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view src/mail/ngx_mail_smtp_module.c @ 7674:7731c710796f

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Memcached: protect from too long responses. If a memcached response was followed by a correct trailer, and then the NUL character followed by some extra data - this was accepted by the trailer checking code. This in turn resulted in ctx->rest underflow and caused negative size buffer on the next reading from the upstream, followed by the "negative size buf in writer" alert. Fix is to always check for too long responses, so a correct trailer cannot be followed by extra data.
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 06 Jul 2020 18:36:17 +0300
parents f18c285c2e59
children dc955d274130
line wrap: on
line source


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


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


static void *ngx_mail_smtp_create_srv_conf(ngx_conf_t *cf);
static char *ngx_mail_smtp_merge_srv_conf(ngx_conf_t *cf, void *parent,
    void *child);


static ngx_conf_bitmask_t  ngx_mail_smtp_auth_methods[] = {
    { ngx_string("plain"), NGX_MAIL_AUTH_PLAIN_ENABLED },
    { ngx_string("login"), NGX_MAIL_AUTH_LOGIN_ENABLED },
    { ngx_string("cram-md5"), NGX_MAIL_AUTH_CRAM_MD5_ENABLED },
    { ngx_string("external"), NGX_MAIL_AUTH_EXTERNAL_ENABLED },
    { ngx_string("none"), NGX_MAIL_AUTH_NONE_ENABLED },
    { ngx_null_string, 0 }
};


static ngx_str_t  ngx_mail_smtp_auth_methods_names[] = {
    ngx_string("PLAIN"),
    ngx_string("LOGIN"),
    ngx_null_string,  /* APOP */
    ngx_string("CRAM-MD5"),
    ngx_string("EXTERNAL"),
    ngx_null_string   /* NONE */
};


static ngx_mail_protocol_t  ngx_mail_smtp_protocol = {
    ngx_string("smtp"),
    { 25, 465, 587, 0 },
    NGX_MAIL_SMTP_PROTOCOL,

    ngx_mail_smtp_init_session,
    ngx_mail_smtp_init_protocol,
    ngx_mail_smtp_parse_command,
    ngx_mail_smtp_auth_state,

    ngx_string("451 4.3.2 Internal server error" CRLF),
    ngx_string("421 4.7.1 SSL certificate error" CRLF),
    ngx_string("421 4.7.1 No required SSL certificate" CRLF)
};


static ngx_command_t  ngx_mail_smtp_commands[] = {

    { ngx_string("smtp_client_buffer"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_size_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_smtp_srv_conf_t, client_buffer_size),
      NULL },

    { ngx_string("smtp_greeting_delay"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_msec_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_smtp_srv_conf_t, greeting_delay),
      NULL },

    { ngx_string("smtp_capabilities"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_1MORE,
      ngx_mail_capabilities,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_smtp_srv_conf_t, capabilities),
      NULL },

    { ngx_string("smtp_auth"),
      NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_1MORE,
      ngx_conf_set_bitmask_slot,
      NGX_MAIL_SRV_CONF_OFFSET,
      offsetof(ngx_mail_smtp_srv_conf_t, auth_methods),
      &ngx_mail_smtp_auth_methods },

      ngx_null_command
};


static ngx_mail_module_t  ngx_mail_smtp_module_ctx = {
    &ngx_mail_smtp_protocol,               /* protocol */

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

    ngx_mail_smtp_create_srv_conf,         /* create server configuration */
    ngx_mail_smtp_merge_srv_conf           /* merge server configuration */
};


ngx_module_t  ngx_mail_smtp_module = {
    NGX_MODULE_V1,
    &ngx_mail_smtp_module_ctx,             /* module context */
    ngx_mail_smtp_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 void *
ngx_mail_smtp_create_srv_conf(ngx_conf_t *cf)
{
    ngx_mail_smtp_srv_conf_t  *sscf;

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

    sscf->client_buffer_size = NGX_CONF_UNSET_SIZE;
    sscf->greeting_delay = NGX_CONF_UNSET_MSEC;

    if (ngx_array_init(&sscf->capabilities, cf->pool, 4, sizeof(ngx_str_t))
        != NGX_OK)
    {
        return NULL;
    }

    return sscf;
}


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

    u_char                    *p, *auth, *last;
    size_t                     size;
    ngx_str_t                 *c;
    ngx_uint_t                 i, m, auth_enabled;
    ngx_mail_core_srv_conf_t  *cscf;

    ngx_conf_merge_size_value(conf->client_buffer_size,
                              prev->client_buffer_size,
                              (size_t) ngx_pagesize);

    ngx_conf_merge_msec_value(conf->greeting_delay,
                              prev->greeting_delay, 0);

    ngx_conf_merge_bitmask_value(conf->auth_methods,
                              prev->auth_methods,
                              (NGX_CONF_BITMASK_SET
                               |NGX_MAIL_AUTH_PLAIN_ENABLED
                               |NGX_MAIL_AUTH_LOGIN_ENABLED));


    cscf = ngx_mail_conf_get_module_srv_conf(cf, ngx_mail_core_module);

    size = sizeof("220  ESMTP ready" CRLF) - 1 + cscf->server_name.len;

    p = ngx_pnalloc(cf->pool, size);
    if (p == NULL) {
        return NGX_CONF_ERROR;
    }

    conf->greeting.len = size;
    conf->greeting.data = p;

