tlsv1_server_write.c

Go to the documentation of this file.

/*
 * TLSv1 server - write handshake message
 * Copyright (c) 2006-2007, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "crypto/md5.h"
#include "crypto/sha1.h"
#include "crypto/tls.h"
#include "x509v3.h"
#include "tlsv1_common.h"
#include "tlsv1_record.h"
#include "tlsv1_server.h"
#include "tlsv1_server_i.h"


static size_t tls_server_cert_chain_der_len(struct tlsv1_server *conn)
{
        size_t len = 0;
        struct x509_certificate *cert;

        cert = conn->cred->cert;
        while (cert) {
                len += 3 + cert->cert_len;
                if (x509_certificate_self_signed(cert))
                        break;
                cert = x509_certificate_get_subject(conn->cred->trusted_certs,
                                                    &cert->issuer);
        }

        return len;
}


static int tls_write_server_hello(struct tlsv1_server *conn,
                                  u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length;
        struct os_time now;
        size_t rlen;

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send ServerHello");
        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;

        os_get_time(&now);
        WPA_PUT_BE32(conn->server_random, now.sec);
        if (os_get_random(conn->server_random + 4, TLS_RANDOM_LEN - 4)) {
                wpa_printf(MSG_ERROR, "TLSv1: Could not generate "
                           "server_random");
                return -1;
        }
        wpa_hexdump(MSG_MSGDUMP, "TLSv1: server_random",
                    conn->server_random, TLS_RANDOM_LEN);

        conn->session_id_len = TLS_SESSION_ID_MAX_LEN;
        if (os_get_random(conn->session_id, conn->session_id_len)) {
                wpa_printf(MSG_ERROR, "TLSv1: Could not generate "
                           "session_id");
                return -1;
        }
        wpa_hexdump(MSG_MSGDUMP, "TLSv1: session_id",
                    conn->session_id, conn->session_id_len);

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_SERVER_HELLO;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        /* body - ServerHello */
        /* ProtocolVersion server_version */
        WPA_PUT_BE16(pos, TLS_VERSION);
        pos += 2;
        /* Random random: uint32 gmt_unix_time, opaque random_bytes */
        os_memcpy(pos, conn->server_random, TLS_RANDOM_LEN);
        pos += TLS_RANDOM_LEN;
        /* SessionID session_id */
        *pos++ = conn->session_id_len;
        os_memcpy(pos, conn->session_id, conn->session_id_len);
        pos += conn->session_id_len;
        /* CipherSuite cipher_suite */
        WPA_PUT_BE16(pos, conn->cipher_suite);
        pos += 2;
        /* CompressionMethod compression_method */
        *pos++ = TLS_COMPRESSION_NULL;

        if (conn->session_ticket && conn->session_ticket_cb) {
                int res = conn->session_ticket_cb(
                        conn->session_ticket_cb_ctx,
                        conn->session_ticket, conn->session_ticket_len,
                        conn->client_random, conn->server_random,
                        conn->master_secret);
                if (res < 0) {
                        wpa_printf(MSG_DEBUG, "TLSv1: SessionTicket callback "
                                   "indicated failure");
                        tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                           TLS_ALERT_HANDSHAKE_FAILURE);
                        return -1;
                }
                conn->use_session_ticket = res;

                if (conn->use_session_ticket) {
                        if (tlsv1_server_derive_keys(conn, NULL, 0) < 0) {
                                wpa_printf(MSG_DEBUG, "TLSv1: Failed to "
                                           "derive keys");
                                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                                   TLS_ALERT_INTERNAL_ERROR);
                                return -1;
                        }
                }

                /*
                 * RFC 4507 specifies that server would include an empty
                 * SessionTicket extension in ServerHello and a
                 * NewSessionTicket message after the ServerHello. However,
                 * EAP-FAST (RFC 4851), i.e., the only user of SessionTicket
                 * extension at the moment, does not use such extensions.
                 *
                 * TODO: Add support for configuring RFC 4507 behavior and make
                 * EAP-FAST disable it.
                 */
        }

        WPA_PUT_BE24(hs_length, pos - hs_length - 3);
        tls_verify_hash_add(&conn->verify, hs_start, pos - hs_start);

