path: root/crypto/openssl/ssl/s2_srvr.c

/* ssl/s2_srvr.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */
/* ====================================================================
 * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include "ssl_locl.h"
#ifndef OPENSSL_NO_SSL2
#include "../crypto/constant_time_locl.h"
# include <stdio.h>
# include <openssl/bio.h>
# include <openssl/rand.h>
# include <openssl/objects.h>
# include <openssl/evp.h>

static const SSL_METHOD *ssl2_get_server_method(int ver);
static int get_client_master_key(SSL *s);
static int get_client_hello(SSL *s);
static int server_hello(SSL *s);
static int get_client_finished(SSL *s);
static int server_verify(SSL *s);
static int server_finish(SSL *s);
static int request_certificate(SSL *s);
static int ssl_rsa_private_decrypt(CERT *c, int len, unsigned char *from,
                                   unsigned char *to, int padding);
# define BREAK   break

static const SSL_METHOD *ssl2_get_server_method(int ver)
{
    if (ver == SSL2_VERSION)
        return (SSLv2_server_method());
    else
        return (NULL);
}

IMPLEMENT_ssl2_meth_func(SSLv2_server_method,
                         ssl2_accept,
                         ssl_undefined_function, ssl2_get_server_method)

int ssl2_accept(SSL *s)
{
    unsigned long l = (unsigned long)time(NULL);
    BUF_MEM *buf = NULL;
    int ret = -1;
    long num1;
    void (*cb) (const SSL *ssl, int type, int val) = NULL;
    int new_state, state;

    RAND_add(&l, sizeof(l), 0);
    ERR_clear_error();
    clear_sys_error();

    if (s->info_callback != NULL)
        cb = s->info_callback;
    else if (s->ctx->info_callback != NULL)
        cb = s->ctx->info_callback;

    /* init things to blank */
    s->in_handshake++;
    if (!SSL_in_init(s) || SSL_in_before(s))
        SSL_clear(s);

    if (s->cert == NULL) {
        SSLerr(SSL_F_SSL2_ACCEPT, SSL_R_NO_CERTIFICATE_SET);
        return (-1);
    }

    clear_sys_error();
    for (;;) {
        state = s->state;

        switch (s->state) {
        case SSL_ST_BEFORE:
        case SSL_ST_ACCEPT:
        case SSL_ST_BEFORE | SSL_ST_ACCEPT:
        case SSL_ST_OK | SSL_ST_ACCEPT:

            s->server = 1;
            if (cb != NULL)
                cb(s, SSL_CB_HANDSHAKE_START, 1);

            s->version = SSL2_VERSION;
            s->type = SSL_ST_ACCEPT;

            if (s->init_buf == NULL) {
                if ((buf = BUF_MEM_new()) == NULL) {
                    ret = -1;
                    goto end;
                }
                if (!BUF_MEM_grow
                    (buf, (int)SSL2_MAX_RECORD_LENGTH_3_BYTE_HEADER)) {
                    BUF_MEM_free(buf);
                    ret = -1;
                    goto end;
                }
                s->init_buf = buf;
            }
            s->init_num = 0;
            s->ctx->stats.sess_accept++;
            s->handshake_func = ssl2_accept;
            s->state = SSL2_ST_GET_CLIENT_HELLO_A;
            BREAK;

        case SSL2_ST_GET_CLIENT_HELLO_A:
        case SSL2_ST_GET_CLIENT_HELLO_B:
        case SSL2_ST_GET_CLIENT_HELLO_C:
            s->shutdown = 0;
            ret = get_client_hello(s);
            if (ret <= 0)
                goto end;
            s->init_num = 0;
            s->state = SSL2_ST_SEND_SERVER_HELLO_A;
            BREAK;

        case SSL2_ST_SEND_SERVER_HELLO_A:
        case SSL2_ST_SEND_SERVER_HELLO_B:
            ret = server_hello(s);
            if (ret <= 0)
                goto end;
            s->init_num = 0;
            if (!s->hit) {
                s->state = SSL2_ST_GET_CLIENT_MASTER_KEY_A;
                BREAK;
            } else {
                s->state = SSL2_ST_SERVER_START_ENCRYPTION;
                BREAK;
            }
        case SSL2_ST_GET_CLIENT_MASTER_KEY_A:
        case SSL2_ST_GET_CLIENT_MASTER_KEY_B:
            ret = get_client_master_key(s);
            if (ret <= 0)
                goto end;
            s->init_num = 0;
            s->state = SSL2_ST_SERVER_START_ENCRYPTION;
            BREAK;

        case SSL2_ST_SERVER_START_ENCRYPTION:
            /*
             * Ok we how have sent all the stuff needed to start encrypting,
             * the next packet back will be encrypted.
             */
            if (!ssl2_enc_init(s, 0)) {
                ret = -1;
                goto end;
            }
            s->s2->clear_text = 0;
            s->state = SSL2_ST_SEND_SERVER_VERIFY_A;
            BREAK;

