text: 
  /*
   * Copyright (C) Igor Sysoev
   * Copyright (C) Nginx, Inc.
   */
  
  
  #include <ngx_config.h>
  #include <ngx_core.h>
  #include <ngx_event.h>
  #include <ngx_event_connect.h>
  #include <ngx_mail.h>
  
  
  typedef struct {
      ngx_flag_t  enable;
      ngx_flag_t  pass_error_message;
      ngx_flag_t  xclient;
      ngx_flag_t  smtp_auth;
      ngx_flag_t  proxy_protocol;
      size_t      buffer_size;
      ngx_msec_t  timeout;
  } ngx_mail_proxy_conf_t;
  
  
  static void ngx_mail_proxy_block_read(ngx_event_t *rev);
  static void ngx_mail_proxy_pop3_handler(ngx_event_t *rev);
  static void ngx_mail_proxy_imap_handler(ngx_event_t *rev);
  static void ngx_mail_proxy_smtp_handler(ngx_event_t *rev);
  static void ngx_mail_proxy_write_handler(ngx_event_t *wev);
  static ngx_int_t ngx_mail_proxy_send_proxy_protocol(ngx_mail_session_t *s);
  static ngx_int_t ngx_mail_proxy_read_response(ngx_mail_session_t *s,
      ngx_uint_t state);
  static void ngx_mail_proxy_handler(ngx_event_t *ev);
  static void ngx_mail_proxy_upstream_error(ngx_mail_session_t *s);
  static void ngx_mail_proxy_internal_server_error(ngx_mail_session_t *s);
  static void ngx_mail_proxy_close_session(ngx_mail_session_t *s);
  static void *ngx_mail_proxy_create_conf(ngx_conf_t *cf);
  static char *ngx_mail_proxy_merge_conf(ngx_conf_t *cf, void *parent,
      void *child);
  
  
  static ngx_command_t  ngx_mail_proxy_commands[] = {
  
      { ngx_string("proxy"),
        NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
        ngx_conf_set_flag_slot,
        NGX_MAIL_SRV_CONF_OFFSET,
        offsetof(ngx_mail_proxy_conf_t, enable),
        NULL },
  
      { ngx_string("proxy_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_proxy_conf_t, buffer_size),
        NULL },
  
      { ngx_string("proxy_timeout"),
        NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_TAKE1,
        ngx_conf_set_msec_slot,
        NGX_MAIL_SRV_CONF_OFFSET,
        offsetof(ngx_mail_proxy_conf_t, timeout),
        NULL },
  
      { ngx_string("proxy_pass_error_message"),
        NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
        ngx_conf_set_flag_slot,
        NGX_MAIL_SRV_CONF_OFFSET,
        offsetof(ngx_mail_proxy_conf_t, pass_error_message),
        NULL },
  
      { ngx_string("xclient"),
        NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
        ngx_conf_set_flag_slot,
        NGX_MAIL_SRV_CONF_OFFSET,
        offsetof(ngx_mail_proxy_conf_t, xclient),
        NULL },
  
      { ngx_string("proxy_smtp_auth"),
        NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
        ngx_conf_set_flag_slot,
        NGX_MAIL_SRV_CONF_OFFSET,
        offsetof(ngx_mail_proxy_conf_t, smtp_auth),
        NULL },
  
      { ngx_string("proxy_protocol"),
        NGX_MAIL_MAIN_CONF|NGX_MAIL_SRV_CONF|NGX_CONF_FLAG,
        ngx_conf_set_flag_slot,
        NGX_MAIL_SRV_CONF_OFFSET,
        offsetof(ngx_mail_proxy_conf_t, proxy_protocol),
        NULL },
  
        ngx_null_command
  };
  
  
  static ngx_mail_module_t  ngx_mail_proxy_module_ctx = {
      NULL,                                  /* protocol */
  
      NULL,                                  /* create main configuration */
      NULL,                                  /* init main configuration */
  
      ngx_mail_proxy_create_conf,            /* create server configuration */
      ngx_mail_proxy_merge_conf              /* merge server configuration */
  };
  
  
  ngx_module_t  ngx_mail_proxy_module = {
      NGX_MODULE_V1,
      &ngx_mail_proxy_module_ctx,            /* module context */
      ngx_mail_proxy_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 u_char  smtp_auth_ok[] = "235 2.0.0 OK" CRLF;
  
  
  void
  ngx_mail_proxy_init(ngx_mail_session_t *s, ngx_addr_t *peer)
  {
      ngx_int_t                  rc;
      ngx_mail_proxy_ctx_t      *p;
      ngx_mail_proxy_conf_t     *pcf;
      ngx_mail_core_srv_conf_t  *cscf;
  
