diff options
Diffstat (limited to 'gnu/build/linux-container.scm')
| -rw-r--r-- | gnu/build/linux-container.scm | 111 |
1 files changed, 74 insertions, 37 deletions
diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm index 345ce2de08..51f04bc249 100644 --- a/gnu/build/linux-container.scm +++ b/gnu/build/linux-container.scm @@ -189,7 +189,10 @@ for the process." (remount-read-only "/")))) (define* (initialize-user-namespace pid host-uids - #:key (guest-uid 0) (guest-gid 0)) + #:key + (host-uid (getuid)) + (host-gid (getgid)) + (guest-uid 0) (guest-gid 0)) "Configure the user namespace for PID. HOST-UIDS specifies the number of host user identifiers to map into the user namespace. GUEST-UID and GUEST-GID specify the first UID (respectively GID) that host UIDs (respectively GIDs) @@ -200,24 +203,21 @@ map to in the namespace." (define (scope file) (string-append proc-dir file)) - (let ((uid (getuid)) - (gid (getgid))) - - ;; Only root can write to the gid map without first disabling the - ;; setgroups syscall. - (unless (and (zero? uid) (zero? gid)) - (call-with-output-file (scope "/setgroups") - (lambda (port) - (display "deny" port)))) - - ;; Map the user/group that created the container to the root user - ;; within the container. - (call-with-output-file (scope "/uid_map") + ;; Only root can write to the gid map without first disabling the + ;; setgroups syscall. + (unless (and (zero? host-uid) (zero? host-gid)) + (call-with-output-file (scope "/setgroups") (lambda (port) - (format port "~d ~d ~d" guest-uid uid host-uids))) - (call-with-output-file (scope "/gid_map") - (lambda (port) - (format port "~d ~d ~d" guest-gid gid host-uids))))) + (display "deny" port)))) + + ;; Map the user/group that created the container to the root user + ;; within the container. + (call-with-output-file (scope "/uid_map") + (lambda (port) + (format port "~d ~d ~d" guest-uid host-uid host-uids))) + (call-with-output-file (scope "/gid_map") + (lambda (port) + (format port "~d ~d ~d" guest-gid host-gid host-uids)))) (define (namespaces->bit-mask namespaces) "Return the number suitable for the 'flags' argument of 'clone' that @@ -238,12 +238,14 @@ corresponds to the symbols in NAMESPACES." #:key (guest-uid 0) (guest-gid 0) (populate-file-system (const #t)) (loopback-network? #t) + (lock-mounts? #t) writable-root?) "Run THUNK in a new container process and return its PID. ROOT specifies the root directory for the container. MOUNTS is a list of <file-system> objects that specify file systems to mount inside the container. NAMESPACES is a list of symbols that correspond to the possible Linux namespaces: mnt, -ipc, uts, user, and net. +ipc, uts, user, and net. When LOCK-MOUNTS? is true, arrange so that none of +MOUNTS can be unmounted or remounted individually from within THUNK. When LOOPBACK-NETWORK? is true and 'net is amount NAMESPACES, set up the loopback device (\"lo\") and a minimal /etc/hosts. @@ -303,6 +305,28 @@ that host UIDs (respectively GIDs) map to in the namespace." ;; cannot be 'read' so they shouldn't be written as is. (write args child) (primitive-exit 3)))) + + (when (and lock-mounts? + (memq 'mnt namespaces) + (memq 'user namespaces)) + ;; Create a new mount namespace owned by a new user + ;; namespace to "lock" together previous mounts, such that + ;; they cannot be unmounted or remounted separately--see + ;; mount_namespaces(7). + ;; + ;; Note: at this point, the process is single-threaded (no + ;; GC mark threads, no finalization thread, etc.) which is + ;; why unshare(CLONE_NEWUSER) can be used. + (let ((uid (getuid)) (gid (getgid))) + (unshare (logior CLONE_NEWUSER CLONE_NEWNS)) + (when (file-exists? "/proc/self") + (initialize-user-namespace (getpid) + host-uids + #:host-uid uid + #:host-gid gid + #:guest-uid guest-uid + #:guest-gid guest-gid)))) + ;; TODO: Manage capabilities. (write 'ready child) (close-port child) @@ -365,6 +389,7 @@ if there are no child processes left." (define* (call-with-container mounts thunk #:key (namespaces %namespaces) (host-uids 1) (guest-uid 0) (guest-gid 0) + (lock-mounts? #t) (relayed-signals (list SIGINT SIGTERM)) (child-is-pid1? #t) (populate-file-system (const #t)) @@ -449,6 +474,7 @@ load path must be adjusted as needed." (call-with-temporary-directory (lambda (root) (let ((pid (run-container root mounts namespaces host-uids thunk* + #:lock-mounts? lock-mounts? #:guest-uid guest-uid #:guest-gid guest-gid #:populate-file-system populate-file-system @@ -469,24 +495,35 @@ return the exit status, an integer as returned by 'waitpid'." (0 (call-with-clean-exit (lambda () - (for-each (lambda (ns) - (let ((source (namespace-file (getpid) ns)) - (target (namespace-file pid ns))) - ;; Joining the namespace that the process already - ;; belongs to would throw an error so avoid that. - ;; XXX: This /proc interface leads to TOCTTOU. - (unless (string=? (readlink source) (readlink target)) - (call-with-input-file source - (lambda (current-ns-port) - (call-with-input-file target - (lambda (new-ns-port) - (setns (fileno new-ns-port) 0)))))))) - ;; It's important that the user namespace is joined first, - ;; so that the user will have the privileges to join the - ;; other namespaces. Furthermore, it's important that the - ;; mount namespace is joined last, otherwise the /proc mount - ;; point would no longer be accessible. - '("user" "ipc" "uts" "net" "pid" "mnt")) + ;; First, determine the user namespace that owns the pid namespace and + ;; join that user namespace (the assumption is that it also owns all + ;; the other namespaces). It's important that the user namespace is + ;; joined first, so that the user will have the privileges to join the + ;; other namespaces. + (let* ((pid-ns (open-fdes (namespace-file pid "pid") + (logior O_CLOEXEC O_RDONLY))) + (user-ns (get-user-ns pid-ns))) + (close-fdes pid-ns) + (unless (equal? (stat user-ns) + (stat (namespace-file (getpid) "user"))) + (setns user-ns 0)) + (close-fdes user-ns) + + ;; Then join all the remaining namespaces. + (for-each (lambda (ns) + (let ((source (namespace-file (getpid) ns)) + (target (namespace-file pid ns))) + ;; Joining the namespace that the process already + ;; belongs to would throw an error so avoid that. + ;; XXX: This /proc interface leads to TOCTTOU. + (unless (string=? (readlink source) (readlink target)) + (call-with-input-file target + (lambda (new-ns-port) + (setns (fileno new-ns-port) 0)))))) + ;; It's important that the mount namespace is joined last, + ;; otherwise the /proc mount point would no longer be + ;; accessible. + '("ipc" "uts" "net" "pid" "mnt"))) (purify-environment) (chdir "/") |