tlsv1_client_write.c

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#include "includes.h"

#include "common.h"
#include "md5.h"
#include "sha1.h"
#include "x509v3.h"
#include "tls.h"
#include "tlsv1_common.h"
#include "tlsv1_record.h"
#include "tlsv1_client.h"
#include "tlsv1_client_i.h"


static size_t tls_client_cert_chain_der_len(struct tlsv1_client *conn)
{
        size_t len = 0;
        struct x509_certificate *cert;

        if (conn->cred == NULL)
                return 0;

        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;
}


u8 * tls_send_client_hello(struct tlsv1_client *conn, size_t *out_len)
{
        u8 *hello, *end, *pos, *hs_length, *hs_start, *rhdr;
        struct os_time now;
        size_t len, i;

        wpa_printf(MSG_DEBUG, "TLSv1: Send ClientHello");
        *out_len = 0;

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

        len = 100 + conn->num_cipher_suites * 2 + conn->client_hello_ext_len;
        hello = os_malloc(len);
        if (hello == NULL)
                return NULL;
        end = hello + len;

        rhdr = hello;
        pos = rhdr + TLS_RECORD_HEADER_LEN;

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_CLIENT_HELLO;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        /* body - ClientHello */
        /* ProtocolVersion client_version */
        WPA_PUT_BE16(pos, TLS_VERSION);
        pos += 2;
        /* Random random: uint32 gmt_unix_time, opaque random_bytes */
        os_memcpy(pos, conn->client_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_suites<2..2^16-1> */
        WPA_PUT_BE16(pos, 2 * conn->num_cipher_suites);
        pos += 2;
        for (i = 0; i < conn->num_cipher_suites; i++) {
                WPA_PUT_BE16(pos, conn->cipher_suites[i]);
                pos += 2;
        }
        /* CompressionMethod compression_methods<1..2^8-1> */
        *pos++ = 1;
        *pos++ = TLS_COMPRESSION_NULL;

        if (conn->client_hello_ext) {
                os_memcpy(pos, conn->client_hello_ext,
                          conn->client_hello_ext_len);
                pos += conn->client_hello_ext_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, out_len) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to create TLS record");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(hello);
                return NULL;
        }

        conn->state = SERVER_HELLO;

        return hello;
}


static int tls_write_client_certificate(struct tlsv1_client *conn,
                                        u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length, *cert_start;
        size_t rlen;
        struct x509_certificate *cert;

        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 ? conn->cred->cert : NULL;
        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));
                        tls_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 (conn->cred == NULL || cert == conn->cred->cert || cert == NULL) {
                /*
                 * Client was not configured with all the needed certificates
                 * to form a full certificate chain. The server may fail to
                 * validate the chain unless it is configured with all the
                 * missing CA certificates.
                 */
                wpa_printf(MSG_DEBUG, "TLSv1: Full client 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");
                tls_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 tlsv1_key_x_anon_dh(struct tlsv1_client *conn, u8 **pos, u8 *end)
{
#ifdef EAP_FAST
        /* ClientDiffieHellmanPublic */
        u8 *csecret, *csecret_start, *dh_yc, *shared;
        size_t csecret_len, dh_yc_len, shared_len;

        csecret_len = conn->dh_p_len;
        csecret = os_malloc(csecret_len);
        if (csecret == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to allocate "
                           "memory for Yc (Diffie-Hellman)");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        if (os_get_random(csecret, csecret_len)) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to get random "
                           "data for Diffie-Hellman");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(csecret);
                return -1;
        }

        if (os_memcmp(csecret, conn->dh_p, csecret_len) > 0)
                csecret[0] = 0; /* make sure Yc < p */

        csecret_start = csecret;
        while (csecret_len > 1 && *csecret_start == 0) {
                csecret_start++;
                csecret_len--;
        }
        wpa_hexdump_key(MSG_DEBUG, "TLSv1: DH client's secret value",
                        csecret_start, csecret_len);

        /* Yc = g^csecret mod p */
        dh_yc_len = conn->dh_p_len;
        dh_yc = os_malloc(dh_yc_len);
        if (dh_yc == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to allocate "
                           "memory for Diffie-Hellman");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(csecret);
                return -1;
        }
        if (crypto_mod_exp(conn->dh_g, conn->dh_g_len,
                           csecret_start, csecret_len,
                           conn->dh_p, conn->dh_p_len,
                           dh_yc, &dh_yc_len)) {
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(csecret);
                os_free(dh_yc);
                return -1;
        }

        wpa_hexdump(MSG_DEBUG, "TLSv1: DH Yc (client's public value)",
                    dh_yc, dh_yc_len);

        WPA_PUT_BE16(*pos, dh_yc_len);
        *pos += 2;
        if (*pos + dh_yc_len > end) {
                wpa_printf(MSG_DEBUG, "TLSv1: Not enough room in the "
                           "message buffer for Yc");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(csecret);
                os_free(dh_yc);
                return -1;
        }
        os_memcpy(*pos, dh_yc, dh_yc_len);
        *pos += dh_yc_len;
        os_free(dh_yc);

        shared_len = conn->dh_p_len;
        shared = os_malloc(shared_len);
        if (shared == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: Could not allocate memory for "
                           "DH");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(csecret);
                return -1;
        }

