fix(common): harden CORS, sort, raw-SQL WHERE and x-custom-sql-or

Add a `hardening` config section (RESOLVESPEC_HARDENING_*) so each
fix can be switched off to restore the previous behaviour:

- cors_strict_origins: only reflect origins listed in
  cors.allowed_origins / server URLs, with credentials; `*` never
  sends credentials; fix shared-slice append of expose headers.
- sort_strict: join aliases must match `alias.identifier` (empty alias
  no longer matches everything); sort expressions reject dangerous
  functions/catalogs; cql* columns must be identifier-safe.
- sql_strict: client raw-SQL fragments must have balanced parens and
  quotes, no comments/`;`/`$$`, DML keywords, dangerous functions or
  system catalogs; a rejected fragment now fails closed ("(1=0)")
  instead of dropping the filter. Subqueries stay allowed unless
  sql_block_subqueries is set.
- x-custom-sql-or is grouped together with the client's own
  conditions (new optional WhereGrouper, implemented for bun and gorm)
  so it can no longer OR past server-side filters.

pkg/common/adapters/database/bun.go

@@ -537,6 +537,19 @@ func (b *BunSelectQuery) WhereOr(query string, args ...interface{}) common.Selec
 	return b
 }
 
+// WhereGroup wraps the conditions added by fn in one parenthesised group ANDed with the rest.
+func (b *BunSelectQuery) WhereGroup(fn func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
+	b.query = b.query.WhereGroup(" AND ", func(q *bun.SelectQuery) *bun.SelectQuery {
+		inner := *b
+		inner.query = q
+		if res, ok := fn(&inner).(*BunSelectQuery); ok {
+			return res.query
+		}
+		return q
+	})
+	return b
+}
+
 func (b *BunSelectQuery) Join(query string, args ...interface{}) common.SelectQuery {
 	// Extract optional prefix from args
 	// If the last arg is a string that looks like a table prefix, use it

pkg/common/adapters/database/gorm.go

@@ -377,6 +377,16 @@ func (g *GormSelectQuery) WhereOr(query string, args ...interface{}) common.Sele
 	return g
 }
 
+// WhereGroup wraps the conditions added by fn in one parenthesised group ANDed with the rest.
+func (g *GormSelectQuery) WhereGroup(fn func(common.SelectQuery) common.SelectQuery) common.SelectQuery {
+	inner := *g
+	inner.db = g.db.Session(&gorm.Session{NewDB: true})
+	if res, ok := fn(&inner).(*GormSelectQuery); ok {
+		g.db = g.db.Where(res.db)
+	}
+	return g
+}
+
 func (g *GormSelectQuery) Join(query string, args ...interface{}) common.SelectQuery {
 	// Extract optional prefix from args
 	// If the last arg is a string that looks like a table prefix, use it

pkg/common/adapters/database/where_group_test.go

@@ -0,0 +1,31 @@
+package database
+
+import (
+	"database/sql"
+	"strings"
+	"testing"
+
+	"github.com/uptrace/bun"
+	"github.com/uptrace/bun/dialect/pgdialect"
+
+	"github.com/bitechdev/ResolveSpec/pkg/common"
+)
+
+// The client's OR must widen only the client's own conditions, never the
+// server-side condition ANDed after it.
+func TestBunWhereGroupConfinesOr(t *testing.T) {
+	db := bun.NewDB(&sql.DB{}, pgdialect.New())
+	q := &BunSelectQuery{query: db.NewSelect().TableExpr("items"), db: db, driverName: "postgres"}
+
+	var sq common.SelectQuery = q.Where("a = 1")
+	sq = sq.(common.WhereGrouper).WhereGroup(func(g common.SelectQuery) common.SelectQuery {
+		return g.Where("b = 2").WhereOr("(c = 3)")
+	})
+	sq = sq.Where("tenant = 5")
+
+	got := sq.(*BunSelectQuery).query.String()
+	want := `WHERE (a = 1) AND ((b = 2) OR ((c = 3))) AND (tenant = 5)`
+	if !strings.Contains(got, want) {
+		t.Fatalf("unexpected SQL:\n got: %s\nwant to contain: %s", got, want)
+	}
+}

pkg/common/cors.go

@@ -20,7 +20,15 @@ func DefaultCORSConfig() CORSConfig {
 	configManager := config.GetConfigManager()
 	cfg, _ := configManager.GetConfig()
 	hosts := make([]string, 0)
-	// hosts = append(hosts, "*")
+	if cfg == nil {
+		return CORSConfig{
+			AllowedMethods: []string{"GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"},
+			AllowedHeaders: GetHeadSpecHeaders(),
+			MaxAge:         86400,
+		}
+	}
+	// Explicitly configured origins (cors.allowed_origins); "*" allows any origin without credentials
+	hosts = append(hosts, cfg.CORS.AllowedOrigins...)
 
