X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/4c04137d73637107669e02b21f890387aaa2ef34..7832b9aa09dc312a137a1a56924d270085fad39e:/src/src/dkim.c

diff --git a/src/src/dkim.c b/src/src/dkim.c
index cc103c289..5c9d2279e 100644
--- a/src/src/dkim.c
+++ b/src/src/dkim.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) University of Cambridge, 1995 - 2016 */
+/* Copyright (c) University of Cambridge, 1995 - 2018 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Code for DKIM support. Other DKIM relevant code is in
@@ -12,57 +12,91 @@
 
 #ifndef DISABLE_DKIM
 
-#include "pdkim/pdkim.h"
+# include "pdkim/pdkim.h"
+
+# ifdef MACRO_PREDEF
+#  include "macro_predef.h"
+
+void
+params_dkim(void)
+{
+builtin_macro_create_var(US"_DKIM_SIGN_HEADERS", US PDKIM_DEFAULT_SIGN_HEADERS);
+}
+# else	/*!MACRO_PREDEF*/
+
+
+
+pdkim_ctx dkim_sign_ctx;
 
 int dkim_verify_oldpool;
 pdkim_ctx *dkim_verify_ctx = NULL;
-pdkim_signature *dkim_signatures = NULL;
 pdkim_signature *dkim_cur_sig = NULL;
+static const uschar * dkim_collect_error = NULL;
 
-static int
-dkim_exim_query_dns_txt(char *name, char *answer)
+#define DKIM_MAX_SIGNATURES 20
+
+
+
+/* Look up the DKIM record in DNS for the given hostname.
+Will use the first found if there are multiple.
+The return string is tainted, having come from off-site.
+*/
+
+uschar *
+dkim_exim_query_dns_txt(const uschar * name)
 {
-dns_answer dnsa;
+dns_answer * dnsa = store_get_dns_answer();
 dns_scan dnss;
-dns_record *rr;
+rmark reset_point = store_mark();
+gstring * g = NULL;
 
 lookup_dnssec_authenticated = NULL;
-if (dns_lookup(&dnsa, US name, T_TXT, NULL) != DNS_SUCCEED)
-  return PDKIM_FAIL;	/*XXX better error detail?  logging? */
+if (dns_lookup(dnsa, name, T_TXT, NULL) != DNS_SUCCEED)
+  return NULL;	/*XXX better error detail?  logging? */
 
 /* Search for TXT record */
 
-for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
+for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
      rr;
-     rr = dns_next_rr(&dnsa, &dnss, RESET_NEXT))
+     rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
   if (rr->type == T_TXT)
     {
     int rr_offset = 0;
-    int answer_offset = 0;
 
     /* Copy record content to the answer buffer */
 
     while (rr_offset < rr->size)
       {
       uschar len = rr->data[rr_offset++];
-      snprintf(answer + answer_offset,
-		PDKIM_DNS_TXT_MAX_RECLEN - answer_offset,
-		"%.*s", (int)len, (char *) (rr->data + rr_offset));
+
+      g = string_catn(g, US(rr->data + rr_offset), len);
+      if (g->ptr >= PDKIM_DNS_TXT_MAX_RECLEN)
+	goto bad;
+
       rr_offset += len;
-      answer_offset += len;
-      if (answer_offset >= PDKIM_DNS_TXT_MAX_RECLEN)
-	return PDKIM_FAIL;	/*XXX better error detail?  logging? */
       }
-    return PDKIM_OK;
+
+    /* check if this looks like a DKIM record */
+    if (Ustrncmp(g->s, "v=", 2) != 0 || strncasecmp(CS g->s, "v=dkim", 6) == 0)
+      {
+      gstring_release_unused(g);
+      return string_from_gstring(g);
+      }
+
+    if (g) g->ptr = 0;		/* overwrite previous record */
     }
 
-return PDKIM_FAIL;	/*XXX better error detail?  logging? */
+bad:
+store_reset(reset_point);
+return NULL;	/*XXX better error detail?  logging? */
 }
 
 
 void
 dkim_exim_init(void)
 {
+if (f.dkim_init_done) return;
+f.dkim_init_done = TRUE;
 pdkim_init();
 }
 
@@ -71,6 +105,8 @@ pdkim_init();
 void
 dkim_exim_verify_init(BOOL dot_stuffing)
 {
+dkim_exim_init();
+
 /* There is a store-reset between header & body reception
 so cannot use the main pool. Any allocs done by Exim
 memory-handling must use the perm pool. */
@@ -86,7 +122,8 @@ if (dkim_verify_ctx)
 /* Create new context */
 
 dkim_verify_ctx = pdkim_init_verify(&dkim_exim_query_dns_txt, dot_stuffing);
-dkim_collect_input = !!dkim_verify_ctx;
+dkim_collect_input = dkim_verify_ctx ? DKIM_MAX_SIGNATURES : 0;
+dkim_collect_error = NULL;
 
