1 /*************************************************
2 * Exim - an Internet mail transport agent *
3 *************************************************/
4 /* Experimental DMARC support.
5 Copyright (c) Todd Lyons <tlyons@exim.org> 2012, 2013
8 /* Portions Copyright (c) 2012, 2013, The Trusted Domain Project;
9 All rights reserved, licensed for use per LICENSE.opendmarc. */
11 /* Code for calling dmarc checks via libopendmarc. Called from acl.c. */
14 #ifdef EXPERIMENTAL_DMARC
15 #if !defined EXPERIMENTAL_SPF
16 #error SPF must also be enabled for DMARC
17 #elif defined DISABLE_DKIM
18 #error DKIM must also be enabled for DMARC
21 #include "functions.h"
23 #include "pdkim/pdkim.h"
25 OPENDMARC_LIB_T dmarc_ctx
;
26 DMARC_POLICY_T
*dmarc_pctx
= NULL
;
27 OPENDMARC_STATUS_T libdm_status
, action
, dmarc_policy
;
28 OPENDMARC_STATUS_T da
, sa
, action
;
29 BOOL dmarc_abort
= FALSE
;
30 uschar
*dmarc_pass_fail
= US
"skipped";
31 extern pdkim_signature
*dkim_signatures
;
32 header_line
*from_header
= NULL
;
33 extern SPF_response_t
*spf_response
;
34 int dmarc_spf_result
= 0;
35 uschar
*spf_sender_domain
= NULL
;
36 uschar
*spf_human_readable
= NULL
;
37 u_char
*header_from_sender
= NULL
;
38 int history_file_status
= DMARC_HIST_OK
;
39 uschar
*dkim_history_buffer
= NULL
;
41 /* Accept an error_block struct, initialize if empty, parse to the
42 * end, and append the two strings passed to it. Used for adding
43 * variable amounts of value:pair data to the forensic emails. */
46 add_to_eblock(error_block
*eblock
, uschar
*t1
, uschar
*t2
)
48 error_block
*eb
= malloc(sizeof(error_block
));
53 /* Find the end of the eblock struct and point it at eb */
54 error_block
*tmp
= eblock
;
55 while(tmp
->next
!= NULL
)
65 /* dmarc_init sets up a context that can be re-used for several
66 messages on the same SMTP connection (that come from the
67 same host with the same HELO string) */
71 int *netmask
= NULL
; /* Ignored */
73 char *tld_file
= (dmarc_tld_file
== NULL
) ?
74 "/etc/exim/opendmarc.tlds" :
75 (char *)dmarc_tld_file
;
77 /* Set some sane defaults. Also clears previous results when
78 * multiple messages in one connection. */
80 dmarc_status
= US
"none";
82 dmarc_pass_fail
= US
"skipped";
83 dmarc_used_domain
= US
"";
84 header_from_sender
= NULL
;
85 spf_sender_domain
= NULL
;
86 spf_human_readable
= NULL
;
88 /* ACLs have "control=dmarc_disable_verify" */
89 if (dmarc_disable_verify
== TRUE
)
92 (void) memset(&dmarc_ctx
, '\0', sizeof dmarc_ctx
);
93 dmarc_ctx
.nscount
= 0;
94 libdm_status
= opendmarc_policy_library_init(&dmarc_ctx
);
95 if (libdm_status
!= DMARC_PARSE_OKAY
)
97 log_write(0, LOG_MAIN
|LOG_PANIC
, "DMARC failure to init library: %s",
98 opendmarc_policy_status_to_str(libdm_status
));
101 if (opendmarc_tld_read_file(tld_file
, NULL
, NULL
, NULL
))
103 log_write(0, LOG_MAIN
|LOG_PANIC
, "DMARC failure to load tld list %s: %d",
107 if (sender_host_address
== NULL
)
109 /* This catches locally originated email and startup errors above. */
110 if ( dmarc_abort
== FALSE
)
112 is_ipv6
= string_is_ip_address(sender_host_address
, netmask
);
113 is_ipv6
= (is_ipv6
== 6) ? TRUE
:
114 (is_ipv6
== 4) ? FALSE
: FALSE
;
115 dmarc_pctx
= opendmarc_policy_connect_init(sender_host_address
, is_ipv6
);
116 if (dmarc_pctx
== NULL
)
118 log_write(0, LOG_MAIN
|LOG_PANIC
, "DMARC failure creating policy context: ip=%s",
119 sender_host_address
);
128 /* dmarc_store_data stores the header data so that subsequent
129 * dmarc_process can access the data */
131 int dmarc_store_data(header_line
*hdr
) {
132 /* No debug output because would change every test debug output */
133 if (dmarc_disable_verify
!= TRUE
)
139 /* dmarc_process adds the envelope sender address to the existing
140 context (if any), retrieves the result, sets up expansion
141 strings and evaluates the condition outcome. */
143 int dmarc_process() {
144 int sr
, origin
; /* used in SPF section */
145 pdkim_signature
*sig
= NULL
;
146 BOOL has_dmarc_record
= TRUE
;
147 u_char
**ruf
; /* forensic report addressees, if called for */
149 /* ACLs have "control=dmarc_disable_verify" */
150 if (dmarc_disable_verify
== TRUE
)
152 dmarc_ar_header
= dmarc_auth_results_header(from_header
, NULL
);
156 /* Store the header From: sender domain for this part of DMARC.
