mirror of
https://github.com/caddyserver/caddy.git
synced 2024-12-16 21:56:40 -05:00
328 lines
9 KiB
Go
328 lines
9 KiB
Go
// Copyright 2015 Matthew Holt and The Caddy Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package headers
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import (
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"fmt"
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"net/http"
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"regexp"
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"strings"
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"github.com/caddyserver/caddy/v2"
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"github.com/caddyserver/caddy/v2/modules/caddyhttp"
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)
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func init() {
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caddy.RegisterModule(Handler{})
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}
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// Handler is a middleware which modifies request and response headers.
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//
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// Changes to headers are applied immediately, except for the response
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// headers when Deferred is true or when Required is set. In those cases,
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// the changes are applied when the headers are written to the response.
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// Note that deferred changes do not take effect if an error occurs later
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// in the middleware chain.
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//
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// Properties in this module accept placeholders.
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//
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// Response header operations can be conditioned upon response status code
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// and/or other header values.
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type Handler struct {
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Request *HeaderOps `json:"request,omitempty"`
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Response *RespHeaderOps `json:"response,omitempty"`
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}
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// CaddyModule returns the Caddy module information.
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func (Handler) CaddyModule() caddy.ModuleInfo {
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return caddy.ModuleInfo{
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ID: "http.handlers.headers",
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New: func() caddy.Module { return new(Handler) },
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}
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}
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// Provision sets up h's configuration.
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func (h *Handler) Provision(ctx caddy.Context) error {
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if h.Request != nil {
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err := h.Request.Provision(ctx)
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if err != nil {
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return err
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}
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}
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if h.Response != nil {
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err := h.Response.Provision(ctx)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// Validate ensures h's configuration is valid.
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func (h Handler) Validate() error {
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if h.Request != nil {
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err := h.Request.validate()
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if err != nil {
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return err
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}
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}
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if h.Response != nil {
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err := h.Response.validate()
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if err != nil {
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return err
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}
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}
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return nil
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}
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func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
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repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
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if h.Request != nil {
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h.Request.ApplyToRequest(r)
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}
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if h.Response != nil {
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if h.Response.Deferred || h.Response.Require != nil {
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w = &responseWriterWrapper{
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ResponseWriterWrapper: &caddyhttp.ResponseWriterWrapper{ResponseWriter: w},
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replacer: repl,
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require: h.Response.Require,
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headerOps: h.Response.HeaderOps,
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}
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} else {
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h.Response.ApplyTo(w.Header(), repl)
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}
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}
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return next.ServeHTTP(w, r)
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}
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// HeaderOps defines manipulations for HTTP headers.
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type HeaderOps struct {
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// Adds HTTP headers; does not replace any existing header fields.
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Add http.Header `json:"add,omitempty"`
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// Sets HTTP headers; replaces existing header fields.
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Set http.Header `json:"set,omitempty"`
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// Names of HTTP header fields to delete.
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Delete []string `json:"delete,omitempty"`
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// Performs substring replacements of HTTP headers in-situ.
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Replace map[string][]Replacement `json:"replace,omitempty"`
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}
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// Provision sets up the header operations.
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func (ops *HeaderOps) Provision(_ caddy.Context) error {
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for fieldName, replacements := range ops.Replace {
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for i, r := range replacements {
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if r.SearchRegexp != "" {
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re, err := regexp.Compile(r.SearchRegexp)
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if err != nil {
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return fmt.Errorf("replacement %d for header field '%s': %v", i, fieldName, err)
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}
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replacements[i].re = re
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}
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}
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}
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return nil
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}
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func (ops HeaderOps) validate() error {
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for fieldName, replacements := range ops.Replace {
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for _, r := range replacements {
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if r.Search != "" && r.SearchRegexp != "" {
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return fmt.Errorf("cannot specify both a substring search and a regular expression search for field '%s'", fieldName)
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}
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}
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}
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return nil
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}
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// Replacement describes a string replacement,
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// either a simple and fast substring search
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// or a slower but more powerful regex search.
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type Replacement struct {
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// The substring to search for.
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Search string `json:"search,omitempty"`
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// The regular expression to search with.
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SearchRegexp string `json:"search_regexp,omitempty"`
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// The string with which to replace matches.
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Replace string `json:"replace,omitempty"`
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re *regexp.Regexp
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}
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// RespHeaderOps defines manipulations for response headers.
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type RespHeaderOps struct {
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*HeaderOps
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// If set, header operations will be deferred until
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// they are written out and only performed if the
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// response matches these criteria.
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Require *caddyhttp.ResponseMatcher `json:"require,omitempty"`
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// If true, header operations will be deferred until
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// they are written out. Superceded if Require is set.
