src/mail/ngx_mail_smtp_handler.c - net/nginx-mbedtls - Rivoreo Source Code Repositories


 /*
  * 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_resolve_addr_handler(ngx_resolver_ctx_t *ctx);
 static void ngx_mail_smtp_resolve_name(ngx_event_t *rev);
 static void ngx_mail_smtp_resolve_name_handler(ngx_resolver_ctx_t *ctx);
 static void ngx_mail_smtp_greeting(ngx_mail_session_t *s, ngx_connection_t *c);
 static void ngx_mail_smtp_invalid_pipelining(ngx_event_t *rev);
 static ngx_int_t ngx_mail_smtp_create_buffer(ngx_mail_session_t *s,
     ngx_connection_t *c);

 static ngx_int_t ngx_mail_smtp_helo(ngx_mail_session_t *s, ngx_connection_t *c);
 static ngx_int_t ngx_mail_smtp_auth(ngx_mail_session_t *s, ngx_connection_t *c);
 static ngx_int_t ngx_mail_smtp_mail(ngx_mail_session_t *s, ngx_connection_t *c);
 static ngx_int_t ngx_mail_smtp_starttls(ngx_mail_session_t *s,
     ngx_connection_t *c);
 static ngx_int_t ngx_mail_smtp_rset(ngx_mail_session_t *s, ngx_connection_t *c);
 static ngx_int_t ngx_mail_smtp_rcpt(ngx_mail_session_t *s, ngx_connection_t *c);

 static ngx_int_t ngx_mail_smtp_discard_command(ngx_mail_session_t *s,
     ngx_connection_t *c, char *err);
 static void ngx_mail_smtp_log_rejected_command(ngx_mail_session_t *s,
     ngx_connection_t *c, char *err);


 static u_char  smtp_ok[] = "250 2.0.0 OK" CRLF;
 static u_char  smtp_bye[] = "221 2.0.0 Bye" CRLF;
 static u_char  smtp_starttls[] = "220 2.0.0 Start TLS" CRLF;
 static u_char  smtp_next[] = "334 " CRLF;
 static u_char  smtp_username[] = "334 VXNlcm5hbWU6" CRLF;
 static u_char  smtp_password[] = "334 UGFzc3dvcmQ6" CRLF;
 static u_char  smtp_invalid_command[] = "500 5.5.1 Invalid command" CRLF;
 static u_char  smtp_invalid_pipelining[] =
    "503 5.5.0 Improper use of SMTP command pipelining" CRLF;
 static u_char  smtp_invalid_argument[] = "501 5.5.4 Invalid argument" CRLF;
 static u_char  smtp_auth_required[] = "530 5.7.1 Authentication required" CRLF;
 static u_char  smtp_bad_sequence[] = "503 5.5.1 Bad sequence of commands" CRLF;


 static ngx_str_t  smtp_unavailable = ngx_string("[UNAVAILABLE]");
 static ngx_str_t  smtp_tempunavail = ngx_string("[TEMPUNAVAIL]");


 void
 ngx_mail_smtp_init_session(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     struct sockaddr_in        *sin;
     ngx_resolver_ctx_t        *ctx;
     ngx_mail_core_srv_conf_t  *cscf;

     cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

     if (cscf->resolver == NULL) {
         s->host = smtp_unavailable;
         ngx_mail_smtp_greeting(s, c);
         return;
     }

     if (c->sockaddr->sa_family != AF_INET) {
         s->host = smtp_tempunavail;
         ngx_mail_smtp_greeting(s, c);
         return;
     }

     c->log->action = "in resolving client address";

     ctx = ngx_resolve_start(cscf->resolver, NULL);
     if (ctx == NULL) {
         ngx_mail_close_connection(c);
         return;
     }

     /* AF_INET only */

     sin = (struct sockaddr_in *) c->sockaddr;

     ctx->addr = sin->sin_addr.s_addr;
     ctx->handler = ngx_mail_smtp_resolve_addr_handler;
     ctx->data = s;
     ctx->timeout = cscf->resolver_timeout;

     if (ngx_resolve_addr(ctx) != NGX_OK) {
         ngx_mail_close_connection(c);
     }
 }


 static void
 ngx_mail_smtp_resolve_addr_handler(ngx_resolver_ctx_t *ctx)
 {
     ngx_connection_t    *c;
     ngx_mail_session_t  *s;

     s = ctx->data;
     c = s->connection;

     if (ctx->state) {
         ngx_log_error(NGX_LOG_ERR, c->log, 0,
                       "%V could not be resolved (%i: %s)",
                       &c->addr_text, ctx->state,
                       ngx_resolver_strerror(ctx->state));

         if (ctx->state == NGX_RESOLVE_NXDOMAIN) {
             s->host = smtp_unavailable;

         } else {
             s->host = smtp_tempunavail;
         }

         ngx_resolve_addr_done(ctx);

         ngx_mail_smtp_greeting(s, s->connection);

         return;
     }

     c->log->action = "in resolving client hostname";

     s->host.data = ngx_pstrdup(c->pool, &ctx->name);
     if (s->host.data == NULL) {
         ngx_resolve_addr_done(ctx);
         ngx_mail_close_connection(c);
         return;
     }

     s->host.len = ctx->name.len;

     ngx_resolve_addr_done(ctx);

     ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
                    "address resolved: %V", &s->host);

     c->read->handler = ngx_mail_smtp_resolve_name;

     ngx_post_event(c->read, &ngx_posted_events);
 }


 static void
 ngx_mail_smtp_resolve_name(ngx_event_t *rev)
 {
     ngx_connection_t          *c;
     ngx_mail_session_t        *s;
     ngx_resolver_ctx_t        *ctx;
     ngx_mail_core_srv_conf_t  *cscf;

     c = rev->data;
     s = c->data;

     cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

     ctx = ngx_resolve_start(cscf->resolver, NULL);
     if (ctx == NULL) {
         ngx_mail_close_connection(c);
         return;
     }

     ctx->name = s->host;
     ctx->type = NGX_RESOLVE_A;
     ctx->handler = ngx_mail_smtp_resolve_name_handler;
     ctx->data = s;
     ctx->timeout = cscf->resolver_timeout;

     if (ngx_resolve_name(ctx) != NGX_OK) {
         ngx_mail_close_connection(c);
     }
 }


 static void
 ngx_mail_smtp_resolve_name_handler(ngx_resolver_ctx_t *ctx)
 {
     in_addr_t            addr;
     ngx_uint_t           i;
     ngx_connection_t    *c;
     struct sockaddr_in  *sin;
     ngx_mail_session_t  *s;

     s = ctx->data;
     c = s->connection;

     if (ctx->state) {
         ngx_log_error(NGX_LOG_ERR, c->log, 0,
                       "\"%V\" could not be resolved (%i: %s)",
                       &ctx->name, ctx->state,
                       ngx_resolver_strerror(ctx->state));

         if (ctx->state == NGX_RESOLVE_NXDOMAIN) {
             s->host = smtp_unavailable;

         } else {
             s->host = smtp_tempunavail;
         }

     } else {

         /* AF_INET only */

         sin = (struct sockaddr_in *) c->sockaddr;

         for (i = 0; i < ctx->naddrs; i++) {

             addr = ctx->addrs[i];

             ngx_log_debug4(NGX_LOG_DEBUG_MAIL, c->log, 0,
                            "name was resolved to %ud.%ud.%ud.%ud",
                            (ntohl(addr) >> 24) & 0xff,
                            (ntohl(addr) >> 16) & 0xff,
                            (ntohl(addr) >> 8) & 0xff,
                            ntohl(addr) & 0xff);

             if (addr == sin->sin_addr.s_addr) {
                 goto found;
             }
         }

         s->host = smtp_unavailable;
     }

 found:

     ngx_resolve_name_done(ctx);

     ngx_mail_smtp_greeting(s, c);
 }


 static void
 ngx_mail_smtp_greeting(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     ngx_msec_t                 timeout;
     ngx_mail_core_srv_conf_t  *cscf;
     ngx_mail_smtp_srv_conf_t  *sscf;

     ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
                    "smtp greeting for \"%V\"", &s->host);

     cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);
     sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

     timeout = sscf->greeting_delay ? sscf->greeting_delay : cscf->timeout;
     ngx_add_timer(c->read, timeout);

     if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
         ngx_mail_close_connection(c);
     }

     if (sscf->greeting_delay) {
          c->read->handler = ngx_mail_smtp_invalid_pipelining;
          return;
     }

     c->read->handler = ngx_mail_smtp_init_protocol;

     s->out = sscf->greeting;

     ngx_mail_send(c->write);
 }


 static void
 ngx_mail_smtp_invalid_pipelining(ngx_event_t *rev)
 {
     ngx_connection_t          *c;
     ngx_mail_session_t        *s;
     ngx_mail_core_srv_conf_t  *cscf;
     ngx_mail_smtp_srv_conf_t  *sscf;

     c = rev->data;
     s = c->data;

     c->log->action = "in delay pipelining state";

     if (rev->timedout) {

         ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "delay greeting");

         rev->timedout = 0;

         cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

         c->read->handler = ngx_mail_smtp_init_protocol;

         ngx_add_timer(c->read, cscf->timeout);

         if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             ngx_mail_close_connection(c);
             return;
         }

         sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

         s->out = sscf->greeting;

     } else {

         ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "invalid pipelining");

         if (s->buffer == NULL) {
             if (ngx_mail_smtp_create_buffer(s, c) != NGX_OK) {
                 return;
             }
         }

         if (ngx_mail_smtp_discard_command(s, c,
                                 "client was rejected before greeting: \"%V\"")
             != NGX_OK)
         {
             return;
         }

         ngx_str_set(&s->out, smtp_invalid_pipelining);
     }

     ngx_mail_send(c->write);
 }


 void
 ngx_mail_smtp_init_protocol(ngx_event_t *rev)
 {
     ngx_connection_t    *c;
     ngx_mail_session_t  *s;

     c = rev->data;

     c->log->action = "in auth state";

     if (rev->timedout) {
         ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
         c->timedout = 1;
         ngx_mail_close_connection(c);
         return;
     }

     s = c->data;

     if (s->buffer == NULL) {
         if (ngx_mail_smtp_create_buffer(s, c) != NGX_OK) {
             return;
         }
     }

     s->mail_state = ngx_smtp_start;
     c->read->handler = ngx_mail_smtp_auth_state;

     ngx_mail_smtp_auth_state(rev);
 }


 static ngx_int_t
 ngx_mail_smtp_create_buffer(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     ngx_mail_smtp_srv_conf_t  *sscf;

     if (ngx_array_init(&s->args, c->pool, 2, sizeof(ngx_str_t)) == NGX_ERROR) {
         ngx_mail_session_internal_server_error(s);
         return NGX_ERROR;
     }

     sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

     s->buffer = ngx_create_temp_buf(c->pool, sscf->client_buffer_size);
     if (s->buffer == NULL) {
         ngx_mail_session_internal_server_error(s);
         return NGX_ERROR;
     }

     return NGX_OK;
 }


 void
 ngx_mail_smtp_auth_state(ngx_event_t *rev)
 {
     ngx_int_t            rc;
     ngx_connection_t    *c;
     ngx_mail_session_t  *s;

     c = rev->data;
     s = c->data;

     ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "smtp auth state");

     if (rev->timedout) {
         ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
         c->timedout = 1;
         ngx_mail_close_connection(c);
         return;
     }

     if (s->out.len) {
         ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "smtp send handler busy");
         s->blocked = 1;
         return;
     }

     s->blocked = 0;

     rc = ngx_mail_read_command(s, c);

     if (rc == NGX_AGAIN || rc == NGX_ERROR) {
         return;
     }

     ngx_str_set(&s->out, smtp_ok);

     if (rc == NGX_OK) {
         switch (s->mail_state) {

         case ngx_smtp_start:

             switch (s->command) {

             case NGX_SMTP_HELO:
             case NGX_SMTP_EHLO:
                 rc = ngx_mail_smtp_helo(s, c);
                 break;

             case NGX_SMTP_AUTH:
                 rc = ngx_mail_smtp_auth(s, c);
                 break;

             case NGX_SMTP_QUIT:
                 s->quit = 1;
                 ngx_str_set(&s->out, smtp_bye);
                 break;

             case NGX_SMTP_MAIL:
                 rc = ngx_mail_smtp_mail(s, c);
                 break;

             case NGX_SMTP_RCPT:
                 rc = ngx_mail_smtp_rcpt(s, c);
                 break;

             case NGX_SMTP_RSET:
                 rc = ngx_mail_smtp_rset(s, c);
                 break;

             case NGX_SMTP_NOOP:
                 break;

             case NGX_SMTP_STARTTLS:
                 rc = ngx_mail_smtp_starttls(s, c);
                 ngx_str_set(&s->out, smtp_starttls);
                 break;

             default:
                 rc = NGX_MAIL_PARSE_INVALID_COMMAND;
                 break;
             }

             break;

         case ngx_smtp_auth_login_username:
             rc = ngx_mail_auth_login_username(s, c, 0);

             ngx_str_set(&s->out, smtp_password);
             s->mail_state = ngx_smtp_auth_login_password;
             break;

         case ngx_smtp_auth_login_password:
             rc = ngx_mail_auth_login_password(s, c);
             break;

         case ngx_smtp_auth_plain:
             rc = ngx_mail_auth_plain(s, c, 0);
             break;

         case ngx_smtp_auth_cram_md5:
             rc = ngx_mail_auth_cram_md5(s, c);
             break;
         }
     }

     switch (rc) {

     case NGX_DONE:
         ngx_mail_auth(s, c);
         return;

     case NGX_ERROR:
         ngx_mail_session_internal_server_error(s);
         return;

     case NGX_MAIL_PARSE_INVALID_COMMAND:
         s->mail_state = ngx_smtp_start;
         s->state = 0;
         ngx_str_set(&s->out, smtp_invalid_command);

         /* fall through */

     case NGX_OK:
         s->args.nelts = 0;
         s->buffer->pos = s->buffer->start;
         s->buffer->last = s->buffer->start;

         if (s->state) {
             s->arg_start = s->buffer->start;
         }

         ngx_mail_send(c->write);
     }
 }


 static ngx_int_t
 ngx_mail_smtp_helo(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     ngx_str_t                 *arg;
     ngx_mail_smtp_srv_conf_t  *sscf;

     if (s->args.nelts != 1) {
         ngx_str_set(&s->out, smtp_invalid_argument);
         s->state = 0;
         return NGX_OK;
     }

     arg = s->args.elts;

     s->smtp_helo.len = arg[0].len;

     s->smtp_helo.data = ngx_pnalloc(c->pool, arg[0].len);
     if (s->smtp_helo.data == NULL) {
         return NGX_ERROR;
     }

     ngx_memcpy(s->smtp_helo.data, arg[0].data, arg[0].len);

     ngx_str_null(&s->smtp_from);
     ngx_str_null(&s->smtp_to);

     sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

     if (s->command == NGX_SMTP_HELO) {
         s->out = sscf->server_name;

     } else {
         s->esmtp = 1;

 #if (NGX_MAIL_SSL)

         if (c->ssl == NULL) {
             ngx_mail_ssl_conf_t  *sslcf;

             sslcf = ngx_mail_get_module_srv_conf(s, ngx_mail_ssl_module);

             if (sslcf->starttls == NGX_MAIL_STARTTLS_ON) {
                 s->out = sscf->starttls_capability;
                 return NGX_OK;
             }

             if (sslcf->starttls == NGX_MAIL_STARTTLS_ONLY) {
                 s->out = sscf->starttls_only_capability;
                 return NGX_OK;
             }
         }
 #endif

         s->out = sscf->capability;
     }

     return NGX_OK;
 }


 static ngx_int_t
 ngx_mail_smtp_auth(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     ngx_int_t                  rc;
     ngx_mail_core_srv_conf_t  *cscf;
     ngx_mail_smtp_srv_conf_t  *sscf;

 #if (NGX_MAIL_SSL)
     if (ngx_mail_starttls_only(s, c)) {
         return NGX_MAIL_PARSE_INVALID_COMMAND;
     }
 #endif

     if (s->args.nelts == 0) {
         ngx_str_set(&s->out, smtp_invalid_argument);
         s->state = 0;
         return NGX_OK;
     }

     rc = ngx_mail_auth_parse(s, c);

     switch (rc) {

     case NGX_MAIL_AUTH_LOGIN:

         ngx_str_set(&s->out, smtp_username);
         s->mail_state = ngx_smtp_auth_login_username;

         return NGX_OK;

     case NGX_MAIL_AUTH_LOGIN_USERNAME:

         ngx_str_set(&s->out, smtp_password);
         s->mail_state = ngx_smtp_auth_login_password;

         return ngx_mail_auth_login_username(s, c, 1);

     case NGX_MAIL_AUTH_PLAIN:

         ngx_str_set(&s->out, smtp_next);
         s->mail_state = ngx_smtp_auth_plain;

         return NGX_OK;

     case NGX_MAIL_AUTH_CRAM_MD5:

         sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

         if (!(sscf->auth_methods & NGX_MAIL_AUTH_CRAM_MD5_ENABLED)) {
             return NGX_MAIL_PARSE_INVALID_COMMAND;
         }

         if (s->salt.data == NULL) {
             cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