        case SSL2_ST_SEND_SERVER_VERIFY_A:
        case SSL2_ST_SEND_SERVER_VERIFY_B:
            ret = server_verify(s);
            if (ret <= 0)
                goto end;
            s->init_num = 0;
            if (s->hit) {
                /*
                 * If we are in here, we have been buffering the output, so
                 * we need to flush it and remove buffering from future
                 * traffic
                 */
                s->state = SSL2_ST_SEND_SERVER_VERIFY_C;
                BREAK;
            } else {
                s->state = SSL2_ST_GET_CLIENT_FINISHED_A;
                break;
            }

        case SSL2_ST_SEND_SERVER_VERIFY_C:
            /* get the number of bytes to write */
            num1 = BIO_ctrl(s->wbio, BIO_CTRL_INFO, 0, NULL);
            if (num1 > 0) {
                s->rwstate = SSL_WRITING;
                num1 = BIO_flush(s->wbio);
                if (num1 <= 0) {
                    ret = -1;
                    goto end;
                }
                s->rwstate = SSL_NOTHING;
            }

            /* flushed and now remove buffering */
            s->wbio = BIO_pop(s->wbio);

            s->state = SSL2_ST_GET_CLIENT_FINISHED_A;
            BREAK;

        case SSL2_ST_GET_CLIENT_FINISHED_A:
        case SSL2_ST_GET_CLIENT_FINISHED_B:
            ret = get_client_finished(s);
            if (ret <= 0)
                goto end;
            s->init_num = 0;
            s->state = SSL2_ST_SEND_REQUEST_CERTIFICATE_A;
            BREAK;

        case SSL2_ST_SEND_REQUEST_CERTIFICATE_A:
        case SSL2_ST_SEND_REQUEST_CERTIFICATE_B:
        case SSL2_ST_SEND_REQUEST_CERTIFICATE_C:
        case SSL2_ST_SEND_REQUEST_CERTIFICATE_D:
            /*
             * don't do a 'request certificate' if we don't want to, or we
             * already have one, and we only want to do it once.
             */
            if (!(s->verify_mode & SSL_VERIFY_PEER) ||
                ((s->session->peer != NULL) &&
                 (s->verify_mode & SSL_VERIFY_CLIENT_ONCE))) {
                s->state = SSL2_ST_SEND_SERVER_FINISHED_A;
                break;
            } else {
                ret = request_certificate(s);
                if (ret <= 0)
                    goto end;
                s->init_num = 0;
                s->state = SSL2_ST_SEND_SERVER_FINISHED_A;
            }
            BREAK;

        case SSL2_ST_SEND_SERVER_FINISHED_A:
        case SSL2_ST_SEND_SERVER_FINISHED_B:
            ret = server_finish(s);
            if (ret <= 0)
                goto end;
            s->init_num = 0;
            s->state = SSL_ST_OK;
            break;

        case SSL_ST_OK:
            BUF_MEM_free(s->init_buf);
            ssl_free_wbio_buffer(s);
            s->init_buf = NULL;
            s->init_num = 0;
            /*      ERR_clear_error(); */

            ssl_update_cache(s, SSL_SESS_CACHE_SERVER);

            s->ctx->stats.sess_accept_good++;
            /* s->server=1; */
            ret = 1;

            if (cb != NULL)
                cb(s, SSL_CB_HANDSHAKE_DONE, 1);

            goto end;
            /* BREAK; */

        default:
            SSLerr(SSL_F_SSL2_ACCEPT, SSL_R_UNKNOWN_STATE);
            ret = -1;
            goto end;
            /* BREAK; */
        }

        if ((cb != NULL) && (s->state != state)) {
            new_state = s->state;
            s->state = state;
            cb(s, SSL_CB_ACCEPT_LOOP, 1);
            s->state = new_state;
        }
    }
 end:
    s->in_handshake--;
    if (cb != NULL)
        cb(s, SSL_CB_ACCEPT_EXIT, ret);
    return (ret);
}

static int get_client_master_key(SSL *s)
{
    int is_export, i, n, keya;
    unsigned int num_encrypted_key_bytes, key_length;
    unsigned long len;
    unsigned char *p;
    const SSL_CIPHER *cp;
    const EVP_CIPHER *c;
    const EVP_MD *md;
    unsigned char rand_premaster_secret[SSL_MAX_MASTER_KEY_LENGTH];
    unsigned char decrypt_good;
    size_t j;

    p = (unsigned char *)s->init_buf->data;
    if (s->state == SSL2_ST_GET_CLIENT_MASTER_KEY_A) {
        i = ssl2_read(s, (char *)&(p[s->init_num]), 10 - s->init_num);

        if (i < (10 - s->init_num))
            return (ssl2_part_read(s, SSL_F_GET_CLIENT_MASTER_KEY, i));
        s->init_num = 10;

        if (*(p++) != SSL2_MT_CLIENT_MASTER_KEY) {
            if (p[-1] != SSL2_MT_ERROR) {
                ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
                SSLerr(SSL_F_GET_CLIENT_MASTER_KEY,
                       SSL_R_READ_WRONG_PACKET_TYPE);
            } else
                SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, SSL_R_PEER_ERROR);
            return (-1);
        }