        /* shared = Ys^csecret mod p */
        if (crypto_mod_exp(conn->dh_ys, conn->dh_ys_len,
                           csecret_start, csecret_len,
                           conn->dh_p, conn->dh_p_len,
                           shared, &shared_len)) {
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(csecret);
                os_free(shared);
                return -1;
        }
        wpa_hexdump_key(MSG_DEBUG, "TLSv1: Shared secret from DH key exchange",
                        shared, shared_len);

        os_memset(csecret_start, 0, csecret_len);
        os_free(csecret);
        if (tls_derive_keys(conn, shared, shared_len)) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to derive keys");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                os_free(shared);
                return -1;
        }
        os_memset(shared, 0, shared_len);
        os_free(shared);
        tlsv1_client_free_dh(conn);
        return 0;
#else /* EAP_FAST */
        tls_alert(conn, TLS_ALERT_LEVEL_FATAL, TLS_ALERT_INTERNAL_ERROR);
        return -1;
#endif /* EAP_FAST */
}


static int tlsv1_key_x_rsa(struct tlsv1_client *conn, u8 **pos, u8 *end)
{
        u8 pre_master_secret[TLS_PRE_MASTER_SECRET_LEN];
        size_t clen;
        int res;

        if (tls_derive_pre_master_secret(pre_master_secret) < 0 ||
            tls_derive_keys(conn, pre_master_secret,
                            TLS_PRE_MASTER_SECRET_LEN)) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to derive keys");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }

        /* EncryptedPreMasterSecret */
        if (conn->server_rsa_key == NULL) {
                wpa_printf(MSG_DEBUG, "TLSv1: No server RSA key to "
                           "use for encrypting pre-master secret");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }

        /* RSA encrypted value is encoded with PKCS #1 v1.5 block type 2. */
        *pos += 2;
        clen = end - *pos;
        res = crypto_public_key_encrypt_pkcs1_v15(
                conn->server_rsa_key,
                pre_master_secret, TLS_PRE_MASTER_SECRET_LEN,
                *pos, &clen);
        os_memset(pre_master_secret, 0, TLS_PRE_MASTER_SECRET_LEN);
        if (res < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: RSA encryption failed");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        WPA_PUT_BE16(*pos - 2, clen);
        wpa_hexdump(MSG_MSGDUMP, "TLSv1: Encrypted pre_master_secret",
                    *pos, clen);
        *pos += clen;

        return 0;
}


static int tls_write_client_key_exchange(struct tlsv1_client *conn,
                                         u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length;
        size_t rlen;
        tls_key_exchange keyx;
        const struct tls_cipher_suite *suite;

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

        pos = *msgpos;

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

        rhdr = pos;
        pos += TLS_RECORD_HEADER_LEN;

        /* opaque fragment[TLSPlaintext.length] */

        /* Handshake */
        hs_start = pos;
        /* HandshakeType msg_type */
        *pos++ = TLS_HANDSHAKE_TYPE_CLIENT_KEY_EXCHANGE;
        /* uint24 length (to be filled) */
        hs_length = pos;
        pos += 3;
        /* body - ClientKeyExchange */
        if (keyx == TLS_KEY_X_DH_anon) {
                if (tlsv1_key_x_anon_dh(conn, &pos, end) < 0)
                        return -1;
        } else {
                if (tlsv1_key_x_rsa(conn, &pos, end) < 0)
                        return -1;
        }

        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 create a record");
                tls_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_client_certificate_verify(struct tlsv1_client *conn,
                                               u8 **msgpos, u8 *end)
{
        u8 *pos, *rhdr, *hs_start, *hs_length, *signed_start;
        size_t rlen, hlen, clen;
        u8 hash[MD5_MAC_LEN + SHA1_MAC_LEN], *hpos;
        enum { SIGN_ALG_RSA, SIGN_ALG_DSA } alg = SIGN_ALG_RSA;

        pos = *msgpos;

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

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

        /*
         * RFC 2246: 7.4.3 and 7.4.8:
         * Signature signature
         *
         * RSA:
         * digitally-signed struct {
         *     opaque md5_hash[16];
         *     opaque sha_hash[20];
         * };
         *
         * DSA:
         * digitally-signed struct {
         *     opaque sha_hash[20];
         * };
         *
         * The hash values are calculated over all handshake messages sent or
         * received starting at ClientHello up to, but not including, this
         * CertificateVerify message, including the type and length fields of
         * the handshake messages.
         */

        hpos = hash;

        if (alg == SIGN_ALG_RSA) {
                hlen = MD5_MAC_LEN;
                if (conn->verify.md5_cert == NULL ||
                    crypto_hash_finish(conn->verify.md5_cert, hpos, &hlen) < 0)
                {
                        tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                                  TLS_ALERT_INTERNAL_ERROR);
                        conn->verify.md5_cert = NULL;
                        crypto_hash_finish(conn->verify.sha1_cert, NULL, NULL);
                        conn->verify.sha1_cert = NULL;
                        return -1;
                }
                hpos += MD5_MAC_LEN;
        } else
                crypto_hash_finish(conn->verify.md5_cert, NULL, NULL);

        conn->verify.md5_cert = NULL;
        hlen = SHA1_MAC_LEN;
        if (conn->verify.sha1_cert == NULL ||
            crypto_hash_finish(conn->verify.sha1_cert, hpos, &hlen) < 0) {
                conn->verify.sha1_cert = NULL;
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        conn->verify.sha1_cert = NULL;

        if (alg == SIGN_ALG_RSA)
                hlen += MD5_MAC_LEN;

        wpa_hexdump(MSG_MSGDUMP, "TLSv1: CertificateVerify hash", hash, hlen);

