1 /* $Cambridge: exim/src/src/dkim.c,v 1.1.2.11 2009/05/19 09:49:14 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 1;
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));
54 int 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 = 1;
66 pdkim_set_debug_stream(dkim_verify_ctx,debug_file);
70 dkim_collect_input = 0;
76 int dkim_exim_verify_feed(uschar *data, int len) {
77 if (pdkim_feed(dkim_verify_ctx,
79 len) != PDKIM_OK) return 0;
84 int dkim_exim_verify_finish(void) {
85 dkim_signatures = NULL;
86 dkim_collect_input = 0;
87 if (pdkim_feed_finish(dkim_verify_ctx,&dkim_signatures) != PDKIM_OK) return 0;
89 while (dkim_signatures != NULL) {
92 uschar *logmsg = string_append(NULL, &size, &ptr, 5,
94 string_sprintf( "DKIM: v=%u d=%s s=%s c=%s/%s a=%s ",
95 dkim_signatures->version,
96 dkim_signatures->domain,
97 dkim_signatures->selector,
98 (dkim_signatures->canon_headers == PDKIM_CANON_SIMPLE)?"simple":"relaxed",
99 (dkim_signatures->canon_body == PDKIM_CANON_SIMPLE)?"simple":"relaxed",
100 (dkim_signatures->algo == PDKIM_ALGO_RSA_SHA256)?"rsa-sha256":"rsa-sha1"
103 ((dkim_signatures->identity != NULL)?
104 string_sprintf("i=%s ", dkim_signatures->identity)
108 ((dkim_signatures->created > 0)?
109 string_sprintf("t=%lu ", dkim_signatures->created)
113 ((dkim_signatures->expires > 0)?
114 string_sprintf("x=%lu ", dkim_signatures->expires)
118 ((dkim_signatures->bodylength > -1)?
119 string_sprintf("l=%lu ", dkim_signatures->bodylength)
125 switch(dkim_signatures->verify_status) {
126 case PDKIM_VERIFY_NONE:
127 logmsg = string_append(logmsg, &size, &ptr, 1, "[not verified]");
129 case PDKIM_VERIFY_INVALID:
130 logmsg = string_append(logmsg, &size, &ptr, 1, "[invalid - ");
131 switch (dkim_signatures->verify_ext_status) {
132 case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
133 logmsg = string_append(logmsg, &size, &ptr, 1, "public key record (currently?) unavailable]");
135 case PDKIM_VERIFY_INVALID_BUFFER_SIZE:
136 logmsg = string_append(logmsg, &size, &ptr, 1, "overlong public key record]");
138 case PDKIM_VERIFY_INVALID_PUBKEY_PARSING:
139 logmsg = string_append(logmsg, &size, &ptr, 1, "syntax error in public key record]");
142 logmsg = string_append(logmsg, &size, &ptr, 1, "unspecified problem]");
145 case PDKIM_VERIFY_FAIL:
146 logmsg = string_append(logmsg, &size, &ptr, 1, "[verification failed - ");
147 switch (dkim_signatures->verify_ext_status) {
148 case PDKIM_VERIFY_FAIL_BODY:
149 logmsg = string_append(logmsg, &size, &ptr, 1, "body hash mismatch (body probably modified in transit)]");
151 case PDKIM_VERIFY_FAIL_MESSAGE:
152 logmsg = string_append(logmsg, &size, &ptr, 1, "signature did not verify (headers probably modified in transit)]");
155 logmsg = string_append(logmsg, &size, &ptr, 1, "unspecified reason]");
158 case PDKIM_VERIFY_PASS:
159 logmsg = string_append(logmsg, &size, &ptr, 1, "[verification succeeded]");
164 log_write(0, LOG_MAIN, (char *)logmsg);
166 /* Try next signature */
167 dkim_signatures = dkim_signatures->next;
170 return dkim_signatures?1:0;
174 int dkim_exim_verify_result(uschar *domain, uschar **result, uschar **error) {
176 if (dkim_verify_ctx) {
184 uschar *dkim_exim_sign(int dkim_fd,
185 uschar *dkim_private_key,
187 uschar *dkim_selector,
189 uschar *dkim_sign_headers) {
190 pdkim_ctx *ctx = NULL;
192 pdkim_signature *signature;
197 int old_pool = store_pool;
199 dkim_domain = expand_string(dkim_domain);
200 if (dkim_domain == NULL) {
201 /* expansion error, do not send message. */
202 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
203 "dkim_domain: %s", expand_string_message);
207 /* Set up $dkim_domain expansion variable. */
208 dkim_signing_domain = dkim_domain;
210 /* Get selector to use. */
211 dkim_selector = expand_string(dkim_selector);
212 if (dkim_selector == NULL) {
213 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
214 "dkim_selector: %s", expand_string_message);
218 /* Set up $dkim_selector expansion variable. */
219 dkim_signing_selector = dkim_selector;
221 /* Get canonicalization to use */
222 dkim_canon = expand_string(dkim_canon?dkim_canon:US"relaxed");
223 if (dkim_canon == NULL) {
224 /* expansion error, do not send message. */
225 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
226 "dkim_canon: %s", expand_string_message);
230 if (Ustrcmp(dkim_canon, "relaxed") == 0)
231 pdkim_canon = PDKIM_CANON_RELAXED;
232 else if (Ustrcmp(dkim_canon, "simple") == 0)
233 pdkim_canon = PDKIM_CANON_RELAXED;
235 log_write(0, LOG_MAIN, "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",dkim_canon);
236 pdkim_canon = PDKIM_CANON_RELAXED;
239 /* Expand signing headers once */
240 if (dkim_sign_headers != NULL) {
241 dkim_sign_headers = expand_string(dkim_sign_headers);
242 if (dkim_sign_headers == NULL) {
243 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
244 "dkim_sign_headers: %s", expand_string_message);
250 /* Get private key to use. */
251 dkim_private_key = expand_string(dkim_private_key);
252 if (dkim_private_key == NULL) {
253 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
254 "dkim_private_key: %s", expand_string_message);
258 if ( (Ustrlen(dkim_private_key) == 0) ||
259 (Ustrcmp(dkim_private_key,"0") == 0) ||
260 (Ustrcmp(dkim_private_key,"false") == 0) ) {
261 /* don't sign, but no error */
266 if (dkim_private_key[0] == '/') {
268 /* Looks like a filename, load the private key. */
269 memset(big_buffer,0,big_buffer_size);
270 privkey_fd = open(CS dkim_private_key,O_RDONLY);
271 (void)read(privkey_fd,big_buffer,16383);
272 (void)close(privkey_fd);
273 dkim_private_key = big_buffer;
276 ctx = pdkim_init_sign(PDKIM_INPUT_SMTP,
277 (char *)dkim_signing_domain,
278 (char *)dkim_signing_selector,
279 (char *)dkim_private_key
282 pdkim_set_debug_stream(ctx,debug_file);
284 pdkim_set_optional(ctx,
285 (char *)dkim_sign_headers,
290 PDKIM_ALGO_RSA_SHA256,
294 while((sread = read(dkim_fd,&buf,4096)) > 0) {
295 if (pdkim_feed(ctx,buf,sread) != PDKIM_OK) {
300 /* Handle failed read above. */
302 debug_printf("DKIM: Error reading -K file.\n");
308 if (pdkim_feed_finish(ctx,&signature) != PDKIM_OK)
311 rc = store_get(strlen(signature->signature_header)+3);
312 Ustrcpy(rc,US signature->signature_header);
313 Ustrcat(rc,US"\r\n");
319 store_pool = old_pool;