sendserver.c

/*
 * Copyright (C) 1995,1996,1997 Lars Fenneberg
 * Copyright (C) 2015,2016 Nikos Mavrogiannopoulos
 *
 * Copyright 1992 Livingston Enterprises, Inc.
 *
 * Copyright 1992,1993, 1994,1995 The Regents of the University of Michigan
 * and Merit Network, Inc. All Rights Reserved
 *
 * See the file COPYRIGHT for the respective terms and conditions.
 *
 */
 
#include <includes.h>
#include <radcli/radcli.h>
#include <pathnames.h>
#include <poll.h>
#include "util.h"
#include "rc-md5.h"
#include "rc-hmac.h"
 
#if defined(HAVE_GNUTLS)
# include <gnutls/gnutls.h>
# include <gnutls/crypto.h>
#endif
 
#if defined(__linux__)
#include <linux/in6.h>
#endif
 
 
#define SCLOSE(fd) if (sfuncs->close_fd) sfuncs->close_fd(fd)

static void rc_random_vector(unsigned char[AUTH_VECTOR_LEN]);
static int rc_check_reply(AUTH_HDR *, int, char const *, unsigned char const *,
                          unsigned char);

 
/* Packs an attribute value pair list into a buffer
 *
 * @param vp a pointer to a VALUE_PAIR.
 * @param secret the secret used by the server.
 * @param auth a pointer to AUTH_HDR.
 * @param max_len maximum total packet length in bytes (header + attributes);
 *        callers must subtract any bytes appended after this call (e.g. 18
 *        bytes for Message-Authenticator on auth requests).
 * @return The number of octets packed, or -1 if any attribute value exceeds
 *         253 bytes or the packet would exceed max_len.
 */
int rc_pack_list(VALUE_PAIR * vp, char *secret, AUTH_HDR * auth, int max_len)
{
        int length, i, pc, padded_length;
        size_t secretlen;
        uint32_t lvalue, vendor;
        unsigned char passbuf[RC_MAX(AUTH_PASS_LEN, CHAP_VALUE_LENGTH)];
        unsigned char md5buf[MAX_SECRET_LENGTH + AUTH_VECTOR_LEN];
        unsigned char *vector;
        pkt_buf pb;
        uint8_t *attr_start, *attr_len_ptr, *vsa_len_ptr;
 
        /* head = start of RADIUS packet; tail starts after the fixed header;
         * pb_written() will return the total packet length (header + attrs). */
        pb.head = (uint8_t *)auth;
        pb.data = (uint8_t *)auth;
        pb.tail = auth->data;
        pb.end  = (uint8_t *)auth + max_len;
 
        while (vp != NULL) {
                vsa_len_ptr = NULL;
                unsigned max_vlen = AUTH_STRING_LEN;        /* 253: RFC 2865 per-attribute value limit */
 
                if (VENDOR(vp->attribute) != 0) {
                        max_vlen = AUTH_STRING_LEN - VSA_HDR_LEN; /* 247: VSA envelope consumes 6 bytes */
                        if (pb_put_byte(&pb, PW_VENDOR_SPECIFIC) < 0) goto too_large;
                        vsa_len_ptr = pb.tail;
                        if (pb_put_byte(&pb, 6) < 0) goto too_large;
                        vendor = htonl(VENDOR(vp->attribute));
                        if (pb_put_bytes(&pb, &vendor, sizeof(uint32_t)) < 0) goto too_large;
                }
 
                attr_start = pb.tail;
                if (pb_put_byte(&pb, vp->attribute & 0xff) < 0) goto too_large;
                attr_len_ptr = pb.tail;
                if (pb_put_byte(&pb, 2) < 0) goto too_large;  /* placeholder; patched below */
 
                switch (vp->attribute) {
                case PW_USER_PASSWORD:
                        length = vp->lvalue;
                        if (length > AUTH_PASS_LEN)
                                length = AUTH_PASS_LEN;
                        padded_length =
                            (length + (AUTH_VECTOR_LEN - 1)) & ~(AUTH_VECTOR_LEN - 1);
 
                        if (pb.tail + padded_length > pb.end) goto too_large;
 
                        /* Pad the password with zeros */
                        memset((char *)passbuf, '\0', AUTH_PASS_LEN);
                        memcpy((char *)passbuf, vp->strvalue, (size_t) length);
 