    *p++ = '2'; *p++ = '2'; *p++ = '0'; *p++ = ' ';
    p = ngx_cpymem(p, cscf->server_name.data, cscf->server_name.len);
    ngx_memcpy(p, " ESMTP ready" CRLF, sizeof(" ESMTP ready" CRLF) - 1);


    size = sizeof("250 " CRLF) - 1 + cscf->server_name.len;

    p = ngx_pnalloc(cf->pool, size);
    if (p == NULL) {
        return NGX_CONF_ERROR;
    }

    conf->server_name.len = size;
    conf->server_name.data = p;

    *p++ = '2'; *p++ = '5'; *p++ = '0'; *p++ = ' ';
    p = ngx_cpymem(p, cscf->server_name.data, cscf->server_name.len);
    *p++ = CR; *p = LF;


    if (conf->capabilities.nelts == 0) {
        conf->capabilities = prev->capabilities;
    }

    size = sizeof("250-") - 1 + cscf->server_name.len + sizeof(CRLF) - 1;

    c = conf->capabilities.elts;
    for (i = 0; i < conf->capabilities.nelts; i++) {
        size += sizeof("250 ") - 1 + c[i].len + sizeof(CRLF) - 1;
    }

    auth_enabled = 0;

    for (m = NGX_MAIL_AUTH_PLAIN_ENABLED, i = 0;
         m <= NGX_MAIL_AUTH_EXTERNAL_ENABLED;
         m <<= 1, i++)
    {
        if (m & conf->auth_methods) {
            size += 1 + ngx_mail_smtp_auth_methods_names[i].len;
            auth_enabled = 1;
        }
    }

    if (auth_enabled) {
        size += sizeof("250 AUTH") - 1 + sizeof(CRLF) - 1;
    }

    p = ngx_pnalloc(cf->pool, size);
    if (p == NULL) {
        return NGX_CONF_ERROR;
    }

    conf->capability.len = size;
    conf->capability.data = p;

    last = p;

    *p++ = '2'; *p++ = '5'; *p++ = '0'; *p++ = '-';
    p = ngx_cpymem(p, cscf->server_name.data, cscf->server_name.len);
    *p++ = CR; *p++ = LF;

    for (i = 0; i < conf->capabilities.nelts; i++) {
        last = p;
        *p++ = '2'; *p++ = '5'; *p++ = '0'; *p++ = '-';
        p = ngx_cpymem(p, c[i].data, c[i].len);
        *p++ = CR; *p++ = LF;
    }

    auth = p;

    if (auth_enabled) {
        last = p;

        *p++ = '2'; *p++ = '5'; *p++ = '0'; *p++ = ' ';
        *p++ = 'A'; *p++ = 'U'; *p++ = 'T'; *p++ = 'H';

        for (m = NGX_MAIL_AUTH_PLAIN_ENABLED, i = 0;
             m <= NGX_MAIL_AUTH_EXTERNAL_ENABLED;
             m <<= 1, i++)
        {
            if (m & conf->auth_methods) {
                *p++ = ' ';
                p = ngx_cpymem(p, ngx_mail_smtp_auth_methods_names[i].data,
                               ngx_mail_smtp_auth_methods_names[i].len);
            }
        }

        *p++ = CR; *p = LF;

    } else {
        last[3] = ' ';
    }

    size += sizeof("250 STARTTLS" CRLF) - 1;

    p = ngx_pnalloc(cf->pool, size);
    if (p == NULL) {
        return NGX_CONF_ERROR;
    }

    conf->starttls_capability.len = size;
    conf->starttls_capability.data = p;

    p = ngx_cpymem(p, conf->capability.data, conf->capability.len);

    ngx_memcpy(p, "250 STARTTLS" CRLF, sizeof("250 STARTTLS" CRLF) - 1);

    p = conf->starttls_capability.data
        + (last - conf->capability.data) + 3;
    *p = '-';

    size = (auth - conf->capability.data)
            + sizeof("250 STARTTLS" CRLF) - 1;

    p = ngx_pnalloc(cf->pool, size);
    if (p == NULL) {
        return NGX_CONF_ERROR;
    }

    conf->starttls_only_capability.len = size;
    conf->starttls_only_capability.data = p;

    p = ngx_cpymem(p, conf->capability.data, auth - conf->capability.data);

    ngx_memcpy(p, "250 STARTTLS" CRLF, sizeof("250 STARTTLS" CRLF) - 1);

    if (last < auth) {
        p = conf->starttls_only_capability.data
            + (last - conf->capability.data) + 3;
        *p = '-';
    }

    return NGX_CONF_OK;
}