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diff --git a/doc/security.rdoc b/doc/security.rdoc deleted file mode 100644 index d8efca0042..0000000000 --- a/doc/security.rdoc +++ /dev/null @@ -1,144 +0,0 @@ -= Ruby Security - -The Ruby programming language is large and complex and there are many security -pitfalls often encountered by newcomers and experienced Rubyists alike. - -This document aims to discuss many of these pitfalls and provide more secure -alternatives where applicable. - -Please check the full list of publicly known CVEs and how to correctly report a -security vulnerability, at: http://www.ruby-lang.org/en/security/ -Japanese version is here: http://www.ruby-lang.org/ja/security/ - -Security vulnerabilities should be reported via an email to -mailto:security@ruby-lang.org ({the PGP public -key}[http://www.ruby-lang.org/security.asc]), which is a private mailing list. -Reported problems will be published after fixes. - -== <code>$SAFE</code> - -Ruby provides a mechanism to restrict what operations can be performed by Ruby -code in the form of the <code>$SAFE</code> variable. - -However, <code>$SAFE</code> does not provide a secure environment for executing -untrusted code. - -If you need to execute untrusted code, you should use an operating system level -sandboxing mechanism. On Linux, ptrace or LXC can be used to sandbox -potentially malicious code. Other similar mechanisms exist on every major -operating system. - -== +Marshal.load+ - -Ruby's +Marshal+ module provides methods for serializing and deserializing Ruby -object trees to and from a binary data format. - -Never use +Marshal.load+ to deserialize untrusted or user supplied data. -Because +Marshal+ can deserialize to almost any Ruby object and has full -control over instance variables, it is possible to craft a malicious payload -that executes code shortly after deserialization. - -If you need to deserialize untrusted data, you should use JSON as it is only -capable of returning 'primitive' types such as strings, arrays, hashes, numbers -and nil. If you need to deserialize other classes, you should handle this -manually. Never deserialize to a user specified class. - -== YAML - -YAML is a popular human readable data serialization format used by many Ruby -programs for configuration and database persistence of Ruby object trees. - -Similar to +Marshal+, it is able to deserialize into arbitrary Ruby classes. -For example, the following YAML data will create an +ERB+ object when -deserialized: - - !ruby/object:ERB - src: puts `uname` - -Because of this, many of the security considerations applying to Marshal are -also applicable to YAML. Do not use YAML to deserialize untrusted data. - -== Symbols - -Symbols are often seen as syntax sugar for simple strings, but they play a much -more crucial role. The MRI Ruby implementation uses Symbols internally for -method, variable and constant names. The reason for this is that symbols are -simply integers with names attached to them, so they are faster to look up in -hashtables. - -Once a symbol is created, the memory used by it is never freed. If you convert -user input to symbols with +to_sym+ or +intern+, it is possible for an attacker -to mount a denial of service attack against your application by flooding it -with unique strings. Because each string is kept in memory until the Ruby -process exits, this will cause memory consumption to grow and grow until Ruby -runs out of memory and crashes. - -Be careful with passing user input to methods such as +send+, -+instance_variable_get+ or +_set+, +const_get+ or +_set+, etc. as these methods -will convert string parameters to symbols internally and pose the same DoS -potential as direct conversion through +to_sym+/+intern+. - -The workaround to this is simple - don't convert user input to symbols. You -should attempt to leave user input in string form instead. - -== Regular expressions - -Ruby's regular expression syntax has some minor differences when compared to -other languages. In Ruby, the <code>^</code> and <code>$</code> anchors do not -refer to the beginning and end of the string, rather the beginning and end of a -*line*. - -This means that if you're using a regular expression like -<code>/^[a-z]+$/</code> to restrict a string to only letters, an attacker can -bypass this check by passing a string containing a letter, then a newline, then -any string of their choosing. - -If you want to match the beginning and end of the entire string in Ruby, use -the anchors +\A+ and +\z+. - -== +eval+ - -Never pass untrusted or user controlled input to +eval+. - -Unless you are implementing a REPL like +irb+ or +pry+, +eval+ is almost -certainly not what you want. Do not attempt to filter user input before passing -it to +eval+ - this approach is fraught with danger and will most likely open -your application up to a serious remote code execution vulnerability. - -== +send+ - -'Global functions' in Ruby (+puts+, +exit+, etc.) are actually private instance -methods on +Object+. This means it is possible to invoke these methods with -+send+, even if the call to +send+ has an explicit receiver. - -For example, the following code snippet writes "Hello world" to the terminal: - - 1.send(:puts, "Hello world") - -You should never call +send+ with user supplied input as the first parameter. -Doing so can introduce a denial of service vulnerability: - - foo.send(params[:bar]) # params[:bar] is "exit!" - -If an attacker can control the first two arguments to +send+, remote code -execution is possible: - - # params is { :a => "eval", :b => "...ruby code to be executed..." } - foo.send(params[:a], params[:b]) - -When dispatching a method call based on user input, carefully verify that the -method name. If possible, check it against a whitelist of safe method names. - -Note that the use of +public_send+ is also dangerous, as +send+ itself is -public: - - 1.public_send("send", "eval", "...ruby code to be executed...") - -== DRb - -As DRb allows remote clients to invoke arbitrary methods, it is not suitable to -expose to untrusted clients. - -When using DRb, try to avoid exposing it over the network if possible. If this -isn't possible and you need to expose DRb to the world, you *must* configure an -appropriate security policy with <code>DRb::ACL</code>. |
