X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/c3d43245c842965fed6a9153f9c6e9e8be326b7c..30795c5e77e21e90f3c695e6274bc9b4a9b68900:/src/src/arc.c

diff --git a/src/src/arc.c b/src/src/arc.c
index dedf64c44..b7fcb116a 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -21,6 +21,11 @@
 extern pdkim_ctx * dkim_verify_ctx;
 extern pdkim_ctx dkim_sign_ctx;
 
+#define ARC_SIGN_OPT_TSTAMP	BIT(0)
+#define ARC_SIGN_OPT_EXPIRE	BIT(1)
+
+#define ARC_SIGN_DEFAULT_EXPIRE_DELTA (60 * 60 * 24 * 30)	/* one month */
+
 /******************************************************************************/
 
 typedef struct hdr_rlist {
@@ -84,8 +89,11 @@ typedef struct arc_ctx {
 #define HDR_AR		US"Authentication-Results:"
 #define HDRLEN_AR	23
 
+static time_t now;
+static time_t expire;
 static hdr_rlist * headers_rlist;
 static arc_ctx arc_sign_ctx = { NULL };
+static arc_ctx arc_verify_ctx = { NULL };
 
 
 /******************************************************************************/
@@ -135,7 +143,7 @@ for (pas = &ctx->arcset_chain, prev = NULL, next = ctx->arcset_chain;
   }
 
 DEBUG(D_acl) debug_printf("ARC: new instance %u\n", i);
-*pas = as = store_get(sizeof(arc_set));
+*pas = as = store_get(sizeof(arc_set), FALSE);
 memset(as, 0, sizeof(arc_set));
 as->next = next;
 as->prev = prev;
@@ -193,7 +201,7 @@ al->complete = h;
 
 if (!instance_only)
   {
-  al->rawsig_no_b_val.data = store_get(h->slen + 1);
+  al->rawsig_no_b_val.data = store_get(h->slen + 1, TRUE);	/* tainted */
   memcpy(al->rawsig_no_b_val.data, h->text, off);	/* copy the header name blind */
   r = al->rawsig_no_b_val.data + off;
   al->rawsig_no_b_val.len = off;
@@ -252,9 +260,10 @@ while ((c = *s))
 	  while ((c = *++s) && c != ';')
 	    if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
 	      g = string_catn(g, s, 1);
+	  if (!g) return US"no b= value";
 	  al->b.data = string_from_gstring(g);
 	  al->b.len = g->ptr;
-	  gstring_reset_unused(g);
+	  gstring_release_unused(g);
 	  bend = s;
 	  break;
 	case 'h':			/* bh= AMS body hash */
@@ -268,9 +277,10 @@ while ((c = *s))
 	  while ((c = *++s) && c != ';')
 	    if (c != ' ' && c != '\t' && c != '\n' && c != '\r')
 	      g = string_catn(g, s, 1);
+	  if (!g) return US"no bh= value";
 	  al->bh.data = string_from_gstring(g);
 	  al->bh.len = g->ptr;
-	  gstring_reset_unused(g);
+	  gstring_release_unused(g);
 	  break;
 	default:
 	  return US"b? tag";
@@ -375,9 +385,9 @@ static uschar *
 arc_insert_hdr(arc_ctx * ctx, header_line * h, unsigned off, unsigned hoff,
   BOOL instance_only)
 {
-int i;
+unsigned i;
 arc_set * as;
-arc_line * al = store_get(sizeof(arc_line)), ** alp;
+arc_line * al = store_get(sizeof(arc_line), FALSE), ** alp;
 uschar * e;
 
 memset(al, 0, sizeof(arc_line));
@@ -388,6 +398,7 @@ if ((e = arc_parse_line(al, h, off, instance_only)))
   return US"line parse";
   }
 if (!(i = arc_instance_from_hdr(al)))	return US"instance find";
+if (i > 50)				return US"overlarge instance number";
 if (!(as = arc_find_set(ctx, i)))	return US"set find";
 if (*(alp = (arc_line **)(US as + hoff))) return US"dup hdr";
 
@@ -488,7 +499,7 @@ const uschar * e;
 DEBUG(D_acl) debug_printf("ARC: collecting arc sets\n");
 for (h = header_list; h; h = h->next)
   {
-  r = store_get(sizeof(hdr_rlist));
+  r = store_get(sizeof(hdr_rlist), FALSE);
   r->prev = rprev;
   r->used = FALSE;
   r->h = h;
@@ -533,7 +544,8 @@ hctx hhash_ctx;
 const uschar * s;
 int len;
 