 	_, _, ipsList := config.GetIPs()
 
@@ -113,25 +121,63 @@ func GetHeadSpecHeaders() []string {
 	}
 }
 
-// SetCORSHeaders sets CORS headers on a response writer
+// originAllowed reports whether origin matches config.AllowedOrigins exactly
+// (case-insensitive, trailing slash ignored). wildcard is true when the list
+// contains "*".
+func originAllowed(origin string, allowed []string) (ok bool, wildcard bool) {
+	norm := strings.ToLower(strings.TrimRight(strings.TrimSpace(origin), "/"))
+	for _, a := range allowed {
+		a = strings.ToLower(strings.TrimRight(strings.TrimSpace(a), "/"))
+		if a == "*" {
+			wildcard = true
+			continue
+		}
+		if a != "" && a == norm {
+			return true, wildcard
+		}
+	}
+	return false, wildcard
+}
+
+// SetCORSHeaders sets CORS headers on a response writer.
+//
+// The request Origin is only reflected (and credentials only allowed) when it
+// is listed in config.AllowedOrigins. A "*" entry allows any origin but never
+// with credentials. Unlisted origins get no CORS headers, so browsers block
+// the cross-origin read.
 func SetCORSHeaders(w ResponseWriter, r Request, config CORSConfig) {
-	// Reflect the request origin; fall back to wildcard only when no origin is present
+	if !Hardening().CORSStrictOrigins {
+		setCORSHeadersLegacy(w, r, config)
+		return
+	}
 	origin := r.Header("Origin")
 	if origin == "" {
-		origin = "*"
+		// Not a cross-origin browser request; nothing to protect.
+		w.SetHeader("Access-Control-Allow-Origin", "*")
 	} else {
 		// Vary must be set so caches don't serve one origin's response to another
-		httpW := w.UnderlyingResponseWriter()
-		httpW.Header().Set("Vary", "Origin")
+		w.UnderlyingResponseWriter().Header().Set("Vary", "Origin")
+
+		ok, wildcard := originAllowed(origin, config.AllowedOrigins)
+		switch {
+		case ok:
+			w.SetHeader("Access-Control-Allow-Origin", origin)
+			w.SetHeader("Access-Control-Allow-Credentials", "true")
+		case wildcard:
+			w.SetHeader("Access-Control-Allow-Origin", "*")
+		default:
+			return
+		}
 	}
-	w.SetHeader("Access-Control-Allow-Origin", origin)
 
 	// Set allowed methods
 	if len(config.AllowedMethods) > 0 {
 		w.SetHeader("Access-Control-Allow-Methods", strings.Join(config.AllowedMethods, ", "))
 	}
 
-	// Reflect the preflight request headers when present; otherwise use the explicit config list
+	// The origin is trusted at this point, so reflecting the preflight request
+	// headers is safe (the config list contains "X-Foo-*" patterns that browsers
+	// cannot match literally).
 	requestedHeaders := r.Header("Access-Control-Request-Headers")
 	if requestedHeaders != "" {
 		w.SetHeader("Access-Control-Allow-Headers", requestedHeaders)
@@ -144,13 +190,40 @@ func SetCORSHeaders(w ResponseWriter, r Request, config CORSConfig) {
 		w.SetHeader("Access-Control-Max-Age", fmt.Sprintf("%d", config.MaxAge))
 	}
 