157 * If there is no from_header struct, then it's likely this message
158 * is locally generated and relying on fixups to add it. Just skip
159 * the entire DMARC system if we can't find a From: header....or if
160 * there was a previous error.
162 if (from_header
== NULL
|| dmarc_abort
== TRUE
)
166 /* I strongly encourage anybody who can make this better to contact me directly!
167 * <cannonball> Is this an insane way to extract the email address from the From: header?
168 * <jgh_hm> it's sure a horrid layer-crossing....
169 * <cannonball> I'm not denying that :-/
170 * <jgh_hm> there may well be no better though
172 header_from_sender
= expand_string(
173 string_sprintf("${domain:${extract{1}{:}{${addresses:%s}}}}",
174 from_header
->text
) );
175 /* The opendmarc library extracts the domain from the email address, but
176 * only try to store it if it's not empty. Otherwise, skip out of DMARC. */
177 if (strcmp( CCS header_from_sender
, "") == 0)
179 libdm_status
= (dmarc_abort
== TRUE
) ?
181 opendmarc_policy_store_from_domain(dmarc_pctx
, header_from_sender
);
182 if (libdm_status
!= DMARC_PARSE_OKAY
)
184 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to store header From: in DMARC: %s, header was '%s'",
185 opendmarc_policy_status_to_str(libdm_status
), from_header
->text
);
190 /* Skip DMARC if connection is SMTP Auth. Temporarily, admin should
191 * instead do this in the ACLs. */
192 if (dmarc_abort
== FALSE
&& sender_host_authenticated
== NULL
)
194 /* Use the envelope sender domain for this part of DMARC */
195 spf_sender_domain
= expand_string(US
"$sender_address_domain");
196 if ( spf_response
== NULL
)
198 /* No spf data means null envelope sender so generate a domain name
199 * from the sender_host_name || sender_helo_name */
200 if (spf_sender_domain
== NULL
)
202 spf_sender_domain
= (sender_host_name
== NULL
) ? sender_helo_name
: sender_host_name
;
203 uschar
*subdomain
= spf_sender_domain
;
205 while (subdomain
&& *subdomain
!= '.')
210 /* If parsed characters in temp var "subdomain" and is pointing to
211 * a period now, get rid of the period and use that. Otherwise
212 * will use whatever was first set in spf_sender_domain. Goal is to
213 * generate a sane answer, not necessarily the right/best answer b/c
214 * at this point with a null sender, it's a bounce message, making
215 * the spf domain be subjective. */
216 if (count
> 0 && *subdomain
== '.')
