src/IPv4Pattern.hs

   1 {-# LANGUAGE FlexibleInstances #-}
   2
   3 -- | An IPv4 address pattern has four fields separated by ".".  Each
   4 --   field is either a decimal number, or a sequence inside "[]" that
   5 --   contains one or more ";"-separated decimal numbers or
   6 --   number..number ranges.
   7 --
   8 --   Thus, any pattern field can be a sequence inside "[]", but a "[]"
   9 --   sequence cannot span multiple address fields, and a pattern field
  10 --   cannot contain both a number and a "[]" sequence at the same
  11 --   time.
  12 --
  13 --   This means that the pattern 1.2.[3.4] is not valid (the sequence
  14 --   [3.4] cannot span two address fields) and the pattern
  15 --   1.2.3.3[6..9] is also not valid (the last field cannot be both
  16 --   number 3 and sequence [6..9] at the same time).
  17 --
  18 --   The syntax for IPv4 patterns is as follows:
  19 --
  20 --   v4pattern = v4field "." v4field "." v4field "." v4field
  21 --   v4field = v4octet | "[" v4sequence "]"
  22 --   v4octet = any decimal number in the range 0 through 255
  23 --   v4sequence = v4seq_member | v4sequence ";" v4seq_member
  24 --   v4seq_member = v4octet | v4octet ".." v4octet
  25 --
  26 module IPv4Pattern
  27 where
  28
  29 import Test.Tasty ( TestTree, testGroup )
  30 import Test.Tasty.HUnit ( (@?=), testCase )
  31 import Text.Parsec
  32 import Text.Parsec.String ( Parser )
  33 import Text.Read ( readMaybe )
  34
  35
  36 class Pretty a where
  37   -- | Obtain a pretty 'String' representation of the given thingy.
  38   prettyshow :: a -> String
  39
  40   -- | Pretty-print the given thingy.
  41   pp :: a -> IO ()
  42   pp = putStrLn . prettyshow
  43
  44
  45 -- | Define a 'Pretty' instance for the result of 'parse'. This lets
  46 --   us pretty-print the result of a parse attempt without worrying
  47 --   about whether or not it failed. If the parse failed, you get the
  48 --   same output that you usually would. Otherwise we pretty-print the
  49 --   parsed value.
  50 --
  51 instance Pretty a => Pretty (Either ParseError a) where
  52   prettyshow (Left err) = show err
  53   prettyshow (Right v)  = prettyshow v
  54
  55
  56 -- * Octets
  57
  58 -- | An ipv4 octet; that is, an integer between @0@ and @255@
  59 --   inclusive. This is the data type corresponding to a \"v4octet\"
  60 --   in the postscreen parser.
  61 --
  62 newtype IPv4Octet = IPv4Octet Int
  63   deriving (Eq, Show)
  64
  65
  66 instance Pretty IPv4Octet where
  67   prettyshow (IPv4Octet x) = show x
  68
  69
  70 -- | Parse an IPv4 octet, which should contain a string of digits.
  71 --   Should fail if the parsed integer does not lie between @0@ and
  72 --   @255@ inclusive.
  73 --
  74 --   ==== _Examples_
  75 --
  76 --   Standard octets are parsed correctly:
  77 --
  78 --   >>> parseTest v4octet "0"
  79 --   IPv4Octet 0
  80 --
  81 --   >>> parseTest v4octet "127"
  82 --   IPv4Octet 127
  83 --
  84 --   >>> parseTest v4octet "255"
  85 --   IPv4Octet 255
  86 --
  87 --   Non-digit input throws an error:
  88 --
  89 --   >>> parseTest v4octet "Hello, World!"
  90 --   parse error at (line 1, column 1):
  91 --   unexpected "H"
  92 --   expecting digit
  93 --
  94 --   If we're given an integer outside the range @0..255@ (i.e. not a
  95 --   valid octet), we fail:
  96 --
  97 --   >>> parseTest v4octet "9000"
  98 --   parse error at (line 1, column 5):
  99 --   unexpected end of input
 100 --   expecting digit
 101 --   Octet "9000" must be between 0 and 255.
 102 --
 103 v4octet :: Parser IPv4Octet
 104 v4octet = do
 105   s <- many1 digit
 106   case ( readMaybe s :: Maybe Int ) of
 107     -- If "many1 digit" gives us a list of digits, we should be able
 108     -- to convert that to an Int! It will overflow rather than fail
 109     -- if the input is too big/small, so it should really always
 110     -- succeed.
