Commit | Line | Data |
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42055a33 JH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
9242a7e8 | 5 | /* Copyright (c) University of Cambridge 1995 - 2017 */ |
42055a33 JH |
6 | /* See the file NOTICE for conditions of use and distribution. */ |
7 | ||
8 | /* Transport shim for dkim signing */ | |
9 | ||
42055a33 JH |
10 | |
11 | #include "exim.h" | |
12 | ||
09d5060c JH |
13 | #ifndef DISABLE_DKIM /* rest of file */ |
14 | ||
42055a33 JH |
15 | |
16 | static BOOL | |
17 | dkt_sign_fail(struct ob_dkim * dkim, int * errp) | |
18 | { | |
19 | if (dkim->dkim_strict) | |
20 | { | |
21 | uschar * dkim_strict_result = expand_string(dkim->dkim_strict); | |
22 | ||
23 | if (dkim_strict_result) | |
24 | if ( (strcmpic(dkim->dkim_strict, US"1") == 0) || | |
25 | (strcmpic(dkim->dkim_strict, US"true") == 0) ) | |
26 | { | |
27 | /* Set errno to something halfway meaningful */ | |
28 | *errp = EACCES; | |
29 | log_write(0, LOG_MAIN, "DKIM: message could not be signed," | |
30 | " and dkim_strict is set. Deferring message delivery."); | |
31 | return FALSE; | |
32 | } | |
33 | } | |
34 | return TRUE; | |
35 | } | |
36 | ||
d315eda1 JH |
37 | /* Send the file at in_fd down the output fd */ |
38 | ||
42055a33 | 39 | static BOOL |
bb07bcd3 JH |
40 | dkt_send_file(int out_fd, int in_fd, off_t off |
41 | #ifdef OS_SENDFILE | |
42 | , size_t size | |
43 | #endif | |
44 | ) | |
42055a33 | 45 | { |
47c292c9 | 46 | #ifdef OS_SENDFILE |
6c140c01 | 47 | DEBUG(D_transport) debug_printf("send file fd=%d size=%u\n", out_fd, (unsigned)(size - off)); |
47c292c9 JH |
48 | #else |
49 | DEBUG(D_transport) debug_printf("send file fd=%d\n", out_fd); | |
50 | #endif | |
42055a33 JH |
51 | |
52 | /*XXX should implement timeout, like transport_write_block_fd() ? */ | |
53 | ||
7d758a6a | 54 | #ifdef OS_SENDFILE |
42055a33 JH |
55 | /* We can use sendfile() to shove the file contents |
56 | to the socket. However only if we don't use TLS, | |
57 | as then there's another layer of indirection | |
58 | before the data finally hits the socket. */ | |
59 | if (tls_out.active != out_fd) | |
60 | { | |
61 | ssize_t copied = 0; | |
62 | ||
63 | while(copied >= 0 && off < size) | |
7d758a6a | 64 | copied = os_sendfile(out_fd, in_fd, &off, size - off); |
42055a33 JH |
65 | if (copied < 0) |
66 | return FALSE; | |
67 | } | |
68 | else | |
69 | ||
70 | #endif | |
71 | ||
72 | { | |
73 | int sread, wwritten; | |
74 | ||
328c5688 | 75 | /* Rewind file */ |
d315eda1 | 76 | if (lseek(in_fd, off, SEEK_SET) < 0) return FALSE; |
328c5688 | 77 | |
42055a33 | 78 | /* Send file down the original fd */ |
d315eda1 | 79 | while((sread = read(in_fd, deliver_out_buffer, DELIVER_OUT_BUFFER_SIZE)) > 0) |
42055a33 JH |
80 | { |
81 | uschar * p = deliver_out_buffer; | |
82 | /* write the chunk */ | |
83 | ||
84 | while (sread) | |
85 | { | |
86 | #ifdef SUPPORT_TLS | |
87 | wwritten = tls_out.active == out_fd | |
925ac8e4 | 88 | ? tls_write(FALSE, p, sread, FALSE) |
42055a33 JH |
89 | : write(out_fd, CS p, sread); |
90 | #else | |
91 | wwritten = write(out_fd, CS p, sread); | |
92 | #endif | |
93 | if (wwritten == -1) | |
94 | return FALSE; | |
95 | p += wwritten; | |
96 | sread -= wwritten; | |
97 | } | |
98 | } | |
99 | ||
100 | if (sread == -1) | |
101 | return FALSE; | |
102 | } | |
103 | ||
104 | return TRUE; | |
105 | } | |
106 | ||
107 | ||
108 | ||
