Avoid warnings on VC++ 2005.

[thirdparty/openssl.git] / ssl / ssl_sess.c

/* ssl/ssl_sess.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.]
 */

#include <stdio.h>
#include <openssl/lhash.h>
#include <openssl/rand.h>
#include "ssl_locl.h"

static void SSL_SESSION_list_remove(SSL_CTX *ctx, SSL_SESSION *s);
static void SSL_SESSION_list_add(SSL_CTX *ctx,SSL_SESSION *s);
static int remove_session_lock(SSL_CTX *ctx, SSL_SESSION *c, int lck);

SSL_SESSION *SSL_get_session(const SSL *ssl)
/* aka SSL_get0_session; gets 0 objects, just returns a copy of the pointer */
        {
        return(ssl->session);
        }

SSL_SESSION *SSL_get1_session(SSL *ssl)
/* variant of SSL_get_session: caller really gets something */
        {
        SSL_SESSION *sess;
        /* Need to lock this all up rather than just use CRYPTO_add so that
         * somebody doesn't free ssl->session between when we check it's
         * non-null and when we up the reference count. */
        CRYPTO_w_lock(CRYPTO_LOCK_SSL_SESSION);
        sess = ssl->session;
        if(sess)
                sess->references++;
        CRYPTO_w_unlock(CRYPTO_LOCK_SSL_SESSION);
        return(sess);
        }

int SSL_SESSION_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func,
             CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func)
        {
        return CRYPTO_get_ex_new_index(CRYPTO_EX_INDEX_SSL_SESSION, argl, argp,
                        new_func, dup_func, free_func);
        }

int SSL_SESSION_set_ex_data(SSL_SESSION *s, int idx, void *arg)
        {
        return(CRYPTO_set_ex_data(&s->ex_data,idx,arg));
        }

void *SSL_SESSION_get_ex_data(const SSL_SESSION *s, int idx)
        {
        return(CRYPTO_get_ex_data(&s->ex_data,idx));
        }

SSL_SESSION *SSL_SESSION_new(void)
        {
        SSL_SESSION *ss;

        ss=(SSL_SESSION *)OPENSSL_malloc(sizeof(SSL_SESSION));
        if (ss == NULL)
                {
                SSLerr(SSL_F_SSL_SESSION_NEW,ERR_R_MALLOC_FAILURE);
                return(0);
                }
        memset(ss,0,sizeof(SSL_SESSION));

        ss->verify_result = 1; /* avoid 0 (= X509_V_OK) just in case */
        ss->references=1;
        ss->timeout=60*5+4; /* 5 minute timeout by default */
        ss->time=(unsigned long)time(NULL);
        ss->prev=NULL;
        ss->next=NULL;
        ss->compress_meth=0;
        CRYPTO_new_ex_data(CRYPTO_EX_INDEX_SSL_SESSION, ss, &ss->ex_data);
        return(ss);
        }

const unsigned char *SSL_SESSION_get_id(const SSL_SESSION *s, unsigned int *len)
        {
        if(len)
                *len = s->session_id_length;
        return s->session_id;
        }

/* Even with SSLv2, we have 16 bytes (128 bits) of session ID space. SSLv3/TLSv1
 * has 32 bytes (256 bits). As such, filling the ID with random gunk repeatedly
 * until we have no conflict is going to complete in one iteration pretty much
 * "most" of the time (btw: understatement). So, if it takes us 10 iterations
 * and we still can't avoid a conflict - well that's a reasonable point to call
 * it quits. Either the RAND code is broken or someone is trying to open roughly
 * very close to 2^128 (or 2^256) SSL sessions to our server. How you might
 * store that many sessions is perhaps a more interesting question ... */

