125 lines
4.7 KiB
Go
125 lines
4.7 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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"net/http"
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"strings"
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"github.com/mholt/acmez/acme"
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"go.uber.org/zap"
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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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chalInfo, distributed, err := am.config.getChallengeInfo(host)
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if err != nil {
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if am.Logger != nil {
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am.Logger.Error("looking up info for HTTP challenge",
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zap.String("host", host),
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zap.Error(err))
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}
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return false
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}
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return solveHTTPChallenge(am.Logger, w, r, chalInfo.Challenge, distributed)
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}
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// solveHTTPChallenge solves the HTTP challenge using the given challenge information.
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// If the challenge is being solved in a distributed fahsion, set distributed to true for logging purposes.
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// It returns true the properties of the request check out in relation to the HTTP challenge.
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// Most of this code borrowed from xenolf's built-in HTTP-01 challenge solver in March 2018.
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func solveHTTPChallenge(logger *zap.Logger, w http.ResponseWriter, r *http.Request, challenge acme.Challenge, distributed bool) bool {
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challengeReqPath := challenge.HTTP01ResourcePath()
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if r.URL.Path == challengeReqPath &&
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strings.EqualFold(hostOnly(r.Host), challenge.Identifier.Value) && // 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(challenge.KeyAuthorization))
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r.Close = true
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if logger != nil {
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logger.Info("served key authentication",
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zap.String("identifier", challenge.Identifier.Value),
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zap.String("challenge", "http-01"),
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zap.String("remote", r.RemoteAddr),
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zap.Bool("distributed", distributed))
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}
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return true
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}
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return false
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}
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// SolveHTTPChallenge solves the HTTP challenge. It should be used only on HTTP requests that are
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// from ACME servers trying to validate an identifier (i.e. LooksLikeHTTPChallenge() == true). It
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// returns true if the request criteria check out and it answered with key authentication, in which
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// case no further handling of the request is necessary.
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func SolveHTTPChallenge(logger *zap.Logger, w http.ResponseWriter, r *http.Request, challenge acme.Challenge) bool {
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return solveHTTPChallenge(logger, w, r, challenge, 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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