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view src/mail/ngx_mail_ssl_module.c @ 6553:2014ed60f17f

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SSL: support for multiple curves (ticket #885). OpenSSL 1.0.2+ allows configuring a curve list instead of a single curve previously supported. This allows use of different curves depending on what client supports (as available via the elliptic_curves extension), and also allows use of different curves in an ECDHE key exchange and in the ECDSA certificate. The special value "auto" was introduced (now the default for ssl_ecdh_curve), which means "use an internal list of curves as available in the OpenSSL library used". For versions prior to OpenSSL 1.0.2 it maps to "prime256v1" as previously used. The default in 1.0.2b+ prefers prime256v1 as well (and X25519 in OpenSSL 1.1.0+). As client vs. server preference of curves is controlled by the same option as used for ciphers (SSL_OP_CIPHER_SERVER_PREFERENCE), the ssl_prefer_server_ciphers directive now controls both.
author Maxim Dounin <mdounin@mdounin.ru>
date Thu, 19 May 2016 14:46:32 +0300
parents 51e1f047d15d
children 04d8d1f85649
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_mail.h>


#define NGX_DEFAULT_CIPHERS     "HIGH:!aNULL:!MD5"
#define NGX_DEFAULT_ECDH_CURVE  "auto"


static void *ngx_mail_ssl_create_conf(ngx_conf_t *cf);
static char *ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child);

static char *ngx_mail_ssl_enable(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);
static char *ngx_mail_ssl_starttls(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);
static char *ngx_mail_ssl_password_file(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);
static char *ngx_mail_ssl_session_cache(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);


static ngx_conf_enum_t  ngx_mail_starttls_state[] = {
    { ngx_string("off"), NGX_MAIL_STARTTLS_OFF },
    { ngx_string("on"), NGX_MAIL_STARTTLS_ON },
    { ngx_string("only"), NGX_MAIL_STARTTLS_ONLY },
    { ngx_null_string, 0 }
};



static ngx_conf_bitmask_t  ngx_mail_ssl_protocols[] = {
    { ngx_string("SSLv2"), NGX_SSL_SSLv2 },
    { ngx_string("SSLv3"), NGX_SSL_SSLv3 },
    { ngx_string("TLSv1"), NGX_SSL_TLSv1 },
    { ngx_string("TLSv1.1"), NGX_SSL_TLSv1_1 },
    { ngx_string("TLSv1.2"), NGX_SSL_TLSv1_2 },
    { ngx_null_string, 0 }
};


static ngx_conf_enum_t  ngx_mail_ssl_verify[] = {
    { ngx_string("off"), 0 },
    { ngx_string("on"), 1 },
    { ngx_string("optional"), 2 },
    { ngx_string("optional_no_ca"), 3 },
    { ngx_null_string, 0 }
};


static ngx_command_t  ngx_mail_ssl_commands[] = {

    { ngx_string("ssl"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
      ngx_mail_ssl_enable,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, enable),
      NULL },

    { ngx_string("starttls"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_mail_ssl_starttls,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, starttls),
      ngx_mail_starttls_state },

    { ngx_string("ssl_certificate"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_array_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, certificates),
      NULL },

    { ngx_string("ssl_certificate_key"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_array_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, certificate_keys),
      NULL },

    { ngx_string("ssl_password_file"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_mail_ssl_password_file,
      NGX_MAIL_SRV_CONF_OFFSET,
      0,
      NULL },

    { ngx_string("ssl_dhparam"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, dhparam),
      NULL },

    { ngx_string("ssl_ecdh_curve"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, ecdh_curve),
      NULL },

    { ngx_string("ssl_protocols"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_1MORE,
      ngx_conf_set_bitmask_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, protocols),
      &ngx_mail_ssl_protocols },

    { ngx_string("ssl_ciphers"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, ciphers),
      NULL },

