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package interfaces
import (
"bytes"
"fmt"
"sort"
"strings"
"github.com/snapcore/snapd/logger"
"github.com/snapcore/snapd/snap"
)
// SnapAppSet is a helper that provides information about executable elements of
// a snap. This currently includes snap apps and hooks.
type SnapAppSet struct {
info *snap.Info
components []*snap.ComponentInfo
}
// NewSnapAppSet returns a new SnapAppSet for the given snap.Info.
func NewSnapAppSet(info *snap.Info, components []*snap.ComponentInfo) (*SnapAppSet, error) {
for _, c := range components {
if c.Component.SnapName != info.SnapName() {
return nil, fmt.Errorf("internal error: snap %q does not own component %q", info.SnapName(), c.Component)
}
}
return &SnapAppSet{info: info, components: components}, nil
}
// Info returns the snap.Info that this SnapAppSet is based on.
func (a *SnapAppSet) Info() *snap.Info {
return a.info
}
// Components returns the components that this SnapAppSet was created with.
func (a *SnapAppSet) Components() []*snap.ComponentInfo {
return a.components
}
// InstanceName returns the instance name of the snap that this SnapAppSet is
// based on.
func (a *SnapAppSet) InstanceName() string {
return a.info.InstanceName()
}
// SecurityTagsForConnectedPlug returns the security tags for the given plug.
// These are derived from the security tags of the apps and hooks that are
// associated with the plug.
func (a *SnapAppSet) SecurityTagsForConnectedPlug(plug *ConnectedPlug) ([]string, error) {
return a.SecurityTagsForPlug(plug.plugInfo)
}
// SecurityTagsForPlug returns the security tags for the given plug. These are
// derived from the security tags of the apps and hooks that are associated with
// the plug.
func (a *SnapAppSet) SecurityTagsForPlug(plug *snap.PlugInfo) ([]string, error) {
if plug.Snap.InstanceName() != a.info.InstanceName() {
return nil, fmt.Errorf("internal error: plug %q is from snap %q, security tags can only be computed for processed target snap: %q", plug.Name, plug.Snap.InstanceName(), a.info.InstanceName())
}
apps := a.info.AppsForPlug(plug)
hooks := a.info.HooksForPlug(plug)
for _, component := range a.components {
hooks = append(hooks, component.HooksForPlug(plug)...)
}
tags := make([]string, 0, len(apps)+len(hooks))
for _, app := range apps {
tags = append(tags, app.SecurityTag())
}
for _, hook := range hooks {
tags = append(tags, hook.SecurityTag())
}
sort.Strings(tags)
return tags, nil
}
// SecurityTagsForConnectedSlot returns the security tags for the given slot. These
// are derived from the security tags of the apps and hooks that are associated
// with the slot.
func (a *SnapAppSet) SecurityTagsForConnectedSlot(slot *ConnectedSlot) ([]string, error) {
return a.SecurityTagsForSlot(slot.slotInfo)
}
// SecurityTagsForSlot returns the security tags for the given slot. These are
// derived from the security tags of the apps and hooks that are associated with
// the slot.
func (a *SnapAppSet) SecurityTagsForSlot(slot *snap.SlotInfo) ([]string, error) {
if slot.Snap.InstanceName() != a.info.InstanceName() {
return nil, fmt.Errorf("internal error: slot %q is from snap %q, security tags can only be computed for processed target snap: %q", slot.Name, slot.Snap.InstanceName(), a.info.InstanceName())
}
apps := a.info.AppsForSlot(slot)
hooks := a.info.HooksForSlot(slot)
tags := make([]string, 0, len(apps)+len(hooks))
for _, app := range apps {
tags = append(tags, app.SecurityTag())
}
for _, hook := range hooks {
tags = append(tags, hook.SecurityTag())
}
sort.Strings(tags)
return tags, nil
}
// Runnables returns a list of all runnables known by the app set.
func (a *SnapAppSet) Runnables() []snap.Runnable {
var runnables []snap.Runnable
for _, app := range a.info.Apps {
runnables = append(runnables, app.Runnable())
}
for _, hook := range a.info.Hooks {
runnables = append(runnables, hook.Runnable())
}
for _, component := range a.components {
for _, hook := range component.Hooks {
runnables = append(runnables, hook.Runnable())
}
}
return runnables
}
// labelExpr returns the specification of the apparmor label describing the
// given connected plug/slot. The result has one of three forms, depending on
// how apps are bound to the slot:
//
// - "snap.$snap_instance.$app" if there is exactly one app/hook bound
// - "snap.$snap_instance.{$app1,...$appN, $hook1...$hookN}" if there are
// some, but not all, apps/hooks bound
// - "snap.$snap_instance.*" if all apps/hooks are bound to the plug or slot
func labelExpr(connected interface {
AppSet() *SnapAppSet
Runnables() []snap.Runnable
}) string {
appSet := connected.AppSet()
runnables := connected.Runnables()
// all security tags are prefixed with snap.$snap_instance, we use this
// knowledge to build a pattern that will match against all of the connected
// runnables
prefix := fmt.Sprintf("snap.%s", appSet.InstanceName())
suffixes := make([]string, 0, len(runnables))
for _, r := range runnables {
suffix := strings.TrimPrefix(r.SecurityTag, prefix)
if suffix == r.SecurityTag {
logger.Noticef("security tag %q does not have expected prefix: %q", r.SecurityTag, prefix)
continue
}
suffixes = append(suffixes, suffix)
}
sort.Strings(suffixes)
var buf bytes.Buffer
fmt.Fprintf(&buf, `"%s`, prefix)
switch len(suffixes) {
case 0:
buf.WriteString(".")
case 1:
buf.WriteString(suffixes[0])
case len(appSet.Runnables()):
buf.WriteString(".*")
default:
buf.WriteByte('{')
for _, name := range suffixes {
buf.WriteString(name)
buf.WriteByte(',')
}
// remove trailing comma
buf.Truncate(buf.Len() - 1)
buf.WriteByte('}')
}
buf.WriteByte('"')
return buf.String()
}
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