                        secretlen = strlen(secret);
                        if (secretlen > MAX_SECRET_LENGTH)
                                secretlen = MAX_SECRET_LENGTH;
                        vector = (unsigned char *)auth->vector;
                        for (i = 0; i < padded_length; i += AUTH_VECTOR_LEN) {
                                /* Build hash input: secret || vector */
                                memcpy(md5buf, secret, secretlen);
                                memcpy(md5buf + secretlen, vector, AUTH_VECTOR_LEN);
                                rc_md5_calc(pb.tail, md5buf, secretlen + AUTH_VECTOR_LEN);
 
                                /* Remember the start of the digest */
                                vector = pb.tail;
 
                                /* Xor the password into the MD5 digest */
                                for (pc = i; pc < (i + AUTH_VECTOR_LEN); pc++)
                                        *pb.tail++ ^= passbuf[pc];
                        }
                        break;
 
                default:
                        switch (vp->type) {
                        case PW_TYPE_STRING:
                        case PW_TYPE_IPV6PREFIX:
                                if (vp->lvalue > max_vlen) goto too_large;
                                if (pb_put_bytes(&pb, vp->strvalue, (int)vp->lvalue) < 0)
                                        goto too_large;
                                break;
 
                        case PW_TYPE_IPV6ADDR:
                                if (pb_put_bytes(&pb, vp->strvalue, 16) < 0)
                                        goto too_large;
                                break;
 
                        case PW_TYPE_INTEGER:
                        case PW_TYPE_IPADDR:
                        case PW_TYPE_DATE:
                                lvalue = htonl(vp->lvalue);
                                if (pb_put_bytes(&pb, &lvalue, sizeof(uint32_t)) < 0)
                                        goto too_large;
                                break;
 
                        default:
                                break;
                        }
                        break;
                }
 
                /* Patch back lengths: attr_len = type(1) + len(1) + value */
                *attr_len_ptr = (uint8_t)(pb.tail - attr_start);
                if (vsa_len_ptr != NULL)
                        *vsa_len_ptr += *attr_len_ptr;
 
                vp = vp->next;
        }
        return (int)pb_written(&pb);  /* total packet bytes: AUTH_HDR_LEN + attrs */
 
too_large:
        rc_log(LOG_ERR, "rc_pack_list: attribute value too large or packet would exceed %d bytes", max_len);
        return -1;
}
 
/* Appends a string to the provided buffer
 *
 * @param dest the destination buffer.
 * @param max_size the maximum size available in the destination buffer.
 * @param pos the current position in the dest buffer; initially must be zero.
 * @param src the source buffer to append.
 */
static void strappend(char *dest, unsigned max_size, int *pos, const char *src)
{
        unsigned len = strlen(src) + 1;
 
        if (*pos == -1)
                return;
 
        if (len + *pos > max_size) {
                *pos = -1;
                return;
        }
 
        memcpy(&dest[*pos], src, len);
        *pos += len - 1;
        return;
}
 

static int populate_ctx(RC_AAA_CTX ** ctx, char secret[MAX_SECRET_LENGTH + 1],
                        uint8_t vector[AUTH_VECTOR_LEN])
{
        if (ctx) {
                if (*ctx != NULL)
                        return ERROR_RC;
 
                *ctx = malloc(sizeof(RC_AAA_CTX));
                if (*ctx) {
                        memcpy((*ctx)->secret, secret, sizeof((*ctx)->secret));
                        memcpy((*ctx)->request_vector, vector,
                               sizeof((*ctx)->request_vector));
                } else {
                        return ERROR_RC;
                }
        }
        return OK_RC;
}

int rc_send_server(rc_handle * rh, SEND_DATA * data, char *msg, rc_type type)
{
        return rc_send_server_ctx(rh, NULL, data, msg, type, 0);
}
 
/* Verify items in returned packet
 *
 * @param auth a pointer to AUTH_HDR.
 * @param bufferlen the available buffer length.
 * @param secret the secret used by the server.
 * @param vector a random vector of %AUTH_VECTOR_LEN.
 * @param seq_nbr a unique sequence number.
 * @return OK_RC upon success, BADRESP_RC if anything looks funny.
 */
static int rc_check_reply(AUTH_HDR * auth, int bufferlen, char const *secret,
                          unsigned char const *vector, uint8_t seq_nbr)
{
        int secretlen;
        int totallen;
        unsigned char calc_digest[AUTH_VECTOR_LEN];
        unsigned char reply_digest[AUTH_VECTOR_LEN];
 
        totallen = ntohs(auth->length);
        secretlen = (int)strlen(secret);
 
