imapserver: add ID capability

imapserver/capability.go

@@ -91,6 +91,7 @@ func (c *Conn) availableCaps() []imap.Cap {
 			imap.CapCreateSpecialUse,
 			imap.CapLiteralPlus,
 			imap.CapUnauthenticate,
+			imap.CapID,
 		})
 	}
 	return caps

imapserver/conn.go

@@ -220,6 +220,9 @@ func (c *Conn) readCommand(dec *imapwire.Decoder) error {
 		err = c.handleLogout(dec)
 	case "CAPABILITY":
 		err = c.handleCapability(dec)
+	case "ID":
+		err = c.handleID(tag, dec)
+		sendOK = false
 	case "STARTTLS":
 		err = c.handleStartTLS(tag, dec)
 		sendOK = false

imapserver/id.go

@@ -0,0 +1,155 @@
+package imapserver
+
+import (
+	"fmt"
+
+	"github.com/emersion/go-imap/v2"
+	"github.com/emersion/go-imap/v2/internal/imapwire"
+)
+
+func (c *Conn) handleID(tag string, dec *imapwire.Decoder) error {
+	idData, err := readID(dec)
+	if err != nil {
+		return fmt.Errorf("in id: %v", err)
+	}
+
+	if !dec.ExpectCRLF() {
+		return dec.Err()
+	}
+
+	var serverIDData *imap.IDData
+	if idSess, ok := c.session.(SessionID); ok {
+		serverIDData = idSess.ID(idData)
+	}
+
+	enc := newResponseEncoder(c)
+	enc.Atom("*").SP().Atom("ID")
+
+	if serverIDData == nil {
+		enc.SP().NIL()
+	} else {
+		enc.SP().Special('(')
+		isFirstKey := true
+		if serverIDData.Name != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "name", serverIDData.Name)
+		}
+		if serverIDData.Version != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "version", serverIDData.Version)
+		}
+		if serverIDData.OS != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "os", serverIDData.OS)
+		}
+		if serverIDData.OSVersion != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "os-version", serverIDData.OSVersion)
+		}
+		if serverIDData.Vendor != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "vendor", serverIDData.Vendor)
+		}
+		if serverIDData.SupportURL != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "support-url", serverIDData.SupportURL)
+		}
+		if serverIDData.Address != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "address", serverIDData.Address)
+		}
+		if serverIDData.Date != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "date", serverIDData.Date)
+		}
+		if serverIDData.Command != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "command", serverIDData.Command)
+		}
+		if serverIDData.Arguments != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "arguments", serverIDData.Arguments)
+		}
+		if serverIDData.Environment != "" {
+			addIDKeyValue(enc.Encoder, &isFirstKey, "environment", serverIDData.Environment)
+		}
+		enc.Special(')')
+	}
+
+	err = enc.CRLF()
+	enc.end()
+	if err != nil {
+		return err
+	}
+
+	return c.writeStatusResp(tag, &imap.StatusResponse{
+		Type: imap.StatusResponseTypeOK,
+		Text: "ID completed",
+	})
+}
+
+func readID(dec *imapwire.Decoder) (*imap.IDData, error) {
+	if !dec.ExpectSP() {
+		return nil, dec.Err()
+	}
+
+	if dec.ExpectNIL() {
+		return nil, nil
+	}
+
+	data := &imap.IDData{}
+	currKey := ""
+	err := dec.ExpectList(func() error {
+		var keyOrValue string
+		if !dec.String(&keyOrValue) {
+			return fmt.Errorf("in id key-val list: %v", dec.Err())
+		}
+
+		if currKey == "" {
+			currKey = keyOrValue
+			return nil
+		}
+
+		switch currKey {
+		case "name":
+			data.Name = keyOrValue
+		case "version":
+			data.Version = keyOrValue
+		case "os":
+			data.OS = keyOrValue
+		case "os-version":
+			data.OSVersion = keyOrValue
+		case "vendor":
+			data.Vendor = keyOrValue
+		case "support-url":
+			data.SupportURL = keyOrValue
+		case "address":
+			data.Address = keyOrValue
+		case "date":
+			data.Date = keyOrValue
+		case "command":
+			data.Command = keyOrValue
+		case "arguments":
+			data.Arguments = keyOrValue
+		case "environment":
+			data.Environment = keyOrValue
+		default:
+			// Ignore unknown key
+		}
+		currKey = ""
+
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return data, nil
+}
+
+func addIDKeyValue(enc *imapwire.Encoder, isFirstKey *bool, key, value string) {
+	if *isFirstKey {
+		enc.Quoted(key).SP().Quoted(value)
+	} else {
+		enc.SP().Quoted(key).SP().Quoted(value)
+	}
+	*isFirstKey = false
+}
+
+// SessionID is an interface for sessions that can provide server ID information.
+type SessionID interface {
+	// ID returns server information in response to a client ID command.
+	// The client's ID information is provided if available.
+	ID(clientID *imap.IDData) *imap.IDData
+}