 111     Nothing -> unexpected "readMaybe failed on a sequence of digits!"
 112
 113     -- If we got an Int, make sure it's actually a representation of
 114     -- an octet.
 115     Just k -> if 0 <= k && k <= 255
 116              then return (IPv4Octet k)
 117              else fail ("Octet \"" ++ (show k)
 118                                    ++ "\" must be between 0 and 255.")
 119
 120
 121
 122
 123 -- * Sequence members
 124
 125
 126 -- | An ipv4 \"sequence member\". A sequence member is either an
 127 --   integer (an octet) or a range of integers (contained in an
 128 --   octet). This data type corresponds to \"v4seq_member\" in the
 129 --   postscreen parser.
 130 --
 131 data IPv4SequenceMember =
 132   IPv4SequenceMemberOctet IPv4Octet
 133   | IPv4SequenceMemberOctetRange IPv4Octet IPv4Octet
 134   deriving (Eq, Show)
 135
 136
 137 instance Pretty IPv4SequenceMember where
 138   prettyshow (IPv4SequenceMemberOctet octet) = prettyshow octet
 139   prettyshow (IPv4SequenceMemberOctetRange octet1 octet2) =
 140     (prettyshow octet1) ++ ".." ++ (prettyshow octet2)
 141
 142
 143 -- | Parse an IPv4 \"sequence member\". A sequence member is either an
 144 --   octet, or a start..end sequence (like an enumeration, in Haskell).
 145 --
 146 --   ==== _Examples_
 147 --
 148 --   >>> parseTest v4seq_member "127"
 149 --   IPv4SequenceMemberOctet (IPv4Octet 127)
 150 --
 151 --   >>> parseTest v4seq_member "1..5"
 152 --   IPv4SequenceMemberOctetRange (IPv4Octet 1) (IPv4Octet 5)
 153 --
 154 v4seq_member :: Parser IPv4SequenceMember
 155 v4seq_member = try both <|> just_one
 156   where
 157     both = do
 158       oct1 <- v4octet
 159       _ <- string ".."
 160       oct2 <- v4octet
 161       return $ IPv4SequenceMemberOctetRange oct1 oct2
 162
 163     just_one = fmap IPv4SequenceMemberOctet v4octet
 164
 165
 166
 167 -- * Sequences
 168
 169 -- | An ipv4 \"sequence\". A sequence contains either a single
 170 --   \"sequence member\" (see 'IPv4SequenceMember'), or a sequence
 171 --   member along with another sequence. So, this is a potentially
 172 --   recursive definition. This type corresponds to \"v4sequence\" in
 173 --   the postscreen parser.
 174 --
 175 data IPv4Sequence =
 176   IPv4SequenceSingleMember IPv4SequenceMember
 177   | IPv4SequenceOptions IPv4SequenceMember IPv4Sequence
 178   deriving (Eq, Show)
 179
 180
 181 instance Pretty IPv4Sequence where
 182   prettyshow (IPv4SequenceSingleMember member) = prettyshow member
 183   prettyshow (IPv4SequenceOptions member subsequence) =
 184     (prettyshow member) ++ ";" ++ (prettyshow subsequence)
 185
 186
 187 -- | Parse an IPv4 \"sequence\". A sequence is whatever is allowed
 188 --   within square brackets. Basically it can be three things:
 189 --
 190 --     * An octet (number).
 191 --     * A range of addresses in start..end format.
 192 --     * An alternative, separated by a semicolon, where each side
 193 --       contains one of the previous two options.
 194 --
 195 --   ==== _Examples_
 196 --
 197 --   >>> parseTest v4sequence "1"
 198 --   IPv4SequenceSingleMember (IPv4SequenceMemberOctet (IPv4Octet 1))
 199 --
 200 --   >>> pp $ parse v4sequence "" "1..2"
 201 --   1..2
 202 --
 203 --   >>> pp $ parse v4sequence "" "1..2;8"
 204 --   1..2;8
 205 --
 206 v4sequence :: Parser IPv4Sequence
 207 v4sequence = try both <|> just_one -- Maybe sepBy is appropriate here?
