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Published: Aug 25, 2021 License: GPL-3.0 Imports: 22 Imported by: 0



Package apparmor contains primitives for working with apparmor.



Package apparmor implements integration between snappy and ubuntu-core-launcher around apparmor.

Snappy creates apparmor profiles for each application (for each snap) present in the system. Upon each execution of ubuntu-core-launcher application process is launched under the profile. Prior to that the profile must be parsed, compiled and loaded into the kernel using the support tool "apparmor_parser".

Each apparmor profile contains a simple <header><content><footer> structure. The header specifies the profile name that the launcher will use to launch a process under this profile. Snappy uses "abstract identifiers" as profile names.

The actual profiles are stored in /var/lib/snappy/apparmor/profiles.

NOTE: A systemd job (apparmor.service) loads all snappy-specific apparmor profiles into the kernel during the boot process.



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func GenWritableFileProfile

func GenWritableFileProfile(emit func(f string, args ...interface{}), path string, assumedPrefixDepth int)

GenWritableFileProfile writes a profile for snap-update-ns for making given file writable.

func GenWritableMimicProfile

func GenWritableMimicProfile(emit func(f string, args ...interface{}), path string, assumedPrefixDepth int)

GenWritableMimicProfile generates apparmor rules for a writable mimic at the given path.

func GenWritableProfile

func GenWritableProfile(emit func(f string, args ...interface{}), path string, assumedPrefixDepth int)

GenWritableProfile generates a profile for snap-update-ns for making given directory writable.

func LoadedProfiles

func LoadedProfiles() ([]string, error)

LoadedProfiles interrogates the kernel and returns a list of loaded apparmor profiles.

Snappy manages apparmor profiles named "snap.*". Other profiles might exist on the system (via snappy dimension) and those are filtered-out.

func MockIsHomeUsingNFS

func MockIsHomeUsingNFS(new func() (bool, error)) (restore func())

MockIsHomeUsingNFS mocks the real implementation of osutil.IsHomeUsingNFS. This is exported so that other packages that indirectly interact with AppArmor backend can mock isHomeUsingNFS.

func ValidateNoAppArmorRegexp

func ValidateNoAppArmorRegexp(s string) error

ValidateNoAppArmorRegexp will check that the given string does not contain AppArmor regular expressions (AARE), double quotes or \0.


type Backend

type Backend struct {
	// contains filtered or unexported fields

Backend is responsible for maintaining apparmor profiles for snaps and parts of snapd.

func (*Backend) Initialize

func (b *Backend) Initialize(opts *interfaces.SecurityBackendOptions) error

Initialize prepares customized apparmor policy for snap-confine.

func (*Backend) Name

func (b *Backend) Name() interfaces.SecuritySystem

Name returns the name of the backend.

func (*Backend) NewSpecification

func (b *Backend) NewSpecification() interfaces.Specification

NewSpecification returns a new, empty apparmor specification.

func (*Backend) Remove

func (b *Backend) Remove(snapName string) error

Remove removes and unloads apparmor profiles of a given snap.

func (*Backend) RemoveLate

func (b *Backend) RemoveLate(snapName string, rev snap.Revision, typ snap.Type) error

func (*Backend) SandboxFeatures

func (b *Backend) SandboxFeatures() []string

SandboxFeatures returns the list of apparmor features supported by the kernel.

func (*Backend) Setup

Setup creates and loads apparmor profiles specific to a given snap. The snap can be in developer mode to make security violations non-fatal to the offending application process.

This method should be called after changing plug, slots, connections between them or application present in the snap.

func (*Backend) SetupMany

func (b *Backend) SetupMany(snaps []*snap.Info, confinement func(snapName string) interfaces.ConfinementOptions, repo *interfaces.Repository, tm timings.Measurer) []error

SetupMany creates and loads apparmor profiles for multiple snaps. The snaps can be in developer mode to make security violations non-fatal to the offending application process. SetupMany tries to recreate all profiles without interrupting on errors, but collects and returns them all.

This method is useful mainly for regenerating profiles.

type Specification

type Specification struct {
	// contains filtered or unexported fields

Specification assists in collecting apparmor entries associated with an interface.

func (*Specification) AddConnectedPlug

func (spec *Specification) AddConnectedPlug(iface interfaces.Interface, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error

AddConnectedPlug records apparmor-specific side-effects of having a connected plug.

func (*Specification) AddConnectedSlot

func (spec *Specification) AddConnectedSlot(iface interfaces.Interface, plug *interfaces.ConnectedPlug, slot *interfaces.ConnectedSlot) error

AddConnectedSlot records apparmor-specific side-effects of having a connected slot.

func (*Specification) AddDeduplicatedSnippet

func (spec *Specification) AddDeduplicatedSnippet(snippet string)

AddDeduplicatedSnippet adds a new apparmor snippet to all applications and hooks using the interface.

Certain combinations of snippets may be computationally expensive for apparmor_parser in its de-duplication step. This function lets snapd perform de-duplication of identical rules at the potential cost of a somewhat more complex auditing process of the text of generated apparmor profile. Identical mount rules should typically use this, but this function can also be used to avoid repeated rules that inhibit auditability.

func (*Specification) AddLayout

func (spec *Specification) AddLayout(si *snap.Info)

AddLayout adds apparmor snippets based on the layout of the snap.