-if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
+if (  hashtype == -1
+   || !exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
   {
   DEBUG(D_acl)
       debug_printf("ARC: hash setup error, possibly nonhandled hashtype\n");
@@ -588,7 +600,7 @@ uschar * dns_txt;
 pdkim_pubkey * p;
 
 if (!(dns_txt = dkim_exim_query_dns_txt(string_sprintf("%.*s._domainkey.%.*s",
-	  al->s.len, al->s.data, al->d.len, al->d.data))))
+	  (int)al->s.len, al->s.data, (int)al->d.len, al->d.data))))
   {
   DEBUG(D_acl) debug_printf("pubkey dns lookup fail\n");
   return NULL;
@@ -628,7 +640,7 @@ return p;
 static pdkim_bodyhash *
 arc_ams_setup_vfy_bodyhash(arc_line * ams)
 {
-int canon_head, canon_body;
+int canon_head = -1, canon_body = -1;
 long bodylen;
 
 if (!ams->c.data) ams->c.data = US"simple";	/* RFC 6376 (DKIM) default */
@@ -734,6 +746,11 @@ if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
   }
 
 hashtype = pdkim_hashname_to_hashtype(ams->a_hash.data, ams->a_hash.len);
+if (hashtype == -1)
+  {
+  DEBUG(D_acl) debug_printf("ARC i=%d AMS verify bad a_hash\n", as->instance);
+  return as->ams_verify_done = arc_state_reason = US"AMS sig nonverify";
+  }
 
 if ((errstr = exim_dkim_verify(&vctx,
 	  pdkim_hashes[hashtype].exim_hashmethod, &hhash, &sighash)))
@@ -760,24 +777,26 @@ arc_headers_check(arc_ctx * ctx)
 arc_set * as;
 int inst;
 BOOL ams_fail_found = FALSE;
-uschar * ret = NULL;
 
-if (!(as = ctx->arcset_chain))
+if (!(as = ctx->arcset_chain_last))
   return US"none";
 
-for(inst = 0; as; as = as->next)
+for(inst = as->instance; as; as = as->prev, inst--)
   {
-  if (  as->instance != ++inst
-     || !as->hdr_aar || !as->hdr_ams || !as->hdr_as
-     || arc_cv_match(as->hdr_as, US"fail")
-     )
-    {
-    arc_state_reason = string_sprintf("i=%d"
-      " (cv, sequence or missing header)", as->instance);
-    DEBUG(D_acl) debug_printf("ARC chain fail at %s\n", arc_state_reason);
-    return US"fail";
-    }
+  if (as->instance != inst)
+    arc_state_reason = string_sprintf("i=%d (sequence; expected %d)",
+      as->instance, inst);
+  else if (!as->hdr_aar || !as->hdr_ams || !as->hdr_as)
+    arc_state_reason = string_sprintf("i=%d (missing header)", as->instance);
+  else if (arc_cv_match(as->hdr_as, US"fail"))
+    arc_state_reason = string_sprintf("i=%d (cv)", as->instance);
+  else
+    goto good;
+
+  DEBUG(D_acl) debug_printf("ARC chain fail at %s\n", arc_state_reason);
+  return US"fail";
 
+  good:
   /* Evaluate the oldest-pass AMS validation while we're here.
   It does not affect the AS chain validation but is reported as
   auxilary info. */
@@ -789,23 +808,29 @@ for(inst = 0; as; as = as->next)
       arc_oldest_pass = inst;
   arc_state_reason = NULL;
   }
+if (inst != 0)
+  {
+  arc_state_reason = string_sprintf("(sequence; expected i=%d)", inst);
+  DEBUG(D_acl) debug_printf("ARC chain fail %s\n", arc_state_reason);
+  return US"fail";
+  }
 
 arc_received = ctx->arcset_chain_last;
-arc_received_instance = inst;
-if (ret)
-  return ret;
+arc_received_instance = arc_received->instance;
 
 /* We can skip the latest-AMS validation, if we already did it. */
 
 as = ctx->arcset_chain_last;
-if (as->ams_verify_done && !as->ams_verify_passed)
+if (!as->ams_verify_passed)
   {
-  arc_state_reason = as->ams_verify_done;
-  return US"fail";
+  if (as->ams_verify_done)
+    {
+    arc_state_reason = as->ams_verify_done;
+    return US"fail";
+    }
+  if (!!arc_ams_verify(ctx, as))
+    return US"fail";
   }
-if (!!arc_ams_verify(ctx, as))
-  return US"fail";
-
 return NULL;
 }
 