      s->connection->log->action = "connecting to upstream";
  
      cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);
  
      p = ngx_pcalloc(s->connection->pool, sizeof(ngx_mail_proxy_ctx_t));
      if (p == NULL) {
          ngx_mail_session_internal_server_error(s);
          return;
      }
  
      s->proxy = p;
  
      p->upstream.sockaddr = peer->sockaddr;
      p->upstream.socklen = peer->socklen;
      p->upstream.name = &peer->name;
      p->upstream.get = ngx_event_get_peer;
      p->upstream.log = s->connection->log;
      p->upstream.log_error = NGX_ERROR_ERR;
  
      rc = ngx_event_connect_peer(&p->upstream);
  
      if (rc == NGX_ERROR || rc == NGX_BUSY || rc == NGX_DECLINED) {
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      ngx_add_timer(p->upstream.connection->read, cscf->timeout);
  
      p->upstream.connection->data = s;
      p->upstream.connection->pool = s->connection->pool;
  
      s->connection->read->handler = ngx_mail_proxy_block_read;
      p->upstream.connection->write->handler = ngx_mail_proxy_write_handler;
  
      pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
  
      s->proxy->buffer = ngx_create_temp_buf(s->connection->pool,
                                             pcf->buffer_size);
      if (s->proxy->buffer == NULL) {
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      s->proxy->proxy_protocol = pcf->proxy_protocol;
  
      s->out.len = 0;
  
      switch (s->protocol) {
  
      case NGX_MAIL_POP3_PROTOCOL:
          p->upstream.connection->read->handler = ngx_mail_proxy_pop3_handler;
          s->mail_state = ngx_pop3_start;
          break;
  
      case NGX_MAIL_IMAP_PROTOCOL:
          p->upstream.connection->read->handler = ngx_mail_proxy_imap_handler;
          s->mail_state = ngx_imap_start;
          break;
  
      default: /* NGX_MAIL_SMTP_PROTOCOL */
          p->upstream.connection->read->handler = ngx_mail_proxy_smtp_handler;
          s->mail_state = ngx_smtp_start;
          break;
      }
  
      if (rc == NGX_AGAIN) {
          return;
      }
  
      ngx_mail_proxy_write_handler(p->upstream.connection->write);
  }
  
  
  static void
  ngx_mail_proxy_block_read(ngx_event_t *rev)
  {
      ngx_connection_t    *c;
      ngx_mail_session_t  *s;
  
      ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy block read");
  
      if (ngx_handle_read_event(rev, 0) != NGX_OK) {
          c = rev->data;
          s = c->data;
  
          ngx_mail_proxy_close_session(s);
      }
  }
  
  
  static void
  ngx_mail_proxy_pop3_handler(ngx_event_t *rev)
  {
      u_char                 *p;
      ngx_int_t               rc;
      ngx_str_t               line;
      ngx_connection_t       *c;
      ngx_mail_session_t     *s;
      ngx_mail_proxy_conf_t  *pcf;
  
      ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                     "mail proxy pop3 auth handler");
  
      c = rev->data;
      s = c->data;
  
      if (rev->timedout) {
          ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
                        "upstream timed out");
          c->timedout = 1;
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      if (s->proxy->proxy_protocol) {
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "mail proxy pop3 busy");
  
          if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          return;
      }
  
      rc = ngx_mail_proxy_read_response(s, 0);
  
      if (rc == NGX_AGAIN) {
          if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          return;
      }
  
      if (rc == NGX_ERROR) {
          ngx_mail_proxy_upstream_error(s);
          return;
      }
  
      switch (s->mail_state) {
  
      case ngx_pop3_start:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send user");
  
          s->connection->log->action = "sending user name to upstream";
  
          line.len = sizeof("USER ")  - 1 + s->login.len + 2;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          p = ngx_cpymem(line.data, "USER ", sizeof("USER ") - 1);
          p = ngx_cpymem(p, s->login.data, s->login.len);
          *p++ = CR; *p = LF;
  
          s->mail_state = ngx_pop3_user;
          break;
  
      case ngx_pop3_user:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send pass");
  
          s->connection->log->action = "sending password to upstream";
  
          line.len = sizeof("PASS ")  - 1 + s->passwd.len + 2;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          p = ngx_cpymem(line.data, "PASS ", sizeof("PASS ") - 1);
          p = ngx_cpymem(p, s->passwd.data, s->passwd.len);
          *p++ = CR; *p = LF;
  
          s->mail_state = ngx_pop3_passwd;
          break;
  
      case ngx_pop3_passwd:
          s->connection->read->handler = ngx_mail_proxy_handler;
          s->connection->write->handler = ngx_mail_proxy_handler;
          rev->handler = ngx_mail_proxy_handler;
          c->write->handler = ngx_mail_proxy_handler;
  
