Treat the transport option dkim_domain as a colon separated list, not

as a single string, and sign the message with each element, omitting
multiple occurences of the same signer.

The transport option dkim_domain should be renamed to dkim_add_signers.
The values of dkim_selector and dkim_private_key are expanded for
each signer available in $dkim_domain.  It is unclear if signatures
for domains that already signed the mail should be omitted and if we
need a new variable for signatures to omit or if it could be hardcoded,
but this question is independent of this patch.

1 files changed, 122 insertions, 101 deletions

diff --git a/src/src/dkim.c b/src/src/dkim.c
index e303776c2..d2abaff76 100644
--- a/src/src/dkim.c
+++ b/src/src/dkim.c
@@ -1,4 +1,4 @@
-/* $Cambridge: exim/src/src/dkim.c,v 1.11 2009/12/15 08:23:15 tom Exp $ */
+/* $Cambridge: exim/src/src/dkim.c,v 1.12 2010/02/18 12:09:15 michael Exp $ */
 
 /*************************************************
 *     Exim - an Internet mail transport agent    *
@@ -387,6 +387,14 @@ uschar *dkim_exim_sign(int dkim_fd,
                        uschar *dkim_selector,
                        uschar *dkim_canon,
                        uschar *dkim_sign_headers) {
+  int sep = 0;
+  uschar *seen_items = NULL;
+  int seen_items_size = 0;
+  int seen_items_offset = 0;
+  uschar itembuf[256];
+  uschar *dkim_canon_expanded;
+  uschar *dkim_sign_headers_expanded;
+  uschar *dkim_private_key_expanded;
   pdkim_ctx *ctx = NULL;
   uschar *rc = NULL;
   pdkim_signature *signature;
@@ -405,127 +413,140 @@ uschar *dkim_exim_sign(int dkim_fd,
     rc = NULL;
     goto CLEANUP;
   }
-  /* Set up $dkim_domain expansion variable. */
-  dkim_signing_domain = dkim_domain;
 
-  /* Get selector to use. */
-  dkim_selector = expand_string(dkim_selector);
-  if (dkim_selector == NULL) {
-    log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
-      "dkim_selector: %s", expand_string_message);
-    rc = NULL;
-    goto CLEANUP;
-  }
-  /* Set up $dkim_selector expansion variable. */
-  dkim_signing_selector = dkim_selector;
+  /* Set $dkim_domain expansion variable to each unique domain in list. */
+  while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep,
+                                                  itembuf,
+                                                  sizeof(itembuf))) != NULL) {
+    if (!dkim_signing_domain || (dkim_signing_domain[0] == '\0')) continue;
+    /* Only sign once for each domain, no matter how often it
+       appears in the expanded list. */
+    if (seen_items != NULL) {
+      uschar *seen_items_list = seen_items;
+      if (match_isinlist(dkim_signing_domain,
+                         &seen_items_list,0,NULL,NULL,MCL_STRING,TRUE,NULL) == OK)
+        continue;
+      seen_items = string_append(seen_items,&seen_items_size,&seen_items_offset,1,":");
+    }
+    seen_items = string_append(seen_items,&seen_items_size,&seen_items_offset,1,dkim_signing_domain);
+    seen_items[seen_items_offset] = '\0';
 
-  /* Get canonicalization to use */
-  dkim_canon = expand_string(dkim_canon?dkim_canon:US"relaxed");
-  if (dkim_canon == NULL) {
-    /* expansion error, do not send message. */
-    log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
-          "dkim_canon: %s", expand_string_message);
-    rc = NULL;
-    goto CLEANUP;
-  }
-  if (Ustrcmp(dkim_canon, "relaxed") == 0)
-    pdkim_canon = PDKIM_CANON_RELAXED;
-  else if (Ustrcmp(dkim_canon, "simple") == 0)
-    pdkim_canon = PDKIM_CANON_SIMPLE;
-  else {
-    log_write(0, LOG_MAIN, "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",dkim_canon);
-    pdkim_canon = PDKIM_CANON_RELAXED;
-  }
+    /* Set up $dkim_selector expansion variable. */
+    dkim_signing_selector = expand_string(dkim_selector);
+    if (dkim_signing_selector == NULL) {
+      log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
+                "dkim_selector: %s", expand_string_message);
+      rc = NULL;
+      goto CLEANUP;
+    }
 
