mirror of
https://github.com/gravitational/teleport.git
synced 2026-09-24 16:17:11 +08:00
131 lines
3.2 KiB
Go
131 lines
3.2 KiB
Go
/*
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Copyright 2019-2021 Gravitational, Inc.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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package sshutils
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import (
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"crypto/rsa"
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"net"
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"github.com/gravitational/teleport/api/constants"
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"github.com/gravitational/trace"
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"golang.org/x/crypto/ssh"
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)
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// CertChecker is a drop-in replacement for ssh.CertChecker. In FIPS mode,
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// checks if the certificate (or key) were generated with a supported algorithm.
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type CertChecker struct {
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ssh.CertChecker
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// FIPS means in addition to checking the validity of the key or
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// certificate, also check that FIPS 140-2 algorithms were used.
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FIPS bool
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// OnCheckCert is called when validating host certificate.
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OnCheckCert func(*ssh.Certificate)
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}
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// Authenticate checks the validity of a user certificate.
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func (c *CertChecker) Authenticate(conn ssh.ConnMetadata, key ssh.PublicKey) (*ssh.Permissions, error) {
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err := c.validateFIPS(key)
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if err != nil {
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return nil, trace.Wrap(err)
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}
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perms, err := c.CertChecker.Authenticate(conn, key)
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if err != nil {
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return nil, trace.Wrap(err)
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}
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return perms, nil
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}
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// CheckCert checks certificate metadata and signature.
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func (c *CertChecker) CheckCert(principal string, cert *ssh.Certificate) error {
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err := c.validateFIPS(cert)
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if err != nil {
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return trace.Wrap(err)
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}
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err = c.CertChecker.CheckCert(principal, cert)
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if err != nil {
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return trace.Wrap(err)
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}
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if c.OnCheckCert != nil {
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c.OnCheckCert(cert)
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}
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return nil
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}
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// CheckHostKey checks the validity of a host certificate.
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func (c *CertChecker) CheckHostKey(addr string, remote net.Addr, key ssh.PublicKey) error {
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err := c.validateFIPS(key)
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if err != nil {
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return trace.Wrap(err)
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}
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err = c.CertChecker.CheckHostKey(addr, remote, key)
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if err != nil {
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return trace.Wrap(err)
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}
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if cert, ok := key.(*ssh.Certificate); ok && c.OnCheckCert != nil {
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c.OnCheckCert(cert)
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}
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return nil
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}
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func (c *CertChecker) validateFIPS(key ssh.PublicKey) error {
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// When not in FIPS mode, accept all algorithms and key sizes.
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if !c.FIPS {
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return nil
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}
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switch cert := key.(type) {
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case *ssh.Certificate:
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err := validateFIPSAlgorithm(cert.Key)
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if err != nil {
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return trace.Wrap(err)
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}
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err = validateFIPSAlgorithm(cert.SignatureKey)
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if err != nil {
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return trace.Wrap(err)
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}
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return nil
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default:
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return validateFIPSAlgorithm(key)
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}
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}
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func validateFIPSAlgorithm(key ssh.PublicKey) error {
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cryptoKey, ok := key.(ssh.CryptoPublicKey)
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if !ok {
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return trace.BadParameter("unable to determine underlying public key")
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}
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k, ok := cryptoKey.CryptoPublicKey().(*rsa.PublicKey)
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if !ok {
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return trace.BadParameter("only RSA keys supported")
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}
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if k.N.BitLen() != constants.RSAKeySize {
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return trace.BadParameter("found %v-bit key, only %v-bit supported", k.N.BitLen(), constants.RSAKeySize)
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}
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return nil
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}
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