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caddy/modules/caddyhttp/rewrite/rewrite.go

262 lines
7.7 KiB
Go

// 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"
"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.
//
// The Method and URI properties are "setters": the request URI
// will be set to the given values. Other properties are "modifiers":
// they modify existing files but do not explicitly specify what the
// result will be. It is atypical to combine the use of setters and
// modifiers in a single rewrite.
type Rewrite struct {
// Changes the request's HTTP verb.
Method string `json:"method,omitempty"`
// Changes the request's URI, which consists of path and query string.
// Only components of the URI that are specified will be changed.
// For example, a value of "/foo.html" or "foo.html" will only change
// the path and will preserve any existing query string. Similarly, a
// value of "?a=b" will only change the query string and will not affect
// the path. Both can also be changed: "/foo?a=b" - this sets both the
// path and query string at the same time.
//
// You can also use placeholders. For example, to preserve the existing
// query string, you might use: "?{http.request.uri.query}&a=b". Any
// key-value pairs you add to the query string will not overwrite
// existing values.
//
// To clear the query string, explicitly set an empty one: "?"
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"`
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),
)
}
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 (path, query string, and fragment just because)
if uri := rewr.URI; uri != "" {
// find the bounds of each part of the URI that exist
pathStart, qsStart, fragStart := -1, -1, -1
pathEnd, qsEnd := -1, -1
for i, ch := range uri {
switch {
case ch == '?' && qsStart < 0:
pathEnd, qsStart = i, i+1
case ch == '#' && fragStart < 0:
qsEnd, fragStart = i, i+1
case pathStart < 0 && qsStart < 0 && fragStart < 0:
pathStart = i
}
}
if pathStart >= 0 && pathEnd < 0 {
pathEnd = len(uri)
}
if qsStart >= 0 && qsEnd < 0 {
qsEnd = len(uri)
}
if pathStart >= 0 {
r.URL.Path = repl.ReplaceAll(uri[pathStart:pathEnd], "")
}
if qsStart >= 0 {
r.URL.RawQuery = buildQueryString(uri[qsStart:qsEnd], repl)
}
if fragStart >= 0 {
r.URL.Fragment = repl.ReplaceAll(uri[fragStart:], "")
}
}
// 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
}
// buildQueryString takes an input query string and
// performs replacements on each component, returning
// the resulting query string. This function appends
// duplicate keys rather than replaces.
func buildQueryString(qs string, repl *caddy.Replacer) string {
var sb strings.Builder
// first component must be key, which is the same
// as if we just wrote a value in previous iteration
wroteVal := true
for len(qs) > 0 {
// determine the end of this component, which will be at
// the next equal sign or ampersand, whichever comes first
nextEq, nextAmp := strings.Index(qs, "="), strings.Index(qs, "&")
ampIsNext := nextAmp >= 0 && (nextAmp < nextEq || nextEq < 0)
end := len(qs) // assume no delimiter remains...
if ampIsNext {
end = nextAmp // ...unless ampersand is first...
} else if nextEq >= 0 && (nextEq < nextAmp || nextAmp < 0) {
end = nextEq // ...or unless equal is first.
}
// consume the component and write the result
comp := qs[:end]
comp, _ = repl.ReplaceFunc(comp, func(name, val string) (string, error) {
if name == "http.request.uri.query" && wroteVal {
return val, nil // already escaped
}
return url.QueryEscape(val), nil
})
if end < len(qs) {
end++ // consume delimiter
}
qs = qs[end:]
// if previous iteration wrote a value,
// that means we are writing a key
if wroteVal {
if sb.Len() > 0 {
sb.WriteRune('&')
}
} else {
sb.WriteRune('=')
}
sb.WriteString(comp)
// remember for the next iteration that we just wrote a value,
// which means the next iteration MUST write a key
wroteVal = ampIsNext
}
return sb.String()
}
// 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)