-	// Allow credentials only when a specific origin is reflected (not wildcard)
+	// Expose headers that clients can read (fresh slice: avoid appending into
+	// config.AllowedHeaders' backing array)
+	exposeHeaders := make([]string, 0, len(config.AllowedHeaders)+3)
+	exposeHeaders = append(exposeHeaders, config.AllowedHeaders...)
+	exposeHeaders = append(exposeHeaders, "Content-Range", "X-Api-Range-Total", "X-Api-Range-Size")
+	w.SetHeader("Access-Control-Expose-Headers", strings.Join(exposeHeaders, ", "))
+}
+
+// setCORSHeadersLegacy is the pre-hardening behaviour (reflect any origin with
+// credentials). Used only when hardening.cors_strict_origins is false.
+func setCORSHeadersLegacy(w ResponseWriter, r Request, config CORSConfig) {
+	origin := r.Header("Origin")
+	if origin == "" {
+		origin = "*"
+	} else {
+		w.UnderlyingResponseWriter().Header().Set("Vary", "Origin")
+	}
+	w.SetHeader("Access-Control-Allow-Origin", origin)
+	if len(config.AllowedMethods) > 0 {
+		w.SetHeader("Access-Control-Allow-Methods", strings.Join(config.AllowedMethods, ", "))
+	}
+	if requested := r.Header("Access-Control-Request-Headers"); requested != "" {
+		w.SetHeader("Access-Control-Allow-Headers", requested)
+	} else if len(config.AllowedHeaders) > 0 {
+		w.SetHeader("Access-Control-Allow-Headers", strings.Join(config.AllowedHeaders, ", "))
+	}
+	if config.MaxAge > 0 {
+		w.SetHeader("Access-Control-Max-Age", fmt.Sprintf("%d", config.MaxAge))
+	}
 	if origin != "*" {
 		w.SetHeader("Access-Control-Allow-Credentials", "true")
 	}
-
-	// Expose headers that clients can read
-	exposeHeaders := config.AllowedHeaders
+	exposeHeaders := make([]string, 0, len(config.AllowedHeaders)+3)
+	exposeHeaders = append(exposeHeaders, config.AllowedHeaders...)
 	exposeHeaders = append(exposeHeaders, "Content-Range", "X-Api-Range-Total", "X-Api-Range-Size")
 	w.SetHeader("Access-Control-Expose-Headers", strings.Join(exposeHeaders, ", "))
 }

pkg/common/hardening.go

@@ -0,0 +1,16 @@
+package common
+
+import "github.com/bitechdev/ResolveSpec/pkg/config"
+
+// hardeningProvider returns the active hardening switches. Tests may replace it.
+var hardeningProvider = func() config.HardeningConfig {
+	cfg, err := config.GetConfigManager().GetConfig()
+	if err != nil || cfg == nil {
+		// Fail secure: hardening on when config is unavailable.
+		return config.HardeningConfig{CORSStrictOrigins: true, SortStrict: true, SQLStrict: true}
+	}
+	return cfg.Hardening
+}
+
+// Hardening returns the security hardening toggles (config section "hardening").
+func Hardening() config.HardeningConfig { return hardeningProvider() }

