proc_pid_attr(5) — Linux manual page

NAME | DESCRIPTION | SEE ALSO | COLOPHON

proc_pid_attr(5)           File Formats Manual          proc_pid_attr(5)

NAME         top

       /proc/pid/attr/ - security-related attributes

DESCRIPTION         top

       /proc/pid/attr/
              The files in this directory provide an API for security
              modules.  The contents of this directory are files that
              can be read and written in order to set security-related
              attributes.  This directory was added to support SELinux,
              but the intention was that the API be general enough to
              support other security modules.  For the purpose of
              explanation, examples of how SELinux uses these files are
              provided below.

              This directory is present only if the kernel was
              configured with CONFIG_SECURITY.

       /proc/pid/attr/current (since Linux 2.6.0)
              The contents of this file represent the current security
              attributes of the process.

              In SELinux, this file is used to get the security context
              of a process.  Prior to Linux 2.6.11, this file could not
              be used to set the security context (a write was always
              denied), since SELinux limited process security
              transitions to execve(2) (see the description of
              /proc/pid/attr/exec, below).  Since Linux 2.6.11, SELinux
              lifted this restriction and began supporting "set"
              operations via writes to this node if authorized by
              policy, although use of this operation is only suitable
              for applications that are trusted to maintain any desired
              separation between the old and new security contexts.

              Prior to Linux 2.6.28, SELinux did not allow threads
              within a multithreaded process to set their security
              context via this node as it would yield an inconsistency
              among the security contexts of the threads sharing the
              same memory space.  Since Linux 2.6.28, SELinux lifted
              this restriction and began supporting "set" operations for
              threads within a multithreaded process if the new security
              context is bounded by the old security context, where the
              bounded relation is defined in policy and guarantees that
              the new security context has a subset of the permissions
              of the old security context.

              Other security modules may choose to support "set"
              operations via writes to this node.

       /proc/pid/attr/exec (since Linux 2.6.0)
              This file represents the attributes to assign to the
              process upon a subsequent execve(2).

              In SELinux, this is needed to support role/domain
              transitions, and execve(2) is the preferred point to make
              such transitions because it offers better control over the
              initialization of the process in the new security label
              and the inheritance of state.  In SELinux, this attribute
              is reset on execve(2) so that the new program reverts to
              the default behavior for any execve(2) calls that it may
              make.  In SELinux, a process can set only its own
              /proc/pid/attr/exec attribute.

       /proc/pid/attr/fscreate (since Linux 2.6.0)
              This file represents the attributes to assign to files
              created by subsequent calls to open(2), mkdir(2),
              symlink(2), and mknod(2)

              SELinux employs this file to support creation of a file
              (using the aforementioned system calls) in a secure state,
              so that there is no risk of inappropriate access being
              obtained between the time of creation and the time that
              attributes are set.  In SELinux, this attribute is reset
              on execve(2), so that the new program reverts to the
              default behavior for any file creation calls it may make,
              but the attribute will persist across multiple file
              creation calls within a program unless it is explicitly
              reset.  In SELinux, a process can set only its own
              /proc/pid/attr/fscreate attribute.

       /proc/pid/attr/keycreate (since Linux 2.6.18)
              If a process writes a security context into this file, all
              subsequently created keys (add_key(2)) will be labeled
              with this context.  For further information, see the
              kernel source file Documentation/security/keys/core.rst
              (or file Documentation/security/keys.txt between Linux 3.0
              and Linux 4.13, or Documentation/keys.txt before Linux
              3.0).

       /proc/pid/attr/prev (since Linux 2.6.0)
              This file contains the security context of the process
              before the last execve(2); that is, the previous value of
              /proc/pid/attr/current.

       /proc/pid/attr/socketcreate (since Linux 2.6.18)
              If a process writes a security context into this file, all
              subsequently created sockets will be labeled with this
              context.

SEE ALSO         top

       proc(5)

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02               proc_pid_attr(5)