        cp = ssl2_get_cipher_by_char(p);
        if (cp == NULL || sk_SSL_CIPHER_find(s->session->ciphers, cp) < 0) {
            ssl2_return_error(s, SSL2_PE_NO_CIPHER);
            SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, SSL_R_NO_CIPHER_MATCH);
            return (-1);
        }
        s->session->cipher = cp;

        p += 3;
        n2s(p, i);
        s->s2->tmp.clear = i;
        n2s(p, i);
        s->s2->tmp.enc = i;
        n2s(p, i);
        if (i > SSL_MAX_KEY_ARG_LENGTH) {
            ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
            SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, SSL_R_KEY_ARG_TOO_LONG);
            return -1;
        }
        s->session->key_arg_length = i;
        s->state = SSL2_ST_GET_CLIENT_MASTER_KEY_B;
    }

    /* SSL2_ST_GET_CLIENT_MASTER_KEY_B */
    p = (unsigned char *)s->init_buf->data;
    if (s->init_buf->length < SSL2_MAX_RECORD_LENGTH_3_BYTE_HEADER) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, ERR_R_INTERNAL_ERROR);
        return -1;
    }
    keya = s->session->key_arg_length;
    len =
        10 + (unsigned long)s->s2->tmp.clear + (unsigned long)s->s2->tmp.enc +
        (unsigned long)keya;
    if (len > SSL2_MAX_RECORD_LENGTH_3_BYTE_HEADER) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, SSL_R_MESSAGE_TOO_LONG);
        return -1;
    }
    n = (int)len - s->init_num;
    i = ssl2_read(s, (char *)&(p[s->init_num]), n);
    if (i != n)
        return (ssl2_part_read(s, SSL_F_GET_CLIENT_MASTER_KEY, i));
    if (s->msg_callback) {
        /* CLIENT-MASTER-KEY */
        s->msg_callback(0, s->version, 0, p, (size_t)len, s,
                        s->msg_callback_arg);
    }
    p += 10;

    memcpy(s->session->key_arg, &(p[s->s2->tmp.clear + s->s2->tmp.enc]),
           (unsigned int)keya);

    if (s->cert->pkeys[SSL_PKEY_RSA_ENC].privatekey == NULL) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, SSL_R_NO_PRIVATEKEY);
        return (-1);
    }

    is_export = SSL_C_IS_EXPORT(s->session->cipher);

    if (!ssl_cipher_get_evp(s->session, &c, &md, NULL, NULL, NULL)) {
        ssl2_return_error(s, SSL2_PE_NO_CIPHER);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY,
               SSL_R_PROBLEMS_MAPPING_CIPHER_FUNCTIONS);
        return (0);
    }

    /*
     * The format of the CLIENT-MASTER-KEY message is
     * 1 byte message type
     * 3 bytes cipher
     * 2-byte clear key length (stored in s->s2->tmp.clear)
     * 2-byte encrypted key length (stored in s->s2->tmp.enc)
     * 2-byte key args length (IV etc)
     * clear key
     * encrypted key
     * key args
     *
     * If the cipher is an export cipher, then the encrypted key bytes
     * are a fixed portion of the total key (5 or 8 bytes). The size of
     * this portion is in |num_encrypted_key_bytes|. If the cipher is not an
     * export cipher, then the entire key material is encrypted (i.e., clear
     * key length must be zero).
     */
    key_length = (unsigned int)EVP_CIPHER_key_length(c);
    if (key_length > SSL_MAX_MASTER_KEY_LENGTH) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY, ERR_R_INTERNAL_ERROR);
        return -1;
    }

    if (s->session->cipher->algorithm2 & SSL2_CF_8_BYTE_ENC) {
        is_export = 1;
        num_encrypted_key_bytes = 8;
    } else if (is_export) {
        num_encrypted_key_bytes = 5;
    } else {
        num_encrypted_key_bytes = key_length;
    }

    if (s->s2->tmp.clear + num_encrypted_key_bytes != key_length) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY,SSL_R_BAD_LENGTH);
        return -1;
    }
    /*
     * The encrypted blob must decrypt to the encrypted portion of the key.
     * Decryption can't be expanding, so if we don't have enough encrypted
     * bytes to fit the key in the buffer, stop now.
     */
    if (s->s2->tmp.enc < num_encrypted_key_bytes) {
        ssl2_return_error(s,SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_MASTER_KEY,SSL_R_LENGTH_TOO_SHORT);
        return -1;
    }

    /*
     * We must not leak whether a decryption failure occurs because of
     * Bleichenbacher's attack on PKCS #1 v1.5 RSA padding (see RFC 2246,
     * section 7.4.7.1). The code follows that advice of the TLS RFC and
     * generates a random premaster secret for the case that the decrypt
     * fails. See https://tools.ietf.org/html/rfc5246#section-7.4.7.1
     */