 /* Start feed up with any cached data */
 receive_get_cache();
@@ -102,213 +139,291 @@ int rc;
 
 store_pool = POOL_PERM;
 if (  dkim_collect_input
-   && (rc = pdkim_feed(dkim_verify_ctx, CS data, len)) != PDKIM_OK)
+   && (rc = pdkim_feed(dkim_verify_ctx, data, len)) != PDKIM_OK)
   {
+  dkim_collect_error = pdkim_errstr(rc);
   log_write(0, LOG_MAIN,
-	     "DKIM: validation error: %.100s", pdkim_errstr(rc));
-  dkim_collect_input = FALSE;
+	     "DKIM: validation error: %.100s", dkim_collect_error);
+  dkim_collect_input = 0;
   }
 store_pool = dkim_verify_oldpool;
 }
 
 
-void
-dkim_exim_verify_finish(void)
+/* Log the result for the given signature */
+static void
+dkim_exim_verify_log_sig(pdkim_signature * sig)
 {
-pdkim_signature *sig = NULL;
-int dkim_signers_size = 0;
-int dkim_signers_ptr = 0;
-dkim_signers = NULL;
-int rc;
-
-store_pool = POOL_PERM;
-
-/* Delete eventual previous signature chain */
-
-dkim_signatures = NULL;
-
-/* If we have arrived here with dkim_collect_input == FALSE, it
-means there was a processing error somewhere along the way.
-Log the incident and disable further verification. */
-
-if (!dkim_collect_input)
-  {
-  log_write(0, LOG_MAIN,
-	     "DKIM: Error while running this message through validation,"
-	     " disabling signature verification.");
-  dkim_disable_verify = TRUE;
-  goto out;
-  }
-
-dkim_collect_input = FALSE;
-
-/* Finish DKIM operation and fetch link to signatures chain */
-
-if ((rc = pdkim_feed_finish(dkim_verify_ctx, &dkim_signatures)) != PDKIM_OK)
-  {
-  log_write(0, LOG_MAIN,
-	     "DKIM: validation error: %.100s", pdkim_errstr(rc));
-  goto out;
+gstring * logmsg;
+uschar * s;
+
+if (!sig) return;
+
+/* Remember the domain for the first pass result */
+
+if (  !dkim_verify_overall
+   && dkim_verify_status
+      ? Ustrcmp(dkim_verify_status, US"pass") == 0
+      : sig->verify_status == PDKIM_VERIFY_PASS
+   )
+  dkim_verify_overall = string_copy(sig->domain);
+
+/* Rewrite the sig result if the ACL overrode it.  This is only
+needed because the DMARC code (sigh) peeks at the dkim sigs.
+Mark the sig for this having been done. */
+
+if (  dkim_verify_status
+   && (  dkim_verify_status != dkim_exim_expand_query(DKIM_VERIFY_STATUS)
+      || dkim_verify_reason != dkim_exim_expand_query(DKIM_VERIFY_REASON)
+   )  )
+  {			/* overridden by ACL */
+  sig->verify_ext_status = -1;
+  if (Ustrcmp(dkim_verify_status, US"fail") == 0)
+    sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_FAIL;
+  else if (Ustrcmp(dkim_verify_status, US"invalid") == 0)
+    sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_INVALID;
+  else if (Ustrcmp(dkim_verify_status, US"none") == 0)
+    sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_NONE;
+  else if (Ustrcmp(dkim_verify_status, US"pass") == 0)
+    sig->verify_status = PDKIM_VERIFY_POLICY | PDKIM_VERIFY_PASS;
+  else
+    sig->verify_status = -1;
   }
 
