1 /* $Cambridge: exim/src/src/dkim.c,v 1.1.2.12 2009/05/20 14:30:14 tom Exp $ */
3 /*************************************************
4 * Exim - an Internet mail transport agent *
5 *************************************************/
7 /* Copyright (c) University of Cambridge 2009 */
8 /* See the file NOTICE for conditions of use and distribution. */
10 /* Code for DKIM support. Other DKIM relevant code is in
11 receive.c, transport.c and transports/smtp.c */
17 #include "pdkim/pdkim.h"
19 pdkim_ctx *dkim_verify_ctx = NULL;
20 pdkim_signature *dkim_signatures = NULL;
22 int dkim_exim_query_dns_txt(char *name, char *answer) {
27 if (dns_lookup(&dnsa, (uschar *)name, T_TXT, NULL) != DNS_SUCCEED) return PDKIM_FAIL;
29 /* Search for TXT record */
30 for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
32 rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
33 if (rr->type == T_TXT) break;
35 /* Copy record content to the answer buffer */
38 int answer_offset = 0;
39 while (rr_offset < rr->size) {
40 uschar len = (rr->data)[rr_offset++];
41 snprintf(answer+(answer_offset),
42 PDKIM_DNS_TXT_MAX_RECLEN-(answer_offset),
43 "%.*s", (int)len, (char *)((rr->data)+rr_offset));
48 else return PDKIM_FAIL;
54 void dkim_exim_verify_init(void) {
56 /* Free previous context if there is one */
57 if (dkim_verify_ctx) pdkim_free_ctx(dkim_verify_ctx);
59 /* Create new context */
60 dkim_verify_ctx = pdkim_init_verify(PDKIM_INPUT_SMTP,
61 &dkim_exim_query_dns_txt
64 if (dkim_verify_ctx != NULL) {
65 dkim_collect_input = TRUE;
66 pdkim_set_debug_stream(dkim_verify_ctx,debug_file);
68 else dkim_collect_input = FALSE;
73 void dkim_exim_verify_feed(uschar *data, int len) {
74 if (dkim_collect_input &&
75 pdkim_feed(dkim_verify_ctx,
77 len) != PDKIM_OK) dkim_collect_input = FALSE;
81 void dkim_exim_verify_finish(void) {
83 /* Delete eventual previous signature chain */
84 dkim_signatures = NULL;
86 /* If we have arrived here with dkim_collect_input == FALSE, it
87 means there was a processing error somewhere along the way.
88 Log the incident and disable futher verification. */
89 if (!dkim_collect_input) {
90 log_write(0, LOG_MAIN|LOG_PANIC, "DKIM: Error while running this message through validation, disabling signature verification.");
91 dkim_disable_verify = TRUE;
94 dkim_collect_input = FALSE;
96 /* Finish DKIM operation and fetch link to signatures chain */
97 if (pdkim_feed_finish(dkim_verify_ctx,&dkim_signatures) != PDKIM_OK) return;
99 /* Log a line for each signature */
100 while (dkim_signatures != NULL) {
103 uschar *logmsg = string_append(NULL, &size, &ptr, 5,
105 string_sprintf( "DKIM: d=%s s=%s c=%s/%s a=%s ",
106 dkim_signatures->domain,
107 dkim_signatures->selector,
108 (dkim_signatures->canon_headers == PDKIM_CANON_SIMPLE)?"simple":"relaxed",
109 (dkim_signatures->canon_body == PDKIM_CANON_SIMPLE)?"simple":"relaxed",
110 (dkim_signatures->algo == PDKIM_ALGO_RSA_SHA256)?"rsa-sha256":"rsa-sha1"
113 ((dkim_signatures->identity != NULL)?
114 string_sprintf("i=%s ", dkim_signatures->identity)
118 ((dkim_signatures->created > 0)?
119 string_sprintf("t=%lu ", dkim_signatures->created)
123 ((dkim_signatures->expires > 0)?
124 string_sprintf("x=%lu ", dkim_signatures->expires)
128 ((dkim_signatures->bodylength > -1)?
