Class: Scryer::Rules::ActiveStorageInlineDispositionRule

Inherits:
Scryer::Rule
  • Object
show all
Defined in:
lib/scryer/rules/active_storage_inline_disposition_rule.rb

Overview

Flags an explicit disposition: "inline"/:inline on a blob/variant URL helper (rails_blob_path, rails_blob_url, url_for, a .variant(...) chain). Serving user-uploaded content inline (rendered directly in the browser, rather than downloaded) can lead to stored XSS if the uploaded file's content-type isn't tightly restricted — an uploaded SVG or HTML file executes in the page's own origin.

Instance Attribute Summary

Attributes inherited from Scryer::Rule

#file, #sexp, #source

Instance Method Summary collapse

Methods inherited from Scryer::Rule

inherited, #initialize

Constructor Details

This class inherits a constructor from Scryer::Rule

Instance Method Details

#scan ⇒ Object 



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# File 'lib/scryer/rules/active_storage_inline_disposition_rule.rb', line 15

def scan
  findings = []

  Ast.each_node(sexp) do |node|
    next unless Ast.tagged?(node, :method_add_arg, :command, :command_call)

    inner = Ast.tagged?(node, :method_add_arg) ? node[1] : node
    name_pair = Ast.call_name(inner)
    next unless name_pair

    args = Ast.call_arguments(node)
    disposition = Ast.keyword_arg(args, "disposition")
    next unless disposition && Ast.literal_text(disposition) == "inline"

    line = Ast.line_of(node)
    findings << finding(
      line: line,
      message: "`disposition: \"inline\"` renders this attachment's content directly in " \
                "the browser instead of downloading it — if the attachment's content-type " \
                "isn't tightly restricted, a user-uploaded SVG or HTML file served this way " \
                "executes as if it were part of the site.",
      suggested_fix: "Prefer the default `disposition: \"attachment\"` (or drop the option " \
                      "entirely) unless inline rendering is genuinely required — and if it " \
                      "is, make sure the attachment has a strict `content_type:` allowlist " \
                      "(e.g. image types only) so nothing executable can reach this code path."
    )
  end

  findings
end