interfaces/builtin: refine the content interface rules using $SLOT

interfaces/builtin/basedeclaration.go

@@ -204,9 +204,14 @@ slots:
       slot-snap-type:
         - app
         - gadget
+    allow-connection:
+      plug-attributes:
+        content: $SLOT(content)
     allow-auto-connection:
       plug-publisher-id:
         - $SLOT_PUBLISHER_ID
+      plug-attributes:
+        content: $SLOT(content)
   core-support:
     allow-installation:
       slot-snap-type:

interfaces/builtin/basedeclaration_test.go

@@ -220,11 +220,58 @@ plugs:
 }
 
 func (s *baseDeclSuite) TestAutoConnectionContent(c *C) {
-	// content will also depend for now AutoConnect(plug, slot)
 	// random snaps cannot connect with content
+	// (Sanitize* will now also block this)
 	cand := s.connectCand(c, "content", "", "")
 	err := cand.CheckAutoConnect()
 	c.Check(err, NotNil)
+
+	slotDecl1 := s.mockSnapDecl(c, "slot-snap", "slot-snap-id", "pub1", "")
+	plugDecl1 := s.mockSnapDecl(c, "plug-snap", "plug-snap-id", "pub1", "")
+	plugDecl2 := s.mockSnapDecl(c, "plug-snap", "plug-snap-id", "pub2", "")
+
+	// same publisher, same content
+	cand = s.connectCand(c, "stuff", `
+name: slot-snap
+slots:
+  stuff:
+    interface: content
+    content: mk1
+`, `
+name: plug-snap
+plugs:
+  stuff:
+    interface: content
+    content: mk1
+`)
+	cand.SlotSnapDeclaration = slotDecl1
+	cand.PlugSnapDeclaration = plugDecl1
+	err = cand.CheckAutoConnect()
+	c.Check(err, IsNil)
+
+	// different publisher, same content
+	cand.SlotSnapDeclaration = slotDecl1
+	cand.PlugSnapDeclaration = plugDecl2
+	err = cand.CheckAutoConnect()
+	c.Check(err, NotNil)
+
+	// same publisher, different content
+	cand = s.connectCand(c, "stuff", `name: slot-snap
+slots:
+  stuff:
+    interface: content
+    content: mk1
+`, `
+name: plug-snap
+plugs:
+  stuff:
+    interface: content
+    content: mk2
+`)
+	cand.SlotSnapDeclaration = slotDecl1
+	cand.PlugSnapDeclaration = plugDecl1
+	err = cand.CheckAutoConnect()
+	c.Check(err, NotNil)
 }
 
 func (s *baseDeclSuite) TestAutoConnectionLxdSupportOverride(c *C) {
@@ -499,6 +546,7 @@ func (s *baseDeclSuite) TestConnection(c *C) {
 	// case-by-case basis
 	noconnect := map[string]bool{
 		"bluez":                   true,
+		"content":                 true,
 		"docker":                  true,
 		"fwupd":                   true,
 		"location-control":        true,
@@ -594,3 +642,59 @@ func (s *baseDeclSuite) TestSanity(c *C) {
 		}
 	}
 }
+
+func (s *baseDeclSuite) TestConnectionContent(c *C) {
+	// we let connect explicitly as long as content matches (or is absent on both sides)
+
+	// random (Sanitize* will now also block this)
+	cand := s.connectCand(c, "content", "", "")
+	err := cand.Check()
+	c.Check(err, NotNil)
+
+	slotDecl1 := s.mockSnapDecl(c, "slot-snap", "slot-snap-id", "pub1", "")
+	plugDecl1 := s.mockSnapDecl(c, "plug-snap", "plug-snap-id", "pub1", "")
+	plugDecl2 := s.mockSnapDecl(c, "plug-snap", "plug-snap-id", "pub2", "")
+
+	// same publisher, same content
+	cand = s.connectCand(c, "stuff", `name: slot-snap
+slots:
+  stuff:
+    interface: content
+    content: mk1
+`, `
+name: plug-snap
+plugs:
+  stuff:
+    interface: content
+    content: mk1
+`)
+	cand.SlotSnapDeclaration = slotDecl1
+	cand.PlugSnapDeclaration = plugDecl1
+	err = cand.Check()
+	c.Check(err, IsNil)
+
+	// different publisher, same content
+	cand.SlotSnapDeclaration = slotDecl1
+	cand.PlugSnapDeclaration = plugDecl2
+	err = cand.Check()
+	c.Check(err, IsNil)
+
+	// same publisher, different content
+	cand = s.connectCand(c, "stuff", `
+name: slot-snap
+slots:
+  stuff:
+    interface: content
+    content: mk1
+`, `
+name: plug-snap
+plugs:
+  stuff:
+    interface: content
+    content: mk2
+`)
+	cand.SlotSnapDeclaration = slotDecl1
+	cand.PlugSnapDeclaration = plugDecl1
+	err = cand.Check()
+	c.Check(err, NotNil)
+}

interfaces/builtin/content.go

@@ -44,6 +44,10 @@ func (iface *ContentInterface) SanitizeSlot(slot *interfaces.Slot) error {
 	if iface.Name() != slot.Interface {
 		panic(fmt.Sprintf("slot is not of interface %q", iface))
 	}
+	content, ok := slot.Attrs["content"].(string)
+	if !ok || len(content) == 0 {
+		return fmt.Errorf("content slot must have a content attribute set")
+	}
 