    /*
     * should be RAND_bytes, but we cannot work around a failure.
     */
    if (RAND_pseudo_bytes(rand_premaster_secret,
                          (int)num_encrypted_key_bytes) <= 0)
        return 0;

    i = ssl_rsa_private_decrypt(s->cert, s->s2->tmp.enc,
                                &(p[s->s2->tmp.clear]),
                                &(p[s->s2->tmp.clear]),
                                (s->s2->ssl2_rollback) ? RSA_SSLV23_PADDING :
                                RSA_PKCS1_PADDING);
    ERR_clear_error();
    /*
     * If a bad decrypt, continue with protocol but with a random master
     * secret (Bleichenbacher attack)
     */
    decrypt_good = constant_time_eq_int_8(i, (int)num_encrypted_key_bytes);
    for (j = 0; j < num_encrypted_key_bytes; j++) {
        p[s->s2->tmp.clear + j] =
                constant_time_select_8(decrypt_good, p[s->s2->tmp.clear + j],
                                       rand_premaster_secret[j]);
    }

    s->session->master_key_length = (int)key_length;
    memcpy(s->session->master_key, p, key_length);
    OPENSSL_cleanse(p, key_length);

    return 1;
}

static int get_client_hello(SSL *s)
{
    int i, n;
    unsigned long len;
    unsigned char *p;
    STACK_OF(SSL_CIPHER) *cs;   /* a stack of SSL_CIPHERS */
    STACK_OF(SSL_CIPHER) *cl;   /* the ones we want to use */
    STACK_OF(SSL_CIPHER) *prio, *allow;
    int z;

    /*
     * This is a bit of a hack to check for the correct packet type the first
     * time round.
     */
    if (s->state == SSL2_ST_GET_CLIENT_HELLO_A) {
        s->first_packet = 1;
        s->state = SSL2_ST_GET_CLIENT_HELLO_B;
    }

    p = (unsigned char *)s->init_buf->data;
    if (s->state == SSL2_ST_GET_CLIENT_HELLO_B) {
        i = ssl2_read(s, (char *)&(p[s->init_num]), 9 - s->init_num);
        if (i < (9 - s->init_num))
            return (ssl2_part_read(s, SSL_F_GET_CLIENT_HELLO, i));
        s->init_num = 9;

        if (*(p++) != SSL2_MT_CLIENT_HELLO) {
            if (p[-1] != SSL2_MT_ERROR) {
                ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
                SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_READ_WRONG_PACKET_TYPE);
            } else
                SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_PEER_ERROR);
            return (-1);
        }
        n2s(p, i);
        if (i < s->version)
            s->version = i;
        n2s(p, i);
        s->s2->tmp.cipher_spec_length = i;
        n2s(p, i);
        s->s2->tmp.session_id_length = i;
        if ((i < 0) || (i > SSL_MAX_SSL_SESSION_ID_LENGTH)) {
            ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
            SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
            return -1;
        }
        n2s(p, i);
        s->s2->challenge_length = i;
        if ((i < SSL2_MIN_CHALLENGE_LENGTH) ||
            (i > SSL2_MAX_CHALLENGE_LENGTH)) {
            ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
            SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_INVALID_CHALLENGE_LENGTH);
            return (-1);
        }
        s->state = SSL2_ST_GET_CLIENT_HELLO_C;
    }

    /* SSL2_ST_GET_CLIENT_HELLO_C */
    p = (unsigned char *)s->init_buf->data;
    len =
        9 + (unsigned long)s->s2->tmp.cipher_spec_length +
        (unsigned long)s->s2->challenge_length +
        (unsigned long)s->s2->tmp.session_id_length;
    if (len > SSL2_MAX_RECORD_LENGTH_3_BYTE_HEADER) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_MESSAGE_TOO_LONG);
        return -1;
    }
    n = (int)len - s->init_num;
    i = ssl2_read(s, (char *)&(p[s->init_num]), n);
    if (i != n)
        return (ssl2_part_read(s, SSL_F_GET_CLIENT_HELLO, i));
    if (s->msg_callback) {
        /* CLIENT-HELLO */
        s->msg_callback(0, s->version, 0, p, (size_t)len, s,
                        s->msg_callback_arg);
    }
    p += 9;

    /*
     * get session-id before cipher stuff so we can get out session structure
     * if it is cached
     */
    /* session-id */
    if ((s->s2->tmp.session_id_length != 0) &&
        (s->s2->tmp.session_id_length != SSL2_SSL_SESSION_ID_LENGTH)) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_BAD_SSL_SESSION_ID_LENGTH);
        return (-1);
    }

    if (s->s2->tmp.session_id_length == 0) {
        if (!ssl_get_new_session(s, 1)) {
            ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
            return (-1);
        }
    } else {
        i = ssl_get_prev_session(s, &(p[s->s2->tmp.cipher_spec_length]),
                                 s->s2->tmp.session_id_length, NULL);
        if (i == 1) {           /* previous session */
            s->hit = 1;
        } else if (i == -1) {
            ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
            return (-1);
        } else {
            if (s->cert == NULL) {
                ssl2_return_error(s, SSL2_PE_NO_CERTIFICATE);
                SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_NO_CERTIFICATE_SET);
                return (-1);
            }

            if (!ssl_get_new_session(s, 1)) {
                ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
                return (-1);
            }
        }
    }

    if (!s->hit) {
        cs = ssl_bytes_to_cipher_list(s, p, s->s2->tmp.cipher_spec_length,
                                      &s->session->ciphers);
        if (cs == NULL)
            goto mem_err;

        cl = SSL_get_ciphers(s);

        if (s->options & SSL_OP_CIPHER_SERVER_PREFERENCE) {
            prio = sk_SSL_CIPHER_dup(cl);
            if (prio == NULL)
                goto mem_err;
            allow = cs;
        } else {
            prio = cs;
            allow = cl;
        }