        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_HANDSHAKE,
                              rhdr, end - rhdr, pos - hs_start, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to create TLS record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        pos = rhdr + rlen;

        *msgpos = pos;

        return 0;
}


static int tls_write_server_certificate(struct tlsv1_server *conn,
                                        u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length, *cert_start;
        size_t rlen;
        struct x509_certificate *cert;
        const struct tls_cipher_suite *suite;

        suite = tls_get_cipher_suite(conn->rl.cipher_suite);
        if (suite && suite->key_exchange == TLS_KEY_X_DH_anon) {
                wpa_printf(MSG_DEBUG, "TLSv1: Do not send Certificate when "
                           "using anonymous DH");
                return 0;
        }

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send Certificate");
        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_CERTIFICATE;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        /* body - Certificate */
        /* uint24 length (to be filled) */
        cert_start = pos;
        pos += 3;
        cert = conn->cred->cert;
        while (cert) {
                if (pos + 3 + cert->cert_len > end) {
                        wpa_printf(MSG_DEBUG, "TLSv1: Not enough buffer space "
                                   "for Certificate (cert_len=%lu left=%lu)",
                                   (unsigned long) cert->cert_len,
                                   (unsigned long) (end - pos));
                        tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                           TLS_ALERT_INTERNAL_ERROR);
                        return -1;
                }
                WPA_PUT_BE24(pos, cert->cert_len);
                pos += 3;
                os_memcpy(pos, cert->cert_start, cert->cert_len);
                pos += cert->cert_len;

                if (x509_certificate_self_signed(cert))
                        break;
                cert = x509_certificate_get_subject(conn->cred->trusted_certs,
                                                    &cert->issuer);
        }
        if (cert == conn->cred->cert || cert == NULL) {
                /*
                 * Server was not configured with all the needed certificates
                 * to form a full certificate chain. The client may fail to
                 * validate the chain unless it is configured with all the
                 * missing CA certificates.
                 */
                wpa_printf(MSG_DEBUG, "TLSv1: Full server certificate chain "
                           "not configured - validation may fail");
        }
        WPA_PUT_BE24(cert_start, pos - cert_start - 3);

        WPA_PUT_BE24(hs_length, pos - hs_length - 3);

        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_HANDSHAKE,
                              rhdr, end - rhdr, pos - hs_start, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to generate a record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        pos = rhdr + rlen;

        tls_verify_hash_add(&conn->verify, hs_start, pos - hs_start);

        *msgpos = pos;

        return 0;
}


static int tls_write_server_key_exchange(struct tlsv1_server *conn,
                                         u8 **msgpos, u8 *end)
{
        tls_key_exchange keyx;
        const struct tls_cipher_suite *suite;
        u8 *pos, *rhdr, *hs_start, *hs_length;
        size_t rlen;
        u8 *dh_ys;
        size_t dh_ys_len;

        suite = tls_get_cipher_suite(conn->rl.cipher_suite);
        if (suite == NULL)
                keyx = TLS_KEY_X_NULL;
        else
                keyx = suite->key_exchange;

        if (!tls_server_key_exchange_allowed(conn->rl.cipher_suite)) {
                wpa_printf(MSG_DEBUG, "TLSv1: No ServerKeyExchange needed");
                return 0;
        }

        if (keyx != TLS_KEY_X_DH_anon) {
                /* TODO? */
                wpa_printf(MSG_DEBUG, "TLSv1: ServerKeyExchange not yet "
                           "supported with key exchange type %d", keyx);
                return -1;
        }

        if (conn->cred == NULL || conn->cred->dh_p == NULL ||
            conn->cred->dh_g == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: No DH parameters available for "
                           "ServerKeyExhcange");
                return -1;
        }

        os_free(conn->dh_secret);
        conn->dh_secret_len = conn->cred->dh_p_len;
        conn->dh_secret = os_malloc(conn->dh_secret_len);
        if (conn->dh_secret == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to allocate "
                           "memory for secret (Diffie-Hellman)");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        if (os_get_random(conn->dh_secret, conn->dh_secret_len)) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to get random "
                           "data for Diffie-Hellman");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                os_free(conn->dh_secret);
                conn->dh_secret = NULL;
                return -1;
        }