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
          ngx_add_timer(s->connection->read, pcf->timeout);
          ngx_del_timer(c->read);
  
          c->log->action = NULL;
          ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
  
          ngx_mail_proxy_handler(s->connection->write);
  
          return;
  
      default:
  #if (NGX_SUPPRESS_WARN)
          ngx_str_null(&line);
  #endif
          break;
      }
  
      if (c->send(c, line.data, line.len) < (ssize_t) line.len) {
          /*
           * we treat the incomplete sending as NGX_ERROR
           * because it is very strange here
           */
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      s->proxy->buffer->pos = s->proxy->buffer->start;
      s->proxy->buffer->last = s->proxy->buffer->start;
  }
  
  
  static void
  ngx_mail_proxy_imap_handler(ngx_event_t *rev)
  {
      u_char                 *p;
      ngx_int_t               rc;
      ngx_str_t               line;
      ngx_connection_t       *c;
      ngx_mail_session_t     *s;
      ngx_mail_proxy_conf_t  *pcf;
  
      ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                     "mail proxy imap auth handler");
  
      c = rev->data;
      s = c->data;
  
      if (rev->timedout) {
          ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
                        "upstream timed out");
          c->timedout = 1;
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      if (s->proxy->proxy_protocol) {
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "mail proxy imap busy");
  
          if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          return;
      }
  
      rc = ngx_mail_proxy_read_response(s, s->mail_state);
  
      if (rc == NGX_AGAIN) {
          if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          return;
      }
  
      if (rc == NGX_ERROR) {
          ngx_mail_proxy_upstream_error(s);
          return;
      }
  
      switch (s->mail_state) {
  
      case ngx_imap_start:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send login");
  
          s->connection->log->action = "sending LOGIN command to upstream";
  
          line.len = s->tag.len + sizeof("LOGIN ") - 1
                     + 1 + NGX_SIZE_T_LEN + 1 + 2;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          line.len = ngx_sprintf(line.data, "%VLOGIN {%uz}" CRLF,
                                 &s->tag, s->login.len)
                     - line.data;
  
          s->mail_state = ngx_imap_login;
          break;
  
      case ngx_imap_login:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send user");
  
          s->connection->log->action = "sending user name to upstream";
  
          line.len = s->login.len + 1 + 1 + NGX_SIZE_T_LEN + 1 + 2;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          line.len = ngx_sprintf(line.data, "%V {%uz}" CRLF,
                                 &s->login, s->passwd.len)
                     - line.data;
  
          s->mail_state = ngx_imap_user;
          break;
  
      case ngx_imap_user:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send passwd");
  
          s->connection->log->action = "sending password to upstream";
  
          line.len = s->passwd.len + 2;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          p = ngx_cpymem(line.data, s->passwd.data, s->passwd.len);
          *p++ = CR; *p = LF;
  
          s->mail_state = ngx_imap_passwd;
          break;
  
      case ngx_imap_passwd:
          s->connection->read->handler = ngx_mail_proxy_handler;
          s->connection->write->handler = ngx_mail_proxy_handler;
          rev->handler = ngx_mail_proxy_handler;
          c->write->handler = ngx_mail_proxy_handler;
  
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
          ngx_add_timer(s->connection->read, pcf->timeout);
          ngx_del_timer(c->read);
  
          c->log->action = NULL;
          ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
  
          ngx_mail_proxy_handler(s->connection->write);
  
          return;
  
      default:
  #if (NGX_SUPPRESS_WARN)
          ngx_str_null(&line);
  #endif
          break;
      }
  
      if (c->send(c, line.data, line.len) < (ssize_t) line.len) {
          /*
           * we treat the incomplete sending as NGX_ERROR
           * because it is very strange here
           */
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      s->proxy->buffer->pos = s->proxy->buffer->start;
      s->proxy->buffer->last = s->proxy->buffer->start;
  }
  
  
  static void
  ngx_mail_proxy_smtp_handler(ngx_event_t *rev)
  {
      u_char                    *p;
      ngx_int_t                  rc;
      ngx_str_t                  line, auth, encoded;
      ngx_buf_t                 *b;
      ngx_connection_t          *c;
      ngx_mail_session_t        *s;
      ngx_mail_proxy_conf_t     *pcf;
      ngx_mail_core_srv_conf_t  *cscf;
  
      ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                     "mail proxy smtp auth handler");
  
      c = rev->data;
      s = c->data;
  
      if (rev->timedout) {
          ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
                        "upstream timed out");
          c->timedout = 1;
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      if (s->proxy->proxy_protocol) {
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "mail proxy smtp busy");
  
          if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          return;
      }
  
      rc = ngx_mail_proxy_read_response(s, s->mail_state);
  
      if (rc == NGX_AGAIN) {
          if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          return;
      }
  
      if (rc == NGX_ERROR) {
          ngx_mail_proxy_upstream_error(s);
          return;
      }
  
      switch (s->mail_state) {
  
      case ngx_smtp_start:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0, "mail proxy send ehlo");
  
          s->connection->log->action = "sending HELO/EHLO to upstream";
  
          cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);
  
          line.len = sizeof("HELO ")  - 1 + cscf->server_name.len + 2;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
  
          p = ngx_cpymem(line.data,
                         ((s->esmtp || pcf->xclient) ? "EHLO " : "HELO "),
                         sizeof("HELO ") - 1);
  
          p = ngx_cpymem(p, cscf->server_name.data, cscf->server_name.len);
          *p++ = CR; *p = LF;
  
          if (pcf->xclient) {
              s->mail_state = ngx_smtp_helo_xclient;
  
          } else if (s->auth_method == NGX_MAIL_AUTH_NONE) {
              s->mail_state = ngx_smtp_helo_from;
  
          } else if (pcf->smtp_auth) {
              s->mail_state = ngx_smtp_helo_auth;
  
          } else {
              s->mail_state = ngx_smtp_helo;
          }
  
          break;
  
      case ngx_smtp_helo_xclient:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send xclient");
  
          s->connection->log->action = "sending XCLIENT to upstream";
  
          line.len = sizeof("XCLIENT ADDR= LOGIN= NAME="
                            CRLF) - 1
                     + s->connection->addr_text.len + s->login.len + s->host.len;
  
  #if (NGX_HAVE_INET6)
          if (s->connection->sockaddr->sa_family == AF_INET6) {
              line.len += sizeof("IPV6:") - 1;
          }
  #endif
  
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          p = ngx_cpymem(line.data, "XCLIENT ADDR=", sizeof("XCLIENT ADDR=") - 1);
  
  #if (NGX_HAVE_INET6)
          if (s->connection->sockaddr->sa_family == AF_INET6) {
              p = ngx_cpymem(p, "IPV6:", sizeof("IPV6:") - 1);
          }
  #endif
  
          p = ngx_copy(p, s->connection->addr_text.data,
                       s->connection->addr_text.len);
  
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
  
          if (s->login.len && !pcf->smtp_auth) {
              p = ngx_cpymem(p, " LOGIN=", sizeof(" LOGIN=") - 1);
              p = ngx_copy(p, s->login.data, s->login.len);
          }
  
          p = ngx_cpymem(p, " NAME=", sizeof(" NAME=") - 1);
          p = ngx_copy(p, s->host.data, s->host.len);
  
          *p++ = CR; *p++ = LF;
  
          line.len = p - line.data;
  
          if (s->smtp_helo.len) {
              s->mail_state = ngx_smtp_xclient_helo;
  
          } else if (s->auth_method == NGX_MAIL_AUTH_NONE) {
              s->mail_state = ngx_smtp_xclient_from;
  
          } else if (pcf->smtp_auth) {
              s->mail_state = ngx_smtp_xclient_auth;
  
          } else {
              s->mail_state = ngx_smtp_xclient;
          }
  
          break;
  
      case ngx_smtp_xclient_helo:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send client ehlo");
  
          s->connection->log->action = "sending client HELO/EHLO to upstream";
  
          line.len = sizeof("HELO " CRLF) - 1 + s->smtp_helo.len;
  
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          line.len = ngx_sprintf(line.data,
                         ((s->esmtp) ? "EHLO %V" CRLF : "HELO %V" CRLF),
                         &s->smtp_helo)
                     - line.data;
  
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
  
          if (s->auth_method == NGX_MAIL_AUTH_NONE) {
              s->mail_state = ngx_smtp_helo_from;
  
          } else if (pcf->smtp_auth) {
              s->mail_state = ngx_smtp_helo_auth;
  