    { ngx_string("ssl_prefer_server_ciphers"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, prefer_server_ciphers),
      NULL },

    { ngx_string("ssl_session_cache"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE12,
      ngx_mail_ssl_session_cache,
      NGX_MAIL_SRV_CONF_OFFSET,
      0,
      NULL },

    { ngx_string("ssl_session_tickets"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, session_tickets),
      NULL },

    { ngx_string("ssl_session_ticket_key"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_array_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, session_ticket_keys),
      NULL },

    { ngx_string("ssl_session_timeout"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_sec_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, session_timeout),
      NULL },

    { ngx_string("ssl_verify_client"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_enum_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, verify),
      &ngx_mail_ssl_verify },

    { ngx_string("ssl_verify_depth"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_num_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, verify_depth),
      NULL },

    { ngx_string("ssl_client_certificate"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, client_certificate),
      NULL },

    { ngx_string("ssl_trusted_certificate"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, trusted_certificate),
      NULL },

    { ngx_string("ssl_crl"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_str_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_ssl_conf_t, crl),
      NULL },

      ngx_null_command
};


static ngx_mail_module_t  ngx_mail_ssl_module_ctx = {
    NULL,                                  /* protocol */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    ngx_mail_ssl_create_conf,              /* create server configuration */
    ngx_mail_ssl_merge_conf                /* merge server configuration */
};


ngx_module_t  ngx_mail_ssl_module = {
    NGX_MODULE_V1,
    &ngx_mail_ssl_module_ctx,              /* module context */
    ngx_mail_ssl_commands,                 /* module directives */
    NGX_MAIL_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_str_t ngx_mail_ssl_sess_id_ctx = ngx_string("MAIL");


static void *
ngx_mail_ssl_create_conf(ngx_conf_t *cf)
{
    ngx_mail_ssl_conf_t  *scf;

    scf = ngx_pcalloc(cf->pool, sizeof(ngx_mail_ssl_conf_t));
    if (scf == NULL) {
        return NULL;
    }

    /*
     * set by ngx_pcalloc():
     *
     *     scf->protocols = 0;
     *     scf->dhparam = { 0, NULL };
     *     scf->ecdh_curve = { 0, NULL };
     *     scf->client_certificate = { 0, NULL };
     *     scf->trusted_certificate = { 0, NULL };
     *     scf->crl = { 0, NULL };
     *     scf->ciphers = { 0, NULL };
     *     scf->shm_zone = NULL;
     */

    scf->enable = NGX_CONF_UNSET;
    scf->starttls = NGX_CONF_UNSET_UINT;
    scf->certificates = NGX_CONF_UNSET_PTR;
    scf->certificate_keys = NGX_CONF_UNSET_PTR;
    scf->passwords = NGX_CONF_UNSET_PTR;
    scf->prefer_server_ciphers = NGX_CONF_UNSET;
    scf->verify = NGX_CONF_UNSET_UINT;
    scf->verify_depth = NGX_CONF_UNSET_UINT;
    scf->builtin_session_cache = NGX_CONF_UNSET;
    scf->session_timeout = NGX_CONF_UNSET;
    scf->session_tickets = NGX_CONF_UNSET;
    scf->session_ticket_keys = NGX_CONF_UNSET_PTR;

    return scf;
}


static char *
ngx_mail_ssl_merge_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_mail_ssl_conf_t *prev = parent;
    ngx_mail_ssl_conf_t *conf = child;

    char                *mode;
    ngx_pool_cleanup_t  *cln;

    ngx_conf_merge_value(conf->enable, prev->enable, 0);
    ngx_conf_merge_uint_value(conf->starttls, prev->starttls,
                         NGX_MAIL_STARTTLS_OFF);

    ngx_conf_merge_value(conf->session_timeout,
                         prev->session_timeout, 300);

    ngx_conf_merge_value(conf->prefer_server_ciphers,
                         prev->prefer_server_ciphers, 0);

