zrhoffman commented on code in PR #7392: URL: https://github.com/apache/trafficcontrol/pull/7392#discussion_r1175302294
########## 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 + pemBytes, err := ioutil.ReadFile(path) + if err != nil { + return fmt.Errorf("failed to open cert at %s. err: %w", path, err) + } + pemBlock, _ := pem.Decode(pemBytes) + // Failed to decode PEM, skip file + if pemBlock == nil { + return nil + } + certificate, err := x509.ParseCertificate(pemBlock.Bytes) + if err != nil { + return fmt.Errorf("failed to parse PEM into x509. err: %w", err) + } + + if rootPool == nil { + rootPool = x509.NewCertPool() + } + rootPool.AddCert(certificate) + + return nil + }) + if err != nil { + return fmt.Errorf("failed to load root certs from path %s. err: %w", dirPath, err) + } + + return nil +} + +// ParseClientCertificateUID takes an x509 Certificate and loops through the Names in the +// Subject. If it finds an asn.ObjectIdentifier that matches UID, it returns the +// corresponding value. Otherwise returns empty string. If more than one UID is present, +// the first result found to match is returned (order not guaranteed). +func ParseClientCertificateUID(cert *x509.Certificate) string { + + // Object Identifier value for UID used within LDAP + // LDAP OID reference: https://ldap.com/ldap-oid-reference-guide/ + // 0.9.2342.19200300.100.1.1 uid Attribute Type + // asn1.ObjectIdentifier([]int{0, 9, 2342, 19200300, 100, 1, 1}) + + for _, name := range cert.Subject.Names { + t := name.Type + if len(t) == 7 && t[0] == 0 && t[1] == 9 && t[2] == 2342 && t[3] == 19200300 && t[4] == 100 && t[5] == 1 && t[6] == 1 { + return name.Value.(string) Review Comment: Considering a certificate with multiple UIDs as invalid in d5fc5e3401 -- This is an automated message from the Apache Git Service. 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