        if (os_memcmp(conn->dh_secret, conn->cred->dh_p, conn->dh_secret_len) >
            0)
                conn->dh_secret[0] = 0; /* make sure secret < p */

        pos = conn->dh_secret;
        while (pos + 1 < conn->dh_secret + conn->dh_secret_len && *pos == 0)
                pos++;
        if (pos != conn->dh_secret) {
                os_memmove(conn->dh_secret, pos,
                           conn->dh_secret_len - (pos - conn->dh_secret));
                conn->dh_secret_len -= pos - conn->dh_secret;
        }
        wpa_hexdump_key(MSG_DEBUG, "TLSv1: DH server's secret value",
                        conn->dh_secret, conn->dh_secret_len);

        /* Ys = g^secret mod p */
        dh_ys_len = conn->cred->dh_p_len;
        dh_ys = os_malloc(dh_ys_len);
        if (dh_ys == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to allocate memory for "
                           "Diffie-Hellman");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        if (crypto_mod_exp(conn->cred->dh_g, conn->cred->dh_g_len,
                           conn->dh_secret, conn->dh_secret_len,
                           conn->cred->dh_p, conn->cred->dh_p_len,
                           dh_ys, &dh_ys_len)) {
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                os_free(dh_ys);
                return -1;
        }

        wpa_hexdump(MSG_DEBUG, "TLSv1: DH Ys (server's public value)",
                    dh_ys, dh_ys_len);

        /*
         * struct {
         *    select (KeyExchangeAlgorithm) {
         *       case diffie_hellman:
         *          ServerDHParams params;
         *          Signature signed_params;
         *       case rsa:
         *          ServerRSAParams params;
         *          Signature signed_params;
         *    };
         * } ServerKeyExchange;
         *
         * struct {
         *    opaque dh_p<1..2^16-1>;
         *    opaque dh_g<1..2^16-1>;
         *    opaque dh_Ys<1..2^16-1>;
         * } ServerDHParams;
         */

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send ServerKeyExchange");
        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_SERVER_KEY_EXCHANGE;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;

        /* body - ServerDHParams */
        /* dh_p */
        if (pos + 2 + conn->cred->dh_p_len > end) {
                wpa_printf(MSG_DEBUG, "TLSv1: Not enough buffer space for "
                           "dh_p");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                os_free(dh_ys);
                return -1;
        }
        WPA_PUT_BE16(pos, conn->cred->dh_p_len);
        pos += 2;
        os_memcpy(pos, conn->cred->dh_p, conn->cred->dh_p_len);
        pos += conn->cred->dh_p_len;

        /* dh_g */
        if (pos + 2 + conn->cred->dh_g_len > end) {
                wpa_printf(MSG_DEBUG, "TLSv1: Not enough buffer space for "
                           "dh_g");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                os_free(dh_ys);
                return -1;
        }
        WPA_PUT_BE16(pos, conn->cred->dh_g_len);
        pos += 2;
        os_memcpy(pos, conn->cred->dh_g, conn->cred->dh_g_len);
        pos += conn->cred->dh_g_len;

        /* dh_Ys */
        if (pos + 2 + dh_ys_len > end) {
                wpa_printf(MSG_DEBUG, "TLSv1: Not enough buffer space for "
                           "dh_Ys");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                os_free(dh_ys);
                return -1;
        }
        WPA_PUT_BE16(pos, dh_ys_len);
        pos += 2;
        os_memcpy(pos, dh_ys, dh_ys_len);
        pos += dh_ys_len;
        os_free(dh_ys);

        WPA_PUT_BE24(hs_length, pos - hs_length - 3);

        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_HANDSHAKE,
                              rhdr, end - rhdr, pos - hs_start, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to generate a record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        pos = rhdr + rlen;

        tls_verify_hash_add(&conn->verify, hs_start, pos - hs_start);

        *msgpos = pos;

        return 0;
}


static int tls_write_server_certificate_request(struct tlsv1_server *conn,
                                                u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length;
        size_t rlen;

        if (!conn->verify_peer) {
                wpa_printf(MSG_DEBUG, "TLSv1: No CertificateRequest needed");
                return 0;
        }