    ngx_conf_merge_bitmask_value(conf->protocols, prev->protocols,
                         (NGX_CONF_BITMASK_SET|NGX_SSL_TLSv1
                          |NGX_SSL_TLSv1_1|NGX_SSL_TLSv1_2));

    ngx_conf_merge_uint_value(conf->verify, prev->verify, 0);
    ngx_conf_merge_uint_value(conf->verify_depth, prev->verify_depth, 1);

    ngx_conf_merge_ptr_value(conf->certificates, prev->certificates, NULL);
    ngx_conf_merge_ptr_value(conf->certificate_keys, prev->certificate_keys,
                         NULL);

    ngx_conf_merge_ptr_value(conf->passwords, prev->passwords, NULL);

    ngx_conf_merge_str_value(conf->dhparam, prev->dhparam, "");

    ngx_conf_merge_str_value(conf->ecdh_curve, prev->ecdh_curve,
                         NGX_DEFAULT_ECDH_CURVE);

    ngx_conf_merge_str_value(conf->client_certificate,
                         prev->client_certificate, "");
    ngx_conf_merge_str_value(conf->trusted_certificate,
                         prev->trusted_certificate, "");
    ngx_conf_merge_str_value(conf->crl, prev->crl, "");

    ngx_conf_merge_str_value(conf->ciphers, prev->ciphers, NGX_DEFAULT_CIPHERS);


    conf->ssl.log = cf->log;

    if (conf->enable) {
        mode = "ssl";

    } else if (conf->starttls != NGX_MAIL_STARTTLS_OFF) {
        mode = "starttls";

    } else {
        mode = "";
    }

    if (conf->file == NULL) {
        conf->file = prev->file;
        conf->line = prev->line;
    }

    if (*mode) {

        if (conf->certificates == NULL) {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "no \"ssl_certificate\" is defined for "
                          "the \"%s\" directive in %s:%ui",
                          mode, conf->file, conf->line);
            return NGX_CONF_ERROR;
        }

        if (conf->certificate_keys == NULL) {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "no \"ssl_certificate_key\" is defined for "
                          "the \"%s\" directive in %s:%ui",
                          mode, conf->file, conf->line);
            return NGX_CONF_ERROR;
        }

        if (conf->certificate_keys->nelts < conf->certificates->nelts) {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "no \"ssl_certificate_key\" is defined "
                          "for certificate \"%V\" and "
                          "the \"ssl\" directive in %s:%ui",
                          ((ngx_str_t *) conf->certificates->elts)
                          + conf->certificates->nelts - 1,
                          conf->file, conf->line);
            return NGX_CONF_ERROR;
        }

    } else {

        if (conf->certificates == NULL) {
            return NGX_CONF_OK;
        }

        if (conf->certificate_keys == NULL
            || conf->certificate_keys->nelts < conf->certificates->nelts)
        {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "no \"ssl_certificate_key\" is defined "
                          "for certificate \"%V\"",
                          ((ngx_str_t *) conf->certificates->elts)
                          + conf->certificates->nelts - 1);
            return NGX_CONF_ERROR;
        }
    }

    if (ngx_ssl_create(&conf->ssl, conf->protocols, NULL) != NGX_OK) {
        return NGX_CONF_ERROR;
    }

    cln = ngx_pool_cleanup_add(cf->pool, 0);
    if (cln == NULL) {
        return NGX_CONF_ERROR;
    }

    cln->handler = ngx_ssl_cleanup_ctx;
    cln->data = &conf->ssl;

    if (ngx_ssl_certificates(cf, &conf->ssl, conf->certificates,
                             conf->certificate_keys, conf->passwords)
        != NGX_OK)
    {
        return NGX_CONF_ERROR;
    }

    if (conf->verify) {

        if (conf->client_certificate.len == 0 && conf->verify != 3) {
            ngx_log_error(NGX_LOG_EMERG, cf->log, 0,
                          "no ssl_client_certificate for ssl_client_verify");
            return NGX_CONF_ERROR;
        }