-for (sig = dkim_signatures; sig; sig = sig->next)
-  {
-  int size = 0;
-  int ptr = 0;
-
-  /* Log a line for each signature */
-
-  uschar *logmsg = string_append(NULL, &size, &ptr, 5,
-	string_sprintf("d=%s s=%s c=%s/%s a=%s b=%d ",
-	      sig->domain,
-	      sig->selector,
-	      sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed",
-	      sig->canon_body == PDKIM_CANON_SIMPLE ? "simple" : "relaxed",
-	      sig->algo == PDKIM_ALGO_RSA_SHA256
-	      ? "rsa-sha256"
-	      : sig->algo == PDKIM_ALGO_RSA_SHA1 ? "rsa-sha1" : "err",
-	      (int)sig->sigdata.len > -1 ? sig->sigdata.len * 8 : 0
-	      ),
-
-	sig->identity ? string_sprintf("i=%s ", sig->identity) : US"",
-	sig->created > 0 ? string_sprintf("t=%lu ", sig->created) : US"",
-	sig->expires > 0 ? string_sprintf("x=%lu ", sig->expires) : US"",
-	sig->bodylength > -1 ? string_sprintf("l=%lu ", sig->bodylength) : US""
-	);
-
+if (!LOGGING(dkim_verbose)) return;
+
+
+logmsg = string_catn(NULL, US"DKIM: ", 6);
+if (!(s = sig->domain)) s = US"<UNSET>";
+logmsg = string_append(logmsg, 2, "d=", s);
+if (!(s = sig->selector)) s = US"<UNSET>";
+logmsg = string_append(logmsg, 2, " s=", s);
+logmsg = string_fmt_append(logmsg, " c=%s/%s a=%s b=" SIZE_T_FMT,
+	  sig->canon_headers == PDKIM_CANON_SIMPLE ? "simple" : "relaxed",
+	  sig->canon_body    == PDKIM_CANON_SIMPLE ? "simple" : "relaxed",
+	  dkim_sig_to_a_tag(sig),
+	  (int)sig->sighash.len > -1 ? sig->sighash.len * 8 : (size_t)0);
+if ((s= sig->identity)) logmsg = string_append(logmsg, 2, " i=", s);
+if (sig->created > 0) logmsg = string_fmt_append(logmsg, " t=%lu",
+				    sig->created);
+if (sig->expires > 0) logmsg = string_fmt_append(logmsg, " x=%lu",
+				    sig->expires);
+if (sig->bodylength > -1) logmsg = string_fmt_append(logmsg, " l=%lu",
+				    sig->bodylength);
+
+if (sig->verify_status & PDKIM_VERIFY_POLICY)
+  logmsg = string_append(logmsg, 5,
+	    US" [", dkim_verify_status, US" - ", dkim_verify_reason, US"]");
+else
   switch (sig->verify_status)
     {
     case PDKIM_VERIFY_NONE:
-      logmsg = string_append(logmsg, &size, &ptr, 1, "[not verified]");
+      logmsg = string_cat(logmsg, US" [not verified]");
       break;
 
     case PDKIM_VERIFY_INVALID:
-      logmsg = string_append(logmsg, &size, &ptr, 1, "[invalid - ");
+      logmsg = string_cat(logmsg, US" [invalid - ");
       switch (sig->verify_ext_status)
 	{
 	case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
-	  logmsg = string_append(logmsg, &size, &ptr, 1,
-		        "public key record (currently?) unavailable]");
+	  logmsg = string_cat(logmsg,
+			US"public key record (currently?) unavailable]");
 	  break;
 
 	case PDKIM_VERIFY_INVALID_BUFFER_SIZE:
-	  logmsg = string_append(logmsg, &size, &ptr, 1,
-			"overlong public key record]");
+	  logmsg = string_cat(logmsg, US"overlong public key record]");
 	  break;
 
 	case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:
 	case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT:
-	  logmsg = string_append(logmsg, &size, &ptr, 1,
-		       "syntax error in public key record]");
+	  logmsg = string_cat(logmsg, US"syntax error in public key record]");
 	  break;
 
-        case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR:
-          logmsg = string_append(logmsg, &size, &ptr, 1,
-                       "signature tag missing or invalid]");
-          break;
+	case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR:
+	  logmsg = string_cat(logmsg, US"signature tag missing or invalid]");
+	  break;
 
-        case PDKIM_VERIFY_INVALID_DKIM_VERSION:
-          logmsg = string_append(logmsg, &size, &ptr, 1,
-                       "unsupported DKIM version]");
-          break;
+	case PDKIM_VERIFY_INVALID_DKIM_VERSION:
+	  logmsg = string_cat(logmsg, US"unsupported DKIM version]");
+	  break;
 
 	default:
-	  logmsg = string_append(logmsg, &size, &ptr, 1,
-			"unspecified problem]");
+	  logmsg = string_cat(logmsg, US"unspecified problem]");
 	}
       break;
 
     case PDKIM_VERIFY_FAIL:
-      logmsg =
-	string_append(logmsg, &size, &ptr, 1, "[verification failed - ");
+      logmsg = string_cat(logmsg, US" [verification failed - ");
       switch (sig->verify_ext_status)
 	{
 	case PDKIM_VERIFY_FAIL_BODY:
-	  logmsg = string_append(logmsg, &size, &ptr, 1,
-		       "body hash mismatch (body probably modified in transit)]");
+	  logmsg = string_cat(logmsg,
+	       US"body hash mismatch (body probably modified in transit)]");
 	  break;
 
 	case PDKIM_VERIFY_FAIL_MESSAGE:
-	  logmsg = string_append(logmsg, &size, &ptr, 1,
-		       "signature did not verify (headers probably modified in transit)]");
-	break;
+	  logmsg = string_cat(logmsg,
+		US"signature did not verify "
+		"(headers probably modified in transit)]");
+	  break;
 
 	default:
-	  logmsg = string_append(logmsg, &size, &ptr, 1, "unspecified reason]");
+	  logmsg = string_cat(logmsg, US"unspecified reason]");
 	}
       break;
 
     case PDKIM_VERIFY_PASS:
-      logmsg =
-	string_append(logmsg, &size, &ptr, 1, "[verification succeeded]");
+      logmsg = string_cat(logmsg, US" [verification succeeded]");
       break;
     }
 