        /* Do sanity checks on packet length */
        if ((totallen < 20) || (totallen > 4096)) {
                rc_log(LOG_ERR,
                       "rc_check_reply: received RADIUS server response with invalid length");
                return BADRESP_RC;
        }
 
        /* Verify buffer space, should never trigger with current buffer size and check above */
        if ((totallen + secretlen) > bufferlen) {
                rc_log(LOG_ERR,
                       "rc_check_reply: not enough buffer space to verify RADIUS server response");
                return BADRESP_RC;
        }
 
        /* Verify that id (seq. number) matches what we sent */
        if (auth->id != seq_nbr) {
                rc_log(LOG_ERR,
                       "rc_check_reply: received non-matching id in RADIUS server response");
                return BADRESPID_RC;
        }
        /* Verify the reply digest */
        memcpy((char *)reply_digest, (char *)auth->vector, AUTH_VECTOR_LEN);
        memcpy((char *)auth->vector, (char *)vector, AUTH_VECTOR_LEN);
        memcpy((char *)auth + totallen, secret, secretlen);
        rc_md5_calc(calc_digest, (unsigned char *)auth, totallen + secretlen);
 
        if (rc_memcmp((char *)reply_digest, (char *)calc_digest,
                      AUTH_VECTOR_LEN) != 0) {
                rc_log(LOG_ERR,
                       "rc_check_reply: received invalid reply digest from RADIUS server");
                return BADRESP_RC;
        }
 
        return OK_RC;
 
}
 
/* Generates a random vector of AUTH_VECTOR_LEN octets
 *
 * @param vector a buffer with at least %AUTH_VECTOR_LEN bytes.
 */
static void rc_random_vector(unsigned char vector[AUTH_VECTOR_LEN])
{
#if defined(HAVE_GNUTLS)
        int ret = gnutls_rnd(GNUTLS_RND_NONCE, vector, AUTH_VECTOR_LEN);
        assert(ret >= 0);
#else
        int ret = getentropy(vector, AUTH_VECTOR_LEN);
        assert(ret == 0);
#endif
}

 

static int add_msg_auth_attr(rc_handle * rh, char * secret,
                        AUTH_HDR *auth, int total_length)
{
        size_t secretlen = strlen(secret);
        uint8_t *msg_auth = (uint8_t *)auth + total_length;
        msg_auth[0] = PW_MESSAGE_AUTHENTICATOR;
        msg_auth[1] = 18;
        memset(&msg_auth[2], 0, MD5_DIGEST_SIZE);
        total_length += 18;
        auth->length = htons((unsigned short)total_length);
 
        /* Calculate HMAC-MD5 [RFC2104] hash */
        uint8_t digest[MD5_DIGEST_SIZE];
        rc_hmac_md5((uint8_t *)auth, (size_t)total_length, (uint8_t *)secret, secretlen, digest);
        memcpy(&msg_auth[2], digest, MD5_DIGEST_SIZE);
 
        return total_length;
}

static int validate_message_authenticator(const uint8_t *recv_buffer,
                                          size_t length, const char *secret,
                                          const unsigned char *req_auth)
{
        uint8_t verify_buffer[RC_BUFFER_LEN];
        pkt_buf vb;
        uint8_t ma_copy[MD5_DIGEST_SIZE];
        uint8_t digest[MD5_DIGEST_SIZE];
        uint8_t attr_type, attr_len;
        int ma_found = 0;
 
        if (AUTH_HDR_LEN + length > sizeof(verify_buffer)) {
                rc_log(LOG_ERR, "%s: packet too large for verification buffer", __func__);
                return -1;
        }
 
        /* Copy the packet, substitute the Request Authenticator per RFC 3579 §3.2,
         * and zero the Message-Authenticator value before computing HMAC-MD5. */
        memcpy(verify_buffer, recv_buffer, AUTH_HDR_LEN + length);
        memcpy(verify_buffer + 4, req_auth, AUTH_VECTOR_LEN);
        pb_init_read(&vb, verify_buffer + AUTH_HDR_LEN, length, length);
 
        while (pb_len(&vb) >= 2) {
                attr_type = vb.data[0];
                attr_len  = vb.data[1];
                if (attr_len < 2 || (size_t)attr_len > pb_len(&vb))
                        break;  /* malformed; already rejected by upstream attr-loop */
 