-  /* Expand signing headers once */
-  if (dkim_sign_headers != NULL) {
-    dkim_sign_headers = expand_string(dkim_sign_headers);
-    if (dkim_sign_headers == NULL) {
+    /* Get canonicalization to use */
+    dkim_canon_expanded = expand_string(dkim_canon?dkim_canon:US"relaxed");
+    if (dkim_canon_expanded == NULL) {
+      /* expansion error, do not send message. */
       log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
-        "dkim_sign_headers: %s", expand_string_message);
+                "dkim_canon: %s", expand_string_message);
       rc = NULL;
       goto CLEANUP;
     }
-  }
+    if (Ustrcmp(dkim_canon_expanded, "relaxed") == 0)
+      pdkim_canon = PDKIM_CANON_RELAXED;
+    else if (Ustrcmp(dkim_canon_expanded, "simple") == 0)
+      pdkim_canon = PDKIM_CANON_SIMPLE;
+    else {
+      log_write(0, LOG_MAIN, "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",dkim_canon_expanded);
+      pdkim_canon = PDKIM_CANON_RELAXED;
+    }
 
-  /* Get private key to use. */
-  dkim_private_key = expand_string(dkim_private_key);
-  if (dkim_private_key == NULL) {
-    log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
-      "dkim_private_key: %s", expand_string_message);
-    rc = NULL;
-    goto CLEANUP;
-  }
-  if ( (Ustrlen(dkim_private_key) == 0) ||
-       (Ustrcmp(dkim_private_key,"0") == 0) ||
-       (Ustrcmp(dkim_private_key,"false") == 0) ) {
-    /* don't sign, but no error */
-    rc = US"";
-    goto CLEANUP;
-  }
+    dkim_sign_headers_expanded = expand_string(dkim_sign_headers);
+    if (dkim_sign_headers_expanded == NULL) {
+      log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
+                "dkim_sign_headers: %s", expand_string_message);
+      rc = NULL;
+      goto CLEANUP;
+    }
 
-  if (dkim_private_key[0] == '/') {
-    int privkey_fd = 0;
-    /* Looks like a filename, load the private key. */
-    memset(big_buffer,0,big_buffer_size);
-    privkey_fd = open(CS dkim_private_key,O_RDONLY);
-    if (privkey_fd < 0) {
-      log_write(0, LOG_MAIN|LOG_PANIC, "unable to open "
-        "private key file for reading: %s", dkim_private_key);
+    /* Get private key to use. */
+    dkim_private_key_expanded = expand_string(dkim_private_key);
+    if (dkim_private_key_expanded == NULL) {
+      log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
+                "dkim_private_key: %s", expand_string_message);
       rc = NULL;
       goto CLEANUP;
     }
-    (void)read(privkey_fd,big_buffer,(big_buffer_size-2));
-    (void)close(privkey_fd);
-    dkim_private_key = big_buffer;
-  }
+    if ( (Ustrlen(dkim_private_key_expanded) == 0) ||
+         (Ustrcmp(dkim_private_key_expanded,"0") == 0) ||
+         (Ustrcmp(dkim_private_key_expanded,"false") == 0) ) {
+      /* don't sign, but no error */
+      rc = US"";
+      goto CLEANUP;
+    }
+
+    if (dkim_private_key_expanded[0] == '/') {
+      int privkey_fd = 0;
+      /* Looks like a filename, load the private key. */
+      memset(big_buffer,0,big_buffer_size);
+      privkey_fd = open(CS dkim_private_key_expanded,O_RDONLY);
+      if (privkey_fd < 0) {
+        log_write(0, LOG_MAIN|LOG_PANIC, "unable to open "
+                  "private key file for reading: %s", dkim_private_key_expanded);
+        rc = NULL;
+        goto CLEANUP;
+      }
+      (void)read(privkey_fd,big_buffer,(big_buffer_size-2));
+      (void)close(privkey_fd);
+      dkim_private_key_expanded = big_buffer;
+    }
 
