Adding upstream version 4.94.2.upstream/4.94.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 891 insertions, 0 deletions

diff --git a/src/dkim.c b/src/dkim.c
new file mode 100644
index 0000000..92adb35
--- /dev/null
+++ b/src/dkim.c
@@ -0,0 +1,891 @@
+/*************************************************
+*     Exim - an Internet mail transport agent    *
+*************************************************/
+
+/* Copyright (c) University of Cambridge, 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 */
+/* See the file NOTICE for conditions of use and distribution. */
+
+/* Code for DKIM support. Other DKIM relevant code is in
+   receive.c, transport.c and transports/smtp.c */
+
+#include "exim.h"
+
+#ifndef DISABLE_DKIM
+
+# 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);
+builtin_macro_create_var(US"_DKIM_OVERSIGN_HEADERS", US PDKIM_OVERSIGN_HEADERS);
+}
+# else	/*!MACRO_PREDEF*/
+
+
+
+pdkim_ctx dkim_sign_ctx;
+
+int dkim_verify_oldpool;
+pdkim_ctx *dkim_verify_ctx = NULL;
+pdkim_signature *dkim_cur_sig = NULL;
+static const uschar * dkim_collect_error = NULL;
+
+#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 = store_get_dns_answer();
+dns_scan dnss;
+rmark reset_point = store_mark();
+gstring * g = NULL;
+
+lookup_dnssec_authenticated = NULL;
+if (dns_lookup(dnsa, name, T_TXT, NULL) != DNS_SUCCEED)
+  return NULL;	/*XXX better error detail?  logging? */
+
+/* Search for TXT record */
+
+for (dns_record * rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
+     rr;
+     rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+  if (rr->type == T_TXT)
+    {
+    int rr_offset = 0;
+
+    /* Copy record content to the answer buffer */
+
+    while (rr_offset < rr->size)
+      {
+      uschar len = 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;
+      }
+
+    /* 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 */
+    }
+
+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();
+}
+
+
+
+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. */
+
+dkim_verify_oldpool = store_pool;
+store_pool = POOL_PERM;
+
+/* Free previous context if there is one */
+
+if (dkim_verify_ctx)
+  pdkim_free_ctx(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_MAX_SIGNATURES : 0;
+dkim_collect_error = NULL;
+
+/* Start feed up with any cached data */
+receive_get_cache();
+
+store_pool = dkim_verify_oldpool;
+}
+
+
+void
+dkim_exim_verify_feed(uschar * data, int len)
+{
+int rc;
+
+store_pool = POOL_PERM;
+if (  dkim_collect_input
+   && (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", dkim_collect_error);
+  dkim_collect_input = 0;
+  }
+store_pool = dkim_verify_oldpool;
+}
+
+
+/* Log the result for the given signature */
+static void
+dkim_exim_verify_log_sig(pdkim_signature * sig)
+{
+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;
+  }
+
+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_cat(logmsg, US" [not verified]");
+      break;
+
+    case PDKIM_VERIFY_INVALID:
+      logmsg = string_cat(logmsg, US" [invalid - ");
+      switch (sig->verify_ext_status)
+	{
+	case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
+	  logmsg = string_cat(logmsg,
+			US"public key record (currently?) unavailable]");
+	  break;
+
+	case PDKIM_VERIFY_INVALID_BUFFER_SIZE:
+	  logmsg = string_cat(logmsg, US"overlong public key record]");
+	  break;
+
+	case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:
+	case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT:
+	  logmsg = string_cat(logmsg, US"syntax error in public key record]");
+	  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_cat(logmsg, US"unsupported DKIM version]");
+	  break;
+
+	default:
+	  logmsg = string_cat(logmsg, US"unspecified problem]");
+	}
+      break;
+
+    case PDKIM_VERIFY_FAIL:
+      logmsg = string_cat(logmsg, US" [verification failed - ");
+      switch (sig->verify_ext_status)
+	{
+	case PDKIM_VERIFY_FAIL_BODY:
+	  logmsg = string_cat(logmsg,
+	       US"body hash mismatch (body probably modified in transit)]");
+	  break;
+
+	case PDKIM_VERIFY_FAIL_MESSAGE:
+	  logmsg = string_cat(logmsg,
+		US"signature did not verify "
+		"(headers probably modified in transit)]");
+	  break;
+
+	case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE:
+	  logmsg = string_cat(logmsg,
