Malformed RADIUS packet from host %s: received %d octets, packet length says %d",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           packet->data_len, totallen);
                free(packet);
                return NULL;
        }

        /*
         *      RFC 2865, Section 3., subsection 'length' says:
         *
         *      "Octets outside the range of the Length field MUST be
         *      treated as padding and ignored on reception."
         */
        if (packet->data_len > totallen) {
                /*
                 *      We're shortening the packet below, but just
                 *      to be paranoid, zero out the extra data.
                 */
                memset(data + totallen, 0, packet->data_len - totallen);
                packet->data_len = totallen;
        }

        /*
         *      Walk through the packet's attributes, ensuring that
         *      they add up EXACTLY to the size of the packet.
         *
         *      If they don't, then the attributes either under-fill
         *      or over-fill the packet.  Any parsing of the packet
         *      is impossible, and will result in unknown side effects.
         *
         *      This would ONLY happen with buggy RADIUS implementations,
         *      or with an intentional attack.  Either way, we do NOT want
         *      to be vulnerable to this problem.
         */
        attr = hdr->data;
        count = totallen - AUTH_HDR_LEN;
        num_attributes = 0;

        while (count > 0) {
                /*
                 *      Attribute number zero is NOT defined.
                 */
                if (attr[0] == 0) {
                        librad_log("WARNING: Malformed RADIUS packet from host %s: Invalid attribute 0",
                                   ip_ntoa(host_ipaddr, packet->src_ipaddr));
                        free(packet);
                        return NULL;
                }

                /*
                 *      Attributes are at LEAST as long as the ID & length
                 *      fields.  Anything shorter is an invalid attribute.
                 */
                if (attr[1] < 2) {
                        librad_log("WARNING: Malformed RADIUS packet from host %s: attribute %d too short",
                                   ip_ntoa(host_ipaddr, packet->src_ipaddr),
                                   attr[0]);
                        free(packet);
                        return NULL;
                }

                /*
                 *      Sanity check the attributes for length.
                 */
                switch (attr[0]) {
                default:        /* don't do anything by default */
                        break;


                        /*
                         *      If there's an EAP-Message, we require
                         *      a Message-Authenticator.
                         */
                case PW_EAP_MESSAGE:
                        require_ma = 1;
                        break;

                case PW_MESSAGE_AUTHENTICATOR:
                        if (attr[1] != 2 + AUTH_VECTOR_LEN) {
                                librad_log("WARNING: Malformed RADIUS packet from host %s: Message-Authenticator has invalid length %d",
                                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                                           attr[1] - 2);
                                free(packet);
                                return NULL;
                        }
                        seen_ma = 1;
                        break;
                }

                /*
                 *      FIXME: Look up the base 255 attributes in the
                 *      dictionary, and switch over their type.  For
                 *      integer/date/ip, the attribute length SHOULD
                 *      be 6.
                 */
                count -= attr[1];       /* grab the attribute length */
                attr += attr[1];
                num_attributes++;       /* seen one more attribute */
        }

        /*
         *      If the attributes add up to a packet, it's allowed.
         *
         *      If not, we complain, and throw the packet away.
         */
        if (count != 0) {
                librad_log("WARNING: Malformed RADIUS packet from host %s: packet attributes do NOT exactly fill the packet",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr));
                free(packet);
                return NULL;
        }

        /*
         *      If we're configured to look for a maximum number of
         *      attributes, and we've seen more than that maximum,
         *      then throw the packet away, as a possible DoS.
         */
        if ((librad_max_attributes > 0) &&
            (num_attributes > librad_max_attributes)) {
                librad_log("WARNING: Possible DoS attack from host %s: Too many attributes in request (received %d, max %d are allowed).",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr),
                           num_attributes, librad_max_attributes);
                free(packet);
                return NULL;
        }

        /*
         *      http://www.freeradius.org/rfc/rfc2869.html#EAP-Message
         *
         *      A packet with an EAP-Message attribute MUST also have
         *      a Message-Authenticator attribute.
         *
         *      A Message-Authenticator all by itself is OK, though.
         *
         *      Similarly, Status-Server packets MUST contain
         *      Message-Authenticator attributes.
         */
        if (require_ma && ! seen_ma) {
                librad_log("WARNING: Insecure packet from host %s:  Packet does not contain required Message-Authenticator attribute",
                           ip_ntoa(host_ipaddr, packet->src_ipaddr));
                free(packet);
                return NULL;
        }

        if (librad_debug) {
                if ((hdr->code > 0) && (hdr->code < 52)) {
                        printf("rad_recv: %s packet from host %s:%d",
                               packet_codes[hdr->code],
                               ip_ntoa(host_ipaddr, packet->src_ipaddr), packet->src_port);
                } else {
                        printf("rad_recv: Packet from host %s:%d code=%d",
                               ip_ntoa(host_ipaddr, packet->src_ipaddr), packet->src_port,
                               hdr->code);
                }
                printf(", id=%d, length=%d\n", hdr->id, totallen);
        }

