1 /* $Cambridge: exim/src/src/dkim.c,v 1.1.2.7 2009/04/30 08:21:30 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) {
90 debug_printf("DKIM: Signature from domain '%s': ",dkim_signatures->domain);
91 switch(dkim_signatures->verify_status) {
92 case PDKIM_VERIFY_NONE:
93 debug_printf("not verified\n");
94 log_write(0, LOG_MAIN, "DKIM: Signature from domain '%s', selector '%s': "
95 "not verified", dkim_signatures->domain, dkim_signatures->selector);
97 case PDKIM_VERIFY_INVALID:
98 debug_printf("invalid\n");
99 log_write(0, LOG_MAIN, "DKIM: Signature from domain '%s', selector '%s': "
100 "invalid", dkim_signatures->domain, dkim_signatures->selector);
102 case PDKIM_VERIFY_FAIL:
103 debug_printf("verification failed\n");
104 log_write(0, LOG_MAIN, "DKIM: Signature from domain '%s', selector '%s': "
105 "verification failed", dkim_signatures->domain, dkim_signatures->selector);
107 case PDKIM_VERIFY_PASS:
108 debug_printf("verification succeeded\n");
109 log_write(0, LOG_MAIN, "DKIM: Signature from domain '%s', selector '%s': "
110 "verification succeeded", dkim_signatures->domain, dkim_signatures->selector);
113 /* Try next signature */
114 dkim_signatures = dkim_signatures->next;
117 return dkim_signatures?1:0;
121 int dkim_exim_verify_result(uschar *domain, uschar **result, uschar **error) {
123 if (dkim_verify_ctx) {
131 uschar *dkim_exim_sign(int dkim_fd,
132 uschar *dkim_private_key,
134 uschar *dkim_selector,
136 uschar *dkim_sign_headers) {
137 pdkim_ctx *ctx = NULL;
139 pdkim_signature *signature;
144 int old_pool = store_pool;
146 dkim_domain = expand_string(dkim_domain);
147 if (dkim_domain == NULL) {
148 /* expansion error, do not send message. */
149 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
150 "dkim_domain: %s", expand_string_message);
154 /* Set up $dkim_domain expansion variable. */
155 dkim_signing_domain = dkim_domain;
157 /* Get selector to use. */
158 dkim_selector = expand_string(dkim_selector);
159 if (dkim_selector == NULL) {
160 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
161 "dkim_selector: %s", expand_string_message);
165 /* Set up $dkim_selector expansion variable. */
166 dkim_signing_selector = dkim_selector;
168 /* Get canonicalization to use */
169 dkim_canon = expand_string(dkim_canon?dkim_canon:US"relaxed");
170 if (dkim_canon == NULL) {
171 /* expansion error, do not send message. */
172 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
173 "dkim_canon: %s", expand_string_message);
177 if (Ustrcmp(dkim_canon, "relaxed") == 0)
178 pdkim_canon = PDKIM_CANON_RELAXED;
179 else if (Ustrcmp(dkim_canon, "simple") == 0)
180 pdkim_canon = PDKIM_CANON_RELAXED;
182 log_write(0, LOG_MAIN, "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",dkim_canon);
183 pdkim_canon = PDKIM_CANON_RELAXED;
186 /* Expand signing headers once */
187 if (dkim_sign_headers != NULL) {
188 dkim_sign_headers = expand_string(dkim_sign_headers);
189 if (dkim_sign_headers == NULL) {
190 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
191 "dkim_sign_headers: %s", expand_string_message);
197 /* Get private key to use. */
198 dkim_private_key = expand_string(dkim_private_key);
199 if (dkim_private_key == NULL) {
200 log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
201 "dkim_private_key: %s", expand_string_message);
205 if ( (Ustrlen(dkim_private_key) == 0) ||
206 (Ustrcmp(dkim_private_key,"0") == 0) ||
207 (Ustrcmp(dkim_private_key,"false") == 0) ) {
208 /* don't sign, but no error */
213 if (dkim_private_key[0] == '/') {
215 /* Looks like a filename, load the private key. */
216 memset(big_buffer,0,big_buffer_size);
217 privkey_fd = open(CS dkim_private_key,O_RDONLY);
218 (void)read(privkey_fd,big_buffer,16383);
219 (void)close(privkey_fd);
220 dkim_private_key = big_buffer;
223 ctx = pdkim_init_sign(PDKIM_INPUT_SMTP,
224 (char *)dkim_signing_domain,
225 (char *)dkim_signing_selector,
226 (char *)dkim_private_key
229 pdkim_set_debug_stream(ctx,debug_file);
231 pdkim_set_optional(ctx,
232 (char *)dkim_sign_headers,
237 PDKIM_ALGO_RSA_SHA256,
241 while((sread = read(dkim_fd,&buf,4096)) > 0) {
242 if (pdkim_feed(ctx,buf,sread) != PDKIM_OK) {
247 /* Handle failed read above. */
249 debug_printf("DKIM: Error reading -K file.\n");
255 if (pdkim_feed_finish(ctx,&signature) != PDKIM_OK)
258 rc = store_get(strlen(signature->signature_header)+3);
259 Ustrcpy(rc,US signature->signature_header);
260 Ustrcat(rc,US"\r\n");
266 store_pool = old_pool;