Subject: [bug#75144] [PATCH v3 1/2] guix: ssh: Add strict-host-key-check? option.

From: Roman Scherer <[email-masked]>
Date: Tue, 4 Feb 2025 20:01:13 +0100

* guix/ssh.scm (open-ssh-session): Add strict-host-key-check? option.

Change-Id: Iae5df5ac8d45033b6b636e9c872f8910d4f6cfe9
---
 guix/ssh.scm | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/guix/ssh.scm b/guix/ssh.scm
index ae506df14c..8decfdbab9 100644
--- a/guix/ssh.scm
+++ b/guix/ssh.scm
@@ -103,7 +103,8 @@ (define* (open-ssh-session host #:key user port identity
                            host-key
                            (compression %compression)
                            (timeout 3600)
-                           (connection-timeout 10))
+                           (connection-timeout 10)
+                           (strict-host-key-check? #t))
   "Open an SSH session for HOST and return it.  IDENTITY specifies the file
 name of a private key to use for authenticating with the host.  When USER,
 PORT, or IDENTITY are #f, use default values or whatever '~/.ssh/config'
@@ -117,6 +118,9 @@ (define* (open-ssh-session host #:key user port identity
 seconds.  Install TIMEOUT as the maximum time in seconds after which a read or
 write operation on a channel of the returned session is considered as failing.
 
+IF STRICT-HOST-KEY-CHECK? is #f, strict host key checking is turned off for
+the new session.
+
 Throw an error on failure."
   (let ((session (make-session #:user user
                                #:identity identity
@@ -137,7 +141,8 @@ (define* (open-ssh-session host #:key user port identity
 
                                ;; Speed up RPCs by creating sockets with
                                ;; TCP_NODELAY.
-                               #:nodelay #t)))
+                               #:nodelay #t
+                               #:stricthostkeycheck strict-host-key-check?)))
 
     ;; Honor ~/.ssh/config.
     (session-parse-config! session)
@@ -149,13 +154,14 @@ (define* (open-ssh-session host #:key user port identity
            (authenticate-server* session host-key)
 
            ;; Authenticate against ~/.ssh/known_hosts.
-           (match (authenticate-server session)
-             ('ok #f)
-             (reason
-              (raise (formatted-message (G_ "failed to authenticate \
+           (when strict-host-key-check?
+             (match (authenticate-server session)
+               ('ok #f)
+               (reason
+                (raise (formatted-message (G_ "failed to authenticate \
 server at '~a': ~a")
-                                        (session-get session 'host)
-                                        reason)))))
+                                          (session-get session 'host)
+                                          reason))))))
 
        ;; Use public key authentication, via the SSH agent if it's available.
        (match (userauth-public-key/auto! session)

base-commit: 97fee203a5441f4d3004ccf43ed72fa3b51a7cdc
-- 
2.48.1