        /*
         *      Fill RADIUS header fields
         */
        packet->code = hdr->code;
        packet->id = hdr->id;
        memcpy(packet->vector, hdr->vector, AUTH_VECTOR_LEN);

        /*
         *  Now that we've sanity checked the packet, we can allocate
         *  memory for it, and copy the data from the local area to
         *  the packet buffer.
         */
        if ((packet->data = malloc(packet->data_len)) == NULL) {
          free(packet);
          librad_log("out of memory");
          return NULL;
        }
        memcpy(packet->data, data, packet->data_len);

        return packet;
}


/*
 *      Verify the signature of a packet.
 */
int rad_verify(RADIUS_PACKET *packet, RADIUS_PACKET *original,
               const char *secret)
{
        uint8_t                 *ptr;
        int                     length;
        int                     attrlen;

        if (!packet || !packet->data) return -1;

        /*
         *      Before we allocate memory for the attributes, do more
         *      sanity checking.
         */
        ptr = packet->data + AUTH_HDR_LEN;
        length = packet->data_len - AUTH_HDR_LEN;
        while (length > 0) {
                uint8_t msg_auth_vector[AUTH_VECTOR_LEN];
                uint8_t calc_auth_vector[AUTH_VECTOR_LEN];

                attrlen = ptr[1];

                switch (ptr[0]) {
                default:        /* don't do anything. */
                        break;

                        /*
                         *      Note that more than one Message-Authenticator
                         *      attribute is invalid.
                         */
                case PW_MESSAGE_AUTHENTICATOR:
                        memcpy(msg_auth_vector, &ptr[2], sizeof(msg_auth_vector));
                        memset(&ptr[2], 0, AUTH_VECTOR_LEN);

                        switch (packet->code) {
                        default:
                                break;

                        case PW_ACCOUNTING_REQUEST:
                        case PW_ACCOUNTING_RESPONSE:
                        case PW_DISCONNECT_REQUEST:
                        case PW_DISCONNECT_ACK:
                        case PW_DISCONNECT_NAK:
                        case PW_COA_REQUEST:
                        case PW_COA_ACK:
                        case PW_COA_NAK:
                                memset(packet->data + 4, 0, AUTH_VECTOR_LEN);
                                break;

                        case PW_AUTHENTICATION_ACK:
                        case PW_AUTHENTICATION_REJECT:
                        case PW_ACCESS_CHALLENGE:
                                if (!original) {
                                        librad_log("ERROR: Cannot validate Message-Authenticator in response packet without a request packet.");
                                        return -1;
                                }
                                memcpy(packet->data + 4, original->vector, AUTH_VECTOR_LEN);
                                break;
                        }

                        lrad_hmac_md5(packet->data, packet->data_len,
                                      secret, strlen(secret), calc_auth_vector);
                        if (memcmp(calc_auth_vector, msg_auth_vector,
                                   sizeof(calc_auth_vector)) != 0) {
                                char buffer[32];
                                librad_log("Received packet from %s with invalid Message-Authenticator!  (Shared secret is incorrect.)",
                                           ip_ntoa(buffer, packet->src_ipaddr));
                                /* Silently drop packet, according to RFC 3579 */
                                return -2;
                        } /* else the message authenticator was good */

                        /*
                         *      Reinitialize Authenticators.
                         */
                        memcpy(&ptr[2], msg_auth_vector, AUTH_VECTOR_LEN);
                        memcpy(packet->data + 4, packet->vector, AUTH_VECTOR_LEN);
                        break;
                } /* switch over the attributes */

                ptr += attrlen;
                length -= attrlen;
        } /* loop over the packet, sanity checking the attributes */

        /*
         *      Calculate and/or verify digest.
         */
        switch(packet->code) {
                int rcode;

                case PW_AUTHENTICATION_REQUEST:
                case PW_STATUS_SERVER:
                case PW_DISCONNECT_REQUEST:
                        /*
                         *      The authentication vector is random
                         *      nonsense, invented by the client.
                         */
                        break;

                case PW_ACCOUNTING_REQUEST:
                        if (calc_acctdigest(packet, secret) > 1) {
                                char buffer[32];
                                librad_log("Received Accounting-Request packet "
                                           "from %s with invalid signature!  (Shared secret is incorrect.)",
                                           ip_ntoa(buffer, packet->src_ipaddr));
                                return -1;
                        }
                        break;