109 | ||
110 | /* This function is a wrapper around transport_write_message(). | |
111 | It is only called from the smtp transport if DKIM or Domainkeys support | |
112 | is active and no transport filter is to be used. | |
113 | ||
114 | Arguments: | |
115 | As for transport_write_message() in transort.c, with additional arguments | |
116 | for DKIM. | |
117 | ||
118 | Returns: TRUE on success; FALSE (with errno) for any failure | |
119 | */ | |
120 | ||
121 | static BOOL | |
122 | dkt_direct(transport_ctx * tctx, struct ob_dkim * dkim, | |
123 | const uschar ** err) | |
124 | { | |
125 | int save_fd = tctx->u.fd; | |
126 | int save_options = tctx->options; | |
328c5688 | 127 | BOOL save_wireformat = spool_file_wireformat; |
9e70917d | 128 | uschar * hdrs; |
acec9514 | 129 | gstring * dkim_signature; |
9e70917d | 130 | int hsize; |
42055a33 JH |
131 | const uschar * errstr; |
132 | BOOL rc; | |
133 | ||
134 | DEBUG(D_transport) debug_printf("dkim signing direct-mode\n"); | |
135 | ||
328c5688 JH |
136 | /* Get headers in string for signing and transmission. Do CRLF |
137 | and dotstuffing (but no body nor dot-termination) */ | |
42055a33 JH |
138 | |
139 | tctx->u.msg = NULL; | |
140 | tctx->options = tctx->options & ~(topt_end_dot | topt_use_bdat) | |
141 | | topt_output_string | topt_no_body; | |
142 | ||
143 | rc = transport_write_message(tctx, 0); | |
acec9514 JH |
144 | hdrs = string_from_gstring(tctx->u.msg); |
145 | hsize = tctx->u.msg->ptr; | |
42055a33 JH |
146 | |
147 | tctx->u.fd = save_fd; | |
148 | tctx->options = save_options; | |
149 | if (!rc) return FALSE; | |
150 | ||
151 | /* Get signatures for headers plus spool data file */ | |
152 | ||
153 | dkim->dot_stuffed = !!(save_options & topt_end_dot); | |
154 | ||
9e70917d | 155 | if (!(dkim_signature = dkim_exim_sign(deliver_datafile, SPOOL_DATA_START_OFFSET, |
42055a33 | 156 | hdrs, dkim, &errstr))) |
9e70917d JH |
157 | if (!(rc = dkt_sign_fail(dkim, &errno))) |
158 | { | |
159 | *err = errstr; | |
160 | return FALSE; | |
161 | } | |
42055a33 JH |
162 | |
163 | /* Write the signature and headers into the deliver-out-buffer. This should | |
164 | mean they go out in the same packet as the MAIL, RCPT and (first) BDAT commands | |
165 | (transport_write_message() sizes the BDAT for the buffered amount) - for short | |
328c5688 JH |
166 | messages, the BDAT LAST command. We want no dotstuffing expansion here, it |
167 | having already been done - but we have to say we want CRLF output format, and | |
168 | temporarily set the marker for possible already-CRLF input. */ | |
42055a33 | 169 | |
328c5688 JH |
170 | tctx->options &= ~topt_escape_headers; |
171 | spool_file_wireformat = TRUE; | |
42055a33 | 172 | transport_write_reset(0); |
9e70917d | 173 | if ( ( dkim_signature |
acec9514 JH |
174 | && dkim_signature->ptr > 0 |
175 | && !write_chunk(tctx, dkim_signature->s, dkim_signature->ptr) | |
9e70917d JH |
176 | ) |
177 | || !write_chunk(tctx, hdrs, hsize) | |
178 | ) | |
42055a33 JH |
179 | return FALSE; |
180 | ||
328c5688 | 181 | spool_file_wireformat = save_wireformat; |
42055a33 JH |
182 | tctx->options = save_options | topt_no_headers | topt_continuation; |
183 | ||
184 | if (!(transport_write_message(tctx, 0))) | |
185 | return FALSE; | |
186 | ||
187 | tctx->options = save_options; | |
188 | return TRUE; | |
189 | } | |
190 | ||
191 | ||
192 | /* This function is a wrapper around transport_write_message(). | |
