gpgsm: Handle re-issued CA certificates in a better way.

* sm/certchain.c (find_up_search_by_keyid): Consider all matching
certificates.
(find_up): Add some debug messages.
--

The DFN-Verein recently re-issued its CA certificates without
generating new keys.  Thus looking up the chain using the authority
keyids works but may use still existing old certificates.  This may
break the CRL lookup in the Dirmngr.  The hack to fix this is by using
the latest issued certificate with the same subject key identifier.

As usual Peter Gutman's X.509 style guide has some comments on that
re-issuing.

GnuPG-bug-id: 1644

1 files changed, 59 insertions, 3 deletions

diff --git a/sm/certchain.c b/sm/certchain.c
index b51291dfe..5f5fd80a5 100644
--- a/sm/certchain.c
+++ b/sm/certchain.c
@@ -444,6 +444,8 @@ find_up_search_by_keyid (KEYDB_HANDLE kh,
   int rc;
   ksba_cert_t cert = NULL;
   ksba_sexp_t subj = NULL;
+  int anyfound = 0;
+  ksba_isotime_t not_before, last_not_before;
 
   keydb_search_reset (kh);
   while (!(rc = keydb_search_subject (kh, issuer)))
@@ -460,10 +462,37 @@ find_up_search_by_keyid (KEYDB_HANDLE kh,
       if (!ksba_cert_get_subj_key_id (cert, NULL, &subj))
         {
           if (!cmp_simple_canon_sexp (keyid, subj))
-            break; /* Found matching cert. */
+            {
+              /* Found matching cert. */
+              rc = ksba_cert_get_validity (cert, 0, not_before);
+              if (rc)
+                {
+                  log_error ("keydb_get_validity() failed: rc=%d\n", rc);
+                  rc = -1;
+                  break;
+                }
+
+              if (!anyfound || strcmp (last_not_before, not_before) < 0)
+                {
+                  /* This certificate is the first one found or newer
+                     than the previous one.  This copes with
+                     re-issuing CA certificates while keeping the same
+                     key information.  */
+                  anyfound = 1;
+                  gnupg_copy_time (last_not_before, not_before);
+                  keydb_push_found_state (kh);
+                }
+            }
         }
     }
 
+  if (anyfound)
+    {
+      /* Take the last saved one.  */
+      keydb_pop_found_state (kh);
+      rc = 0;  /* Ignore EOF or other error after the first cert.  */
+    }
+
   ksba_cert_release (cert);
   xfree (subj);
   return rc? -1:0;
@@ -606,6 +635,8 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
   ksba_sexp_t keyid;
   int rc = -1;
 
+  if (DBG_X509)
+    log_debug ("looking for parent certificate\n");
   if (!ksba_cert_get_auth_key_id (cert, &keyid, &authid, &authidno))
     {
       const char *s = ksba_name_enum (authid, 0);
@@ -615,6 +646,9 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
           if (rc)
             keydb_search_reset (kh);
 
+          if (!rc && DBG_X509)
+            log_debug ("  found via authid and sn+issuer\n");
+
           /* In case of an error, try to get the certificate from the
              dirmngr.  That is done by trying to put that certifcate
              into the ephemeral DB and let the code below do the
@@ -634,6 +668,9 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
                   rc = keydb_search_issuer_sn (kh, s, authidno);
                   if (rc)
                     keydb_search_reset (kh);
+
+                  if (!rc && DBG_X509)
+                    log_debug ("  found via authid and sn+issuer (ephem)\n");
                 }
               keydb_set_ephemeral (kh, old);
             }
@@ -649,11 +686,15 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
              subjectKeyIdentifier. */
           /* Fixme: Should we also search in the dirmngr?  */
           rc = find_up_search_by_keyid (kh, issuer, keyid);
+          if (!rc && DBG_X509)
+            log_debug ("  found via authid and keyid\n");
           if (rc)
             {
               int old = keydb_set_ephemeral (kh, 1);
               if (!old)
                 rc = find_up_search_by_keyid (kh, issuer, keyid);
+              if (!rc && DBG_X509)
+                log_debug ("  found via authid and keyid (ephem)\n");
               keydb_set_ephemeral (kh, old);
             }
           if (rc)
@@ -678,11 +719,19 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
             }
           if (rc)
             rc = -1; /* Need to make sure to have this error code. */
+
+          if (!rc && DBG_X509)
+            log_debug ("  found via authid and issuer from dirmngr cache\n");
         }
 
       /* If we still didn't found it, try an external lookup.  */
       if (rc == -1 && opt.auto_issuer_key_retrieve && !find_next)
-        rc = find_up_external (ctrl, kh, issuer, keyid);
+        {
+          rc = find_up_external (ctrl, kh, issuer, keyid);
+          if (!rc && DBG_X509)
+            log_debug ("  found via authid and external lookup\n");
+        }
+
 
       /* Print a note so that the user does not feel too helpless when
          an issuer certificate was found and gpgsm prints BAD
@@ -733,11 +782,18 @@ find_up (ctrl_t ctrl, KEYDB_HANDLE kh,
           rc = keydb_search_subject (kh, issuer);
         }
       keydb_set_ephemeral (kh, old);
+
+      if (!rc && DBG_X509)
+        log_debug ("  found via issuer\n");
     }
 
   /* Still not found.  If enabled, try an external lookup.  */
   if (rc == -1 && opt.auto_issuer_key_retrieve && !find_next)
-    rc = find_up_external (ctrl, kh, issuer, NULL);
+    {
+      rc = find_up_external (ctrl, kh, issuer, NULL);
+      if (!rc && DBG_X509)
+        log_debug ("  found via issuer and external lookup\n");
+    }
 
   return rc;
 }