Injection is #1 on the 2013 OWASP Top Ten web security risks. SQL injection is when a user is able to manipulate a value which is used unsafely inside a SQL query. This can lead to data leaks, data loss, elevation of privilege, and other unpleasant outcomes.

Brakeman focuses on ActiveRecord methods dealing with building SQL statements.

A basic (Rails 2.x) example looks like this:

User.first(:conditions => "username = '#{params[:username]}'")

Brakeman would produce a warning like this:

Possible SQL injection near line 30: User.first(:conditions => ("username = '#{params[:username]}'"))

The safe way to do this query is to use a parameterized query:

User.first(:conditions => ["username = ?", params[:username]])

Brakeman also understands the new Rails 3.x way of doing things (and local variables and concatenation):

username = params[:user][:name].downcase
password = params[:user][:password]

User.first.where("username = '" + username + "' AND password = '" + password + "'")

This results in this kind of warning:

Possible SQL injection near line 37:
User.first.where((((("username = '" + params[:user][:name].downcase) + "' AND password = '") + params[:user][:password]) + "'"))

See the Ruby Security Guide for more information and Rails-SQLi.org for many examples of SQL injection in Rails.

Injection is #1 on the 2013 OWASP Top Ten web security risks. SQL injection is when a user is able to manipulate a value which is used unsafely inside a SQL query. This can lead to data leaks, data loss, elevation of privilege, and other unpleasant outcomes.

Brakeman focuses on ActiveRecord methods dealing with building SQL statements.

A basic (Rails 2.x) example looks like this:

User.first(:conditions => "username = '#{params[:username]}'")

Brakeman would produce a warning like this:

Possible SQL injection near line 30: User.first(:conditions => ("username = '#{params[:username]}'"))

The safe way to do this query is to use a parameterized query:

User.first(:conditions => ["username = ?", params[:username]])

Brakeman also understands the new Rails 3.x way of doing things (and local variables and concatenation):

username = params[:user][:name].downcase
password = params[:user][:password]

User.first.where("username = '" + username + "' AND password = '" + password + "'")

This results in this kind of warning:

Possible SQL injection near line 37:
User.first.where((((("username = '" + params[:user][:name].downcase) + "' AND password = '") + params[:user][:password]) + "'"))

See the Ruby Security Guide for more information and Rails-SQLi.org for many examples of SQL injection in Rails.

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

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 that the cyclomatic complexity of methods is not higher than the configured maximum. The cyclomatic complexity is the number of linearly independent paths through a method. The algorithm counts decision points and adds one.

An if statement (or unless or ?:) increases the complexity by one. An else branch does not, since it doesn't add a decision point. The && operator (or keyword and) can be converted to a nested if statement, and ||/or is shorthand for a sequence of ifs, so they also add one. Loops can be said to have an exit condition, so they add one.

This cop tries to produce a complexity score that's a measure of the complexity the reader experiences when looking at a method. For that reason it considers when nodes as something that doesn't add as much complexity as an if or a &&. Except if it's one of those special case/when constructs where there's no expression after case. Then the cop treats it as an if/elsif/elsif... and lets all the when nodes count. In contrast to the CyclomaticComplexity cop, this cop considers else nodes as adding complexity.

Example:

def my_method                   # 1
  if cond                       # 1
    case var                    # 2 (0.8 + 4 * 0.2, rounded)
    when 1 then func_one
    when 2 then func_two
    when 3 then func_three
    when 4..10 then func_other
    end
  else                          # 1
    do_something until a && b   # 2
  end                           # ===
end                             # 7 complexity points

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

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 that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks if the length of a block exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable. The cop can be configured to ignore blocks passed to certain methods.

This cop checks if the length of a block exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable. The cop can be configured to ignore blocks passed to certain methods.

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

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

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 methods which skip validations which are listed in http://guides.rubyonrails.org/active_record_validations.html#skipping-validations

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_attributes(website: 'example.com')
FileUtils.touch('file')

This cop checks for uses of each_key and each_value Hash methods.

Note: If you have an array of two-element arrays, you can put parentheses around the block arguments to indicate that you're not working with a hash, and suppress RuboCop offenses.