pkg/common/hardening_test.go

@@ -0,0 +1,121 @@
+package common
+
+import (
+	"testing"
+
+	"github.com/bitechdev/ResolveSpec/pkg/config"
+)
+
+func setHardening(t *testing.T, h config.HardeningConfig) {
+	t.Helper()
+	old := hardeningProvider
+	hardeningProvider = func() config.HardeningConfig { return h }
+	t.Cleanup(func() { hardeningProvider = old })
+}
+
+var (
+	hardOn  = config.HardeningConfig{CORSStrictOrigins: true, SortStrict: true, SQLStrict: true}
+	hardOff = config.HardeningConfig{}
+)
+
+func TestSanitizeWhereClause_Strict(t *testing.T) {
+	setHardening(t, hardOn)
+	allowed := []string{
+		"status = 'awaiting update approval'",
+		"last_update > '2020-01-01'",
+		"name = 'it''s; fine'",
+		"(a = 1 or b = 2) and ifblnk(c) = 'x'",
+	}
+	for _, w := range allowed {
+		if got := SanitizeWhereClause(w, ""); got == "" || got == "(1=0)" {
+			t.Errorf("legitimate clause %q rejected: %q", w, got)
+		}
+	}
+	hostile := []string{
+		"1=1)) OR ((1=1",
+		"id = 1 or (select count(*) from pg_shadow) > 0",
+		"id in (select oid from pg_catalog.pg_class)",
+		"id = 1 and pg_sleep(5) is not null",
+		"id = 1; delete/**/from items",
+		"id = 1 -- x",
+		"name = 'unterminated",
+	}
+	for _, w := range hostile {
+		if got := SanitizeWhereClause(w, "t"); got != "(1=0)" {
+			t.Errorf("hostile clause %q not rejected closed: %q", w, got)
+		}
+	}
+}
+
+func TestSanitizeWhereClause_Subqueries(t *testing.T) {
+	q := "id in (select l.id from other l where l.x = 1)"
+	setHardening(t, hardOn)
+	if got := SanitizeWhereClause(q, "t"); got == "(1=0)" || got == "" {
+		t.Errorf("subquery should be allowed by default: %q", got)
+	}
+	h := hardOn
+	h.SQLBlockSubqueries = true
+	setHardening(t, h)
+	if got := SanitizeWhereClause(q, "t"); got != "(1=0)" {
+		t.Errorf("subquery should be blocked with sql_block_subqueries: %q", got)
+	}
+}
+
+func TestSanitizeWhereClause_StrictOff_LegacyBehaviour(t *testing.T) {
+	setHardening(t, hardOff)
+	if got := SanitizeWhereClause("a = 1 and drop table x", "t"); got != "" {
+		t.Errorf("legacy fail-open expected empty, got %q", got)
+	}
+}
+
+func TestSortStrict(t *testing.T) {
+	v := NewColumnValidator(TestModel{})
+	opts := RequestOptions{
+		JoinAliases: []string{""},
+		Sort:        []SortOption{{Column: "x.id, (select pg_sleep(10))"}, {Column: "(select pg_sleep(1))"}},
+	}
+	setHardening(t, hardOn)
+	if got := v.FilterRequestOptions(opts).Sort; len(got) != 0 {
+		t.Errorf("strict: expected no sorts, got %v", got)
+	}
+	opts.JoinAliases = []string{"j"}
+	opts.Sort = []SortOption{{Column: "j.id"}, {Column: "j.id, (select 1)"}, {Column: "(select max(age) from users)"}}
+	if got := v.FilterRequestOptions(opts).Sort; len(got) != 2 {
+		t.Errorf("strict: join column and plain subquery sort must be allowed, got %v", got)
+	}
+	opts.Sort = []SortOption{{Column: "j.id"}, {Column: "j.id, (select 1)"}}
+	if got := v.FilterRequestOptions(opts).Sort; len(got) != 1 || got[0].Column != "j.id" {
+		t.Errorf("strict: expected only j.id, got %v", got)
+	}
+	setHardening(t, hardOff)
+	opts.JoinAliases = []string{""}
+	opts.Sort = []SortOption{{Column: "x.id, (select pg_sleep(10))"}}
+	if got := v.FilterRequestOptions(opts).Sort; len(got) != 1 {
+		t.Errorf("legacy: expected sort kept, got %v", got)
+	}
+}
+
+func TestCQLColumn(t *testing.T) {
+	v := NewColumnValidator(TestModel{})
+	setHardening(t, hardOn)
+	if !v.IsValidColumn("cqlComputed1") || v.IsValidColumn("cql1); drop") {
+		t.Error("strict cql validation wrong")
+	}
+	setHardening(t, hardOff)
+	if !v.IsValidColumn("cql1); drop") {
+		t.Error("legacy cql behaviour should be permissive")
+	}
+}
+
+func TestOriginAllowed(t *testing.T) {
+	list := []string{"https://app.example.com/", "http://localhost:8080"}
+	if ok, _ := originAllowed("https://APP.example.com", list); !ok {
+		t.Error("listed origin should match case-insensitively, ignoring trailing slash")
+	}
+	if ok, _ := originAllowed("https://evil.example", list); ok {
+		t.Error("unlisted origin must not match")
+	}
+	if ok, wc := originAllowed("https://evil.example", []string{"*"}); ok || !wc {
+		t.Error("wildcard must be reported separately and never as an exact match")
+	}
+}

pkg/common/interfaces.go

@@ -319,3 +319,11 @@ type QueryHandler interface {
 	SpecHandler
 	// Methods are defined in funcspec package due to different function signature requirements
 }
+
+// WhereGrouper is implemented by query builders that can wrap a set of
+// conditions (including WhereOr) in one parenthesised group that is ANDed with
+// the rest of the query. It is optional so existing SelectQuery implementations
+// keep compiling.
+type WhereGrouper interface {
+	WhereGroup(fn func(SelectQuery) SelectQuery) SelectQuery
+}

pkg/common/sql_helpers.go

@@ -148,6 +148,93 @@ func validateWhereClauseSecurity(where string) error {
 	return nil
 }
 