-  logmsg[ptr] = '\0';
-  log_write(0, LOG_MAIN, "DKIM: %s", logmsg);
+log_write(0, LOG_MAIN, "%s", string_from_gstring(logmsg));
+return;
+}
+
+
+/* Log a line for each signature */
+void
+dkim_exim_verify_log_all(void)
+{
+for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next)
+  dkim_exim_verify_log_sig(sig);
+}
 
-  /* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */
 
-  dkim_signers = string_append(dkim_signers,
-				&dkim_signers_size,
-				&dkim_signers_ptr, 2, sig->domain, ":");
+void
+dkim_exim_verify_finish(void)
+{
+int rc;
+gstring * g = NULL;
+const uschar * errstr = NULL;
 
-  if (sig->identity)
-    dkim_signers = string_append(dkim_signers,
-				  &dkim_signers_size,
-				  &dkim_signers_ptr, 2, sig->identity, ":");
+store_pool = POOL_PERM;
 
-  /* Process next signature */
+/* Delete eventual previous signature chain */
+
+dkim_signers = NULL;
+dkim_signatures = NULL;
+
+if (dkim_collect_error)
+  {
+  log_write(0, LOG_MAIN,
+      "DKIM: Error during validation, disabling signature verification: %.100s",
+      dkim_collect_error);
+  f.dkim_disable_verify = TRUE;
+  goto out;
   }
 
-/* NULL-terminate and chop the last colon from the domain list */
+dkim_collect_input = 0;
 
-if (dkim_signers)
+/* Finish DKIM operation and fetch link to signatures chain */
+
+rc = pdkim_feed_finish(dkim_verify_ctx, (pdkim_signature **)&dkim_signatures,
+			&errstr);
+if (rc != PDKIM_OK && errstr)
+  log_write(0, LOG_MAIN, "DKIM: validation error: %s", errstr);
+
+/* Build a colon-separated list of signing domains (and identities, if present) in dkim_signers */
+
+for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next)
   {
-  dkim_signers[dkim_signers_ptr] = '\0';
-  if (Ustrlen(dkim_signers) > 0)
-  dkim_signers[Ustrlen(dkim_signers) - 1] = '\0';
+  if (sig->domain)   g = string_append_listele(g, ':', sig->domain);
+  if (sig->identity) g = string_append_listele(g, ':', sig->identity);
   }
 
+if (g) dkim_signers = g->s;
+
 out:
 store_pool = dkim_verify_oldpool;
 }
 
 
-void
-dkim_exim_acl_setup(uschar * id)
+
+/* Args as per dkim_exim_acl_run() below */
+static int
+dkim_acl_call(uschar * id, gstring ** res_ptr,
+  uschar ** user_msgptr, uschar ** log_msgptr)
+{
+int rc;
+DEBUG(D_receive)
+  debug_printf("calling acl_smtp_dkim for dkim_cur_signer='%s'\n", id);
+
+rc = acl_check(ACL_WHERE_DKIM, NULL, acl_smtp_dkim, user_msgptr, log_msgptr);
+dkim_exim_verify_log_sig(dkim_cur_sig);
+*res_ptr = string_append_listele(*res_ptr, ':', dkim_verify_status);
+return rc;
+}
+
+
+
+/* For the given identity, run the DKIM ACL once for each matching signature.
+
+Arguments
+ id		Identity to look for in dkim signatures
+ res_ptr	ptr to growable string-list of status results,
+		appended to per ACL run
+ user_msgptr	where to put a user error (for SMTP response)
+ log_msgptr	where to put a logging message (not for SMTP response)
+
+Returns:       OK         access is granted by an ACCEPT verb
+               DISCARD    access is granted by a DISCARD verb
+               FAIL       access is denied
+               FAIL_DROP  access is denied; drop the connection
+               DEFER      can't tell at the moment
+               ERROR      disaster
+*/
+
+int
+dkim_exim_acl_run(uschar * id, gstring ** res_ptr,
+  uschar ** user_msgptr, uschar ** log_msgptr)
 {
-pdkim_signature * sig;
 uschar * cmp_val;
+int rc = -1;
 
-dkim_cur_sig = NULL;
+dkim_verify_status = US"none";
+dkim_verify_reason = US"";
 dkim_cur_signer = id;
 
-if (dkim_disable_verify || !id || !dkim_verify_ctx)
-  return;
+if (f.dkim_disable_verify || !id || !dkim_verify_ctx)
+  return OK;
 
-/* Find signature to run ACL on */
+/* Find signatures to run ACL on */
 
-for (sig = dkim_signatures; sig; sig = sig->next)
+for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next)
   if (  (cmp_val = Ustrchr(id, '@') != NULL ? US sig->identity : US sig->domain)
      && strcmpic(cmp_val, id) == 0
      )
     {
-    dkim_cur_sig = sig;
-
     /* The "dkim_domain" and "dkim_selector" expansion variables have
-       related globals, since they are used in the signing code too.
-       Instead of inventing separate names for verification, we set
-       them here. This is easy since a domain and selector is guaranteed
-       to be in a signature. The other dkim_* expansion items are
-       dynamically fetched from dkim_cur_sig at expansion time (see
-       function below). */
+    related globals, since they are used in the signing code too.
+    Instead of inventing separate names for verification, we set
+    them here. This is easy since a domain and selector is guaranteed
+    to be in a signature. The other dkim_* expansion items are
+    dynamically fetched from dkim_cur_sig at expansion time (see
+    dkim_exim_expand_query() below). */
 
