120 lines
4.0 KiB
Go
120 lines
4.0 KiB
Go
// Copyright 2015 Matthew Holt
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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 certmagic
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import (
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"encoding/json"
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"log"
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"net/http"
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"strings"
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"github.com/go-acme/lego/v3/challenge/http01"
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)
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// HTTPChallengeHandler wraps h in a handler that can solve the ACME
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// HTTP challenge. cfg is required, and it must have a certificate
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// cache backed by a functional storage facility, since that is where
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// the challenge state is stored between initiation and solution.
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//
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// If a request is not an ACME HTTP challenge, h will be invoked.
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func (am *ACMEManager) HTTPChallengeHandler(h http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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if am.HandleHTTPChallenge(w, r) {
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return
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}
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h.ServeHTTP(w, r)
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})
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}
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// HandleHTTPChallenge uses am to solve challenge requests from an ACME
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// server that were initiated by this instance or any other instance in
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// this cluster (being, any instances using the same storage am does).
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//
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// If the HTTP challenge is disabled, this function is a no-op.
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//
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// If am is nil or if am does not have a certificate cache backed by
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// usable storage, solving the HTTP challenge will fail.
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//
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// It returns true if it handled the request; if so, the response has
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// already been written. If false is returned, this call was a no-op and
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// the request has not been handled.
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func (am *ACMEManager) HandleHTTPChallenge(w http.ResponseWriter, r *http.Request) bool {
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if am == nil {
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return false
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}
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if am.DisableHTTPChallenge {
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return false
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}
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if !LooksLikeHTTPChallenge(r) {
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return false
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}
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return am.distributedHTTPChallengeSolver(w, r)
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}
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// distributedHTTPChallengeSolver checks to see if this challenge
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// request was initiated by this or another instance which uses the
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// same storage as am does, and attempts to complete the challenge for
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// it. It returns true if the request was handled; false otherwise.
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func (am *ACMEManager) distributedHTTPChallengeSolver(w http.ResponseWriter, r *http.Request) bool {
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if am == nil {
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return false
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}
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host := hostOnly(r.Host)
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tokenKey := distributedSolver{acmeManager: am, caURL: am.CA}.challengeTokensKey(host)
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chalInfoBytes, err := am.config.Storage.Load(tokenKey)
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if err != nil {
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if _, ok := err.(ErrNotExist); !ok {
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log.Printf("[ERROR][%s] Opening distributed HTTP challenge token file: %v", host, err)
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}
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return false
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}
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var chalInfo challengeInfo
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err = json.Unmarshal(chalInfoBytes, &chalInfo)
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if err != nil {
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log.Printf("[ERROR][%s] Decoding challenge token file %s (corrupted?): %v", host, tokenKey, err)
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return false
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}
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return answerHTTPChallenge(w, r, chalInfo)
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}
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// answerHTTPChallenge solves the challenge with chalInfo.
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// Most of this code borrowed from xenolf/lego's built-in HTTP-01
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// challenge solver in March 2018.
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func answerHTTPChallenge(w http.ResponseWriter, r *http.Request, chalInfo challengeInfo) bool {
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challengeReqPath := http01.ChallengePath(chalInfo.Token)
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if r.URL.Path == challengeReqPath &&
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strings.EqualFold(hostOnly(r.Host), chalInfo.Domain) && // mitigate DNS rebinding attacks
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r.Method == "GET" {
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w.Header().Add("Content-Type", "text/plain")
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w.Write([]byte(chalInfo.KeyAuth))
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r.Close = true
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log.Printf("[INFO][%s] Served key authentication (HTTP challenge)", chalInfo.Domain)
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return true
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}
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return false
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}
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// LooksLikeHTTPChallenge returns true if r looks like an ACME
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// HTTP challenge request from an ACME server.
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func LooksLikeHTTPChallenge(r *http.Request) bool {
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return r.Method == "GET" && strings.HasPrefix(r.URL.Path, challengeBasePath)
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}
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const challengeBasePath = "/.well-known/acme-challenge"
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