+		US"signature invalid (key too short)]");
+	  break;
+
+	default:
+	  logmsg = string_cat(logmsg, US"unspecified reason]");
+	}
+      break;
+
+    case PDKIM_VERIFY_PASS:
+      logmsg = string_cat(logmsg, US" [verification succeeded]");
+      break;
+    }
+
+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);
+}
+
+
+void
+dkim_exim_verify_finish(void)
+{
+int rc;
+gstring * g = NULL;
+const uschar * errstr = NULL;
+
+store_pool = POOL_PERM;
+
+/* 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;
+  }
+
+dkim_collect_input = 0;
+
+/* 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)
+  {
+  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;
+}
+
+
+
+/* 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)
+{
+uschar * cmp_val;
+int rc = -1;
+
+dkim_verify_status = US"none";
+dkim_verify_reason = US"";
+dkim_cur_signer = id;
+
+if (f.dkim_disable_verify || !id || !dkim_verify_ctx)
+  return OK;
+
+/* Find signatures to run ACL on */
+
+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
+     )
+    {
+    /* 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
+    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->keybits;
+
+    /* 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);
+}
+
+
+static uschar *
+dkim_exim_expand_defaults(int what)
+{
+switch (what)
+  {
+  case DKIM_ALGO:		return US"";
+  case DKIM_BODYLENGTH:		return US"9999999999999";
+  case DKIM_CANON_BODY:		return US"";
+  case DKIM_CANON_HEADERS:	return US"";
+  case DKIM_COPIEDHEADERS:	return US"";
+  case DKIM_CREATED:		return US"0";
+  case DKIM_EXPIRES:		return US"9999999999999";
+  case DKIM_HEADERNAMES:	return US"";
+  case DKIM_IDENTITY:		return US"";
+  case DKIM_KEY_GRANULARITY:	return US"*";
+  case DKIM_KEY_SRVTYPE:	return US"*";
+  case DKIM_KEY_NOTES:		return US"";
+  case DKIM_KEY_TESTING:	return US"0";
+  case DKIM_NOSUBDOMAINS:	return US"0";
+  case DKIM_VERIFY_STATUS:	return US"none";
+  case DKIM_VERIFY_REASON:	return US"";
+  default:			return US"";
+  }
+}
+
+
+uschar *
+dkim_exim_expand_query(int what)
+{
+if (!dkim_verify_ctx || f.dkim_disable_verify || !dkim_cur_sig)
+  return dkim_exim_expand_defaults(what);
+
+switch (what)
+  {
+  case DKIM_ALGO:
+    return dkim_sig_to_a_tag(dkim_cur_sig);
+
+  case DKIM_BODYLENGTH:
+    return dkim_cur_sig->bodylength >= 0
+      ? string_sprintf("%ld", dkim_cur_sig->bodylength)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_CANON_BODY:
+    switch (dkim_cur_sig->canon_body)
+      {
+      case PDKIM_CANON_RELAXED:	return US"relaxed";
+      case PDKIM_CANON_SIMPLE:
+      default:			return US"simple";
+      }
+
+  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";
+      }
+
+  case DKIM_COPIEDHEADERS:
+    return dkim_cur_sig->copiedheaders
+      ? US dkim_cur_sig->copiedheaders : dkim_exim_expand_defaults(what);
+
+  case DKIM_CREATED:
+    return dkim_cur_sig->created > 0
+      ? string_sprintf("%lu", dkim_cur_sig->created)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_EXPIRES:
+    return dkim_cur_sig->expires > 0
+      ? string_sprintf("%lu", dkim_cur_sig->expires)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_HEADERNAMES:
+    return dkim_cur_sig->headernames
+      ? dkim_cur_sig->headernames : dkim_exim_expand_defaults(what);
+
+  case DKIM_IDENTITY:
+    return dkim_cur_sig->identity
+      ? US dkim_cur_sig->identity : dkim_exim_expand_defaults(what);
+
+  case DKIM_KEY_GRANULARITY:
+    return dkim_cur_sig->pubkey
+      ? dkim_cur_sig->pubkey->granularity
+      ? US dkim_cur_sig->pubkey->granularity
+      : dkim_exim_expand_defaults(what)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_KEY_SRVTYPE:
+    return dkim_cur_sig->pubkey
+      ? dkim_cur_sig->pubkey->srvtype
+      ? US dkim_cur_sig->pubkey->srvtype
+      : dkim_exim_expand_defaults(what)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_KEY_NOTES:
+    return dkim_cur_sig->pubkey
+      ? dkim_cur_sig->pubkey->notes
+      ? US dkim_cur_sig->pubkey->notes
+      : dkim_exim_expand_defaults(what)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_KEY_TESTING:
+    return dkim_cur_sig->pubkey
+      ? dkim_cur_sig->pubkey->testing
+      ? US"1"
+      : dkim_exim_expand_defaults(what)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_NOSUBDOMAINS:
+    return dkim_cur_sig->pubkey
+      ? dkim_cur_sig->pubkey->no_subdomaining
+      ? US"1"
+      : dkim_exim_expand_defaults(what)
+      : dkim_exim_expand_defaults(what);
+
+  case DKIM_VERIFY_STATUS:
+    switch (dkim_cur_sig->verify_status)
+      {
+      case PDKIM_VERIFY_INVALID:	return US"invalid";
+      case PDKIM_VERIFY_FAIL:		return US"fail";
+      case PDKIM_VERIFY_PASS:		return US"pass";
+      case PDKIM_VERIFY_NONE:
+      default:				return US"none";
+      }
+
+  case DKIM_VERIFY_REASON:
+    switch (dkim_cur_sig->verify_ext_status)
+      {
+      case PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE:
+						return US"pubkey_unavailable";
+      case PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD:return US"pubkey_dns_syntax";
+      case PDKIM_VERIFY_INVALID_PUBKEY_IMPORT:	return US"pubkey_der_syntax";
+      case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE:	return US"pubkey_too_short";
+      case PDKIM_VERIFY_FAIL_BODY:		return US"bodyhash_mismatch";
+      case PDKIM_VERIFY_FAIL_MESSAGE:		return US"signature_incorrect";
+      }
+
+  default:
+    return US"";
+  }
+}
+
+
+void
+dkim_exim_sign_init(void)
+{
+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;
+gstring * seen_doms = NULL;
+pdkim_signature * sig;
+gstring * sigbuf;
+int pdkim_rc;
+int sread;
+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 ((s = dkim->dkim_domain) && !(dkim_domain = expand_cstring(s)))
+  /* expansion error, do not send message. */
+  { errwhen = US"dkim_domain"; goto expand_bad; }
+
+/* Set $dkim_domain expansion variable to each unique domain in list. */
+
+if (dkim_domain)
+  while ((dkim_signing_domain = string_nextinlist(&dkim_domain, &sep, NULL, 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. */
+
+  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;
+
+  seen_doms = string_append_listele(seen_doms, ':', dkim_signing_domain);
+
+  /* Set $dkim_selector expansion variable to each selector in list,
+  for this domain. */
+
+  if (!(dkim_sel = expand_string(dkim->dkim_selector)))
+    { errwhen = US"dkim_selector"; goto expand_bad; }
+
+  while ((dkim_signing_selector = string_nextinlist(&dkim_sel, &sel_sep,
+	  NULL, 0)))
+    {
+    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,
+		 "DKIM: unknown canonicalization method '%s', defaulting to 'relaxed'.\n",
+		 dkim_canon_expanded);
+      pdkim_canon = PDKIM_CANON_RELAXED;
+      }
+
+    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 */
+
+    /* Get private key to use. */
+
+    if (!(dkim_private_key_expanded = expand_string(dkim->dkim_private_key)))
+      { errwhen = US"dkim_private_key"; goto expand_bad; }
+
+    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[0] == '/'
+       && !(dkim_private_key_expanded =
+	     expand_file_big_buffer(dkim_private_key_expanded)))
+      goto bad;
+
+    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';
+
+    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 (!dkim_sign_ctx.sig)		/* link sig to context chain */
+      dkim_sign_ctx.sig = sig;
+    else
+      {
+      pdkim_signature * n = dkim_sign_ctx.sig;
+      while (n->next) n = n->next;
+      n->next = sig;
+      }
+    }
+  }
+
+/* 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)
+    {
+    debug_printf("DKIM: Error reading -K file.\n");
+    save_errno = errno;
+    goto bad;
+    }
+
+  /* Build string of headers, one per signature */
+
+  if ((pdkim_rc = pdkim_feed_finish(&dkim_sign_ctx, &sig, errstr)) != PDKIM_OK)
+    goto pk_bad;
+
+  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");
+  }
+
+CLEANUP:
+  (void) string_from_gstring(sigbuf);
+  store_pool = old_pool;
+  errno = save_errno;
+  return sigbuf;
+
+pk_bad:
+  log_write(0, LOG_MAIN|LOG_PANIC,
+		"DKIM: signing failed: %.100s", pdkim_errstr(pdkim_rc));
+bad:
+  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;
+}
+
+
+
+
+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;
+        case PDKIM_VERIFY_INVALID_PUBKEY_KEYSIZE:	/* should this really be "polcy"? */
+          g = string_fmt_append(g, "fail (public key too short: %u bits)\n\t\t", sig->keybits);
+          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*/