[gnunet-scheme] 06/49: dht/client: Implement message verifiers.

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maxime-devos pushed a commit to branch master
in repository gnunet-scheme.

commit ed1806824099f59570e8e887b213a807937a60b9
Author: Maxime Devos <maximedevos@telenet.be>
AuthorDate: Thu Sep 16 16:54:48 2021 +0200

    dht/client: Implement message verifiers.
    
    * gnu/gnunet/dht/client.scm: New module.
---
 Makefile.am               |   1 +
 gnu/gnunet/dht/client.scm | 110 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 111 insertions(+)

diff --git a/Makefile.am b/Makefile.am
index afa6103..5c7aa2e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -63,6 +63,7 @@ modules = \
   gnu/gnunet/config/db.scm \
   gnu/gnunet/config/fs.scm \
   \
+  gnu/gnunet/dht/client.scm \
   gnu/gnunet/dht/struct.scm \
   \
   gnu/gnunet/util/cmsg.scm \
diff --git a/gnu/gnunet/dht/client.scm b/gnu/gnunet/dht/client.scm
new file mode 100644
index 0000000..1f65a23
--- /dev/null
+++ b/gnu/gnunet/dht/client.scm
@@ -0,0 +1,110 @@
+;; This file is part of GNUnet
+;; Copyright (C) 2004-2013, 2016 GNUnet e.V.
+;; Copyright (C) 2021 Maxime Devos
+;;
+;; GNUnet is free software: you can redistribute it and/or modify it
+;; under the terms of the GNU Affero General Public License as published
+;; by the Free Software Foundation, either version 3 of the License,
+;; or (at your option) any later version.
+;;
+;; GNUnet is distributed in the hope that it will be useful, but
+;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;; Affero General Public License for more details.
+;;
+;; You should have received a copy of the GNU Affero General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+;;
+;; SPDX-License-Identifier: AGPL-3.0-or-later
+
+;; Author: Christian Grothoff
+;; Author: Nathan Evans
+;; ^^ TODO: not visible yet, but once more parts are ported ...
+;; Author: Maxime Devos (Scheme port)
+(define-library (gnu gnunet dht client)
+  (export connect
+         disconnect!
+         put!
+         cancel-put!
+         start-get!
+         filter-get:known-results!
+         stop-get!
+         ;; Extended API: monitor
+         start-monitor!
+         stop-monitor!)
+  (import (gnu gnunet mq handler)
+         (only (guile)
+               define-syntax-rule)
+         (only (gnu extractor enum)
+               symbol-value)
+         (gnu gnunet dht struct)
+         (only (gnu gnunet crypto struct)
+               /peer-identity)
+         (only (gnu gnunet message protocols)
+               message-type)
+         (only (gnu gnunet netstruct syntactic)
+               read% sizeof)
+         (only (gnu gnunet utils bv-slice)
+               slice-length slice/read-only)
+         (only (rnrs base)
+               and >= = quote * + - define begin ... let*))
+  (begin
+    (define-syntax-rule (well-formed?/path-length slice type (field ...) 
compare)
+      "Verify the TYPE message in @var{slice}, which has @var{field ...} ...
+(e.g. one or more of get-path-length or put-path-length) and corresponding
+/peer-identities at the end of the message is well-formed -- i.e., check if 
the length
+of @var{slice} corresponds to the size of @var{type} and the get-path-length 
and
+put-path-length.
+
+@var{compare} must be @code{=} if no additional payload follows, or @code{>=}
+if an addiional payload may follow.  The message type and the size in the
+message header is assumed to be correct."
+      ;; Warning: slice is evaluated multiple times!
+      (and (>= (slice-length slice) (sizeof type '()))
+          (let* ((header (slice/read-only slice 0 (sizeof type '())))
+                 (extra-size (- (slice-length slice) (sizeof type '())))
+                 (field (read% type '(field) slice))
+                 ...)
+            (compare extra-size (* (+ field ...) (sizeof /peer-identity 
'()))))))
+
+    ;; TODO: WIP!
+    (define (reconnect . todo)
+      (define handlers
+       (message-handlers
+        (message-handler
+         (type (symbol-value message-type msg:dht:monitor:get))
+         ((interpose exp) exp)
+         ((well-formed? slice)
+          ;; The C implementation verifies that 'get-path-length' at most
+          ;; (- (expt 2 16) 1), but this seems only to prevent integer 
overflow,
+          ;; which cannot happen in Scheme due to the use of bignums.
+          ;;
+          ;; This message does _not_ have a payload, so use = instead of >=.
+          (well-formed?/path-length slice /:msg:dht:monitor:get-response
+                                    (get-path-length) =))
+         ((handle! slice) ???))
+        (message-handler
+         (type (symbol-value message-type msg:dht:monitor:get-response))
+         ((interpose exp) exp)
+         ((well-formed? slice)
+          ;; Payload follows, hence >= instead of =.
+          (well-formed?/path-length slice /:msg:dht:monitor:get-response
+                                    (get-path-length put-path-length) >=))
+         ((handle! slice) ???))
+        (message-handler
+         (type (symbol-value message-type msg:dht:monitor:put))
+         ((interpose exp) exp)
+         ((well-formed? slice)
+          ;; Payload follows, hence >= instead of =.
+          (well-formed?/path-length slice /:msg:dht:monitor:put
+                                    (put-path-length) >=))
+         ((handle! slice) ???))
+        (message-handler
+         (type (symbol-value message-type msg:dht:client:result))
+         ((interpose exp) exp)
+         ((well-formed? slice)
+          ;; Actual data follows, hence >= instead of =.
+          (well-formed?/path-length slice /:msg:dht:client:result
+                                    (get-path-length put-path-length) >=))
+         ((handle! slice) ???))))
+      todo)))

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