@@ -852,7 +877,8 @@ if (  as->instance == 1 && !arc_cv_match(hdr_as, US"none")
 
 hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
 
-if (!exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
+if (  hashtype == -1
+   || !exim_sha_init(&hhash_ctx, pdkim_hashes[hashtype].exim_hashmethod))
   {
   DEBUG(D_acl)
       debug_printf("ARC: hash setup error, possibly nonhandled hashtype\n");
@@ -947,8 +973,6 @@ if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
   return US"fail";
   }
 
-hashtype = pdkim_hashname_to_hashtype(hdr_as->a_hash.data, hdr_as->a_hash.len);
-
 if ((errstr = exim_dkim_verify(&vctx,
 	      pdkim_hashes[hashtype].exim_hashmethod,
 	      &hhash_computed, &sighash)))
@@ -967,16 +991,13 @@ return NULL;
 static const uschar *
 arc_verify_seals(arc_ctx * ctx)
 {
-arc_set * as = ctx->arcset_chain;
+arc_set * as = ctx->arcset_chain_last;
 
 if (!as)
   return US"none";
 
-while (as)
-  {
-  if (arc_seal_verify(ctx, as)) return US"fail";
-  as = as->next;
-  }
+for ( ; as; as = as->prev) if (arc_seal_verify(ctx, as)) return US"fail";
+
 DEBUG(D_acl) debug_printf("ARC: AS vfy overall pass\n");
 return NULL;
 }
@@ -991,9 +1012,10 @@ Return:  The ARC state, or NULL on error.
 const uschar *
 acl_verify_arc(void)
 {
-arc_ctx ctx = { NULL };
 const uschar * res;
 
+memset(&arc_verify_ctx, 0, sizeof(arc_verify_ctx));
+
 if (!dkim_verify_ctx)
   {
   DEBUG(D_acl) debug_printf("ARC: no DKIM verify context\n");
@@ -1007,7 +1029,7 @@ https://tools.ietf.org/html/draft-ietf-dmarc-arc-protocol-10#section-6
        none, the ARC state is "none" and the algorithm stops here.
 */
 
-if ((res = arc_vfy_collect_hdrs(&ctx)))
+if ((res = arc_vfy_collect_hdrs(&arc_verify_ctx)))
   goto out;
 
 /* 2.  If the form of any ARC set is invalid (e.g., does not contain
@@ -1025,7 +1047,7 @@ if ((res = arc_vfy_collect_hdrs(&ctx)))
        then the chain state is "fail" and the algorithm stops here.
 */
 
-if ((res = arc_headers_check(&ctx)))
+if ((res = arc_headers_check(&arc_verify_ctx)))
   goto out;
 
 /* 4.  For each ARC-Seal from the "N"th instance to the first, apply the
@@ -1067,7 +1089,7 @@ if ((res = arc_headers_check(&ctx)))
        the algorithm is complete.
 */
 
-if ((res = arc_verify_seals(&ctx)))
+if ((res = arc_verify_seals(&arc_verify_ctx)))
   goto out;
 
 res = US"pass";
@@ -1083,7 +1105,7 @@ out:
 static hdr_rlist *
 arc_rlist_entry(hdr_rlist * list, const uschar * s, int len)
 {
-hdr_rlist * r = store_get(sizeof(hdr_rlist) + sizeof(header_line));
+hdr_rlist * r = store_get(sizeof(hdr_rlist) + sizeof(header_line), FALSE);
 header_line * h = r->h = (header_line *)(r+1);
 
 r->prev = list;
@@ -1174,12 +1196,13 @@ arc_sign_append_aar(gstring * g, arc_ctx * ctx,
   const uschar * identity, int instance, blob * ar)
 {
 int aar_off = g ? g->ptr : 0;
-arc_set * as = store_get(sizeof(arc_set) + sizeof(arc_line) + sizeof(header_line));
+arc_set * as =
+  store_get(sizeof(arc_set) + sizeof(arc_line) + sizeof(header_line), FALSE);
 arc_line * al = (arc_line *)(as+1);
 header_line * h = (header_line *)(al+1);
 
