Implement oldest-pass

* Instead of a single set of validation canons we need them for each ARC
  instance.
* `arc_add_canon()`'s deduplication of header canons was wrong, it
  didn't account for `hdrlist` and the hash includes the signature header
  itself so these are always different.
* Body canons, which are more expensive, can easily be deduplicated
  and weren't.
* `arc_state` was referenced a couple of times when `arc_cstate` was
  meant, in a way that made the checks always false in normal operation.
  The check that wasn't redundant was wrong, though, so two bugs canceled
  each other out.

CHANGELOG.md

@@ -5,6 +5,8 @@ All notable changes to this project will be documented in this file.
 ## Unreleased
 
 ### Added
+- `oldest-pass` processing per [RFC 8617 section 5.2](https://datatracker.ietf.org/doc/html/rfc8617#section-5.2).
+- libopenarc - `arc_chain_oldest_pass()`
 - milter - `AuthResIP` configuration option.
 - milter - `RequireSafeKeys` configuration option.
 
@@ -22,6 +24,8 @@ All notable changes to this project will be documented in this file.
   are excluded from the AMS, as required by RFC 8617.
 - libopenarc - ARC headers are returned with a space before the header value.
 - libopenarc - String arguments are marked as `const` where applicable.
+- milter - `Authentication-Results` and `ARC-Authentication-Results` include
+  `header.oldest-pass` when appropriate.
 
 ### Fixed
 - libopenarc - Seals on failed chains only cover the latest ARC header set,
@@ -32,6 +36,8 @@ All notable changes to this project will be documented in this file.
 - libopenarc - The installed pkg-config file is more correct.
 - libopenarc - U-labels (domain labels encoded as UTF-8) are allowed in `d=`
   and `s=` tags.
+- libopenarc - `arc_eom()` propagates internal errors like memory allocation
+  failure instead of marking the chain as failed.
 - milter - Use after free.
 - milter - Unlikely division by zero.
 - milter - Small memory leak during config loading.

libopenarc/arc-canon.c

@@ -684,12 +684,16 @@ arc_add_canon(ARC_MESSAGE         *msg,
 
     assert(hashtype == ARC_HASHTYPE_SHA1 || hashtype == ARC_HASHTYPE_SHA256);
 
-    if (type == ARC_CANONTYPE_HEADER)
+    /* Body canons can be shared if the parameters match. Header canons could
+     * theoretically be partially shared if the `h` tags match, but it would be
+     * complex so we don't currently do it. */
+    if (type == ARC_CANONTYPE_BODY)
     {
         for (cur = msg->arc_canonhead; cur != NULL; cur = cur->canon_next)
         {
-            if (cur->canon_type != ARC_CANONTYPE_HEADER ||
-                cur->canon_hashtype != hashtype || cur->canon_length != length)
+            if (cur->canon_type != ARC_CANONTYPE_BODY ||
+                cur->canon_canon != canon || cur->canon_hashtype != hashtype ||
+                cur->canon_length != length)
             {
                 continue;
             }
@@ -1947,6 +1951,7 @@ arc_canon_getsealhash(ARC_MESSAGE *msg, int setnum, void **sh, size_t *shlen)
 **
 **  Parameters:
 **  	msg -- ARC message from which to get completed hashes
+**      setnum -- which seal's hashes to get
 **  	hh -- pointer to header hash buffer (returned)
 **  	hhlen -- bytes used at hh (returned)
 **  	bh -- pointer to body hash buffer (returned)
@@ -1958,8 +1963,12 @@ arc_canon_getsealhash(ARC_MESSAGE *msg, int setnum, void **sh, size_t *shlen)
 */
 
 ARC_STAT
-arc_canon_gethashes(
-    ARC_MESSAGE *msg, void **hh, size_t *hhlen, void **bh, size_t *bhlen)
+arc_canon_gethashes(ARC_MESSAGE *msg,
+                    int          setnum,
+                    void       **hh,
+                    size_t      *hhlen,
+                    void       **bh,
+                    size_t      *bhlen)
 {
     ARC_STAT          status;
     struct arc_canon *hdc;
@@ -1969,8 +1978,8 @@ arc_canon_gethashes(
     size_t            hdlen;
     size_t            bdlen;
 
-    hdc = msg->arc_valid_hdrcanon;
-    bdc = msg->arc_valid_bodycanon;
+    hdc = msg->arc_hdrcanons[setnum - 1];
+    bdc = msg->arc_bodycanons[setnum - 1];
 
     status = arc_canon_getfinal(hdc, &hd, &hdlen);
     if (status != ARC_STAT_OK)

libopenarc/arc-canon.h

@@ -41,7 +41,7 @@ extern void     arc_canon_cleanup(ARC_MESSAGE *);
 extern ARC_STAT arc_canon_closebody(ARC_MESSAGE *);
 extern ARC_STAT arc_canon_getfinal(ARC_CANON *, unsigned char **, size_t *);
 extern ARC_STAT arc_canon_gethashes(
-    ARC_MESSAGE *, void **, size_t *, void **, size_t *);
+    ARC_MESSAGE *, int, void **, size_t *, void **, size_t *);
 extern ARC_STAT arc_canon_getsealhash(ARC_MESSAGE *, int, void **, size_t *);
 extern ARC_STAT arc_canon_header_string(
     struct arc_dstring *, arc_canon_t, const char *, size_t, bool);

libopenarc/arc-types.h

@@ -121,6 +121,7 @@ struct arc_msghandle
     bool                 arc_infail;
     int                  arc_dnssec_key;
     int                  arc_signalg;
+    int                  arc_oldest_pass;
     unsigned int         arc_mode;
     unsigned int         arc_nsets;
     unsigned int         arc_margin;
@@ -158,9 +159,9 @@ struct arc_msghandle
     struct arc_dstring  *arc_hdrbuf;
     struct arc_canon    *arc_sealcanon;
     struct arc_canon   **arc_sealcanons;
-    struct arc_canon    *arc_valid_hdrcanon;
+    struct arc_canon   **arc_hdrcanons;
+    struct arc_canon   **arc_bodycanons;
     struct arc_canon    *arc_sign_hdrcanon;
-    struct arc_canon    *arc_valid_bodycanon;
     struct arc_canon    *arc_sign_bodycanon;
     struct arc_canon    *arc_canonhead;
     struct arc_canon    *arc_canontail;