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75 lines
1.9 KiB
75 lines
1.9 KiB
9 years ago
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package handlers
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import (
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"net/http"
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"net/url"
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"strings"
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)
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type canonical struct {
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h http.Handler
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domain string
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code int
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}
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// CanonicalHost is HTTP middleware that re-directs requests to the canonical
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// domain. It accepts a domain and a status code (e.g. 301 or 302) and
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// re-directs clients to this domain. The existing request path is maintained.
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//
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// Note: If the provided domain is considered invalid by url.Parse or otherwise
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// returns an empty scheme or host, clients are not re-directed.
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//
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// Example:
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//
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// r := mux.NewRouter()
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// canonical := handlers.CanonicalHost("http://www.gorillatoolkit.org", 302)
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// r.HandleFunc("/route", YourHandler)
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//
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// log.Fatal(http.ListenAndServe(":7000", canonical(r)))
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//
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func CanonicalHost(domain string, code int) func(h http.Handler) http.Handler {
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fn := func(h http.Handler) http.Handler {
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return canonical{h, domain, code}
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}
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return fn
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}
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func (c canonical) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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dest, err := url.Parse(c.domain)
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if err != nil {
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// Call the next handler if the provided domain fails to parse.
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c.h.ServeHTTP(w, r)
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return
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}
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if dest.Scheme == "" || dest.Host == "" {
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// Call the next handler if the scheme or host are empty.
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// Note that url.Parse won't fail on in this case.
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c.h.ServeHTTP(w, r)
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return
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}
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if !strings.EqualFold(cleanHost(r.Host), dest.Host) {
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// Re-build the destination URL
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dest := dest.Scheme + "://" + dest.Host + r.URL.Path
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if r.URL.RawQuery != "" {
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dest += "?" + r.URL.RawQuery
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}
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http.Redirect(w, r, dest, c.code)
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return
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}
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c.h.ServeHTTP(w, r)
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}
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// cleanHost cleans invalid Host headers by stripping anything after '/' or ' '.
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// This is backported from Go 1.5 (in response to issue #11206) and attempts to
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// mitigate malformed Host headers that do not match the format in RFC7230.
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func cleanHost(in string) string {
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if i := strings.IndexAny(in, " /"); i != -1 {
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return in[:i]
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}
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return in
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}
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