                if (attr_type == PW_MESSAGE_AUTHENTICATOR) {
                        if (attr_len != 2 + MD5_DIGEST_SIZE) {
                                rc_log(LOG_ERR, "%s: Message-Authenticator has wrong length %u",
                                       __func__, (unsigned)(attr_len - 2));
                                return -1;
                        }
                        /* Save original value before zeroing in the verification copy */
                        memcpy(ma_copy, vb.data + 2, MD5_DIGEST_SIZE);
                        memset(vb.data + 2, '\0', MD5_DIGEST_SIZE);
                        ma_found = 1;
                        break;
                }
                assert(pb_pull(&vb, attr_len) == 0);
        }
 
        if (!ma_found)
                return -1;
 
        rc_hmac_md5(verify_buffer, AUTH_HDR_LEN + length, (uint8_t *)secret, strlen(secret), digest);
        return rc_memcmp(ma_copy, digest, MD5_DIGEST_SIZE);
}

int rc_send_server_ctx(rc_handle * rh, RC_AAA_CTX ** ctx, SEND_DATA * data,
                       char *msg, rc_type type, int no_wait)
{
        int sockfd = -1;
        AUTH_HDR *auth, *recv_auth;
        char *server_name, *p;  /* Name of server to query */
        struct sockaddr_storage our_sockaddr;
        struct addrinfo *auth_addr = NULL;
        socklen_t salen;
        int result = 0;
        int total_length;
        int length, pos;
        int retry_max;
        const rc_sockets_override *sfuncs;
        unsigned discover_local_ip;
        size_t secretlen;
        char secret[MAX_SECRET_LENGTH + 1];
        unsigned char vector[AUTH_VECTOR_LEN];
        uint8_t recv_buffer[RC_BUFFER_LEN];
        uint8_t send_buffer[RC_BUFFER_LEN];
        uint16_t tlen;
        pkt_buf rb;
        uint8_t attr_type, attr_len;
        int retries;
        VALUE_PAIR *vp;
        struct pollfd pfd;
        double start_time, timeout;
        struct sockaddr_storage *ss_set = NULL;
        char *server_type = "auth";
        char *ns = NULL;
        int ns_def_hdl = 0;
 
        server_name = data->server;
        if (server_name == NULL || server_name[0] == '\0')
                return ERROR_RC;
 
        ns = rc_conf_str(rh, "namespace"); /* Check for namespace config */
        if (ns != NULL) {
                if(-1 == rc_set_netns(ns, &ns_def_hdl)) {
                        rc_log(LOG_ERR, "rc_send_server: namespace %s set failed", ns);
                        return ERROR_RC;
                }
        }
        if ((vp = rc_avpair_get(data->send_pairs, PW_SERVICE_TYPE, 0)) &&
            (vp->lvalue == PW_ADMINISTRATIVE)) {
                strlcpy(secret, MGMT_POLL_SECRET, sizeof(secret));
                auth_addr =
                    rc_getaddrinfo(server_name,
                                   type == AUTH ? PW_AI_AUTH : PW_AI_ACCT);
                if (auth_addr == NULL) {
                        result = ERROR_RC;
                        goto exit_error;
                }
        } else {
                if (data->secret != NULL) {
                        strlcpy(secret, data->secret, sizeof(secret));
                }
                /*
                   else
                   {
                 */
                if (rc_find_server_addr
                    (rh, server_name, &auth_addr, secret, type) != 0) {
                        rc_log(LOG_ERR,
                               "rc_send_server: unable to find server: %s",
                               server_name);
                        result = ERROR_RC;
                        goto exit_error;
                }
                /*} */
        }
 
        sfuncs = &rh->so;
 
        if (sfuncs->static_secret) {
                /* any static secret set in sfuncs overrides the configured */
                strlcpy(secret, sfuncs->static_secret, sizeof(secret));
        }
 
        if (sfuncs->lock) {
                if (sfuncs->lock(sfuncs->ptr) != 0) {
                        rc_log(LOG_ERR, "%s: lock error", __func__);
                        result = ERROR_RC;
                        goto exit_error;
                }
        }
 
        rc_own_bind_addr(rh, &our_sockaddr);
        discover_local_ip = 0;
        if (our_sockaddr.ss_family == AF_INET) {
                if (((struct sockaddr_in *)(&our_sockaddr))->sin_addr.s_addr ==
                    INADDR_ANY) {
                        discover_local_ip = 1;
                }
        }
 