Example:

# bad
hash.keys.each { |k| p k }
hash.values.each { |v| p v }
hash.each { |k, _v| p k }
hash.each { |_k, v| p v }

# good
hash.each_key { |k| p k }
hash.each_value { |v| p v }

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

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_attributes(website: 'example.com')
FileUtils.touch('file')

This cop checks dynamic find_by_* methods. Use find_by instead of dynamic method. See. https://github.com/bbatsov/rails-style-guide#find_by

Example:

# bad
User.find_by_name(name)

# bad
User.find_by_name_and_email(name)

# bad
User.find_by_email!(name)

# good
User.find_by(name: name)

# good
User.find_by(name: name, email: email)

# good
User.find_by!(email: email)

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

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_attributes(website: 'example.com')
FileUtils.touch('file')

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

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_attributes(website: 'example.com')
FileUtils.touch('file')

This cop looks for uses of the for keyword, or each method. The preferred alternative is set in the EnforcedStyle configuration parameter. An each call with a block on a single line is always allowed, however.

This cop checks for the use of Time methods without zone.

Built on top of Ruby on Rails style guide (https://github.com/bbatsov/rails-style-guide#time) and the article http://danilenko.org/2012/7/6/rails_timezones/ .

Two styles are supported for this cop. When EnforcedStyle is 'strict' then only use of Time.zone is allowed.

When EnforcedStyle is 'flexible' then it's also allowed to use Time.intimezone.

Example:

# always offense
Time.now
Time.parse('2015-03-02 19:05:37')

# no offense
Time.zone.now
Time.zone.parse('2015-03-02 19:05:37')

# no offense only if style is 'flexible'
Time.current
DateTime.strptime(str, "%Y-%m-%d %H:%M %Z").in_time_zone
Time.at(timestamp).in_time_zone

This cop checks for every useless assignment to local variable in every scope. The basic idea for this cop was from the warning of ruby -cw:

assigned but unused variable - foo

Currently this cop has advanced logic that detects unreferenced reassignments and properly handles varied cases such as branch, loop, rescue, ensure, etc.

Example:

# bad

def some_method
  some_var = 1
  do_something
end

Example:

# good

def some_method
  some_var = 1
  do_something(some_var)
end

This cop checks for the presence of parentheses around ternary conditions. It is configurable to enforce inclusion or omission of parentheses using EnforcedStyle. Omission is only enforced when removing the parentheses won't cause a different behavior.

Example: EnforcedStyle: requirenoparentheses (default)

# bad
foo = (bar?) ? a : b
foo = (bar.baz?) ? a : b
foo = (bar && baz) ? a : b

# good
foo = bar? ? a : b
foo = bar.baz? ? a : b
foo = bar && baz ? a : b

Example: EnforcedStyle: require_parentheses

# bad
foo = bar? ? a : b
foo = bar.baz? ? a : b
foo = bar && baz ? a : b

# good
foo = (bar?) ? a : b
foo = (bar.baz?) ? a : b
foo = (bar && baz) ? a : b

Example: EnforcedStyle: requireparentheseswhen_complex

# bad
foo = (bar?) ? a : b
foo = (bar.baz?) ? a : b
foo = bar && baz ? a : b

# good
foo = bar? ? a : b
foo = bar.baz? ? a : b
foo = (bar && baz) ? a : b

This cop checks for every useless assignment to local variable in every scope. The basic idea for this cop was from the warning of ruby -cw:

assigned but unused variable - foo

Currently this cop has advanced logic that detects unreferenced reassignments and properly handles varied cases such as branch, loop, rescue, ensure, etc.

Example:

# bad

def some_method
  some_var = 1
  do_something
end

Example:

# good

def some_method
  some_var = 1
  do_something(some_var)
end

This cop checks for the use of Time methods without zone.

Built on top of Ruby on Rails style guide (https://github.com/bbatsov/rails-style-guide#time) and the article http://danilenko.org/2012/7/6/rails_timezones/ .

Two styles are supported for this cop. When EnforcedStyle is 'strict' then only use of Time.zone is allowed.

When EnforcedStyle is 'flexible' then it's also allowed to use Time.intimezone.

Example:

# always offense
Time.now
Time.parse('2015-03-02 19:05:37')

# no offense
Time.zone.now
Time.zone.parse('2015-03-02 19:05:37')

# no offense only if style is 'flexible'
Time.current
DateTime.strptime(str, "%Y-%m-%d %H:%M %Z").in_time_zone
Time.at(timestamp).in_time_zone

This cop checks for the use of Time methods without zone.

Built on top of Ruby on Rails style guide (https://github.com/bbatsov/rails-style-guide#time) and the article http://danilenko.org/2012/7/6/rails_timezones/ .