             if (ngx_mail_salt(s, c, cscf) != NGX_OK) {
                 return NGX_ERROR;
             }
         }

         if (ngx_mail_auth_cram_md5_salt(s, c, "334 ", 4) == NGX_OK) {
             s->mail_state = ngx_smtp_auth_cram_md5;
             return NGX_OK;
         }

         return NGX_ERROR;
     }

     return rc;
 }


 static ngx_int_t
 ngx_mail_smtp_mail(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     u_char                     ch;
     ngx_str_t                  l;
     ngx_uint_t                 i;
     ngx_mail_smtp_srv_conf_t  *sscf;

     sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

     if (!(sscf->auth_methods & NGX_MAIL_AUTH_NONE_ENABLED)) {
         ngx_mail_smtp_log_rejected_command(s, c, "client was rejected: \"%V\"");
         ngx_str_set(&s->out, smtp_auth_required);
         return NGX_OK;
     }

     /* auth none */

     if (s->smtp_from.len) {
         ngx_str_set(&s->out, smtp_bad_sequence);
         return NGX_OK;
     }

     l.len = s->buffer->last - s->buffer->start;
     l.data = s->buffer->start;

     for (i = 0; i < l.len; i++) {
         ch = l.data[i];

         if (ch != CR && ch != LF) {
             continue;
         }

         l.data[i] = ' ';
     }

     while (i) {
         if (l.data[i - 1] != ' ') {
             break;
         }

         i--;
     }

     l.len = i;

     s->smtp_from.len = l.len;

     s->smtp_from.data = ngx_pnalloc(c->pool, l.len);
     if (s->smtp_from.data == NULL) {
         return NGX_ERROR;
     }

     ngx_memcpy(s->smtp_from.data, l.data, l.len);

     ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
                    "smtp mail from:\"%V\"", &s->smtp_from);

     ngx_str_set(&s->out, smtp_ok);

     return NGX_OK;
 }


 static ngx_int_t
 ngx_mail_smtp_rcpt(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     u_char      ch;
     ngx_str_t   l;
     ngx_uint_t  i;

     if (s->smtp_from.len == 0) {
         ngx_str_set(&s->out, smtp_bad_sequence);
         return NGX_OK;
     }

     l.len = s->buffer->last - s->buffer->start;
     l.data = s->buffer->start;

     for (i = 0; i < l.len; i++) {
         ch = l.data[i];

         if (ch != CR && ch != LF) {
             continue;
         }

         l.data[i] = ' ';
     }

     while (i) {
         if (l.data[i - 1] != ' ') {
             break;
         }

         i--;
     }

     l.len = i;

     s->smtp_to.len = l.len;

     s->smtp_to.data = ngx_pnalloc(c->pool, l.len);
     if (s->smtp_to.data == NULL) {
         return NGX_ERROR;
     }

     ngx_memcpy(s->smtp_to.data, l.data, l.len);

     ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
                    "smtp rcpt to:\"%V\"", &s->smtp_to);

     s->auth_method = NGX_MAIL_AUTH_NONE;

     return NGX_DONE;
 }


 static ngx_int_t
 ngx_mail_smtp_rset(ngx_mail_session_t *s, ngx_connection_t *c)
 {
     ngx_str_null(&s->smtp_from);
     ngx_str_null(&s->smtp_to);
     ngx_str_set(&s->out, smtp_ok);

     return NGX_OK;
 }


 static ngx_int_t
 ngx_mail_smtp_starttls(ngx_mail_session_t *s, ngx_connection_t *c)
 {
 #if (NGX_MAIL_SSL)
     ngx_mail_ssl_conf_t  *sslcf;

     if (c->ssl == NULL) {
         sslcf = ngx_mail_get_module_srv_conf(s, ngx_mail_ssl_module);
         if (sslcf->starttls) {

             /*
              * RFC3207 requires us to discard any knowledge
              * obtained from client before STARTTLS.
              */

             ngx_str_null(&s->smtp_helo);
             ngx_str_null(&s->smtp_from);
             ngx_str_null(&s->smtp_to);

             c->read->handler = ngx_mail_starttls_handler;
             return NGX_OK;
         }
     }

 #endif

     return NGX_MAIL_PARSE_INVALID_COMMAND;
 }


 static ngx_int_t
 ngx_mail_smtp_discard_command(ngx_mail_session_t *s, ngx_connection_t *c,
     char *err)
 {
     ssize_t    n;

     n = c->recv(c, s->buffer->last, s->buffer->end - s->buffer->last);

     if (n == NGX_ERROR || n == 0) {
         ngx_mail_close_connection(c);
         return NGX_ERROR;
     }

     if (n > 0) {
         s->buffer->last += n;
     }

     if (n == NGX_AGAIN) {
         if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
             ngx_mail_session_internal_server_error(s);
             return NGX_ERROR;
         }

         return NGX_AGAIN;
     }

     ngx_mail_smtp_log_rejected_command(s, c, err);

     s->buffer->pos = s->buffer->start;
     s->buffer->last = s->buffer->start;

     return NGX_OK;
 }


 static void
 ngx_mail_smtp_log_rejected_command(ngx_mail_session_t *s, ngx_connection_t *c,
     char *err)
 {
     u_char      ch;
     ngx_str_t   cmd;
     ngx_uint_t  i;

     if (c->log->log_level < NGX_LOG_INFO) {
         return;
     }

     cmd.len = s->buffer->last - s->buffer->start;
     cmd.data = s->buffer->start;

     for (i = 0; i < cmd.len; i++) {
         ch = cmd.data[i];

         if (ch != CR && ch != LF) {
             continue;
         }

         cmd.data[i] = '_';
     }

     cmd.len = i;

