client: Have SetCapability() return an error for unsupported caps

Author: dveeden

client/auth.go

@@ -14,6 +14,18 @@ import (
 
 const defaultAuthPluginName = mysql.AUTH_NATIVE_PASSWORD
 
+var optionalCapabilities = []uint32{
+	mysql.CLIENT_FOUND_ROWS,
+	mysql.CLIENT_IGNORE_SPACE,
+	mysql.CLIENT_MULTI_STATEMENTS,
+	mysql.CLIENT_MULTI_RESULTS,
+	mysql.CLIENT_PS_MULTI_RESULTS,
+	mysql.CLIENT_CONNECT_ATTRS,
+	mysql.CLIENT_COMPRESS,
+	mysql.CLIENT_ZSTD_COMPRESSION_ALGORITHM,
+	mysql.CLIENT_LOCAL_FILES,
+}
+
 // defines the supported auth plugins
 var supportedAuthPlugins = []string{mysql.AUTH_NATIVE_PASSWORD, mysql.AUTH_SHA256_PASSWORD, mysql.AUTH_CACHING_SHA2_PASSWORD, mysql.AUTH_MARIADB_ED25519}
 
@@ -214,11 +226,9 @@ func (c *Conn) writeAuthHandshake() error {
 	// Adjust client capability flags on specific client requests
 	// Only flags that would make any sense setting and aren't handled elsewhere
 	// in the library are supported here
-	capability |= c.ccaps&mysql.CLIENT_FOUND_ROWS | c.ccaps&mysql.CLIENT_IGNORE_SPACE |
-		c.ccaps&mysql.CLIENT_MULTI_STATEMENTS | c.ccaps&mysql.CLIENT_MULTI_RESULTS |
-		c.ccaps&mysql.CLIENT_PS_MULTI_RESULTS | c.ccaps&mysql.CLIENT_CONNECT_ATTRS |
-		c.ccaps&mysql.CLIENT_COMPRESS | c.ccaps&mysql.CLIENT_ZSTD_COMPRESSION_ALGORITHM |
-		c.ccaps&mysql.CLIENT_LOCAL_FILES
+	for _, optionalCap := range optionalCapabilities {
+		capability |= c.ccaps & optionalCap
+	}
 
 	capability &^= c.clientExplicitOffCaps
 

client/conn.go

@@ -9,6 +9,7 @@ import (
 	"net"
 	"runtime"
 	"runtime/debug"
+	"slices"
 	"strings"
 	"time"
 
@@ -238,9 +239,13 @@ func (c *Conn) Ping() error {
 }
 
 // SetCapability marks the specified flag as explicitly enabled by the client.
-func (c *Conn) SetCapability(cap uint32) {
+func (c *Conn) SetCapability(cap uint32) error {
+	if !slices.Contains(optionalCapabilities, cap) {
+		return errors.New("unsupported or unknown capability")
+	}
 	c.ccaps |= cap
 	c.clientExplicitOffCaps &^= cap
+	return nil
 }
 
 // UnsetCapability marks the specified flag as explicitly disabled by the client.