                        /* Verify the reply digest */
                case PW_AUTHENTICATION_ACK:
                case PW_AUTHENTICATION_REJECT:
                case PW_ACCESS_CHALLENGE:
                case PW_ACCOUNTING_RESPONSE:
                        rcode = calc_replydigest(packet, original, secret);
                        if (rcode > 1) {
                                char buffer[32];
                                librad_log("Received %s packet "
                                           "from client %s port %d with invalid signature (err=%d)!  (Shared secret is incorrect.)",
                                           packet_codes[packet->code],
                                           ip_ntoa(buffer, packet->src_ipaddr),
                                           packet->src_port,
                                           rcode);
                                return -1;
                        }
                  break;
        }

        return 0;
}


/*
 *      Parse a RADIUS attribute into a data structure.
 */
static VALUE_PAIR *rad_attr2vp(const RADIUS_PACKET *packet, const RADIUS_PACKET *original,
                        const char *secret, int attribute, int length,
                        const uint8_t *data)
{
        int offset = 0;
        VALUE_PAIR *vp;

        if ((vp = paircreate(attribute, PW_TYPE_OCTETS)) == NULL) {
                return NULL;
        }
        
        /*
         *      If length is greater than 253, something is SERIOUSLY
         *      wrong.
         */
        if (length > 253) length = 253; /* paranoia (pair-anoia?) */

        vp->length = length;
        vp->operator = T_OP_EQ;
        vp->next = NULL;

        /*
         *      Handle tags.
         */
        if (vp->flags.has_tag) {
                if (TAG_VALID(data[0]) ||
                    (vp->flags.encrypt == FLAG_ENCRYPT_TUNNEL_PASSWORD)) {
                        /*
                         *      Tunnel passwords REQUIRE a tag, even
                         *      if don't have a valid tag.
                         */
                        vp->flags.tag = data[0];

                        if ((vp->type == PW_TYPE_STRING) ||
                            (vp->type == PW_TYPE_OCTETS)) offset = 1;
                }
        }

        /*
         *      Copy the data to be decrypted
         */
        memcpy(&vp->strvalue[0], data + offset, length - offset);
        vp->length -= offset;

        /*
         *      Decrypt the attribute.
         */
        switch (vp->flags.encrypt) {
                /*
                 *  User-Password
                 */
        case FLAG_ENCRYPT_USER_PASSWORD:
                if (original) {
                        rad_pwdecode((char *)vp->strvalue,
                                     vp->length, secret,
                                     original->vector);
                } else {
                        rad_pwdecode((char *)vp->strvalue,
                                     vp->length, secret,
                                     packet->vector);
                }
                if (vp->attribute == PW_USER_PASSWORD) {
                        vp->length = strlen(vp->strvalue);
                }
                break;
                
                /*
                 *      Tunnel-Password's may go ONLY
                 *      in response packets.
                 */
        case FLAG_ENCRYPT_TUNNEL_PASSWORD:
                if (!original) goto raw;
                
                if (rad_tunnel_pwdecode(vp->strvalue, &vp->length,
                                        secret, original->vector) < 0) {
                        goto raw;
                }
                break;
                
                /*
                 *  Ascend-Send-Secret
                 *  Ascend-Receive-Secret
                 */
        case FLAG_ENCRYPT_ASCEND_SECRET:
                if (!original) {
                        goto raw;
                } else {
                        uint8_t my_digest[AUTH_VECTOR_LEN];
                        make_secret(my_digest,
                                    original->vector,
                                    secret, data);
                        memcpy(vp->strvalue, my_digest,
                               AUTH_VECTOR_LEN );
                        vp->strvalue[AUTH_VECTOR_LEN] = '\0';
                        vp->length = strlen(vp->strvalue);
                }
                break;

        default:
                break;
        } /* switch over encryption flags */


        switch (vp->type) {
        case PW_TYPE_STRING:
        case PW_TYPE_OCTETS:
        case PW_TYPE_ABINARY:
                /* nothing more to do */
                break;

        case PW_TYPE_INTEGER:
                if (vp->length != 4) goto raw;

                memcpy(&vp->lvalue, vp->strvalue, 4);
                vp->lvalue = ntohl(vp->lvalue);

                if (vp->flags.has_tag) vp->lvalue &= 0x00ffffff;

                /*
                 *      Try to get named VALUEs
                 */
                {
                        DICT_VALUE *dval;
                        dval = dict_valbyattr(vp->attribute,
                                              vp->lvalue);
                        if (dval) {
                                strNcpy(vp->strvalue,
                                        dval->name,
                                        sizeof(vp->strvalue));
                        }
                }
                break;

        case PW_TYPE_DATE:
                if (vp->length != 4) goto raw;

                memcpy(&vp->lvalue, vp->strvalue, 4);
                vp->lvalue = ntohl(vp->lvalue);
                break;

                /*
                 *      IPv4 address. Keep it in network byte order in
                 *      vp->lvalue and put ASCII IP address in standard
                 *      dot notation into vp->strvalue.
                 */
        case PW_TYPE_IPADDR:
                if (vp->length != 4) goto raw;

                memcpy(&vp->lvalue, vp->strvalue, 4);
                ip_ntoa(vp->strvalue, vp->lvalue);
                break;

                /*
                 *      IPv6 interface ID is 8 octets long.
                 */
        case PW_TYPE_IFID:
                if (vp->length != 8) goto raw;
                /* vp->vp_ifid == vp->strvalue */
                break;
                