+var (
+	reStrictDML = regexp.MustCompile(`(?i)\b(delete|update|truncate|drop|alter|create|insert|grant|revoke|exec|execute|copy|call|do|merge|vacuum|listen|notify|set|returning|into)\b`)
+	// reStrictSubquery is only enforced when hardening.sql_block_subqueries is on.
+	reStrictSubquery = regexp.MustCompile(`(?i)\b(select|union|lateral|with)\b`)
+	// reStrictDangerousFunc matches functions/schemas that enable DoS or data
+	// exfiltration through a WHERE fragment (sleep, file/large-object access,
+	// dblink, config access, catalogs).
+	reStrictDangerousFunc = regexp.MustCompile(`(?i)\b(pg_[a-z0-9_]*|lo_[a-z0-9_]*|dblink[a-z0-9_]*|set_config|current_setting|query_to_xml[a-z_]*|xpath[a-z_]*|generate_series|repeat|crypt|information_schema|sleep|benchmark)\b`)
+)
+
+// stripSQLLiterals blanks out single-quoted literals (honouring ”) and
+// double-quoted identifiers so structural checks only see SQL syntax.
+// ok is false when a quote is left unterminated.
+func stripSQLLiterals(s string) (out string, ok bool) {
+	var b strings.Builder
+	for i := 0; i < len(s); i++ {
+		ch := s[i]
+		if ch != '\'' && ch != '"' {
+			b.WriteByte(ch)
+			continue
+		}
+		q := ch
+		closed := false
+		for i++; i < len(s); i++ {
+			if s[i] == q {
+				if i+1 < len(s) && s[i+1] == q { // escaped quote
+					i++
+					continue
+				}
+				closed = true
+				break
+			}
+		}
+		if !closed {
+			return "", false
+		}
+		b.WriteString("''")
+	}
+	return b.String(), true
+}
+
+// validateWhereClauseStrict is the hardened check for client raw-SQL fragments
+// (hardening.sql_strict). It inspects syntax outside string literals: quotes
+// and parentheses must be balanced, and comments, statement separators,
+// dollar-quoting, DML keywords, dangerous functions and system catalogs are
+// rejected. Subqueries and ordinary functions stay allowed unless
+// hardening.sql_block_subqueries is set. isJoin (custom joins) still gets all
+// checks except the subquery block, since joins legitimately use subqueries.
+func validateWhereClauseStrict(where string, isJoin bool) error {
+	stripped, ok := stripSQLLiterals(where)
+	if !ok {
+		return fmt.Errorf("unterminated quote")
+	}
+	for _, bad := range []string{"--", "/*", "*/", ";", "$$", "\\"} {
+		if strings.Contains(stripped, bad) {
+			return fmt.Errorf("forbidden token %q", bad)
+		}
+	}
+	depth := 0
+	for i := 0; i < len(stripped); i++ {
+		switch stripped[i] {
+		case '(':
+			depth++
+		case ')':
+			depth--
+			if depth < 0 {
+				return fmt.Errorf("unbalanced parentheses")
+			}
+		}
+	}
+	if depth != 0 {
+		return fmt.Errorf("unbalanced parentheses")
+	}
+	if m := reStrictDML.FindString(stripped); m != "" {
+		return fmt.Errorf("forbidden keyword %q", strings.ToLower(m))
+	}
+	if m := reStrictDangerousFunc.FindString(stripped); m != "" {
+		return fmt.Errorf("forbidden function or schema %q", strings.ToLower(m))
+	}
+	if !isJoin && Hardening().SQLBlockSubqueries {
+		if m := reStrictSubquery.FindString(stripped); m != "" {
+			return fmt.Errorf("subqueries not allowed (%q)", strings.ToLower(m))
+		}
+	}
+	return nil
+}
+
 // SanitizeWhereClause removes trivial conditions and fixes incorrect table prefixes
 // This function should be used everywhere a WHERE statement is sent to ensure clean, efficient SQL
 //
@@ -174,7 +261,14 @@ func SanitizeWhereClause(where string, tableName string, options ...*RequestOpti
 	where = strings.TrimSpace(where)
 