        if (ngx_ssl_client_certificate(cf, &conf->ssl,
                                       &conf->client_certificate,
                                       conf->verify_depth)
            != NGX_OK)
        {
            return NGX_CONF_ERROR;
        }

        if (ngx_ssl_trusted_certificate(cf, &conf->ssl,
                                        &conf->trusted_certificate,
                                        conf->verify_depth)
            != NGX_OK)
        {
            return NGX_CONF_ERROR;
        }

        if (ngx_ssl_crl(cf, &conf->ssl, &conf->crl) != NGX_OK) {
            return NGX_CONF_ERROR;
        }
    }

    if (SSL_CTX_set_cipher_list(conf->ssl.ctx,
                                (const char *) conf->ciphers.data)
        == 0)
    {
        ngx_ssl_error(NGX_LOG_EMERG, cf->log, 0,
                      "SSL_CTX_set_cipher_list(\"%V\") failed",
                      &conf->ciphers);
        return NGX_CONF_ERROR;
    }

    if (conf->prefer_server_ciphers) {
        SSL_CTX_set_options(conf->ssl.ctx, SSL_OP_CIPHER_SERVER_PREFERENCE);
    }

#if (OPENSSL_VERSION_NUMBER < 0x10100001L && !defined LIBRESSL_VERSION_NUMBER)
    SSL_CTX_set_tmp_rsa_callback(conf->ssl.ctx, ngx_ssl_rsa512_key_callback);
#endif

    if (ngx_ssl_dhparam(cf, &conf->ssl, &conf->dhparam) != NGX_OK) {
        return NGX_CONF_ERROR;
    }

    if (ngx_ssl_ecdh_curve(cf, &conf->ssl, &conf->ecdh_curve) != NGX_OK) {
        return NGX_CONF_ERROR;
    }

    ngx_conf_merge_value(conf->builtin_session_cache,
                         prev->builtin_session_cache, NGX_SSL_NONE_SCACHE);

    if (conf->shm_zone == NULL) {
        conf->shm_zone = prev->shm_zone;
    }

    if (ngx_ssl_session_cache(&conf->ssl, &ngx_mail_ssl_sess_id_ctx,
                              conf->builtin_session_cache,
                              conf->shm_zone, conf->session_timeout)
        != NGX_OK)
    {
        return NGX_CONF_ERROR;
    }

    ngx_conf_merge_value(conf->session_tickets,
                         prev->session_tickets, 1);

#ifdef SSL_OP_NO_TICKET
    if (!conf->session_tickets) {
        SSL_CTX_set_options(conf->ssl.ctx, SSL_OP_NO_TICKET);
    }
#endif

    ngx_conf_merge_ptr_value(conf->session_ticket_keys,
                         prev->session_ticket_keys, NULL);

    if (ngx_ssl_session_ticket_keys(cf, &conf->ssl, conf->session_ticket_keys)
        != NGX_OK)
    {
        return NGX_CONF_ERROR;
    }

    return NGX_CONF_OK;
}


static char *
ngx_mail_ssl_enable(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_mail_ssl_conf_t  *scf = conf;

    char  *rv;

    rv = ngx_conf_set_flag_slot(cf, cmd, conf);

    if (rv != NGX_CONF_OK) {
        return rv;
    }

    if (scf->enable && (ngx_int_t) scf->starttls > NGX_MAIL_STARTTLS_OFF) {
        ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                           "\"starttls\" directive conflicts with \"ssl on\"");
        return NGX_CONF_ERROR;
    }

    scf->file = cf->conf_file->file.name.data;
    scf->line = cf->conf_file->line;

    return NGX_CONF_OK;
}


static char *
ngx_mail_ssl_starttls(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_mail_ssl_conf_t  *scf = conf;

