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Closes: https://github.com/landlock-lsm/linux/issues/7 Problem ======= Abstract unix sockets are used for local inter-process communications independent of the filesystem. Currently, a sandboxed process can connect to a socket outside of the sandboxed environment, since Landlock has no restriction for connecting to an abstract socket address(see more details in [1,2]). Access to such sockets for a sandboxed process should be scoped the same way ptrace is limited. [1] https://lore.kernel.org/all/20231023.ahphah4Wii4v@digikod.net/ [2] https://lore.kernel.org/all/20231102.MaeWaepav8nu@digikod.net/ Solution ======== To solve this issue, we extend the user space interface by adding a new "scoped" field to Landlock ruleset attribute structure. This field can contains different rights to restrict different functionalities. For abstract unix sockets, we introduce "LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET" field to specify that a ruleset will deny any connection from within the sandbox domain to its parent (i.e. any parent sandbox or non-sandbox processes). Example ======= Starting a listening socket with socat(1): socat abstract-listen:mysocket - Starting a sandboxed shell from $HOME with samples/landlock/sandboxer: LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="a" ./sandboxer /bin/bash If we try to connect to the listening socket, the connection would be refused. socat - abstract-connect:mysocket --> fails Notes of Implementation ======================= * Using the "scoped" field provides enough compatibility and flexibility to extend the scoping mechanism for other IPCs(e.g. signals). * To access the domain of a socket, we use its credentials of the file's FD which point to the credentials of the process that created the socket. (see more details in [3]). Cases where the process using the socket has a different domain than the process created it are covered in the unix_sock_special_cases test. [3] https://lore.kernel.org/outreachy/Zmi8Ydz4Z6tYtpY1@tahera-OptiPlex-5000/T/#m8cdf33180d86c7ec22932e2eb4ef7dd4fc94c792 Thanks to Mickaël Salaün and Paul Moore for guiding me through this implementation. Previous Versions ================= v6: https://lore.kernel.org/all/Zn32CYZiu7pY+rdI@tahera-OptiPlex-5000/ and https://lore.kernel.org/all/Zn32KKIJrY7Zi51K@tahera-OptiPlex-5000/ v5: https://lore.kernel.org/all/ZnSZnhGBiprI6FRk@tahera-OptiPlex-5000/ v4: https://lore.kernel.org/all/ZnNcE3ph2SWi1qmd@tahera-OptiPlex-5000/ v3: https://lore.kernel.org/all/ZmJJ7lZdQuQop7e5@tahera-OptiPlex-5000/ v2: https://lore.kernel.org/all/ZgX5TRTrSDPrJFfF@tahera-OptiPlex-5000/ v1: https://lore.kernel.org/all/ZgXN5fi6A1YQKiAQ@tahera-OptiPlex-5000/ Tahera Fahimi (4): Landlock: Add abstract unix socket connect restriction selftests/landlock: Abstract unix socket restriction tests samples/landlock: Support abstract unix socket restriction documentation/landlock: Adding scoping mechanism documentation Documentation/userspace-api/landlock.rst | 23 +- include/uapi/linux/landlock.h | 29 + samples/landlock/sandboxer.c | 25 +- security/landlock/limits.h | 3 + security/landlock/ruleset.c | 7 +- security/landlock/ruleset.h | 23 +- security/landlock/syscalls.c | 14 +- security/landlock/task.c | 112 +++ tools/testing/selftests/landlock/base_test.c | 2 +- .../testing/selftests/landlock/ptrace_test.c | 867 ++++++++++++++++++ 10 files changed, 1088 insertions(+), 17 deletions(-)