        /* Generate list of SSLv2 ciphers shared between client and server */
        for (z = 0; z < sk_SSL_CIPHER_num(prio); z++) {
            const SSL_CIPHER *cp = sk_SSL_CIPHER_value(prio, z);
            if ((cp->algorithm_ssl & SSL_SSLV2) == 0 ||
                sk_SSL_CIPHER_find(allow, cp) < 0) {
                (void)sk_SSL_CIPHER_delete(prio, z);
                z--;
            }
        }
        if (s->options & SSL_OP_CIPHER_SERVER_PREFERENCE) {
            sk_SSL_CIPHER_free(s->session->ciphers);
            s->session->ciphers = prio;
        }

        /* Make sure we have at least one cipher in common */
        if (sk_SSL_CIPHER_num(s->session->ciphers) == 0) {
            ssl2_return_error(s, SSL2_PE_NO_CIPHER);
            SSLerr(SSL_F_GET_CLIENT_HELLO, SSL_R_NO_CIPHER_MATCH);
            return -1;
        }
        /*
         * s->session->ciphers should now have a list of ciphers that are on
         * both the client and server. This list is ordered by the order the
         * client sent the ciphers or in the order of the server's preference
         * if SSL_OP_CIPHER_SERVER_PREFERENCE was set.
         */
    }
    p += s->s2->tmp.cipher_spec_length;
    /* done cipher selection */

    /* session id extracted already */
    p += s->s2->tmp.session_id_length;

    /* challenge */
    if (s->s2->challenge_length > sizeof s->s2->challenge) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_HELLO, ERR_R_INTERNAL_ERROR);
        return -1;
    }
    memcpy(s->s2->challenge, p, (unsigned int)s->s2->challenge_length);
    return (1);
 mem_err:
    SSLerr(SSL_F_GET_CLIENT_HELLO, ERR_R_MALLOC_FAILURE);
    return (0);
}

static int server_hello(SSL *s)
{
    unsigned char *p, *d;
    int n, hit;

    p = (unsigned char *)s->init_buf->data;
    if (s->state == SSL2_ST_SEND_SERVER_HELLO_A) {
        d = p + 11;
        *(p++) = SSL2_MT_SERVER_HELLO; /* type */
        hit = s->hit;
        *(p++) = (unsigned char)hit;
# if 1
        if (!hit) {
            if (s->session->sess_cert != NULL)
                /*
                 * This can't really happen because get_client_hello has
                 * called ssl_get_new_session, which does not set sess_cert.
                 */
                ssl_sess_cert_free(s->session->sess_cert);
            s->session->sess_cert = ssl_sess_cert_new();
            if (s->session->sess_cert == NULL) {
                SSLerr(SSL_F_SERVER_HELLO, ERR_R_MALLOC_FAILURE);
                return (-1);
            }
        }
        /*
         * If 'hit' is set, then s->sess_cert may be non-NULL or NULL,
         * depending on whether it survived in the internal cache or was
         * retrieved from an external cache. If it is NULL, we cannot put any
         * useful data in it anyway, so we don't touch it.
         */

# else                          /* That's what used to be done when cert_st
                                 * and sess_cert_st were * the same. */
        if (!hit) {             /* else add cert to session */
            CRYPTO_add(&s->cert->references, 1, CRYPTO_LOCK_SSL_CERT);
            if (s->session->sess_cert != NULL)
                ssl_cert_free(s->session->sess_cert);
            s->session->sess_cert = s->cert;
        } else {                /* We have a session id-cache hit, if the *
                                 * session-id has no certificate listed
                                 * against * the 'cert' structure, grab the
                                 * 'old' one * listed against the SSL
                                 * connection */
            if (s->session->sess_cert == NULL) {
                CRYPTO_add(&s->cert->references, 1, CRYPTO_LOCK_SSL_CERT);
                s->session->sess_cert = s->cert;
            }
        }
# endif

        if (s->cert == NULL) {
            ssl2_return_error(s, SSL2_PE_NO_CERTIFICATE);
            SSLerr(SSL_F_SERVER_HELLO, SSL_R_NO_CERTIFICATE_SPECIFIED);
            return (-1);
        }

        if (hit) {
            *(p++) = 0;         /* no certificate type */
            s2n(s->version, p); /* version */
            s2n(0, p);          /* cert len */
            s2n(0, p);          /* ciphers len */
        } else {
            /* EAY EAY */
            /* put certificate type */
            *(p++) = SSL2_CT_X509_CERTIFICATE;
            s2n(s->version, p); /* version */
            n = i2d_X509(s->cert->pkeys[SSL_PKEY_RSA_ENC].x509, NULL);
            s2n(n, p);          /* certificate length */
            i2d_X509(s->cert->pkeys[SSL_PKEY_RSA_ENC].x509, &d);
            n = 0;

