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authorLudovic Courtès <ludo@gnu.org>2019-12-03 21:28:23 +0100
committerLudovic Courtès <ludo@gnu.org>2019-12-04 18:16:08 +0100
commit114dcb429a812911633a9fe5a9ee7d70dd28b353 (patch)
tree0e381f5324a05ade7b152c422de98fdd08f90625 /guix/ssh.scm
parentd75540473f3f460007f45efab5122c39aa4130ff (diff)
ssh: Add 'authenticate-server*' and use it for offloading.
* guix/scripts/offload.scm (host-key->type+key): Remove. (open-ssh-session): Replace server authentication code with a call to 'authenticate-server*'. * guix/ssh.scm (host-key->type+key, authenticate-server*): New procedures.
Diffstat (limited to 'guix/ssh.scm')
-rw-r--r--guix/ssh.scm37
1 files changed, 37 insertions, 0 deletions
diff --git a/guix/ssh.scm b/guix/ssh.scm
index 5fd3c280e8..f34e71392b 100644
--- a/guix/ssh.scm
+++ b/guix/ssh.scm
@@ -37,6 +37,8 @@
#:use-module (ice-9 format)
#:use-module (ice-9 binary-ports)
#:export (open-ssh-session
+ authenticate-server*
+
remote-inferior
remote-daemon-channel
connect-to-remote-daemon
@@ -60,6 +62,41 @@
(define %compression
"zlib@openssh.com,zlib")
+(define (host-key->type+key host-key)
+ "Destructure HOST-KEY, an OpenSSH host key string, and return two values:
+its key type as a symbol, and the actual base64-encoded string."
+ (define (type->symbol type)
+ (and (string-prefix? "ssh-" type)
+ (string->symbol (string-drop type 4))))
+
+ (match (string-tokenize host-key)
+ ((type key x)
+ (values (type->symbol type) key))
+ ((type key)
+ (values (type->symbol type) key))))
+
+(define (authenticate-server* session key)
+ "Make sure the server for SESSION has the given KEY, where KEY is a string
+such as \"ssh-ed25519 AAAAC3Nz… root@example.org\". Raise an exception if the
+actual key does not match."
+ (let-values (((server) (get-server-public-key session))
+ ((type key) (host-key->type+key key)))
+ (unless (and (or (not (get-key-type server))
+ (eq? (get-key-type server) type))
+ (string=? (public-key->string server) key))
+ ;; Key mismatch: something's wrong. XXX: It could be that the server
+ ;; provided its Ed25519 key when we where expecting its RSA key. XXX:
+ ;; Guile-SSH 0.10.1 doesn't know about ed25519 keys and 'get-key-type'
+ ;; returns #f in that case.
+ (raise (condition
+ (&message
+ (message (format #f (G_ "server at '~a' returned host key \
+'~a' of type '~a' instead of '~a' of type '~a'~%")
+ (session-get session 'host)
+ (public-key->string server)
+ (get-key-type server)
+ key type))))))))
+
(define* (open-ssh-session host #:key user port identity
(compression %compression)
(timeout 3600))