#define MAX_SESS_ID_ATTEMPTS 10
static int def_generate_session_id(const SSL *ssl, unsigned char *id,
                                unsigned int *id_len)
{
        unsigned int retry = 0;
        do
                if (RAND_pseudo_bytes(id, *id_len) <= 0)
                        return 0;
        while(SSL_has_matching_session_id(ssl, id, *id_len) &&
                (++retry < MAX_SESS_ID_ATTEMPTS));
        if(retry < MAX_SESS_ID_ATTEMPTS)
                return 1;
        /* else - woops a session_id match */
        /* XXX We should also check the external cache --
         * but the probability of a collision is negligible, and
         * we could not prevent the concurrent creation of sessions
         * with identical IDs since we currently don't have means
         * to atomically check whether a session ID already exists
         * and make a reservation for it if it does not
         * (this problem applies to the internal cache as well).
         */
        return 0;
}

int ssl_get_new_session(SSL *s, int session)
        {
        /* This gets used by clients and servers. */

        unsigned int tmp;
        SSL_SESSION *ss=NULL;
        GEN_SESSION_CB cb = def_generate_session_id;

        if ((ss=SSL_SESSION_new()) == NULL) return(0);

        /* If the context has a default timeout, use it */
        if (s->ctx->session_timeout == 0)
                ss->timeout=SSL_get_default_timeout(s);
        else
                ss->timeout=s->ctx->session_timeout;

        if (s->session != NULL)
                {
                SSL_SESSION_free(s->session);
                s->session=NULL;
                }

        if (session)
                {
                if (s->version == SSL2_VERSION)
                        {
                        ss->ssl_version=SSL2_VERSION;
                        ss->session_id_length=SSL2_SSL_SESSION_ID_LENGTH;
                        }
                else if (s->version == SSL3_VERSION)
                        {
                        ss->ssl_version=SSL3_VERSION;
                        ss->session_id_length=SSL3_SSL_SESSION_ID_LENGTH;
                        }
                else if (s->version == TLS1_VERSION)
                        {
                        ss->ssl_version=TLS1_VERSION;
                        ss->session_id_length=SSL3_SSL_SESSION_ID_LENGTH;
                        }
                else if (s->version == DTLS1_VERSION)
                        {
                        ss->ssl_version=DTLS1_VERSION;
                        ss->session_id_length=SSL3_SSL_SESSION_ID_LENGTH;
                        }
                else
                        {
                        SSLerr(SSL_F_SSL_GET_NEW_SESSION,SSL_R_UNSUPPORTED_SSL_VERSION);
                        SSL_SESSION_free(ss);
                        return(0);
                        }
                /* Choose which callback will set the session ID */
                CRYPTO_r_lock(CRYPTO_LOCK_SSL_CTX);
                if(s->generate_session_id)
                        cb = s->generate_session_id;
                else if(s->ctx->generate_session_id)
                        cb = s->ctx->generate_session_id;
                CRYPTO_r_unlock(CRYPTO_LOCK_SSL_CTX);
                /* Choose a session ID */
                tmp = ss->session_id_length;
                if(!cb(s, ss->session_id, &tmp))
                        {
                        /* The callback failed */
                        SSLerr(SSL_F_SSL_GET_NEW_SESSION,
                                SSL_R_SSL_SESSION_ID_CALLBACK_FAILED);
                        SSL_SESSION_free(ss);
                        return(0);
                        }
                /* Don't allow the callback to set the session length to zero.
                 * nor set it higher than it was. */
                if(!tmp || (tmp > ss->session_id_length))
                        {
                        /* The callback set an illegal length */
                        SSLerr(SSL_F_SSL_GET_NEW_SESSION,
                                SSL_R_SSL_SESSION_ID_HAS_BAD_LENGTH);
                        SSL_SESSION_free(ss);
                        return(0);
                        }
                /* If the session length was shrunk and we're SSLv2, pad it */
                if((tmp < ss->session_id_length) && (s->version == SSL2_VERSION))
                        memset(ss->session_id + tmp, 0, ss->session_id_length - tmp);
                else
                        ss->session_id_length = tmp;
                /* Finally, check for a conflict */
                if(SSL_has_matching_session_id(s, ss->session_id,
                                                ss->session_id_length))
                        {
                        SSLerr(SSL_F_SSL_GET_NEW_SESSION,
                                SSL_R_SSL_SESSION_ID_CONFLICT);
                        SSL_SESSION_free(ss);
                        return(0);
                        }
                }
        else
                {
                ss->session_id_length=0;
                }

        if (s->sid_ctx_length > sizeof ss->sid_ctx)
                {
                SSLerr(SSL_F_SSL_GET_NEW_SESSION, ERR_R_INTERNAL_ERROR);
                SSL_SESSION_free(ss);
                return 0;
                }
        memcpy(ss->sid_ctx,s->sid_ctx,s->sid_ctx_length);
        ss->sid_ctx_length=s->sid_ctx_length;
        s->session=ss;
        ss->ssl_version=s->version;
        ss->verify_result = X509_V_OK;

        return(1);
        }

int ssl_get_prev_session(SSL *s, unsigned char *session_id, int len)
        {
        /* This is used only by servers. */