     ngx_log_error(NGX_LOG_INFO, c->log, 0, err, &cmd);
 }

	/*
	* 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_resolve_addr_handler(ngx_resolver_ctx_t *ctx);
	static void ngx_mail_smtp_resolve_name(ngx_event_t *rev);
	static void ngx_mail_smtp_resolve_name_handler(ngx_resolver_ctx_t *ctx);
	static void ngx_mail_smtp_greeting(ngx_mail_session_t s, ngx_connection_t c);
	static void ngx_mail_smtp_invalid_pipelining(ngx_event_t *rev);
	static ngx_int_t ngx_mail_smtp_create_buffer(ngx_mail_session_t *s,
	ngx_connection_t *c);

	static ngx_int_t ngx_mail_smtp_helo(ngx_mail_session_t s, ngx_connection_t c);
	static ngx_int_t ngx_mail_smtp_auth(ngx_mail_session_t s, ngx_connection_t c);
	static ngx_int_t ngx_mail_smtp_mail(ngx_mail_session_t s, ngx_connection_t c);
	static ngx_int_t ngx_mail_smtp_starttls(ngx_mail_session_t *s,
	ngx_connection_t *c);
	static ngx_int_t ngx_mail_smtp_rset(ngx_mail_session_t s, ngx_connection_t c);
	static ngx_int_t ngx_mail_smtp_rcpt(ngx_mail_session_t s, ngx_connection_t c);

	static ngx_int_t ngx_mail_smtp_discard_command(ngx_mail_session_t *s,
	ngx_connection_t c, char err);
	static void ngx_mail_smtp_log_rejected_command(ngx_mail_session_t *s,
	ngx_connection_t c, char err);


	static u_char smtp_ok[] = "250 2.0.0 OK" CRLF;
	static u_char smtp_bye[] = "221 2.0.0 Bye" CRLF;
	static u_char smtp_starttls[] = "220 2.0.0 Start TLS" CRLF;
	static u_char smtp_next[] = "334 " CRLF;
	static u_char smtp_username[] = "334 VXNlcm5hbWU6" CRLF;
	static u_char smtp_password[] = "334 UGFzc3dvcmQ6" CRLF;
	static u_char smtp_invalid_command[] = "500 5.5.1 Invalid command" CRLF;
	static u_char smtp_invalid_pipelining[] =
	"503 5.5.0 Improper use of SMTP command pipelining" CRLF;
	static u_char smtp_invalid_argument[] = "501 5.5.4 Invalid argument" CRLF;
	static u_char smtp_auth_required[] = "530 5.7.1 Authentication required" CRLF;
	static u_char smtp_bad_sequence[] = "503 5.5.1 Bad sequence of commands" CRLF;


	static ngx_str_t smtp_unavailable = ngx_string("[UNAVAILABLE]");
	static ngx_str_t smtp_tempunavail = ngx_string("[TEMPUNAVAIL]");


	void
	ngx_mail_smtp_init_session(ngx_mail_session_t s, ngx_connection_t c)
	{
	struct sockaddr_in *sin;
	ngx_resolver_ctx_t *ctx;
	ngx_mail_core_srv_conf_t *cscf;

	cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

	if (cscf->resolver == NULL) {
	s->host = smtp_unavailable;
	ngx_mail_smtp_greeting(s, c);
	return;
	}

	if (c->sockaddr->sa_family != AF_INET) {
	s->host = smtp_tempunavail;
	ngx_mail_smtp_greeting(s, c);
	return;
	}

	c->log->action = "in resolving client address";

	ctx = ngx_resolve_start(cscf->resolver, NULL);
	if (ctx == NULL) {
	ngx_mail_close_connection(c);
	return;
	}

	/* AF_INET only */

	sin = (struct sockaddr_in *) c->sockaddr;

	ctx->addr = sin->sin_addr.s_addr;
	ctx->handler = ngx_mail_smtp_resolve_addr_handler;
	ctx->data = s;
	ctx->timeout = cscf->resolver_timeout;

	if (ngx_resolve_addr(ctx) != NGX_OK) {
	ngx_mail_close_connection(c);
	}
	}


	static void
	ngx_mail_smtp_resolve_addr_handler(ngx_resolver_ctx_t *ctx)
	{
	ngx_connection_t *c;
	ngx_mail_session_t *s;

	s = ctx->data;
	c = s->connection;

	if (ctx->state) {
	ngx_log_error(NGX_LOG_ERR, c->log, 0,
	"%V could not be resolved (%i: %s)",
	&c->addr_text, ctx->state,
	ngx_resolver_strerror(ctx->state));

	if (ctx->state == NGX_RESOLVE_NXDOMAIN) {
	s->host = smtp_unavailable;

	} else {
	s->host = smtp_tempunavail;
	}

	ngx_resolve_addr_done(ctx);

	ngx_mail_smtp_greeting(s, s->connection);

	return;
	}

	c->log->action = "in resolving client hostname";

	s->host.data = ngx_pstrdup(c->pool, &ctx->name);
	if (s->host.data == NULL) {
	ngx_resolve_addr_done(ctx);
	ngx_mail_close_connection(c);
	return;
	}

	s->host.len = ctx->name.len;

	ngx_resolve_addr_done(ctx);

	ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
	"address resolved: %V", &s->host);

	c->read->handler = ngx_mail_smtp_resolve_name;

	ngx_post_event(c->read, &ngx_posted_events);
	}


	static void
	ngx_mail_smtp_resolve_name(ngx_event_t *rev)
	{
	ngx_connection_t *c;
	ngx_mail_session_t *s;
	ngx_resolver_ctx_t *ctx;
	ngx_mail_core_srv_conf_t *cscf;

	c = rev->data;
	s = c->data;

	cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

	ctx = ngx_resolve_start(cscf->resolver, NULL);
	if (ctx == NULL) {
	ngx_mail_close_connection(c);
	return;
	}

	ctx->name = s->host;
	ctx->type = NGX_RESOLVE_A;
	ctx->handler = ngx_mail_smtp_resolve_name_handler;
	ctx->data = s;
	ctx->timeout = cscf->resolver_timeout;

	if (ngx_resolve_name(ctx) != NGX_OK) {
	ngx_mail_close_connection(c);
	}
	}


	static void
	ngx_mail_smtp_resolve_name_handler(ngx_resolver_ctx_t *ctx)
	{
	in_addr_t addr;
	ngx_uint_t i;
	ngx_connection_t *c;
	struct sockaddr_in *sin;
	ngx_mail_session_t *s;

	s = ctx->data;
	c = s->connection;

	if (ctx->state) {
	ngx_log_error(NGX_LOG_ERR, c->log, 0,
	"\"%V\" could not be resolved (%i: %s)",
	&ctx->name, ctx->state,
	ngx_resolver_strerror(ctx->state));

	if (ctx->state == NGX_RESOLVE_NXDOMAIN) {
	s->host = smtp_unavailable;

