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125 lines
3.1 KiB
Go
125 lines
3.1 KiB
Go
// Package cap
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// Copyright (c) 2019-21 Andrew G. Morgan <morgan@kernel.org>
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//
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// The cap and psx packages are licensed with a (you choose) BSD
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// 3-clause or GPL2. See LICENSE file for details.
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// [the Fully Capable site]: https://sites.google.com/site/fullycapable/
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package cap
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import (
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"errors"
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"sync"
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)
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// Value is the type of a single capability (or permission) bit.
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type Value uint
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// Flag is the type of one of the three Value dimensions held in a
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// Set. It is also used in the (*IAB).Fill() method for changing the
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// Bounding and Ambient Vectors.
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type Flag uint
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// Effective, Permitted, Inheritable are the three Flags of Values
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// held in a Set.
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const (
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Effective Flag = iota
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Permitted
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Inheritable
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)
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// String identifies a Flag value by its conventional "e", "p" or "i"
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// string abbreviation.
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func (f Flag) String() string {
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switch f {
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case Effective:
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return "e"
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case Permitted:
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return "p"
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case Inheritable:
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return "i"
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default:
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return "<Error>"
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}
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}
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// data holds a 32-bit slice of the compressed bitmaps of capability
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// sets as understood by the kernel.
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type data [Inheritable + 1]uint32
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// Set is an opaque capabilities container for a set of system
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// capbilities. It holds individually addressable capability Value's
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// for the three capability Flag's. See GetFlag() and SetFlag() for
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// how to adjust them individually, and Clear() and ClearFlag() for
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// how to do bulk operations.
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//
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// For admin tasks associated with managing namespace specific file
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// capabilities, Set can also support a namespace-root-UID value which
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// defaults to zero. See GetNSOwner() and SetNSOwner().
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type Set struct {
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// mu protects all other members of a Set.
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mu sync.RWMutex
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// flat holds Flag Value bitmaps for all capabilities
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// associated with this Set.
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flat []data
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// Linux specific
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nsRoot int
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}
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// Various known kernel magic values.
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const (
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kv1 = 0x19980330 // First iteration of process capabilities (32 bits).
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kv2 = 0x20071026 // First iteration of process and file capabilities (64 bits) - deprecated.
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kv3 = 0x20080522 // Most recently supported process and file capabilities (64 bits).
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)
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var (
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// startUp protects setting of the following values: magic,
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// words, maxValues.
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startUp sync.Once
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// magic holds the preferred magic number for the kernel ABI.
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magic uint32
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// words holds the number of uint32's associated with each
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// capability Flag for this session.
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words int
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// maxValues holds the number of bit values that are named by
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// the running kernel. This is generally expected to match
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// ValueCount which is autogenerated at packaging time.
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maxValues uint
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)
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type header struct {
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magic uint32
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pid int32
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}
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// defines from uapi/linux/prctl.h
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const (
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prCapBSetRead = 23
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prCapBSetDrop = 24
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)
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// NewSet returns an empty capability set.
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func NewSet() *Set {
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startUp.Do(cInit)
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return &Set{
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flat: make([]data, words),
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}
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}
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// ErrBadSet indicates a nil pointer was used for a *Set, or the
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// request of the Set is invalid in some way.
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var ErrBadSet = errors.New("bad capability set")
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// good confirms that c looks valid.
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func (c *Set) good() error {
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if c == nil || len(c.flat) == 0 {
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return ErrBadSet
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}
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return nil
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}
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