 g = string_catn(g, ARC_HDR_AAR, ARC_HDRLEN_AAR);
-g = string_cat(g, string_sprintf(" i=%d; %s;\r\n\t", instance, identity));
+g = string_fmt_append(g, " i=%d; %s;\r\n\t", instance, identity);
 g = string_catn(g, US ar->data, ar->len);
 
 h->slen = g->ptr - aar_off;
@@ -1240,6 +1263,9 @@ if (  (errstr = exim_dkim_signing_init(privkey, &sctx))
    || (errstr = exim_dkim_sign(&sctx, hm, &hhash, sig)))
   {
   log_write(0, LOG_MAIN, "ARC: %s signing: %s\n", why, errstr);
+  DEBUG(D_transport)
+    debug_printf("private key, or private-key file content, was: '%s'\n",
+      privkey);
   return FALSE;
   }
 return TRUE;
@@ -1262,7 +1288,7 @@ for (;;)
   g = string_catn(g, US"\r\n\t  ", 5);
   }
 g = string_catn(g, US";\r\n", 3);
-gstring_reset_unused(g);
+gstring_release_unused(g);
 string_from_gstring(g);
 return g;
 }
@@ -1273,7 +1299,7 @@ return g;
 static gstring *
 arc_sign_append_ams(gstring * g, arc_ctx * ctx, int instance,
   const uschar * identity, const uschar * selector, blob * bodyhash,
-  hdr_rlist * rheaders, const uschar * privkey)
+  hdr_rlist * rheaders, const uschar * privkey, unsigned options)
 {
 uschar * s;
 gstring * hdata = NULL;
@@ -1281,7 +1307,7 @@ int col;
 int hashtype = pdkim_hashname_to_hashtype(US"sha256", 6);	/*XXX hardwired */
 blob sig;
 int ams_off;
-arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line));
+arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line), FALSE);
 header_line * h = (header_line *)(al+1);
 
 /* debug_printf("%s\n", __FUNCTION__); */
@@ -1289,13 +1315,14 @@ header_line * h = (header_line *)(al+1);
 /* Construct the to-be-signed AMS pseudo-header: everything but the sig. */
 
 ams_off = g->ptr;
-g = string_append(g, 10,
-      ARC_HDR_AMS,
-      US" i=", string_sprintf("%d", instance),
-      US"; a=rsa-sha256; c=relaxed; d=", identity,		/*XXX hardwired */
-      US"; s=", selector,
-      US";\r\n\tbh=", pdkim_encode_base64(bodyhash),
-      US";\r\n\th=");
+g = string_fmt_append(g, "%s i=%d; a=rsa-sha256; c=relaxed; d=%s; s=%s",
+      ARC_HDR_AMS, instance, identity, selector);	/*XXX hardwired a= */
+if (options & ARC_SIGN_OPT_TSTAMP)
+  g = string_fmt_append(g, "; t=%lu", (u_long)now);
+if (options & ARC_SIGN_OPT_EXPIRE)
+  g = string_fmt_append(g, "; x=%lu", (u_long)expire);
+g = string_fmt_append(g, ";\r\n\tbh=%s;\r\n\th=",
+      pdkim_encode_base64(bodyhash));
 
 for(col = 3; rheaders; rheaders = rheaders->prev)
   {
@@ -1391,12 +1418,12 @@ return US"none";
 static gstring *
 arc_sign_prepend_as(gstring * arcset_interim, arc_ctx * ctx,
   int instance, const uschar * identity, const uschar * selector, blob * ar,
-  const uschar * privkey)
+  const uschar * privkey, unsigned options)
 {
 gstring * arcset;
 arc_set * as;
 uschar * status = arc_ar_cv_status(ar);
-arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line));
+arc_line * al = store_get(sizeof(header_line) + sizeof(arc_line), FALSE);
 header_line * h = (header_line *)(al+1);
 
 gstring * hdata = NULL;
@@ -1418,12 +1445,16 @@ blob sig;
 
 /* Construct the AS except for the signature */
 
-arcset = string_append(NULL, 10,
+arcset = string_append(NULL, 9,
 	  ARC_HDR_AS,
 	  US" i=", string_sprintf("%d", instance),
 	  US"; cv=", status,
 	  US"; a=rsa-sha256; d=", identity,			/*XXX hardwired */
-	  US"; s=", selector,					/*XXX same as AMS */
+	  US"; s=", selector);					/*XXX same as AMS */
+if (options & ARC_SIGN_OPT_TSTAMP)
+  arcset = string_append(arcset, 2,
+      US"; t=", string_sprintf("%lu", (u_long)now));
+arcset = string_cat(arcset,
 	  US";\r\n\t b=;");
 
 h->slen = arcset->ptr;
@@ -1521,7 +1552,8 @@ The dkim_exim_sign() function has already been called, so will have hashed the
 message body for us so long as we requested a hash previously.
 