	} else {
	s->host = smtp_tempunavail;
	}

	} else {

	/* AF_INET only */

	sin = (struct sockaddr_in *) c->sockaddr;

	for (i = 0; i < ctx->naddrs; i++) {

	addr = ctx->addrs[i];

	ngx_log_debug4(NGX_LOG_DEBUG_MAIL, c->log, 0,
	"name was resolved to %ud.%ud.%ud.%ud",
	(ntohl(addr) >> 24) & 0xff,
	(ntohl(addr) >> 16) & 0xff,
	(ntohl(addr) >> 8) & 0xff,
	ntohl(addr) & 0xff);

	if (addr == sin->sin_addr.s_addr) {
	goto found;
	}
	}

	s->host = smtp_unavailable;
	}

	found:

	ngx_resolve_name_done(ctx);

	ngx_mail_smtp_greeting(s, c);
	}


	static void
	ngx_mail_smtp_greeting(ngx_mail_session_t s, ngx_connection_t c)
	{
	ngx_msec_t timeout;
	ngx_mail_core_srv_conf_t *cscf;
	ngx_mail_smtp_srv_conf_t *sscf;

	ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
	"smtp greeting for \"%V\"", &s->host);

	cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);
	sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

	timeout = sscf->greeting_delay ? sscf->greeting_delay : cscf->timeout;
	ngx_add_timer(c->read, timeout);

	if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
	ngx_mail_close_connection(c);
	}

	if (sscf->greeting_delay) {
	c->read->handler = ngx_mail_smtp_invalid_pipelining;
	return;
	}

	c->read->handler = ngx_mail_smtp_init_protocol;

	s->out = sscf->greeting;

	ngx_mail_send(c->write);
	}


	static void
	ngx_mail_smtp_invalid_pipelining(ngx_event_t *rev)
	{
	ngx_connection_t *c;
	ngx_mail_session_t *s;
	ngx_mail_core_srv_conf_t *cscf;
	ngx_mail_smtp_srv_conf_t *sscf;

	c = rev->data;
	s = c->data;

	c->log->action = "in delay pipelining state";

	if (rev->timedout) {

	ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "delay greeting");

	rev->timedout = 0;

	cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

	c->read->handler = ngx_mail_smtp_init_protocol;

	ngx_add_timer(c->read, cscf->timeout);

	if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
	ngx_mail_close_connection(c);
	return;
	}

	sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

	s->out = sscf->greeting;

	} else {

	ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "invalid pipelining");

	if (s->buffer == NULL) {
	if (ngx_mail_smtp_create_buffer(s, c) != NGX_OK) {
	return;
	}
	}

	if (ngx_mail_smtp_discard_command(s, c,
	"client was rejected before greeting: \"%V\"")
	!= NGX_OK)
	{
	return;
	}

	ngx_str_set(&s->out, smtp_invalid_pipelining);
	}

	ngx_mail_send(c->write);
	}


	void
	ngx_mail_smtp_init_protocol(ngx_event_t *rev)
	{
	ngx_connection_t *c;
	ngx_mail_session_t *s;

	c = rev->data;

	c->log->action = "in auth state";

	if (rev->timedout) {
	ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
	c->timedout = 1;
	ngx_mail_close_connection(c);
	return;
	}

	s = c->data;

	if (s->buffer == NULL) {
	if (ngx_mail_smtp_create_buffer(s, c) != NGX_OK) {
	return;
	}
	}

	s->mail_state = ngx_smtp_start;
	c->read->handler = ngx_mail_smtp_auth_state;

	ngx_mail_smtp_auth_state(rev);
	}


	static ngx_int_t
	ngx_mail_smtp_create_buffer(ngx_mail_session_t s, ngx_connection_t c)
	{
	ngx_mail_smtp_srv_conf_t *sscf;

	if (ngx_array_init(&s->args, c->pool, 2, sizeof(ngx_str_t)) == NGX_ERROR) {
	ngx_mail_session_internal_server_error(s);
	return NGX_ERROR;
	}

	sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

	s->buffer = ngx_create_temp_buf(c->pool, sscf->client_buffer_size);
	if (s->buffer == NULL) {
	ngx_mail_session_internal_server_error(s);
	return NGX_ERROR;
	}

	return NGX_OK;
	}


	void
	ngx_mail_smtp_auth_state(ngx_event_t *rev)
	{
	ngx_int_t rc;
	ngx_connection_t *c;
	ngx_mail_session_t *s;

	c = rev->data;
	s = c->data;

	ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "smtp auth state");

	if (rev->timedout) {
	ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
	c->timedout = 1;
	ngx_mail_close_connection(c);
	return;
	}

	if (s->out.len) {
	ngx_log_debug0(NGX_LOG_DEBUG_MAIL, c->log, 0, "smtp send handler busy");
	s->blocked = 1;
	return;
	}

	s->blocked = 0;

	rc = ngx_mail_read_command(s, c);

	if (rc == NGX_AGAIN \|\| rc == NGX_ERROR) {
	return;
	}

	ngx_str_set(&s->out, smtp_ok);

	if (rc == NGX_OK) {
	switch (s->mail_state) {

	case ngx_smtp_start:

	switch (s->command) {

	case NGX_SMTP_HELO:
	case NGX_SMTP_EHLO:
	rc = ngx_mail_smtp_helo(s, c);
	break;

	case NGX_SMTP_AUTH:
	rc = ngx_mail_smtp_auth(s, c);
	break;

	case NGX_SMTP_QUIT:
	s->quit = 1;
	ngx_str_set(&s->out, smtp_bye);
	break;

	case NGX_SMTP_MAIL:
	rc = ngx_mail_smtp_mail(s, c);
	break;

	case NGX_SMTP_RCPT:
	rc = ngx_mail_smtp_rcpt(s, c);
	break;

	case NGX_SMTP_RSET:
	rc = ngx_mail_smtp_rset(s, c);
	break;

	case NGX_SMTP_NOOP:
	break;

	case NGX_SMTP_STARTTLS:
	rc = ngx_mail_smtp_starttls(s, c);
	ngx_str_set(&s->out, smtp_starttls);
	break;

	default:
	rc = NGX_MAIL_PARSE_INVALID_COMMAND;
	break;
	}

	break;

	case ngx_smtp_auth_login_username:
	rc = ngx_mail_auth_login_username(s, c, 0);

	ngx_str_set(&s->out, smtp_password);
	s->mail_state = ngx_smtp_auth_login_password;
	break;

	case ngx_smtp_auth_login_password:
	rc = ngx_mail_auth_login_password(s, c);
	break;

	case ngx_smtp_auth_plain:
	rc = ngx_mail_auth_plain(s, c, 0);
	break;

	case ngx_smtp_auth_cram_md5:
	rc = ngx_mail_auth_cram_md5(s, c);
	break;
	}
	}

	switch (rc) {

	case NGX_DONE:
	ngx_mail_auth(s, c);
	return;

	case NGX_ERROR:
	ngx_mail_session_internal_server_error(s);
	return;

	case NGX_MAIL_PARSE_INVALID_COMMAND:
	s->mail_state = ngx_smtp_start;
	s->state = 0;
	ngx_str_set(&s->out, smtp_invalid_command);

	/* fall through */

	case NGX_OK:
	s->args.nelts = 0;
	s->buffer->pos = s->buffer->start;
	s->buffer->last = s->buffer->start;

	if (s->state) {
	s->arg_start = s->buffer->start;
	}

	ngx_mail_send(c->write);
	}
	}


	static ngx_int_t
	ngx_mail_smtp_helo(ngx_mail_session_t s, ngx_connection_t c)
	{
	ngx_str_t *arg;
	ngx_mail_smtp_srv_conf_t *sscf;

	if (s->args.nelts != 1) {
	ngx_str_set(&s->out, smtp_invalid_argument);
	s->state = 0;
	return NGX_OK;
	}

	arg = s->args.elts;

	s->smtp_helo.len = arg[0].len;

	s->smtp_helo.data = ngx_pnalloc(c->pool, arg[0].len);
	if (s->smtp_helo.data == NULL) {
	return NGX_ERROR;
	}

	ngx_memcpy(s->smtp_helo.data, arg[0].data, arg[0].len);

	ngx_str_null(&s->smtp_from);
	ngx_str_null(&s->smtp_to);

	sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

	if (s->command == NGX_SMTP_HELO) {
	s->out = sscf->server_name;

	} else {
	s->esmtp = 1;

	#if (NGX_MAIL_SSL)

	if (c->ssl == NULL) {
	ngx_mail_ssl_conf_t *sslcf;

	sslcf = ngx_mail_get_module_srv_conf(s, ngx_mail_ssl_module);

	if (sslcf->starttls == NGX_MAIL_STARTTLS_ON) {
	s->out = sscf->starttls_capability;
	return NGX_OK;
	}

	if (sslcf->starttls == NGX_MAIL_STARTTLS_ONLY) {
	s->out = sscf->starttls_only_capability;
	return NGX_OK;
	}
	}
	#endif

	s->out = sscf->capability;
	}

	return NGX_OK;
	}


	static ngx_int_t
	ngx_mail_smtp_auth(ngx_mail_session_t s, ngx_connection_t c)
	{
	ngx_int_t rc;
	ngx_mail_core_srv_conf_t *cscf;
	ngx_mail_smtp_srv_conf_t *sscf;

	#if (NGX_MAIL_SSL)
	if (ngx_mail_starttls_only(s, c)) {
	return NGX_MAIL_PARSE_INVALID_COMMAND;
	}
	#endif

	if (s->args.nelts == 0) {
	ngx_str_set(&s->out, smtp_invalid_argument);
	s->state = 0;
	return NGX_OK;
	}

	rc = ngx_mail_auth_parse(s, c);

	switch (rc) {

	case NGX_MAIL_AUTH_LOGIN:

	ngx_str_set(&s->out, smtp_username);
	s->mail_state = ngx_smtp_auth_login_username;

	return NGX_OK;

	case NGX_MAIL_AUTH_LOGIN_USERNAME:

	ngx_str_set(&s->out, smtp_password);
	s->mail_state = ngx_smtp_auth_login_password;

	return ngx_mail_auth_login_username(s, c, 1);

	case NGX_MAIL_AUTH_PLAIN:

	ngx_str_set(&s->out, smtp_next);
	s->mail_state = ngx_smtp_auth_plain;

	return NGX_OK;

	case NGX_MAIL_AUTH_CRAM_MD5:

	sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

	if (!(sscf->auth_methods & NGX_MAIL_AUTH_CRAM_MD5_ENABLED)) {
	return NGX_MAIL_PARSE_INVALID_COMMAND;
	}

	if (s->salt.data == NULL) {
	cscf = ngx_mail_get_module_srv_conf(s, ngx_mail_core_module);