        SSL_SESSION *ret=NULL,data;
        int fatal = 0;

        data.ssl_version=s->version;
        data.session_id_length=len;
        if (len > SSL_MAX_SSL_SESSION_ID_LENGTH)
                goto err;
        memcpy(data.session_id,session_id,len);

        if (!(s->ctx->session_cache_mode & SSL_SESS_CACHE_NO_INTERNAL_LOOKUP))
                {
                CRYPTO_r_lock(CRYPTO_LOCK_SSL_CTX);
                ret=(SSL_SESSION *)lh_retrieve(s->ctx->sessions,&data);
                if (ret != NULL)
                    /* don't allow other threads to steal it: */
                    CRYPTO_add(&ret->references,1,CRYPTO_LOCK_SSL_SESSION);
                CRYPTO_r_unlock(CRYPTO_LOCK_SSL_CTX);
                }

        if (ret == NULL)
                {
                int copy=1;
        
                s->ctx->stats.sess_miss++;
                ret=NULL;
                if (s->ctx->get_session_cb != NULL
                    && (ret=s->ctx->get_session_cb(s,session_id,len,&copy))
                       != NULL)
                        {
                        s->ctx->stats.sess_cb_hit++;

                        /* Increment reference count now if the session callback
                         * asks us to do so (note that if the session structures
                         * returned by the callback are shared between threads,
                         * it must handle the reference count itself [i.e. copy == 0],
                         * or things won't be thread-safe). */
                        if (copy)
                                CRYPTO_add(&ret->references,1,CRYPTO_LOCK_SSL_SESSION);

                        /* Add the externally cached session to the internal
                         * cache as well if and only if we are supposed to. */
                        if(!(s->ctx->session_cache_mode & SSL_SESS_CACHE_NO_INTERNAL_STORE))
                                /* The following should not return 1, otherwise,
                                 * things are very strange */
                                SSL_CTX_add_session(s->ctx,ret);
                        }
                if (ret == NULL)
                        goto err;
                }

        /* Now ret is non-NULL, and we own one of its reference counts. */

        if((s->verify_mode&SSL_VERIFY_PEER)
           && (!s->sid_ctx_length || ret->sid_ctx_length != s->sid_ctx_length
               || memcmp(ret->sid_ctx,s->sid_ctx,ret->sid_ctx_length)))
            {
                /* We've found the session named by the client, but we don't
                 * want to use it in this context. */
                
                if (s->sid_ctx_length == 0)
                        {
                        /* application should have used SSL[_CTX]_set_session_id_context
                         * -- we could tolerate this and just pretend we never heard
                         * of this session, but then applications could effectively
                         * disable the session cache by accident without anyone noticing */

                        SSLerr(SSL_F_SSL_GET_PREV_SESSION,SSL_R_SESSION_ID_CONTEXT_UNINITIALIZED);
                        fatal = 1;
                        goto err;
                        }
                else
                        {
#if 0 /* The client cannot always know when a session is not appropriate,
           * so we shouldn't generate an error message. */

                        SSLerr(SSL_F_SSL_GET_PREV_SESSION,SSL_R_ATTEMPT_TO_REUSE_SESSION_IN_DIFFERENT_CONTEXT);
#endif
                        goto err; /* treat like cache miss */
                        }
                }

        if (ret->cipher == NULL)
                {
                unsigned char buf[5],*p;
                unsigned long l;

                p=buf;
                l=ret->cipher_id;
                l2n(l,p);
                if ((ret->ssl_version>>8) == SSL3_VERSION_MAJOR)
                        ret->cipher=ssl_get_cipher_by_char(s,&(buf[2]));
                else 
                        ret->cipher=ssl_get_cipher_by_char(s,&(buf[1]));
                if (ret->cipher == NULL)
                        goto err;
                }