 208   where
 209     both = do
 210       sm <- v4seq_member
 211       _ <- char ';'
 212       s <- v4sequence
 213       return $ IPv4SequenceOptions sm s
 214
 215     just_one = fmap IPv4SequenceSingleMember v4seq_member
 216
 217
 218
 219 -- * Fields
 220
 221 data IPv4Field = IPv4FieldOctet IPv4Octet | IPv4FieldSequence IPv4Sequence
 222   deriving (Eq, Show)
 223
 224
 225 instance Pretty IPv4Field where
 226   prettyshow (IPv4FieldOctet octet) = prettyshow octet
 227   prettyshow (IPv4FieldSequence seq) = "[" ++ (prettyshow seq) ++ "]"
 228
 229
 230 -- | Parse an IPv4 \"field\", which is either a boring old octet, or a
 231 --   'v4sequence' within square brackets.
 232 --
 233 --   ==== _Examples_
 234 --
 235 --   >>> parseTest v4field "127"
 236 --   IPv4FieldOctet (IPv4Octet 127)
 237 --
 238 --   >>> pp $ parse v4field "" "[127]"
 239 --   [127]
 240 --
 241 v4field :: Parser IPv4Field
 242 v4field = just_octet <|> brackets
 243   where
 244     just_octet = fmap IPv4FieldOctet v4octet
 245
 246     brackets = do
 247       _ <- char '['
 248       s <- v4sequence
 249       _ <- char ']'
 250       return $ IPv4FieldSequence s
 251
 252
 253
 254 -- * Patterns
 255
 256 data IPv4Pattern =
 257   IPv4Pattern IPv4Field IPv4Field IPv4Field IPv4Field
 258   deriving (Eq, Show)
 259
 260
 261 instance Pretty IPv4Pattern where
 262   prettyshow (IPv4Pattern f1 f2 f3 f4) =
 263     (prettyshow f1) ++ "."
 264                     ++ (prettyshow f2)
 265                     ++ "."
 266                     ++ (prettyshow f3)
 267                     ++ "."
 268                     ++ (prettyshow f4)
 269
 270
 271 -- | Parse an ipv4 address pattern. This consists of four fields,
 272 --   separated by periods, where a field is either a simple octet or a
 273 --   sequence.
 274 --
 275 --   See also: 'v4field', 'v4sequence'.
 276 --
 277 --   ==== _Examples_
 278 --
 279 --   >>> pp $ parse v4pattern "" "127.0.0.1"
 280 --   127.0.0.1
 281 --
 282 --   >>> pp $ parse v4pattern "" "127.0.[1..3].1"
 283 --   127.0.[1..3].1
 284 --
 285 --   >>> pp $ parse v4pattern "" "127.0.[1..3;8].1"
 286 --   127.0.[1..3;8].1
 287 --
 288 --   In the module intro, it is mentioned that this is invalid:
 289 --
 290 --   >>> parseTest v4pattern "1.2.[3.4]"
 291 --   parse error at (line 1, column 7):
 292 --   unexpected "."
 293 --   expecting digit or "]"
 294 --
 295 --   This one is /also/ invalid; however, we'll parse the valid part off
 296 --   the front of it:
 297 --
 298 --   >>> pp $ parse v4pattern "" "1.2.3.3[6..9]"
 299 --   1.2.3.3
 300 --
 301 v4pattern :: Parser IPv4Pattern
 302 v4pattern = do
 303   field1 <- v4field
 304   _ <- char '.'
 305   field2 <- v4field
 306   _ <- char '.'
 307   field3 <- v4field
 308   _ <- char '.'
 309   field4 <- v4field
 310   return $ IPv4Pattern field1 field2 field3 field4
 311
 312
 313
 314 -- * Enumeration
 315
 316 -- | Enumerate the members of an 'IPv4SequenceMember'. A sequence
 317 --   member is either an octet, which is easy to enumerate -- we just
 318 --   print it -- or an octet range whose members can be enumerated
 319 --   from least to greatest.
 320 --
 321 --   We enumerate strings instead of integers because the big picture
 322 --   is that we will be listing out patterns of ipv4 addresses, and
 323 --   those are represented as strings (dotted quad format).