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// Usually you will need to set this to true if any
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// fields are being deleted.
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Deferred bool `json:"deferred,omitempty"`
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}
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// ApplyTo applies ops to hdr using repl.
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func (ops HeaderOps) ApplyTo(hdr http.Header, repl *caddy.Replacer) {
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// add
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for fieldName, vals := range ops.Add {
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fieldName = repl.ReplaceAll(fieldName, "")
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for _, v := range vals {
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hdr.Add(fieldName, repl.ReplaceAll(v, ""))
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}
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}
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// set
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for fieldName, vals := range ops.Set {
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fieldName = repl.ReplaceAll(fieldName, "")
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var newVals []string
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for i := range vals {
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// append to new slice so we don't overwrite
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// the original values in ops.Set
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newVals = append(newVals, repl.ReplaceAll(vals[i], ""))
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}
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hdr.Set(fieldName, strings.Join(newVals, ","))
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}
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// delete
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for _, fieldName := range ops.Delete {
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hdr.Del(repl.ReplaceAll(fieldName, ""))
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}
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// replace
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for fieldName, replacements := range ops.Replace {
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fieldName = http.CanonicalHeaderKey(repl.ReplaceAll(fieldName, ""))
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// all fields...
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if fieldName == "*" {
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for _, r := range replacements {
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search := repl.ReplaceAll(r.Search, "")
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replace := repl.ReplaceAll(r.Replace, "")
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for fieldName, vals := range hdr {
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for i := range vals {
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if r.re != nil {
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hdr[fieldName][i] = r.re.ReplaceAllString(hdr[fieldName][i], replace)
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} else {
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hdr[fieldName][i] = strings.ReplaceAll(hdr[fieldName][i], search, replace)
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}
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}
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}
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}
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continue
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}
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// ...or only with the named field
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for _, r := range replacements {
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search := repl.ReplaceAll(r.Search, "")
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replace := repl.ReplaceAll(r.Replace, "")
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for hdrFieldName, vals := range hdr {
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// see issue #4330 for why we don't simply use hdr[fieldName]
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if http.CanonicalHeaderKey(hdrFieldName) != fieldName {
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continue
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}
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for i := range vals {
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if r.re != nil {
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hdr[hdrFieldName][i] = r.re.ReplaceAllString(hdr[hdrFieldName][i], replace)
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} else {
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hdr[hdrFieldName][i] = strings.ReplaceAll(hdr[hdrFieldName][i], search, replace)
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}
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}
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}
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}
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}
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}
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// ApplyToRequest applies ops to r, specially handling the Host
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// header which the standard library does not include with the
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// header map with all the others. This method mutates r.Host.
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func (ops HeaderOps) ApplyToRequest(r *http.Request) {
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repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
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// capture the current Host header so we can
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// reset to it when we're done
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origHost, hadHost := r.Header["Host"]
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// append r.Host; this way, we know that our value
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// was last in the list, and if an Add operation
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// appended something else after it, that's probably
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// fine because it's weird to have multiple Host
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// headers anyway and presumably the one they added
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// is the one they wanted
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r.Header["Host"] = append(r.Header["Host"], r.Host)
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// apply header operations
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ops.ApplyTo(r.Header, repl)
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// retrieve the last Host value (likely the one we appended)
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if len(r.Header["Host"]) > 0 {
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r.Host = r.Header["Host"][len(r.Header["Host"])-1]
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} else {
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r.Host = ""
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}
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// reset the Host header slice
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if hadHost {
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r.Header["Host"] = origHost
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} else {
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delete(r.Header, "Host")
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}
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}
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// responseWriterWrapper defers response header
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// operations until WriteHeader is called.
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type responseWriterWrapper struct {
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*caddyhttp.ResponseWriterWrapper
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replacer *caddy.Replacer
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require *caddyhttp.ResponseMatcher
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headerOps *HeaderOps
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wroteHeader bool
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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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if rww.require == nil || rww.require.Match(status, rww.ResponseWriterWrapper.Header()) {
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if rww.headerOps != nil {
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rww.headerOps.ApplyTo(rww.ResponseWriterWrapper.Header(), rww.replacer)
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}
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}
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rww.ResponseWriterWrapper.WriteHeader(status)
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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.ResponseWriterWrapper.Write(d)
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}
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// Interface guards
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var (
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_ caddy.Provisioner = (*Handler)(nil)
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_ caddyhttp.MiddlewareHandler = (*Handler)(nil)
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_ caddyhttp.HTTPInterfaces = (*responseWriterWrapper)(nil)
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)
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