        DEBUG(LOG_ERR, "DEBUG: rc_send_server: creating socket to: %s",
              server_name);
        if (discover_local_ip) {
                result = rc_get_srcaddr(SA(&our_sockaddr), auth_addr->ai_addr);
                if (result != OK_RC) {
                        memset(secret, '\0', sizeof(secret));
                        rc_log(LOG_ERR,
                               "rc_send_server: cannot figure our own address");
                        goto cleanup;
                }
        }
 
        if (sfuncs->get_fd) {
                sockfd = sfuncs->get_fd(sfuncs->ptr, SA(&our_sockaddr));
                if (sockfd < 0) {
                        memset(secret, '\0', sizeof(secret));
                        rc_log(LOG_ERR, "rc_send_server: socket: %s",
                               strerror(errno));
                        result = ERROR_RC;
                        goto cleanup;
                }
        }
 
        if(our_sockaddr.ss_family  == AF_INET6) {
                /* Check for IPv6 non-temporary address support */
                char *non_temp_addr = rc_conf_str(rh, "use-public-addr");
                if (non_temp_addr && (strcasecmp(non_temp_addr, "true") == 0)) {
#if defined(__linux__)
                        int sock_opt = IPV6_PREFER_SRC_PUBLIC;
                        if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_ADDR_PREFERENCES,
                                        &sock_opt, sizeof(sock_opt)) != 0) {
                                rc_log(LOG_ERR, "rc_send_server: setsockopt: %s",
                                        strerror(errno));
                                result = ERROR_RC;
                                goto cleanup;
                        }
#elif defined(BSD) || defined(__APPLE__)
                        int sock_opt = 0;
                        if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_PREFER_TEMPADDR,
                                &sock_opt, sizeof(sock_opt)) != 0) {
                                rc_log(LOG_ERR, "rc_send_server: setsockopt: %s",
                                        strerror(errno));
                                result = ERROR_RC;
                                goto cleanup;
                        }
#else
                        rc_log(LOG_INFO, "rc_send_server: Usage of non-temporary IPv6"
                                        " address is not supported in this system");
#endif
                }
        }
 
        retry_max = data->retries;      /* Max. numbers to try for reply */
        retries = 0;            /* Init retry cnt for blocking call */
 
        if (data->svc_port) {
                if (our_sockaddr.ss_family == AF_INET)
                        ((struct sockaddr_in *)auth_addr->ai_addr)->sin_port =
                            htons((unsigned short)data->svc_port);
                else
                        ((struct sockaddr_in6 *)auth_addr->ai_addr)->sin6_port =
                            htons((unsigned short)data->svc_port);
        }
 
        /*
         * Fill in NAS-IP-Address (if needed)
         */
        if (rh->nas_addr_set) {
                rc_avpair_remove(&(data->send_pairs), PW_NAS_IP_ADDRESS, 0);
                rc_avpair_remove(&(data->send_pairs), PW_NAS_IPV6_ADDRESS, 0);
 
                ss_set = &rh->nas_addr;
        } else if (rc_avpair_get(data->send_pairs, PW_NAS_IP_ADDRESS, 0) == NULL &&
                   rc_avpair_get(data->send_pairs, PW_NAS_IPV6_ADDRESS, 0) == NULL) {
 
                ss_set = &our_sockaddr;
        }
 
        if (ss_set) {
                if (ss_set->ss_family == AF_INET) {
                        uint32_t ip;
                        ip = *((uint32_t
                                *) (&((struct sockaddr_in *)ss_set)->
                                    sin_addr));
                        ip = ntohl(ip);
 
                        rc_avpair_add(rh, &(data->send_pairs),
                                      PW_NAS_IP_ADDRESS, &ip, 0, 0);
                } else {
                        void *p;
                        p = &((struct sockaddr_in6 *)ss_set)->sin6_addr;
 
                        rc_avpair_add(rh, &(data->send_pairs),
                                      PW_NAS_IPV6_ADDRESS, p, 16, 0);
                }
        }
 
        /*
         * Fill in NAS-Identifier (if needed)
         */
        p = rc_conf_str(rh, "nas-identifier");
        if (p != NULL) {
                rc_avpair_remove(&(data->send_pairs), PW_NAS_IDENTIFIER, 0);
                rc_avpair_add(rh, &(data->send_pairs),
                              PW_NAS_IDENTIFIER, p, -1, 0);
        }
 
