Initial commit

src/mail/ngx_mail_smtp_handler.c

@@ -0,0 +1,872 @@
+
+/*
+ * 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)
+{
+    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 (NGX_HAVE_UNIX_DOMAIN)
+    if (c->sockaddr->sa_family == AF_UNIX) {
+        s->host = smtp_tempunavail;
+        ngx_mail_smtp_greeting(s, c);
+        return;
+    }
+#endif
+
+    c->log->action = "in resolving client address";
+
+    ctx = ngx_resolve_start(cscf->resolver, NULL);
+    if (ctx == NULL) {
+        ngx_mail_close_connection(c);
+        return;
+    }
+
+    ctx->addr.sockaddr = c->sockaddr;
+    ctx->addr.socklen = c->socklen;
+    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->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)
+{
+    ngx_uint_t           i;
+    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)",
+                      &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 {
+
+#if (NGX_DEBUG)
+        {
+        u_char     text[NGX_SOCKADDR_STRLEN];
+        ngx_str_t  addr;
+
+        addr.data = text;
+
+        for (i = 0; i < ctx->naddrs; i++) {
+            addr.len = ngx_sock_ntop(ctx->addrs[i].sockaddr,
+                                     ctx->addrs[i].socklen,
+                                     text, NGX_SOCKADDR_STRLEN, 0);
+
+            ngx_log_debug1(NGX_LOG_DEBUG_MAIL, c->log, 0,
+                           "name was resolved to %V", &addr);
+        }
+        }
+#endif
+
+        for (i = 0; i < ctx->naddrs; i++) {
+            if (ngx_cmp_sockaddr(ctx->addrs[i].sockaddr, ctx->addrs[i].socklen,
+                                 c->sockaddr, c->socklen, 0)
+                == NGX_OK)
+            {
+                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);
+        s->quit = 1;
+    }
+
+    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;
+
+        case ngx_smtp_auth_external:
+            rc = ngx_mail_auth_external(s, c, 0);
+            break;
+        }
+    }
+
+    if (s->buffer->pos < s->buffer->last) {
+        s->blocked = 1;
+    }
+
+    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;
+
+        if (s->buffer->pos == s->buffer->last) {
+            s->buffer->pos = s->buffer->start;
+            s->buffer->last = s->buffer->start;
+        }
+
+        if (s->state) {
+            s->arg_start = s->buffer->pos;
+        }
+
+        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;
+    }
+
+    sscf = ngx_mail_get_module_srv_conf(s, ngx_mail_smtp_module);
+
+    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:
+
+        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;
+
+    case NGX_MAIL_AUTH_EXTERNAL:
+
+        if (!(sscf->auth_methods & NGX_MAIL_AUTH_EXTERNAL_ENABLED)) {
+            return NGX_MAIL_PARSE_INVALID_COMMAND;
+        }
+
+        ngx_str_set(&s->out, smtp_username);
+        s->mail_state = ngx_smtp_auth_external;
+
+        return NGX_OK;
+    }
+
+    return rc;
+}
+
+
+static ngx_int_t
+ngx_mail_smtp_mail(ngx_mail_session_t *s, ngx_connection_t *c)
+{
+    ngx_str_t                 *arg, cmd;
+    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;
+    }
+
+    if (s->args.nelts == 0) {
+        ngx_str_set(&s->out, smtp_invalid_argument);
+        return NGX_OK;
+    }
+
+    arg = s->args.elts;
+    arg += s->args.nelts - 1;
+
+    cmd.len = arg->data + arg->len - s->cmd.data;
+    cmd.data = s->cmd.data;
+
+    s->smtp_from.len = cmd.len;
+
+    s->smtp_from.data = ngx_pnalloc(c->pool, cmd.len);
+    if (s->smtp_from.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    ngx_memcpy(s->smtp_from.data, cmd.data, cmd.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)
+{
+    ngx_str_t  *arg, cmd;
+
+    if (s->smtp_from.len == 0) {
+        ngx_str_set(&s->out, smtp_bad_sequence);
+        return NGX_OK;
+    }
+
+    if (s->args.nelts == 0) {
+        ngx_str_set(&s->out, smtp_invalid_argument);
+        return NGX_OK;
+    }
+
+    arg = s->args.elts;
+    arg += s->args.nelts - 1;
+
+    cmd.len = arg->data + arg->len - s->cmd.data;
+    cmd.data = s->cmd.data;
+
+    s->smtp_to.len = cmd.len;
+
+    s->smtp_to.data = ngx_pnalloc(c->pool, cmd.len);
+    if (s->smtp_to.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    ngx_memcpy(s->smtp_to.data, cmd.data, cmd.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);
+
+            s->buffer->pos = s->buffer->start;
+            s->buffer->last = s->buffer->start;
+
+            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);
+}