#if 0 /* This is way too late. */

        /* If a thread got the session, then 'swaped', and another got
         * it and then due to a time-out decided to 'OPENSSL_free' it we could
         * be in trouble.  So I'll increment it now, then double decrement
         * later - am I speaking rubbish?. */
        CRYPTO_add(&ret->references,1,CRYPTO_LOCK_SSL_SESSION);
#endif

        if ((long)(ret->time+ret->timeout) < (long)time(NULL)) /* timeout */
                {
                s->ctx->stats.sess_timeout++;
                /* remove it from the cache */
                SSL_CTX_remove_session(s->ctx,ret);
                goto err;
                }

        s->ctx->stats.sess_hit++;

        /* ret->time=time(NULL); */ /* rezero timeout? */
        /* again, just leave the session 
         * if it is the same session, we have just incremented and
         * then decremented the reference count :-) */
        if (s->session != NULL)
                SSL_SESSION_free(s->session);
        s->session=ret;
        s->verify_result = s->session->verify_result;
        return(1);

 err:
        if (ret != NULL)
                SSL_SESSION_free(ret);
        if (fatal)
                return -1;
        else
                return 0;
        }

int SSL_CTX_add_session(SSL_CTX *ctx, SSL_SESSION *c)
        {
        int ret=0;
        SSL_SESSION *s;

        /* add just 1 reference count for the SSL_CTX's session cache
         * even though it has two ways of access: each session is in a
         * doubly linked list and an lhash */
        CRYPTO_add(&c->references,1,CRYPTO_LOCK_SSL_SESSION);
        /* if session c is in already in cache, we take back the increment later */

        CRYPTO_w_lock(CRYPTO_LOCK_SSL_CTX);
        s=(SSL_SESSION *)lh_insert(ctx->sessions,c);
        
        /* s != NULL iff we already had a session with the given PID.
         * In this case, s == c should hold (then we did not really modify
         * ctx->sessions), or we're in trouble. */
        if (s != NULL && s != c)
                {
                /* We *are* in trouble ... */
                SSL_SESSION_list_remove(ctx,s);
                SSL_SESSION_free(s);
                /* ... so pretend the other session did not exist in cache
                 * (we cannot handle two SSL_SESSION structures with identical
                 * session ID in the same cache, which could happen e.g. when
                 * two threads concurrently obtain the same session from an external
                 * cache) */
                s = NULL;
                }

        /* Put at the head of the queue unless it is already in the cache */
        if (s == NULL)
                SSL_SESSION_list_add(ctx,c);

        if (s != NULL)
                {
                /* existing cache entry -- decrement previously incremented reference
                 * count because it already takes into account the cache */

                SSL_SESSION_free(s); /* s == c */
                ret=0;
                }
        else
                {
                /* new cache entry -- remove old ones if cache has become too large */
                
                ret=1;

                if (SSL_CTX_sess_get_cache_size(ctx) > 0)
                        {
                        while (SSL_CTX_sess_number(ctx) >
                                SSL_CTX_sess_get_cache_size(ctx))
                                {
                                if (!remove_session_lock(ctx,
                                        ctx->session_cache_tail, 0))
                                        break;
                                else
                                        ctx->stats.sess_cache_full++;
                                }
                        }
                }
        CRYPTO_w_unlock(CRYPTO_LOCK_SSL_CTX);
        return(ret);
        }

int SSL_CTX_remove_session(SSL_CTX *ctx, SSL_SESSION *c)
{
        return remove_session_lock(ctx, c, 1);
}

static int remove_session_lock(SSL_CTX *ctx, SSL_SESSION *c, int lck)
        {
        SSL_SESSION *r;
        int ret=0;

        if ((c != NULL) && (c->session_id_length != 0))
                {
                if(lck) CRYPTO_w_lock(CRYPTO_LOCK_SSL_CTX);
                if ((r = (SSL_SESSION *)lh_retrieve(ctx->sessions,c)) == c)
                        {
                        ret=1;
                        r=(SSL_SESSION *)lh_delete(ctx->sessions,c);
                        SSL_SESSION_list_remove(ctx,c);
                        }

                if(lck) CRYPTO_w_unlock(CRYPTO_LOCK_SSL_CTX);

