Injection is #1 on the 2010 OWASP Top Ten web security risks. Command injection occurs when shell commands unsafely include user-manipulatable values.

There are many ways to run commands in Ruby:

`ls #{params[:file]}`

system("ls #{params[:dir]}")

exec("md5sum #{params[:input]}")

Brakeman will warn on any method like these that uses user input or unsafely interpolates variables.

See the Ruby Security Guide for details.

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

This cop checks for the use of the read_attribute or write_attribute methods and recommends square brackets instead.

If an attribute is missing from the instance (for example, when initialized by a partial select) then read_attribute will return nil, but square brackets will raise an ActiveModel::MissingAttributeError.

Explicitly raising an error in this situation is preferable, and that is why rubocop recommends using square brackets.

Example:

# bad
x = read_attribute(:attr)
write_attribute(:attr, val)

# good
x = self[:attr]
self[:attr] = val

This cop checks for the use of the read_attribute or write_attribute methods and recommends square brackets instead.

If an attribute is missing from the instance (for example, when initialized by a partial select) then read_attribute will return nil, but square brackets will raise an ActiveModel::MissingAttributeError.

Explicitly raising an error in this situation is preferable, and that is why rubocop recommends using square brackets.

Example:

# bad
x = read_attribute(:attr)
write_attribute(:attr, val)

# good
x = self[:attr]
self[:attr] = val

This cop checks for the use of the read_attribute or write_attribute methods and recommends square brackets instead.

If an attribute is missing from the instance (for example, when initialized by a partial select) then read_attribute will return nil, but square brackets will raise an ActiveModel::MissingAttributeError.

Explicitly raising an error in this situation is preferable, and that is why rubocop recommends using square brackets.

Example:

# bad
x = read_attribute(:attr)
write_attribute(:attr, val)

# good
x = self[:attr]
self[:attr] = val

This cop checks for the use of methods which skip validations which are listed in https://guides.rubyonrails.org/active_record_validations.html#skipping-validations

Methods may be ignored from this rule by configuring a Whitelist.

Example:

# bad
Article.first.decrement!(:view_count)
DiscussionBoard.decrement_counter(:post_count, 5)
Article.first.increment!(:view_count)
DiscussionBoard.increment_counter(:post_count, 5)
person.toggle :active
product.touch
Billing.update_all("category = 'authorized', author = 'David'")
user.update_attribute(:website, 'example.com')
user.update_columns(last_request_at: Time.current)
Post.update_counters 5, comment_count: -1, action_count: 1

# good
user.update(website: 'example.com')
FileUtils.touch('file')

Example: Whitelist: ["touch"]

# bad
DiscussionBoard.decrement_counter(:post_count, 5)
DiscussionBoard.increment_counter(:post_count, 5)
person.toggle :active

# good
user.touch

This cop checks for indentation that doesn't use the specified number of spaces.

See also the IndentationConsistency cop which is the companion to this one.

Example:

# bad
class A
 def test
  puts 'hello'
 end
end

# good
class A
  def test
    puts 'hello'
  end
end

Example: IgnoredPatterns: ['^\s*module']

# bad
module A
class B
  def test
  puts 'hello'
  end
end
end

# good
module A
class B
  def test
    puts 'hello'
  end
end
end