+    dkim_cur_sig = sig;
     dkim_signing_domain = US sig->domain;
     dkim_signing_selector = US sig->selector;
-    dkim_key_length = sig->sigdata.len * 8;
-    return;
+    dkim_key_length = sig->sighash.len * 8;
+
+    /* These two return static strings, so we can compare the addr
+    later to see if the ACL overwrote them.  Check that when logging */
+
+    dkim_verify_status = dkim_exim_expand_query(DKIM_VERIFY_STATUS);
+    dkim_verify_reason = dkim_exim_expand_query(DKIM_VERIFY_REASON);
+
+    if ((rc = dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr)) != OK)
+      return rc;
     }
+
+if (rc != -1)
+  return rc;
+
+/* No matching sig found.  Call ACL once anyway. */
+
+dkim_cur_sig = NULL;
+return dkim_acl_call(id, res_ptr, user_msgptr, log_msgptr);
 }
 
 
@@ -341,22 +456,17 @@ switch (what)
 uschar *
 dkim_exim_expand_query(int what)
 {
-if (!dkim_verify_ctx || dkim_disable_verify || !dkim_cur_sig)
+if (!dkim_verify_ctx || f.dkim_disable_verify || !dkim_cur_sig)
   return dkim_exim_expand_defaults(what);
 
 switch (what)
   {
   case DKIM_ALGO:
-    switch (dkim_cur_sig->algo)
-      {
-      case PDKIM_ALGO_RSA_SHA1:	return US"rsa-sha1";
-      case PDKIM_ALGO_RSA_SHA256:
-      default:			return US"rsa-sha256";
-      }
+    return dkim_sig_to_a_tag(dkim_cur_sig);
 
   case DKIM_BODYLENGTH:
     return dkim_cur_sig->bodylength >= 0
-      ? string_sprintf(OFF_T_FMT, (LONGLONG_T) dkim_cur_sig->bodylength)
+      ? string_sprintf("%ld", dkim_cur_sig->bodylength)
       : dkim_exim_expand_defaults(what);
 
   case DKIM_CANON_BODY:
@@ -368,12 +478,12 @@ switch (what)
       }
 
   case DKIM_CANON_HEADERS:
-  switch (dkim_cur_sig->canon_headers)
-    {
-    case PDKIM_CANON_RELAXED:	return US"relaxed";
-    case PDKIM_CANON_SIMPLE:
-    default:			return US"simple";
-    }
+    switch (dkim_cur_sig->canon_headers)
+      {
+      case PDKIM_CANON_RELAXED:	return US"relaxed";
+      case PDKIM_CANON_SIMPLE:
+      default:			return US"simple";
+      }
 
   case DKIM_COPIEDHEADERS:
     return dkim_cur_sig->copiedheaders
@@ -381,12 +491,12 @@ switch (what)
 
   case DKIM_CREATED:
     return dkim_cur_sig->created > 0
-      ? string_sprintf("%llu", dkim_cur_sig->created)
+      ? string_sprintf("%lu", dkim_cur_sig->created)
       : dkim_exim_expand_defaults(what);
 
   case DKIM_EXPIRES:
     return dkim_cur_sig->expires > 0
-      ? string_sprintf("%llu", dkim_cur_sig->expires)
+      ? string_sprintf("%lu", dkim_cur_sig->expires)
       : dkim_exim_expand_defaults(what);
 
   case DKIM_HEADERNAMES:
@@ -459,173 +569,195 @@ switch (what)
 }
 
 
-uschar *
-dkim_exim_sign(int dkim_fd, struct ob_dkim * dkim)
+void
+dkim_exim_sign_init(void)
 {
-const uschar * dkim_domain;
+int old_pool = store_pool;
+
+dkim_exim_init();
+store_pool = POOL_MAIN;
+pdkim_init_context(&dkim_sign_ctx, FALSE, &dkim_exim_query_dns_txt);
+store_pool = old_pool;
+}
+
+
+/* Generate signatures for the given file.
+If a prefix is given, prepend it to the file for the calculations.
+
+Return:
+  NULL:		error; error string written
+  string: 	signature header(s), or a zero-length string (not an error)
+*/
+
+gstring *
+dkim_exim_sign(int fd, off_t off, uschar * prefix,
+  struct ob_dkim * dkim, const uschar ** errstr)
+{
+const uschar * dkim_domain = NULL;
 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;
-uschar *sigbuf = NULL;
-int sigsize = 0;
-int sigptr = 0;
-pdkim_signature *signature;
-int pdkim_canon;
+gstring * seen_doms = NULL;
+pdkim_signature * sig;
+gstring * sigbuf;
 int pdkim_rc;
 int sread;
-char buf[4096];
+uschar buf[4096];
 int save_errno = 0;
 int old_pool = store_pool;
+uschar * errwhen;
+const uschar * s;
+
+if (dkim->dot_stuffed)
+  dkim_sign_ctx.flags |= PDKIM_DOT_TERM;
 
 store_pool = POOL_MAIN;
 