219 spf_sender_domain
= subdomain
;
221 log_write(0, LOG_MAIN
, "DMARC using synthesized SPF sender domain = %s\n",
224 debug_printf("DMARC using synthesized SPF sender domain = %s\n", spf_sender_domain
);
226 dmarc_spf_result
= DMARC_POLICY_SPF_OUTCOME_NONE
;
227 origin
= DMARC_POLICY_SPF_ORIGIN_HELO
;
228 spf_human_readable
= US
"";
232 sr
= spf_response
->result
;
233 dmarc_spf_result
= (sr
== SPF_RESULT_NEUTRAL
) ? DMARC_POLICY_SPF_OUTCOME_NONE
:
234 (sr
== SPF_RESULT_PASS
) ? DMARC_POLICY_SPF_OUTCOME_PASS
:
235 (sr
== SPF_RESULT_FAIL
) ? DMARC_POLICY_SPF_OUTCOME_FAIL
:
236 (sr
== SPF_RESULT_SOFTFAIL
) ? DMARC_POLICY_SPF_OUTCOME_TMPFAIL
:
237 DMARC_POLICY_SPF_OUTCOME_NONE
;
238 origin
= DMARC_POLICY_SPF_ORIGIN_MAILFROM
;
239 spf_human_readable
= (uschar
*)spf_response
->header_comment
;
241 debug_printf("DMARC using SPF sender domain = %s\n", spf_sender_domain
);
243 if (strcmp( CCS spf_sender_domain
, "") == 0)
245 if (dmarc_abort
== FALSE
)
247 libdm_status
= opendmarc_policy_store_spf(dmarc_pctx
, spf_sender_domain
,
248 dmarc_spf_result
, origin
, spf_human_readable
);
249 if (libdm_status
!= DMARC_PARSE_OKAY
)
250 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to store spf for DMARC: %s",
251 opendmarc_policy_status_to_str(libdm_status
));
254 /* Now we cycle through the dkim signature results and put into
255 * the opendmarc context, further building the DMARC reply. */
256 sig
= dkim_signatures
;
257 dkim_history_buffer
= US
"";
261 vs
= sig
->verify_status
;
262 dkim_result
= ( vs
== PDKIM_VERIFY_PASS
) ? DMARC_POLICY_DKIM_OUTCOME_PASS
:
263 ( vs
== PDKIM_VERIFY_FAIL
) ? DMARC_POLICY_DKIM_OUTCOME_FAIL
:
264 ( vs
== PDKIM_VERIFY_INVALID
) ? DMARC_POLICY_DKIM_OUTCOME_TMPFAIL
:
265 DMARC_POLICY_DKIM_OUTCOME_NONE
;
266 libdm_status
= opendmarc_policy_store_dkim(dmarc_pctx
, (uschar
*)sig
->domain
,
269 debug_printf("DMARC adding DKIM sender domain = %s\n", sig
->domain
);
270 if (libdm_status
!= DMARC_PARSE_OKAY
)
271 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to store dkim (%s) for DMARC: %s",
272 sig
->domain
, opendmarc_policy_status_to_str(libdm_status
));
274 dkim_history_buffer
= string_sprintf("%sdkim %s %d\n", dkim_history_buffer
,
275 sig
->domain
, dkim_result
);
278 libdm_status
= opendmarc_policy_query_dmarc(dmarc_pctx
, US
"");
279 switch (libdm_status
)
281 case DMARC_DNS_ERROR_NXDOMAIN
:
282 case DMARC_DNS_ERROR_NO_RECORD
:
284 debug_printf("DMARC no record found for %s\n", header_from_sender
);
285 has_dmarc_record
= FALSE
;
287 case DMARC_PARSE_OKAY
:
289 debug_printf("DMARC record found for %s\n", header_from_sender
);
291 case DMARC_PARSE_ERROR_BAD_VALUE
:
293 debug_printf("DMARC record parse error for %s\n", header_from_sender
);
294 has_dmarc_record
= FALSE
;
297 /* everything else, skip dmarc */
299 debug_printf("DMARC skipping (%d), unsure what to do with %s",
300 libdm_status
, from_header
->text
);
301 has_dmarc_record
= FALSE
;
304 /* Can't use exim's string manipulation functions so allocate memory
305 * for libopendmarc using its max hostname length definition. */
306 uschar
*dmarc_domain
= (uschar
*)calloc(DMARC_MAXHOSTNAMELEN
, sizeof(uschar
));
307 libdm_status
= opendmarc_policy_fetch_utilized_domain(dmarc_pctx