                if (ret)
                        {
                        r->not_resumable=1;
                        if (ctx->remove_session_cb != NULL)
                                ctx->remove_session_cb(ctx,r);
                        SSL_SESSION_free(r);
                        }
                }
        else
                ret=0;
        return(ret);
        }

void SSL_SESSION_free(SSL_SESSION *ss)
        {
        int i;

        if(ss == NULL)
            return;

        i=CRYPTO_add(&ss->references,-1,CRYPTO_LOCK_SSL_SESSION);
#ifdef REF_PRINT
        REF_PRINT("SSL_SESSION",ss);
#endif
        if (i > 0) return;
#ifdef REF_CHECK
        if (i < 0)
                {
                fprintf(stderr,"SSL_SESSION_free, bad reference count\n");
                abort(); /* ok */
                }
#endif

        CRYPTO_free_ex_data(CRYPTO_EX_INDEX_SSL_SESSION, ss, &ss->ex_data);

        OPENSSL_cleanse(ss->key_arg,sizeof ss->key_arg);
        OPENSSL_cleanse(ss->master_key,sizeof ss->master_key);
        OPENSSL_cleanse(ss->session_id,sizeof ss->session_id);
        if (ss->sess_cert != NULL) ssl_sess_cert_free(ss->sess_cert);
        if (ss->peer != NULL) X509_free(ss->peer);
        if (ss->ciphers != NULL) sk_SSL_CIPHER_free(ss->ciphers);
        OPENSSL_cleanse(ss,sizeof(*ss));
        OPENSSL_free(ss);
        }

int SSL_set_session(SSL *s, SSL_SESSION *session)
        {
        int ret=0;
        const SSL_METHOD *meth;

        if (session != NULL)
                {
                meth=s->ctx->method->get_ssl_method(session->ssl_version);
                if (meth == NULL)
                        meth=s->method->get_ssl_method(session->ssl_version);
                if (meth == NULL)
                        {
                        SSLerr(SSL_F_SSL_SET_SESSION,SSL_R_UNABLE_TO_FIND_SSL_METHOD);
                        return(0);
                        }

                if (meth != s->method)
                        {
                        if (!SSL_set_ssl_method(s,meth))
                                return(0);
                        if (s->ctx->session_timeout == 0)
                                session->timeout=SSL_get_default_timeout(s);
                        else
                                session->timeout=s->ctx->session_timeout;
                        }

#ifndef OPENSSL_NO_KRB5
                if (s->kssl_ctx && !s->kssl_ctx->client_princ &&
                    session->krb5_client_princ_len > 0)
                {
                    s->kssl_ctx->client_princ = (char *)malloc(session->krb5_client_princ_len + 1);
                    memcpy(s->kssl_ctx->client_princ,session->krb5_client_princ,
                            session->krb5_client_princ_len);
                    s->kssl_ctx->client_princ[session->krb5_client_princ_len] = '\0';
                }
#endif /* OPENSSL_NO_KRB5 */

                /* CRYPTO_w_lock(CRYPTO_LOCK_SSL);*/
                CRYPTO_add(&session->references,1,CRYPTO_LOCK_SSL_SESSION);
                if (s->session != NULL)
                        SSL_SESSION_free(s->session);
                s->session=session;
                s->verify_result = s->session->verify_result;
                /* CRYPTO_w_unlock(CRYPTO_LOCK_SSL);*/
                ret=1;
                }
        else
                {
                if (s->session != NULL)
                        {
                        SSL_SESSION_free(s->session);
                        s->session=NULL;
                        }

                meth=s->ctx->method;
                if (meth != s->method)
                        {
                        if (!SSL_set_ssl_method(s,meth))
                                return(0);
                        }
                ret=1;
                }
        return(ret);
        }

long SSL_SESSION_set_timeout(SSL_SESSION *s, long t)
        {
        if (s == NULL) return(0);
        s->timeout=t;
        return(1);
        }

long SSL_SESSION_get_timeout(const SSL_SESSION *s)
        {
        if (s == NULL) return(0);
        return(s->timeout);
        }

long SSL_SESSION_get_time(const SSL_SESSION *s)
        {
        if (s == NULL) return(0);
        return(s->time);
        }

long SSL_SESSION_set_time(SSL_SESSION *s, long t)
        {
        if (s == NULL) return(0);
        s->time=t;
        return(t);
        }

