Support scoping abstract unix sockets

Closes: #330
Signed-off-by: Rahul Sandhu <nvraxn@gmail.com>

Author: WavyEbuilder

bubblewrap.c

@@ -32,10 +32,15 @@
 #include <sys/signalfd.h>
 #include <sys/capability.h>
 #include <sys/prctl.h>
+#include <sys/syscall.h>
 #include <linux/sched.h>
 #include <linux/seccomp.h>
 #include <linux/filter.h>
 
+#ifdef HAVE_LANDLOCK_H
+#include <linux/landlock.h>
+#endif
+
 #include "utils.h"
 #include "network.h"
 #include "bind-mount.h"
@@ -92,6 +97,7 @@ static int opt_userns_fd = -1;
 static int opt_userns2_fd = -1;
 static int opt_pidns_fd = -1;
 static int opt_tmp_overlay_count = 0;
+static bool opt_scope_abstract_unix_sockets = false;
 static int next_perms = -1;
 static size_t next_size_arg = 0;
 static int next_overlay_src_count = 0;
@@ -373,6 +379,7 @@ usage (int ecode, FILE *out)
            "    --perms OCTAL                Set permissions of next argument (--bind-data, --file, etc.)\n"
            "    --size BYTES                 Set size of next argument (only for --tmpfs)\n"
            "    --chmod OCTAL PATH           Change permissions of PATH (must already exist)\n"
+           "    --scope-abstract-af-unix     Scope access to abstract unix sockets to within in the sandbox\n"
           );
   exit (ecode);
 }
@@ -2736,6 +2743,10 @@ parse_args_recurse (int          *argcp,
           argv += 2;
           argc -= 2;
         }
+      else if (strcmp (arg, "--scope-abstract-af-unix") == 0)
+        {
+          opt_scope_abstract_unix_sockets = true;
+        }
       else if (strcmp (arg, "--") == 0)
         {
           argv += 1;
@@ -2867,6 +2878,26 @@ namespace_ids_write (int    fd,
     }
 }
 
+#ifdef HAVE_LANDLOCK_H
+#ifndef landlock_create_ruleset
+static inline int
+landlock_create_ruleset (const struct landlock_ruleset_attr *attr,
+                         size_t                              size,
+                         uint32_t                            flags)
+{
+  return syscall (SYS_landlock_create_ruleset, attr, size, flags);
+}
+#endif
+
+#ifndef landlock_restrict_self
+static inline int
+landlock_restrict_self (int ruleset_fd, uint32_t flags)
+{
+  return syscall (SYS_landlock_restrict_self, ruleset_fd, flags);
+}
+#endif
+#endif
+
 int
 main (int    argc,
       char **argv)
@@ -3491,6 +3522,27 @@ main (int    argc,
         die ("creation of new user namespaces was not disabled as requested");
     }
 
+  if (opt_scope_abstract_unix_sockets)
+    {
+  #ifdef HAVE_LANDLOCK_H
+      static const struct landlock_ruleset_attr ruleset_attr = {
+        .scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET
+      };
+      const int abi = landlock_create_ruleset (NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);
+      if (abi < 0)
+        die_with_error ("failed to check Landlock compatibility");
+      if (abi < 6)
+        die ("supported kernel Landlock ABI too old, version 6 or above required");
+      const int ruleset_fd = landlock_create_ruleset (&ruleset_attr, sizeof (ruleset_attr), 0);
+      if (ruleset_fd < 0)
+        die_with_error ("failed to create Landlock ruleset");
+      if (landlock_restrict_self (ruleset_fd, 0) < 0)
+        die_with_error ("failed to enforce Landlock ruleset");
+  #else
+    die ("Landlock not available at compile time, cannot implement --scope-abstract-af-unix");
+  #endif
+    }
+
   /* All privileged ops are done now, so drop caps we don't need */
   drop_privs (!is_privileged, true);
 

bwrap.xml

@@ -617,6 +617,17 @@
         command line.  Please be careful to the order they are specified.
       </para></listitem>
     </varlistentry>
+    <varlistentry>
+      <term><option>--scope-abstract-af-unix</option></term>
+      <listitem><para>
+        Scope access to abstract unix sockets.  This option will prevent the newly
+        created sandbox from talking to any abstract unix sockets, including in the
+        current net namespace (i.e. in the absence of <option>--unshare-net</option>).
+
+        This has the same behaviour as LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET: see
+        <citerefentry><refentrytitle>landlock</refentrytitle><manvolnum>7</manvolnum></citerefentry> for details.
+      </para></listitem>
+    </varlistentry>
   </variablelist>
 </refsect1>
 

completions/bash/bwrap

@@ -15,6 +15,7 @@ _bwrap() {
 		--disable-userns
 		--help
 		--new-session
+		--scope-abstract-af-unix
 		--unshare-all
 		--unshare-cgroup
 		--unshare-cgroup-try

completions/zsh/_bwrap

@@ -60,6 +60,7 @@ _bwrap_args=(
     '--remount-ro[Remount DEST as readonly; does not recursively remount]:mount point to remount read-only:_files'
     '--ro-bind-try[Equal to --ro-bind but ignores non-existent SRC]:source:_files:destination:_files'
     '--ro-bind[Bind mount the host path SRC readonly on DEST]:source:_files:destination:_files'
+    '--scope-abstract-af-unix[Scope access to abstract unix sockets to within in the sandbox]'
     '--seccomp[Load and use seccomp rules from FD]: :_guard "[0-9]#" "file descriptor to read seccomp rules from"'
     '--setenv[Set an environment variable]:variable to set:_parameters -g "*export*":value of variable: :'
     '--size[Set size in bytes for next action argument]: :->after_size'

meson.build

@@ -57,6 +57,10 @@ if (
   ], language : 'c')
 endif
 
+if cc.check_header('linux/landlock.h')
+  add_project_arguments('-DHAVE_LANDLOCK_H', language : 'c')
+endif
+
 bash = find_program('bash', required : false)
 
 if get_option('python') == ''