 Arguments:
-  signspec	Three-element colon-sep list: identity, selector, privkey
+  signspec	Three-element colon-sep list: identity, selector, privkey.
+		Optional fourth element: comma-sep list of options.
 		Already expanded
   sigheaders	Any signature headers already generated, eg. by DKIM, or NULL
   errstr	Error string
@@ -1534,7 +1566,8 @@ Return value
 gstring *
 arc_sign(const uschar * signspec, gstring * sigheaders, uschar ** errstr)
 {
-const uschar * identity, * selector, * privkey;
+const uschar * identity, * selector, * privkey, * opts, * s;
+unsigned options = 0;
 int sep = 0;
 header_line * headers;
 hdr_rlist * rheaders;
@@ -1543,11 +1576,13 @@ int instance;
 gstring * g = NULL;
 pdkim_bodyhash * b;
 
+expire = now = 0;
+
 /* Parse the signing specification */
 
 identity = string_nextinlist(&signspec, &sep, NULL, 0);
 selector = string_nextinlist(&signspec, &sep, NULL, 0);
-if (  !*identity | !*selector
+if (  !*identity || !*selector
    || !(privkey = string_nextinlist(&signspec, &sep, NULL, 0)) || !*privkey)
   {
   log_write(0, LOG_MAIN, "ARC: bad signing-specification (%s)",
@@ -1557,6 +1592,36 @@ if (  !*identity | !*selector
 if (*privkey == '/' && !(privkey = expand_file_big_buffer(privkey)))
   return sigheaders ? sigheaders : string_get(0);
 
+if ((opts = string_nextinlist(&signspec, &sep, NULL, 0)))
+  {
+  int osep = ',';
+  while ((s = string_nextinlist(&opts, &osep, NULL, 0)))
+    if (Ustrcmp(s, "timestamps") == 0)
+      {
+      options |= ARC_SIGN_OPT_TSTAMP;
+      if (!now) now = time(NULL);
+      }
+    else if (Ustrncmp(s, "expire", 6) == 0)
+      {
+      options |= ARC_SIGN_OPT_EXPIRE;
+      if (*(s += 6) == '=')
+	if (*++s == '+')
+	  {
+	  if (!(expire = (time_t)atoi(CS ++s)))
+	    expire = ARC_SIGN_DEFAULT_EXPIRE_DELTA;
+	  if (!now) now = time(NULL);
+	  expire += now;
+	  }
+	else
+	  expire = (time_t)atol(CS s);
+      else
+	{
+	if (!now) now = time(NULL);
+	expire = now + ARC_SIGN_DEFAULT_EXPIRE_DELTA;
+	}
+      }
+  }
+
 DEBUG(D_transport) debug_printf("ARC: sign for %s\n", identity);
 
 /* Make an rlist of any new DKIM headers, then add the "normals" rlist to it.
@@ -1566,18 +1631,17 @@ string_from_gstring(sigheaders);
 if ((rheaders = arc_sign_scan_headers(&arc_sign_ctx, sigheaders)))
   {
   hdr_rlist ** rp;
-  for (rp = &rheaders; *rp; ) rp = &(*rp)->prev;
-  *rp = headers_rlist;
-  headers_rlist = rheaders;
+  for (rp = &headers_rlist; *rp; ) rp = &(*rp)->prev;
+  *rp = rheaders;
   }
-else
-  rheaders = headers_rlist;
 
 /* Finally, build a normal-order headers list */
 /*XXX only needed for hunt-the-AR? */
+/*XXX also, we really should be accepting any number of ADMD-matching ARs */
   {
   header_line * hnext = NULL;
-  for (; rheaders; hnext = rheaders->h, rheaders = rheaders->prev)
+  for (rheaders = headers_rlist; rheaders;
+       hnext = rheaders->h, rheaders = rheaders->prev)
     rheaders->h->next = hnext;
   headers = hnext;
   }
@@ -1619,7 +1683,7 @@ g = arc_sign_append_aar(g, &arc_sign_ctx, identity, instance, &ar);
 
 b = arc_ams_setup_sign_bodyhash();
 g = arc_sign_append_ams(g, &arc_sign_ctx, instance, identity, selector,
-      &b->bh, headers_rlist, privkey);
+      &b->bh, headers_rlist, privkey, options);
 