                /*
                 *      IPv6 addresses are 16 octets long
                 */
        case PW_TYPE_IPV6ADDR:
                if (vp->length != 16) goto raw;
                /* vp->vp_ipv6addr == vp->strvalue */
                break;
                
                /*
                 *      IPv6 prefixes are 2 to 18 octets long.
                 *
                 *      RFC 3162: The first octet is unused.
                 *      The second is the length of the prefix
                 *      the rest are the prefix data.
                 *
                 *      The prefix length can have value 0 to 128.
                 */
        case PW_TYPE_IPV6PREFIX:
                if (vp->length < 2 || vp->length > 18) goto raw;
                if (vp->strvalue[1] > 128) goto raw;

                /*
                 *      FIXME: double-check that
                 *      (vp->strvalue[1] >> 3) matches vp->length + 2
                 */
                if (vp->length < 18) {
                        memset(vp->strvalue + vp->length, 0,
                               18 - vp->length);
                }
                break;

        default:
        raw:
                vp->type = PW_TYPE_OCTETS;
                vp->length = length;
                memcpy(vp->strvalue, data, length);
                

                /*
                 *      Ensure there's no encryption or tag stuff,
                 *      we just pass the attribute as-is.
                 */
                memset(&vp->flags, 0, sizeof(vp->flags));
        }

        return vp;
}


/*
 *      Calculate/check digest, and decode radius attributes.
 */
int rad_decode(RADIUS_PACKET *packet, RADIUS_PACKET *original,
               const char *secret)
{
        uint32_t                lvalue;
        uint32_t                vendorcode;
        VALUE_PAIR              **tail;
        VALUE_PAIR              *pair;
        uint8_t                 *ptr;
        int                     packet_length;
        int                     attribute;
        int                     attrlen;
        int                     vendorlen;
        radius_packet_t         *hdr;
        int                     vsa_tlen, vsa_llen;
        DICT_VENDOR             *dv = NULL;

        /*
         *      Extract attribute-value pairs
         */
        hdr = (radius_packet_t *)packet->data;
        ptr = hdr->data;
        packet_length = packet->data_len - AUTH_HDR_LEN;

        /*
         *      There may be VP's already in the packet.  Don't
         *      destroy them.
         */
        for (tail = &packet->vps; *tail != NULL; tail = &((*tail)->next)) {
                /* nothing */
        }

        vendorcode = 0;
        vendorlen  = 0;
        vsa_tlen = vsa_llen = 1;

        /*
         *      We have to read at least two bytes.
         *
         *      rad_recv() above ensures that this is OK.
         */
        while (packet_length > 0) {
                attribute = -1;
                attrlen = -1;

                /*
                 *      Normal attribute, handle it like normal.
                 */
                if (vendorcode == 0) {
                        /*
                         *      No room to read attr/length,
                         *      or bad attribute, or attribute is
                         *      too short, or attribute is too long,
                         *      stop processing the packet.
                         */
                        if ((packet_length < 2) ||
                            (ptr[0] == 0) ||  (ptr[1] < 2) ||
                            (ptr[1] > packet_length)) break;

                        attribute = *ptr++;
                        attrlen   = *ptr++;

                        attrlen -= 2;
                        packet_length  -= 2;

                        if (attribute != PW_VENDOR_SPECIFIC) goto create_pair;
                        
                        /*
                         *      No vendor code, or ONLY vendor code.
                         */
                        if (attrlen <= 4) goto create_pair;

                        vendorlen = 0;
                }
                
                /*
                 *      Handle Vendor-Specific
                 */
                if (vendorlen == 0) {
                        uint8_t *subptr;
                        int sublen;
                        int myvendor;
                        
                        /*
                         *      attrlen was checked above.
                         */
                        memcpy(&lvalue, ptr, 4);
                        myvendor = ntohl(lvalue);

                        /*
                         *      Zero isn't allowed.
                         */
                        if (myvendor == 0) goto create_pair;
                        
                        /*
                         *      This is an implementation issue.
                         *      We currently pack vendor into the upper
                         *      16 bits of a 32-bit attribute number,
                         *      so we can't handle vendor numbers larger
                         *      than 16 bits.
                         */
                        if (myvendor > 65535) goto create_pair;
                        
                        vsa_tlen = vsa_llen = 1;
                        dv = dict_vendorbyvalue(myvendor);
                        if (dv) {
                                vsa_tlen = dv->type;
                                vsa_llen = dv->length;
                        }
                        
                        /*
                         *      Sweep through the list of VSA's,
                         *      seeing if they exactly fill the
                         *      outer Vendor-Specific attribute.
                         *
                         *      If not, create a raw Vendor-Specific.
                         */
                        subptr = ptr + 4;
                        sublen = attrlen - 4;

                        /*
                         *      See if we can parse it.
                         */
                        do {
                                int myattr = 0;

                                /*
                                 *      Don't have a type, it's bad.
                                 */
                                if (sublen < vsa_tlen) goto create_pair;
                                