-if (!(dkim_domain = expand_cstring(dkim->dkim_domain)))
-  {
+if ((s = dkim->dkim_domain) && !(dkim_domain = expand_cstring(s)))
   /* expansion error, do not send message. */
-  log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand "
-	     "dkim_domain: %s", expand_string_message);
-  goto bad;
-  }
+  { errwhen = US"dkim_domain"; goto expand_bad; }
 
 /* Set $dkim_domain expansion variable to each unique domain in list. */
 
-while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep,
-				   itembuf, sizeof(itembuf))))
+if (dkim_domain)
+  while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 0)))
   {
-  if (!dkim_signing_domain || dkim_signing_domain[0] == '\0')
+  const uschar * dkim_sel;
+  int sel_sep = 0;
+
+  if (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)
-    {
-    const 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';
+  dkim_signing_domain = string_copylc(dkim_signing_domain);
+  if (match_isinlist(dkim_signing_domain, CUSS &seen_doms,
+      0, NULL, NULL, MCL_STRING, TRUE, NULL) == OK)
+    continue;
 
-  /* Set up $dkim_selector expansion variable. */
+  seen_doms = string_append_listele(seen_doms, ':', dkim_signing_domain);
 
-  if (!(dkim_signing_selector = expand_string(dkim->dkim_selector)))
-    {
-    log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand "
-	       "dkim_selector: %s", expand_string_message);
-    goto bad;
-    }
+  /* Set $dkim_selector expansion variable to each selector in list,
+  for this domain. */
 
-  /* Get canonicalization to use */
-
-  dkim_canon_expanded = dkim->dkim_canon
-    ? expand_string(dkim->dkim_canon) : US"relaxed";
-  if (!dkim_canon_expanded)
-    {
-    /* expansion error, do not send message. */
-    log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand "
-	       "dkim_canon: %s", expand_string_message);
-    goto bad;
-    }
+  if (!(dkim_sel = expand_string(dkim->dkim_selector)))
+    { errwhen = US"dkim_selector"; goto expand_bad; }
 
-  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
+  while ((dkim_signing_selector = string_nextinlist(&dkim_sel, &sel_sep,
+	  NULL, 0)))
     {
-    log_write(0, LOG_MAIN,
-	       "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",
-	       dkim_canon_expanded);
-    pdkim_canon = PDKIM_CANON_RELAXED;
-    }
-
-  dkim_sign_headers_expanded = NULL;
-  if (dkim->dkim_sign_headers)
-    if (!(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers)))
+    uschar * dkim_canon_expanded;
+    int pdkim_canon;
+    uschar * dkim_sign_headers_expanded = NULL;
+    uschar * dkim_private_key_expanded;
+    uschar * dkim_hash_expanded;
+    uschar * dkim_identity_expanded = NULL;
+    uschar * dkim_timestamps_expanded = NULL;
+    unsigned long tval = 0, xval = 0;
+
+    /* Get canonicalization to use */
+
+    dkim_canon_expanded = dkim->dkim_canon
+      ? expand_string(dkim->dkim_canon) : US"relaxed";
+    if (!dkim_canon_expanded)	/* expansion error, do not send message. */
+      { errwhen = US"dkim_canon"; goto expand_bad; }
+
+    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 | LOG_PANIC, "failed to expand "
-		 "dkim_sign_headers: %s", expand_string_message);
-      goto bad;
+      log_write(0, LOG_MAIN,
+		 "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",
+		 dkim_canon_expanded);
+      pdkim_canon = PDKIM_CANON_RELAXED;
       }
-    			/* else pass NULL, which means default header list */
 
-  /* Get private key to use. */
+    if (  dkim->dkim_sign_headers
+       && !(dkim_sign_headers_expanded = expand_string(dkim->dkim_sign_headers)))
+      { errwhen = US"dkim_sign_header"; goto expand_bad; }
+    /* else pass NULL, which means default header list */
 
-  if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key)))
-    {
-    log_write(0, LOG_MAIN | LOG_PANIC, "failed to expand "
-	       "dkim_private_key: %s", expand_string_message);
-    goto bad;
-    }
+    /* Get private key to use. */
 
-  if (  Ustrlen(dkim_private_key_expanded) == 0
-     || Ustrcmp(dkim_private_key_expanded, "0") == 0
-     || Ustrcmp(dkim_private_key_expanded, "false") == 0
-     )
-    continue;		/* don't sign, but no error */
+    if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key)))
+      { errwhen = US"dkim_private_key"; goto expand_bad; }
 