 	// check that we have either a read or write path
 	rpath := iface.path(slot, "read")
@@ -68,6 +72,10 @@ func (iface *ContentInterface) SanitizePlug(plug *interfaces.Plug) error {
 	if iface.Name() != plug.Interface {
 		panic(fmt.Sprintf("plug is not of interface %q", iface))
 	}
+	content, ok := plug.Attrs["content"].(string)
+	if !ok || len(content) == 0 {
+		return fmt.Errorf("content plug must have a content attribute set")
+	}
 	target, ok := plug.Attrs["target"].(string)
 	if !ok || len(target) == 0 {
 		return fmt.Errorf("content plug must contain target path")
@@ -184,5 +192,6 @@ func (iface *ContentInterface) PermanentPlugSnippet(plug *interfaces.Plug, secur
 }
 
 func (iface *ContentInterface) AutoConnect(plug *interfaces.Plug, slot *interfaces.Slot) bool {
-	return plug.Attrs["content"] == slot.Attrs["content"]
+	// allow what declarations allowed
+	return true
 }

interfaces/builtin/content_test.go

@@ -46,6 +46,7 @@ version: 1.0
 slots:
  content-slot:
   interface: content
+  content: mycont
   read:
    - shared/read
 `
@@ -55,12 +56,28 @@ slots:
 	c.Assert(err, IsNil)
 }
 
+func (s *ContentSuite) TestSanitizeSlotNoContentLabel(c *C) {
+	const mockSnapYaml = `name: content-slot-snap
+version: 1.0
+slots:
+ content-slot:
+  interface: content
+  read:
+   - shared/read
+`
+	info := snaptest.MockInfo(c, mockSnapYaml, nil)
+	slot := &interfaces.Slot{SlotInfo: info.Slots["content-slot"]}
+	err := s.iface.SanitizeSlot(slot)
+	c.Assert(err, ErrorMatches, `content slot must have a content attribute set`)
+}
+
 func (s *ContentSuite) TestSanitizeSlotNoPaths(c *C) {
 	const mockSnapYaml = `name: content-slot-snap
 version: 1.0
 slots:
  content-slot:
   interface: content
+  content: mycont
 `
 	info := snaptest.MockInfo(c, mockSnapYaml, nil)
 	slot := &interfaces.Slot{SlotInfo: info.Slots["content-slot"]}
@@ -74,6 +91,7 @@ version: 1.0
 slots:
  content-slot:
   interface: content
+  content: mycont
   read: []
   write: []
 `
@@ -83,12 +101,13 @@ slots:
 	c.Assert(err, ErrorMatches, "read or write path must be set")
 }
 
-func (s *ContentSuite) TestSanitizeSlotHasRealtivePath(c *C) {
+func (s *ContentSuite) TestSanitizeSlotHasRelativePath(c *C) {
 	const mockSnapYaml = `name: content-slot-snap
 version: 1.0
 slots:
  content-slot:
   interface: content
+  content: mycont
 `
 	for _, rw := range []string{"read: [../foo]", "write: [../bar]"} {
 		info := snaptest.MockInfo(c, mockSnapYaml+"  "+rw, nil)
@@ -104,6 +123,7 @@ version: 1.0
 plugs:
  content-plug:
   interface: content
+  content: mycont
   target: import
 `
 	info := snaptest.MockInfo(c, mockSnapYaml, nil)
@@ -112,12 +132,27 @@ plugs:
 	c.Assert(err, IsNil)
 }
 
+func (s *ContentSuite) TestSanitizePlugNoContentLabel(c *C) {
+	const mockSnapYaml = `name: content-slot-snap
+version: 1.0
+plugs:
+ content-plug:
+  interface: content
+  target: import
+`
+	info := snaptest.MockInfo(c, mockSnapYaml, nil)
+	plug := &interfaces.Plug{PlugInfo: info.Plugs["content-plug"]}
+	err := s.iface.SanitizePlug(plug)
+	c.Assert(err, ErrorMatches, `content plug must have a content attribute set`)
+}
+
 func (s *ContentSuite) TestSanitizePlugSimpleNoTarget(c *C) {
 	const mockSnapYaml = `name: content-slot-snap
 version: 1.0
 plugs:
  content-plug:
   interface: content
+  content: mycont
 `
 	info := snaptest.MockInfo(c, mockSnapYaml, nil)
 	plug := &interfaces.Plug{PlugInfo: info.Plugs["content-plug"]}
@@ -131,6 +166,7 @@ version: 1.0
 plugs:
  content-plug:
   interface: content
+  content: mycont
   target: ../foo
 `
 	info := snaptest.MockInfo(c, mockSnapYaml, nil)