                                /*
                                 *      Ensure that the attribute number
                                 *      is OK.
                                 */
                                switch (vsa_tlen) {
                                case 1:
                                        myattr = subptr[0];
                                        break;
                                        
                                case 2:
                                        myattr = (subptr[0] << 8) | subptr[1];
                                        break;
                                        
                                case 4:
                                        if ((subptr[0] != 0) ||
                                            (subptr[1] != 0)) goto create_pair;
                                        
                                        myattr = (subptr[2] << 8) | subptr[3];
                                        break;
                                        
                                        /*
                                         *      Our dictionary is broken.
                                         */
                                default:
                                        goto create_pair;
                                }
                                
                                /*
                                 *      Not enough room for one more
                                 *      attribute.  Die!
                                 */
                                if (sublen < vsa_tlen + vsa_llen) goto create_pair;
                                switch (vsa_llen) {
                                case 0:
                                        attribute = (myvendor << 16) | myattr;
                                        ptr += 4 + vsa_tlen;
                                        attrlen -= (4 + vsa_tlen);
                                        packet_length -= 4 + vsa_tlen;
                                        goto create_pair;

                                case 1:
                                        if (subptr[vsa_tlen] < (vsa_tlen + vsa_llen))
                                                goto create_pair;

                                        if (subptr[vsa_tlen] > sublen)
                                                goto create_pair;
                                        sublen -= subptr[vsa_tlen];
                                        subptr += subptr[vsa_tlen];
                                        break;

                                case 2:
                                        if (subptr[vsa_tlen] != 0) goto create_pair;
                                        if (subptr[vsa_tlen + 1] < (vsa_tlen + vsa_llen))
                                                goto create_pair;
                                        if (subptr[vsa_tlen + 1] > sublen)
                                                goto create_pair;
                                        sublen -= subptr[vsa_tlen + 1];
                                        subptr += subptr[vsa_tlen + 1];
                                        break;

                                        /*
                                         *      Our dictionaries are
                                         *      broken.
                                         */
                                default:
                                        goto create_pair;
                                }
                        } while (sublen > 0);

                        vendorcode = myvendor;
                        vendorlen = attrlen - 4;
                        packet_length -= 4;

                        ptr += 4;
                }

                /*
                 *      attrlen is the length of this attribute.
                 *      total_len is the length of the encompassing
                 *      attribute.
                 */
                switch (vsa_tlen) {
                case 1:
                        attribute = ptr[0];
                        break;
                        
                case 2:
                        attribute = (ptr[0] << 8) | ptr[1];
                        break;

                default:        /* can't hit this. */
                        return -1;
                }
                attribute |= (vendorcode << 16);
                ptr += vsa_tlen;

                switch (vsa_llen) {
                case 1:
                        attrlen = ptr[0] - (vsa_tlen + vsa_llen);
                        break;
                        
                case 2:
                        attrlen = ptr[1] - (vsa_tlen + vsa_llen);
                        break;

                default:        /* can't hit this. */
                        return -1;
                }
                ptr += vsa_llen;
                vendorlen -= vsa_tlen + vsa_llen + attrlen;
                if (vendorlen == 0) vendorcode = 0;
                packet_length -= (vsa_tlen + vsa_llen);

                /*
                 *      Create the attribute, setting the default type
                 *      to 'octects'.  If the type in the dictionary
                 *      is different, then the dictionary type will
                 *      over-ride this one.
                 */
        create_pair:
                pair = rad_attr2vp(packet, original, secret,
                                 attribute, attrlen, ptr);
                if (!pair) {
                        pairfree(&packet->vps);
                        librad_log("out of memory");
                        return -1;
                }

                debug_pair(pair);
                *tail = pair;
                tail = &pair->next;

                ptr += attrlen;
                packet_length -= attrlen;
        }

        /*
         *      Merge information from the outside world into our
         *      random pool.
         */
        lrad_rand_seed(packet->data, AUTH_HDR_LEN);
          
        return 0;
}


/*
 *      Encode password.
 *
 *      We assume that the passwd buffer passed is big enough.
 *      RFC2138 says the password is max 128 chars, so the size
 *      of the passwd buffer must be at least 129 characters.
 *      Preferably it's just MAX_STRING_LEN.
 *
 *      int *pwlen is updated to the new length of the encrypted
 *      password - a multiple of 16 bytes.
 */
int rad_pwencode(char *passwd, int *pwlen, const char *secret,
                 const char *vector)
{
        uint8_t buffer[AUTH_VECTOR_LEN + MAX_STRING_LEN + 1];
        char    digest[AUTH_VECTOR_LEN];
        int     i, n, secretlen;
        int     len;

        /*
         *      Pad password to multiple of AUTH_PASS_LEN bytes.
         */
        len = *pwlen;
        if (len > 128) len = 128;
        *pwlen = len;
        if (len % AUTH_PASS_LEN != 0) {
                n = AUTH_PASS_LEN - (len % AUTH_PASS_LEN);
                for (i = len; n > 0; n--, i++)
                        passwd[i] = 0;
                len = *pwlen = i;