-  ctx = pdkim_init_sign(PDKIM_INPUT_SMTP,
-                        (char *)dkim_signing_domain,
-                        (char *)dkim_signing_selector,
-                        (char *)dkim_private_key
-                       );
-
-  pdkim_set_debug_stream(ctx,debug_file);
-
-  pdkim_set_optional(ctx,
-                     (char *)dkim_sign_headers,
-                     NULL,
-                     pdkim_canon,
-                     pdkim_canon,
-                     -1,
-                     PDKIM_ALGO_RSA_SHA256,
-                     0,
-                     0);
-
-  while((sread = read(dkim_fd,&buf,4096)) > 0) {
-    if (pdkim_feed(ctx,buf,sread) != PDKIM_OK) {
+    ctx = pdkim_init_sign(PDKIM_INPUT_SMTP,
+                          (char *)dkim_signing_domain,
+                          (char *)dkim_signing_selector,
+                          (char *)dkim_private_key_expanded
+                         );
+
+    pdkim_set_debug_stream(ctx,debug_file);
+
+    pdkim_set_optional(ctx,
+                       (char *)dkim_sign_headers_expanded,
+                       NULL,
+                       pdkim_canon,
+                       pdkim_canon,
+                       -1,
+                       PDKIM_ALGO_RSA_SHA256,
+                       0,
+                       0);
+
+    while((sread = read(dkim_fd,&buf,4096)) > 0) {
+      if (pdkim_feed(ctx,buf,sread) != PDKIM_OK) {
+        rc = NULL;
+        goto CLEANUP;
+      }
+    }
+    /* Handle failed read above. */
+    if (sread == -1) {
+      debug_printf("DKIM: Error reading -K file.\n");
+      save_errno = errno;
       rc = NULL;
       goto CLEANUP;
     }
-  }
-  /* Handle failed read above. */
-  if (sread == -1) {
-    debug_printf("DKIM: Error reading -K file.\n");
-    save_errno = errno;
-    rc = NULL;
-    goto CLEANUP;
-  }
 
-  pdkim_rc = pdkim_feed_finish(ctx,&signature);
-  if (pdkim_rc != PDKIM_OK) {
-    log_write(0, LOG_MAIN|LOG_PANIC, "DKIM: signing failed (RC %d)", pdkim_rc);
-    goto CLEANUP;
-  }
+    pdkim_rc = pdkim_feed_finish(ctx,&signature);
+    if (pdkim_rc != PDKIM_OK) {
+      log_write(0, LOG_MAIN|LOG_PANIC, "DKIM: signing failed (RC %d)", pdkim_rc);
+      goto CLEANUP;
+    }
 
-  rc = store_get(strlen(signature->signature_header)+3);
-  Ustrcpy(rc,US signature->signature_header);
-  Ustrcat(rc,US"\r\n");
+    rc = store_get(strlen(signature->signature_header)+3);
+    Ustrcpy(rc,US signature->signature_header);
+    Ustrcat(rc,US"\r\n");
 
-  CLEANUP:
-  if (ctx != NULL) {
     pdkim_free_ctx(ctx);
+    ctx = NULL;
   }
+
+  CLEANUP:
+  if (ctx != NULL)
+    pdkim_free_ctx(ctx);
   store_pool = old_pool;
   errno = save_errno;
   return rc;