193 | It is only called from the smtp transport if DKIM or Domainkeys support | |
194 | is active and a transport filter is to be used. The function sets up a | |
195 | replacement fd into a -K file, then calls the normal function. This way, the | |
196 | exact bits that exim would have put "on the wire" will end up in the file | |
197 | (except for TLS encapsulation, which is the very very last thing). When we | |
198 | are done signing the file, send the signed message down the original fd (or | |
199 | TLS fd). | |
200 | ||
201 | Arguments: | |
202 | As for transport_write_message() in transort.c, with additional arguments | |
203 | for DKIM. | |
204 | ||
205 | Returns: TRUE on success; FALSE (with errno) for any failure | |
206 | */ | |
207 | ||
208 | static BOOL | |
209 | dkt_via_kfile(transport_ctx * tctx, struct ob_dkim * dkim, const uschar ** err) | |
210 | { | |
211 | int dkim_fd; | |
212 | int save_errno = 0; | |
213 | BOOL rc; | |
9e70917d | 214 | uschar * dkim_spool_name; |
acec9514 | 215 | gstring * dkim_signature; |
9e70917d | 216 | int options, dlen; |
42055a33 JH |
217 | off_t k_file_size; |
218 | const uschar * errstr; | |
219 | ||
220 | dkim_spool_name = spool_fname(US"input", message_subdir, message_id, | |
221 | string_sprintf("-%d-K", (int)getpid())); | |
222 | ||
223 | DEBUG(D_transport) debug_printf("dkim signing via file %s\n", dkim_spool_name); | |
224 | ||
225 | if ((dkim_fd = Uopen(dkim_spool_name, O_RDWR|O_CREAT|O_TRUNC, SPOOL_MODE)) < 0) | |
226 | { | |
227 | /* Can't create spool file. Ugh. */ | |
228 | rc = FALSE; | |
229 | save_errno = errno; | |
230 | *err = string_sprintf("dkim spoolfile create: %s", strerror(errno)); | |
231 | goto CLEANUP; | |
232 | } | |
233 | ||
234 | /* Call transport utility function to write the -K file; does the CRLF expansion | |
235 | (but, in the CHUNKING case, neither dot-stuffing nor dot-termination). */ | |
236 | ||
237 | { | |
238 | int save_fd = tctx->u.fd; | |
239 | tctx->u.fd = dkim_fd; | |
240 | options = tctx->options; | |
241 | tctx->options &= ~topt_use_bdat; | |
242 | ||
243 | rc = transport_write_message(tctx, 0); | |
244 | ||
245 | tctx->u.fd = save_fd; | |
246 | tctx->options = options; | |
247 | } | |
248 | ||
249 | /* Save error state. We must clean up before returning. */ | |
250 | if (!rc) | |
251 | { | |
252 | save_errno = errno; | |
253 | goto CLEANUP; | |
254 | } | |
255 | ||
256 | /* Feed the file to the goats^W DKIM lib */ | |
257 | ||
258 | dkim->dot_stuffed = !!(options & topt_end_dot); | |
9e70917d | 259 | if (!(dkim_signature = dkim_exim_sign(dkim_fd, 0, NULL, dkim, &errstr))) |
42055a33 | 260 | { |
9e70917d JH |
261 | dlen = 0; |
262 | if (!(rc = dkt_sign_fail(dkim, &save_errno))) | |
263 | { | |
264 | *err = errstr; | |
265 | goto CLEANUP; | |
266 | } | |
42055a33 | 267 | } |
9e70917d | 268 | else |
acec9514 | 269 | dlen = dkim_signature->ptr; |
42055a33 | 270 | |
7d758a6a | 271 | #ifndef OS_SENDFILE |
42055a33 JH |
272 | if (options & topt_use_bdat) |
273 | #endif | |
d315eda1 JH |
274 | if ((k_file_size = lseek(dkim_fd, 0, SEEK_END)) < 0) |
275 | { | |
276 | *err = string_sprintf("dkim spoolfile seek: %s", strerror(errno)); | |
277 | goto CLEANUP; | |
278 | } | |
42055a33 JH |
279 | |
280 | if (options & topt_use_bdat) | |
281 | { | |
282 | /* On big messages output a precursor chunk to get any pipelined | |
