# Purell Purell is a tiny Go library to normalize URLs. It returns a pure URL. Pure-ell. Sanitizer and all. Yeah, I know... Based on the [wikipedia paper][wiki] and the [RFC 3986 document][rfc]. [![build status](https://secure.travis-ci.org/PuerkitoBio/purell.png)](http://travis-ci.org/PuerkitoBio/purell) ## Install `go get github.com/PuerkitoBio/purell` ## Changelog * **2016-11-14 (v1.1.0)** : IDN: Conform to RFC 5895: Fold character width (thanks to @beeker1121). * **2016-07-27 (v1.0.0)** : Normalize IDN to ASCII (thanks to @zenovich). * **2015-02-08** : Add fix for relative paths issue ([PR #5][pr5]) and add fix for unnecessary encoding of reserved characters ([see issue #7][iss7]). * **v0.2.0** : Add benchmarks, Attempt IDN support. * **v0.1.0** : Initial release. ## Examples From `example_test.go` (note that in your code, you would import "github.com/PuerkitoBio/purell", and would prefix references to its methods and constants with "purell."): ```go package purell import ( "fmt" "net/url" ) func ExampleNormalizeURLString() { if normalized, err := NormalizeURLString("hTTp://someWEBsite.com:80/Amazing%3f/url/", FlagLowercaseScheme|FlagLowercaseHost|FlagUppercaseEscapes); err != nil { panic(err) } else { fmt.Print(normalized) } // Output: http://somewebsite.com:80/Amazing%3F/url/ } func ExampleMustNormalizeURLString() { normalized := MustNormalizeURLString("hTTpS://someWEBsite.com:443/Amazing%fa/url/", FlagsUnsafeGreedy) fmt.Print(normalized) // Output: http://somewebsite.com/Amazing%FA/url } func ExampleNormalizeURL() { if u, err := url.Parse("Http://SomeUrl.com:8080/a/b/.././c///g?c=3&a=1&b=9&c=0#target"); err != nil { panic(err) } else { normalized := NormalizeURL(u, FlagsUsuallySafeGreedy|FlagRemoveDuplicateSlashes|FlagRemoveFragment) fmt.Print(normalized) } // Output: http://someurl.com:8080/a/c/g?c=3&a=1&b=9&c=0 } ``` ## API As seen in the examples above, purell offers three methods, `NormalizeURLString(string, NormalizationFlags) (string, error)`, `MustNormalizeURLString(string, NormalizationFlags) (string)` and `NormalizeURL(*url.URL, NormalizationFlags) (string)`. They all normalize the provided URL based on the specified flags. Here are the available flags: ```go const ( // Safe normalizations FlagLowercaseScheme NormalizationFlags = 1 << iota // HTTP://host -> http://host, applied by default in Go1.1 FlagLowercaseHost // http://HOST -> http://host FlagUppercaseEscapes // http://host/t%ef -> http://host/t%EF FlagDecodeUnnecessaryEscapes // http://host/t%41 -> http://host/tA FlagEncodeNecessaryEscapes // http://host/!"#$ -> http://host/%21%22#$ FlagRemoveDefaultPort // http://host:80 -> http://host FlagRemoveEmptyQuerySeparator // http://host/path? -> http://host/path // Usually safe normalizations FlagRemoveTrailingSlash // http://host/path/ -> http://host/path FlagAddTrailingSlash // http://host/path -> http://host/path/ (should choose only one of these add/remove trailing slash flags) FlagRemoveDotSegments // http://host/path/./a/b/../c -> http://host/path/a/c // Unsafe normalizations FlagRemoveDirectoryIndex // http://host/path/index.html -> http://host/path/ FlagRemoveFragment // http://host/path#fragment -> http://host/path FlagForceHTTP // https://host -> http://host FlagRemoveDuplicateSlashes // http://host/path//a///b -> http://host/path/a/b FlagRemoveWWW // http://www.host/ -> http://host/ FlagAddWWW // http://host/ -> http://www.host/ (should choose only one of these add/remove WWW flags) FlagSortQuery // http://host/path?c=3&b=2&a=1&b=1 -> http://host/path?a=1&b=1&b=2&c=3 // Normalizations not in the wikipedia article, required to cover tests cases // submitted by jehiah FlagDecodeDWORDHost // http://1113982867 -> http://66.102.7.147 FlagDecodeOctalHost // http://0102.0146.07.0223 -> http://66.102.7.147 FlagDecodeHexHost // http://0x42660793 -> http://66.102.7.147 FlagRemoveUnnecessaryHostDots // http://.host../path -> http://host/path FlagRemoveEmptyPortSeparator // http://host:/path -> http://host/path // Convenience set of safe normalizations FlagsSafe NormalizationFlags = FlagLowercaseHost | FlagLowercaseScheme | FlagUppercaseEscapes | FlagDecodeUnnecessaryEscapes | FlagEncodeNecessaryEscapes | FlagRemoveDefaultPort | FlagRemoveEmptyQuerySeparator // For convenience sets, "greedy" uses the "remove trailing slash" and "remove www. prefix" flags, // while "non-greedy" uses