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116 lines
2.9 KiB
Go
116 lines
2.9 KiB
Go
// Package header provides middleware that appends headers to
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// requests based on a set of configuration rules that define
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// which routes receive which headers.
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package header
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import (
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"net/http"
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"strings"
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"github.com/mholt/caddy/caddyhttp/httpserver"
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)
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// Headers is middleware that adds headers to the responses
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// for requests matching a certain path.
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type Headers struct {
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Next httpserver.Handler
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Rules []Rule
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}
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// ServeHTTP implements the httpserver.Handler interface and serves requests,
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// setting headers on the response according to the configured rules.
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func (h Headers) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
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replacer := httpserver.NewReplacer(r, nil, "")
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rww := &responseWriterWrapper{w: w}
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for _, rule := range h.Rules {
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if httpserver.Path(r.URL.Path).Matches(rule.Path) {
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for _, header := range rule.Headers {
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// One can either delete a header, add multiple values to a header, or simply
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// set a header.
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if strings.HasPrefix(header.Name, "-") {
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rww.delHeader(strings.TrimLeft(header.Name, "-"))
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} else if strings.HasPrefix(header.Name, "+") {
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rww.addHeader(strings.TrimLeft(header.Name, "+"), replacer.Replace(header.Value))
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} else {
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rww.setHeader(header.Name, replacer.Replace(header.Value))
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}
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}
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}
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}
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return h.Next.ServeHTTP(rww, r)
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}
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type (
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// Rule groups a slice of HTTP headers by a URL pattern.
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// TODO: use http.Header type instead?
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Rule struct {
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Path string
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Headers []Header
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}
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// Header represents a single HTTP header, simply a name and value.
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Header struct {
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Name string
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Value string
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}
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)
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// headerOperation represents an operation on the header
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type headerOperation func(http.Header)
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// responseWriterWrapper wraps the real ResponseWriter.
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// It defers header operations until writeHeader
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type responseWriterWrapper struct {
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w http.ResponseWriter
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ops []headerOperation
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wroteHeader bool
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}
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func (rww *responseWriterWrapper) Header() http.Header {
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return rww.w.Header()
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}
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func (rww *responseWriterWrapper) Write(d []byte) (int, error) {
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if !rww.wroteHeader {
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rww.WriteHeader(http.StatusOK)
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}
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return rww.w.Write(d)
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}
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func (rww *responseWriterWrapper) WriteHeader(status int) {
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if rww.wroteHeader {
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return
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}
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rww.wroteHeader = true
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// capture the original headers
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h := rww.Header()
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// perform our revisions
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for _, op := range rww.ops {
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op(h)
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}
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rww.w.WriteHeader(status)
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}
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// addHeader registers a http.Header.Add operation
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func (rww *responseWriterWrapper) addHeader(key, value string) {
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rww.ops = append(rww.ops, func(h http.Header) {
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h.Add(key, value)
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})
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}
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// delHeader registers a http.Header.Del operation
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func (rww *responseWriterWrapper) delHeader(key string) {
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rww.ops = append(rww.ops, func(h http.Header) {
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h.Del(key)
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})
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}
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// setHeader registers a http.Header.Set operation
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func (rww *responseWriterWrapper) setHeader(key, value string) {
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rww.ops = append(rww.ops, func(h http.Header) {
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h.Set(key, value)
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})
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}
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