            /*
             * lets send out the ciphers we like in the prefered order
             */
            n = ssl_cipher_list_to_bytes(s, s->session->ciphers, d, 0);
            d += n;
            s2n(n, p);          /* add cipher length */
        }

        /* make and send conn_id */
        s2n(SSL2_CONNECTION_ID_LENGTH, p); /* add conn_id length */
        s->s2->conn_id_length = SSL2_CONNECTION_ID_LENGTH;
        if (RAND_pseudo_bytes(s->s2->conn_id, (int)s->s2->conn_id_length) <=
            0)
            return -1;
        memcpy(d, s->s2->conn_id, SSL2_CONNECTION_ID_LENGTH);
        d += SSL2_CONNECTION_ID_LENGTH;

        s->state = SSL2_ST_SEND_SERVER_HELLO_B;
        s->init_num = d - (unsigned char *)s->init_buf->data;
        s->init_off = 0;
    }
    /* SSL2_ST_SEND_SERVER_HELLO_B */
    /*
     * If we are using TCP/IP, the performance is bad if we do 2 writes
     * without a read between them.  This occurs when Session-id reuse is
     * used, so I will put in a buffering module
     */
    if (s->hit) {
        if (!ssl_init_wbio_buffer(s, 1))
            return (-1);
    }

    return (ssl2_do_write(s));
}

static int get_client_finished(SSL *s)
{
    unsigned char *p;
    int i, n;
    unsigned long len;

    p = (unsigned char *)s->init_buf->data;
    if (s->state == SSL2_ST_GET_CLIENT_FINISHED_A) {
        i = ssl2_read(s, (char *)&(p[s->init_num]), 1 - s->init_num);
        if (i < 1 - s->init_num)
            return (ssl2_part_read(s, SSL_F_GET_CLIENT_FINISHED, i));
        s->init_num += i;

        if (*p != SSL2_MT_CLIENT_FINISHED) {
            if (*p != SSL2_MT_ERROR) {
                ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
                SSLerr(SSL_F_GET_CLIENT_FINISHED,
                       SSL_R_READ_WRONG_PACKET_TYPE);
            } else {
                SSLerr(SSL_F_GET_CLIENT_FINISHED, SSL_R_PEER_ERROR);
                /* try to read the error message */
                i = ssl2_read(s, (char *)&(p[s->init_num]), 3 - s->init_num);
                return ssl2_part_read(s, SSL_F_GET_SERVER_VERIFY, i);
            }
            return (-1);
        }
        s->state = SSL2_ST_GET_CLIENT_FINISHED_B;
    }

    /* SSL2_ST_GET_CLIENT_FINISHED_B */
    if (s->s2->conn_id_length > sizeof s->s2->conn_id) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_FINISHED, ERR_R_INTERNAL_ERROR);
        return -1;
    }
    len = 1 + (unsigned long)s->s2->conn_id_length;
    n = (int)len - s->init_num;
    i = ssl2_read(s, (char *)&(p[s->init_num]), n);
    if (i < n) {
        return (ssl2_part_read(s, SSL_F_GET_CLIENT_FINISHED, i));
    }
    if (s->msg_callback) {
        /* CLIENT-FINISHED */
        s->msg_callback(0, s->version, 0, p, len, s, s->msg_callback_arg);
    }
    p += 1;
    if (memcmp(p, s->s2->conn_id, s->s2->conn_id_length) != 0) {
        ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
        SSLerr(SSL_F_GET_CLIENT_FINISHED, SSL_R_CONNECTION_ID_IS_DIFFERENT);
        return (-1);
    }
    return (1);
}

static int server_verify(SSL *s)
{
    unsigned char *p;

    if (s->state == SSL2_ST_SEND_SERVER_VERIFY_A) {
        p = (unsigned char *)s->init_buf->data;
        *(p++) = SSL2_MT_SERVER_VERIFY;
        if (s->s2->challenge_length > sizeof s->s2->challenge) {
            SSLerr(SSL_F_SERVER_VERIFY, ERR_R_INTERNAL_ERROR);
            return -1;
        }
        memcpy(p, s->s2->challenge, (unsigned int)s->s2->challenge_length);
        /* p+=s->s2->challenge_length; */

        s->state = SSL2_ST_SEND_SERVER_VERIFY_B;
        s->init_num = s->s2->challenge_length + 1;
        s->init_off = 0;
    }
    return (ssl2_do_write(s));
}

static int server_finish(SSL *s)
{
    unsigned char *p;

    if (s->state == SSL2_ST_SEND_SERVER_FINISHED_A) {
        p = (unsigned char *)s->init_buf->data;
        *(p++) = SSL2_MT_SERVER_FINISHED;

        if (s->session->session_id_length > sizeof s->session->session_id) {
            SSLerr(SSL_F_SERVER_FINISH, ERR_R_INTERNAL_ERROR);
            return -1;
        }
        memcpy(p, s->session->session_id,
               (unsigned int)s->session->session_id_length);
        /* p+=s->session->session_id_length; */

        s->state = SSL2_ST_SEND_SERVER_FINISHED_B;
        s->init_num = s->session->session_id_length + 1;
        s->init_off = 0;
    }

