alficles commented on code in PR #7392: URL: https://github.com/apache/trafficcontrol/pull/7392#discussion_r1132779925
########## traffic_ops/traffic_ops_golang/auth/certificate.go: ########## @@ -0,0 +1,167 @@ +package auth + +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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. + */ + +import ( + "crypto/x509" + "encoding/pem" + "fmt" + "io/fs" + "io/ioutil" + "net/http" + "path/filepath" +) + +// ParseCertificate takes a http.Request, pulls the (optionally) provided client TLS +// certificates and attempts to verify them against the directory of provided Root CA +// certificates. The Root CA certificates can be different than those utilized by the +// http.Server. Returns an error if the verification process fails +func VerifyClientCertificate(r *http.Request, rootCertsDirPath string) error { + // TODO: Parse client headers as alternative to TLS in the request + + if err := loadRootCerts(rootCertsDirPath); err != nil { + return fmt.Errorf("failed to load root certificates") + } + + if err := verifyClientRootChain(r.TLS.PeerCertificates); err != nil { + return fmt.Errorf("failed to verify client to root certificate chain") + } + + return nil +} + +func verifyClientRootChain(clientChain []*x509.Certificate) error { + if len(clientChain) == 0 { + return fmt.Errorf("empty client chain") + } + + if rootPool == nil { + return fmt.Errorf("uninitialized root cert pool") + } + + intermediateCertPool := x509.NewCertPool() + for _, intermediate := range clientChain[1:] { + intermediateCertPool.AddCert(intermediate) + } + + opts := x509.VerifyOptions{ + Intermediates: intermediateCertPool, + Roots: rootPool, + KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth}, + } + _, err := clientChain[0].Verify(opts) + if err != nil { + return fmt.Errorf("failed to verify client cert chain. err: %w", err) + } + return nil +} + +// Lazy initialized +var rootPool *x509.CertPool + +func loadRootCerts(dirPath string) error { + // Root cert pool already populated + // TODO: This will prevent rolling cert renewals at runtime and will require a TO restart + // to pick up additional certificates. + if rootPool != nil { + return nil + } + + if dirPath == "" { + return fmt.Errorf("empty path supplied for root cert directory") + } + + err := filepath.WalkDir(dirPath, + // walk function to perform on each file in the supplied + // directory path for root certificiates. + // + // For each file in the directory, first check if it, too, is a dir. If so, + // return the filepath.SkipDir error to allow for it to be skipped without + // stopping the subsequent executions. + // + // If of type File, then load the PEM encoded string from the file and + // attempt to decode the PEM block into an x509 certificate. If successful, + // add that certificate to the Root Cert Pool to be used for verification. + // + // Must be a closure for access to the `dirPath` value + func(path string, file fs.DirEntry, e error) error { + if e != nil { + return e + } + + // Skip logic if root directory + if path == dirPath { + return nil + } + + // Don't traverse nested directories + if file.IsDir() { + return filepath.SkipDir + } + + // Read file Review Comment: The model I'm thinking of is the one SSH uses. Basically, if someone that isn't the owner of the process (or root, ofc) can write to the file, it shouldn't be trusted. Technically, it would also be acceptable to accept group write if the only one in the group is the owner of the process, but that's more complex. Practically... folks will see the error and `chmod 600` the file and be done with it. And that's fine, too. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