          } else {
              s->mail_state = ngx_smtp_helo;
          }
  
          break;
  
      case ngx_smtp_helo_auth:
      case ngx_smtp_xclient_auth:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send auth");
  
          s->connection->log->action = "sending AUTH to upstream";
  
          if (s->passwd.data == NULL) {
              ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
                            "no password available");
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          auth.len = 1 + s->login.len + 1 + s->passwd.len;
          auth.data = ngx_pnalloc(c->pool, auth.len);
          if (auth.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          auth.len = ngx_sprintf(auth.data, "%Z%V%Z%V", &s->login, &s->passwd)
                     - auth.data;
  
          line.len = sizeof("AUTH PLAIN " CRLF) - 1
                     + ngx_base64_encoded_length(auth.len);
  
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          encoded.data = ngx_cpymem(line.data, "AUTH PLAIN ",
                                    sizeof("AUTH PLAIN ") - 1);
  
          ngx_encode_base64(&encoded, &auth);
  
          p = encoded.data + encoded.len;
          *p++ = CR; *p = LF;
  
          s->mail_state = ngx_smtp_auth_plain;
  
          break;
  
      case ngx_smtp_helo_from:
      case ngx_smtp_xclient_from:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send mail from");
  
          s->connection->log->action = "sending MAIL FROM to upstream";
  
          line.len = s->smtp_from.len + sizeof(CRLF) - 1;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          p = ngx_cpymem(line.data, s->smtp_from.data, s->smtp_from.len);
          *p++ = CR; *p = LF;
  
          s->mail_state = ngx_smtp_from;
  
          break;
  
      case ngx_smtp_from:
          ngx_log_debug0(NGX_LOG_DEBUG_MAIL, rev->log, 0,
                         "mail proxy send rcpt to");
  
          s->connection->log->action = "sending RCPT TO to upstream";
  
          line.len = s->smtp_to.len + sizeof(CRLF) - 1;
          line.data = ngx_pnalloc(c->pool, line.len);
          if (line.data == NULL) {
              ngx_mail_proxy_internal_server_error(s);
              return;
          }
  
          p = ngx_cpymem(line.data, s->smtp_to.data, s->smtp_to.len);
          *p++ = CR; *p = LF;
  
          s->mail_state = ngx_smtp_to;
  
          break;
  
      case ngx_smtp_helo:
      case ngx_smtp_xclient:
      case ngx_smtp_auth_plain:
      case ngx_smtp_to:
  
          b = s->proxy->buffer;
  
          if (s->auth_method == NGX_MAIL_AUTH_NONE) {
              b->pos = b->start;
  
          } else {
              ngx_memcpy(b->start, smtp_auth_ok, sizeof(smtp_auth_ok) - 1);
              b->last = b->start + sizeof(smtp_auth_ok) - 1;
          }
  
          s->connection->read->handler = ngx_mail_proxy_handler;
          s->connection->write->handler = ngx_mail_proxy_handler;
          rev->handler = ngx_mail_proxy_handler;
          c->write->handler = ngx_mail_proxy_handler;
  
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
          ngx_add_timer(s->connection->read, pcf->timeout);
          ngx_del_timer(c->read);
  
          c->log->action = NULL;
          ngx_log_error(NGX_LOG_INFO, c->log, 0, "client logged in");
  
          if (s->buffer->pos == s->buffer->last) {
              ngx_mail_proxy_handler(s->connection->write);
  
          } else {
              ngx_mail_proxy_handler(c->write);
          }
  
          return;
  
      default:
  #if (NGX_SUPPRESS_WARN)
          ngx_str_null(&line);
  #endif
          break;
      }
  
      if (c->send(c, line.data, line.len) < (ssize_t) line.len) {
          /*
           * we treat the incomplete sending as NGX_ERROR
           * because it is very strange here
           */
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
          ngx_mail_proxy_internal_server_error(s);
          return;
      }
  
      s->proxy->buffer->pos = s->proxy->buffer->start;
      s->proxy->buffer->last = s->proxy->buffer->start;
  }
  
  
  static void
  ngx_mail_proxy_write_handler(ngx_event_t *wev)
  {
      ngx_connection_t    *c;
      ngx_mail_session_t  *s;
  
      ngx_log_debug0(NGX_LOG_DEBUG_MAIL, wev->log, 0, "mail proxy write handler");
  
      c = wev->data;
      s = c->data;
  
      if (s->proxy->proxy_protocol) {
          if (ngx_mail_proxy_send_proxy_protocol(s) != NGX_OK) {
              return;
          }
  
          s->proxy->proxy_protocol = 0;
      }
  
      if (ngx_handle_write_event(wev, 0) != NGX_OK) {
          ngx_mail_proxy_internal_server_error(s);
      }
  