 	// Validate that the WHERE clause doesn't contain dangerous SQL statements
-	if err := validateWhereClauseSecurity(where); err != nil {
+	if Hardening().SQLStrict {
+		// Strict mode: fail closed. A rejected client fragment must not turn into
+		// "no filter", so substitute a clause that matches no rows.
+		if err := validateWhereClauseStrict(where, tableName == ""); err != nil {
+			logger.Warn("Rejected client SQL fragment (%v): %s", err, where)
+			return "(1=0)"
+		}
+	} else if err := validateWhereClauseSecurity(where); err != nil {
 		logger.Debug("Security validation failed for WHERE clause: %v", err)
 		return ""
 	}

pkg/common/sql_helpers_test.go

@@ -102,25 +102,25 @@ func TestSanitizeWhereClause(t *testing.T) {
 			name:      "dangerous DELETE keyword - blocked",
 			where:     "status = 'active'; DELETE FROM users",
 			tableName: "users",
-			expected:  "",
+			expected:  "(1=0)", // fail closed,
 		},
 		{
 			name:      "dangerous UPDATE keyword - blocked",
 			where:     "1=1; UPDATE users SET admin = true",
 			tableName: "users",
-			expected:  "",
+			expected:  "(1=0)", // fail closed,
 		},
 		{
 			name:      "dangerous TRUNCATE keyword - blocked",
 			where:     "status = 'active' OR TRUNCATE TABLE users",
 			tableName: "users",
-			expected:  "",
+			expected:  "(1=0)", // fail closed,
 		},
 		{
 			name:      "dangerous DROP keyword - blocked",
 			where:     "status = 'active'; DROP TABLE users",
 			tableName: "users",
-			expected:  "",
+			expected:  "(1=0)", // fail closed,
 		},
 		{
 			name:      "subquery with table alias should not be modified",

pkg/common/validation.go

@@ -3,6 +3,7 @@ package common
 import (
 	"fmt"
 	"reflect"
+	"regexp"
 	"sort"
 	"strings"
 
@@ -105,7 +106,7 @@ func (v *ColumnValidator) ValidateColumn(column string) error {
 	}
 
 	// Allow columns prefixed with "cql" (case insensitive) for computed columns
-	if strings.HasPrefix(strings.ToLower(column), "cql") {
+	if lc := strings.ToLower(column); strings.HasPrefix(lc, "cql") && (!Hardening().SortStrict || reCQLColumn.MatchString(lc)) {
 		return nil
 	}
 
@@ -275,8 +276,14 @@ func (v *ColumnValidator) FilterRequestOptions(options RequestOptions) RequestOp
 			validSorts = append(validSorts, sort)
 		} else {
 			foundJoin := false
+			strictSort := Hardening().SortStrict
 			for _, j := range options.JoinAliases {
-				if strings.Contains(sort.Column, j) {
+				if strictSort {
+					if isJoinAliasColumn(sort.Column, j) {
+						foundJoin = true
+						break
+					}
+				} else if strings.Contains(sort.Column, j) {
 					foundJoin = true
 					break
 				}
@@ -287,7 +294,7 @@ func (v *ColumnValidator) FilterRequestOptions(options RequestOptions) RequestOp
 			}
 			if strings.HasPrefix(sort.Column, "(") && strings.HasSuffix(sort.Column, ")") {
 				// Allow sort by expression/subquery, but validate for security
-				if IsSafeSortExpression(sort.Column) {
+				if IsSafeSortExpression(sort.Column) && (!strictSort || isSortExpressionRestricted(sort.Column)) {
 					validSorts = append(validSorts, sort)
 				} else {
 					logger.Warn("Unsafe sort expression '%s' removed", sort.Column)
@@ -376,6 +383,56 @@ func (v *ColumnValidator) FilterRequestOptions(options RequestOptions) RequestOp
 	return filtered
 }
 