        /* Build a request */
        auth = (AUTH_HDR *) send_buffer;
        auth->code = data->code;
        auth->id = data->seq_nbr;
 
        if (data->code == PW_ACCOUNTING_REQUEST) {
                server_type = "acct";
                total_length = rc_pack_list(data->send_pairs, secret, auth, RC_MAX_PACKET_LEN);
                if (total_length < 0) {
                        result = ERROR_RC;
                        goto cleanup;
                }
 
                tlen = htons((unsigned short)total_length);
                memcpy(&auth->length, &tlen, sizeof(uint16_t));
 
                memset((char *)auth->vector, 0, AUTH_VECTOR_LEN);
                secretlen = strlen(secret);
                memcpy((char *)auth + total_length, secret, secretlen);
                rc_md5_calc(vector, (unsigned char *)auth,
                            total_length + secretlen);
                memcpy((char *)auth->vector, (char *)vector, AUTH_VECTOR_LEN);
        } else {
                rc_random_vector(vector);
                memcpy((char *)auth->vector, (char *)vector, AUTH_VECTOR_LEN);
 
                /* Leave 2+MD5_DIGEST_SIZE bytes for Message-Authenticator (added below) */
                total_length = rc_pack_list(data->send_pairs, secret, auth,
                                            RC_MAX_PACKET_LEN - (2 + MD5_DIGEST_SIZE));
                if (total_length < 0) {
                        result = ERROR_RC;
                        goto cleanup;
                }
 
                total_length = add_msg_auth_attr(rh, secret, auth, total_length);
 
                auth->length = htons((unsigned short)total_length);
        }
 
        if (radcli_debug) {
                char our_addr_txt[50] = "";     /* hold a text IP */
                char auth_addr_txt[50] = "";    /* hold a text IP */
 
                getnameinfo(SA(&our_sockaddr), SS_LEN(&our_sockaddr), NULL, 0,
                            our_addr_txt, sizeof(our_addr_txt), NI_NUMERICHOST);
                getnameinfo(auth_addr->ai_addr, auth_addr->ai_addrlen, NULL, 0,
                            auth_addr_txt, sizeof(auth_addr_txt),
                            NI_NUMERICHOST);
 
                DEBUG(LOG_ERR,
                      "DEBUG: timeout=%d retries=%d local %s : 0, remote %s : %u\n",
                      data->timeout, retry_max, our_addr_txt, auth_addr_txt,
                      data->svc_port);
        }
 
        for (;;) {
                do {
                        result =
                            sfuncs->sendto(sfuncs->ptr, sockfd, (char *)auth,
                                           (unsigned int)total_length, (int)0,
                                           SA(auth_addr->ai_addr),
                                           auth_addr->ai_addrlen);
                } while (result == -1 && errno == EINTR);
                if (result == -1) {
                        result = errno == ENETUNREACH ? NETUNREACH_RC : ERROR_RC;
                        rc_log(LOG_ERR, "%s: socket: %s", __FUNCTION__,
                               strerror(errno));
                        goto cleanup;
                }
 
                if (no_wait) {
                        /* Fire-and-forget: no reply to wait for, so close the
                         * socket and capture the request's own secret/vector
                         * (REQ-NET-TEARDOWN-001, REQ-NET-SEC-009) right here,
                         * instead of falling through to the receive/switch
                         * path below that expects a parsed response. */
                        SCLOSE(sockfd);
                        result = populate_ctx(ctx, secret, vector);
                        memset(secret, '\0', sizeof(secret));
                        if (result != OK_RC)
                                goto cleanup;
                        result = OK_RC;
                        goto cleanup;
                }
 
                /* Re-fetch fd: sendto() may have triggered a TLS session
                 * restart (restart_session), replacing the underlying socket. */
                if (sfuncs->get_active_fd) {
                        int new_fd = sfuncs->get_active_fd(sfuncs->ptr);
                        if (new_fd >= 0)
                                sockfd = new_fd;
                }
                pfd.fd = sockfd;
                pfd.events = POLLIN;
                pfd.revents = 0;
                start_time = rc_getmtime();
                for (timeout = data->timeout; timeout > 0;
                     timeout -= rc_getmtime() - start_time) {
                        result = poll(&pfd, 1, timeout * 1000);
                        if (result != -1 || errno != EINTR)
                                break;
                }
 
                if (result == -1) {
                        rc_log(LOG_ERR, "rc_send_server: poll: %s",
                               strerror(errno));
                        memset(secret, '\0', sizeof(secret));
                        SCLOSE(sockfd);
                        result = ERROR_RC;
                        goto cleanup;
                }
 
                if (result == 1 && (pfd.revents & POLLIN) != 0) {
                        salen = auth_addr->ai_addrlen;
                        do {
                                length = sfuncs->recvfrom(sfuncs->ptr, sockfd,
                                                          (char *)recv_buffer,
                                                          (int)
                                                          sizeof(recv_buffer),
                                                          (int)0,
                                                          SA(auth_addr->
                                                             ai_addr), &salen);
                        } while (length == -1 && errno == EINTR);
 