    /* SSL2_ST_SEND_SERVER_FINISHED_B */
    return (ssl2_do_write(s));
}

/* send the request and check the response */
static int request_certificate(SSL *s)
{
    const unsigned char *cp;
    unsigned char *p, *p2, *buf2;
    unsigned char *ccd;
    int i, j, ctype, ret = -1;
    unsigned long len;
    X509 *x509 = NULL;
    STACK_OF(X509) *sk = NULL;

    ccd = s->s2->tmp.ccl;
    if (s->state == SSL2_ST_SEND_REQUEST_CERTIFICATE_A) {
        p = (unsigned char *)s->init_buf->data;
        *(p++) = SSL2_MT_REQUEST_CERTIFICATE;
        *(p++) = SSL2_AT_MD5_WITH_RSA_ENCRYPTION;
        if (RAND_pseudo_bytes(ccd, SSL2_MIN_CERT_CHALLENGE_LENGTH) <= 0)
            return -1;
        memcpy(p, ccd, SSL2_MIN_CERT_CHALLENGE_LENGTH);

        s->state = SSL2_ST_SEND_REQUEST_CERTIFICATE_B;
        s->init_num = SSL2_MIN_CERT_CHALLENGE_LENGTH + 2;
        s->init_off = 0;
    }

    if (s->state == SSL2_ST_SEND_REQUEST_CERTIFICATE_B) {
        i = ssl2_do_write(s);
        if (i <= 0) {
            ret = i;
            goto end;
        }

        s->init_num = 0;
        s->state = SSL2_ST_SEND_REQUEST_CERTIFICATE_C;
    }

    if (s->state == SSL2_ST_SEND_REQUEST_CERTIFICATE_C) {
        p = (unsigned char *)s->init_buf->data;
        /* try to read 6 octets ... */
        i = ssl2_read(s, (char *)&(p[s->init_num]), 6 - s->init_num);
        /*
         * ... but don't call ssl2_part_read now if we got at least 3
         * (probably NO-CERTIFICATE-ERROR)
         */
        if (i < 3 - s->init_num) {
            ret = ssl2_part_read(s, SSL_F_REQUEST_CERTIFICATE, i);
            goto end;
        }
        s->init_num += i;

        if ((s->init_num >= 3) && (p[0] == SSL2_MT_ERROR)) {
            n2s(p, i);
            if (i != SSL2_PE_NO_CERTIFICATE) {
                /*
                 * not the error message we expected -- let ssl2_part_read
                 * handle it
                 */
                s->init_num -= 3;
                ret = ssl2_part_read(s, SSL_F_REQUEST_CERTIFICATE, 3);
                goto end;
            }

            if (s->msg_callback) {
                /* ERROR */
                s->msg_callback(0, s->version, 0, p, 3, s,
                                s->msg_callback_arg);
            }

            /*
             * this is the one place where we can recover from an SSL 2.0
             * error
             */

            if (s->verify_mode & SSL_VERIFY_FAIL_IF_NO_PEER_CERT) {
                ssl2_return_error(s, SSL2_PE_BAD_CERTIFICATE);
                SSLerr(SSL_F_REQUEST_CERTIFICATE,
                       SSL_R_PEER_DID_NOT_RETURN_A_CERTIFICATE);
                goto end;
            }
            ret = 1;
            goto end;
        }
        if ((*(p++) != SSL2_MT_CLIENT_CERTIFICATE) || (s->init_num < 6)) {
            ssl2_return_error(s, SSL2_PE_UNDEFINED_ERROR);
            SSLerr(SSL_F_REQUEST_CERTIFICATE, SSL_R_SHORT_READ);
            goto end;
        }
        if (s->init_num != 6) {
            SSLerr(SSL_F_REQUEST_CERTIFICATE, ERR_R_INTERNAL_ERROR);
            goto end;
        }

        /* ok we have a response */
        /* certificate type, there is only one right now. */
        ctype = *(p++);
        if (ctype != SSL2_AT_MD5_WITH_RSA_ENCRYPTION) {
            ssl2_return_error(s, SSL2_PE_UNSUPPORTED_CERTIFICATE_TYPE);
            SSLerr(SSL_F_REQUEST_CERTIFICATE, SSL_R_BAD_RESPONSE_ARGUMENT);
            goto end;
        }
        n2s(p, i);
        s->s2->tmp.clen = i;
        n2s(p, i);
        s->s2->tmp.rlen = i;
        s->state = SSL2_ST_SEND_REQUEST_CERTIFICATE_D;
    }