+var reCQLColumn = regexp.MustCompile(`^cql[a-z0-9_]*$`)
+
+var (
+	reJoinColumnIdent = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*$`)
+)
+
+// isJoinAliasColumn reports whether col is exactly "<alias>.<identifier>".
+// An empty alias never matches.
+func isJoinAliasColumn(col, alias string) bool {
+	if alias == "" || !strings.HasPrefix(col, alias+".") {
+		return false
+	}
+	return reJoinColumnIdent.MatchString(col[len(alias)+1:])
+}
+
+// isSortExpressionRestricted applies the hardened checks to a client sort
+// expression. Subqueries and ordinary functions are allowed; dangerous
+// functions/catalogs (pg_sleep, pg_*, dblink, ...) and unbalanced parentheses are
+// rejected. Subqueries are blocked only when hardening.sql_block_subqueries is on.
+func isSortExpressionRestricted(expr string) bool {
+	stripped, ok := stripSQLLiterals(expr)
+	if !ok {
+		return false
+	}
+	depth := 0
+	for i := 0; i < len(stripped); i++ {
+		switch stripped[i] {
+		case '(':
+			depth++
+		case ')':
+			depth--
+			if depth < 0 {
+				return false
+			}
+		}
+	}
+	if depth != 0 {
+		return false
+	}
+	if m := reStrictDangerousFunc.FindString(stripped); m != "" {
+		logger.Warn("Forbidden function '%s' in sort expression: %s", m, expr)
+		return false
+	}
+	if Hardening().SQLBlockSubqueries && reStrictSubquery.MatchString(stripped) {
+		logger.Warn("Subquery in sort expression rejected: %s", expr)
+		return false
+	}
+	return true
+}
+
 // IsSafeSortExpression validates that a sort expression (enclosed in brackets) is safe
 // and doesn't contain SQL injection attempts or dangerous commands
 func IsSafeSortExpression(expr string) bool {

pkg/common/validation_test.go

@@ -435,19 +435,19 @@ func TestFilterRequestOptions_WithSortExpressions(t *testing.T) {
 
 	options := RequestOptions{
 		Sort: []SortOption{
-			{Column: "id", Direction: "ASC"},                                    // Valid column
-			{Column: "(SELECT MAX(age) FROM users)", Direction: "DESC"},         // Safe expression
-			{Column: "name", Direction: "ASC"},                                  // Valid column
-			{Column: "(id); DROP TABLE users; --", Direction: "DESC"},          // Dangerous expression
-			{Column: "invalid_col", Direction: "ASC"},                           // Invalid column
+			{Column: "id", Direction: "ASC"},                                     // Valid column
+			{Column: "(SELECT MAX(age) FROM users)", Direction: "DESC"},          // Safe expression
+			{Column: "name", Direction: "ASC"},                                   // Valid column
+			{Column: "(id); DROP TABLE users; --", Direction: "DESC"},            // Dangerous expression
+			{Column: "invalid_col", Direction: "ASC"},                            // Invalid column
 			{Column: "(CASE WHEN age > 18 THEN 1 ELSE 0 END)", Direction: "ASC"}, // Safe expression
 		},
 	}
 
 	filtered := validator.FilterRequestOptions(options)
 
-	// Should keep: id, safe expression, name, another safe expression
-	// Should remove: dangerous expression, invalid column
+	// Keeps: id, subquery expression, name, CASE expression
+	// Removes: dangerous expression, invalid column
 	expectedCount := 4
 	if len(filtered.Sort) != expectedCount {
 		t.Errorf("Expected %d sort options, got %d", expectedCount, len(filtered.Sort))
@@ -474,8 +474,8 @@ type RelatedModel struct {
 // PreloadParentModel has a has-one relation to RelatedModel. The json tag on
 // the relation field is the name used in x-preload headers.
 type PreloadParentModel struct {
-	ID      int64        `bun:"id,pk"`
-	Name    string       `bun:"name"`
+	ID      int64         `bun:"id,pk"`
+	Name    string        `bun:"name"`
 	RELATED *RelatedModel `json:"RELATED" bun:"rel:has-one,join:id=related_id"`
 }