 324 --
 325 --   ==== _Examples_
 326 --
 327 --   >>> let (Right r) = parse v4seq_member "" "127"
 328 --   >>> sequence_members r
 329 --   ["127"]
 330 --
 331 --   >>> let (Right r) = parse v4seq_member "" "127..135"
 332 --   >>> sequence_members r
 333 --   ["127","128","129","130","131","132","133","134","135"]
 334 --
 335 sequence_members :: IPv4SequenceMember -> [String]
 336 sequence_members (IPv4SequenceMemberOctet (IPv4Octet i)) = [show i]
 337 sequence_members (IPv4SequenceMemberOctetRange (IPv4Octet s) (IPv4Octet t)) =
 338   [show x | x <- [s .. t]]
 339
 340
 341 -- | Enumerate the members of an ipv4 sequence. These consist of
 342 --   either a single sequence member (in which case we delegate to
 343 --   'sequence_members'), or an \"option\" which is enumerated
 344 --   recursively.
 345 --
 346 --   ==== _Examples_
 347 --
 348 --   >>> let (Right r) = parse v4sequence "" "1"
 349 --   >>> sequences r
 350 --   ["1"]
 351 --
 352 --   >>> let (Right r) = parse v4sequence "" "1..2"
 353 --   >>> sequences r
 354 --   ["1","2"]
 355 --
 356 --   >>> let (Right r) = parse v4sequence "" "1..3;4;5..9"
 357 --   >>> sequences r
 358 --   ["1","2","3","4","5","6","7","8","9"]
 359 --
 360 sequences :: IPv4Sequence -> [String]
 361 sequences (IPv4SequenceSingleMember sm) =
 362   sequence_members sm
 363 sequences (IPv4SequenceOptions sm s) =
 364   (sequence_members sm) ++ (sequences s)
 365
 366
 367 -- | Enumerate the members of an 'IPv4Field'. If the field contains a
 368 --   single 'IPv4Octet', we simply 'show' it. Otherwise it contains an
 369 --   'IPv4FieldSequence', and we enumerate that recursively using
 370 --   'sequences'.
 371 --
 372 --   ==== _Examples_
 373 --
 374 --   >>> let (Right r) = parse v4field "" "1"
 375 --   >>> fields r
 376 --   ["1"]
 377 --
 378 --   >>> let (Right r) = parse v4field "" "[127..135]"
 379 --   >>> fields r
 380 --   ["127","128","129","130","131","132","133","134","135"]
 381 --
 382 fields :: IPv4Field -> [String]
 383 fields (IPv4FieldOctet (IPv4Octet i)) = [show i]
 384 fields (IPv4FieldSequence s) = sequences s
 385
 386
 387 -- | Enumerate the addresses represented by a given 'IPv4Pattern'.
 388 --
 389 --   A pattern contains four fields, sepearated by period
 390 --   characters. We want to list all possible combinations of
 391 --   addresses where the first octet comes from the first field, the
 392 --   second octet comes from the second field... and so on. To do
 393 --   this, we take advantage of the List monad and the fact that
 394 --   'fields' returns a list of 'String's.
 395 --
 396 --   ==== _Examples_
 397 --
 398 --   A single address:
 399 --
 400 --   >>> let (Right r) = parse v4pattern "" "127.0.0.1"
 401 --   >>> addresses r
 402 --   ["127.0.0.1"]
 403 --
 404 --   Anything between 127.0.0.2 and 127.0.0.4, and either 127.0.0.10
 405 --   or 127.0.0.11:
 406 --
 407 --   >>> let (Right r) = parse v4pattern "" "127.0.0.[2..4;10;11]"
 408 --   >>> addresses r
 409 --   ["127.0.0.2","127.0.0.3","127.0.0.4","127.0.0.10","127.0.0.11"]
 410 --
 411 addresses :: IPv4Pattern -> [String]
 412 addresses (IPv4Pattern field1 field2 field3 field4) = do
 413   f1 <- fields field1
 414   f2 <- fields field2
 415   f3 <- fields field3
 416   f4 <- fields field4
 417   return $ f1 ++ "." ++ f2 ++ "." ++ f3 ++ "." ++ f4
 418
 419
 420
 421 -- * Tests
 422
 423 v4octet_tests :: TestTree
 424 v4octet_tests =
 425   testGroup
 426     "v4octet tests"
 427     [ test_v4octet_single_digit_parsed ]
 428
 429 test_v4octet_single_digit_parsed :: TestTree
 430 test_v4octet_single_digit_parsed =
 431   testCase "a single digit is parsed as a v4octet" $ do
 432     -- Whatever, it's a test.
 433     let (Right actual) = parse v4octet "" "1"
 434     let expected = IPv4Octet 1
 435     actual @?= expected