homework: allow specifying a dir component in CIFS services

Allow specifying CIFS services in the format //host/service/subdir/… to
allow multiple homedirs on the same share, and not in the main dir of
the share.

All other backends allow placing the data store at arbitrary places,
let's allow this too for the CIFS backend. This is particularly useful
for testing.

5 files changed, 43 insertions, 7 deletions

diff --git a/docs/USER_RECORD.md b/docs/USER_RECORD.md
index 6b607dfd45..6710b00c0c 100644
--- a/docs/USER_RECORD.md
+++ b/docs/USER_RECORD.md
@@ -411,7 +411,9 @@ useful when `cifs` is used as storage mechanism for the user's home directory,
 see above.
 
 `cifsService` → A string indicating the Windows File Share service (CIFS) to
-mount as home directory of the user on login.
+mount as home directory of the user on login. Should be in format
+`//<host>/<service>/<directory/…>`. The directory part is optional. If missing
+the top-level directory of the CIFS share is used.
 
 `imagePath` → A string with an absolute file system path to the file, directory
 or block device to use for storage backing the home directory. If the `luks`
diff --git a/man/homectl.xml b/man/homectl.xml
index c2b1ec6c9b..f670566593 100644
--- a/man/homectl.xml
+++ b/man/homectl.xml
@@ -690,8 +690,11 @@
         <term><option>--cifs-service=</option><replaceable>SERVICE</replaceable></term>
 
         <listitem><para>Configures the Windows File Sharing (CIFS) domain and user to associate with the home
-        directory/user account, as well as the file share ("service") to mount as directory. The latter is used when
-        <literal>cifs</literal> storage is selected.</para></listitem>
+        directory/user account, as well as the file share ("service") to mount as directory. The latter is
+        used when <literal>cifs</literal> storage is selected. The file share should be specified in format
+        <literal>//<replaceable>host</replaceable>/<replaceable>share</replaceable>/<replaceable>directory/…</replaceable></literal>. The
+        directory part is optional — if not specified the home directory will be placed in the top-level
+        directory of the share.</para></listitem>
       </varlistentry>
 
       <varlistentry>
diff --git a/src/home/homework-cifs.c b/src/home/homework-cifs.c
index b920053163..55b8c2588d 100644
--- a/src/home/homework-cifs.c
+++ b/src/home/homework-cifs.c
@@ -7,6 +7,7 @@
 #include "fs-util.h"
 #include "homework-cifs.h"
 #include "homework-mount.h"
+#include "mkdir.h"
 #include "mount-util.h"
 #include "process-util.h"
 #include "stat-util.h"
@@ -18,6 +19,7 @@ int home_setup_cifs(
                 HomeSetupFlags flags,
                 HomeSetup *setup) {
 
+        _cleanup_free_ char *chost = NULL, *cservice = NULL, *cdir = NULL, *chost_and_service = NULL, *j = NULL;
         char **pw;
         int r;
 
@@ -38,6 +40,15 @@ int home_setup_cifs(
         if (!h->cifs_service)
                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "User record lacks CIFS service, refusing.");
 
+        r = parse_cifs_service(h->cifs_service, &chost, &cservice, &cdir);
+        if (r < 0)
+                return log_error_errno(r, "Failed parse CIFS service specification: %m");
+
+        /* Just the host and service part, without the directory */
+        chost_and_service = strjoin("//", chost, "/", cservice);
+        if (!chost_and_service)
+                return log_oom();
+
         r = home_unshare_and_mkdir();
         if (r < 0)
                 return r;
@@ -78,7 +89,7 @@ int home_setup_cifs(
                 if (r == 0) {
                         /* Child */
                         execl("/bin/mount", "/bin/mount", "-n", "-t", "cifs",
-                              h->cifs_service, HOME_RUNTIME_WORK_DIR,
+                              chost_and_service, HOME_RUNTIME_WORK_DIR,
                               "-o", options, NULL);
 
                         log_error_errno(errno, "Failed to execute mount: %m");
@@ -104,10 +115,23 @@ int home_setup_cifs(
         if (r < 0)
                 return r;
 
-        setup->root_fd = open(HOME_RUNTIME_WORK_DIR, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
+        if (cdir) {
+                j = path_join(HOME_RUNTIME_WORK_DIR, cdir);
+                if (!j)
+                        return log_oom();
+
+                if (FLAGS_SET(flags, HOME_SETUP_CIFS_MKDIR)) {
+                        r = mkdir_p(j, 0700);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to create CIFS subdirectory: %m");
+                }
+        }
+
+        setup->root_fd = open(j ?: HOME_RUNTIME_WORK_DIR, O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW);
         if (setup->root_fd < 0)
                 return log_error_errno(errno, "Failed to open home directory: %m");
 
+        setup->mount_suffix = TAKE_PTR(cdir);
         return 0;
 }
 
@@ -139,7 +163,7 @@ int home_activate_cifs(
 
         setup->root_fd = safe_close(setup->root_fd);
 
-        r = home_move_mount(NULL, hd);
+        r = home_move_mount(setup->mount_suffix, hd);
         if (r < 0)
                 return r;
 
@@ -171,7 +195,7 @@ int home_create_cifs(UserRecord *h, HomeSetup *setup, UserRecord **ret_home) {
                 return log_error_errno(errno, "Unable to detect whether /sbin/mount.cifs exists: %m");
         }
 
-        r = home_setup_cifs(h, 0, setup);
+        r = home_setup_cifs(h, HOME_SETUP_CIFS_MKDIR, setup);
         if (r < 0)
                 return r;
 
diff --git a/src/home/homework.c b/src/home/homework.c
index cfc0c945de..8ffed82742 100644
--- a/src/home/homework.c
+++ b/src/home/homework.c
@@ -365,6 +365,8 @@ int home_setup_done(HomeSetup *setup) {
         if (setup->do_drop_caches)
                 drop_caches_now();
 
+        setup->mount_suffix = mfree(setup->mount_suffix);
+
         return r;
 }
 
diff --git a/src/home/homework.h b/src/home/homework.h
index 1fa5a1e37a..08d97b8261 100644
--- a/src/home/homework.h
+++ b/src/home/homework.h
@@ -37,6 +37,8 @@ typedef struct HomeSetup {
 
         uint64_t partition_offset;
         uint64_t partition_size;
+
+        char *mount_suffix;           /* The directory to use as home dir is this path below /run/systemd/user-home-mount */
 } HomeSetup;
 
 typedef struct PasswordCache {
@@ -66,6 +68,9 @@ static inline bool password_cache_contains(const PasswordCache *cache, const cha
 /* Various flags for the operation of setting up a home directory */
 typedef enum HomeSetupFlags {
         HOME_SETUP_ALREADY_ACTIVATED = 1 << 0, /* Open an already activated home, rather than activate it afresh */
+
+        /* CIFS backend: */
+        HOME_SETUP_CIFS_MKDIR        = 1 << 1, /* Create CIFS subdir when missing */
 } HomeSetupFlags;
 
 int home_setup_done(HomeSetup *setup);