        } else if (len == 0) {
                memset(passwd, 0, AUTH_PASS_LEN);
                *pwlen = len = AUTH_PASS_LEN;
        }

        /*
         *      Use the secret to setup the decryption digest
         */
        secretlen = strlen(secret);
        memcpy(buffer, secret, secretlen);
        memcpy(buffer + secretlen, vector, AUTH_VECTOR_LEN);
        librad_md5_calc((u_char *)digest, buffer, secretlen + AUTH_VECTOR_LEN);

        /*
         *      Now we can encode the password *in place*
         */
        for (i = 0; i < AUTH_PASS_LEN; i++)
                passwd[i] ^= digest[i];

        if (len <= AUTH_PASS_LEN) return 0;

        /*
         *      Length > AUTH_PASS_LEN, so we need to use the extended
         *      algorithm.
         */
        for (n = 0; n < 128 && n <= (len - AUTH_PASS_LEN); n += AUTH_PASS_LEN) {
                memcpy(buffer + secretlen, passwd + n, AUTH_PASS_LEN);
                librad_md5_calc((u_char *)digest, buffer, secretlen + AUTH_PASS_LEN);
                for (i = 0; i < AUTH_PASS_LEN; i++)
                        passwd[i + n + AUTH_PASS_LEN] ^= digest[i];
        }

        return 0;
}

/*
 *      Decode password.
 */
int rad_pwdecode(char *passwd, int pwlen, const char *secret,
                 const char *vector)
{
        uint8_t buffer[AUTH_VECTOR_LEN + MAX_STRING_LEN + 1];
        char    digest[AUTH_VECTOR_LEN];
        char    r[AUTH_VECTOR_LEN];
        char    *s;
        int     i, n, secretlen;
        int     rlen;

        /*
         *      Use the secret to setup the decryption digest
         */
        secretlen = strlen(secret);
        memcpy(buffer, secret, secretlen);
        memcpy(buffer + secretlen, vector, AUTH_VECTOR_LEN);
        librad_md5_calc((u_char *)digest, buffer, secretlen + AUTH_VECTOR_LEN);

        /*
         *      Now we can decode the password *in place*
         */
        memcpy(r, passwd, AUTH_PASS_LEN);
        for (i = 0; i < AUTH_PASS_LEN && i < pwlen; i++)
                passwd[i] ^= digest[i];

        if (pwlen <= AUTH_PASS_LEN) {
                passwd[pwlen+1] = 0;
                return pwlen;
        }

        /*
         *      Length > AUTH_PASS_LEN, so we need to use the extended
         *      algorithm.
         */
        rlen = ((pwlen - 1) / AUTH_PASS_LEN) * AUTH_PASS_LEN;

        for (n = rlen; n > 0; n -= AUTH_PASS_LEN ) {
                s = (n == AUTH_PASS_LEN) ? r : (passwd + n - AUTH_PASS_LEN);
                memcpy(buffer + secretlen, s, AUTH_PASS_LEN);
                librad_md5_calc((u_char *)digest, buffer, secretlen + AUTH_PASS_LEN);
                for (i = 0; i < AUTH_PASS_LEN && (i + n) < pwlen; i++)
                        passwd[i + n] ^= digest[i];
        }
        passwd[pwlen] = 0;

        return pwlen;
}


/*
 *      Encode Tunnel-Password attributes when sending them out on the wire.
 *
 *      int *pwlen is updated to the new length of the encrypted
 *      password - a multiple of 16 bytes.
 *
 *      This is per RFC-2868 which adds a two char SALT to the initial intermediate
 *      value MD5 hash.
 */
int rad_tunnel_pwencode(char *passwd, int *pwlen, const char *secret,
                        const char *vector)
{
        uint8_t buffer[AUTH_VECTOR_LEN + MAX_STRING_LEN + 3];
        unsigned char   digest[AUTH_VECTOR_LEN];
        char*   salt;
        int     i, n, secretlen;
        unsigned len, n2;

        len = *pwlen;

        if (len > 127) len = 127;
        /*
         * Shift the password 3 positions right to place a salt and original
         * length, tag will be added automatically on packet send
         */
        for (n=len ; n>=0 ; n--) passwd[n+3] = passwd[n];
        salt = passwd;
        passwd += 2;
        /*
         * save original password length as first password character;
         */
        *passwd = len;
        len += 1;


        /*
         *      Generate salt.  The RFC's say:
         *
         *      The high bit of salt[0] must be set, each salt in a
         *      packet should be unique, and they should be random
         *
         *      So, we set the high bit, add in a counter, and then
         *      add in some CSPRNG data.  should be OK..
         */
        salt[0] = (0x80 | ( ((salt_offset++) & 0x0f) << 3) |
                   (lrad_rand() & 0x07));
        salt[1] = lrad_rand();