 /*
 - Generate AS
@@ -1634,13 +1698,15 @@ g = arc_sign_append_ams(g, &arc_sign_ctx, instance, identity, selector,
         including self (but with an empty b= in self)
 */
 
-g = arc_sign_prepend_as(g, &arc_sign_ctx, instance, identity, selector, &ar, privkey);
+if (g)
+  g = arc_sign_prepend_as(g, &arc_sign_ctx, instance, identity, selector, &ar,
+      privkey, options);
 
 /* Finally, append the dkim headers and return the lot. */
 
-g = string_catn(g, sigheaders->s, sigheaders->ptr);
+if (sigheaders) g = string_catn(g, sigheaders->s, sigheaders->ptr);
 (void) string_from_gstring(g);
-gstring_reset_unused(g);
+gstring_release_unused(g);
 return g;
 }
 
@@ -1677,7 +1743,13 @@ memset(&al, 0, sizeof(arc_line));
 if ((errstr = arc_parse_line(&al, &h, ARC_HDRLEN_AMS, FALSE)))
   {
   DEBUG(D_acl) if (errstr) debug_printf("ARC: %s\n", errstr);
-  return US"line parsing error";
+  goto badline;
+  }
+
+if (!al.a_hash.data)
+  {
+  DEBUG(D_acl) debug_printf("ARC: no a_hash from '%.*s'\n", h.slen, h.text);
+  goto badline;
   }
 
 /* defaults */
@@ -1696,6 +1768,9 @@ if (!(b = arc_ams_setup_vfy_bodyhash(&al)))
 should have been created here. */
 
 return NULL;
+
+badline:
+  return US"line parsing error";
 }
 
 
@@ -1720,7 +1795,37 @@ return is_vfy ? arc_header_vfy_feed(g) : arc_header_sign_feed(g);
 
 /******************************************************************************/
 
-/* Construct an Authenticate-Results header portion, for the ARC module */
+/* Construct the list of domains from the ARC chain after validation */
+
+uschar *
+fn_arc_domains(void)
+{
+arc_set * as;
+unsigned inst;
+gstring * g = NULL;
+
+for (as = arc_verify_ctx.arcset_chain, inst = 1; as; as = as->next, inst++)
+  {
+  arc_line * hdr_as = as->hdr_as;
+  if (hdr_as)
+    {
+    blob * d = &hdr_as->d;
+
+    for (; inst < as->instance; inst++)
+      g = string_catn(g, US":", 1);
+
+    g = d->data && d->len
+      ? string_append_listele_n(g, ':', d->data, d->len)
+      : string_catn(g, US":", 1);
+    }
+  else
+    g = string_catn(g, US":", 1);
+  }
+return g ? g->s : US"";
+}
+
+
+/* Construct an Authentication-Results header portion, for the ARC module */
 
 gstring *
 authres_arc(gstring * g)
@@ -1734,19 +1839,17 @@ if (arc_state)
   g = string_append(g, 2, US";\n\tarc=", arc_state);
   if (arc_received_instance > 0)
     {
-    g = string_append(g, 3, US" (i=",
-      string_sprintf("%d", arc_received_instance), US")");
+    g = string_fmt_append(g, " (i=%d)", arc_received_instance);
     if (arc_state_reason)
       g = string_append(g, 3, US"(", arc_state_reason, US")");
     g = string_catn(g, US" header.s=", 10);
     highest_ams = arc_received->hdr_ams;
     g = string_catn(g, highest_ams->s.data, highest_ams->s.len);
 
-    g = string_append(g, 2,
-      US" arc.oldest-pass=", string_sprintf("%d", arc_oldest_pass));
+    g = string_fmt_append(g, " arc.oldest-pass=%d", arc_oldest_pass);
 
     if (sender_host_address)
-      g = string_append(g, 2, US" smtp.client-ip=", sender_host_address);
+      g = string_append(g, 2, US" smtp.remote-ip=", sender_host_address);
     }
   else if (arc_state_reason)
     g = string_append(g, 3, US" (", arc_state_reason, US")");