module Net::IMAP::StringPrep

Regexps and utility methods for implementing stringprep profiles. The StringPrep algorithm is defined by RFC-3454. Each codepoint table defined in the RFC-3454 appendices is matched by a Regexp defined in this module.

Public Class Methods

[](table) click to toggle source

Returns a Regexp matching the given table name.

# File lib/net/imap/stringprep.rb, line 49
def self.[](table)
  Tables::REGEXPS.fetch(table)
end

Public Instance Methods

check_bidi!(string, c_8: false, profile: nil) click to toggle source

Checks that string obeys all of the “Bidirectional Characters” requirements in RFC-3454, §6:

The characters in StringPrep["C.8"] MUST be prohibited
If a string contains any RandALCat character, the string MUST NOT contain any LCat character.
If a string contains any RandALCat character, a RandALCat character MUST be the first character of the string, and a RandALCat character MUST be the last character of the string.

This is usually combined with check_prohibited!, so table “C.8” is only checked when c_8: true.

Raises either ProhibitedCodepoint or BidiStringError unless all requirements are met. profile is an optional string which will be added to any exception that is raised (it does not affect behavior).

# File lib/net/imap/stringprep.rb, line 144
def check_bidi!(string, c_8: false, profile: nil)
  check_prohibited!(string, "C.8", profile: profile) if c_8
  if Tables::BIDI_FAILS_REQ2.match?(string)
    raise BidiStringError.new(
      Tables::BIDI_DESC_REQ2, string: string, profile: profile,
    )
  elsif Tables::BIDI_FAILS_REQ3.match?(string)
    raise BidiStringError.new(
      Tables::BIDI_DESC_REQ3, string: string, profile: profile,
    )
  end
end

check_prohibited!(string, *tables, bidi: false, unassigned: "A.1", stored: false, profile: nil) click to toggle source

Checks string for any codepoint in tables. Raises a ProhibitedCodepoint describing the first matching table.

Also checks bidirectional characters, when bidi: true, which may raise a BidiStringError.

profile is an optional string which will be added to any exception that is raised (it does not affect behavior).

# File lib/net/imap/stringprep.rb, line 104
def check_prohibited!(string,
                      *tables,
                      bidi: false,
                      unassigned: "A.1",
                      stored: false,
                      profile: nil)
  tables  = Tables::TITLES.keys.grep(/^C/) if tables.empty?
  tables |= [unassigned] if stored
  tables |= %w[C.8] if bidi
  table   = tables.find {|t|
    case t
    when String then Tables::REGEXPS.fetch(t).match?(string)
    when Regexp then t.match?(string)
    else raise ArgumentError, "only table names and regexps can be checked"
    end
  }
  if table
    raise ProhibitedCodepoint.new(
      table, string: string, profile: profile
    )
  end
  check_bidi!(string, profile: profile) if bidi
end

map_tables!(string, *tables) click to toggle source

# File lib/net/imap/stringprep.rb, line 88
def map_tables!(string, *tables)
  tables.each do |table|
    regexp, replacements = Tables::MAPPINGS.fetch(table)
    string.gsub!(regexp, replacements)
  end
  string
end

stringprep(string, maps:, normalization:, prohibited:, **opts) click to toggle source

Map – For each character in the input, check if it has a mapping and, if so, replace it with its mapping. This is described in section 3.

Normalize – Possibly normalize the result of step 1 using Unicode normalization. This is described in section 4.

Prohibit – Check for any characters that are not allowed in the output. If any are found, return an error. This is described in section 5.

Check bidi – Possibly check for right-to-left characters, and if any are found, make sure that the whole string satisfies the requirements for bidirectional strings. If the string does not satisfy the requirements for bidirectional strings, return an error. This is described in section 6.

The above steps MUST be performed in the order given to comply with this specification.

# File lib/net/imap/stringprep.rb, line 76
def stringprep(string,
               maps:,
               normalization:,
               prohibited:,
               **opts)
  string = string.encode("UTF-8") # also dups (and raises invalid encoding)
  map_tables!(string, *maps)                     if maps
  string.unicode_normalize!(normalization)       if normalization
  check_prohibited!(string, *prohibited, **opts) if prohibited
  string
end