-  if (dkim_private_key_expanded[0] == '/')
-    {
-    int privkey_fd = 0;
+    if (  Ustrlen(dkim_private_key_expanded) == 0
+       || Ustrcmp(dkim_private_key_expanded, "0") == 0
+       || Ustrcmp(dkim_private_key_expanded, "false") == 0
+       )
+      continue;		/* don't sign, but no error */
 
-    /* Looks like a filename, load the private key. */
+    if (  dkim_private_key_expanded[0] == '/'
+       && !(dkim_private_key_expanded =
+	     expand_file_big_buffer(dkim_private_key_expanded)))
+      goto bad;
 
-    memset(big_buffer, 0, big_buffer_size);
+    if (!(dkim_hash_expanded = expand_string(dkim->dkim_hash)))
+      { errwhen = US"dkim_hash"; goto expand_bad; }
+
+    if (dkim->dkim_identity)
+      if (!(dkim_identity_expanded = expand_string(dkim->dkim_identity)))
+	{ errwhen = US"dkim_identity"; goto expand_bad; }
+      else if (!*dkim_identity_expanded)
+	dkim_identity_expanded = NULL;
+
+    if (dkim->dkim_timestamps)
+      if (!(dkim_timestamps_expanded = expand_string(dkim->dkim_timestamps)))
+	{ errwhen = US"dkim_timestamps"; goto expand_bad; }
+      else
+	xval = (tval = (unsigned long) time(NULL))
+	      + strtoul(CCS dkim_timestamps_expanded, NULL, 10);
+
+    if (!(sig = pdkim_init_sign(&dkim_sign_ctx, dkim_signing_domain,
+			  dkim_signing_selector,
+			  dkim_private_key_expanded,
+			  dkim_hash_expanded,
+			  errstr
+			  )))
+      goto bad;
+    dkim_private_key_expanded[0] = '\0';
 
-    if ((privkey_fd = open(CS dkim_private_key_expanded, O_RDONLY)) < 0)
-      {
-      log_write(0, LOG_MAIN | LOG_PANIC, "unable to open "
-		 "private key file for reading: %s",
-		 dkim_private_key_expanded);
+    pdkim_set_optional(sig,
+			CS dkim_sign_headers_expanded,
+			CS dkim_identity_expanded,
+			pdkim_canon,
+			pdkim_canon, -1, tval, xval);
+
+    if (!pdkim_set_sig_bodyhash(&dkim_sign_ctx, sig))
       goto bad;
-      }
 
-    if (read(privkey_fd, big_buffer, big_buffer_size - 2) < 0)
+    if (!dkim_sign_ctx.sig)		/* link sig to context chain */
+      dkim_sign_ctx.sig = sig;
+    else
       {
-      log_write(0, LOG_MAIN|LOG_PANIC, "unable to read private key file: %s",
-		 dkim_private_key_expanded);
-      goto bad;
+      pdkim_signature * n = dkim_sign_ctx.sig;
+      while (n->next) n = n->next;
+      n->next = sig;
       }
-
-    (void) close(privkey_fd);
-    dkim_private_key_expanded = big_buffer;
     }
+  }
 
-  ctx = pdkim_init_sign(CS dkim_signing_domain,
-			CS dkim_signing_selector,
-			CS dkim_private_key_expanded,
-			PDKIM_ALGO_RSA_SHA256,
-			dkim->dot_stuffed,
-			&dkim_exim_query_dns_txt
-			);
-  dkim_private_key_expanded[0] = '\0';
-  pdkim_set_optional(ctx,
-		      CS dkim_sign_headers_expanded,
-		      NULL,
-		      pdkim_canon,
-		      pdkim_canon, -1, 0, 0);
-
-  lseek(dkim_fd, 0, SEEK_SET);
-
-  while ((sread = read(dkim_fd, &buf, sizeof(buf))) > 0)
-    if ((pdkim_rc = pdkim_feed(ctx, buf, sread)) != PDKIM_OK)
-      goto pk_bad;
+/* We may need to carry on with the data-feed even if there are no DKIM sigs to
+produce, if some other package (eg. ARC) is signing. */
+
+if (!dkim_sign_ctx.sig && !dkim->force_bodyhash)
+  {
+  DEBUG(D_transport) debug_printf("DKIM: no viable signatures to use\n");
+  sigbuf = string_get(1);	/* return a zero-len string */
+  }
+else
+  {
+  if (prefix && (pdkim_rc = pdkim_feed(&dkim_sign_ctx, prefix, Ustrlen(prefix))) != PDKIM_OK)
+    goto pk_bad;
+
+  if (lseek(fd, off, SEEK_SET) < 0)
+    sread = -1;
+  else
+    while ((sread = read(fd, &buf, sizeof(buf))) > 0)
+      if ((pdkim_rc = pdkim_feed(&dkim_sign_ctx, buf, sread)) != PDKIM_OK)
+	goto pk_bad;
 
   /* Handle failed read above. */
   if (sread == -1)
@@ -635,37 +767,114 @@ while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep,
     goto bad;
     }
 