      if (c->read->ready) {
          ngx_post_event(c->read, &ngx_posted_events);
      }
  }
  
  
  static ngx_int_t
  ngx_mail_proxy_send_proxy_protocol(ngx_mail_session_t *s)
  {
      u_char            *p;
      ssize_t            n, size;
      ngx_connection_t  *c;
      u_char             buf[NGX_PROXY_PROTOCOL_MAX_HEADER];
  
      s->connection->log->action = "sending PROXY protocol header to upstream";
  
      ngx_log_debug0(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
                     "mail proxy send PROXY protocol header");
  
      p = ngx_proxy_protocol_write(s->connection, buf,
                                   buf + NGX_PROXY_PROTOCOL_MAX_HEADER);
      if (p == NULL) {
          ngx_mail_proxy_internal_server_error(s);
          return NGX_ERROR;
      }
  
      c = s->proxy->upstream.connection;
  
      size = p - buf;
  
      n = c->send(c, buf, size);
  
      if (n == NGX_AGAIN) {
          if (ngx_handle_write_event(c->write, 0) != NGX_OK) {
              ngx_mail_proxy_internal_server_error(s);
              return NGX_ERROR;
          }
  
          return NGX_AGAIN;
      }
  
      if (n == NGX_ERROR) {
          ngx_mail_proxy_internal_server_error(s);
          return NGX_ERROR;
      }
  
      if (n != size) {
  
          /*
           * PROXY protocol specification:
           * The sender must always ensure that the header
           * is sent at once, so that the transport layer
           * maintains atomicity along the path to the receiver.
           */
  
          ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
                        "could not send PROXY protocol header at once");
  
          ngx_mail_proxy_internal_server_error(s);
  
          return NGX_ERROR;
      }
  
      return NGX_OK;
  }
  
  
  static ngx_int_t
  ngx_mail_proxy_read_response(ngx_mail_session_t *s, ngx_uint_t state)
  {
      u_char                 *p, *m;
      ssize_t                 n;
      ngx_buf_t              *b;
      ngx_mail_proxy_conf_t  *pcf;
  
      s->connection->log->action = "reading response from upstream";
  
      b = s->proxy->buffer;
  
      n = s->proxy->upstream.connection->recv(s->proxy->upstream.connection,
                                              b->last, b->end - b->last);
  
      if (n == NGX_ERROR || n == 0) {
          return NGX_ERROR;
      }
  
      if (n == NGX_AGAIN) {
          return NGX_AGAIN;
      }
  
      b->last += n;
  
      if (b->last - b->pos < 4) {
          return NGX_AGAIN;
      }
  
      if (*(b->last - 2) != CR || *(b->last - 1) != LF) {
          if (b->last == b->end) {
              *(b->last - 1) = '\0';
              ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
                            "upstream sent too long response line: \"%s\"",
                            b->pos);
              return NGX_ERROR;
          }
  
          return NGX_AGAIN;
      }
  
      p = b->pos;
  
      switch (s->protocol) {
  
      case NGX_MAIL_POP3_PROTOCOL:
          if (p[0] == '+' && p[1] == 'O' && p[2] == 'K') {
              return NGX_OK;
          }
          break;
  
      case NGX_MAIL_IMAP_PROTOCOL:
          switch (state) {
  
          case ngx_imap_start:
              if (p[0] == '*' && p[1] == ' ' && p[2] == 'O' && p[3] == 'K') {
                  return NGX_OK;
              }
              break;
  
          case ngx_imap_login:
          case ngx_imap_user:
              if (p[0] == '+') {
                  return NGX_OK;
              }
              break;
  
          case ngx_imap_passwd:
              if (ngx_strncmp(p, s->tag.data, s->tag.len) == 0) {
                  p += s->tag.len;
                  if (p[0] == 'O' && p[1] == 'K') {
                      return NGX_OK;
                  }
              }
              break;
          }
  
          break;
  
      default: /* NGX_MAIL_SMTP_PROTOCOL */
  
          if (p[3] == '-') {
              /* multiline reply, check if we got last line */
  
              m = b->last - (sizeof(CRLF "200" CRLF) - 1);
  
              while (m > p) {
                  if (m[0] == CR && m[1] == LF) {
                      break;
                  }
  
                  m--;
              }
  
              if (m <= p || m[5] == '-') {
                  return NGX_AGAIN;
              }
          }
  
          switch (state) {
  
          case ngx_smtp_start:
              if (p[0] == '2' && p[1] == '2' && p[2] == '0') {
                  return NGX_OK;
              }
              break;
  