        /*
         * RFC 2246, 4.7:
         * In digital signing, one-way hash functions are used as input for a
         * signing algorithm. A digitally-signed element is encoded as an
         * opaque vector <0..2^16-1>, where the length is specified by the
         * signing algorithm and key.
         *
         * In RSA signing, a 36-byte structure of two hashes (one SHA and one
         * MD5) is signed (encrypted with the private key). It is encoded with
         * PKCS #1 block type 0 or type 1 as described in [PKCS1].
         */
        signed_start = pos; /* length to be filled */
        pos += 2;
        clen = end - pos;
        if (conn->cred == NULL ||
            crypto_private_key_sign_pkcs1(conn->cred->key, hash, hlen,
                                          pos, &clen) < 0) {
                wpa_printf(MSG_DEBUG, "TLSv1: Failed to sign hash (PKCS #1)");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        WPA_PUT_BE16(signed_start, clen);

        pos += clen;

        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");
                tls_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_client_change_cipher_spec(struct tlsv1_client *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");
                tls_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");
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }

        *msgpos = rhdr + rlen;

        return 0;
}


static int tls_write_client_finished(struct tlsv1_client *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_client == NULL ||
            crypto_hash_finish(conn->verify.md5_client, hash, &hlen) < 0) {
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                conn->verify.md5_client = NULL;
                crypto_hash_finish(conn->verify.sha1_client, NULL, NULL);
                conn->verify.sha1_client = NULL;
                return -1;
        }
        conn->verify.md5_client = NULL;
        hlen = SHA1_MAC_LEN;
        if (conn->verify.sha1_client == NULL ||
            crypto_hash_finish(conn->verify.sha1_client, hash + MD5_MAC_LEN,
                               &hlen) < 0) {
                conn->verify.sha1_client = NULL;
                tls_alert(conn, TLS_ALERT_LEVEL_FATAL,
                          TLS_ALERT_INTERNAL_ERROR);
                return -1;
        }
        conn->verify.sha1_client = NULL;

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

        pos = rhdr + rlen;

        *msgpos = pos;

        return 0;
}


static u8 * tls_send_client_key_exchange(struct tlsv1_client *conn,
                                         size_t *out_len)
{
        u8 *msg, *end, *pos;
        size_t msglen;

        *out_len = 0;

        msglen = 1000;
        if (conn->certificate_requested)
                msglen += tls_client_cert_chain_der_len(conn);

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

        pos = msg;
        end = msg + msglen;

        if (conn->certificate_requested) {
                if (tls_write_client_certificate(conn, &pos, end) < 0) {
                        os_free(msg);
                        return NULL;
                }
        }

        if (tls_write_client_key_exchange(conn, &pos, end) < 0 ||
            (conn->certificate_requested && conn->cred && conn->cred->key &&
             tls_write_client_certificate_verify(conn, &pos, end) < 0) ||
            tls_write_client_change_cipher_spec(conn, &pos, end) < 0 ||
            tls_write_client_finished(conn, &pos, end) < 0) {
                os_free(msg);
                return NULL;
        }

        *out_len = pos - msg;

        conn->state = SERVER_CHANGE_CIPHER_SPEC;

        return msg;
}


static u8 * tls_send_change_cipher_spec(struct tlsv1_client *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_client_change_cipher_spec(conn, &pos, end) < 0 ||
            tls_write_client_finished(conn, &pos, end) < 0) {
                os_free(msg);
                return NULL;
        }

        *out_len = pos - msg;

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

        return msg;
}


u8 * tlsv1_client_handshake_write(struct tlsv1_client *conn, size_t *out_len,
                                  int no_appl_data)
{
        switch (conn->state) {
        case CLIENT_KEY_EXCHANGE:
                return tls_send_client_key_exchange(conn, out_len);
        case CHANGE_CIPHER_SPEC:
                return tls_send_change_cipher_spec(conn, out_len);
        case ACK_FINISHED:
                wpa_printf(MSG_DEBUG, "TLSv1: Handshake completed "
                           "successfully");
                conn->state = ESTABLISHED;
                *out_len = 0;
                if (no_appl_data) {
                        /* Need to return something to get final TLS ACK. */
                        return os_malloc(1);
                }
                return NULL;
        default:
                wpa_printf(MSG_DEBUG, "TLSv1: Unexpected state %d while "
                           "generating reply", conn->state);
                return NULL;
        }
}


u8 * tlsv1_client_send_alert(struct tlsv1_client *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;
}