>From 67ba3f6e6fcb12b99757fcc49f86f951ad59c02b Mon Sep 17 00:00:00 2001 From: "F. Jason Park" Date: Mon, 14 Feb 2022 02:36:57 -0800 Subject: [PATCH 4/5] Support SOCKS resolve extension * lisp/net/socks.el (socks-resolve-command): Add new constant for the SOCKS command RESOLVE, which comes by way of a nonstandard extension from the TOR project. It mirrors CONNECT in most respects but asks the server to RESOLVE a host name and return its IP. For details, see https://github.com/torproject/torspec/blob/master/socks-extensions.txt This shouldn't be confused with 5h/5-hostname, which is used to by clients like cURL to allow users to bypass attempts to resolve a name locally. (socks--extract-resolve-response, socks-tor-resolve): Add utility functions to query a SOCKS service supporting the RESOLVE extension. Bug#53941 --- lisp/net/socks.el | 61 ++++++++++++++++++++++++++++++++++++ test/lisp/net/socks-tests.el | 34 ++++++++++++++++++++ 2 files changed, 95 insertions(+) diff --git a/lisp/net/socks.el b/lisp/net/socks.el index a2198d898a..02edd95328 100644 --- a/lisp/net/socks.el +++ b/lisp/net/socks.el @@ -181,6 +181,9 @@ socks-udp-associate-command (defconst socks-authentication-null 0) (defconst socks-authentication-failure 255) +;; Extensions +(defconst socks-resolve-command #xf0) + ;; Response codes (defconst socks-response-success 0) (defconst socks-response-general-failure 1) @@ -653,6 +656,64 @@ socks-nslookup-host res) host)) +(defun socks--extract-resolve-response (proc) + "Parse response for PROC and maybe return destination IP address." + (let ((response (process-get proc 'socks-response))) + (cl-assert response) ; otherwise, msg not received in its entirety + (pcase (process-get proc 'socks-server-protocol) + (4 ; https://www.openssh.com/txt/socks4a.protocol + (when-let (((zerop (process-get proc 'socks-reply))) + ((eq (aref response 1) 90)) ; #x5a request granted + (a (substring response 4)) ; ignore port for now + ((not (string-empty-p a))) + ((not (string= a "\0\0\0\0")))) + a)) + (5 ; https://tools.ietf.org/html/rfc1928 + (cl-assert (eq 5 (aref response 0)) t) + (pcase (aref response 3) ; ATYP + (1 (and-let* ((a (substring response 4 8)) + ((not (string= a "\0\0\0\0"))) + a))) + ;; No reason to support RESOLVE_PTR [F1] extension, right? + (3 (let ((len (1- (aref response 4)))) + (substring response 5 (+ 5 len)))) + (4 (substring response 4 20))))))) + +(declare-function puny-encode-domain "puny" (domain)) + +(defun socks-tor-resolve (name &optional _family) + "Return list of one vector IPv4 address for domain NAME. +Or return nil on failure. See `network-lookup-address-info' for format +of return value. Server must support the Tor RESOLVE command." + (let ((socks-password (or socks-password "")) + host + (port 80) ; unused for now + route + proc + ip) + (unless (string-suffix-p ".onion" name) + (setq host (if (string-match "\\`[[:ascii:]]+\\'" name) + name + (require 'puny) + (puny-encode-domain name)) + route (socks-find-route host port)) + (cl-assert route) + ;; "Host unreachable" may be raised when the lookup fails + (unwind-protect + (progn + (setq proc (socks-open-connection route)) + (socks-send-command proc + socks-resolve-command + socks-address-type-name + host + port) + (cl-assert (eq (process-get proc 'socks-state) + socks-state-connected)) + (setq ip (socks--extract-resolve-response proc))) + (when proc + (delete-process proc))) + (list (vconcat ip [0]))))) + (provide 'socks) ;;; socks.el ends here diff --git a/test/lisp/net/socks-tests.el b/test/lisp/net/socks-tests.el index 4e990ffdba..3d1aca9af4 100644 --- a/test/lisp/net/socks-tests.el +++ b/test/lisp/net/socks-tests.el @@ -295,4 +295,38 @@ socks-tests-v5-auth-none (socks-tests-perform-hello-world-http-request))) (should (assq 2 socks-authentication-methods))) +(ert-deftest tor-resolve-4a () + "Make request to TOR resolve service over SOCKS4a" + (let* ((socks-server '("server" "127.0.0.1" 19050 4a)) + (socks-tests-canned-server-patterns + '(([4 #xf0 0 80 0 0 0 1 ?f ?o ?o 0 ?e ?x ?a ?m ?p ?l ?e ?. ?c ?o ?m 0] + . [0 90 0 0 93 184 216 34]))) + (inhibit-message noninteractive) + (server (socks-tests-canned-server-create))) + (ert-info ("Query TOR RESOLVE service over SOCKS4") + (cl-letf (((symbol-function 'user-full-name) + (lambda (&optional _) "foo"))) + (should (equal '([93 184 216 34 0]) + (socks-tor-resolve "example.com"))))) + (kill-buffer (process-buffer server)) + (delete-process server))) + +(ert-deftest tor-resolve-5 () + "Make request to TOR resolve service over SOCKS5" + (let* ((socks-server '("server" "127.0.0.1" 19051 5)) + (socks-username "foo") + (socks-authentication-methods (append socks-authentication-methods + nil)) + (inhibit-message noninteractive) + (socks-tests-canned-server-patterns + '(([5 2 0 2] . [5 2]) + ([1 3 ?f ?o ?o 0] . [1 0]) + ([5 #xf0 0 3 11 ?e ?x ?a ?m ?p ?l ?e ?. ?c ?o ?m 0 80] + . [5 0 0 1 93 184 216 34 0 0]))) + (server (socks-tests-canned-server-create))) + (ert-info ("Query TOR RESOLVE service over SOCKS5") + (should (equal '([93 184 216 34 0]) (socks-tor-resolve "example.com")))) + (kill-buffer (process-buffer server)) + (delete-process server))) + ;;; socks-tests.el ends here -- 2.35.1