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send CertificateRequest");
        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_CERTIFICATE_REQUEST;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        /* body - CertificateRequest */

        /*
         * enum {
         *   rsa_sign(1), dss_sign(2), rsa_fixed_dh(3), dss_fixed_dh(4),
         *   (255)
         * } ClientCertificateType;
         * ClientCertificateType certificate_types<1..2^8-1>
         */
        *pos++ = 1;
        *pos++ = 1; /* rsa_sign */

        /*
         * opaque DistinguishedName<1..2^16-1>
         * DistinguishedName certificate_authorities<3..2^16-1>
         */
        /* TODO: add support for listing DNs for trusted CAs */
        WPA_PUT_BE16(pos, 0);
        pos += 2;

        WPA_PUT_BE24(hs_length, pos - hs_length - 3);

        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_HANDSHAKE,
                              rhdr, end - rhdr, pos - hs_start, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to generate a record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        pos = rhdr + rlen;

        tls_verify_hash_add(&conn->verify, hs_start, pos - hs_start);

        *msgpos = pos;

        return 0;
}


static int tls_write_server_hello_done(struct tlsv1_server *conn,
                                       u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length;
        size_t rlen;

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send ServerHelloDone");
        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_SERVER_HELLO_DONE;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        /* body - ServerHelloDone (empty) */

        WPA_PUT_BE24(hs_length, pos - hs_length - 3);

        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_HANDSHAKE,
                              rhdr, end - rhdr, pos - hs_start, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to generate a record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        pos = rhdr + rlen;

        tls_verify_hash_add(&conn->verify, hs_start, pos - hs_start);

        *msgpos = pos;

        return 0;
}


static int tls_write_server_change_cipher_spec(struct tlsv1_server *conn,
                                               u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr;
        size_t rlen;

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send ChangeCipherSpec");
        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;
        *pos = TLS_CHANGE_CIPHER_SPEC;
        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_CHANGE_CIPHER_SPEC,
                              rhdr, end - rhdr, 1, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to create a record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }

        if (tlsv1_record_change_write_cipher(&conn->rl) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to set write cipher for "
                           "record layer");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }

        *msgpos = rhdr + rlen;

        return 0;
}


static int tls_write_server_finished(struct tlsv1_server *conn,
                                     u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length;
        size_t rlen, hlen;
        u8 verify_data[TLS_VERIFY_DATA_LEN];
        u8 hash[MD5_MAC_LEN + SHA1_MAC_LEN];

        pos = *msgpos;

        wpa_printf(MSG_DEBUG, "TLSv1: Send Finished");

        /* Encrypted Handshake Message: Finished */

        hlen = MD5_MAC_LEN;
        if (conn->verify.md5_server == NULL ||
            crypto_hash_finish(conn->verify.md5_server, hash, &hlen) < 0) {
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                conn->verify.md5_server = NULL;
                crypto_hash_finish(conn->verify.sha1_server, NULL, NULL);
                conn->verify.sha1_server = NULL;
                return -1;
        }
        conn->verify.md5_server = NULL;
        hlen = SHA1_MAC_LEN;
        if (conn->verify.sha1_server == NULL ||
            crypto_hash_finish(conn->verify.sha1_server, hash + MD5_MAC_LEN,
                               &hlen) < 0) {
                conn->verify.sha1_server = NULL;
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        conn->verify.sha1_server = NULL;

        if (tls_prf(conn->master_secret, TLS_MASTER_SECRET_LEN,
                    "server finished", hash, MD5_MAC_LEN + SHA1_MAC_LEN,
                    verify_data, TLS_VERIFY_DATA_LEN)) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to generate verify_data");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        wpa_hexdump_key(MSG_DEBUG, "TLSv1: verify_data (server)",
                        verify_data, TLS_VERIFY_DATA_LEN);

        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;
        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_FINISHED;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        os_memcpy(pos, verify_data, TLS_VERIFY_DATA_LEN);
        pos += TLS_VERIFY_DATA_LEN;
        WPA_PUT_BE24(hs_length, pos - hs_length - 3);
        tls_verify_hash_add(&conn->verify, hs_start, pos - hs_start);

        if (tlsv1_record_send(&conn->rl, TLS_CONTENT_TYPE_HANDSHAKE,
                              rhdr, end - rhdr, pos - hs_start, &rlen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to create a record");
                tlsv1_server_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                   TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }

        pos = rhdr + rlen;