          case ngx_smtp_helo:
          case ngx_smtp_helo_xclient:
          case ngx_smtp_helo_from:
          case ngx_smtp_helo_auth:
          case ngx_smtp_from:
              if (p[0] == '2' && p[1] == '5' && p[2] == '0') {
                  return NGX_OK;
              }
              break;
  
          case ngx_smtp_xclient:
          case ngx_smtp_xclient_from:
          case ngx_smtp_xclient_helo:
          case ngx_smtp_xclient_auth:
              if (p[0] == '2' && (p[1] == '2' || p[1] == '5') && p[2] == '0') {
                  return NGX_OK;
              }
              break;
  
          case ngx_smtp_auth_plain:
              if (p[0] == '2' && p[1] == '3' && p[2] == '5') {
                  return NGX_OK;
              }
              break;
  
          case ngx_smtp_to:
              return NGX_OK;
          }
  
          break;
      }
  
      pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
  
      if (pcf->pass_error_message == 0) {
          *(b->last - 2) = '\0';
          ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
                        "upstream sent invalid response: \"%s\"", p);
          return NGX_ERROR;
      }
  
      s->out.len = b->last - p - 2;
      s->out.data = p;
  
      ngx_log_error(NGX_LOG_INFO, s->connection->log, 0,
                    "upstream sent invalid response: \"%V\"", &s->out);
  
      s->out.len = b->last - b->pos;
      s->out.data = b->pos;
  
      return NGX_ERROR;
  }
  
  
  static void
  ngx_mail_proxy_handler(ngx_event_t *ev)
  {
      char                   *action, *recv_action, *send_action;
      size_t                  size;
      ssize_t                 n;
      ngx_buf_t              *b;
      ngx_uint_t              do_write;
      ngx_connection_t       *c, *src, *dst;
      ngx_mail_session_t     *s;
      ngx_mail_proxy_conf_t  *pcf;
  
      c = ev->data;
      s = c->data;
  
      if (ev->timedout || c->close) {
          c->log->action = "proxying";
  
          if (c->close) {
              ngx_log_error(NGX_LOG_INFO, c->log, 0, "shutdown timeout");
  
          } else if (c == s->connection) {
              ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
                            "client timed out");
              c->timedout = 1;
  
          } else {
              ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT,
                            "upstream timed out");
          }
  
          ngx_mail_proxy_close_session(s);
          return;
      }
  
      if (c == s->connection) {
          if (ev->write) {
              recv_action = "proxying and reading from upstream";
              send_action = "proxying and sending to client";
              src = s->proxy->upstream.connection;
              dst = c;
              b = s->proxy->buffer;
  
          } else {
              recv_action = "proxying and reading from client";
              send_action = "proxying and sending to upstream";
              src = c;
              dst = s->proxy->upstream.connection;
              b = s->buffer;
          }
  
      } else {
          if (ev->write) {
              recv_action = "proxying and reading from client";
              send_action = "proxying and sending to upstream";
              src = s->connection;
              dst = c;
              b = s->buffer;
  
          } else {
              recv_action = "proxying and reading from upstream";
              send_action = "proxying and sending to client";
              src = c;
              dst = s->connection;
              b = s->proxy->buffer;
          }
      }
  
      do_write = ev->write ? 1 : 0;
  
      ngx_log_debug3(NGX_LOG_DEBUG_MAIL, ev->log, 0,
                     "mail proxy handler: %ui, #%d > #%d",
                     do_write, src->fd, dst->fd);
  
      for ( ;; ) {
  
          if (do_write) {
  
              size = b->last - b->pos;
  
              if (size && dst->write->ready) {
                  c->log->action = send_action;
  
                  n = dst->send(dst, b->pos, size);
  
                  if (n == NGX_ERROR) {
                      ngx_mail_proxy_close_session(s);
                      return;
                  }
  
                  if (n > 0) {
                      b->pos += n;
  
                      if (b->pos == b->last) {
                          b->pos = b->start;
                          b->last = b->start;
                      }
                  }
              }
          }
  
          size = b->end - b->last;
  
          if (size && src->read->ready) {
              c->log->action = recv_action;
  
              n = src->recv(src, b->last, size);
  
              if (n == NGX_AGAIN || n == 0) {
                  break;
              }
  
              if (n > 0) {
                  do_write = 1;
                  b->last += n;
  
                  continue;
              }
  
              if (n == NGX_ERROR) {
                  src->read->eof = 1;
              }
          }
  
          break;
      }
  
      c->log->action = "proxying";
  