the "add (or keep) the trailing slash" and "add www. prefix". // Convenience set of usually safe normalizations (includes FlagsSafe) FlagsUsuallySafeGreedy NormalizationFlags = FlagsSafe | FlagRemoveTrailingSlash | FlagRemoveDotSegments FlagsUsuallySafeNonGreedy NormalizationFlags = FlagsSafe | FlagAddTrailingSlash | FlagRemoveDotSegments // Convenience set of unsafe normalizations (includes FlagsUsuallySafe) FlagsUnsafeGreedy NormalizationFlags = FlagsUsuallySafeGreedy | FlagRemoveDirectoryIndex | FlagRemoveFragment | FlagForceHTTP | FlagRemoveDuplicateSlashes | FlagRemoveWWW | FlagSortQuery FlagsUnsafeNonGreedy NormalizationFlags = FlagsUsuallySafeNonGreedy | FlagRemoveDirectoryIndex | FlagRemoveFragment | FlagForceHTTP | FlagRemoveDuplicateSlashes | FlagAddWWW | FlagSortQuery // Convenience set of all available flags FlagsAllGreedy = FlagsUnsafeGreedy | FlagDecodeDWORDHost | FlagDecodeOctalHost | FlagDecodeHexHost | FlagRemoveUnnecessaryHostDots | FlagRemoveEmptyPortSeparator FlagsAllNonGreedy = FlagsUnsafeNonGreedy | FlagDecodeDWORDHost | FlagDecodeOctalHost | FlagDecodeHexHost | FlagRemoveUnnecessaryHostDots | FlagRemoveEmptyPortSeparator ) ``` For convenience, the set of flags `FlagsSafe`, `FlagsUsuallySafe[Greedy|NonGreedy]`, `FlagsUnsafe[Greedy|NonGreedy]` and `FlagsAll[Greedy|NonGreedy]` are provided for the similarly grouped normalizations on [wikipedia's URL normalization page][wiki]. You can add (using the bitwise OR `|` operator) or remove (using the bitwise AND NOT `&^` operator) individual flags from the sets if required, to build your own custom set. The [full godoc reference is available on gopkgdoc][godoc]. Some things to note: * `FlagDecodeUnnecessaryEscapes`, `FlagEncodeNecessaryEscapes`, `FlagUppercaseEscapes` and `FlagRemoveEmptyQuerySeparator` are always implicitly set, because internally, the URL string is parsed as an URL object, which automatically decodes unnecessary escapes, uppercases and encodes necessary ones, and removes empty query separators (an unnecessary `?` at the end of the url). So this operation cannot **not** be done. For this reason, `FlagRemoveEmptyQuerySeparator` (as well as the other three) has been included in the `FlagsSafe` convenience set, instead of `FlagsUnsafe`, where Wikipedia puts it. * The `FlagDecodeUnnecessaryEscapes` decodes the following escapes (*from -> to*): - %24 -> $ - %26 -> & - %2B-%3B -> +,-./0123456789:; - %3D -> = - %40-%5A -> @ABCDEFGHIJKLMNOPQRSTUVWXYZ - %5F -> _ - %61-%7A -> abcdefghijklmnopqrstuvwxyz - %7E -> ~ * When the `NormalizeURL` function is used (passing an URL object), this source URL object is modified (that is, after the call, the URL object will be modified to reflect the normalization). * The *replace IP with domain name* normalization (`http://208.77.188.166/ → http://www.example.com/`) is obviously not possible for a library without making some network requests. This is not implemented in purell. * The *remove unused query string parameters* and *remove default query parameters* are also not implemented, since this is a very case-specific normalization, and it is quite trivial to do with an URL object. ### Safe vs Usually Safe vs Unsafe Purell allows you to control the level of risk you take while normalizing an URL. You can aggressively normalize, play it totally safe, or anything in between. Consider the following URL: `HTTPS://www.RooT.com/toto/t%45%1f///a/./b/../c/?z=3&w=2&a=4&w=1#invalid` Normalizing with the `FlagsSafe` gives: `https://www.root.com/toto/tE%1F///a/./b/../c/?z=3&w=2&a=4&w=1#invalid` With the `FlagsUsuallySafeGreedy`: `https://www.root.com/toto/tE%1F///a/c?z=3&w=2&a=4&w=1#invalid` And with `FlagsUnsafeGreedy`: `http://root.com/toto/tE%1F/a/c?a=4&w=1&w=2&z=3` ## TODOs * Add a class/default instance to allow specifying custom directory index names? At the moment, removing directory index removes `(^|/)((?:default|index)\.\w{1,4})$`. ## Thanks / Contributions @rogpeppe @jehiah @opennota @pchristopher1275 @zenovich @beeker1121 ## License The [BSD 3-Clause license][bsd]. [bsd]: http://opensource.org/licenses/BSD-3-Clause [wiki]: http://en.wikipedia.org/wiki/URL_normalization [rfc]: http://tools.ietf.org/html/rfc3986#section-6 [godoc]: http://go.pkgdoc.org/github.com/PuerkitoBio/purell [pr5]: https://github.com/PuerkitoBio/purell/pull/5 [iss7]: https://github.com/PuerkitoBio/purell/issues/7