, dmarc_domain
,
308 DMARC_MAXHOSTNAMELEN
-1);
309 dmarc_used_domain
= string_copy(dmarc_domain
);
311 if (libdm_status
!= DMARC_PARSE_OKAY
)
313 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to read domainname used for DMARC lookup: %s",
314 opendmarc_policy_status_to_str(libdm_status
));
316 libdm_status
= opendmarc_get_policy_to_enforce(dmarc_pctx
);
317 dmarc_policy
= libdm_status
;
320 case DMARC_POLICY_ABSENT
: /* No DMARC record found */
321 dmarc_status
= US
"norecord";
322 dmarc_pass_fail
= US
"temperror";
323 dmarc_status_text
= US
"No DMARC record";
324 action
= DMARC_RESULT_ACCEPT
;
326 case DMARC_FROM_DOMAIN_ABSENT
: /* No From: domain */
327 dmarc_status
= US
"nofrom";
328 dmarc_pass_fail
= US
"temperror";
329 dmarc_status_text
= US
"No From: domain found";
330 action
= DMARC_RESULT_ACCEPT
;
332 case DMARC_POLICY_NONE
: /* Accept and report */
333 dmarc_status
= US
"none";
334 dmarc_pass_fail
= US
"none";
335 dmarc_status_text
= US
"None, Accept";
336 action
= DMARC_RESULT_ACCEPT
;
338 case DMARC_POLICY_PASS
: /* Explicit accept */
339 dmarc_status
= US
"accept";
340 dmarc_pass_fail
= US
"pass";
341 dmarc_status_text
= US
"Accept";
342 action
= DMARC_RESULT_ACCEPT
;
344 case DMARC_POLICY_REJECT
: /* Explicit reject */
345 dmarc_status
= US
"reject";
346 dmarc_pass_fail
= US
"fail";
347 dmarc_status_text
= US
"Reject";
348 action
= DMARC_RESULT_REJECT
;
350 case DMARC_POLICY_QUARANTINE
: /* Explicit quarantine */
351 dmarc_status
= US
"quarantine";
352 dmarc_pass_fail
= US
"fail";
353 dmarc_status_text
= US
"Quarantine";
354 action
= DMARC_RESULT_QUARANTINE
;
357 dmarc_status
= US
"temperror";
358 dmarc_pass_fail
= US
"temperror";
359 dmarc_status_text
= US
"Internal Policy Error";
360 action
= DMARC_RESULT_TEMPFAIL
;
364 libdm_status
= opendmarc_policy_fetch_alignment(dmarc_pctx
, &da
, &sa
);
365 if (libdm_status
!= DMARC_PARSE_OKAY
)
367 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to read DMARC alignment: %s",
368 opendmarc_policy_status_to_str(libdm_status
));
371 if (has_dmarc_record
== TRUE
)
373 log_write(0, LOG_MAIN
, "DMARC results: spf_domain=%s dmarc_domain=%s "
374 "spf_align=%s dkim_align=%s enforcement='%s'",
375 spf_sender_domain
, dmarc_used_domain
,
376 (sa
==DMARC_POLICY_SPF_ALIGNMENT_PASS
) ?"yes":"no",
377 (da
==DMARC_POLICY_DKIM_ALIGNMENT_PASS
)?"yes":"no",
379 history_file_status
= dmarc_write_history_file();
380 /* Now get the forensic reporting addresses, if any */
381 ruf
= opendmarc_policy_fetch_ruf(dmarc_pctx
, NULL
, 0, 1);
382 dmarc_send_forensic_report(ruf
);
386 /* set some global variables here */
387 dmarc_ar_header
= dmarc_auth_results_header(from_header
, NULL
);
389 /* shut down libopendmarc */
390 if ( dmarc_pctx
!= NULL
)
391 (void) opendmarc_policy_connect_shutdown(dmarc_pctx
);
392 if ( dmarc_disable_verify
== FALSE
)
393 (void) opendmarc_policy_library_shutdown(&dmarc_ctx
);
398 int dmarc_write_history_file()
400 static int history_file_fd
;
403 u_char
**rua
; /* aggregate report addressees */
404 uschar
*history_buffer
= NULL
;
406 if (dmarc_history_file
== NULL
)
407 return DMARC_HIST_DISABLED
;
408 history_file_fd
= log_create(dmarc_history_file
);
410 if (history_file_fd
< 0)
