Unvalidated redirects and forwards are #10 on the OWASP Top Ten.

Redirects which rely on user-supplied values can be used to "spoof" websites or hide malicious links in otherwise harmless-looking URLs. They can also allow access to restricted areas of a site if the destination is not validated.

Brakeman will raise warnings whenever redirect_to appears to be used with a user-supplied value that may allow them to change the :host option.

For example,

redirect_to params.merge(:action => :home)

will create a warning like

Possible unprotected redirect near line 46: redirect_to(params)

This is because params could contain :host => 'evilsite.com' which would redirect away from your site and to a malicious site.

If the first argument to redirect_to is a hash, then adding :only_path => true will limit the redirect to the current host. Another option is to specify the host explicitly.

redirect_to params.merge(:only_path => true)

redirect_to params.merge(:host => 'myhost.com')

If the first argument is a string, then it is possible to parse the string and extract the path:

redirect_to URI.parse(some_url).path

If the URL does not contain a protocol (e.g., http://), then you will probably get unexpected results, as redirect_to will prepend the current host name and a protocol.

Unvalidated redirects and forwards are #10 on the OWASP Top Ten.

Redirects which rely on user-supplied values can be used to "spoof" websites or hide malicious links in otherwise harmless-looking URLs. They can also allow access to restricted areas of a site if the destination is not validated.

Brakeman will raise warnings whenever redirect_to appears to be used with a user-supplied value that may allow them to change the :host option.

For example,

redirect_to params.merge(:action => :home)

will create a warning like

Possible unprotected redirect near line 46: redirect_to(params)

This is because params could contain :host => 'evilsite.com' which would redirect away from your site and to a malicious site.

If the first argument to redirect_to is a hash, then adding :only_path => true will limit the redirect to the current host. Another option is to specify the host explicitly.

redirect_to params.merge(:only_path => true)

redirect_to params.merge(:host => 'myhost.com')

If the first argument is a string, then it is possible to parse the string and extract the path:

redirect_to URI.parse(some_url).path

If the URL does not contain a protocol (e.g., http://), then you will probably get unexpected results, as redirect_to will prepend the current host name and a protocol.

Unvalidated redirects and forwards are #10 on the OWASP Top Ten.

Redirects which rely on user-supplied values can be used to "spoof" websites or hide malicious links in otherwise harmless-looking URLs. They can also allow access to restricted areas of a site if the destination is not validated.

Brakeman will raise warnings whenever redirect_to appears to be used with a user-supplied value that may allow them to change the :host option.

For example,

redirect_to params.merge(:action => :home)

will create a warning like

Possible unprotected redirect near line 46: redirect_to(params)

This is because params could contain :host => 'evilsite.com' which would redirect away from your site and to a malicious site.

If the first argument to redirect_to is a hash, then adding :only_path => true will limit the redirect to the current host. Another option is to specify the host explicitly.

redirect_to params.merge(:only_path => true)

redirect_to params.merge(:host => 'myhost.com')

If the first argument is a string, then it is possible to parse the string and extract the path:

redirect_to URI.parse(some_url).path

If the URL does not contain a protocol (e.g., http://), then you will probably get unexpected results, as redirect_to will prepend the current host name and a protocol.

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 method exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable.

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

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 cops checks the indentation of comments.

Example:

# bad
  # comment here
def method_name
end

  # comment here
a = 'hello'

# yet another comment
  if true
    true
  end

# good
# comment here
def method_name
end

# comment here
a = 'hello'

# yet another comment
if true
  true
end

This cop checks the style of children definitions at classes and modules. Basically there are two different styles:

Example: EnforcedStyle: nested (default)

# good
# have each child on its own line
class Foo
  class Bar
  end
end

Example: EnforcedStyle: compact

# good
# combine definitions as much as possible
class Foo::Bar
end

The compact style is only forced for classes/modules with one child.

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"

This cops 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

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"

This cops 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

This cops checks for inconsistent indentation.

Example:

class A
  def test
    puts 'hello'
     puts 'world'
  end
end

This cops checks for inconsistent indentation.

Example:

class A
  def test
    puts 'hello'
     puts 'world'
  end
end

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"

This cops checks the indentation of comments.

Example:

# bad
  # comment here
def method_name
end

  # comment here
a = 'hello'

# yet another comment
  if true
    true
  end

# good
# comment here
def method_name
end

# comment here
a = 'hello'

# yet another comment
if true
  true
end

This cops 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

This cop checks for non-nil checks, which are usually redundant.

Example:

# bad
if x != nil
end

# good (when not allowing semantic changes)
# bad (when allowing semantic changes)
if !x.nil?
end

# good (when allowing semantic changes)
if x
end

Non-nil checks are allowed if they are the final nodes of predicate.

# good
def signed_in?
  !current_user.nil?
end

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"

This cop checks for missing top-level documentation of classes and modules. Classes with no body are exempt from the check and so are namespace modules - modules that have nothing in their bodies except classes, other modules, or constant definitions.

The documentation requirement is annulled if the class or module has a "#:nodoc:" comment next to it. Likewise, "#:nodoc: all" does the same for all its children.

Example:

# bad
class Person
  # ...
end

# good
# Description/Explanation of Person class
class Person
  # ...
end

This cops 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