Two styles are supported for this cop. When EnforcedStyle is 'strict' then only use of Time.zone is allowed.

When EnforcedStyle is 'flexible' then it's also allowed to use Time.intimezone.

Example:

# always offense
Time.now
Time.parse('2015-03-02 19:05:37')

# no offense
Time.zone.now
Time.zone.parse('2015-03-02 19:05:37')

# no offense only if style is 'flexible'
Time.current
DateTime.strptime(str, "%Y-%m-%d %H:%M %Z").in_time_zone
Time.at(timestamp).in_time_zone

Use a guard clause instead of wrapping the code inside a conditional expression

Example:

# bad
def test
  if something
    work
  end
end

# good
def test
  return unless something
  work
end

# also good
def test
  work if something
end

# bad
if something
  raise 'exception'
else
  ok
end

# good
raise 'exception' if something
ok

This cop checks for every useless assignment to local variable in every scope. The basic idea for this cop was from the warning of ruby -cw:

assigned but unused variable - foo

Currently this cop has advanced logic that detects unreferenced reassignments and properly handles varied cases such as branch, loop, rescue, ensure, etc.

Example:

# bad

def some_method
  some_var = 1
  do_something
end

Example:

# good

def some_method
  some_var = 1
  do_something(some_var)
end

This cop checks for uses of DateTime that should be replaced by Date or Time.

Example:

# bad - uses `DateTime` for current time
DateTime.now

# good - uses `Time` for current time
Time.now

# bad - uses `DateTime` for modern date
DateTime.iso8601('2016-06-29')

# good - uses `Date` for modern date
Date.iso8601('2016-06-29')

# good - uses `DateTime` with start argument for historical date
DateTime.iso8601('1751-04-23', Date::ENGLAND)

If the else branch of a conditional consists solely of an if node, it can be combined with the else to become an elsif. This helps to keep the nesting level from getting too deep.

Example:

# bad
if condition_a
  action_a
else
  if condition_b
    action_b
  else
    action_c
  end
end

# good
if condition_a
  action_a
elsif condition_b
  action_b
else
  action_c
end

This cop checks for uses of DateTime that should be replaced by Date or Time.

Example:

# bad - uses `DateTime` for current time
DateTime.now

# good - uses `Time` for current time
Time.now

# bad - uses `DateTime` for modern date
DateTime.iso8601('2016-06-29')

# good - uses `Date` for modern date
Date.iso8601('2016-06-29')

# good - uses `DateTime` with start argument for historical date
DateTime.iso8601('1751-04-23', Date::ENGLAND)

This cop checks for the use of Time methods without zone.

Built on top of Ruby on Rails style guide (https://github.com/bbatsov/rails-style-guide#time) and the article http://danilenko.org/2012/7/6/rails_timezones/ .

Two styles are supported for this cop. When EnforcedStyle is 'strict' then only use of Time.zone is allowed.

When EnforcedStyle is 'flexible' then it's also allowed to use Time.intimezone.

Example:

# always offense
Time.now
Time.parse('2015-03-02 19:05:37')

# no offense
Time.zone.now
Time.zone.parse('2015-03-02 19:05:37')

# no offense only if style is 'flexible'
Time.current
DateTime.strptime(str, "%Y-%m-%d %H:%M %Z").in_time_zone
Time.at(timestamp).in_time_zone

If the else branch of a conditional consists solely of an if node, it can be combined with the else to become an elsif. This helps to keep the nesting level from getting too deep.

Example:

# bad
if condition_a
  action_a
else
  if condition_b
    action_b
  else
    action_c
  end
end

# good
if condition_a
  action_a
elsif condition_b
  action_b
else
  action_c
end

This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

This cop checks for the use of Time methods without zone.

Built on top of Ruby on Rails style guide (https://github.com/bbatsov/rails-style-guide#time) and the article http://danilenko.org/2012/7/6/rails_timezones/ .

Two styles are supported for this cop. When EnforcedStyle is 'strict' then only use of Time.zone is allowed.

When EnforcedStyle is 'flexible' then it's also allowed to use Time.intimezone.

Example:

# always offense
Time.now
Time.parse('2015-03-02 19:05:37')

# no offense
Time.zone.now
Time.zone.parse('2015-03-02 19:05:37')

# no offense only if style is 'flexible'
Time.current
DateTime.strptime(str, "%Y-%m-%d %H:%M %Z").in_time_zone
Time.at(timestamp).in_time_zone