        *msgpos = pos;

        return 0;
}


static u8 * tls_send_server_hello(struct tlsv1_server *conn, size_t *out_len)
{
        u8 *msg, *end, *pos;
        size_t msglen;

        *out_len = 0;

        msglen = 1000 + tls_server_cert_chain_der_len(conn);

        msg = os_malloc(msglen);
        if (msg == NULL)
                return NULL;

        pos = msg;
        end = msg + msglen;

        if (tls_write_server_hello(conn, &pos, end) < 0) {
                os_free(msg);
                return NULL;
        }

        if (conn->use_session_ticket) {
                /* Abbreviated handshake using session ticket; RFC 4507 */
                if (tls_write_server_change_cipher_spec(conn, &pos, end) < 0 ||
                    tls_write_server_finished(conn, &pos, end) < 0) {
                        os_free(msg);
                        return NULL;
                }

                *out_len = pos - msg;

                conn->state = CHANGE_CIPHER_SPEC;

                return msg;
        }

        /* Full handshake */
        if (tls_write_server_certificate(conn, &pos, end) < 0 ||
            tls_write_server_key_exchange(conn, &pos, end) < 0 ||
            tls_write_server_certificate_request(conn, &pos, end) < 0 ||
            tls_write_server_hello_done(conn, &pos, end) < 0) {
                os_free(msg);
                return NULL;
        }

        *out_len = pos - msg;

        conn->state = CLIENT_CERTIFICATE;

        return msg;
}


static u8 * tls_send_change_cipher_spec(struct tlsv1_server *conn,
                                        size_t *out_len)
{
        u8 *msg, *end, *pos;

        *out_len = 0;

        msg = os_malloc(1000);
        if (msg == NULL)
                return NULL;

        pos = msg;
        end = msg + 1000;

        if (tls_write_server_change_cipher_spec(conn, &pos, end) < 0 ||
            tls_write_server_finished(conn, &pos, end) < 0) {
                os_free(msg);
                return NULL;
        }

        *out_len = pos - msg;

        wpa_printf(MSG_DEBUG, "TLSv1: Handshake completed successfully");
        conn->state = ESTABLISHED;

        return msg;
}


u8 * tlsv1_server_handshake_write(struct tlsv1_server *conn, size_t *out_len)
{
        switch (conn->state) {
        case SERVER_HELLO:
                return tls_send_server_hello(conn, out_len);
        case SERVER_CHANGE_CIPHER_SPEC:
                return tls_send_change_cipher_spec(conn, out_len);
        default:
                if (conn->state == ESTABLISHED && conn->use_session_ticket) {
                        /* Abbreviated handshake was already completed. */
                        return NULL;
                }
                wpa_printf(MSG_DEBUG, "TLSv1: Unexpected state %d while "
                           "generating reply", conn->state);
                return NULL;
        }
}


u8 * tlsv1_server_send_alert(struct tlsv1_server *conn, u8 level,
                             u8 description, size_t *out_len)
{
        u8 *alert, *pos, *length;

        wpa_printf(MSG_DEBUG, "TLSv1: Send Alert(%d:%d)", level, description);
        *out_len = 0;

        alert = os_malloc(10);
        if (alert == NULL)
                return NULL;

        pos = alert;

        /* TLSPlaintext */
        /* ContentType type */
        *pos++ = TLS_CONTENT_TYPE_ALERT;
        /* ProtocolVersion version */
        WPA_PUT_BE16(pos, TLS_VERSION);
        pos += 2;
        /* uint16 length (to be filled) */
        length = pos;
        pos += 2;
        /* opaque fragment[TLSPlaintext.length] */

        /* Alert */
        /* AlertLevel level */
        *pos++ = level;
        /* AlertDescription description */
        *pos++ = description;

        WPA_PUT_BE16(length, pos - length - 2);
        *out_len = pos - alert;

        return alert;
}