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// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package rewrite
import (
"net/http"
"net/url"
"strconv"
"strings"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"go.uber.org/zap"
)
func init() {
caddy.RegisterModule(Rewrite{})
}
// Rewrite is a middleware which can rewrite HTTP requests.
//
// These rewrite properties are applied to a request in this order:
// Method, URI, StripPathPrefix, StripPathSuffix, URISubstring.
//
// TODO: This module is still a WIP and may experience breaking changes.
type Rewrite struct {
// Changes the request's HTTP verb.
Method string `json:"method,omitempty"`
// Changes the request's URI (path, query string, and fragment if present).
// Only components of the URI that are specified will be changed.
URI string `json:"uri,omitempty"`
// Strips the given prefix from the beginning of the URI path.
StripPathPrefix string `json:"strip_path_prefix,omitempty"`
// Strips the given suffix from the end of the URI path.
StripPathSuffix string `json:"strip_path_suffix,omitempty"`
// Performs substring replacements on the URI.
URISubstring []replacer `json:"uri_substring,omitempty"`
// If set to a 3xx HTTP status code and if the URI was rewritten (changed),
// the handler will issue a simple HTTP redirect to the new URI using the
// given status code.
HTTPRedirect caddyhttp.WeakString `json:"http_redirect,omitempty"`
logger *zap.Logger
}
// CaddyModule returns the Caddy module information.
func (Rewrite) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "http.handlers.rewrite",
New: func() caddy.Module { return new(Rewrite) },
}
}
// Provision sets up rewr.
func (rewr *Rewrite) Provision(ctx caddy.Context) error {
rewr.logger = ctx.Logger(rewr)
return nil
}
func (rewr Rewrite) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
logger := rewr.logger.With(
zap.Object("request", caddyhttp.LoggableHTTPRequest{Request: r}),
)
changed := rewr.rewrite(r, repl, logger)
if changed {
logger.Debug("rewrote request",
zap.String("method", r.Method),
zap.String("uri", r.RequestURI),
)
if rewr.HTTPRedirect != "" {
statusCode, err := strconv.Atoi(repl.ReplaceAll(rewr.HTTPRedirect.String(), ""))
if err != nil {
return caddyhttp.Error(http.StatusInternalServerError, err)
}
w.Header().Set("Location", r.RequestURI)
w.WriteHeader(statusCode)
return nil
}
}
return next.ServeHTTP(w, r)
}
// rewrite performs the rewrites on r using repl, which
// should have been obtained from r, but is passed in for
// efficiency. It returns true if any changes were made to r.
func (rewr Rewrite) rewrite(r *http.Request, repl *caddy.Replacer, logger *zap.Logger) bool {
oldMethod := r.Method
oldURI := r.RequestURI
// method
if rewr.Method != "" {
r.Method = strings.ToUpper(repl.ReplaceAll(rewr.Method, ""))
}
// uri (which consists of path, query string, and maybe fragment?)
if rewr.URI != "" {
newURI := repl.ReplaceAll(rewr.URI, "")
newU, err := url.Parse(newURI)
if err != nil {
logger.Error("parsing new URI",
zap.String("raw_input", rewr.URI),
zap.String("input", newURI),
zap.Error(err),
)
}
if newU.Path != "" {
r.URL.Path = newU.Path
}
if strings.Contains(newURI, "?") {
// you'll notice we check for existence of a question mark
// instead of RawQuery != "". We do this because if the user
// wants to remove an existing query string, they do that by
// appending "?" to the path: "/foo?" -- in this case, then,
// RawQuery is "" but we still want to set it to that; hence,
// we check for a "?", which always starts a query string
inputQuery := newU.Query()
outputQuery := make(url.Values)
for k := range inputQuery {
// overwrite existing values; we don't simply keep
// appending because it can cause rewrite rules like
// "{path}{query}&a=b" with rehandling enabled to go
// on forever: "/foo.html?a=b&a=b&a=b..."
outputQuery.Set(k, inputQuery.Get(k))
}
// this sorts the keys, oh well
r.URL.RawQuery = outputQuery.Encode()
}
if newU.Fragment != "" {
r.URL.Fragment = newU.Fragment
}
}
// strip path prefix or suffix
if rewr.StripPathPrefix != "" {
prefix := repl.ReplaceAll(rewr.StripPathPrefix, "")
r.URL.Path = strings.TrimPrefix(r.URL.Path, prefix)
}
if rewr.StripPathSuffix != "" {
suffix := repl.ReplaceAll(rewr.StripPathSuffix, "")
r.URL.Path = strings.TrimSuffix(r.URL.Path, suffix)
}
// substring replacements in URI
for _, rep := range rewr.URISubstring {
rep.do(r, repl)
}
// update the encoded copy of the URI
r.RequestURI = r.URL.RequestURI()
// return true if anything changed
return r.Method != oldMethod || r.RequestURI != oldURI
}
// replacer describes a simple and fast substring replacement.
type replacer struct {
// The substring to find. Supports placeholders.
Find string `json:"find,omitempty"`
// The substring to replace. Supports placeholders.
Replace string `json:"replace,omitempty"`
// Maximum number of replacements per string.
// Set to <= 0 for no limit (default).
Limit int `json:"limit,omitempty"`
}
// do performs the replacement on r and returns true if any changes were made.
func (rep replacer) do(r *http.Request, repl *caddy.Replacer) bool {
if rep.Find == "" || rep.Replace == "" {
return false
}
lim := rep.Limit
if lim == 0 {
lim = -1
}
find := repl.ReplaceAll(rep.Find, "")
replace := repl.ReplaceAll(rep.Replace, "")
oldPath := r.URL.Path
oldQuery := r.URL.RawQuery
r.URL.Path = strings.Replace(oldPath, find, replace, lim)
r.URL.RawQuery = strings.Replace(oldQuery, find, replace, lim)
return r.URL.Path != oldPath && r.URL.RawQuery != oldQuery
}
// Interface guard
var _ caddyhttp.MiddlewareHandler = (*Rewrite)(nil)
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