;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2020-2022 Ludovic Courtès <ludo@gnu.org> ;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org> ;;; ;;; This file is part of GNU Guix. ;;; ;;; GNU Guix is free software; you can redistribute it and/or modify it ;;; under the terms of the GNU General Public License as published by ;;; the Free Software Foundation; either version 3 of the License, or (at ;;; your option) any later version. ;;; ;;; GNU Guix 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 General Public License for more details. ;;; ;;; You should have received a copy of the GNU General Public License ;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>. (define-module (gnu build secret-service) #:use-module (guix build utils) #:use-module (srfi srfi-26) #:use-module (rnrs bytevectors) #:use-module (ice-9 binary-ports) #:use-module (ice-9 match) #:use-module (ice-9 rdelim) #:export (secret-service-receive-secrets secret-service-send-secrets)) ;;; Commentary: ;;; ;;; Utility procedures for copying secrets into a VM. ;;; ;;; Code: (define-syntax log (lambda (s) "Log the given message." (syntax-case s () ((_ fmt args ...) (with-syntax ((fmt (string-append "secret service: " (syntax->datum #'fmt)))) ;; Log to the current output port. That way, when ;; 'secret-service-send-secrets' is called from shepherd, output goes ;; to syslog. #'(format (current-output-port) fmt args ...)))))) (define-syntax with-modules (syntax-rules () "Dynamically load the given MODULEs at run time, making the chosen bindings available within the lexical scope of BODY." ((_ ((module #:select (bindings ...)) rest ...) body ...) (let* ((iface (resolve-interface 'module)) (bindings (module-ref iface 'bindings)) ...) (with-modules (rest ...) body ...))) ((_ () body ...) (begin body ...)))) (define (wait-for-readable-fd port timeout) "Wait until PORT has data available for reading or TIMEOUT has expired. Return #t in the former case and #f in the latter case." (match (resolve-module '(fibers) #f #:ensure #f) ;using Fibers? (#f (log "blocking on socket...~%") (match (select (list port) '() '() timeout) (((_) () ()) #t) ((() () ()) #f))) (fibers ;; We're running on the Shepherd 0.9+ with Fibers. Arrange to make a ;; non-blocking wait so that other fibers can be scheduled in while we ;; wait for PORT. (with-modules (((fibers) #:select (spawn-fiber sleep)) ((fibers channels) #:select (make-channel put-message get-message))) ;; Make PORT non-blocking. (let ((flags (fcntl port F_GETFL))) (fcntl port F_SETFL (logior O_NONBLOCK flags))) (let ((channel (make-channel))) (spawn-fiber (lambda () (sleep timeout) ;suspends the fiber (put-message channel 'timeout))) (spawn-fiber (lambda () (lookahead-u8 port) ;suspends the fiber (put-message channel 'readable))) (log "suspending fiber on socket...~%") (match (get-message channel) ('readable #t) ('timeout #f))))))) (define* (secret-service-send-secrets port secret-root #:key (retry 60) (handshake-timeout 180)) "Copy all files under SECRET-ROOT using TCP to secret-service listening at local PORT. If connect fails, sleep 1s and retry RETRY times; once connected, wait for at most HANDSHAKE-TIMEOUT seconds for handshake to complete. Return #f on failure." (define (file->file+size+mode file-name) (let ((stat (stat file-name)) (target (substring file-name (string-length secret-root)))) (list target (stat:size stat) (stat:mode stat)))) (define (send-files sock) (let* ((files (if secret-root (find-files secret-root) '())) (files-sizes-modes (map file->file+size+mode files)) (secrets `(secrets (version 0) (files ,files-sizes-modes)))) (write secrets sock) (for-each (lambda (file) (call-with-input-file file (lambda (input) (dump-port input sock)))) files))) (log "sending secrets to ~a~%" port) (let ((sock (socket AF_INET (logior SOCK_CLOEXEC SOCK_STREAM) 0)) (addr (make-socket-address AF_INET INADDR_LOOPBACK port)) (sleep (if (resolve-module '(fibers) #f) (module-ref (resolve-interface '(fibers)) 'sleep) sleep))) ;; Connect to QEMU on the forwarded port. The 'connect' call succeeds as ;; soon as QEMU is ready, even if there's no server listening on the ;; forward port inside the guest. (let loop ((retry retry)) (catch 'system-error (cute connect sock addr) (lambda (key . args) (when (zero? retry) (apply throw key args)) (log "retrying connection [~a attempts left]~%" (- retry 1)) (sleep 1) (loop (1- retry))))) (log "connected; waiting for handshake...~%") ;; Wait for "hello" message from the server. This is the only way to know ;; that we're really connected to the server inside the guest. (if (wait-for-readable-fd sock handshake-timeout) (match (read sock) (('secret-service-server ('version version ...)) (log "sending files from ~s...~%" secret-root) (send-files sock) (log "done sending files to port ~a~%" port) (close-port sock) secret-root) (x (log "invalid handshake ~s~%" x) (close-port sock) #f)) (begin ;timeout (log "timeout while sending files to ~a~%" port) (close-port sock) #f)))) (define (delete-file* file) "Ensure FILE does not exist." (catch 'system-error (lambda () (delete-file file)) (lambda args (unless (= ENOENT (system-error-errno args)) (apply throw args))))) (define (secret-service-receive-secrets port) "Listen to local PORT and wait for a secret service client to send secrets. Write them to the file system. Return the list of files installed on success, and #f otherwise." (define (wait-for-client port) ;; Wait for a TCP connection on PORT. Note: We cannot use the ;; virtio-serial ports, which would be safer, because they are ;; (presumably) unsupported on GNU/Hurd. (let ((sock (socket AF_INET (logior SOCK_CLOEXEC SOCK_STREAM) 0))) (bind sock AF_INET INADDR_ANY port) (listen sock 1) (log "waiting for secrets on port ~a...~%" port) (match (select (list sock) '() '() 60) (((_) () ()) (match (accept sock) ((client . address) (log "client connection from ~a~%" (inet-ntop (sockaddr:fam address) (sockaddr:addr address))) ;; Send a "hello" message. This allows the client running on the ;; host to know that it's now actually connected to server running ;; in the guest. (write '(secret-service-server (version 0)) client) (force-output client) (close-port sock) client))) ((() () ()) (log "did not receive any secrets; time out~%") (close-port sock) #f)))) ;; TODO: Remove when (@ (guix build utils) dump-port) has a 'size' ;; parameter. (define (dump in out size) ;; Copy SIZE bytes from IN to OUT. (define buf-size 65536) (define buf (make-bytevector buf-size)) (let loop ((left size)) (if (<= left 0) 0 (let ((read (get-bytevector-n! in buf 0 (min left buf-size)))) (if (eof-object? read) left (begin (put-bytevector out buf 0 read) (loop (- left read)))))))) (define (read-secrets port) ;; Read secret files from PORT and install them. (match (false-if-exception (read port)) (('secrets ('version 0) ('files ((files sizes modes) ...))) (for-each (lambda (file size mode) (log "installing file '~a' (~a bytes)...~%" file size) (mkdir-p (dirname file)) ;; It could be that FILE already exists, for instance ;; because it has been created by a service's activation ;; snippet (e.g., SSH host keys). Delete it. (delete-file* file) (call-with-output-file file (lambda (output) (dump port output size) (chmod file mode)))) files sizes modes) (log "received ~a secret files~%" (length files)) files) (_ (log "invalid secrets received~%") #f))) (let* ((port (wait-for-client port)) (result (and=> port read-secrets))) (when port (close-port port)) result)) ;;; Local Variables: ;;; eval: (put 'with-modules 'scheme-indent-function 1) ;;; End: ;;; secret-service.scm ends here