                        if (length <= 0) {
                                int e = errno;
                                rc_log(LOG_ERR,
                                       "rc_send_server: recvfrom: %s:%d: %s",
                                       server_name, data->svc_port,
                                       strerror(e));
                                if (length == -1 && (e == EAGAIN || e == EINTR))
                                        continue;
                                SCLOSE(sockfd);
                                memset(secret, '\0', sizeof(secret));
                                result = ERROR_RC;
                                goto cleanup;
                        }
 
                        recv_auth = (AUTH_HDR *) recv_buffer;
 
                        if (length < AUTH_HDR_LEN
                            || length < ntohs(recv_auth->length)) {
                                rc_log(LOG_ERR,
                                       "rc_send_server: recvfrom: %s:%d: reply is too short",
                                       server_name, data->svc_port);
                                SCLOSE(sockfd);
                                memset(secret, '\0', sizeof(secret));
                                result = ERROR_RC;
                                goto cleanup;
                        }
 
                        result =
                            rc_check_reply(recv_auth, RC_BUFFER_LEN, secret,
                                           vector, data->seq_nbr);
                        if (result != BADRESPID_RC) {
                                /* if a message that doesn't match our ID was received, then ignore
                                 * it, and try to receive more, until timeout. That is because in
                                 * DTLS the channel is shared, and we may receive duplicates or
                                 * out-of-order packets. */
                                break;
                        }
                }
 
                /*
                 * Timed out waiting for response.  Retry "retry_max" times
                 * before giving up.  If retry_max = 0, don't retry at all.
                 */
                if (retries++ >= retry_max) {
                        char radius_server_ip[128];
                        struct sockaddr_in *si =
                            (struct sockaddr_in *)auth_addr->ai_addr;
                        inet_ntop(auth_addr->ai_family, &si->sin_addr,
                                  radius_server_ip, sizeof(radius_server_ip));
                        rc_log(LOG_ERR,
                               "rc_send_server: no reply from RADIUS %s server %s:%u",
                               server_type, radius_server_ip, data->svc_port);
                        SCLOSE(sockfd);
                        memset(secret, '\0', sizeof(secret));
                        result = TIMEOUT_RC;
                        goto cleanup;
                }
        }
 
        /*
         *      If UDP is larger than RADIUS, shorten it to RADIUS.
         */
        if (length > ntohs(recv_auth->length))
                length = ntohs(recv_auth->length);
 
        /*
         *      Verify that it's a valid RADIUS packet before doing ANYTHING with it.
         */
        pb_init_read(&rb, recv_buffer, length, RC_BUFFER_LEN);
        assert(pb_pull(&rb, AUTH_HDR_LEN) == 0);
        while (pb_len(&rb) > 0) {
                if (pb_peek_byte(&rb, 0, &attr_type) < 0 ||
                    pb_peek_byte(&rb, 1, &attr_len)  < 0) {
                        rc_log(LOG_ERR,
                               "rc_send_server: recvfrom: %s:%d: truncated attribute",
                               server_name, data->svc_port);
                        SCLOSE(sockfd);
                        memset(secret, '\0', sizeof(secret));
                        result = ERROR_RC;
                        goto cleanup;
                }
                if (attr_type == 0) {
                        rc_log(LOG_ERR,
                               "rc_send_server: recvfrom: %s:%d: attribute zero is invalid",
                               server_name, data->svc_port);
                        SCLOSE(sockfd);
                        memset(secret, '\0', sizeof(secret));
                        result = ERROR_RC;
                        goto cleanup;
                }
                if (attr_len < 2) {
                        rc_log(LOG_ERR,
                               "rc_send_server: recvfrom: %s:%d: attribute length is too small",
                               server_name, data->svc_port);
                        SCLOSE(sockfd);
                        memset(secret, '\0', sizeof(secret));
                        result = ERROR_RC;
                        goto cleanup;
                }
                if (attr_len > pb_len(&rb)) {
                        rc_log(LOG_ERR,
                               "rc_send_server: recvfrom: %s:%d: attribute overflows the packet",
                               server_name, data->svc_port);
                        SCLOSE(sockfd);
                        memset(secret, '\0', sizeof(secret));
                        result = ERROR_RC;
                        goto cleanup;
                }
                assert(pb_pull(&rb, attr_len) == 0);
        }
 
        length = ntohs(recv_auth->length) - AUTH_HDR_LEN;
        if (length > 0) {
                data->receive_pairs = rc_avpair_gen(rh, NULL, recv_auth->data,
                                                    length, 0);
        } else {
                data->receive_pairs = NULL;
        }
 