The per-snap snap-update-ns profiles are composed via a template and snippets for the snap. The snippets may allow (depending on the snippet): - mount profiles via the content interface - creating missing mount point directories under $SNAP* (the 'tree'

of permissions is needed for SecureMkDirAll that uses
open(..., O_NOFOLLOW) and mkdirat() using the resulting file descriptor)

- creating a placeholder directory in /tmp/.snap/ in the per-snap mount

namespace to support writable mimic which uses tmpfs and bind mount to
poke holes in arbitrary read-only locations

- mounting/unmounting any part of $SNAP into placeholder directory - mounting/unmounting tmpfs over the original $SNAP/** location - mounting/unmounting from placeholder back to $SNAP/** (for reconstructing

the data)

Importantly, the above mount operations are happening within the per-snap mount namespace.

func (*Specification) AddOvername

func (spec *Specification) AddOvername(si *snap.Info)

AddOvername adds AppArmor snippets allowing remapping of snap directories for parallel installed snaps

Specifically snap-update-ns will apply the following bind mounts - /snap/foo_bar -> /snap/foo - /var/snap/foo_bar -> /var/snap/foo - /home/joe/snap/foo_bar -> /home/joe/snap/foo

func (*Specification) AddParametricSnippet

func (spec *Specification) AddParametricSnippet(templateFragment []string, value string)

AddParametricSnippet adds a new apparmor snippet both de-duplicated and optimized for the parser.

Conceptually the function takes a parametric template and a single value to remember. The resulting snippet text is a single entry resulting from the expanding the template and all the unique values observed, in the order they were observed.

The template is expressed as a slice of strings, with the parameter automatically injected between any two of them, or in the special case of only one fragment, after that fragment.

The resulting expansion depends on the number of values seen. If only one value is seen the resulting snippet is just the plain string one would expect if no parametric optimization had taken place. If more than one distinct value was seen then the resulting apparmor rule uses alternation syntax {param1,param2,...,paramN} which has better compilation time and memory complexity as compared to a set of naive expansions of the full snippet one after another.

For example the code:

AddParametricSnippet([]string{"/dev/", "rw,"}, "sda1")
AddParametricSnippet([]string{"/dev/", "rw,"}, "sda3")
AddParametricSnippet([]string{"/dev/", "rw,"}, "sdb2")

Results in a single apparmor rule:

"/dev/{sda1,sda3,sdb2} rw,"

This function should be used whenever the apparmor template features more than one use of "**" syntax (which represent arbitrary many directories or files) and a variable component, like a device name or similar. Repeated instances of this pattern require exponential memory when compiled with apparmor_parser -O no-expr-simplify.

func (*Specification) AddPermanentPlug

func (spec *Specification) AddPermanentPlug(iface interfaces.Interface, plug *snap.PlugInfo) error

AddPermanentPlug records apparmor-specific side-effects of having a plug.

func (*Specification) AddPermanentSlot

func (spec *Specification) AddPermanentSlot(iface interfaces.Interface, slot *snap.SlotInfo) error

AddPermanentSlot records apparmor-specific side-effects of having a slot.

func (*Specification) AddSnippet

func (spec *Specification) AddSnippet(snippet string)

AddSnippet adds a new apparmor snippet to all applications and hooks using the interface.

func (*Specification) AddUpdateNS

func (spec *Specification) AddUpdateNS(snippet string)

AddUpdateNS adds a new apparmor snippet for the snap-update-ns program.

func (*Specification) AddUpdateNSf

func (spec *Specification) AddUpdateNSf(f string, args ...interface{})

AddUpdateNSf formats and adds a new apparmor snippet for the snap-update-ns program.

func (*Specification) SecurityTags

func (spec *Specification) SecurityTags() []string

SecurityTags returns a list of security tags which have a snippet.

func (*Specification) SetSuppressHomeIx

func (spec *Specification) SetSuppressHomeIx()

SetSuppressHomeIx records suppression of the ix rules for the home interface.

func (*Specification) SetSuppressPtraceTrace

func (spec *Specification) SetSuppressPtraceTrace()

SetSuppressPtraceTrace to request explicit ptrace deny rules

func (*Specification) SetUsesPtraceTrace

func (spec *Specification) SetUsesPtraceTrace()

SetUsesPtraceTrace records when to omit explicit ptrace deny rules.

func (*Specification) SnippetForTag

func (spec *Specification) SnippetForTag(tag string) string

SnippetForTag returns a combined snippet for given security tag with individual snippets joined with the newline character. Empty string is returned for non-existing security tag.

func (*Specification) Snippets

func (spec *Specification) Snippets() map[string][]string

Snippets returns a deep copy of all the added application snippets.

func (*Specification) SuppressHomeIx

func (spec *Specification) SuppressHomeIx() bool

SuppressHomeIx returns whether the ix rules of the home interface should be suppressed.

func (*Specification) SuppressPtraceTrace

func (spec *Specification) SuppressPtraceTrace() bool

SuppressPtraceTrace returns whether ptrace should be suppressed as dictated by any of the interfaces in the spec.

func (*Specification) UpdateNS

func (spec *Specification) UpdateNS() []string

UpdateNS returns a deep copy of all the added snap-update-ns snippets.

func (*Specification) UpdateNSIndexOf

func (spec *Specification) UpdateNSIndexOf(snippet string) (idx int, ok bool)

UpdateNSIndexOf returns the index of a previously added snippet.

func (*Specification) UsesPtraceTrace

func (spec *Specification) UsesPtraceTrace() bool

UsesPtraceTrace returns whether ptrace is being used by any of the interfaces in the spec.

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