long SSL_CTX_set_timeout(SSL_CTX *s, long t)
        {
        long l;
        if (s == NULL) return(0);
        l=s->session_timeout;
        s->session_timeout=t;
        return(l);
        }

long SSL_CTX_get_timeout(const SSL_CTX *s)
        {
        if (s == NULL) return(0);
        return(s->session_timeout);
        }

typedef struct timeout_param_st
        {
        SSL_CTX *ctx;
        long time;
        LHASH *cache;
        } TIMEOUT_PARAM;

static void timeout(SSL_SESSION *s, TIMEOUT_PARAM *p)
        {
        if ((p->time == 0) || (p->time > (s->time+s->timeout))) /* timeout */
                {
                /* The reason we don't call SSL_CTX_remove_session() is to
                 * save on locking overhead */
                lh_delete(p->cache,s);
                SSL_SESSION_list_remove(p->ctx,s);
                s->not_resumable=1;
                if (p->ctx->remove_session_cb != NULL)
                        p->ctx->remove_session_cb(p->ctx,s);
                SSL_SESSION_free(s);
                }
        }

static IMPLEMENT_LHASH_DOALL_ARG_FN(timeout, SSL_SESSION *, TIMEOUT_PARAM *)

void SSL_CTX_flush_sessions(SSL_CTX *s, long t)
        {
        unsigned long i;
        TIMEOUT_PARAM tp;

        tp.ctx=s;
        tp.cache=s->sessions;
        if (tp.cache == NULL) return;
        tp.time=t;
        CRYPTO_w_lock(CRYPTO_LOCK_SSL_CTX);
        i=tp.cache->down_load;
        tp.cache->down_load=0;
        lh_doall_arg(tp.cache, LHASH_DOALL_ARG_FN(timeout), &tp);
        tp.cache->down_load=i;
        CRYPTO_w_unlock(CRYPTO_LOCK_SSL_CTX);
        }

int ssl_clear_bad_session(SSL *s)
        {
        if (    (s->session != NULL) &&
                !(s->shutdown & SSL_SENT_SHUTDOWN) &&
                !(SSL_in_init(s) || SSL_in_before(s)))
                {
                SSL_CTX_remove_session(s->ctx,s->session);
                return(1);
                }
        else
                return(0);
        }

/* locked by SSL_CTX in the calling function */
static void SSL_SESSION_list_remove(SSL_CTX *ctx, SSL_SESSION *s)
        {
        if ((s->next == NULL) || (s->prev == NULL)) return;

        if (s->next == (SSL_SESSION *)&(ctx->session_cache_tail))
                { /* last element in list */
                if (s->prev == (SSL_SESSION *)&(ctx->session_cache_head))
                        { /* only one element in list */
                        ctx->session_cache_head=NULL;
                        ctx->session_cache_tail=NULL;
                        }
                else
                        {
                        ctx->session_cache_tail=s->prev;
                        s->prev->next=(SSL_SESSION *)&(ctx->session_cache_tail);
                        }
                }
        else
                {
                if (s->prev == (SSL_SESSION *)&(ctx->session_cache_head))
                        { /* first element in list */
                        ctx->session_cache_head=s->next;
                        s->next->prev=(SSL_SESSION *)&(ctx->session_cache_head);
                        }
                else
                        { /* middle of list */
                        s->next->prev=s->prev;
                        s->prev->next=s->next;
                        }
                }
        s->prev=s->next=NULL;
        }

static void SSL_SESSION_list_add(SSL_CTX *ctx, SSL_SESSION *s)
        {
        if ((s->next != NULL) && (s->prev != NULL))
                SSL_SESSION_list_remove(ctx,s);

        if (ctx->session_cache_head == NULL)
                {
                ctx->session_cache_head=s;
                ctx->session_cache_tail=s;
                s->prev=(SSL_SESSION *)&(ctx->session_cache_head);
                s->next=(SSL_SESSION *)&(ctx->session_cache_tail);
                }
        else
                {
                s->next=ctx->session_cache_head;
                s->next->prev=s;
                s->prev=(SSL_SESSION *)&(ctx->session_cache_head);
                ctx->session_cache_head=s;
                }
        }