    /* SSL2_ST_SEND_REQUEST_CERTIFICATE_D */
    p = (unsigned char *)s->init_buf->data;
    len = 6 + (unsigned long)s->s2->tmp.clen + (unsigned long)s->s2->tmp.rlen;
    if (len > SSL2_MAX_RECORD_LENGTH_3_BYTE_HEADER) {
        SSLerr(SSL_F_REQUEST_CERTIFICATE, SSL_R_MESSAGE_TOO_LONG);
        goto end;
    }
    j = (int)len - s->init_num;
    i = ssl2_read(s, (char *)&(p[s->init_num]), j);
    if (i < j) {
        ret = ssl2_part_read(s, SSL_F_REQUEST_CERTIFICATE, i);
        goto end;
    }
    if (s->msg_callback) {
        /* CLIENT-CERTIFICATE */
        s->msg_callback(0, s->version, 0, p, len, s, s->msg_callback_arg);
    }
    p += 6;

    cp = p;
    x509 = (X509 *)d2i_X509(NULL, &cp, (long)s->s2->tmp.clen);
    if (x509 == NULL) {
        SSLerr(SSL_F_REQUEST_CERTIFICATE, ERR_R_X509_LIB);
        goto msg_end;
    }

    if (((sk = sk_X509_new_null()) == NULL) || (!sk_X509_push(sk, x509))) {
        SSLerr(SSL_F_REQUEST_CERTIFICATE, ERR_R_MALLOC_FAILURE);
        goto msg_end;
    }

    i = ssl_verify_cert_chain(s, sk);

    if (i > 0) {                /* we like the packet, now check the chksum */
        EVP_MD_CTX ctx;
        EVP_PKEY *pkey = NULL;

        EVP_MD_CTX_init(&ctx);
        if (!EVP_VerifyInit_ex(&ctx, s->ctx->rsa_md5, NULL)
            || !EVP_VerifyUpdate(&ctx, s->s2->key_material,
                                 s->s2->key_material_length)
            || !EVP_VerifyUpdate(&ctx, ccd, SSL2_MIN_CERT_CHALLENGE_LENGTH))
            goto msg_end;

        i = i2d_X509(s->cert->pkeys[SSL_PKEY_RSA_ENC].x509, NULL);
        buf2 = OPENSSL_malloc((unsigned int)i);
        if (buf2 == NULL) {
            SSLerr(SSL_F_REQUEST_CERTIFICATE, ERR_R_MALLOC_FAILURE);
            goto msg_end;
        }
        p2 = buf2;
        i = i2d_X509(s->cert->pkeys[SSL_PKEY_RSA_ENC].x509, &p2);
        if (!EVP_VerifyUpdate(&ctx, buf2, (unsigned int)i)) {
            OPENSSL_free(buf2);
            goto msg_end;
        }
        OPENSSL_free(buf2);

        pkey = X509_get_pubkey(x509);
        if (pkey == NULL)
            goto end;
        i = EVP_VerifyFinal(&ctx, cp, s->s2->tmp.rlen, pkey);
        EVP_PKEY_free(pkey);
        EVP_MD_CTX_cleanup(&ctx);

        if (i > 0) {
            if (s->session->peer != NULL)
                X509_free(s->session->peer);
            s->session->peer = x509;
            CRYPTO_add(&x509->references, 1, CRYPTO_LOCK_X509);
            s->session->verify_result = s->verify_result;
            ret = 1;
            goto end;
        } else {
            SSLerr(SSL_F_REQUEST_CERTIFICATE, SSL_R_BAD_CHECKSUM);
            goto msg_end;
        }
    } else {
 msg_end:
        ssl2_return_error(s, SSL2_PE_BAD_CERTIFICATE);
    }
 end:
    sk_X509_free(sk);
    X509_free(x509);
    return (ret);
}

static int ssl_rsa_private_decrypt(CERT *c, int len, unsigned char *from,
                                   unsigned char *to, int padding)
{
    RSA *rsa;
    int i;

    if ((c == NULL) || (c->pkeys[SSL_PKEY_RSA_ENC].privatekey == NULL)) {
        SSLerr(SSL_F_SSL_RSA_PRIVATE_DECRYPT, SSL_R_NO_PRIVATEKEY);
        return (-1);
    }
    if (c->pkeys[SSL_PKEY_RSA_ENC].privatekey->type != EVP_PKEY_RSA) {
        SSLerr(SSL_F_SSL_RSA_PRIVATE_DECRYPT, SSL_R_PUBLIC_KEY_IS_NOT_RSA);
        return (-1);
    }
    rsa = c->pkeys[SSL_PKEY_RSA_ENC].privatekey->pkey.rsa;

    /* we have the public key */
    i = RSA_private_decrypt(len, from, to, rsa, padding);
    if (i < 0)
        SSLerr(SSL_F_SSL_RSA_PRIVATE_DECRYPT, ERR_R_RSA_LIB);
    return (i);
}
#else                           /* !OPENSSL_NO_SSL2 */

# if PEDANTIC
static void *dummy = &dummy;
# endif

#endif