        /*
         *      Padd password to multiple of AUTH_PASS_LEN bytes.
         */
        n = len % AUTH_PASS_LEN;
        if (n) {
                n = AUTH_PASS_LEN - n;
                for (; n > 0; n--, len++)
                        passwd[len] = 0;
        }
        /* set new password length */
        *pwlen = len + 2;

        /*
         *      Use the secret to setup the decryption digest
         */
        secretlen = strlen(secret);
        memcpy(buffer, secret, secretlen);

        for (n2 = 0; n2 < len; n2+=AUTH_PASS_LEN) {
                if (!n2) {
                        memcpy(buffer + secretlen, vector, AUTH_VECTOR_LEN);
                        memcpy(buffer + secretlen + AUTH_VECTOR_LEN, salt, 2);
                        librad_md5_calc(digest, buffer, secretlen + AUTH_VECTOR_LEN + 2);
                } else {
                        memcpy(buffer + secretlen, passwd + n2 - AUTH_PASS_LEN, AUTH_PASS_LEN);
                        librad_md5_calc(digest, buffer, secretlen + AUTH_PASS_LEN);
                }

                for (i = 0; i < AUTH_PASS_LEN; i++) {
                        passwd[i + n2] ^= digest[i];
                }
        }
        passwd[n2] = 0;
        return 0;
}

/*
 *      Decode Tunnel-Password encrypted attributes.
 *
 *      Defined in RFC-2868, this uses a two char SALT along with the
 *      initial intermediate value, to differentiate it from the
 *      above.
 */
int rad_tunnel_pwdecode(uint8_t *passwd, int *pwlen, const char *secret,
                        const char *vector)
{
        uint8_t         buffer[AUTH_VECTOR_LEN + MAX_STRING_LEN + 3];
        uint8_t         digest[AUTH_VECTOR_LEN];
        uint8_t         decrypted[MAX_STRING_LEN + 1];
        int             secretlen;
        unsigned        i, n, len;

        len = *pwlen;

        /*
         *      We need at least a salt.
         */
        if (len < 2) {
                librad_log("tunnel password is too short");
                return -1;
        }

        /*
         *      There's a salt, but no password.  Or, there's a salt
         *      and a 'data_len' octet.  It's wrong, but at least we
         *      can figure out what it means: the password is empty.
         *
         *      Note that this means we ignore the 'data_len' field,
         *      if the attribute length tells us that there's no
         *      more data.  So the 'data_len' field may be wrong,
         *      but that's ok...
         */
        if (len <= 3) {
                passwd[0] = 0;
                *pwlen = 0;
                return 0;
        }

        len -= 2;               /* discount the salt */

        /*
         *      Use the secret to setup the decryption digest
         */
        secretlen = strlen(secret);

        /*
         *      Set up the initial key:
         *
         *       b(1) = MD5(secret + vector + salt)
         */
        memcpy(buffer, secret, secretlen);
        memcpy(buffer + secretlen, vector, AUTH_VECTOR_LEN);
        memcpy(buffer + secretlen + AUTH_VECTOR_LEN, passwd, 2);
        librad_md5_calc(digest, buffer, secretlen + AUTH_VECTOR_LEN + 2);

        /*
         *      A quick check: decrypt the first octet of the password,
         *      which is the 'data_len' field.  Ensure it's sane.
         *
         *      'n' doesn't include the 'data_len' octet
         *      'len' does.
         */
        n = passwd[2] ^ digest[0];
        if (n >= len) {
                librad_log("tunnel password is too long for the attribute");
                return -1;
        }

        /*
         *      Loop over the data, decrypting it, and generating
         *      the key for the next round of decryption.
         */
        for (n = 0; n < len; n += AUTH_PASS_LEN) {
                for (i = 0; i < AUTH_PASS_LEN; i++) {
                        decrypted[n + i] = passwd[n + i + 2] ^ digest[i];

                        /*
                         *      Encrypted password may not be aligned
                         *      on 16 octets, so we catch that here...
                         */
                        if ((n + i) == len) break;
                }

                /*
                 *      Update the digest, based on
                 *
                 *      b(n) = MD5(secret + cleartext(n-1)
                 *
                 *      but only if there's more data...
                 */
                memcpy(buffer + secretlen, passwd + n + 2, AUTH_PASS_LEN);
                librad_md5_calc(digest, buffer, secretlen + AUTH_PASS_LEN);
        }

        /*
         *      We've already validated the length of the decrypted
         *      password.  Copy it back to the caller.
         */
        memcpy(passwd, decrypted + 1, decrypted[0]);
        passwd[decrypted[0]] = 0;
        *pwlen = decrypted[0];

        return decrypted[0];
}

/*
 *      Encode a CHAP password
 *
 *      FIXME: might not work with Ascend because
 *      we use vp->length, and Ascend gear likes
 *      to send an extra '\0' in the string!
 */
int rad_chap_encode(RADIUS_PACKET *packet, char *output, int id,
                    VALUE_PAIR *password)
{
        int             i;
        char            *ptr;
        char            string[MAX_STRING_LEN * 2 + 1];
        VALUE_PAIR      *challenge;