        SCLOSE(sockfd);
        result = populate_ctx(ctx, secret, vector);
        if (result != OK_RC) {
                memset(secret, '\0', sizeof(secret));
                goto cleanup;
        }
 
        /* Per draft-ietf-radext-deprecating-radius, Message-Authenticator MUST
         * be the first attribute in Access-Request responses to prevent MD5
         * prefix attacks (BLAST RADIUS). Not required for Accounting-Response. */
        if (type == AUTH) {
                /* Verify MA whenever present, regardless of position.
                 * An incorrect MA always causes rejection. */
                if (rc_avpair_get(data->receive_pairs, PW_MESSAGE_AUTHENTICATOR, 0)) {
                        if (validate_message_authenticator(recv_buffer, length, secret, vector)) {
                                rc_log(LOG_ERR,
                                       "rc_send_server: recvfrom: %s:%d: received attribute Message-Authenticator is incorrect",
                                       server_name, data->svc_port);
                                memset(secret, '\0', sizeof(secret));
                                result = ERROR_RC;
                                goto cleanup;
                        }
                }
 
                /* Enforce BLAST RADIUS: MA must also be the first attribute.
                 * Per draft-ietf-radext-deprecating-radius-10 Section 4, this
                 * mitigation MUST be applied to RADIUS/UDP and RADIUS/TCP, and
                 * MUST NOT be applied to RADIUS/TLS or RADIUS/DTLS: those
                 * transports are already integrity-protected end-to-end, so the
                 * MD5-prefix collision this guards against isn't reachable. */
                if (rh->so_type != RC_SOCKET_TLS && rh->so_type != RC_SOCKET_DTLS) {
                        if (length == 0 ||
                            recv_buffer[AUTH_HDR_LEN] != PW_MESSAGE_AUTHENTICATOR) {
                                p = rc_conf_str(rh, "require-message-authenticator");
                                if (p == NULL || (strcasecmp(p, "false") != 0 && strcasecmp(p, "no") != 0)) {
                                        rc_log(LOG_ERR,
                                               "rc_send_server: recvfrom: %s:%d: required attribute Message-Authenticator is missing or not first",
                                               server_name, data->svc_port);
                                        memset(secret, '\0', sizeof(secret));
                                        result = ERROR_RC;
                                        goto cleanup;
                                }
                        }
                }
        }
 
        memset(secret, '\0', sizeof(secret));
 
        if (msg) {
                *msg = '\0';
                pos = 0;
                vp = data->receive_pairs;
                while (vp) {
                        if ((vp = rc_avpair_get(vp, PW_REPLY_MESSAGE, 0))) {
                                strappend(msg, PW_MAX_MSG_SIZE, &pos,
                                          vp->strvalue);
                                strappend(msg, PW_MAX_MSG_SIZE, &pos, "\n");
                                vp = vp->next;
                        }
                }
        }
 
        switch (recv_auth->code) {
        case PW_ACCESS_ACCEPT:
        case PW_PASSWORD_ACK:
        case PW_ACCOUNTING_RESPONSE:
                result = OK_RC;
                break;
 
        case PW_ACCESS_REJECT:
        case PW_PASSWORD_REJECT:
                result = REJECT_RC;
                break;
 
        case PW_ACCESS_CHALLENGE:
                result = CHALLENGE_RC;
                break;
 
        default:
                rc_log(LOG_ERR, "rc_send_server: received RADIUS server response neither ACCEPT nor REJECT, code=%d is invalid",
                       recv_auth->code);
                result = BADRESP_RC;
        }
 
 cleanup:
        if (auth_addr)
                freeaddrinfo(auth_addr);
 
        if (sfuncs->unlock) {
                if (sfuncs->unlock(sfuncs->ptr) != 0) {
                        rc_log(LOG_ERR, "%s: unlock error", __func__);
                }
        }
 exit_error:
        if (ns != NULL) {
                if(-1 == rc_reset_netns(&ns_def_hdl)) {
                        rc_log(LOG_ERR, "rc_send_server: namespace %s reset failed", ns);
                        result = ERROR_RC;
                }
        }
 
        return result;
}