simplify private option ownership checks and make them more consistent

allowing private and home directory to be owned by different users
if the home directory is inside /home was thought to add flexibility, but the scenario is
maybe a bit too exotic, and ignoring it paves the way for a simplification

1 files changed, 26 insertions, 40 deletions

diff --git a/src/firejail/fs_home.c b/src/firejail/fs_home.c
index 2e8a8ad96..060152e55 100644
--- a/src/firejail/fs_home.c
+++ b/src/firejail/fs_home.c
@@ -250,9 +250,6 @@ void fs_private_homedir(void) {
         int xflag = store_xauthority();
         int aflag = store_asoundrc();
 
-        // home directory outside /home?
-        int oflag = (strncmp(homedir, "/home/", 6) != 0);
-
         uid_t u = getuid();
         gid_t g = getgid();
 
@@ -266,28 +263,22 @@ void fs_private_homedir(void) {
         int dst = safe_fd(homedir, O_PATH|O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC);
         if (dst == -1)
                 errExit("opening home directory");
-        if (u != 0) {
-                struct stat s;
-                // sometimes system users are assigned home directories like /, /proc, ...
-                // require that a home directory outside /home is owned by the user
-                if (oflag) {
-                        if (fstat(dst, &s) == -1)
-                                errExit("fstat");
-                        if (s.st_uid != u) {
-                                fprintf(stderr, "Error: cannot mount private directory:\n"
-                                        "Home directory is not owned by the current user\n");
-                                exit(1);
-                        }
-                }
-                // check if new home directory is owned by the user
-                if (fstat(src, &s) == -1)
-                        errExit("fstat");
-                if (s.st_uid != u) {
-                        fprintf(stderr, "Error: private directory is not owned by the current user\n");
-                        exit(1);
-                }
-                if ((S_IRWXU & s.st_mode) != S_IRWXU)
-                        fwarning("no full permissions on private directory\n");
+        // both mount source and target should be owned by the user
+        struct stat s;
+        if (fstat(src, &s) == -1)
+                errExit("fstat");
+        if (s.st_uid != u) {
+                fprintf(stderr, "Error: private directory is not owned by the current user\n");
+                exit(1);
+        }
+        if ((S_IRWXU & s.st_mode) != S_IRWXU)
+                fwarning("no full permissions on private directory\n");
+        if (fstat(dst, &s) == -1)
+                errExit("fstat");
+        if (s.st_uid != u) {
+                fprintf(stderr, "Error: cannot mount private directory:\n"
+                        "Home directory is not owned by the current user\n");
+                exit(1);
         }
         // mount via the links in /proc/self/fd
         char *proc_src, *proc_dst;
@@ -324,7 +315,7 @@ void fs_private_homedir(void) {
                         errExit("mounting home directory");
                 fs_logger("tmpfs /root");
         }
-        if (oflag) {
+        if (u == 0 || strncmp(homedir, "/home/", 6) != 0) {
                 // mask /home
                 if (arg_debug)
                         printf("Mounting a new /home directory\n");
@@ -546,9 +537,6 @@ void fs_private_home_list(void) {
         int xflag = store_xauthority();
         int aflag = store_asoundrc();
 
-        // home directory outside /home?
-        int oflag = (strncmp(homedir, "/home/", 6) != 0);
-
         uid_t uid = getuid();
         gid_t gid = getgid();
 
@@ -582,16 +570,14 @@ void fs_private_home_list(void) {
         int fd = safe_fd(homedir, O_PATH|O_DIRECTORY|O_NOFOLLOW|O_CLOEXEC);
         if (fd == -1)
                 errExit("opening home directory");
-        if (uid != 0 && oflag) {
-                // home directory outside /home should be owned by the user
-                struct stat s;
-                if (fstat(fd, &s) == -1)
-                        errExit("fstat");
-                if (s.st_uid != uid) {
-                        fprintf(stderr, "Error: cannot mount private directory:\n"
-                                "Home directory is not owned by the current user\n");
-                        exit(1);
-                }
+        // home directory should be owned by the user
+        struct stat s;
+        if (fstat(fd, &s) == -1)
+                errExit("fstat");
+        if (s.st_uid != uid) {
+                fprintf(stderr, "Error: cannot mount private directory:\n"
+                        "Home directory is not owned by the current user\n");
+                exit(1);
         }
         // mount using the file descriptor
         char *proc;
@@ -614,7 +600,7 @@ void fs_private_home_list(void) {
                 if (mount("tmpfs", "/root", "tmpfs", MS_NOSUID | MS_NODEV | MS_STRICTATIME,  "mode=700,gid=0") < 0)
                         errExit("mounting home directory");
         }
-        if (oflag) {
+        if (uid == 0 || strncmp(homedir, "/home/", 6) != 0) {
                 // mask /home
                 if (arg_debug)
                         printf("Mounting a new /home directory\n");