412 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to create DMARC history file: %s",
414 return DMARC_HIST_FILE_ERR
;
417 /* Generate the contents of the history file */
418 history_buffer
= string_sprintf("job %s\n", message_id
);
419 history_buffer
= string_sprintf("%sreporter %s\n", history_buffer
, primary_hostname
);
420 history_buffer
= string_sprintf("%sreceived %ld\n", history_buffer
, time(NULL
));
421 history_buffer
= string_sprintf("%sipaddr %s\n", history_buffer
, sender_host_address
);
422 history_buffer
= string_sprintf("%sfrom %s\n", history_buffer
, header_from_sender
);
423 history_buffer
= string_sprintf("%smfrom %s\n", history_buffer
,
424 expand_string(US
"$sender_address_domain"));
426 if (spf_response
!= NULL
)
427 history_buffer
= string_sprintf("%sspf %d\n", history_buffer
, dmarc_spf_result
);
428 // history_buffer = string_sprintf("%sspf -1\n", history_buffer);
430 history_buffer
= string_sprintf("%s%s", history_buffer
, dkim_history_buffer
);
431 history_buffer
= string_sprintf("%spdomain %s\n", history_buffer
, dmarc_used_domain
);
432 history_buffer
= string_sprintf("%spolicy %d\n", history_buffer
, dmarc_policy
);
434 rua
= opendmarc_policy_fetch_rua(dmarc_pctx
, NULL
, 0, 1);
437 for (tmp_ans
= 0; rua
[tmp_ans
] != NULL
; tmp_ans
++)
439 history_buffer
= string_sprintf("%srua %s\n", history_buffer
, rua
[tmp_ans
]);
443 history_buffer
= string_sprintf("%srua -\n", history_buffer
);
445 opendmarc_policy_fetch_pct(dmarc_pctx
, &tmp_ans
);
446 history_buffer
= string_sprintf("%spct %d\n", history_buffer
, tmp_ans
);
448 opendmarc_policy_fetch_adkim(dmarc_pctx
, &tmp_ans
);
449 history_buffer
= string_sprintf("%sadkim %d\n", history_buffer
, tmp_ans
);
451 opendmarc_policy_fetch_aspf(dmarc_pctx
, &tmp_ans
);
452 history_buffer
= string_sprintf("%saspf %d\n", history_buffer
, tmp_ans
);
454 opendmarc_policy_fetch_p(dmarc_pctx
, &tmp_ans
);
455 history_buffer
= string_sprintf("%sp %d\n", history_buffer
, tmp_ans
);
457 opendmarc_policy_fetch_sp(dmarc_pctx
, &tmp_ans
);
458 history_buffer
= string_sprintf("%ssp %d\n", history_buffer
, tmp_ans
);
460 history_buffer
= string_sprintf("%salign_dkim %d\n", history_buffer
, da
);
461 history_buffer
= string_sprintf("%salign_spf %d\n", history_buffer
, sa
);
462 history_buffer
= string_sprintf("%saction %d\n", history_buffer
, action
);
464 /* Write the contents to the history file */
466 debug_printf("DMARC logging history data for opendmarc reporting%s\n",
467 (host_checking
|| running_in_test_harness
) ? " (not really)" : "");
468 if (host_checking
|| running_in_test_harness
)
471 debug_printf("DMARC history data for debugging:\n%s", history_buffer
);
475 written_len
= write_to_fd_buf(history_file_fd
,
477 Ustrlen(history_buffer
));
478 if (written_len
== 0)
480 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to write to DMARC history file: %s",
482 return DMARC_HIST_WRITE_ERR
;
484 (void)close(history_file_fd
);
486 return DMARC_HIST_OK
;
489 void dmarc_send_forensic_report(u_char
**ruf
)
492 uschar
*recipient
, *save_sender
;
493 BOOL send_status
= FALSE
;
494 error_block
*eblock
= NULL
;
495 FILE *message_file
= NULL
;
497 /* Earlier ACL does not have *required* control=dmarc_enable_forensic */