129 string_sprintf("l=%lu ", dkim_signatures->bodylength)
135 switch(dkim_signatures->verify_status) {
136 case PDKIM_VERIFY_NONE:
137 logmsg = string_append(logmsg, &size, &ptr, 1, "[not verified]");
139 case PDKIM_VERIFY_INVALID:
140 logmsg = string_append(logmsg, &size, &ptr, 1, "[invalid - ");
141 switch (dkim_signatures->verify_ext_status) {
142 case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
143 logmsg = string_append(logmsg, &size, &ptr, 1, "public key record (currently?) unavailable]");
145 case PDKIM_VERIFY_INVALID_BUFFER_SIZE:
146 logmsg = string_append(logmsg, &size, &ptr, 1, "overlong public key record]");
148 case PDKIM_VERIFY_INVALID_PUBKEY_PARSING:
149 logmsg = string_append(logmsg, &size, &ptr, 1, "syntax error in public key record]");
152 logmsg = string_append(logmsg, &size, &ptr, 1, "unspecified problem]");
155 case PDKIM_VERIFY_FAIL:
156 logmsg = string_append(logmsg, &size, &ptr, 1, "[verification failed - ");
157 switch (dkim_signatures->verify_ext_status) {
158 case PDKIM_VERIFY_FAIL_BODY:
159 logmsg = string_append(logmsg, &size, &ptr, 1, "body hash mismatch (body probably modified in transit)]");
161 case PDKIM_VERIFY_FAIL_MESSAGE:
162 logmsg = string_append(logmsg, &size, &ptr, 1, "signature did not verify (headers probably modified in transit)]");
165 logmsg = string_append(logmsg, &size, &ptr, 1, "unspecified reason]");
168 case PDKIM_VERIFY_PASS:
169 logmsg = string_append(logmsg, &size, &ptr, 1, "[verification succeeded]");
174 log_write(0, LOG_MAIN, (char *)logmsg);
176 /* Log next signature */
177 dkim_signatures = dkim_signatures->next;
182 void dkim_exim_verify_result(uschar *domain, uschar **result, uschar **error) {
183 if (dkim_verify_ctx) {
189 uschar *dkim_exim_sign(int dkim_fd,
190 uschar *dkim_private_key,
192 uschar *dkim_selector,
194 uschar *dkim_sign_headers) {
195 pdkim_ctx *ctx = NULL;
197 pdkim_signature *signature;
202 int old_pool = store_pool;
204 dkim_domain = expand_string(dkim_domain);
205 if (dkim_domain == NULL) {
206 /* expansion error, do not send message. */
207 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
208 "dkim_domain: %s", expand_string_message);
212 /* Set up $dkim_domain expansion variable. */
213 dkim_signing_domain = dkim_domain;
215 /* Get selector to use. */
216 dkim_selector = expand_string(dkim_selector);
217 if (dkim_selector == NULL) {
218 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
219 "dkim_selector: %s", expand_string_message);
223 /* Set up $dkim_selector expansion variable. */
224 dkim_signing_selector = dkim_selector;
226 /* Get canonicalization to use */
227 dkim_canon = expand_string(dkim_canon?dkim_canon:US"relaxed");
228 if (dkim_canon == NULL) {
229 /* expansion error, do not send message. */
230 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
231 "dkim_canon: %s", expand_string_message);
235 if (Ustrcmp(dkim_canon, "relaxed") == 0)
236 pdkim_canon = PDKIM_CANON_RELAXED;
237 else if (Ustrcmp(dkim_canon, "simple") == 0)
238 pdkim_canon = PDKIM_CANON_RELAXED;
240 log_write(0, LOG_MAIN, "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",dkim_canon);
241 pdkim_canon = PDKIM_CANON_RELAXED;
244 /* Expand signing headers once */
245 if (dkim_sign_headers != NULL) {
246 dkim_sign_headers = expand_string(dkim_sign_headers);
247 if (dkim_sign_headers == NULL) {
248 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
249 "dkim_sign_headers: %s", expand_string_message);
255 /* Get private key to use. */
256 dkim_private_key = expand_string(dkim_private_key);
257 if (dkim_private_key == NULL) {
258 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
259 "dkim_private_key: %s", expand_string_message);
263 if ( (Ustrlen(dkim_private_key) == 0) ||
264 (Ustrcmp(dkim_private_key,"0") == 0) ||
265 (Ustrcmp(dkim_private_key,"false") == 0) ) {
266 /* don't sign, but no error */
271 if (dkim_private_key[0] == '/') {
273 /* Looks like a filename, load the private key. */
274 memset(big_buffer,0,big_buffer_size);
275 privkey_fd = open(CS dkim_private_key,O_RDONLY);
276 (void)read(privkey_fd,big_buffer,16383);
277 (void)close(privkey_fd);
278 dkim_private_key = big_buffer;
281 ctx = pdkim_init_sign(PDKIM_INPUT_SMTP,
282 (char *)dkim_signing_domain,
283 (char *)dkim_signing_selector,
284 (char *)dkim_private_key
287 pdkim_set_debug_stream(ctx,debug_file);
289 pdkim_set_optional(ctx,
290 (char *)dkim_sign_headers,
295 PDKIM_ALGO_RSA_SHA256,
299 while((sread = read(dkim_fd,&buf,4096)) > 0) {
300 if (pdkim_feed(ctx,buf,sread) != PDKIM_OK) {
305 /* Handle failed read above. */
307 debug_printf("DKIM: Error reading -K file.\n");
313 if (pdkim_feed_finish(ctx,&signature) != PDKIM_OK)
316 rc = store_get(strlen(signature->signature_header)+3);
317 Ustrcpy(rc,US signature->signature_header);
318 Ustrcat(rc,US"\r\n");
324 store_pool = old_pool;