        /*
         *      Sanity check the input parameters
         */
        if ((packet == NULL) || (password == NULL)) {
                return -1;
        }

        /*
         *      Note that the password VP can be EITHER
         *      a User-Password attribute (from a check-item list),
         *      or a CHAP-Password attribute (the client asking
         *      the library to encode it).
         */

        i = 0;
        ptr = string;
        *ptr++ = id;

        i++;
        memcpy(ptr, password->strvalue, password->length);
        ptr += password->length;
        i += password->length;

        /*
         *      Use Chap-Challenge pair if present,
         *      Request-Authenticator otherwise.
         */
        challenge = pairfind(packet->vps, PW_CHAP_CHALLENGE);
        if (challenge) {
                memcpy(ptr, challenge->strvalue, challenge->length);
                i += challenge->length;
        } else {
                memcpy(ptr, packet->vector, AUTH_VECTOR_LEN);
                i += AUTH_VECTOR_LEN;
        }

        *output = id;
        librad_md5_calc((u_char *)output + 1, (u_char *)string, i);

        return 0;
}


/*
 *      Seed the random number generator.
 *
 *      May be called any number of times.
 */
void lrad_rand_seed(const void *data, size_t size)
{
        uint32_t hash;

        /*
         *      Ensure that the pool is initialized.
         */
        if (lrad_rand_index < 0) {
                int fd;
                
                memset(&lrad_rand_pool, 0, sizeof(lrad_rand_pool));

                fd = open("/dev/urandom", O_RDONLY);
                if (fd >= 0) {
                        size_t total;
                        ssize_t this;

                        total = this = 0;
                        while (total < sizeof(lrad_rand_pool.randrsl)) {
                                this = read(fd, lrad_rand_pool.randrsl,
                                            sizeof(lrad_rand_pool.randrsl) - total);
                                if ((this < 0) && (errno != EINTR)) break;
                                if (this > 0) total += this;
                        }
                        close(fd);
                } else {
                        lrad_rand_pool.randrsl[0] = fd;
                        lrad_rand_pool.randrsl[1] = time(NULL);
                        lrad_rand_pool.randrsl[2] = errno;
                }

                lrad_randinit(&lrad_rand_pool, 1);
                lrad_rand_index = 0;
        }

        if (!data) return;

        /*
         *      Hash the user data
         */
        hash = lrad_hash(data, size);
        
        lrad_rand_pool.randrsl[lrad_rand_index & 0xff] ^= hash;
        lrad_rand_index++;
        lrad_rand_index &= 0xff;

        /*
         *      Churn the pool every so often after seeding it.
         */
        if (((int) (hash & 0xff)) == lrad_rand_index) {
                lrad_isaac(&lrad_rand_pool);
        }
}


/*
 *      Return a 32-bit random number.
 */
uint32_t lrad_rand(void)
{
        uint32_t num;

        /*
         *      Ensure that the pool is initialized.
         */
        if (lrad_rand_index < 0) {
                lrad_rand_seed(NULL, 0);
        }

        /*
         *      We don't return data directly from the pool.
         *      Rather, we return a summary of the data.
         */
        num = lrad_rand_pool.randrsl[lrad_rand_index & 0xff];
        lrad_rand_index++;
        lrad_rand_index &= 0xff;

        /*
         *      Every so often, churn the pool.
         */
        if (((int) (num & 0xff)) == lrad_rand_index) {
                lrad_isaac(&lrad_rand_pool);
        }

        return num;
}

/*
 *      Allocate a new RADIUS_PACKET
 */
RADIUS_PACKET *rad_alloc(int newvector)
{
        RADIUS_PACKET   *rp;

        if ((rp = malloc(sizeof(RADIUS_PACKET))) == NULL) {
                librad_log("out of memory");
                return NULL;
        }
        memset(rp, 0, sizeof(RADIUS_PACKET));
        if (newvector) {
                int i;
                uint32_t hash, base;

                /*
                 *      Don't expose the actual contents of the random
                 *      pool.
                 */
                base = lrad_rand();
                for (i = 0; i < AUTH_VECTOR_LEN; i += sizeof(uint32_t)) {
                        hash = lrad_rand() ^ base;
                        memcpy(rp->vector + i, &hash, sizeof(hash));
                }
        }
        lrad_rand();

        return rp;
}

/*
 *      Free a RADIUS_PACKET
 */
void rad_free(RADIUS_PACKET **radius_packet_ptr)
{
        RADIUS_PACKET *radius_packet;

        if (!radius_packet_ptr) return;
        radius_packet = *radius_packet_ptr;

        if (radius_packet->data) free(radius_packet->data);
        if (radius_packet->vps) pairfree(&radius_packet->vps);

        free(radius_packet);

        *radius_packet_ptr = NULL;
}