498 if (dmarc_enable_forensic
== FALSE
)
501 if ((dmarc_policy
== DMARC_POLICY_REJECT
&& action
== DMARC_RESULT_REJECT
) ||
502 (dmarc_policy
== DMARC_POLICY_QUARANTINE
&& action
== DMARC_RESULT_QUARANTINE
) )
506 eblock
= add_to_eblock(eblock
, US
"Sender Domain", dmarc_used_domain
);
507 eblock
= add_to_eblock(eblock
, US
"Sender IP Address", sender_host_address
);
508 eblock
= add_to_eblock(eblock
, US
"Received Date", tod_stamp(tod_full
));
509 eblock
= add_to_eblock(eblock
, US
"SPF Alignment",
510 (sa
==DMARC_POLICY_SPF_ALIGNMENT_PASS
) ?US
"yes":US
"no");
511 eblock
= add_to_eblock(eblock
, US
"DKIM Alignment",
512 (da
==DMARC_POLICY_DKIM_ALIGNMENT_PASS
)?US
"yes":US
"no");
513 eblock
= add_to_eblock(eblock
, US
"DMARC Results", dmarc_status_text
);
514 /* Set a sane default envelope sender */
515 dsn_from
= dmarc_forensic_sender
? dmarc_forensic_sender
:
516 dsn_from
? dsn_from
:
517 string_sprintf("do-not-reply@%s",primary_hostname
);
518 for (c
= 0; ruf
[c
] != NULL
; c
++)
520 recipient
= string_copylc(ruf
[c
]);
521 if (Ustrncmp(recipient
, "mailto:",7))
523 /* Move to first character past the colon */
526 debug_printf("DMARC forensic report to %s%s\n", recipient
,
527 (host_checking
|| running_in_test_harness
) ? " (not really)" : "");
528 if (host_checking
|| running_in_test_harness
)
530 save_sender
= sender_address
;
531 sender_address
= recipient
;
532 send_status
= moan_to_sender(ERRMESS_DMARC_FORENSIC
, eblock
,
533 header_list
, message_file
, FALSE
);
534 sender_address
= save_sender
;
535 if (send_status
== FALSE
)
536 log_write(0, LOG_MAIN
|LOG_PANIC
, "failure to send DMARC forensic report to %s",
543 uschar
*dmarc_exim_expand_query(int what
)
545 if (dmarc_disable_verify
|| !dmarc_pctx
)
546 return dmarc_exim_expand_defaults(what
);
549 case DMARC_VERIFY_STATUS
:
550 return(dmarc_status
);
556 uschar
*dmarc_exim_expand_defaults(int what
)
559 case DMARC_VERIFY_STATUS
:
560 return (dmarc_disable_verify
) ?
568 uschar
*dmarc_auth_results_header(header_line
*from_header
, uschar
*hostname
)
570 uschar
*hdr_tmp
= US
"";
572 /* Allow a server hostname to be passed to this function, but is
573 * currently unused */
574 if (hostname
== NULL
)
575 hostname
= primary_hostname
;
576 hdr_tmp
= string_sprintf("%s %s;", DMARC_AR_HEADER
, hostname
);
579 /* I don't think this belongs here, but left it here commented out
580 * because it was a lot of work to get working right. */
581 if (spf_response
!= NULL
) {
582 uschar
*dmarc_ar_spf
= US
"";
584 sr
= spf_response
->result
;
585 dmarc_ar_spf
= (sr
== SPF_RESULT_NEUTRAL
) ? US
"neutral" :
586 (sr
== SPF_RESULT_PASS
) ? US
"pass" :
587 (sr
== SPF_RESULT_FAIL
) ? US
"fail" :
588 (sr
== SPF_RESULT_SOFTFAIL
) ? US
"softfail" :
590 hdr_tmp
= string_sprintf("%s spf=%s (%s) smtp.mail=%s;",
591 hdr_tmp
, dmarc_ar_spf_result
,
592 spf_response
->header_comment
,
593 expand_string(US
"$sender_address") );
596 hdr_tmp
= string_sprintf("%s dmarc=%s",
597 hdr_tmp
, dmarc_pass_fail
);
598 if (header_from_sender
)
599 hdr_tmp
= string_sprintf("%s header.from=%s",
600 hdr_tmp
, header_from_sender
);
604 #endif /* EXPERIMENTAL_SPF */
605 #endif /* EXPERIMENTAL_DMARC */
607 // vim:sw=2 expandtab