	if (ngx_mail_salt(s, c, cscf) != NGX_OK) {
	return NGX_ERROR;
	}
	}

	if (ngx_mail_auth_cram_md5_salt(s, c, "334 ", 4) == NGX_OK) {
	s->mail_state = ngx_smtp_auth_cram_md5;
	return NGX_OK;
	}

	return NGX_ERROR;
	}

	return rc;
	}


	static ngx_int_t
	ngx_mail_smtp_mail(ngx_mail_session_t s, ngx_connection_t c)
	{
	u_char ch;
	ngx_str_t l;
	ngx_uint_t i;
	ngx_mail_smtp_srv_conf_t *sscf;

	sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);

	if (!(sscf->auth_methods & NGX_MAIL_AUTH_NONE_ENABLED)) {
	ngx_mail_smtp_log_rejected_command(s, c, "client was rejected: \"%V\"");
	ngx_str_set(&s->out, smtp_auth_required);
	return NGX_OK;
	}

	/* auth none */

	if (s->smtp_from.len) {
	ngx_str_set(&s->out, smtp_bad_sequence);
	return NGX_OK;
	}

	l.len = s->buffer->last - s->buffer->start;
	l.data = s->buffer->start;

	for (i = 0; i < l.len; i++) {
	ch = l.data[i];

	if (ch != CR && ch != LF) {
	continue;
	}

	l.data[i] = ' ';
	}

	while (i) {
	if (l.data[i - 1] != ' ') {
	break;
	}

	i--;
	}

	l.len = i;

	s->smtp_from.len = l.len;

	s->smtp_from.data = ngx_pnalloc(c->pool, l.len);
	if (s->smtp_from.data == NULL) {
	return NGX_ERROR;
	}

	ngx_memcpy(s->smtp_from.data, l.data, l.len);

	ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
	"smtp mail from:\"%V\"", &s->smtp_from);

	ngx_str_set(&s->out, smtp_ok);

	return NGX_OK;
	}


	static ngx_int_t
	ngx_mail_smtp_rcpt(ngx_mail_session_t s, ngx_connection_t c)
	{
	u_char ch;
	ngx_str_t l;
	ngx_uint_t i;

	if (s->smtp_from.len == 0) {
	ngx_str_set(&s->out, smtp_bad_sequence);
	return NGX_OK;
	}

	l.len = s->buffer->last - s->buffer->start;
	l.data = s->buffer->start;

	for (i = 0; i < l.len; i++) {
	ch = l.data[i];

	if (ch != CR && ch != LF) {
	continue;
	}

	l.data[i] = ' ';
	}

	while (i) {
	if (l.data[i - 1] != ' ') {
	break;
	}

	i--;
	}

	l.len = i;

	s->smtp_to.len = l.len;

	s->smtp_to.data = ngx_pnalloc(c->pool, l.len);
	if (s->smtp_to.data == NULL) {
	return NGX_ERROR;
	}

	ngx_memcpy(s->smtp_to.data, l.data, l.len);

	ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
	"smtp rcpt to:\"%V\"", &s->smtp_to);

	s->auth_method = NGX_MAIL_AUTH_NONE;

	return NGX_DONE;
	}


	static ngx_int_t
	ngx_mail_smtp_rset(ngx_mail_session_t s, ngx_connection_t c)
	{
	ngx_str_null(&s->smtp_from);
	ngx_str_null(&s->smtp_to);
	ngx_str_set(&s->out, smtp_ok);

	return NGX_OK;
	}


	static ngx_int_t
	ngx_mail_smtp_starttls(ngx_mail_session_t s, ngx_connection_t c)
	{
	#if (NGX_MAIL_SSL)
	ngx_mail_ssl_conf_t *sslcf;

	if (c->ssl == NULL) {
	sslcf = ngx_mail_get_module_srv_conf(s, ngx_mail_ssl_module);
	if (sslcf->starttls) {

	/*
	* RFC3207 requires us to discard any knowledge
	* obtained from client before STARTTLS.
	*/

	ngx_str_null(&s->smtp_helo);
	ngx_str_null(&s->smtp_from);
	ngx_str_null(&s->smtp_to);

	c->read->handler = ngx_mail_starttls_handler;
	return NGX_OK;
	}
	}

	#endif

	return NGX_MAIL_PARSE_INVALID_COMMAND;
	}


	static ngx_int_t
	ngx_mail_smtp_discard_command(ngx_mail_session_t s, ngx_connection_t c,
	char *err)
	{
	ssize_t n;

	n = c->recv(c, s->buffer->last, s->buffer->end - s->buffer->last);

	if (n == NGX_ERROR \|\| n == 0) {
	ngx_mail_close_connection(c);
	return NGX_ERROR;
	}

	if (n > 0) {
	s->buffer->last += n;
	}

	if (n == NGX_AGAIN) {
	if (ngx_handle_read_event(c->read, 0) != NGX_OK) {
	ngx_mail_session_internal_server_error(s);
	return NGX_ERROR;
	}

	return NGX_AGAIN;
	}

	ngx_mail_smtp_log_rejected_command(s, c, err);

	s->buffer->pos = s->buffer->start;
	s->buffer->last = s->buffer->start;

	return NGX_OK;
	}


	static void
	ngx_mail_smtp_log_rejected_command(ngx_mail_session_t s, ngx_connection_t c,
	char *err)
	{
	u_char ch;
	ngx_str_t cmd;
	ngx_uint_t i;

	if (c->log->log_level < NGX_LOG_INFO) {
	return;
	}

	cmd.len = s->buffer->last - s->buffer->start;
	cmd.data = s->buffer->start;

	for (i = 0; i < cmd.len; i++) {
	ch = cmd.data[i];

	if (ch != CR && ch != LF) {
	continue;
	}

	cmd.data[i] = '_';
	}

	cmd.len = i;

	ngx_log_error(NGX_LOG_INFO, c->log, 0, err, &cmd);
	}