Add more methods for converting to/from sender IDs

spec/senderid.go

@@ -31,10 +31,19 @@
 // StoreSenderIDFromPublicID is a function to store the mxid_mapping after receiving a join event over federation.
 type StoreSenderIDFromPublicID func(ctx context.Context, senderID SenderID, userID string, id RoomID) error
 
+// Create a new sender ID from a private room key
 func SenderIDFromPseudoIDKey(key ed25519.PrivateKey) SenderID {
 	return SenderID(Base64Bytes(key.Public().(ed25519.PublicKey)).Encode())
 }
 
+// Create a new sender ID from a user ID
+func SenderIDFromUserID(user UserID) SenderID {
+	return SenderID(user.String())
+}
+
+// Decodes this sender ID as base64, i.e. returns the raw bytes of the
+// pseudo ID used to create this SenderID, assuming this SenderID was made
+// using a pseudo ID.
 func (s SenderID) RawBytes() (res Base64Bytes, err error) {
 	err = res.Decode(string(s))
 	if err != nil {
@@ -43,13 +52,41 @@
 	return res, nil
 }
 
+// Returns true if this SenderID was made using a user ID
 func (s SenderID) IsUserID() bool {
 	// Key is base64, @ is not a valid base64 char
 	// So if string starts with @, then this sender ID must
 	// be a user ID
 	return string(s)[0] == '@'
 }
 
+// Returns true if this SenderID was made using a pseudo ID
 func (s SenderID) IsPseudoID() bool {
 	return !s.IsUserID()
 }
+
+// Returns the non-nil UserID used to create this SenderID, or nil
+// if this SenderID was not created using a UserID
+func (s SenderID) ToUserID() *UserID {
+	if s.IsUserID() {
+		uID, _ := NewUserID(string(s), true)
+		return uID
+	}
+
+	return nil
+}
+
+// Returns the non-nil room public key (pseudo ID) used to create this
+// SenderID, or nil if this SenderID was not created using a pseudo ID
+func (s SenderID) ToPseudoID() *ed25519.PublicKey {
+	if s.IsPseudoID() {
+		decoded, err := s.RawBytes()
+		if err != nil {
+			return nil
+		}
+		key := ed25519.PublicKey([]byte(decoded))
+		return &key
+	}
+
+	return nil
+}

spec/senderid_test.go

@@ -0,0 +1,77 @@
+package spec
+
+import (
+	"crypto/ed25519"
+	"reflect"
+	"testing"
+)
+
+func TestUserIDSenderIDs(t *testing.T) {
+	tests := map[string]UserID{
+		"basic":                    NewUserIDOrPanic("@localpart:domain", false),
+		"extensive_local":          NewUserIDOrPanic("@abcdefghijklmnopqrstuvwxyz0123456789._=-/:domain", false),
+		"extensive_local_historic": NewUserIDOrPanic("@!\"#$%&'()*+,-./0123456789;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~:domain", true),
+		"domain_with_port":         NewUserIDOrPanic("@localpart:domain.org:80", false),
+		"minimum_id":               NewUserIDOrPanic("@a:1", false),
+	}
+
+	for name, userID := range tests {
+		t.Run(name, func(t *testing.T) {
+			senderID := SenderIDFromUserID(userID)
+
+			if string(senderID) != userID.String() {
+				t.Fatalf("Created sender ID did not match user ID string: senderID %s for user ID %s", string(senderID), userID.String())
+			}
+			if !senderID.IsUserID() {
+				t.Fatalf("IsUserID returned false for user ID: %s", userID.String())
+			}
+			if senderID.IsPseudoID() {
+				t.Fatalf("IsPseudoID returned true for user ID: %s", userID.String())
+			}
+			returnedUserID := senderID.ToUserID()
+			if returnedUserID == nil {
+				t.Fatalf("ToUserID returned nil value")
+			}
+			if !reflect.DeepEqual(userID, *returnedUserID) {
+				t.Fatalf("ToUserID returned different user ID than one used to created sender ID\ncreated with %s\nreturned %s", userID, *returnedUserID)
+			}
+			roomKey := senderID.ToPseudoID()
+			if roomKey != nil {
+				t.Fatalf("ToPseudoID returned non-nil value for user ID: %s, returned %s", userID.String(), roomKey)
+			}
+		})
+	}
+}
+
+func TestPseudoIDSenderIDs(t *testing.T) {
+	// Generate key from all zeroes seed
+	testKeySeed := make([]byte, 32)
+	testKey := ed25519.NewKeyFromSeed(testKeySeed)
+
+	t.Run("test pseudo ID", func(t *testing.T) {
+		senderID := SenderIDFromPseudoIDKey(testKey)
+		testPubkey := testKey.Public()
+		expectedSenderIDString := Base64Bytes(testPubkey.(ed25519.PublicKey)).Encode()
+
+		if string(senderID) != expectedSenderIDString {
+			t.Fatalf("Created sender ID did not match provided key: created sender ID %s, expected: %s", string(senderID), expectedSenderIDString)
+		}
+		if !senderID.IsPseudoID() {
+			t.Fatalf("IsPseudoID returned false for pseudo ID sender ID")
+		}
+		if senderID.IsUserID() {
+			t.Fatalf("IsUserID returned true for pseudo ID sender ID")
+		}
+		returnedKey := senderID.ToPseudoID()
+		if returnedKey == nil {
+			t.Fatal("ToPseudoID returned nil")
+		}
+		if !reflect.DeepEqual(testPubkey, *returnedKey) {
+			t.Fatalf("ToPseudoID returned different key to the one used to create the sender ID:\ncreated with %v\nreturned %v", testPubkey, *returnedKey)
+		}
+		userID := senderID.ToUserID()
+		if userID != nil {
+			t.Fatalf("ToUserID returned non-nil value %v", userID.String())
+		}
+	})
+}

spec/userid.go

@@ -18,10 +18,20 @@
 	domain string
 }
 
+// Creates a new UserID, returning an error if invalid
 func NewUserID(id string, allowHistoricalIDs bool) (*UserID, error) {
 	return parseAndValidateUserID(id, allowHistoricalIDs)
 }
 
+// Creates a new UserID, panicing if invalid
+func NewUserIDOrPanic(id string, allowHistoricalIDs bool) UserID {
+	userID, err := parseAndValidateUserID(id, allowHistoricalIDs)
+	if err != nil {
+		panic(fmt.Sprintf("NewUserIDOrPanic failed: invalid user ID %s", id))
+	}
+	return *userID
+}
+
 // Returns the full userID string including leading sigil
 func (user *UserID) String() string {
 	return user.raw