    char  *rv;

    rv = ngx_conf_set_enum_slot(cf, cmd, conf);

    if (rv != NGX_CONF_OK) {
        return rv;
    }

    if (scf->enable == 1 && (ngx_int_t) scf->starttls > NGX_MAIL_STARTTLS_OFF) {
        ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                           "\"ssl\" directive conflicts with \"starttls\"");
        return NGX_CONF_ERROR;
    }

    scf->file = cf->conf_file->file.name.data;
    scf->line = cf->conf_file->line;

    return NGX_CONF_OK;
}


static char *
ngx_mail_ssl_password_file(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_mail_ssl_conf_t  *scf = conf;

    ngx_str_t  *value;

    if (scf->passwords != NGX_CONF_UNSET_PTR) {
        return "is duplicate";
    }

    value = cf->args->elts;

    scf->passwords = ngx_ssl_read_password_file(cf, &value[1]);

    if (scf->passwords == NULL) {
        return NGX_CONF_ERROR;
    }

    return NGX_CONF_OK;
}


static char *
ngx_mail_ssl_session_cache(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_mail_ssl_conf_t  *scf = conf;

    size_t       len;
    ngx_str_t   *value, name, size;
    ngx_int_t    n;
    ngx_uint_t   i, j;

    value = cf->args->elts;

    for (i = 1; i < cf->args->nelts; i++) {

        if (ngx_strcmp(value[i].data, "off") == 0) {
            scf->builtin_session_cache = NGX_SSL_NO_SCACHE;
            continue;
        }

        if (ngx_strcmp(value[i].data, "none") == 0) {
            scf->builtin_session_cache = NGX_SSL_NONE_SCACHE;
            continue;
        }

        if (ngx_strcmp(value[i].data, "builtin") == 0) {
            scf->builtin_session_cache = NGX_SSL_DFLT_BUILTIN_SCACHE;
            continue;
        }

        if (value[i].len > sizeof("builtin:") - 1
            && ngx_strncmp(value[i].data, "builtin:", sizeof("builtin:") - 1)
               == 0)
        {
            n = ngx_atoi(value[i].data + sizeof("builtin:") - 1,
                         value[i].len - (sizeof("builtin:") - 1));

            if (n == NGX_ERROR) {
                goto invalid;
            }

            scf->builtin_session_cache = n;

            continue;
        }

        if (value[i].len > sizeof("shared:") - 1
            && ngx_strncmp(value[i].data, "shared:", sizeof("shared:") - 1)
               == 0)
        {
            len = 0;

            for (j = sizeof("shared:") - 1; j < value[i].len; j++) {
                if (value[i].data[j] == ':') {
                    break;
                }

                len++;
            }

            if (len == 0) {
                goto invalid;
            }

            name.len = len;
            name.data = value[i].data + sizeof("shared:") - 1;

            size.len = value[i].len - j - 1;
            size.data = name.data + len + 1;

            n = ngx_parse_size(&size);

            if (n == NGX_ERROR) {
                goto invalid;
            }

            if (n < (ngx_int_t) (8 * ngx_pagesize)) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "session cache \"%V\" is too small",
                                   &value[i]);

                return NGX_CONF_ERROR;
            }

            scf->shm_zone = ngx_shared_memory_add(cf, &name, n,
                                                   &ngx_mail_ssl_module);
            if (scf->shm_zone == NULL) {
                return NGX_CONF_ERROR;
            }

            scf->shm_zone->init = ngx_ssl_session_cache_init;

            continue;
        }

        goto invalid;
    }

    if (scf->shm_zone && scf->builtin_session_cache == NGX_CONF_UNSET) {
        scf->builtin_session_cache = NGX_SSL_NO_BUILTIN_SCACHE;
    }

    return NGX_CONF_OK;

invalid:

    ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                       "invalid session cache \"%V\"", &value[i]);

    return NGX_CONF_ERROR;
}