config: define new option index.try_decrypt

By default, notmuch won't try to decrypt on indexing.  With this
patch, we make it possible to indicate a per-database preference using
the config variable "index.try_decrypt", which by default will be
false.

At indexing time, the database needs some way to know its internal
defaults for how to index encrypted parts.  It shouldn't be contingent
on an external config file (since that can't be retrieved from the
database object itself), so we store it in the database.

This behaves similarly to the query.* configurations, which are also
stored in the database itself, so we're not introducing any new
dependencies by requiring that it be stored in the database.

doc/man1/notmuch-config.rst

@@ -138,6 +138,19 @@ The available configuration items are described below.
 
         Default: ``gpg``.
 
+    **index.try_decrypt**
+
+        **[STORED IN DATABASE]**
+        When indexing an encrypted e-mail message, if this variable is
+        set to true, notmuch will try to decrypt the message and index
+        the cleartext.  Be aware that the index is likely sufficient
+        to reconstruct the cleartext of the message itself, so please
+        ensure that the notmuch message index is adequately protected.
+        DO NOT USE ``index.try_decrypt=true`` without considering the
+        security of your index.
+
+        Default: ``false``.
+
     **built_with.<name>**
 
         Compile time feature <name>. Current possibilities include

doc/man7/notmuch-properties.rst

@@ -70,13 +70,15 @@ of its normal activity.
     properties will be set on the message as a whole.
 
     If notmuch never tried to decrypt an encrypted message during
-    indexing (which is the default), then this property will not be
+    indexing (which is the default, see ``index.try_decrypt`` in
-    set on that message.
+    **notmuch-config(1)**), then this property will not be set on that
+    message.
 
 SEE ALSO
 ========
 
 **notmuch(1)**,
+**notmuch-config(1)**,
 **notmuch-dump(1)**,
 **notmuch-insert(1)**,
 **notmuch-new(1)**,

lib/indexopts.c

@@ -23,7 +23,23 @@
 notmuch_indexopts_t *
 notmuch_database_get_default_indexopts (notmuch_database_t *db)
 {
-    return talloc_zero (db, notmuch_indexopts_t);
+    notmuch_indexopts_t *ret = talloc_zero (db, notmuch_indexopts_t);
+    if (!ret)
+	return ret;
+
+    char * try_decrypt;
+    notmuch_status_t err = notmuch_database_get_config (db, "index.try_decrypt", &try_decrypt);
+    if (err)
+	return ret;
+
+    if (try_decrypt &&
+	((!(strcasecmp(try_decrypt, "true"))) ||
+	 (!(strcasecmp(try_decrypt, "yes"))) ||
+	 (!(strcasecmp(try_decrypt, "1")))))
+	notmuch_indexopts_set_try_decrypt (ret, true);
+
+    free (try_decrypt);
+    return ret;
 }
 
 notmuch_status_t

notmuch-config.c

@@ -812,8 +812,14 @@ _item_split (char *item, char **group, char **key)
 static bool
 _stored_in_db (const char *item)
 {
+    const char * db_configs[] = {
+	"index.try_decrypt",
+    };
     if (STRNCMP_LITERAL (item, "query.") == 0)
 	return true;
+    for (size_t i = 0; i < ARRAY_SIZE (db_configs); i++)
+	if (strcmp (item, db_configs[i]) == 0)
+	    return true;
     return false;
 }