-  if ((pdkim_rc = pdkim_feed_finish(ctx, &signature)) != PDKIM_OK)
-    goto pk_bad;
-
-  sigbuf = string_append(sigbuf, &sigsize, &sigptr, 2,
-			  US signature->signature_header, US"\r\n");
+  /* Build string of headers, one per signature */
 
-  pdkim_free_ctx(ctx);
-  ctx = NULL;
-  }
+  if ((pdkim_rc = pdkim_feed_finish(&dkim_sign_ctx, &sig, errstr)) != PDKIM_OK)
+    goto pk_bad;
 
-if (sigbuf)
-  {
-  sigbuf[sigptr] = '\0';
-  rc = sigbuf;
+  if (!sig)
+    {
+    DEBUG(D_transport) debug_printf("DKIM: no signatures to use\n");
+    sigbuf = string_get(1);	/* return a zero-len string */
+    }
+  else for (sigbuf = NULL; sig; sig = sig->next)
+    sigbuf = string_append(sigbuf, 2, US sig->signature_header, US"\r\n");
   }
-else
-  rc = US"";
 
 CLEANUP:
-  if (ctx)
-    pdkim_free_ctx(ctx);
+  (void) string_from_gstring(sigbuf);
   store_pool = old_pool;
   errno = save_errno;
-  return rc;
+  return sigbuf;
 
 pk_bad:
   log_write(0, LOG_MAIN|LOG_PANIC,
-	       	"DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc));
+		"DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc));
 bad:
-  rc = NULL;
+  sigbuf = NULL;
   goto CLEANUP;
+
+expand_bad:
+  *errstr = string_sprintf("failed to expand %s: %s",
+              errwhen, expand_string_message);
+  log_write(0, LOG_MAIN | LOG_PANIC, "%s", *errstr);
+  goto bad;
 }
 
-#endif
+
+
+
+gstring *
+authres_dkim(gstring * g)
+{
+int start = 0;		/* compiler quietening */
+
+DEBUG(D_acl) start = g->ptr;
+
+for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next)
+  {
+  g = string_catn(g, US";\n\tdkim=", 8);
+
+  if (sig->verify_status & PDKIM_VERIFY_POLICY)
+    g = string_append(g, 5,
+      US"policy (", dkim_verify_status, US" - ", dkim_verify_reason, US")");
+  else switch(sig->verify_status)
+    {
+    case PDKIM_VERIFY_NONE:    g = string_cat(g, US"none"); break;
+    case PDKIM_VERIFY_INVALID:
+      switch (sig->verify_ext_status)
+	{
+	case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
+          g = string_cat(g, US"tmperror (pubkey unavailable)\n\t\t"); break;
+        case PDKIM_VERIFY_INVALID_BUFFER_SIZE:
+          g = string_cat(g, US"permerror (overlong public key record)\n\t\t"); break;
+        case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:
+        case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT:
+          g = string_cat(g, US"neutral (public key record import problem)\n\t\t");
+          break;
+        case PDKIM_VERIFY_INVALID_SIGNATURE_ERROR:
+          g = string_cat(g, US"neutral (signature tag missing or invalid)\n\t\t");
+          break;
+        case PDKIM_VERIFY_INVALID_DKIM_VERSION:
+          g = string_cat(g, US"neutral (unsupported DKIM version)\n\t\t");
+          break;
+        default:
+          g = string_cat(g, US"permerror (unspecified problem)\n\t\t"); break;
+	}
+      break;
+    case PDKIM_VERIFY_FAIL:
+      switch (sig->verify_ext_status)
+	{
+	case PDKIM_VERIFY_FAIL_BODY:
+          g = string_cat(g,
+	    US"fail (body hash mismatch; body probably modified in transit)\n\t\t");
+	  break;
+        case PDKIM_VERIFY_FAIL_MESSAGE:
+          g = string_cat(g,
+	    US"fail (signature did not verify; headers probably modified in transit)\n\t\t");
+	  break;
+        default:
+          g = string_cat(g, US"fail (unspecified reason)\n\t\t");
+	  break;
+	}
+      break;
+    case PDKIM_VERIFY_PASS:    g = string_cat(g, US"pass"); break;
+    default:                   g = string_cat(g, US"permerror"); break;
+    }
+  if (sig->domain)   g = string_append(g, 2, US" header.d=", sig->domain);
+  if (sig->identity) g = string_append(g, 2, US" header.i=", sig->identity);
+  if (sig->selector) g = string_append(g, 2, US" header.s=", sig->selector);
+  g = string_append(g, 2, US" header.a=", dkim_sig_to_a_tag(sig));
+  }
+
+DEBUG(D_acl)
+  if (g->ptr == start)
+    debug_printf("DKIM: no authres\n");
+  else
+    debug_printf("DKIM: authres '%.*s'\n", g->ptr - start - 3, g->s + start + 3);
+return g;
+}
+
+
+# endif	/*!MACRO_PREDEF*/
+#endif	/*!DISABLE_DKIM*/