      if ((s->connection->read->eof && s->buffer->pos == s->buffer->last)
          || (s->proxy->upstream.connection->read->eof
              && s->proxy->buffer->pos == s->proxy->buffer->last)
          || (s->connection->read->eof
              && s->proxy->upstream.connection->read->eof))
      {
          action = c->log->action;
          c->log->action = NULL;
          ngx_log_error(NGX_LOG_INFO, c->log, 0, "proxied session done");
          c->log->action = action;
  
          ngx_mail_proxy_close_session(s);
          return;
      }
  
      if (ngx_handle_write_event(dst->write, 0) != NGX_OK) {
          ngx_mail_proxy_close_session(s);
          return;
      }
  
      if (ngx_handle_read_event(dst->read, 0) != NGX_OK) {
          ngx_mail_proxy_close_session(s);
          return;
      }
  
      if (ngx_handle_write_event(src->write, 0) != NGX_OK) {
          ngx_mail_proxy_close_session(s);
          return;
      }
  
      if (ngx_handle_read_event(src->read, 0) != NGX_OK) {
          ngx_mail_proxy_close_session(s);
          return;
      }
  
      if (c == s->connection) {
          pcf = ngx_mail_get_module_srv_conf(s, ngx_mail_proxy_module);
          ngx_add_timer(c->read, pcf->timeout);
      }
  }
  
  
  static void
  ngx_mail_proxy_upstream_error(ngx_mail_session_t *s)
  {
      if (s->proxy->upstream.connection) {
          ngx_log_debug1(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
                         "close mail proxy connection: %d",
                         s->proxy->upstream.connection->fd);
  
          ngx_close_connection(s->proxy->upstream.connection);
      }
  
      if (s->out.len == 0) {
          ngx_mail_session_internal_server_error(s);
          return;
      }
  
      s->quit = 1;
      ngx_mail_send(s->connection->write);
  }
  
  
  static void
  ngx_mail_proxy_internal_server_error(ngx_mail_session_t *s)
  {
      if (s->proxy->upstream.connection) {
          ngx_log_debug1(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
                         "close mail proxy connection: %d",
                         s->proxy->upstream.connection->fd);
  
          ngx_close_connection(s->proxy->upstream.connection);
      }
  
      ngx_mail_session_internal_server_error(s);
  }
  
  
  static void
  ngx_mail_proxy_close_session(ngx_mail_session_t *s)
  {
      if (s->proxy->upstream.connection) {
          ngx_log_debug1(NGX_LOG_DEBUG_MAIL, s->connection->log, 0,
                         "close mail proxy connection: %d",
                         s->proxy->upstream.connection->fd);
  
          ngx_close_connection(s->proxy->upstream.connection);
      }
  
      ngx_mail_close_connection(s->connection);
  }
  
  
  static void *
  ngx_mail_proxy_create_conf(ngx_conf_t *cf)
  {
      ngx_mail_proxy_conf_t  *pcf;
  
      pcf = ngx_pcalloc(cf->pool, sizeof(ngx_mail_proxy_conf_t));
      if (pcf == NULL) {
          return NULL;
      }
  
      pcf->enable = NGX_CONF_UNSET;
      pcf->pass_error_message = NGX_CONF_UNSET;
      pcf->xclient = NGX_CONF_UNSET;
      pcf->smtp_auth = NGX_CONF_UNSET;
      pcf->proxy_protocol = NGX_CONF_UNSET;
      pcf->buffer_size = NGX_CONF_UNSET_SIZE;
      pcf->timeout = NGX_CONF_UNSET_MSEC;
  
      return pcf;
  }
  
  
  static char *
  ngx_mail_proxy_merge_conf(ngx_conf_t *cf, void *parent, void *child)
  {
      ngx_mail_proxy_conf_t *prev = parent;
      ngx_mail_proxy_conf_t *conf = child;
  
      ngx_conf_merge_value(conf->enable, prev->enable, 0);
      ngx_conf_merge_value(conf->pass_error_message, prev->pass_error_message, 0);
      ngx_conf_merge_value(conf->xclient, prev->xclient, 1);
      ngx_conf_merge_value(conf->smtp_auth, prev->smtp_auth, 0);
      ngx_conf_merge_value(conf->proxy_protocol, prev->proxy_protocol, 0);
      ngx_conf_merge_size_value(conf->buffer_size, prev->buffer_size,
                                (size_t) ngx_pagesize);
      ngx_conf_merge_msec_value(conf->timeout, prev->timeout, 24 * 60 * 60000);
  
      return NGX_CONF_OK;
  }
  