283 | MAIL & RCPT commands flushed, then reap the responses so we can | |
284 | error out on RCPT rejects before sending megabytes. */ | |
285 | ||
9e70917d JH |
286 | if ( dlen + k_file_size > DELIVER_OUT_BUFFER_SIZE |
287 | && dlen > 0) | |
42055a33 | 288 | { |
9e70917d JH |
289 | if ( tctx->chunk_cb(tctx, dlen, 0) != OK |
290 | || !transport_write_block(tctx, | |
acec9514 | 291 | dkim_signature->s, dlen, FALSE) |
42055a33 JH |
292 | || tctx->chunk_cb(tctx, 0, tc_reap_prev) != OK |
293 | ) | |
294 | goto err; | |
9e70917d | 295 | dlen = 0; |
42055a33 JH |
296 | } |
297 | ||
298 | /* Send the BDAT command for the entire message, as a single LAST-marked | |
299 | chunk. */ | |
300 | ||
9e70917d | 301 | if (tctx->chunk_cb(tctx, dlen + k_file_size, tc_chunk_last) != OK) |
42055a33 JH |
302 | goto err; |
303 | } | |
304 | ||
acec9514 | 305 | if(dlen > 0 && !transport_write_block(tctx, dkim_signature->s, dlen, TRUE)) |
42055a33 JH |
306 | goto err; |
307 | ||
bb07bcd3 JH |
308 | if (!dkt_send_file(tctx->u.fd, dkim_fd, 0 |
309 | #ifdef OS_SENDFILE | |
310 | , k_file_size | |
311 | #endif | |
312 | )) | |
42055a33 JH |
313 | { |
314 | save_errno = errno; | |
315 | rc = FALSE; | |
316 | } | |
317 | ||
318 | CLEANUP: | |
319 | /* unlink -K file */ | |
d315eda1 | 320 | if (dkim_fd >= 0) (void)close(dkim_fd); |
42055a33 JH |
321 | Uunlink(dkim_spool_name); |
322 | errno = save_errno; | |
323 | return rc; | |
324 | ||
325 | err: | |
326 | save_errno = errno; | |
327 | rc = FALSE; | |
328 | goto CLEANUP; | |
329 | } | |
330 | ||
331 | ||
332 | ||
333 | /*************************************************************************************************** | |
334 | * External interface to write the message, while signing it with DKIM and/or Domainkeys * | |
335 | ***************************************************************************************************/ | |
336 | ||
337 | /* This function is a wrapper around transport_write_message(). | |
338 | It is only called from the smtp transport if DKIM or Domainkeys support | |
339 | is compiled in. | |
340 | ||
341 | Arguments: | |
342 | As for transport_write_message() in transort.c, with additional arguments | |
343 | for DKIM. | |
344 | ||
345 | Returns: TRUE on success; FALSE (with errno) for any failure | |
346 | */ | |
347 | ||
348 | BOOL | |
349 | dkim_transport_write_message(transport_ctx * tctx, | |
350 | struct ob_dkim * dkim, const uschar ** err) | |
351 | { | |
352 | /* If we can't sign, just call the original function. */ | |
353 | ||
354 | if (!(dkim->dkim_private_key && dkim->dkim_domain && dkim->dkim_selector)) | |
355 | return transport_write_message(tctx, 0); | |
356 | ||
357 | /* If there is no filter command set up, construct the message and calculate | |
358 | a dkim signature of it, send the signature and a reconstructed message. This | |
359 | avoids using a temprary file. */ | |
360 | ||
361 | if ( !transport_filter_argv | |
362 | || !*transport_filter_argv | |
363 | || !**transport_filter_argv | |
364 | ) | |
365 | return dkt_direct(tctx, dkim, err); | |
366 | ||
367 | /* Use the transport path to write a file, calculate a dkim signature, | |
368 | send the signature and then send the file. */ | |
369 | ||
370 | return dkt_via_kfile(tctx, dkim, err); | |
371 | } | |
372 | ||
373 | #endif /* whole file */ | |
374 | ||
375 | /* vi: aw ai sw=2 | |
376 | */ | |
377 | /* End of dkim_transport.c */ |